;  i 


MEMCAL    SCHOOL 


l     f 


COLLEGE  OF  PHARMACY 


•' 


A  MANUAL 


OF 


ELEMENTARY  CHEMISTRY, 

THEORETICAL  AND  PRACTICAL. 


GEORGE  FOWNES,  F  R.S., 

LATE  PROFESSOR  OF  PRACTICAL  CHEMISTRY   IN   UNIVERSITY  COLLEGE,   LONDON 
FROM    THE 

TENTH  REVISED  AND   CORRECTED   ENGLISH  EDITION. 

EDITED    BY 

ROBERT  BRIDGES,  M.D., 

PROFESSOR  OF  CHEMISTRY  IN  THE  PHILADELPHIA  COLLEGE  OF  PHARMACY. 

0  3!?2£D  of  Pharmacy 

WITH 
ONE  HUNDRED  AND  NINETY-SEVEN  ILLUSTRATIONS. 


PHILADELPHIA: 
HENRY    C.    LEA. 

1869. 


Entered  according  to  Act  of  Congress,  in  the  year  1869,  by 
HENRY   C.   LEA, 

In  the  Clerk's  Office  of  the  District  Court  of  the  United  States,  in  and  for  the 
Eastern  District  of  Pennsylvania. 


AMERICAN    PUBLISHER'S 
ADVERTISEMENT. 


SO  recent  and  so  thorough  has  been  the  revision  which  this  work 
has  enjoyed  at  the  hands  of  the  English  Editors,  that  but 
little  has  remained  to  be  done  in  preparing  the  present  reprint ; 
while  the  enlargement  which  the  volume  has  necessarily  under- 
gone, in  the  introduction  of  the  most  modern  views  and  discov- 
eries, has  rendered  it  advisable  to  confine  the  additions  to  as 
moderate  a  compass  as  possible.  The  American  Editor  has  there- 
fore added  but  few  notes,  together  with  a  number  of  illustrations, 
and  has  directed  his  attention  rather  to  secure  the  accuracy  so 
essential  to  a  treatise  of  this  nature.  Especial  care  has  been 
devoted  to  the  formulae,  and  errors  have  been  corrected  wherever 
a  minute  supervision  has  been  able  to  detect  them. 

In  its  present  enlarged  and  improved  form,  it  is  hoped  that 
the  work  fairly  represents  the  existing  condition  of  the  science, 
and  that  it  may  be  found  worthy  a  continuance  of  the  very 
remarkable  favor  which  it  has  so  long  enjoyed. 


PHILADELPHIA,  May,  1869. 


418. 


ADVERTISEMENT 

TO 

THE    TENTH    EDITION. 


THE  rapid  progress  of  chemical  discovery  during  the  last  few  years 
has  rendered  it  necessary  to  make  considerable  alterations  and 
additions  in  almost  every  part  of  the  present  Edition. 

The  chapter  on  the  General  Principles  of  Chemical  Philosophy  has 
been  re-written. 

Some  considerable  additions  have  been  made  to  the  descriptions  of 
the  metals,  especially  those  of  rarer  occurrence,  several  of  which  have 
acquired  greatly  increased  importance  by  the  more  exact  investigations 
of  late  years.  The  distinguishing  reactions  of  the  several  metals  are 
also  given  more  fully  than  in  former  editions. 

The  greater  part  of  the  Organic  Chemistry  has  been  re-written,  espe- 
cially the  sections  relating  to  the  Hydrocarbons,  Alcohols,  and  Acids, 
upon  which  great  light  has  been  thrown  by  recent  investigations. 

The  section  on  Animal  Chemistry  has  been  entirely  revised. 

The  Atomic  Weights  used  in  this  Edition  are  those  which  are  now 
almost  universally  received  among  Chemists,  and  the  Notation  has 
been  altered  in  accordance  with  them. 

The  Nomenclature  has  been  simplified  by  discarding  the  word  "  of  " 
in  the  names  of  salts,  &c.,  using,  for  example,  the  term  "silver  nitrate" 
instead  of  "  nitrate  of  silver." 

The  Weights  and  Measures  used  are  those  of  the  French  decimal 
system ;  and  Temperatures  are  expressed  on  the  Centigrade  scale,  ex- 
cepting where  the  contrary  is  expressly  stated.  A  comparative  Table 
of  the  two  scales  is  given  at  the  end  of  the  volume. 

H.  BENCE  JONES. 
HENRY  WATTS. 

LONDON,  October,  1868. 


ADVERTISEMENT 

TO 

THE    THIED    EDITION. 


THE  correction  of  this  Edition  for  the  Press  was  the  daily 
occupation  of  Professor  Fownes,  until  a  few  hours  pre- 
vious to  his  death  in  January,  1849. 

His  wish  and  his  endeavor,  as  seen  in  his  manuscript,  were  to 
render  it  as  perfect  and  as  minutely  accurate  as  possible. 

When  he  had  finished  the  most  important  part  of  the  Organic 
Chemistry,  where  the  most  additions  were  required,  he  told  me 
he  should  "  do  no  more,"  —  he  had  "  finished  his  work." 

At  his  request  I  have  corrected  the  Press  throughout,  and  made 
a  few  alterations  that  .appeared  desirable  in  the  only  part  which 
he  had  left  unaltered,  the  Animal  Chemistry. 

The  Index  and  the  Press  have  also  been  corrected  throughout 
by  his  friend  Mr.  Robert  Murray. 

H.  BENCE  JONES,  M.D. 

30  GROSVENOR  STREET,  Jan.,  1850. 

vi 


PREFACE 

TO 

THE    FIRST    EDITION. 


design  of  the  present  volume  is  to  offer  to  the  student 
commencing  the  subject  of  Chemistry,  in  a  compact  and 
inexpensive  form,  an  outline  of  the  general  principles  of  that 
science,  and  a  history  of  the  more  important  among  the  very 
numerous  bodies  which  Chemical  Investigations  have  made  known 
to  us.  The  work  has  no  pretensions  to  be  considered  a  complete 
treatise  on  the  subject,  but  is  intended  to  serve  as  an  introduction 
to  the  larger  and  more  comprehensive  systematic  works  in  our 
own  language  and  in  those  of  the  Continent ;  and  especially  to 
prepare  the  student  for  the  perusal  of  original  memoirs,  which,  in 
conjunction  with  practical  instruction  in  the  laboratory,  can  alone 
afford  a  real  acquaintance  with  the  spirit  of  research  and  the 
resources  of  Chemical  Science. 

It  has  been  my  aim  throughout  to  render  the  book  as  practical 
as  possible,  by  detailing,  at  as  great  length  as  the  general  plan 
permitted,  many  of  the  working  processes  of  the  scientific  labora- 
tory, and  by  exhibiting,  by  the  aid  of  numerous  wood-engrav- 
ings, the  most  useful  forms  of  apparatus,  with  their  adjustments 
and  methods  of  use. 

As  one  principal  object  was  the  production  of  a  convenient  and 
useful  class-book  for  pupils  attending  my  own  lectures,  I  have 
been  induced  to  adopt  in  the  book  the  plan  of  arrangement  fol- 
lowed in  the  lectures  themselves,  and  to  describe  the  non-metallic 

vii 


viii  PKEFACE. 

elements  and  some  of  their  most  important  compounds  before 
discussing  the  subject  of  the  general  philosophy  of  Chemical 
Science,  and  even  before  describing  the  principle  of  the  equiva- 
lent quantities,  or  explaining  the  use  of  the  written  symbolical 
language  now  universal  among  Chemists.  For  the  benefit  of 
those  to  whom  these  matters  are  already  familiar,  and  to  render 
the  history  of  the  compound  bodies  described  in  the  earlier  part 
of  the  work  more  complete,  I  have  added  in  foot-notes  the  view 
adopted  of  their  Chemical  Constitution,  expressed  in  symbols. 

I  have  devoted  as  much  space  as  could  be  afforded  to  the  very 
important  subject  of  Organic  Chemistry ;  and  it  will,  I  believe, 
be  found  that  there  are  but  few  substances  of  any  general  interest 
which  have  been  altogether  omitted,  although  the  very  great 
number  of  bodies  to  be  described  in  a  limited  number  of  pages 
rendered  it  necessary  to  use  as  much  brevity  as  possible. 

GEO.  FOWNES. 

UNIVERSITY  COLLEGE,  LONDON. 
October  5,  1847. 


CONTENTS. 


PAGE 

INTRODUCTION     ........  25 

PART    I. 

PHYSICS. 

OF  DENSITY  AND  SPECIFIC  GRAVITY      .....  27 

Methods  of  determining  the  Specific  Gravities  of  Fluids  and  Solids  27 

Construction  and  Application  of  the  Hydrometer      .  32 

OF  THE  PHYSICAL  CONSTITUTION  OF  THE  ATMOSPHERE,  AND  OF  GASES 

IN  GENERAL           .......  35 

Elasticity  of  Gases;   Construction  and  Use  of  the  Air-pump          .  36 
Weight  and  Pressure  of  the  Air  —  Barometer        ...  38 
Law  of  Mariotte :  Relations  of  Density  and  Elastic  force:  Cor- 
rection of  Volumes  of  Gases  for  Pressure                .             .  39 

HEAT    .........  42 

Expansion  —  Thermometers        .             .             .             .             .  42 

Different    Rates   of  Expansion    among    Metals.      Compensation- 
pendulum               .......  45 

Daniell's  Pyrometer        ......  47 

Expansion  of  Liquids  —  Absolute  Expansion  of  Mercury  —  Maxi- 
mum Density  of  Water            .....  48 

Expansion  of  Gases  —  Ventilation  —  Movements  of  the  Atmos- 
phere        ........  51 

Conduction  of  Heat         ......  54 

Change  of  State  —  Latent  Heat       .....  55 

Ebullition  —  Steam          ......  57 

Distillation    .             .......  61 

Evaporation  at  low  temperatures            ....  62 

Tension  of  Vapors  at  different  temperatures          ...  63 

Vapor  of  Water  in  the  Atmosphere  —  Hygrometry      .             .  65 

Liquefaction  of  Permanent  Gases                ....  66 

Production  of  Cold  by  Evaporation       ....  68 

Capacity  for  Heat  —  Specific  Heat               ....  69 

Relations  between  the  Specific  Heat  and  Atomic  Weight  of  Ele- 
mentary Bodies            ......  72 

Sources  of  Heat       .......  74 

Relation   between    Heat   and    Mechanical    Force  —  Mechanical 

Equivalent  of  Heat     ......  75 

Dynamical  Theory  of  Heat              .....  77 

ix 


X  CONTENTS. 

PAGE 

LIGHT         ..... 

Reflection,  Refraction,  and  Polarization  of  Light  .  .  83 

Dispersion  —  Relation  between  Color  and  Refrangibility —  Solar 

Spectrum  —  Spectral  Analysis  .  85 

Double   Refraction   and  Polarization  —  Circular   Polarization  — 

Soleil's  Saccharimeter      ......  91 

Heating  and  Chemical  Rays  of  the  Spectrum  —  Photography 

Radiation,  Reflection,  Absorption,  and  Transmission  of  Heat       .  99 

MAGNETISM  .......  107 

Magnetic  Polarity  —  Natural  and  Artificial  Magnets          .  .         107 

Terrestrial  Magnetism  .....  109 

ELECTRICITY     .  .  .    *  .  .  .  114 

Electrical  Excitation  —  Polarity  —  Induction  —  Charge  and  Dis- 
charge .  .  .  .  .  '  . 

Electrical  Machines  ......         116 

Accumulation  of  Electricity  —  Leyden  jar 

Electrophorus  .......         119 

Electric  Current  —  Development  of  Electricity  by  Chemical  Ac- 
tion —  Voltaic  Battery  .  .  .  119 
Thermo-electricity         ......         121 

Animal  Electricity  ......  122 

Electro-magnetism  —  Galvanoscopes  and  Galvanometers  —  Induc- 
tion of  Magnetism  by  Electricity,  and  of  Electricity  by  Mag- 
netism ........  122 

Electricity  of  Vapor       ......  126 


PART    II. 

CHEMISTRY  OF  ELEMENTARY  BODIES. 

Nonmetallic  Elements  ......         127 

Oxygen     ........  128 

Collection  and  Preservation  of  Gases  —  Pneumatic  Trough  — 

Gas-holder  .......  129 

Oxides  —  Acid,  Basic,  and  Neutral  Oxides  —  Salts — Chemical 

Nomenclature  ......  132 

Ozone         ........         135 

Hydrogen  .  .  .  .  .  .  .  136 

Diffusion,  Effusion,  Transpiration,  and  Occlusion  of  Gases          .         137 

Combination  of  Oxygen  and  Hydrogen — Oxy-hydrogen  Blow- 
pipe—  Slow  Combustion  of  Hydrogen  —  Surface  action  of 
Platinum  .......  140 

Water  —  Its  Composition  by  Weight  and  Volume  —  Natural 
Water  —  Sea,  River,  and  Spring  Water  —  Water  of  Hydra- 
tion  —  Water  of  Crystallization — Solubility  of  Salts  .  143 

Liquid  Diffusion  —  Dialysis  —  Osmose  —  Absorption  of  Gases 

by  Water  ........  148 

Hydrogen  Dioxide  .  .  .  ...  .         153 


CONTENTS.  XI 

PAGE 

Nitrogen                .             .             .             .             .             .             .  153 

Atmospheric  air  —  Eudiometry    .                           ...  154 

Oxides  and  Oxygen-acids  of  Nitrogen             .             .             .  157 

Nitrogen  and  Hydrogen  —  Ammonia  —  Ammoniacal  salts           .  162 

Carbon    ........  163 

Compounds  of  Carbon  and  Oxygen  —  Carbonates  .  .  165 
Compounds  of  Carbon  and  Hydrogen — Methane,  or  Marsh-gas 

—  Ethene,  or  Olefiant  gas  —  Coal  and  Oil  Gases  .  .  169 
Combustion  and  the  structure  of  Flame  —  Furnaces  —  Lamps  — 

Blowpipe             ...                                •    .  172 

Chlorine   ........  179 

Hydrochloric  acid  .  .  .  .  .  .181 

Oxides  and  Oxacids  of  Chlorine         ....  183 

Chlorine  and  Nitrogen  —  Chlorine  and  Carbon                .             .  187 

Bromine   ........  188 

Iodine             ........  188 

Fluorine                .             .             .             .             .             .             .  192 

Sulphur          .  .  .  .  .  .  .  .193 

Oxides  and  Oxacids  of  Sulphur          ....  194 

Compounds  of  Sulphur  and  Hydrogen    ....  200 

Compounds  of  Sulphur  and  Carbon  ....  202 

Compounds  of  Sulphur  with  Chlorine,  Bromine,  and  Iodine      .  203 

Selenium  ........  204 

Tellurium      .  .  .  .  .  -.  .  .205 

Boron       ........  208 

Boric  Oxide  and  Acid       ......  208 

Boron  Nitride               ......  208 

"      Chloride  and  Bromide       .                          .             .             .  209 

Silicium  or  Silicon             ......  209 

Silica  or  Silicic  Oxide  —  Silicates             ....  210 

•    Silicium  Hydride  —  Compounds  of  Silicium  with  Chlorine  and 

Bromine       .             .             .             .             .             .             .  211 

Phosphorus    .  .  .  .  .  .  .  .212 

Oxides  and  Oxacids  of  Phosphorus    ....  213 

Compounds  of  Phosphorus  and  Hydrogen  .  .  .  215 
Compounds  of  Phosphorus  with  Chlorine,  Bromine,  Iodine, 

Sulphur,  and  Selenium        ....  216 


ON  THE  GENERAL  PRINCIPLES  OP  CHEMICAL  PHILOSOPHY. 

The  Laws  of  Combination  by  Weight.  —  1.  Constancy  of  Compo- 
sition.—2.  Law  of  Multiples.  —  3.  Law  of  Equivalents            .  219 
Monogenic  and  Polygenic  Elements       ....  221 
Atomic  Weights  —  Atoms  and  Equivalents  —  Substitution  222 


xii  CONTENTS. 


Symbolic  Notation           ......  225 

Table   of   Elementary  Bodies    with   their   Symbols  and   Atomic 

Weights    ........  226 

Physical  and  Chemical  Relations  of  Atomic  Weights                 .  227 

Laws  of  Combination  by  Volume    .....  228 

The  Atomic  Theory         ......  229 

Equivalent  or  Saturating  power  of  Elementary  Bodies  —  Ar- 

tiads  and  Perissads  —  Monads  —  Dyads,  &c.                .             .  230 

Constitutional  Formulae               .....  231 

Combination  of  Similar  Atoms         .....  232 

Variation  of  Equivalency           .....  233 

Classification  of  Elementary  Bodies  according  to  their  Equi- 
valent power  or  Atomicity        .....  236 

Compound  Radicals  or  Residues         ....  237 
Chemical  Affinity     .             .                           .             .             .             .239 

Relations  of  Heat  to  Chemical  Affinity          ...  241 

ELECTRO-CHEMICAL  DECOMPOSITION  OR  ELECTROLYSIS  ;   CHEMISTRY 

OF  THE  VOLTAIC  PILE       ......  245 

Definite  amount  of  Electrolytic  Decomposition  —  Voltameter  .  248 
Division  of  Bodies  into  Electro-positive,  Basylous,  or  Ziricous  and 

Electro-negative,  Acid  or  Chlorous          ....  251 

Voltaic  Batteries              ......  252 

Heat  developed  by  the  Electric  Current     ....  255 

Crystallization  —  Crystalline  Form        ....  257 

Systems  of  Crystallography         .....  260 

Isomorphism   .......  264 


Chemistry  of  the  Metals          .  ....  267 

Physical  Properties  of  Metals  .....  267 

Chemical  Relations:  Alloys  .....  270 

Compounds  of  Metals  with  Metalloids  —  Classification  of  Metals  271 

Metallic  Chlorides  ......  273 

Bromides    .......  275 

Iodides  ......  276 

Fluorides    .......  276 

Cyanides  ......  277 

Oxides        .......  278 

Oxygen-salts  or  Oxysalts          ....  280 

Basicity  of  Acids  —  Normal,  Acid  and  Double  Salts  282 
Phosphates  —  Orthophosphates,  Metaphosphates,  and 

Pyrophosphates          .....  285 

"         Sulphides          ......  287 

"        Selenides  and  Tellurides  289 


CLASS  I.  —  MONAD  METALS. 

Potassium  ........  290 

Sodium              .             .             .             .             .             .             .  .299 

Alkalimetry         .             .             .             .             .             .             .  303 

Ammonium       ........          310 

Ammoniacal  Salts            ......  311 

Amic  Acids  and  Amides       .  .         314 


CONTENTS.  Xlll 

PAGE 

Lithium       ........  316 

Ccesium  and  Rubidium  ......         316 

Silver          ........  317 

CLASS  II. — DYAD  METALS. 

Group  L  —  Metals  of  the  Alkaline  Earths  ....  323 

Barium,  323  —  Strontium,  325  —  Calcium,  326. 

Group  II.  —  Metals  of  the  Earths         .....         332 
Aluminium  (tetrad?),   333  —  Beryllium,  or  Glucinum  (tetrad?), 
337  — Zirconium    (tetrad),  338  —  Thorinum,  or  Thorium,  339. 
Cerium,   Lanthanum,    and   Didymium,  340  —  Yttrium  and  Er- 
bium, 342. 

Reactions  of  the  Earth-metals         .....         343 
Manufacture  of  Glass,  Porcelain,  and  Earthenware     .  .  344 

Group  III.  —  Magnesium,  347  —  Zinc,  351 — Cadmium         .  .         352 

Group  IV. — Copper,  353  —  Mercury,  357  —  Ammoniacal  Mercury- 
compounds  .  .....  362 

CLASS  III.  —  TRIAD  METALS. 
Thallium  ........         365 

Gold  ........  369 

CLASS  IV.  —  TETRAD  METALS. 
Group  I.  —  Platinum  Metals      ......         372 

Platinum,  372  —  Ammoniacal  Platinum  compounds,  374  —  Palla- 
dium, 378 —  Rhodium,  380  —  Iridium,  382  —  Ruthenium,  385. 
Osmium,  387. 

Group  II.  —  Tin,  389 — Titanium  ....  393 

Group  III.  —  Lead        .......         344 

Group  IV.  —  Iron  Metals    .  .  .  .  .  .  397 

Iron,  397  — Nickel,  405  — Cobalt,  407  —  Manganese,  410  — Ura- 
nium, 414 —  Indium,  416. 

CLASS  V. — PENTAD  METALS. 

Antimony,   418  — Arsenic,   422  — Bismuth,   427  —  Vanadium,  429. 
Tantalum,  432  —  Niobium  or  Columbium,  434. 

CLASS  VI.  — HEXAD  METALS. 
Chromium,  437  —  Tungsten  or  Wolfram,  441  —  Molybdenum  .         444 


PART   III. 

ORGANIC  CHEMISTRY. 

INTRODUCTION         .......  447 

THE  ELEMENTARY  OR  ULTIMATE  ANALYSIS  OF  ORGANIC  COMPOUNDS  .  448 

Empirical  and  Molecular  Formulae        .  457 


XIV  CONTENTS. 

PAGE 

DETERMINATION  OF  THE  DENSITY  OF  VAPORS               .            .            .  459 

DECOMPOSITION  AND  TRANSFORMATION  OF  ORGANIC  COMPOUNDS    .  462 

CLASSIFICATION  OF  ORGANIC  COMPOUNDS — ORGANIC  SERIES              .  466 

Rational  Formulae  of  Organic  Compounds  —  Isomerism             .  472 
HYDROCARBONS : 

First  Series,  CnH2n_2  —  Paraffins       .                          ...  474 

Second  Series,  CnH2n  —  Olefines  .             ....  480 

Third  Series,  CnH2n_2: 
Ethine  or  Acetyline  —  Propine  or  Allylene  —  Quavtine  or  Cro- 

tonylene  —  Quintine  or  Valerylene  —  Sextine  or  Diallyl         .  484 

Fourth  Series,  CnH2n_4 : 

Quintone  or  Valylene  ......  488 

Terpenes,  C10H,6 —  Turpentine  oil  —  Volatile  oils  isomeric  with 
Turpentine  oil  —  Caoutchouc  —  Gutta-percha  —  Volatile  oils 

in  general           .......  488 

Fifth  Series,  CnH2n_6  —  Aromatic  Hydrocarbons     .             .             .  492 

Benzene  or  Benzol             ......  493 

Toluene  or  Methyl-benzene     .....  495 

Xylene  or  Dimethyl-benzene         .....  497 

Ethyl-benzene               ......  498 

Isomeric  Hydrocarbons,  C9H,2  —  Cumene  —  Mesitylene 

Isomeric  Hydrocarbons,  C10H14  —  Cymene     .             .             .  499 

Amyl-benzene,  CnH16        .  .  .  .  .500 

Sixth  Series,  CnH2n_8  —  Phenylene  —  Cinnamene           .             .  500 
Seventh  Series,  CnH2n_,0—  Cholesterin          .             .             .             .502 

Eighth  Series,  CnH2n_12—  Naphthalene  .             ...  502 

Ninth  Series,  CnH2n_14  — Diphenyl  — Dibenzyl         .  .  .503 

Tenth  Series,  CnH2n_,6  —  Stilbene            ....  604 

Eleventh  Series,   CnH2n_18. — Anthracene,   or  Paranaphthalene  — 

Pyrene  — Retene          .             .             .             .             .             .  504 

Twelfth  Series,  CnH2n_24.  —  Chrysene           ....  505 

Appendix  to  Hydrocarbons:  Coal,  Petroleum,  Naphtha,  and  allied 

substances        .......  505 

ALCOHOLS  AND  ETHERS            ,            .            .            .            .            .  508 

Monatomic  Alcohols  and  Ethers  .             .             .             .             .  510 

1.  —  Containing  the  Radicals  CnH2n+l,  homologous  with  Methyl     .  510 

Methyl  alcohol  and  ethers  ,             ,             ,             .             .  512 
Ethyl  alcohol  and  ethers           .             ,             .             .             -515 

Commercial  Spirit  —  Wine  —  Beer — Vinous  Fermentation 
Ethyl  Chloride  or  Chlorethane.  ,  ,  ,  .522 

Ethyl  Bromide  and  Iodide  .  522 

Ethyl  Oxide  or  Ethylic  Ether  523 


CONTENTS.  XV 


Ethyl  Nitrate            ......  526 

Ethyl  Sulphates    .  .  .  .  .  .526 

Ethyl  Sulphites         ......  527 

Ethyl  Phosphates  and  Borates  .  .  .  .528 

Ethyl  Silicates          ......  529 

Ethyl  Sulph-hydrate  or  Mercaptan     ....  529 

Ethyl  Sulphides        ......  530 

Triethylsulphurous  compounds  .....  530 

Propyl  alcohols  and  ethers     ...             .             .  531 

Quartyl  or  Butyl  alcohols  and  ethers  ....  532 

Quintyl  or  Amyl  alcohols  and  ethers           .             .             .  535 

Sextyl  or  Hexyl  alcohols  and  ethers    .             .             .             .  539 

Septyl  or  Heptyl  alcohols  and  ethers          .             .             .  540 

Octyl  alcohols  and  ethers          .             .             .             .  541 

Nonyl  alcohol  —  Sexdecyl  or  Cetyl  alcohol             .             .  542 

Ceryl  alcohol  —  Melissyl  alcohol          ....  542 

2.  —  Monatomic  Alcohols,  CnH2nO. 

Vinyl  alcohol  —  Allyl  alcohol          ....  543 

3.  —  Monatomic  Alcohols,  OH2n_20. 

Camphol     .  .  .  .  .  .  .546 

4. — Monatomic  Alcohols,  CnH2n_gO. — Aromatic  Alcohols       .  547 

Primary  Aromatic  Alcohols      .....  548 

Benzyl  alcohol       ......  518 

Xylyl  alcohol  —  Cymyl  alcohol  —  Sycoceryl  alcohol  .         .  549 

Secondary  Aromatic  Alcohols  ;  Phenols    .             .             .  550 
Phenol,  C6H60 — Methyl  phenate  or  Anisol — Chlorophenols 

—  Nitrophenols    ..                      ...             7  550 

Cresol,  C7H80  —  Eight-carbon  or  Xylylic  phenols  .              .  553 

Ten-carbon  Phenols  —  Thymol    ....  556 

5. — Monatomic  Alcohols,  CnH2n_80  .         ....  554 

Cinnyl  alcohol  —  Cholesterin       ....  654 

Diatomic  Alcohols  and  Ethers  ......  555 

1.  —  Diatomic  Alcohols,  CnH2n+202.  —  Glycols            .             .  555 

Ethene  alcohol  or  Glycol,  C2H602  .  .  .  .  .556 

Ethene  Chloride  .             .  558 
Products  of  the  action  of  Chlorine  on  Ethene  Chloride  — 

Chlorides  of  Carbon          .....  559 

Ethene  Bromide  and  Iodide         ....  560 

Oxygen-ethers  of  the  Glycols  —  Ethene  Oxide         .             .  560 

Polyethenic  Alcohols        .....  561 

2.  Diatomic  Phenols           ......  562 

Oxyphenol,  Oxyphenic  acid,  or  Pyrocatechin  —  Orcin  .  562 

Guaiacol  and  Creosol  —  Creosote      ....  563 

Veratrol  —  Anisic  Alcohol           ....  564 

Triatomic  Alcohols  and  Ethers          .....  565 

Methenyl  Ethers —  Methenyl  Chloride  or  Chloroform  —  Bromo- 

form  —  lodoform      ......  565 

Propenyl  Alcohol  or  Glycerin,  C3H803     .  .  .  .666 


XVI  CONTENTS. 

PAGE 

Polyglycerins  .......  569 

Quintenyl  Alcohol,  or  Amyl-glycerin   ....  569 

Triatomic   Phenols  —  Pyrogallol  or  Pyrogallic  acid  —  Phloro- 

glucin — Frangulin          .....  570 

Tetratomic  Alcohols  and  Ethers  .  .  .  .  .571 

Erythrite  —  Propylphycite  .....  571 

Pentatomic  Alcohols.             ......  572 

Pinite  and  Quercite  ......  572 

Hexatomic  Alcohols  and  Ethers        .....  572 

Saturated  Hexatomic  Alcohols- — Mannite  —  Dulcite              .  572 

Glucoses    ........  574 

Ordinary  Glucose — Dextroglucose —  Dextrose     .             .  575 

Maltose  —  Levulose  —  Mannitose         ....  577 

Galactose  —  Inosite  or  Phaseomannite  —  Sorbin,  or  Sorbite — 

Eucalyn    .......  578 

Glucosides             .......  578 

Aesculin  —  Amygdalin  —  Chitin  —  Gallotannic    acid  —  Gly cyr- 
rhizin  —  Myronic  acid  —  Phlorizin  —  Quercitrin  —  Salicin  — 
Populin  — Helicin —  Solanine  —  Thujin — Xanthorhamnin  — 

Indican               .......  579 

Polyglucosic  Alcohols              .....  583 

Cane-sugar  or  Saccharose — Parasaccharose  —  Melitose — Melez- 

itose  —  Trehalose  —  Mycose  —  Milk-sugar,  Lactin,  or  Lactose  584 

Gum         ........  588 

Oxygen-ethers  or  Anhydrides  of  the  Polyglucosic  alcohols        .  589 

Starch —  Dextrin  —  Starch  from  Iceland  moss  —  Inulin   .  589 

Cellulose  —  Woody  fibre  —  Xyloidin  and  Pyroxylin    .             .  592 

Glycogen      .......  594 

ORGANIC  ACIDS             .......  595 

Monatomic  Acids             ......  597 

Fatty  Acids,  CnH2n02         ......  597 

Formic  Acid             .             .             .             .             .             .  604 

Acetic  Acid        .......  606 

Metallic  Acetates              .....  607 

Acetic  Ethers              ......  610 

Acetic  Chloride  and  Oxide           ....  611 

Acids  derived  from  Acetic  Acid  by  substitution.  —  Chloracetic, 
Bromacetic,     and    lodacetic    acids  —  Thiacetlc    acid  — 
Amidacetic    acid,    or  Glycocine  —  Methyl-glycocine,  or 

Sarcosine                 ......  612 

Propionic  acid  —  Chloropropionic  and  Bromopropionic  acids 

—  Aniidopropionic  acid,  or  Alanine         .             .  615 
Butyric  acid      .             .             .             .             .             .             .616 

Valeric  or  Valerianic  acid                ....  617 

Caproic  acid  —  Amidocaproic,  or  Leucine       .             .             •  619 

CEnanthylic  acid       ......  619 

Caprylic  acid  —  Pelargonic  acid  —  Kutic  or  Capric  acid         .  620 

Laurie  acid  —  Myristic  acid             ....  621 

Palmitic  acid     .......  621 

Margaric  acid           ......  623 


CONTENTS.  Xvil 

PAC;  E 

Stearic  acid  —  Stearates —  Soaps         ....  623 

Arachidic  acid         ......  625 

Benic  or  Belienic,  Cerotic,  and  Melissic  acids            •.             .  625 

Acrylic  Acids,  CnH2n_202          .....  626 

Normal  Acrylic  acids :  Acrylic,  Crotonic,  Angelic,  Hypogacic, 

and  Oleic  acids           .             .             .             .              .             .  626 

Iso-acrylic  acids       ......  629 

Monatomic  Acids,  CnH2n_402. — Parasorbic,  Sorbic,  and  Gamphic 

acids       ........  632 

Monatomic  Acid,  CnH2n_602.  —  Hydrobenzoic  acid      .             .  632 

Monatomic  Acids,  CnH2n-802.  —  Aromatic  acids                  .             ..  633 

Benzoic  acid              ......  633 

Metallic  Benzoates  —  Benzoic  Chloride  and  Iodide     .             .  634 

Benzoic  Oxides  —  Benzoic  Sulphide  —  Dibenzoyl               .  635 

Chlorobenzoic,  Bromobenzoic,  and  Nitrobenzoic  acids            .  636 
Amidobenzoic     acid  —  Acetamidobonzoic    acid  —  Benzamid- 

acetic,  or  Hippuric  acid               ....  636 

Toluic  acid         .......  638 

Xylic,  Cumic,  and  Cymic  acids       ....  639 

Monatomic  Acids,  CnH2n_1002.  —  Cinnamic  acid  —  Atropic  acid  .  640 

Diatomic  and  Monobasic  Acids   .....  642 

1.  —  Acids  of  the  Lactic  Series,  CnH2n03    .  .  .  .642 

Glycollic  acid           ......  644 

Lactic  acid         .......  644 

Leucic  acid  .......  648 

Carbonic  acid — Carbonic  ethers  —  Sulphocarbonic  ethers    .  648 

2.  _  Pyruvic  Scries,  CnH2n_203              ....  651 
Pyruvic,  Convolvulinoleic,  Jalapinoleic,  and  Ricinoleic  acids  651 

3.  —Series  CnH2n_403 652 

Guaiacic  acid    .......  652 

4.  —  Series  OnH2n_803              .               ....  652 
Oxybenzoic,  Para-oxybenzoic,  and  Salicylic  acids      .             .  652 
Carbocresylic,  Cresotic,  Formobenzoic,  Anisic  acids         .  654 
Phloretic,  Thymotic,  and  Thymyl-carbonic  acids        .             .  655 

5.  —  Series  CJI,n-lQOz 655 

Coumaric  acid  .....                           .  655 

6.  — Series  C^H^Og.             .                           ...  656 
Benzilic  acid     .......  656 

Diatomic  and  Bibasic  Acids         .....  656 

1 .  —  Oxalic  or  Succinic  Series,  CnH2n_204  ....  657 

Oxalic  acid  .......  657 

Malonic  acid      .  .661 

2* 


XV111  CONTENTS. 

PAGE 

Succinic  acid,  Pyrotartaric,  Adipic,  Suberic              .             .  662 

Anchoic  or  Lepargylic —  Sebic  or  Sebacic,  and  Roccellic  acids  663 

2.—  Fumaric  Series  CnH2n_404           .....  663 

Fumaric  and  Maleic  acids  —  Itaconic,  Citraconic,  and  Mesa- 
conic  acids                 ......  663 

Camphoric  acid                  ......  664 

3.  —  Series  CJ^^O^                    .....  665 
Mellitic  acid          .......  665 

4.  —  Smes  CnH2n_804. 665 

Quinonic    or   Quinoylic  acid  —  Orsellinic   acid  —  Evernic  acid  665 

5.  —  Series  CnH2n_1004           ......  665 

Phthalic,  Terephthalic,  and  Insolinic  acids                 .             .  665 

Triatomic  and  Monobasic  Acids            .....  666 

Glyoxylie  acid                  ......  666 

Glyceric  acid  —  Oxysalicylic,  Eugetic,  and  Piperic  acids               .  667 

Triatomic  and  Bibasic  Acids            .....  668 

Malic  acid     ........  668 

Triatomic  and  Tribasic  Acids                .             .             .             .             .  669 

Aconitic  and  Carballylic  acids                 ....  670 

Tetratomic  and  Monobasic  Acids           .....  670 

Gallic  acid           .......  670 

Appendix  to  Gallic  Acid:  Tannic  acids,  or  Tannins         .             .  671 

Opianic  acid        .......  673 

Tetratomic  and  Bibasic  Acids                .....  673 

Tartaric  acid       .......  673 

Paratartaric  or  Racemic  acid           .....  677 

Rhodizonic  acid               ......  678 

Tetratomic  and  Tribasic  Acids              .....  678 

Citric  acid            .......  678 

Meconic  acid  —  Comenic  and  Pyrocomenic  acids                 .             .  679 

Pentatomic   Acids. — Quinic  or  Kinic  acid  —  Quinone  —  Hydroqui- 

none               ........  680 

Hezatomic  Acids.  —  Mannitic,  Saccharic,  and  Mucic  acids           .  681 

Sulpho-acids.  —  Sulphacetic  —  Disulphometholic  or  Methionic  — 
Sulphopropionic  —  Disulphetholic  —  Sulphobenzoic  —  Sulphoben- 
zolic — Disulphoberizolic — Sulphonaphthalic— Disulphonaphthalic 

—  Isethionic  and  Ethionic  acids  683 


CONTENTS. 


PAGE 

ALDEHYDES              .......  684 

Aldehydes  derived  from  Monatomic  Alcohols              .             .             .  684 

Formic  Aldehyde  —  Acetic  —  Acetal  —  Chloral  —  Acrylic    Al- 
dehyde, or  Acrolein     ......  686 

Benzoic  Aldehyde,  or  Bitter-almond  Oil — Toluic  Aldehyde  — 

Cumic,  Sycocerylic,  and  Cinnamic  Aldehydes  —  Camphor      .  690 

Aldehydes  derived  from  Diatomic  Alcohols            .             .             .  692 

Glyoxal  —  Salicylic    Aldehyde,    or    Salicylol  —  Derivatives    of 
Salicylol —  Coumarin  —  Anisic  Aldehyde  —  Furfurol  and  Fu- 

cusol      ........  692 

KETONES  —  Acetone  —  Benzone,  or  Benzophenone  —  Methyl-benzoyl  696 


ORGANIC  COMPOUNDS  CONTAINING  NITROGEN. 

CYANOGEN  COMPOUNDS             ......  700 

Cyanogen  and  Paracyanogen     .....  700 

Hydrogen  Cyanide  —  Hydrocyanic  or  Prussic  acid             .              •  701 

Metallic  Cyanides            ......  703 

Ferrocyanides  —  Ferricyanides  —  Prussian    blue  —  Cabalticy- 

anides  —  Nitro-prussides           .....  706 

Alcoholic  Cyanides,  or  Hydrocyanic  Ethers      .             .             .  710 

Isocyanides            .......  711 

Cyanic  and  Cyanuric  acids  —  Fulminic  acid  —  Fulminuric  acid  712 

Cyanogen  Chlorides  —  Bromide,  Iodide,  and  Sulphide              .  716 

Sulphocynnic  acid  —  Sulphocyanic  ethers                .             .             .  717 
Allyl  Isosulphocyanate,  or  Volatile  Oil  of  Mustard  —  Sinapoline 

—  Thiosinamine  —  Sinamine                .             .             .             .  719 

Seleniocyanates  —  Melam     ......  720 

Mellone  and  Mellonides              .             ...             .             .  721 

Urea              ........  721 

Uric  acid              .......  723 

Derivatives  of  Uric  acid  —  Allan toi'n  —  Alloxan  —  Alloxanic 
acid  —  Mesoxalic  acid  —  Mycomelic  acid  —  Parabanic  acid  — 
Oxaluric  acid  —  Thionuric  acid  —  Uramile  —  Alloxantin,  Di- 
aluric  acid  —  Hydurilic,  Dilituric,  and  Violuric  acids  —  Vio- 
lantin  —  Dibromobarbituric  acid,  or  Bromalloxan  —  Barbi- 
turic acid  — Murexide  .  724 


XX  CONTENTS. 

PAGE 

COMPOUND  AMMONIAS  OR  AMINES       .....         732 

Amines  derived  from  Monatomic  Alcohols  ;  Monamines  .  733 

Bases  of  the  Ethyl  Series.  —  Ethylamine  —  Biethylamine  —  Tri- 

ethylamine  —  Tetrethyl-ammonium  hydrate  .  .         735 

Bases  of  the  Methyl  Series.  —  Methylamine  —  Bimethylamine  — 

Trimethylamine  —  Tetramethyl-ammonium  hydrate  .  737 


38 


Bases  of  the  Amyl  Series.  —  Amylamine  —  Biamylamine  —  Tri- 
amylamine  —  Tetramyl-ammonium  hydrate     .  .  . 

Bases  of  the  Aromatic  Series      .....  739 

Aniline  .......  739 

Paraniline  —  Chloraniline  —  Nitraniline  .  .  741 

Diphenylamine  and  Triphenylamine  —  Cyananiline  —  Ethyl- 
aniline  —  Diethylaniline  —  Ethyl-amyl-aniline  —  Methyl- 

ethyl-amyl-phenylammonium  hydrate       .  .  .  742 

Toluidine  and  Benzylamine  ....  742 

Xylidine  —  Cumidine  and  Cymidine  .  .  .  743 

Naphthalidene  ......  743 

Diamines  and  Triamines  ......  743 

Ethene-diamine  and  Diethene-diamine  .  .  .  743 

Diethene-  and  Triethene-triamine        •  .  .  .  744 

Diphenyl-ethene-diamine  and  Diphenyl-diethene-diamine        .  744 

Methenyl-diphenyl-diamine,  or  Formyl-aniline       .  .  .  745 

Phenylene-diamine          ......  745 

Carbodiphenyl-triamine,  or  Melaniline        ....  745 

Carbotriphenyl-triamine,  or  Phenyl-melaniline  .  .  745 

Aniline  Colors:  Aniline-purple  or  Mauve  .  .  .  745 

Aniline-red  —  Rosaniline         .....  746 

Aniline-blue  and  Aniline-violet  —  Aniline-yellow  Chrysaniline  747 


Appendix  to  the  Alcoholic  Ammonias. 

I. — Artificial  Organic  Bases  obtained  from  various  Sources                .  748 

Bases  obtained  by  Destructive  Distillation:  Chinoline —  Lepidine  — 

Cryptidine — Picoline               .....  748 

Bases  from  Animal  Oil :  Petinine  —  Pyridine  —  Lutidine  —  Colli- 

dine  —  Parvoline                .             .                           .             .             .  749 

Bases  from  Aldehydes:  Furfurine  —  Amarine  —  Thialdine  —  Ala- 
nine  and  its  homologues         .....  750 

II.  —  Natural  Organic  Bases  or  Alkaloids  .  .  .751 

Morphine,  and  its  salts               .....  751 

Narcotine  —  Opianic  and  Hemipinic  acids  —  Cotarnine  —  Codeine  753 

Thebaine  —  Pseudo-morphine — Narceine  —  Meconin         .             .  754 

Cinchonine  and  Quinine — Quinoi'dine                 .             .             .  754 

Strychnine  and  Brucine       .  756 


CONTENTS.  xxi 


Veratrine  —  Harmaline  —  Caffeine  or  Theine  —  Theobromine  — 

Xantliine  .......  756 

Sarcine  —  Guanine  —  Guanidine  —  Creatin  —  Creatinine  —  Sarco- 

sine  ........  758 

Berberine  —  Piperine  —  Conine  —  Hyoscyamine  —  Atropine  — 

Solanine  —  Aconitine  —  Delphinine  —  Emetine  —  Curarine  .  760 

III.  —  Phosphorus,  Antimony,  and  Arsenic  Bases  .  .  760 
Phosphims. — Triethylphosphine  and  Trimethylphosphine             .         760 
Antimony-bases  or  Stibines.  —  Triethylstibine  or  Stibethyl  —  Tetra- 

methylstibonium  hydrate        .....  761 

Arsenic-bases.  —  Triethylarsine         .....  762 

Arsendimethyl  or  Cacodyl       .....  763 

Arsenmonomethyl  ......  766 

Triethylbismuthine  or  Bismethyl    .....  767 

Borethyl        ........         767 

Diatomic  Bases  of  the  Phosphorus  and  Arsenic  Scries       .  .  767 

IV.  — Compounds  of  Alcohol-radicals  with  Bivalent  and  Quadrivalent 

Metals  and  Metalloids  .....         768 

Zinc  Ethyl  or  Zinc  Ethide,  768— Zinc  Methide,  769  — Potassium 
Ethide  and  Methide,  769  —  Mercuric  Ethide,  769  —  Aluminium 
Methide  and  Ethide,  769  —  Ethyl-compounds  of  Tin,  770  — 
Plumbic  Ethide,  770  —  Alcoholic  compounds  of  Tellurium, 
Selenium,  and  Sulphur,  771. 

AMIDES: 

Amides  derived  from  Monatomic  Acids  —  Acetamide  —  Benza- 

mide  —  Secondary  and  Tertiary  Monamides  .  .  .  772 

Amides  derived  from  Diatomic  and  Monobasic  acids     .  .  774 

Amides  derived  from  Diatomic  and  Bibasic  acids  —  Amides  of 

Carbonic  and  Oxalic  acids  .....  775 

Amides  derived  from  acids  of  higher  Atomicity — Malamide  and 
Malamio  acid  —  Asparagin  and  Aspartic  acid  —  Amides  of 
Citric  acid  .......  778 

UNCLASSIFIED  ORGANIC  COMPOUNDS. 
Organic  Coloring  Principles        .....  781 

Indigo,  781  —  Coloring  Matters  from  Lichens,  785  —  Cochi- 
neal, 787 — Madder-colors  ;  Alizarin,  Purpurin,  Garancin,  787 
—  Safflower,  788  —  Brazil-wood  —  Log-wood  —  Yellow  Dye- 
woods  —  Aloes  .  ....  789 

Eesins  and  Balsams        .  790 


XX11  CONTENTS. 

PAKT   IV. 

ANIMAL  CHEMISTRY. 

PAGE 

INTRODUCTION  ........        792 

Albuminous  Substances       ......  793 

Serum  Albumin,  793  —  Egg  Albumin,  794  —  Casein  and  Albu- 
minate  or  Protein,  794  —  Paralbumin,  795 — Syntonin  or  Para- 
peptone,  795  —  Myosin,  796  —  Fibrino-plastic  substance  and 
Fibrinogen,  or  Paraglobin,  or  Paraglobulin,  796  —  Coagulated 
Albuminous  substances,  797  —  Amyloid  substance,  797  —  Pep- 
tone, 797  —  Metalbumin,  798  —  Haemoglobin,  Haematoglobulin, 
or  Hoematocrystallin,  798  —  Hrematin,  799  —  Mucin,  Pyin,  Pep- 
sin, Sugar-forming  Ferments  of  Saliva  and  Pancreatic  Fluid, 
800  — Gelatin  and  Chondrin,  Horny  Matter  or  Elastin,  801  — 
Keratin,  Fibroin,  Spongin,  803  —  Conchiolin,  Chitin,  Protagon 
and  Neurine,  803  —  Inosinic  acid,  Cnlorohodic  acid,  Excretin, 
804. 

Animal  Fluids  .  .  .  .  .  .805 

Blood,  805  —  Urine,  807  —  Urinary  Calculi,  809  —  Sweat,  Saliva, 
Gastric  Juice,  Bile,  811  —  Pancreatic  Fluid,  Intestinal  Juice, 
Lymph,  Mucus  and  Pus,  815  — Milk,  816. 

The  Animal  Textures    .  .  .  .  .  .  81 8 

Nervous  Substance,  Contractile  Substance,  Elastic  Tissue ;  Skin 
818  — Bones  and  Teeth,  818. 

On  Chemical  Functions  in  Animals. 

Eespiration  ........         820 

Nutrition  of  Animals       ......  822 

Nutrition  of  Plants  .  825 


APPENDIX. 

Hydrometer  Tables        ......  827 

Table  of  the  Tension  of  Vapor  of  Water  at  different  Temperatures  829 
Tables  of  the  proportions  by  Weight  and  Volume  of  Anhydrous 

Alcohol  in  Spirits  of  different  Densities  .  .  .  831 

Analysis  of  Mineral  Waters  .....  832 

Analysis  of  Fresh  Spring  and  River  Water  .  .  .  834 

Weights  and  Measures  .  .  .  .  .  836 

Comparison  of  French  and  English  Measures  .  .  .  837 

Tables  for  converting  degrees  of  the  Centigrade  Thermometer 

into  degrees  of  Fahrenheit's  Scale      .  .  839 


LIST  OF  ILLUSTRATIONS. 


FIG.  PAGE 

1  Specific  gravity  bottle 28 

2  "  "  "     28 

3  «  «  a     29 

4  Theorem  of  Archimedes 29 

5  "  "  30 

6  Specific  gravity  of  heavy  solids..  30 

7  "  "  light        "     ..  31 

8  Lovis  beads 32 

9  Hydrometer 32 

10  Urinometer 33 

11  Specific  gravity  of  liquids 33 

12  Elasticity  of  gases 35 

13  Single  air-puinp 36 

14  Double         «         36 

15  Improved    "         37 

16  "         "         38 

17  Barometer 39 

18  "          40 

19  "          41 

20  Expansion  of  solids 42 

21  «  "  liquids 42 

22  "  "    gases 42 

23  Thermometer,  graduation 43 

24  "  air , 44 

"  differential 44 

26  Difference  of  expansion  in  metals  45 

27*  Pendulum,  gridiron........ 46 

"  mercury 46 

29  Compensation  balance 46 

30  Darnell's  pyrometer 47 

31  Expansion  of  mercury 49 

!2  Comparative  expansion  of  liquids  49 

33  Atmospheric   currents 52 

34  "  «         52 

35  "       .  «         53 

36  Boiling  paradox 58 

37  Steam-bath 60 

38  "      engine 61 

39  Distillation  ,..  62 

40  "          and  condensation 62 

41  Tension  of  vapor ..  63 

42  «  «  64 

•i:'.  Wet-bulb    hygrometer 66 

44  Condensation  of  gases (>(! 

"             "  carbon  dioxide...  67 
46  Cold  by  evaporation 68 


FIG.  PAGE 

47  Wollaston's  cryophorus 68 

48  Daniell's  hygrometer 69 

49  Joule's  apparatus 76 

50  "  "         76 

51  "  «         76 

52  Light,  reflection 84 

53  "       refraction 84 

54  "  "  85 

55  "  "  85 

56  Spectrum 86 

57  "         87 

58  «         of  metals s/ 

59  Spectroscope 88 

60  Absorption-lines 91 

61  «  "     91 

62  Polarization  of  light 92 

63  "  "         92 

64  "  "         92 

65  Saccharimeter 94 

66  Reflection  of  heat 99 

67  "  "     100 

68  Effect  of  electric  current  on  the 

magnetic  needle 102 

69  "  "         103 

70  Thermo-electric  pile 103 

71  "  "          103 

72  Melloni's  instrument  for  measur- 

ing transmitted  heat 104 

73  Magnetic  polarity 108 

74  "  "      108 

75  Electro-repulsion  ....; 115 

76  Electroscope  115 

77  Electric  polarity 115 

78  Electric  machine 116 

79  "  «        117 

80  Leyden  jar 118 

81  Electrophorus 119 

82  Volta'spile 120 

83  Crown  of  oups 120 

84  Cruikshank's  trough 121 

85  Relation   of  magnetic   needle   to 

electric  current 122 

86  Galvanoscope  123 

87  Magnetic  effect  of  current 123 

88  «  "  "      124 

89  Electro-magnet 125 

xxiii 


XXIV 


LIST  OF  ILLUSTRATIONS. 


FIG.  PAGE 

90  Ruhmkorff's   coil 126 

91  Apparatus  for  oxygen 128 

92  Hydro-pneumatic   trough 130 

93  Transferring  gases 130 

94  Pepys'  hydro- pneumatic  appara- 

tus  131 

95  Apparatus  for  hydrogen 136 

96  Levity  of  hydrogen 137 

97  Diffusion  of  gases 138 

98  Heming's   safety-jet 141 

99  Musical  sounds  by  combustion  of 

hydrogen 142 

100  Catalytic  effect  of  platinum 143 

101  Decomposition  of  water 143 

102  Cavendish's  eudiometer 144 

103  Analysis  of  water  145 

104  Solubility  of  salts 147 

105  Dialysis  149 

106  "         149 

107  "        149 

108  «         149 

109  Osmose 150 

110  «       150 

111  "       150 

112  Preparation  of  nitrogen 154 

113  "  "  155 

114  lire's  eudiometer 156 

115  Simple         "  157 

116  Preparation    of    nitrogen    mon- 

oxide  160 

117  Crystalline  forms  of  diamond. ..164 

118  Preparation  of  carbon  dioxide. ..166 

119  Formation   of  connecting  tubes 

of  india-rubber 166 

120  Blast  furnace 173 

121  Reverberatory  furnace 173 

122  Structure  of  flame 175 

123  Mouth  blow-pipe 175 

124  Structure  of  blow-pipe  flame 176 

125  Argand  lamp 176 

126  Spirit-lamp  176 

127  Mitchell's  lamp 176 

128  Gas-lamp 177 

129  Bunsen's  burner 177 

130  Davy's  safety  lamp 178 

131  Hemming's  safety  jet 179 

132  Preparation  of  chlorine 180 

133  •<         "       hydrogen  chloride.182 

134  Safety-tube  183 

135  Preparation  of  hydrogen  iodide.,190 

136  Crystals  of  sulphur 193 

137  "  "        193 

138  Apparatus  for  hydrogens  ulphide  201 

139  Preparation  of  silica 210 

140  "  "   phosphorus 212 

141  Electrolysis  of  hydrogen    chlo- 

ride   247 

142  "  "  "  247 

143  Voltameter 249 

144  Decomposition    without  contact 

of  metals 250 


FIG.  PAGE 

145  Wollaston's  battery 252 

146  Daniell's  "       253 

147  Grove's  "       253 

148  Carbon  "       254 

149  Electrotype 254 

150  Lead-tree 255 

151  Goniometer,  common 258 

152  "  reflecting 258 

153  "  principles  of 259 

154  Crystals,  regular  system 260 

155  "         dinaetric       <       261 

156  "  rhombohedral  '       261 

157  "         trimetric      <       261 

158  "       monoclinic     *       262 

159  "         triclinic        '       262 

160  Passage  of  cube  to  octohedron...263 

161  "  octohedron  to   tetra- 

hedron  263 

162  Wire-drawing 268 

163  Preparation  of  potassium 291 

164  Salt-cake  furnace. 302 

165  Alkalimeter 305 

166  "  Gay-Lussac's 305 

167  "  "  "       305 

168  "          Mohr's 305 

169  Mohr's  clamp 306 

170  Apparatus   lor  determining  car- 

bon  dioxide 306 

171  "  "  ''  306 

173  Iron  manufacture.  Blast-furnace.402 

174  Subliming  tube  for  arsenic 425 

175  Marsh's  apparatus 427 

176  Organic  analysis,  weighing  tube..449 

177  "  "  decomposing   "     449 

178  "  «         chauffer  450 

179  "  "         water-tube 450 

180  "  "  carbon  dioxide 

bulbs 450 

181  "  "         apparatus  com- 

plete  450 

182  Hofmann's  gas-apparatus 451 

183  «  "  "  451 

184  "  "  "  451 

185  Bulb  for  liquid 452 

186  Determination  of  nitrogen 453 

187  Pipette 453 

188  Determination  of  nitrogen,   Du- 

mas  454 

189  Determination  of  nitrogen  as  am- 

monia   456 

190  Determination  of  density  of  va- 

pors  459 

191  Preparation  of  ether 524 

192  "      of  chlorides  of  carbon..559 

193  Starch-granules  589 

194  Mohr's    apparatus    for   benzoic 

acid   634 

195  Preparation  of  tannic  acid 672 

196  Preparation  of  cacodyl 764 

197  Blood  globules 806 


MANUAL  OF  CHEMISTRY. 


INTRODUCTION. 

THE  Science  of  Chemistry  has  for  its  object  the  study  of  the  nature  and 
properties  of  all  the  materials  which  enter  into  the  composition  or  struc- 
ture of  the  earth,  the  sea,  and  the  air,  and  of  the  various  organized  or  liv- 
ing beings  which  inhabit  these  latter.  Every  object  accessible  to  man,  or 
which  may  be  handled  and  examined,  is  thus  embraced  by  the  wide  circle 
of  Chemical  Science. 

The  highest  efforts  of  Chemistry  are  constantly  directed  to  the  discovery 
of  the  general  laws  or  rules  which  regulate  the  formation  of  chemical  com- 
pounds, and  determine  the  action  of  one  substance  upon  another.  These 
laws  are  deduced  from  careful  observation  and  comparison  of  the  proper- 
ties and  relations  of  vast  numbers  of  individual  substances;  —  and  by  this 
method  alone.  The  science  is  entirely  experimental,  and  all  its  conclusions 
the  results  of  skilful  and  systematic  experimental  investigation. 

The  applications  of  the  discoveries  of  Chemistry  to  the  arts  of  life,  and 
to  the  relief  of  human  suffering  in  disease,  are,  in  the  present  state  of  the- 
science,  both  very  numerous  and  very  important,  and  encourage  the  hope 
of  still  greater  benefits  from  more  extended  knowledge  than  that  now 
enjoyed. 

In  ordinary  scientific  speech,  the  term  chemical  is  applied  to  changes 
which  permanently  affect  the  properties  or  characters  of  bodies,  in  oppo- 
sition to  effects  termed  physical,  which  are  not  attended  by  such  conse- 
quences. Changes  of  decomposition  or  combination  are  thus  easily  distin- 
guished from  those  temporarily  brought  about  by  heat,  electricity,  mag- 
netism, and  the  attractive  forces,  whose  laws  and  effects  lie  within  the 
province  of  Physics  or  Natural  Philosophy. 

Nearly  all  the  objects  presented  by  the  visible  world  are  of  a  compound 
nature,  being  chemical  compounds,  or  variously  disposed  mixtures  of  chemi- 
cal compounds,  capable  of  being  resolved  into  simpler  forms  of  matter. 
Thus,  a  piece  of  limestone  or  marble,  by  the  application  of  a  red-heat,  is 
decomposed  into  quicklime  and  a  gaseous  body,  carbon  dioxide.  Both  lime 
3  25 


26  INTRODUCTION. 

and  carbon  dioxide  are  in  their  turn  susceptible  of  decomposition,  the  for- 
mer into  a  metal,  calcium,  and  oxygen,  and  the  latter  into  carbon  and 
oxygen.  For  this  purpose,  however,  simple  heat  does  not  suffice,  the  reso- 
lution of  these  substances  into  their  components  demanding  the  exertion 
of  a  high  degree  of  chemical  energy.  Beyond  this  second  step  of  decom- 
position the  efforts  of  Chemistry  have  hitherto  been  found  to  fail;  and  the 
three  bodies,  calcium,  carbon,  and  oxygen,  having  resisted  all  attempts  to 
resolve  them  into  simpler  forms  of  matter,  are  accordingly  admitted  into 
the  list  of  elements;  —  not  from  any  belief  in  their  real  oneness  of  nature, 
but  from  the  absence  of  any  evidence  that  they  contain  more  than  one 
description  of  matter. 

The  partial  study  of  certain  branches  of  Physical  Science,  as  the  physi- 
cal constitution  of  gases,  the  chief  phenomena  of  heat  and  electricity,  and  a 
few  other  subjects,  forms  so  indispensable  an  introduction  to  Chemistry 
itself,  that  it  is  rarely  omitted  in  the  usual  courses  of  oral  instruction.  A 
sketch  of  these  subjects  is,  in  accordance  with  these  views,  placed  at  the 
commencement  of  the  present  volume. 


PART   I. -PHYSICS. 


OF  DENSITY  AND  SPECIFIC  GRAVITY. 

IT  is  of  great  importance  at  the  outset  to  understand  clearly  what  is  meant 
by  the  terms  density  and  specific  gravity.  By  the  density  of  a  body  is  meant 
its  mass,  or  quantity  of  matter,  compared  with  the  mass  or  quantity  of  matter 
of  an  equal  volume  of  some  standard  body  arbitrarily  chosen.  Specific  grav- 
ity denotes  the  weight  of  a  body,  as  compared  with  the  weight  of  an  equal 
bulk,  or  volume,  of  the  standard  body,  which  is  reckoned  as  unity.*  In 
all  cases  of  solids  and  liquids,  the  standard  of  unity  adopted  in  this  country 
is  pure  water  at  the  temperature  of  15-5°  C.  (60°  Fahr.)  Anything  else 
might  have  been  chosen  ;  there  is  nothing  in  water  to  render  its  adoption 
for  the  purpose  mentioned  indispensable:  it  is  simply  taken  for  the  sake  of 
convenience,  being  always  at  hand,  and  easily  obtained  in  a  state  of  perfect 
purity.  An  ordinary  expression  of  specific  weight,  therefore,  is  a  number 
explaining  how  many  times  the  weight  of  an  equal  bulk  of  water  is  con- 
tained in  the  weight  of  the  substance  spoken  of.  If,  for  example,  we  say, 
that  concentrated  oil  of  vitriol  has  a  specific  gravity  equal  to  1-85,  or  that 
perfectly  pure  alcohol  has  a  density  of  0-794  at  15-5°  C.,  we  mean  that 
equal  bulks  of  these  two  liquids  and  of  distilled  water  possess  weights  in 
the  proportion  of  the  numbers  1-85,  0-794,  and  1;  or  1850,  794,  and  1000. 
It  is  necessary  to  be  particular  about  the  temperature,  for,  as  will  be  here- 
after shown,  liquids  are  extremely  expansible  by  heat;  otherwise  a  constant 
bulk  of  the  same  liquid  will  not  retain  a  constant  weight.  It  will  be  pro- 
per to  begin  with  the  description  of  the  mode  in  which  the  specific  gravity 
of  liquids  is  determined  :  this  is  the  simplest  case,  and  the  one  which  best 
illustrates  the  general  principle. 

In  order  to  obtain  at  pleasure  the  specific  gravity  of  any  particular  liquid 
compared  with  that  of  water,  it  is  only  requisite  to  weigh  equal  bulks  at 
the  standard  temperature,  and  then  divide  the  weight  of  the  liquid  by  the 
weight  of  the  water  ;  the  quotient  will  of  course  be  greater  or  less  than 
unity,  as  the  liquid  experimented  on  is  heavier  or  lighter  than  water.  Now, 
to  weigh  equal  bulks  of  two  fluids,  the  simplest  and  best  method  is  clearly 
to  weigh  them  in  succession  in  the  same  vessel,  taking  care  that  it  is  equally 
full  on  both  occasions,  a  condition  very  easy  of  fulfilment. 

A  thin  glass  bottle,  or  flask,  with  a  narrow  neck,  is  procured,  of  the 
form  represented  below  (fig.  1),  and  of  such  capacity  as  to  contain,  when 
filled  to  about  half-way  up  the  neck,  exactly  1000  grains  of  distilled  water 
at  15-5°  C.  Such  a  flask  is  readily  procured  from  any  one  of  the  Italian 


*Inothor  words,  density  moans  comparative  mass,  and  specific  gravity  comparativ 
These  expressions,  although  really  relating  to  distinct  things,  are  often  used  quite  indifferently 
in  chemical  writings,  and  without  practical  inconvenience,  since  mass  and  weight  are  directly 
proportional  to  each  other. 


28  DENSITY    AND    SPECIFIC    GRAVITY. 

artificers,  to  be  found  in  every  large  town,  who  manufacture  cheap  ther- 
mometers for  sale.  A  counterpoise  of  the  exact  weight  of  the  empty  bottle 
is  made  from  a  bit  of  brass,  an  old  weight,  or  something  of  the  kind,  and 
carefully  adjusted  by  filing.  The  bottle  is  then  graduated,  by  introducing 
water  at  15-5°,  until  it  exactly  balances  the  1000-grain  weight  and  counter- 
poise in  the  opposite  scale  ;  the  height  at  which  the  water  stands  in  the 
neck  is  marked  by  a  scratch,  and  the  instrument  is  complete  for  use.  The 
liquid  to  be  examined  is  brought  to  the  temperature  of  15-5°,  and  with  it 
the  bottle  is  filled  up  to  the  mark  before  mentioned ;  it  is  then  weighed, 
the  counterpoise  being  used  as  before,  and  the  specific  gravity  directly 
ascertained. 

Fig.  1.  Fig.  2. 


A  watery  liquid  in  a  narrow  glass  tube  always  presents  a  curved  surface, 
from  the  molecular  action  of  the  glass,  the  concavity  being  upwards.  It  is 
better,  on  this  account,  in  graduating  the  bottle,  to  make  two  scratches,  as 
represented  in  the  figure,  one  at  the  top  and  the  other  at  the  bottom  of  the 
curve :  this  prevents  any  future  mistake.  The  marks  are  easily  made  by 
a  fine,  sharp  triangular  file,  the  hard  point  of  which,  also,  it  may  be 
observed,  answers  perfectly  well  for  writing  upon  glass,  in  the  absence  of 
a  proper  diamond  pencil. 

It  will  be  quite  obvious  that  the  adoption  of  a  flask  holding  exactly  1000 
grains  of  water  has  no  other  object  than  to  save  the  trouble  of  a  very  tri- 
fling calculation;  any  other  quantity  would  answer  just  as  well,  and,  in 
fact,  the  experimental  chemist  is  often  compelled  to  use  a  bottle  of  much 
smaller  dimensions,  from  scarcity  of  the  liquid  to  be  examined. 

When  the  specific  gravity  of  a  liquid  is  to  be  determined  with  great  accu- 
racy, a  case  which  frequently  occurs  in  chemical  inquiries,  a  little  glass 
bottle  is  used,  of  the  form  showed  in  fig.  2.  This  bottle  is  provided  with  a 
perforated  conical  glass  stopper,  most  accurately  fitted  by  grinding.  By 
completely  filling  the  little  bottle  with  liquid,  and  carefully  removing  the 
portion  of  liquid  which  is  displaced  when  the  stopper  is  inserted,  an  unal- 


DENSITY   AND    SPECIFIC    GRAVITY. 


29 


srable  measure  is  obtained.     The  least  possible  quantity  of  grease  applied 
to  the  stopper  greatly  promotes  the  exact  fitting. 

When  the  chemist  has  only  a  small  quantity  of  a  fluid  at  his  Fig-  3. 
disposal,  and  wishes  not  to  lose  it,  the  little  glass  vessel  (fig.  3) 
is  particularly  useful.  It  is  formed  by  blowing  a  bubble  on  a 
glass  tube.  On  that  portion  of  the  tube  which  is  narrowed  by 
drawing  the  tube  out  over  a  lamp,  a  fine  scratch  is  made  with  a 
diamond.  The  bubble  is  filled  up  to  this  mark  with  a  liquid 
whilst  it  stands  in  water  the  temperature  of  which  is  exactly 
known.  A  very  fine  funnel  is  used  for  filling  the  bubble,  the 
stem  of  the  funnel  being  drawn  out  so  as  to  enter  the  tube,  and 
the  upper  opening  of  the  funnel  being  small  enough  to  be  closed 
by  the  finger.  The  glass  stopper  is  only  wanted  as  a  guard, 
and  does  not  require  to  fit  perfectly. 

The  determination  of  the  specific  gravity  of  a  solid  body  is 
made  according  to  the  same  principles,  and  may  be  performed 
with  the  specific-gravity  bottle  (fig.  2).  The  bottle  is  first 
weighed  full  of  water ;  the  solid  is  then  placed  in  the  same  pan 
of  the  balance,  and  its  weight  determined;  finally,  the  solid 
is  put  into  the  bottle,  displacing  an  equal  bulk  of  water,  the 
weight  of  which  is  determined  by  the  loss  on  again  weighing.  Thus  the 
weights  of  the  solid  and  that  of  an  equal  bulk  of  water  are  obtained.  The 
former  divided  by  the  latter  gives  the  specific  gravity. 

For  example,  the  weight  of  a  small  piece  of  silver  wire 

was  found  to  be    .         .         .         .         .         .         .         .       98-18  grains. 

Glass  bottle  filled  with  water 294-69       " 


After  an  equal  volume  of  water  was  displaced  by  the  sil- 
ver, the  weight  was      ....... 

Hence  the  displaced  water  weighed          .  . 

From    this,   the    specific    gravity   of  the    silver )  98-18 


Another  highly  ingenious,  but  less  exact  method  of 
determining  the  specific  gravity  of  solids,  is  based  on 
the  well-known  theorem  of  Archimedes. 
This  theorem  may  be  thus  expressed  : 

When  a  solid  is  immersed  in  a  fluid,  it  loses  a  por- 
tion of  its  weight ;   and  this  portion  is  equal  to 
the  weight  of  the  fluid  which  it  displaces ;  that 
is,  to  the  weight  of  its  own  bulk  of  that  fluid. 
It  is  easy  to  give  experimental  proof  of  this  very  im- 
portant proposition,  as  well  as  to  establish  it  by  reason- 
ing.    Figure  4  represents   a   little   apparatus  for   the 
former    purpose.     This  consists  of  a  thin   cylindrical 
vessel  of  brass,  into  the  interior  of  which  fits  very  accu- 
rately a  solid  cylinder  of  the  same  metal,  thus  exactly 
filling  it.     When  the  cylinder  is  suspended  beneath  the 
bucket,  as  seen  in  the  sketch,  the  whole  hung  from  the 
arm   of  a  balance    and   counterpoised,    and    then    the 
cylinder  itself  immersed  in  water,  it  will  be  found  to 
have  lost  a  certain  weight;  and  that  this  loss  is  pre- 
cisely equal  to  the  weight  of  an  equal  bulk  of  water, 
may  then  he  proved  by  filling  the  bucket   to  the  brim, 
whereupon  the  equilibrium  will  be  restored. 
3* 


392-87 
383-54 


30 


DENSITY   AND    SPECIFIC    GRAVITY. 


Fig.  5. 


The  consideration  of  the  great  hydrostatic  law  of  fluid  pressure  easily 
proves  the  truth  of  the  principle  laid  down.  Let  the  reader  figure  to 
himself  a  vessel  of  water,  having  immersed  in  it  a  solid  cylindrical  or  rec- 
tangular body,  and  so  adjusted  with  respect  to  density,  that  it  shall  float 
indifferently  in  any  part  beneath  the  surface  (fig.  5.) 
Now  the  law  of  fluid  pressure  is  to  this  effect: 

The  pressure  exerted  by  a  fluid  on  any  point  of  the  containing  vessel,  or 
on  any  point  of  a  body  immersed  beneath  its  surface,  is  dependent,  firstly, 
upon  the  density  of  the  fluid,  and,  secondly,  upon  the  vertical  depth  of  the 
point  in  question  below  the  surface.  It  is  independent 
of  the  form  and  lateral  dimensions  of  the  vessel  or 
immersed  body.  Moreover,  owing  to  the  peculiar 
physical  constitution  of  fluids,  this  pressure  is  exerted 
in  every  direction,  upward,  downward,  and  laterally, 
a  with  equal  force. 

The  floating  body  is  in  a  state  of  equilibrium  ;  there- 
fore the  pressure  downward  caused  by  its  gravitation 
must  be  exactly  compensated  by  the  upward  trans- 
mitted pressure  of  the  column  of  water  a,  b.  But  this 
pressure  downward  is  obviously  equal  to  the  weight 
of  an  equal  quantity  of  water,  since  the  body  of  neces- 
sity displaces  its  own  bulk.  Hence  the  weight  which 


Fig.  6. 


a  body  loses  when  immersed  in,  or  floated  on  water,  is  equal  to  the  weight 
of  the  volume  of  water  displaced  by  that  body. 

Whatever  be  the  density  of  the  substance,  it  will  be  buoyed  up  to  this 
amount :  in  the  case  supposed,  the  buoyancy  is  equal  to  the  whole  weight 
of  the  body,  which  is  tlms,  while  in  the  water,  reduced  to  nothing. 

A  little  reflection  will  show  that  the  same  reasoning 
may  be  applied  to  a  body  of  irregular  form ;  besides,  a 
solid  of  any  figure  may  be  divided  by  the  imagination 
into  a  multitude  of  little  perpendicular  prisms  or  cylin- 
ders, to  each  of  which  the  argument  may  be  applied. 
What  is  true  of  each  individually  must  necessarily  be  true 
of  the  whole  together. 

This  is  the  fundamental  principle;  its  application  is 
made  in  the  following  manner : — Let  it  be  required,  for 
example,  to  know  the  specific  gravity  of  a  body  of 
extremely  irregular  form,  as  a  small  group  of  rock  crys- 
tals :  the  first  part  of  the  operation  consists  in  determining 
its  absolute  weight,  or,  more  correctly  speaking,  its  weight 
in  air ;  it  is  next  suspended  from  the  balance-pan  by  a 
fine  horsehair,  immersed  completely  in  pure  water  at 
15-5°,  and  again  weighed.  It  now  weighs  less,  the  dif- 
ference being  the  weight  of  the  water  it  displaces,  that 
is,  the  weight  of  an  equal  bulk.  This  being  known, 
nothing  more  is  required  than  to  find,  by  division,  how 
many  times  the  latter  number  is  contained  in  the  former; 
the  quotient  will  be  the  density,  water,  at  the  tempera- 
ture of  15-5°,  being  taken  =  1.  For  example: 


The  quartz-crystals  weigh  in  air 
When  immersed  in  water,  they  weigh 


293-7  grains. 
180-1       " 


Difference,  being  the  weight  of  an  equal  volume  of  water     113-6 

293-7 

=  2-59,  the  specific  gravity  required. 

113-6 


DENSITY    AND    SPECIFIC    GRAVITY.  81 

The  rule  is  generally  thus  written:  "  Divide  the  weight  in  air  by  the 
loss  of  weight  in  water,  and  the  quotient  will  be  the  specific  p.  7 

gravity."  In  reality  it  is  not  the  weight  in  air  which  is 
required,  but  the  weight  the  body  would  have  in  empty 
space:  the  error  introduced,  namely,  the  weight  of  an 
equal  bulk  of  air  is  so  trifling,  that  it  is  usually  neglected. 

Sometimes  the  body  to  be  examined  is  lighter  than  water, 
and  floats.  In  this  case,  it  is  first  weighed,  and  afterwards 
attached  to  a  piece  of  metal  heavy  enough  to  sink  it,  and 
suspended  from  the  balance.  The  whole  is  then  exactly 
weighed,  immersed  in  water,  and  again  weighed.  The  dif- 
ference between  the  two  weighings  gives  the  weight  of  a 
quantity  of  water  equal  in  bulk  to  both  together.  The 
light  substance  is  then  detached,  and  the  same  operation  of 
weighing  in  air,  and  again  in  water,  repeated  on  the  piece 
of  metal.  These  data  give  the  means  of  finding  the  specific  gravity,  as 
will  be  at  once  seen  by  the  following  example: 

Light  substance  (a  piece  of  wax)  weighs  in  air          .         .     133-7  grains. 

Attached  to  a  piece  of  brass,  the  whole  now  weighs          .     183-7       " 
Immersed  in  water,  the  system  weighs      ....       38-8       " 

Weight  of  water  equal  in  bulk  to  brass  and  wax        .         .     144-9       " 

Weight  of  brass  in  air 50-0       " 

Weight  of  brass  in  water 44-4       " 

Weight  of  equal  bulk  of  water 5-6       " 

Bulk  of  water  equal  to  wax  and  brass       ....     144-9       " 
Bulk  of  water  equal  to  brass  alone 5-6       " 

Bulk  of  water  equal  to  wax  alone 139-3       " 

133-7 

=  0-9598  • 

1393 

'  In  all  such  experiments  it  is  necessary  to  pay  attention  to  the  tempera- 
ture and  purity  of  the  water,  and  to  remove  with  great  care  all  adhering 
air-bubbles,*  otherwise  a  false  result  will  be  obtained. 

Other  cases  require  mention  in  which  these  operations  must  be  modified 
to  meet  particular  difficulties.  One  of  these  happens  when  the  substance 
is  dissolved  or  acted  upon  by  water.  The  difficulty  is  easily  overcome  by 
substituting  some  other  liquid  of  known  density  which  experience  shows  is 
without  action.  Alcohol  or  oil  of  turpentine  may  generally  be  used  when 
water  is  inadmissible.  Suppose,  for  instance,  the  specific  gravity  of  crys- 
tallized sugar  is  required,  we  proceed  in  the  following  way :  The  specific 
gravity  of  the  oil  of  turpentine  is  first  carefully  determined ;  let  it  be  0-87 ; 
the  sugar  is  next  weighed  in  the  air,  then  suspended  by  a  horsehair,  and 
weighed  in  the  oil ;  the  difference  is  the  weight  of  an  equal  bulk  of  the  lat- 
ter ;  a  simple  calculation  gives  the  weight  of  a  corresponding  volume  of 
water :  — 

*  A  simple  plan  of  avoiding  altogether  the  adhesion  of  air-bubbles,  which  often  are  not  easily 
pen-rived,  consists  in  heating  the  water  to  ebullition,  introducing  the  body  which  has  been 
weighed  in  the.  air  into  the  still  boiling  water,  which  is  then  allowed  to  cool  to  15-5°,  when  the 
second  weighing  is  performed. 


32 


DENSITY   AND    SPECIFIC    GRAVITY. 


Weight  of  sugar  in  air  ..... 
Weight  of  sugar  in  oil  of  turpentine 

Weight  of  equal  bulk  of  oil  of  turpentine    . 
87  :   100=217-5  :   250, 


400      grains. 
182-5       « 

217-5       " 


the  weight  of  an  equal  bulk  of  water ;  hence  the  specific  gravity  of  the 
sugar, — 

400 

==  1-6. 

250 

If  the  substance  to  be  examined  consists  of  small  pieces,  or  of  powder, 
then  the  method  first  described,  namely,  that  of  the  specific-gravity  bottle, 
can  alone  be  used. 

By  this  method  the  specific  gravities  of  metals  in  powder,  metallic  oxides, 
and  other  compounds,  and  salts  of  all  descriptions,  may  be  determined  with 
great  ease.  Oil  of  turpentine  may  be  used  with  most  soluble  salts.  The 
crystals  should  be  crushed  or  roughly  powdered  to  avoid  errors  arising 
from  cavities  in  their  substance. 

The  specific  gravity  of  a  solid  can  also  be  readily  found  by  immersing 
it  in  a  transparent  liquid,  the  density  of  which  has  been  so  adjusted  that 
the  solid  body  remains  indifferently  at  whatever  depth  it  may  be  placed. 
The  specific  gravity  of  the  liquid  must  now  be  determined,  and  it  will,  of 
course,  be  the  same  as  that  of  the  solid.  It  is  necessary  that  the  liquid 
chosen  for  this  experiment  do  not  dissolve  or  in  any  way  act  upon  the  solid. 
Solutions  of  mercuric  nitrate,  or  corrosive  sublimate,  can  be  used  for 
bodies  heavier  than  water,  while  certain  oils,  and  essences,  and  mixtures 
of  alcohol  and  water,  can  be  conveniently  employed  for  such  substances  as 
have  a  lower  specific  gravity  than  water.  This  method  is  not  only  adapted 
to  the  exact  determination  of  specific  gravities,  but  also  serves  in  many 
cases  as  a  means  of  readily  distinguishing  substances  much  resembling  one 
another.  Suppose,  for  instance,  a  solution  of  mercuric  nitrate  to  have  a 
specific  gravity  3;  a  red  amethyst  (2-67)  will  then  float  upon,  and  a  topaz 
of  the  same  color  (3-55)  will  sink  in  thi§  liquid. 

The  theorem  of  Archimedes  affords  the 
key  to  the  general  doctrine  of  the  equili- 
brium of  floating  bodies,  of  which  an 
application  is  made  in  the  common  hydro- 
meter,—  an  instrument  for  finding  the 
specific  gravities  of  liquids  in  a  very  easy 
and  expeditious  manner. 

When  a  solid  body  is  placed  upon  the 
surface  of  a  liquid  specifically  heavier 
than  itself,  it  sinks  down  until  it  displaces  a  quan- 
tity of  liquid  equal  to  its  own  weight,  at  which  point 
it  floats.  Thus,  in  the  case  of  a  substance  floating 
in  water,  whose  specific  weight  is  one  half  that  of 
the  liquid,  the  position  of  equilibrium  will  involve 
the  immersion  of  one  half  of  the  body,  inasmuch  as 
its  whole  weight  is  counterpoised  by  a  quantity  of 
water  equal  to  half  its  volume.  If  the  same  body 
were  put  into  a  liquid  of  one  half  the  specific  gravity 
of  water,  if  such  could  be  found,  it  would  then  sink 
beneath  the  surface,  and  remain  indifferently  in  any 
part.  A  floating  body  of  known  specific  gravity  may 

thus  be  used  as  an  indicator  of  the  specific  gravity  of  a  liquid.  In  this 
manner  little  glass  beads  (fig.  8)  of  known  specific  gravities  are  some- 
times employed  in  the  arts  to  ascertain  in  a  rude  manner  the  specific 


Fig.  8. 


Fig.  9. 


DENSITY   AND    SPECIFIC    GRAVITY. 


33 


gravity  of  liquids;  the  one  that  floats  indifferently  beneath  the  surface, 
without  either  sinking  or  rising,  has  of  course  the  same  specific  gravity  as 
the  liquid  itself;  this  is  pointed  out  by  the  number  marked  upon  the  bead. 

The  hydrometer  (fig.  9)  in  general  use  consists  of  a  floating  vessel  of 
thin  metal  or  glass,  having  a  weight  beneath  to  maintain  it  in  an  upright 
position,  an€  a  stem  above  bearing  a  divided  scale.  The  use  of  the  instru- 
ment is  very  simple.  The  liquid  to  be  tried  is  put  into  a  small  narrow 
jar,  and  the  instrument  floated  in  it.  It  is  obvious  that  the  denser  the 
liquid,  the  higher  will  the  hydrometer  float,  because  a  smaller  displacement 
of  liquid  will  counterbalance  its  weight.  For  the  same  reason,  in  a  liquid 
of  less  density,  it  sinks  deeper.  The  hydrometer  comes  to  rest  almost  im- 
mediately, and  then  the  mark  on  the  stem  at  the  fluid-level  may  be  read  off. 

Very  extensive  use  is  made  of  instruments  of  this  kind  in  the  arts ;  they 
sometimes  bear  different  names,  according  to  the  kind  of  liquid  for  which 
they  are  intended ;  but  the  principle  is  the  same  in  all.  The  graduation 
is  very  commonly  arbitrary,  two  or  three  different  scales  being  unfortu- 
nately used.  These  may  be  sometimes  reduced,  however,  to  the  true  num- 
bers expressing  the  specific  gravity  by  the  aid  of  tables  of  comparison 
drawn  up  for  the  purpose.  (See  APPENDIX.) 

Tables  are  likewise  used  to  reduce  the  readings  of  the  hydrometer  at 
any  temperature  to  those  of  the  normal  temperature. 

The  division  of  the  instrument  from  below,  upward,  into  100  parts,  is 
much  to  be  preferred  to  these  arbitrary  scales.  Half  of  these  divisions  must 
be  made  upon  the  stem.  The  100th  division  indicates  the  point  of  immer- 
sion in  distilled  water  at  15-5°  C.  (60°  Fahr.)  If  in  another  liquid  the 
instrument  sinks  less  deeply,  for  example  to  60,  then  60  volumes  of  this 
liquid  weigh  as  much  as  100  volumes  of  water.  Hence  the  weight  of  100 
volumes,  that  is,  the  specific  gravity,  is  ^  =  1-67.  By  this  arrangement 
of  the  scale,  it  is  evident  that  the  reduction  of  the  specific  gravity  is  so 
simple  that  no  tables  are  required. 

A  very  convenient  and  useful  instrument  in  the  shape  of  a  small  hydro- 
meter, for  taking  the  specific  gravity  of  urine,  has  been  put  into  the  hands 
of  the  physician  ;*  it  may  be  packed  into  a  pocket-case,  with  a  little  jar 
and  a  thermometer,  and  is  always  ready  for  use.f 

Fig.  10. 


Fin.  11. 


[*  The  graduation  of  the  urinometer  is  such  that  each  degree  represents  1-1000,  thus  giving 
tin-  ac-tual  specific  gravity  without  calculation,  for  the  number  of  degrees  on  the  scale  cut  by 
the  surface  of  the  liquid  when  this  instrument  is  at  rest,  added  to  1<HX),  will  represent  the  den- 
sity of  the  liquid.  If,  for  example,  the  surface  of  the  liquid  coincide  with  K5  on  the  scale,  the 
Kp.citie  gravity  will  l>e  1013,  about  the  average  density  of  healthy  urine.  —  R.  B.] 

[f  The  mode  of  determining  the  specific  gravity  of  a  liquid  by  means  of  a  solid  has  been  omitted 


34  DENSITY    AND    SPECIFIC    GRAVITY. 

The  determination  of  the  specific  gravity  of  gases  and  vapors  of  volatile 
liquids  is  a  problem  of  very  great  practical  importance  to  the  chemist:  the 
theory  of  the  operation  is  as  simple  as  when  liquids  themselves  are  con- 
cerned, but  the  processes  are  much  more  delicate,  and  involve  besides  cer- 
tain corrections  for  differences  of  temperature  and  pressure,  founded  on 
principles  yet  to  be  discussed.  It  will  be  proper  to  defer  the  considerations 
of  these  matters  for  the  present.  The  method  of  determining  the  specific 
gravity  of  a  gas  will  be  found  described  under  the  head  of  Oxygen,  and 
that  of  the  vapor  of  a  volatile  liquid  in  the  Introduction  to  Organic 
Chemistry. 

in  the  text.  It  results  from  the  theorem  of  Archimedes,  that  if  any  solid  be  immersed  in  water 
and  then  in  any  other  liquid,  the  loss  of  weight  sustained  in  each  case  will  give  the  relative 
weights  of  equal  bulks  of  the  liquids,  and  on  dividing  the  weight  of  the  liquid  by  the  weight 
of  the  water,  the  quotient  will  be  the  specific  gravity  of  the  liquid  experimented  on.  For  in- 
etancc,  Set  a  piece  of  glass  rod  (fig.  10)  be  suspended  from  the  balance  pan  and  exactly  counter- 
poised, then  immerse  it  in  water  and  restore  the  equipoise  by  weights  added  to  the  pan  to  which 
the  glass  is  suspended,  the  amount  will  give  the  loss  of  weight  by  immersion  or  the  weight  of  a 
bulk  of  water  equal  to  that  of  the  stopper.  Now  wipe  the  glass  dry,  and  having  removed 
the  additional  weights,  immerse  it  in  the  other  liquid,  and  restore  the  equipoise  as  before;  this 
latter  weight  is  the  weight  of  a  bulk  of  the  liquid  equal  to  that  of  the  water.  The  latter  divided 
by  the  former  gives  the  specific  gravity.  For  example : — 

The  glass  stopper  loses  by  immersion  in  water  171  grains. 

The  glass  stopper  loses  by  immersion  in  alcohol 143       " 

^|3  -  .836)  the  specific  gravity  required,  —  R.  B.] 


OF  THE  PHYSICAL  CONSTITUTION  OF  THE  ATMOS- 
PHERE AND  OF  GASES  IN  GENERAL. 


IT  requires  some  little  abstraction  of  mind  to  realize  completely  the  con- 
dition in  which  all  things  at  the  surface  of  the  earth  exist.     We  live  at 
the  bottom  of  an  immense  ocean  of  gaseous  matter,  which  envelops  every- 
thing, and  presses  upon  everything  with  a  force  which  appears,  at  first 
sight,  perfectly  incredible,  but  whose  actual  amount  admits  of  easy  proof. 

Gravity  being,  so  far  as  is  known,  common  to  all  matter,  it  is  natural  to 
expect  that  gases,  being  material  substances,  should  be  acted  upon  by  the 
earth's  attraction,  as  well  as  solids  and  liquids.  This  is  really  the  case, 
and  the  result  is  the  weight  or  pressure  of  the-  atmosphere,  which  is  noth- 
ing more  than  the  effect  of  the  attraction  of  the  earth  on  the  particles  of  air. 

Before  describing  the  leading  phenomena  of  the  atmospheric  pressure,  it 
is  necessary  to  notice  one  very  remarkable  feature  in  the  physical  consti- 
tution of  gases,  upon  which  depends  the  principle  of  an  extremely  valuable 
instrument,  the  air-pump. 

Gases  are  in  the  highest  degree  elastic;  the  volume  or  space  which  a  gas 
occupies  depends  upon  the  pressure  exerted  upon  it.  Let  the  reader  imagine 
a  cylinder,  a,  closed  at  the  bottom,  in  which  Fig.  12. 

moves  a  piston,  air-tight,  so  that  no  air  can  es- 
cape between  the  piston  and  the  cylinder.  Sup- 
pose now  the  piston  be  pressed  downward  with 
a  certain  force ;  the  air  beneath  it  will  be  com- 
pressed into  a  smaller  bulk,  the  amount  of  this 
compression  depending  on  the  force  applied;  if  c 
the  power  be  sufficient,  the  bulk  of  the  gas  may 
be  thus  diminished  to  one  hundredth  part  or  less. 
When  the  pressure  is  removed,  the  elasticity  or 
tension,  as  it  is  called,  of  the  included  air  or  gas, 
will  immediately  force  up  the  piston  until  it  ar- 
rives at  its  first  position. 

Again,  take  fig.  12,  b,  and  suppose  the  piston 
to  stand  about  the  middle  of  the  cylinder,having 
air  beneath  in  its  usual  state.     If  the  piston  be|| 
now  drawn  upward,  the  air  below  will  expand, 
so  as  to  fill  completely  the  increased  space,  and 

this  to  an  apparently  unlimited  extent.  A  volume  of  air,  which,  under 
ordinary  circumstances,  occupies  the  bulk  of  a  cubic  inch,  might,  by  the 
removal  of  the  pressure  upon  it,  be  made  to  expand  to  the  capacity  of  a 
whole  room,  while  a  renewal  of  the  former  pressure  would  be  attended  by 
a  shrinking  down  of  the  air  to  its  former  bulk.  The  smallest  portion  of 
gas  introduced  into  a  large  exhausted  vessel  becomes  at  once  diffused 
through  the  whole  space,  an  equal  quantity  being  present  in  every  part ; 
the  vessel  is  full,  although  the  gas  is  in  a  state  of  extreme  tenuity.  This 
power  of  expansion  which  air  possesses  may  have,  and  probably  has,  in 
reality,  a  limit;  but  the  limit  is  never  reached  in  practice.  We  are  quite 
safe  in  the  assumption  that  for  all  purposes  of  experiment,  however  refined, 
air  is  perfectly  elastic. 

It  is  usual  to  assign  a  reason  for  this  indefinite  expansibility  by  ascribing 

35 


36 


PHYSICAL    CONSTITUTION 


to  the  particles  of  material  bodies,  when  a  in  gaseous  state,  a  self-repulsive 
agency.     This  statement  is  commonly  made  somewhat  in  this  manner : 

Fig.  13. 


matter  is  under  the  influence  of  two  opposite  forces,  one  of  which  tends  to 
draw  the  particles  together,  the  other  to  separate  them.  By  the  prepon- 
derance of  one  or  other  of  these  forces,  we  have  the  three  states  called 
solid,  liquid,  and  gaseous.  When  the  particles  of  matter,  in  consequence 
of  the  direction  and  strength  of  their  mutual  attractions,  possess  only  a 
very  slight  power  of  motion,  a  solid  substance  results;  when  the  forces 
are  nearly  balanced,  we  have  a  liquid,  the  particles  of  which  in  the  interior 
of  the  mass  are  free  to  move,  but  yet  to  a  certain  extent  are  held  together ; 
and  lastly,  when  the  attractive  power  seems  to  be  completely  overcome  by 
its  antagonist,  we  have  a  gas  or  vapor. 

Various  names  are  applied  to  these  forces,  and  various  ideas  entertained 

Fig.  14. 


OF    THE    ATMOSPHERE. 


37 


concerning  them:  the  attractive  forces  bear  the  name  of  cohesion  when  they 
are  exerted  between  particles  of  matter  separated  by  an  immeasurably 
small  interval,  and  gravitation  when  the  distance  is  great.  The  repulsive 
principle  is  often  thought  to  be  identical  with  the  principle  of  heat.  We 
shall  return  to  this  subject  in  discussing  the  nature  of  heat.  (See  page  77.) 

The  ordinary  air-pump,  shown  in  section  in  fig.  13,  consists  essentially 
of  a  metallic  cylinder,  in  which  moves  a  tightly  fitting  piston,  by  the  aid 
of  its  rod.  The  bottom  of  the  cylinder  communicates  with  the  vessel  to  be 
exhausted,  and  is  furnished  with  a  valve  opening  upward.  A  similar 
valve,  also  opening  upward,  is  fitted  to  the  piston :  these  valves  are  made 
with  slips  of  oiled  silk.  When  the  piston  is  raised  from  the  bottom  of  the 
cylinder,  the  space  left  beneath  it  must  be  void  of  air,  since  the  piston- 
valve  opens  only  in  one  direction;  the  air  within  the  receiver  having  on 
that  side  nothing  to  oppose  its  elastic  power  but  the  weight  of  the  little 
valve,  lifts  the  latter,  and  escapes  into  the  cylinder.  So  soon  as  the  piston 
begins  to  descend,  the  lower  valve  closes,  by  its  own  weight,  or  by  the 
transmitted  pressure  from  above,  and  communication  with  the  receiver  is 
cut  off.  As  the  descent  of  the  piston  continues,  the  air  inclosed  in  the 
cylinder  becomes  compressed,  its  elasticity  is  increased,  and  at  length  it 
forces  open  the  upper  valve,  and  escapes  into  the  atmosphere.  In  this 
manner,  a  cylinder  full  of  air  is  at  every  stroke  of  the  pump  removed  from 
the  receiver.  During  the  descent  of  the  piston,  the  upper  valve  remains 
open,  and  the  lower  closed,  and  the  reverse  during  the  opposite  movement. 

In  practice,  it  is  very  convenient  to  have  two  such  barrels  or  cylinders, 
arranged  side  by  side,  the  piston-rods  of  which  are  formed  into  racks, 
having  a  pinion,  or  small-toothed  wheel,  between  them,  moved  by  a  winch. 
By  this  contrivance  the  operation  of  exhaustion  is  much  facilitated  and 
the  labor  lessened.  The  arrangement  is  shown  in  fig.  14,  on  the  preceding 
page. 

A  simpler  form  of  air-pump  is  thus  constructed:  the  cylinder,  which 
may  be  of  large  dimensions,  is  furnished  with  an  accurately  fitted  solid 
piston,  the  rod  of  which  moves,  air-tight,  through  a  contrivance  called  a 
stuffing-box,  at  the  top  of  the  cylinder,  where  also  the  only  valve  essential 
to  the  apparatus  is  to  be  found  :  the  latter  is  a  solid  conical  plug  of  metal, 
shown  at  a  in  the  figure,  kept  tight  by  the  oil  contained  in 
the  chamber  into  which  it  opens.  The  communication  with 
the  vessel  to  be  exhausted  is  made  by  a  tube  which  enters 
th,e  cylinder  a  little  above  the  bottom.  The  action  is  the 
following:  let  the  piston  be  supposed  in  the  act  of  rising 
from  the  bottom  of  the  cylinder:  as  soon  as  it  passes  the 
mouth  of  the  tube  t,  all  communication  is  stopped  between 
the  air  above  the  piston  and  the  vessel  to  be  exhausted ;  the 
inclosed  air  suffers  compression  until  it  acquires  sufficient 
elasticity  to  lift  the  metal  valve  and  escape  by  bubbling 
through  the  oil.  When  the  piston  makes  its  descent,  and , 
this  valve  closes,  a  vacuum  is  left  in  the  upper  part  of  the 
cylinder,  into  which  the  air  in  the  receiver  rushes  so  soon 
as  the  piston  has  passed  below  the  orifice  of  the  connecting 
tube. 

In  the  silk-valved  air-pump,  exhaustion  ceases  when  the 
elasticity  of  the  air  in  the  receiver  becomes  too  feeble  to 
raise  the  valve :  in  that  last  described  the  exhaustion  may, 
on  the  contrary,  be  carried  to  an  indefinite  extent,  without, 
however,  under  the  most  favorable  circumstances,  be- 
coming complete.  The  conical  valve  is  made  to  project 
a  little  below  the  cover  of  the  cylinder,  so  as  to  be  forced 
up  by  the  piston  when  the  latter  reaches  the  top  of  the 


Fig.  15. 


38 


PHYSICAL    CONSTITUTION 


cylinder;  the  oil  then  enters  and  displaces  any  air  that  may  be  lurking  in 
the  cavity. 

It  is  a  great  improvement  to  the  machine  to  supply  the  piston  with  a 
relief-valve  opening  upward;    this  may  also  be  of  metal,   and    contained 

within  the  body  of  the  piston.     Its  use  is 
F'9- 16.  to   avoid  the  momentary  condensation   of 

the  air  in  the  receiver  when  the  piston  de- 
scends. The  pump  is  worked  by  a  lever  in 
the  manner  represented  in  figure  16. 

The  air-pump  may  be  used  for  condens- 
ing instead  of  for  rarefying  the  air.  If  the 
cylinder  (fig.  15)  is  filled  with  air  from  the 
opening  (t),  it  may  be  forced  by  the  rise  of 
the  piston  through  the  valve  (a)  into  a 
communicating  chamber,  and  this  operation 
may  be  frequently  repeated. 

To  return  to  the  atmosphere.  Air  pos- 
sesses weight:  a  light  flask  or  globe  of 
glass,  furnished  with  a  stopcock  and  ex- 
hausted by  the  air-pump,  weighs  consider- 
ably less  than  when  full  of  air.  If  the 
capacity  of  the  vessel  be  equal  to  100 
cubic  inches,  this  difference  may  amount 
to  nearly  30  grains. 

The  mere  fact  of  the  pressure  of  the  at- 
mosphere may  be  demonstrated  by  securely 
tying  a  piece  of  bladder  over  the  mouth  of 
an  open  glass  receiver,  and  then  exhausting 
the  air  from  beneath  it ;  the  bladder  will 
become  more  and  more  concave,  until  it 
suddenly  breaks.  A  thin  square  glass  bot- 
tle, or  a  large  air-tight  tin  box,  may  be 
crushed  by  withdrawing  the  support  of  the 
air  in  the  inside.  Steam-boilers  have  been 
often  destroyed  in  this  manner  by  collapse, 
in  consequence  of  the  accidental  formation 
of  a  partial  vacuum  within. 

After  what  has  been  said  on  the  subject  of 
fluid  pressure,  it  will  scarcely  be  necessary 
to  observe  that  the  law  of  equality  of  pres- 
sure in  all  directions  also  holds  good  in  the 
'  case  of  the  atmosphere.  The  perfect  mo- 
bility of  the  particles  of  air  permits  the 
transmission  of  the  force  generated  by 
their  gravity.  The  sides  and  bottom  of 
an  exhausted  vessel  are  pressed  upon  with 
as  much  force  as  the  top. 

If  a  glass  tube  of  considerable  length 

could  be  perfectly  exhausted  of  air,  and  then  held  in  an  upright  position, 
with  one  of  its  ends  dipping  into  a  vessel  of  liquid,  the  latter,  on  being 
allowed  access  to  the  tube,  would  rise  in  its  interior  until  the  weight  of 
the  column  balanced  the  pressure  of  the  air  upon  the  surface  of  the  liquid. 
Now,  if  the  density  of  this  liquid  were  known,  and  the  height  and  area  of 
the  column  measured,  means  would  be  furnished  for  exactly  estimating  the 
amount  of  pressure  exerted  by  the  atmosphere.  Such  an  instrument  is  the 
barometer:  a  straight  glass  tube  is  taken,  about  36  inches  in  length,  and 
sealed  by  the  blowpipe  flame  at  one  extremity ;  it  is  then  filled  with  clean, 


OF    THE    ATMOSPHERE. 


39 


Fig.  17. 


dry  mercury,  care  being  taken  to  displace  all  air-bubbles,  the  open  end 
stopped  with  a  finger,  and  the  tube  inverted  in  the  basin  of  mercury.  On 
removing  the  finger,  the  fluid  sinks  away  from  the  top  of  the  tube,  until  it 
stands  at  the  height  of  about  30  inches  above  the  level  of  that  in  the  basin. 
Here  it  remains  supported  by,  and  balancing  the  atmospheric  pressure, 
the  space  above  the  mercury  in  the  tube  being  of  necessity  empty. 

The  pressure  of  the  atmosphere  is  thus  seen  to  be  capable 
of  sustaining  a  column  of  mercury  30  inches  in  height,  or 
thereabouts:  now  such  a  column,  having  an  area  of  one  inch, 
weighs  between  14  and  15  pounds:  consequently  such  must 
be  the  amount  of  the  pressure  exerted  upon  every  square  inch 
of  the  surface  of  the  earth,  and  of  the  objects  situated  thereon, 
at  least  near  the  level  of  the  sea.  This  enormous  force  is 
borne  without  inconvenience  by  the  animal  frame,  by  reason 
of  its  perfect  uniformity  in  every  direction;  and  it  may  be 
doubled,  or  even  tripled,  without  injury. 

A  barometer  may  be  constructed  with  other  liquids  besides 
mercury ;  but  as  the  height  of  the  column  must  always  bear 
an  inverse  proportion  to  the  density  of  the  liquid,  the  length 
of  tube  required  will  be  often  considerable;  in  the  case  of 
water  it  will  exceed  33  feet.  It  is  seldom  that  any  other  liquid 
than  mercury  is  employed  in  the  construction  of  this  instru- 
ment. The  Royal  Society  of  London  possessed  a  water  barom- 
eter at  their  apartments  at  Somerset  House.  Its  construction 
was  attended  with  great  difficulties,  and  it  was  found  impos- 
sible to  keep  it  in  repair. 

It  will  now  be  necessary  to  consider  a  most  important  law 
which  connects  the  volume  occupied  by  a  gas  with  the  pressure 
made  upon  it,  and  is  thus  expressed: 

The  volume  of  gas  is  inversely  as  the  pressure ;  the  density 
and  elastic  force  are  directly  as  the  pressure,  and  inversely 
as  the  volume. 

For  instance,  100  cubic  inches  of  gas  under  a  pressure  of 
30  inches  of  mercury  would  expand  to  200  cubic  inches  were 
the  pressure  reduced  to  one  half,  and  shrink,  on  the  contrary, 
to  50  cubic  inches  if  the  original  pressure  were  doubled.  The 
change  of  density  must  necessarily  be  in  the  inverse  proportion 
to -that  of  the  volume,  and  the  elastic  force  follows  the  same 
rule. 

This,  which  is  usually  called  the  law  of  Mariotte,  though 
really  discovered  by  Boyle  (1661),  is  easily  demonstrable  by 
direct  experiment.  A  glass  tube,  about  7  feet  in  length,  is 
closed  at  one  end,  and  bent  into  the  form  represented  in  fig.  18,  the  open 
limb  of  the  syphon  being  the  longer.  It  is  next  attached  to  a  board  fur- 
nished with  a  movable  scale  of  inches,  and  enough  mercury  is  introduced 
to  fill  the  bend,  the  level  being  evenly  adjusted,  and  marked  upon  the 
board.  Mercury  is  now  poured  into  the  tube  until  it  is  found  that  the 
inclosed  air  has  been  reduced  to  one  half  of  its  former  volume ;  and  on 
applying  the  scale,  it  will  be  found  that  the  level  of  the  mercury  in  the 
open  part  of  the  tube  stands  very  nearly  30  inches  above  that  in  the  closed 
portion.  The  pressure  of  an  additionnl  "atmosphere"  has  consequently 
reduced  the  bulk  of  the  contained  air  to  one  half.  If  the  experiment  be 
still  continued  until  the  volume  of  air  is  reduced  to  a  third,  it  will  be 
found  that  the  column  measures  60  inches,  and  so  in  like  proportion  as 
far  as  the  experiment  is  carried. 

The  above  instrument  is  better  adapted  for  illustration  of  the  principle 
than  for  furnishing  rigorous  proof  of  the  law;  this  has,  however,  been 


40 


PHYSICAL    CONSTITUTION 


done.  MM.  Arago  and  Dulong  published,  in  the  year  1830,  an  account  of 
certain  experiments  made  by  them  in  Paris,  in  which  the  law  in  question 
had  been  verified  to  the  extent  of  27  atmospheres.  And  with  rarefied  air, 
of  whatever  degree  of  rarefaction,  the  law  has  been  found  true. 

All   gases    are    alike    subject    to   this  law,   and    all 
Fig.  18.  vapors    of    volatile    liquids,    when  remote  from  their 

points  of  liquefaction.*  It  is  a  matter  of  the  greatest 
importance  in  practical  chemistry,  since  it  gives  the 
means  of  making  corrections  for  pressure,  or  deter- 
mining by  calculation  the  change  of  volume  which  a 
gas  would  suffer  by  any  given  change  of  external 
pressure. 

Let  it  be  required,  for  example,  to  solve  the  follow- 
ing problem:  We  have  100  cubic  inches  of  gas  in  a 
graduated  jar,  the  barometer  standing  at  29  inches; 
how  many  cubic  inches  will  it  occupy  when  the  column 
rises  to  80  inches? — Now  the  volume  must  be  inversely 
as  the  pressure:  consequently  a  change  of  pressure 
in  the  proportion  of  29  to  30  must  be  accompanied  by 
a  change  of  volume  in  the  proportion  of  30  to  29,  the 
30  cubic  inches  of  gas  contracting  to  29  cubic  inches 
under  the  conditions  imagined.  Hence  the  answer: 

30  :  29  =  100  :  96-67  cubic  inches. 

The  reverse  of  the  operation  will  be  obvious.  The 
pupil  will  do  well  to  familiarize  himself  with  the  sim- 
ple calculations  of  correction  for  pressure. 

From  what  has  been  said  respecting  the  easy  com- 
pressibility of  gases,  it  will  be  at  once  seen  that  the 
atmosphere  cannot  have  the  same  density,  and  cannot 
exert  equal  pressures  at  different  elevations  above  the 
sea-level,  but  that,  on  the  contrary,  these  must  dimin- 
ish with  the  altitude,  and  very  rapidly.  The  lower 
strata  of  air  have  to  bear  the  weight  of  those  above 
them;  they  become,  in  consequence,  denser  and  more 
compressed  than  the  upper  portions.  The  following 
table,  which  is  taken  from  Prof.  Graham's  work, 
shows  in  a  very  simple  manner  the  rule  followed  in 
this  respect: 


Height  above  the 
sea,  in  miles. 

0 

2-705 

5-41       . 

8-115 
10-82       . 
13-525 
16-23 


Volume  of  air. 
1      . 
2 
.       4    . 

8 

.     16     . 
32' 
64     , 


Height  of  barometer, 
in  inches. 

.     30 
15 
.       7-5 

3-75 

.       1-875 
0-9375 
0-46875 


The  numbers  in  the  first  column  form  an  arithmetical  series,  by  the  con- 
stant addition  of  2-705;  those  in  the  second  column  an  increasing  geomet- 
rical series,  each  being  double  its  predecessor;  and  those  in  the  third,  a 
decreasing  geometrical  series,  in  which  each  number  is  the  half  of  that 
standing  above  it. 

*  Near  the  liquefying  point  the  law  no  longer  holds ;  the  volume  diminishes  more  rapidly 
than  the  theory  indicates,  a  smaller  amount  of  pressure  being  then  sufficient. 


OF    THE    ATMOSPHERE. 


41 


In  ascending  into  the  air  in  a  balloon,  these  effects  are  well  observed; 
the  expansion  of  the  gas  within  the  machine,  and  the  fall  of  the  mercury 
in  the  barometer,  soon  indicate  to  the  voyager  the  fact  of  his  having  left 
below  him  a  considerable  part  of  the  whole  atmosphere. 

The  invention  of  the  barometer,  which  took  place  in  the 
year  1643,  by  Torricelli,  a  pupil  of  the  celebrated  Galileo,  Fig.19. 
speedily  led  to  the  observation  that  the  atmospheric  pressure 
at  the  same  level  is  not  constant,  but  possesses,  on  the  con- 
trary, a  small  range  of  variation,  seldom  exceeding  in  Europe 
2  or  2-5  inches,  and  within  the  tropics  usually  confined  within 
much  narrower  limits.  Two  kinds  of  variations  are  distin- 
guished: regular  or  horary,  and  irregular  or  accidental.  It 
has  been  observed  that  in  Europe  the  height  of  the  barometer 
is  greatest  at  two  periods  in  the  twenty-four  hours,  depending 
upon  the  season.  In  winter,  the  first  maximum  takes  place 
about  9  A.  M.,  the  first  minimum  at  3  p.  M.,  after  which  the 
mercury  again  rises  and  attains  its  greatest  elevation  at  9  in 
the  evening:  in  summer  these  hours  of  the  aerial  tides  are 
somewhat  altered.  The  accidental  variations  are  much  greater 
in  amount,  and  render  it  extremely  difficult  to  trace  the  regu- 
lar changes  above  mentioned. 

The  barometer  is  applied  with  great  advantage  to  the  mea- 
surement of  accessible  heights,  and  it  is  also  in  daily  use  for 
foretelling  the  state  of  the  weather ;  its  indications  are  in  this 
respect  extremely  deceptive,  except  in  the  case  of  sudden  and 
violent  storms,  which  are  almost  always  preceded  by  a  rapid 
fall  in  the  mercurial  column.  It  is  often  extremely  useful  in 
this  respect  at  sea. 

To  the  practical  chemist  a  moderately  good  barometer  is  an 
indispensable  article,  since  in  all  experiments  in  which  volumes 
of  gases  are  to  be  estimated,  an  account  must  be  taken  of  the 
;itniospheric  pressure.  Fig.  19  represents  a  very  convenient 
and  economical  syphon-barometer  for  this  purpose.  A  piece 
of  new  and  stout  tube,  of  about  one  third  of  an  inch  in  diam- 
eter, is  procured  at  the  glass-house,  sealed  at  one  extremity, 
and  bent  into  the  syphon-form,  as  represented.  Pure  and 
warm  mercury  is  next  introduced  by  successive  portions  until 
the  tube  is  completely  filled,  and  the  latter  being  held  in  an 
upright  position,  the  level  of  the  metal  in  the  lower  and  open 
limb  is  conveniently  adjusted  by  displacing  a  portion  with  a 
stick  or  glass  rod.  The  barometer  is,  lastly,  attached  to  a 
board,  and  furnished  with  a  long  scale,  made  to  slide,  which 
may  be  of  box-wood,  with  a  slip  of  ivory  at  each  end.  When 
an  observation  is  to  be  taken,  the  lower  extremity  or  zero  of 
the  scale  is  placed  exactly  even  with  the  mercury  in  the  short 
limb,  and  then  the  height  of  the  column  is  at  once  read  off. 
4* 


42 


HEAT. 


HEAT. 

IT  will  be  convenient  to  consider  the  subject  of  heat  under  several  sec- 
tions, and  in  the  following  order : — 

1.  Expansion  of  bodies,  or  effects  of  variations  of  temperature  in  alter- 

ing their  dimensions. 

2.  Conduction,  or  transmission  of  heat. 

3.  Change  of  state. 

4.  Specific  heat. 

5.  Sources  of  heat. 

6.  Dynamical  theory  of  heat. 

The  phenomena  of  radiation  must  be  deferred  until  a  sketch  has  been 
given  of  the  science  of  light. 

EXPANSION. 

If  a  bar  of  metal  of  such  magnitude  as  to  fit  accurately  to  a  gauge,  when 
cold,  be  heated  considerably,  and  again  applied  to  the  gauge,  it  will  be  found 
to  have  become  enlarged  in  all  its  dimensions.  When  cold,  it  will  once 
more  enter  the  gauge. 

Again,  if  a  quantity  of  liquid  contained  in  a  glass  bulb,  furnished  with 
a  narrow  neck,  be  plunged  into  hot  water,  or  exposed  to  any  other  source 


Fig.  20. 


Fig.  21. 


Fig.  22. 


of  heat,  the  liquid  will  mount  in  the  stem,  showing  that  its  volume  has 
been  increased.  The  bulb,  however,  has  likewise  expanded  by  the  heat, 
and  its  capacity  has  consequently  been  augmented.  The  rise  of  the  liquid 
in  the  tube,  therefore,  denotes  the  difference  between  these  two  expansions. 

Or,  if  a  portion  of  air  be  confined  in  any  vessel,  the  application  of  a 
slight  degree  of  heat  will  suffice  to  make  it  occupy  a  space  sensibly  larger. 

This  most  general  of  all  the  effects  of  heat  furnishes  in  the  outset  a 
principle,  by  the  aid  of  which  an  instrument  can  be  constructed  capable 
of  taking  cognizance  of  changes  of  temperature  in  a  manner  equally  ac- 
curate and  convenient :  such  an  instrument  is  the  thermometer. 

A  capillary  glass  tube  is  chosen,  of  uniform  diameter:  one  extremity  is 
closed  and  expanded  into  a  bulb,  by  the  aid  of  the  blowpipe  flame,  and  the 


HEAT. 


43 


Fig.  23. 


other  somewhat  drawn  out,  and  left  open.  The  bulb  is  now  cautiously 
heated  by  a  spirit-lamp,  and  the  open  extremity  plunged  into  a  vessel  of 
mercury,  a  portion  of  which  rises  into  the  bulb  when  the  latter  cools, 
replacing  the  air  which  had  been  expanded  and  driven  out  by  the  heat. 
By  again  applying  the  flame,  and  causing  this  mercury  to  boil,  the  remain- 
der of  the  air  is  easily  expelled,  and  the  whole  space  tilled  with  mercurial 
vapor.  The  open  end  of  the  tube  must  now  be  immediately  plunged  into 
the  vessel  filled  with  mercury ;  as  the  metallic  vapors  condense,  the  pres- 
sure of  the  external  air  forces  the  liquid  metal  into  the  instrument,  until 
finally  the  tube  is  completely  filled  with  piercury.  The  thermometer  thus 
filled  is  now  to  be  heated  until  so  much  mercury  has  been  driven  out  by 
the  expansion  of  the  remainder,  that  its  level  in  the  tube  shall  stand  at 
common  temperatures  at  the  point  required.  This  being  satisfactorily 
adjusted,  the  heat  is  once  more  applied,  until  the  column  rises  quite  to  the 
top;  and  then  the  extremity  of  the  tube  is  hermetically 
sealed  by  the  blowpipe.  The  retraction  of  the  mercury 
on  cooling  now  leaves  an  empty  space,  which  is  essen- 
tial to  the  perfection  of  the  instrument. 

The  thermometer  has  yet  to  be  graduated;  and  to 
make  its  indications  comparable  with  those  of  other 
instruments,  a  scale,  having  at  the  least  two  fixed 
points,  must  be  adapted  to  it- 
It  has  been  observed,  that  the  temperature  of  melting 
ice,  that  is  to  say,  of  a  mixture  of  ice  and  water,  is 
always  constant;  a  thermometer,  already  graduated, 
plunged  into  s^uch  a  mixture,  always  marks  the  same 
degree  of  temperature,  and  a  simple  tube  filled  in  the 
manner  described  and  so  treated,  exhibits  the  same 
effect  in  the  unchanged  height  of  the  little  mercurial 
column,  when  tried  from  day  to  day.  The  freezing- 
point  of  water,  or  melting-point  of  ice,  constitutes  then 
one  of  the  invariable  temperatures  demanded. 

Another  is  to  be  found  in  the  boiling-point  of  water,  or,  more  accurately, 
in  the  temperature  of  steam  which  rises  from  boiling  water.  In  order  to 
give  this  temperature,  which  remains  perfectly  constant  whilst  the  baro- 
metric pressure  is  constant,  to  the  mercury  of  the  thermometer,  distilled 
water  is  made  to  boil  in  a  glass  vessel  with  a  long  neck,  when  the  pressure 
is  at  30  inches  (fig.  23).  The  thermometer  is  then  so  placed  that  all  the 
mercury  is  surrounded  with  steam.  It  quickly  rises  to  a  fixed  point,  and 
there  it  remains  as  long  as  the  water  boils,  and  the  height  of  the  barometer 
is  unchanged. 

The  tube  having  been  carefully  marked  with  a  file  at  these  two  points,  it 
remains  to  divide  the  interval  into  degrees:  this  division  is  entirely  arbi- 
trary. The  scale  now  most  generally  employed  is  the  Centigrade,  in  which 
the  space  is  divided  into  100  parts,  the  zero  being  placed  at  the  freezing- 
point  of  water.  The  scale  is  continued  above  and  below  these  points, 
numbers  below  0  being  distinguished  by  the  negative  sign. 

In  England  the  division  of  Fahrenheit  is  still  in  use:  the  above-mentioned 
space  is  divided  into  180  degrees;  but  the  zero,  instead  of  starting  from 
the  freezing-point  of  water,  is  placed  32  degrees  below  it,  so  that  the  tem- 
perature of  ebullition  is  expressed  by  212°. 

The  plan  of  Reaumur  is  nearly  confined  to  a  few  places  in  the  north  of 
Germany  and  to  Russia:  in  this  scale  the  freezing-point  of  water  is  made 
0°,  and  the  boiling-point  80°. 

It  is  unfortunate  that  a  uniform  system  has  not  been  generally  adopted 
in  graduating  thermometers:  tliis  would  render  unnecessary  the  labor 
which  now  so  frequently  has  to  be  performed  of  translating  the  language 


44 


HEAT. 


of  one  scale  into  that  of  another.  To  effect  this,  presents,  however,  no 
great  difficulty.  Let  it  be  required,  for  example,  to  know  the  degree  of 
Fahrenheit's  scale  which  corresponds  to  60°  C. 


Consequently, 


100°  C  —  180°  F,  or  5°  C  =  9°  F. 
5  :  9  =  60  :  108. 


But  then,  as  Fahrenheit's  scale  commences  with  32°  instead  of  0°,  that 
number  must  be  added  to  the  result,  making  60°  C  =  140°  F. 

The  rule  then  will  be  the  following :  —  To  convert  Centigrade  degrees 
into  Fahrenheit  degrees,  multiply  by  9,  divide  the  product  by  5,  and  add 
32;  to  convert  Fahrenheit  degrees  into  Centigrade  degrees,  subtract  32, 
multiply  by  5,  and  divide  by  9. 

The  reduction  of  negative  degrees,  or  those  below  zero  of  one  scale  into 
those  of  another  scale,  is  effected  in  the  same  way.  For  example,  to  con- 
vert—  15°  C.  into  degrees  of  Fahrenheit  — 

9 

We  have  — 15  X  —  +  32  =  —  27  +  32  =  +  5  F. 
5 

In  this  work,  temperatures  will  always  be  given  in  Centigrade  degrees, 
unless  the  contrary  is  expressly  stated. 

Mercury  is  usually  chosen  for  making  thermometers,  on  account  of  its 
regularity  of  expansion  within  certain  limits,  and  because  it  is  easy  to 
have  the  scale  of  great  extent,  from  the  large  interval  between  the  freezing 
and  boiling  points  of  the  metal.  Other  substances  are  sometimes  used; 
alcohol  is  employed  for  estimating  very  low  temperatures,  because  this 
liquid  has  not  been  frozen  even  at  the  lowest  degree  of  cold  which  has  been 
artificially  produced. 

Air-thermometers  are  also  used  for  some  few  particular  purposes;  indeed, 
the  first  thermometer  ever  made  was  of  this  kind.  There  are  two  modifica- 
tions of  this  instrument:  in  the  first,  the  liquid  into  which  the  tube  dips  is 
open  to  the  air;  and  in  the  second,  shown  in  fig.  24,  the  atmosphere  is 
completely  excluded.  The  effects  of  expansion  are  in  the  one  case  compli- 
cated with  those  arising  from  changes  of  pressure,  and  in  the  other  cease 
to  be  visible  at  all  when  the  ivhole  instrument  is  subjected  to  alterations  of 
temperature,  because  the  air  in  the  upper  and  lower  reservoir  being  equally 
affected  by  such  changes,  no  alteration  in  the  height  of  the  fluid  column 


Fig.  24. 

Q 


Fig.  25. 


HEAT.  45 

can  occur.  Accordingly,  such  instruments  are  called  differential  thermom- 
eters, since  they  serve  to  measure  differences  of  temperature  between  the 
two  portions  of  air,  while  changes  affecting  both  alike  are  not  indicated. 
Fig.  25  shows  another  form  of  the  same  instrument. 

The  air-thermometer  may  be  employed  for  measuring  all  temperatures 
from  the  lowest  to  the  highest;  M.  Pouillet  has  described  one  by  which  the 
heat  of  an  air-furnace  could  be  measured.  The  reservoir  of  this  instru- 
ment is  of  platinum,  and  it  is  connected  with  a  piece  of  apparatus  by 
which  the  increase  of  volume  experienced  by  the  included  air  is  determined. 

An  excellent  air-thermometer  has  been  constructed  and  used  by  Rudberg, 
and  more  recently  by  Magnus  and  Regnault,  for  measuring  the  expansion 
of  the  air.  Its  construction  depends  on  the  law,  that  when  air  is  heated 
and  hindered  from  expanding,  its  tension  increases  in  the  same  proportion 
in  which  it  would  have  increased  in  volume  if  permitted  to  expand. 

All  bodies  are  enlarged  in  their  dimensions  by  the  application  of  heat, 
and  reduced  by  its  abstraction,  or,  in  other  words,  contract  on  being  artifi- 
cially cooled:  this  effect  takes  place  to  a  comparatively  small  extent  with 
solids,  to  a  larger  amount  in  liquids,  and  most  of  all  in  the  case  of  gases. 

Each  solid  and  liquid  has  a  rate  of  expansion  peculiar  to  itself;  gases, 
on  the  contrary,  expand  nearly  alike  for  the  same  increase  of  heat. 

Expansion  of  Solids. — The  difference  of  expansibility  among  solids  is  very 
easily  illustrated  by  the  following  arrangement:  a  thin,  straight  bar  of  iron 
is  firmly  fixed,  by  numerous  rivets,  to  a  similar  bar  of  brass:  so  long  as 
the  temperature  at  which  the  two  metals  were  united  remains  unchanged, 
the  compound  bar  preserves  its  straight  figure ;  but  any  alteration  of  tem- 
perature gives  rise  to  a  corresponding  curvature.  Brass  is  more  dilatable 
than  iron;  if  the  bar  be  heated,  therefore,  the  former  expands  more  than 
the  latter,  and  forces  the  straight  bar  into  a  curve,  whose  convex  side  is 
the  brass ;  if  it  be  artificially  cooled,  the  brass  contracts  more  than  the 
iron,  and  the  reverse  of  this  effect  is  produced. 

Fig.  26. 


This  fact  has  received  a  most  valuable  application.  It  is  not  necessary 
to  insist  on  the  importance  of  possessing  instruments  for  the  accurate  mea- 
surement of  time;  such  are  absolutely  indispensable  to  the  successful 
cultivation  of  astronomical  science,  and  not  less  useful  to  the  navigator, 
from  the  assistance  they  give  him  in  finding  the  longitude  at  sea.  For  a 
long  time,  notwithstanding  the  perfection  of  finish  and  adjustment  be- 
stowed upon  clocks  and  watches,  an  apparently  insurmountable  obstacle 
presented  itself  to  their  uniform  and  regular  movement:  this  obstacle  was 
the  change  of  dimensions  to  which  the  regulating  parts  of  the  machine 
were  subject  by  alterations  of  temperature.  A  clock  may  be  defined  as  an 
instrument  for  registering  the  number  of  beats  made  by  a  pendulum :  now 
the  time  of  oscillation  of  a  pendulum  depends  principally  upon  its  length; 
any  alteration  in  this  condition  will  seriously  affect  the  rate  of  the  clock. 
The  material  of  which  the  rod  of  the  pendulum  is  composed  is  subject  to 
expansion  and  contraction  by  changes  of  temperature ;  so  that  a  pendulum 


HEAT. 


adjusted  to  vibrate  seconds  at  15-5°  would  go  too  slow  if  the  temperature 
rose  to  20°,  from  its  becoming  longer,  and  too  fast  if  the  temperature  fell 
to  10°,  from  the  opposite  cause. 

This  great  difficulty  has  been  overcome  by  making  the  rod  of  a  number 
of  bars  of  iron  and  brass,  or  iron  and  zinc,  metals  whose  rates  of  expan- 
sion are  different,  and  arranging  these  bars  in  such  a  manner  that  the 
expansion  in  one  direction  of  the  iron  shall  be  exactly  compensated  by 
that  in  the  opposite  direction  of  the  brass  or  zinc,  it  is  possible  to  maintain 
under  all  circumstances  of  temperature  an  invariable  distance  between  the 
points  of  suspension  and  of  oscillation.  This  is  often  called  the  gridiron 
pendulum;  fig.  27  will  clearly  illustrate  its  principle;  the  shaded  bars  are 
supposed  to  be  iron  and  the  others  zinc. 


Fig.  27. 


Fig.  28. 


Fig.  29. 


A  still  simpler  compensation-pendulum  is  thus  constructed.  The  weight 
or  bob,  instead  of  being  made  of  a  disc  of  metal,  consists  of  a  cylindrical 
glass  jar  containing  mercury,  which  is  held  by  a  stirrup  at  the  extremity 
of  the  steel  pendulum-rod,  fig.  28.  The  same  increase  of  temperature 
which  lengthens  this  rod,  causes  the  volume  of  the  mercury  to  enlarge, 
and  its  level  to  rise  in  the  jar:  the  centre  of  gravity  is  thus  elevated,  and 
by  properly  adjusting  the  quantity  of  mercury  in 
the  glass,  the  virtual  length  of  the  pendulum  may 
be  made  constant. 

In  watches,  the  governing  power  is  a  horizontal 
weighted  wheel,  set  in  motion  in  one  direction  by 
the  machine  itself,  and  in  the  other  by  a  fine  spiral 
spring.  The  rate  of  going  depends  greatly  on  the 
diameter  of  this  wheel,  and  the  diameter  is  of  ne- 
cessity subject  to  variation  by  change  of  tempera- 
ture. To  remedy  the  evil  thus  involved,  the  cir- 
cumference of  the  balance-wheel  is  made  of  two 
metals  having  different  rates  of  expansion,  firmly 
soldered  together,  the  more  expansible  being  on  the 
outside.  The  compound  rim  is  also  cut  through  in  two  places,  as  repre- 
sented in  the  drawing.  When  the  watch  is  exposed  to  a  high  temperature, 
ana  the  diameter  of  the  wheel  becomes  enlarged  by  expansion,  each  seg- 


HEAT. 


47 


Fig.  30. 


ment  is  made,  by  the  same  agency,  to  assume  a  sharper  curve,  whereby 
its  centre  of  gravity  is  thrown  inward,  and  the  expansive  effect  completely 
compensated.  Many  other  beautiful  applications  of  the  same  principle 
might  be  pointed  out:  the  metallic  thermometer  of  M.  Breguet  is  one  of 
these. 

Mr.  Daniell  very  skilfully  applied  the  expansion  of  a  rod  of  metal  to 
the  measurement  of  temperatures  above  those  capable  of  being  indicated  by 
the  thermometer.  A  rod  of  iron  or  pla- 
tinum, about  five  inches  long,  is  dropped 
into  a  tube  of  black  lead  earthenware;  a 
little  cylinder  of  baked  porcelain  is  put 
over  it,  and  secured  in  its  place  by  a  pla- 
tinum strap  and  a  wedge  of  porcelain. 
When  the  whole  is  exposed  to  heat,  the  ex- 
pansion of  the  bar  drives  forward  the 
cylinder,  which  moves  with  a  certain  de- 
gree of  friction,  and  shows,  by  the  extent 
of  its  displacement,  the  lengthening  which 
the  bar  has  undergone.  It  remains,  there- 
fore, to  measure  the  amount  of  its  displace- 
ment, which  must  be  very  small,  even  when 
the  heat  has  been  exceedingly  intense. 
This  is  effected  by  the  contrivance  shown 
in  figure  30,  in  which  the  motion  of  the 
longer  arm  of  the  lever  carrying  the  vernier 

of  the  scale  is  multiplied  by  10,  in  consequence  of  its  superior  length.  The 
scale  itself  is  made  comparable  with  that  of  the  ordinary  thermometer,  by 
plunging  the  instrument  into  a  bath  of  mercury  near  its  point  of  congela- 
tion, and  afterwards  into  another  of  the  same  metal  in  a  boiling  state,  and 
marking  off  the  interval.  By  this  instrument  the  melting-point  of  cast 
iron  was  fixed  at  1530°  C.  (2786°  F.),  and  the  greatest  heat  of  a  good  wind- 
furnace  at  about  1815°  C.  (3390°  F.) 

The  actual  amount  of  expansion  which  different  solids  undergo  by  the 
same  increase  of  heat  has  been  carefully  investigated.  The  following  are 
some  of  the  results  of  the  best  investigations,  more  particularly  those  of 
Lavoisier  and  Laplace.  The  fraction  indicates  the  amount  of  expansion  in 
length  suffered  by  rods  of  the  undermentioned  bodies  in  passing  from  0° 
to  100° : 


Firwood* . 
English  flint  glass 
Platinumf 

Common  white  glass! 
Common  white  glass| 
Glass  without  lead 
Another  specimen     . 
Steel  untempered 


23TT 
TsVff 

Tempered 
Soft  iron 
Gold 

steel 

ti 

*: 

TT7TT 

TTW 

rfc 
TtfW 
¥*7 

Copper  . 
Brass 
Silver    . 
Lead 
Zinc       . 

. 

i 

From  the  linear  expansion,  the  cubic  expansion  (or  increase  of  volume) 
may  be  calculated.  When  the  expansion  of  a  body  in  different  directions 
is  equal,  as,  for  example,  in  glass,  hammered  metals,  and  generally  in 
most  uncrystallized  substances,  it  will  be  sufficient  to  triple  the  fraction 
expressing  the  increase  in  one  dimension.  This  rule  does  not  hold  true 


*  In  the  direction  of  the  vessels  —  Kater. 
J  Duloug  and  Petit. 


t  Borda. 

§  Lavoisier  and  Laplace ;  also  Magnus. 


48  HEAT. 

for  crystals  belonging  to  irregular  systems,  for  they  expand  unequally  in 
the  direction  of  the  different  axes. 

Metals  appear  to  expand  pretty  uniformly  for  equal  increments  of  heat 
within  the  limits  stated  ;  but  above  the  boiling-point  of  water  the  rate  of 
expansion  becomes  irregular  and  more  rapid. 

The  force  exerted  in  the  act  of  expansion  is  very  great.  In  laying  down 
railways,  building  iron  bridges,  erecting  long  ranges  of  steam-pipes,  and 
in  executing  all  works  of  the  kind  in  which  metal  is  largely  used,  it  is 
indispensable  to  make  provision  for  these  changes  of  dimensions. 

In  consequence  of  glass  and  platinum  having  nearly  the  same  amount  of 
expansion,  a  thin  platinum  wire  may  be  fused  into  a  glass  tube,  without 
any  fear  that  the  glass  will  break  on  cooling. 

A  very  useful  little  application  of  expansion  by  heat  is  that  of  the  cut- 
ting of  glass  by  a  hot  iron :  this  is  constantly  practised  in  the  laboratory 
for  a  great  variety  of  purposes.  The  glass  to  be  cut  is  marked  with  ink 
in  the  required  direction,  and  then  a  crack,  commenced  by  any  convenient 
method,  at  some  distance  from  the  desired  line  of  fracture,  may  be  led  by 
the  point  of  a  heated  iron  rod  along  the  latter  with  the  greatest  precision. 

Expansion  of  Liquids. — The  dilatation  of  a  liquid  may  be  determined  by 
filling  a  thermometer  with  it,  in  which  the  relation  between  the  capacity 
of  the  ball  and  that  of  the  stem  is  exactly  known,  and  observing  the  height 
of  the  column  at  different  temperatures.  It  is  necessary  in  this  experiment 
to  take  into  account  the  effects  of  the  expansion  of  the  glass  itself,  the 
observed  result  being  evidently  the  difference  of  the  two. 

Liquids  vary  exceedingly  in  this  particular.  The  following  table  is  taken 
from  Pe"clet's  Elements  de  Physique: 

Apparent  Dilatation  in  Glass  between  0°  and  100°. 

Water ^ 

Hydrochloric  acid,  sp.  gr.  1-137         .         .         .         .  ^V 

Nitric  acid,  sp.  gr.  1-4    .         .         .         .         .         .  ^ 

Sulphuric  acid,  sp.  gr.  1-85 ^ 

Ether TJ¥ 

Olive  oil .  j1^ 

Alcohol  .........  ^ 

Mercury -fa 

Most  of  these  numbers  must  be  taken  as  representing  mean  results ;  for 
there  are  few  liquids  which,  like  mercury,  expand  regularly  between  these 
temperatures.  Even  mercury  above  100°  shows  an  unequal  and  increasing 
expansion,  if  the  temperature  indicated  by  the  air-thermometer  be  used 
for  comparison.  This  is  shoWi  by  the  following  abstract  of  a  table  given 
by  llegnault  : 


Reading  of  Air 
Thermometer. 

0° 

100° 
200° 
300° 
350° 


Reading  of  Mercurial 
Thermometer. 

0° 

100° 
200° 
301° 
354° 


Temperature  deduced  from  the 
absolute  expansion  of  Mercury. 

0° 

100° 
202-78° 
308-34° 
362-16° 


Tlxe  absolute  amount  of  expansion  of  mercury  is,  for  many  reasons,  a 
point  of  great  importance:  it  has  been  very  carefully  determined  by  a 
method  independent  of  the  expansion  of  the  containing  vessel.  The  ap- 
paratus employed  for  this  purpose,  first  by  MM.  Dulong  and  Petit,  and 
later  by  Regnault,  is  shown  in  fig.  31,  divested,  however,  of  many  of  its 


HEAT. 


subordinate  parts.  It  consists  of  two  upright  glass  tubes,  connected  at 
their  bases  by  a  horizontal  tube  of  much  smaller  dimensions.  Since  a  free 
communication  exists  between  the  two  tubes,  mercury  poured  into  the  one 
will  rise  to  the  same  level  in  the  other,  provided  its  temperature  is  the 
same  in  both  tubes ;  when  this  is  not  the  case,  the  hotter  column  will  be 
the  taller,  because  the  expansion  of  the  metal  diminishes  its  specific  gravity, 
and  the  law  of  hydrostatic  equilibrium  requires  that  the  height  of  such 
columns  should  be  inversely  as  their  densities.  By  the  aid  of  the  outer 
cylinders,  one  of  the  tubes  is  maintained  constantly  at  0°,  while  the  other 
is  raised,  by  means  of  heated  water  or  oil,  to  any  required  temperature. 
The  perpendicular  heights  of  the  columns  may  then  be  read  off  by  a  hori- 
zontal micrometer  telescope,  moving  on  a  vertical  divided  scale. 

These  heights  represent  volumes  of  equal  weight,  because  volumes  of 
equal  weight  bear  an  inverse  proportion  to  the  densities  of  the  liquids,  so 
that  the  amount  of  expansion  admits  of  being  very  easily  calculated.  Thus, 
let  the  column  at  0°  be  six  inches  high,  and  that  at  100°,  6-108  inches;  the 
increase  of  height,  108  on  6000,  or  7i-  part  of  the  actual  cubical  expansion. 

Fig.  31. 


The  indications  of  the  mercurial  thermometer  are  inaccurate  when  very 
high  ranges  of  temperature  are  concerned,  from  the  increased  expansi- 
bility of  the  metal.  The  error  thus  caused  is,  however,  nearly  compen- 
sated for  temperatures  under  204-5°  by  the  expansion  of  the  glass  tube.  For 
higher  temperatures  a  small  correction  is  necessary,  as  the  above  table  shows. 

To  what  extent  the  expansion  of  different  liquids  may  vary  between  the 
same  temperatures  is  obvious  from  a  glance  at  fig.  32,  which  represents  the 
expansion  of  mercury  (M),  water  (W),  oil  of  turpentine  (T),  and  alcohol 
(A).  A  column  of  these  several  liquids,  equalling  at  0°  the  tenfold  height 
of  the  line  0  01  in  the  diagram,  would  rxhj^it.  when  heated  to  a  temper- 
ature of  10°,  20°,  30°,  &c.,  an  expansion  indicated  by  the  distances  at 


Fig.  32. 


10    20    30    40    50    00    70    80    90    100° 


s^hich  the  perpendicular  lines  drawn  over  the  numbers  10,  20,  30,  &c.,  are 
intersected  by  the  curves  belonging  to  each  of  these  liquids.     Thus  it  is 

6 


50 


HEAT. 


seen  that  oil  of  turpentine,  between  0°  and  100°,  expands  very  nearly  T^j 
of  its  volume,  and  that  mercury,  between  the  same  limits  of  temperature, 
expands  uniformly,  while  the  rate  of  expansion  of  the  other  liquids  increases 
with  the  rise  of  the  temperature. 

An  exception  to  the  regularity  of  expansion  in  liquids  exists  in  the  case 
of  water;  it  is  so  remarkable,  and  its  consequences  so  important,  that  it 
is  necessary  to  advert  to  it  particularly. 

Let  a  large  thermometer-tube  be  filled  with  water  at  the  common  tem- 
perature of  the  air,  and  then  artificially  cooled.  The  liquid  will  be  ob- 
served to  contract,  until  the  temperature  falls  to  about  4°  C.  (39-2°  F.,  or 
8°)  above  the  freezing-point.  After  this  a  further  reduction  of  tempera- 
ture causes  expansion  instead  of  contraction  in  the  volume  of  the  water, 
and  this  expansion  continues  until  the  liquid  arrives  at  its  point  of  con- 
gelation, when  so  sudden  and  violent  an  enlargement  takes  place  that  the 
vessel  is  almost  invariably  broken.  At  the  temperature  of  4°,  water  is  at 
its  maximum  density;*  increase  or  diminution  of  heat  produces  upon  it, 
for  a  short,  time,  the  same  effect. 

A  beautiful  experiment  by  Dr.  Hope  illustrates  the  same  fact.  If  a  tall 
jar  filled  with  water  at  10°  or  15°,  and  having  in  it  tAvo  small  thermometers, 
one  at  the  bottom  and  the  other  near  the  surface,  be  placed  at  rest  in  a 
very  cold  room,  the  following  changes  will  be  observed  : — The  thermometer 
at  the  bottom  will  fall  more  rapidly  than  that  at  the  top,  until  it  has  at- 
tained the  temperature  of  4°,  after  which  it  will  remain  stationary.  At 
length  the  upper  thermometer  will  also  mark  4°,  but  still  continue  to  sink 
as  rapidly  as  before,  while  that  at  the  bottom  remains  stationary.  It  is 
easy  to  explain  these  effects :  the  water  in  the  upper  part  of  the  jar  is  rapidly 
cooled  by  contact  with  the  air;  it  becomes  denser  in  consequence,  and  falls 
to  the  bottom,  its  place  being  supplied  by  the  lighter  and  warmer  liquid, 
which  in  its  turn  suffers  the  same  change ;  and  this  circulation  goes  on 
until  the  whole  mass  of  water  has  acquired  its  condition  of  maximum 
density,  that  is,  until  the  temperature  has  fallen  to  4°.  Beyond  this,  loss 
of  heat  occasions  expansion  instead  of  contraction,  so  that  the  very  cold 
water  on  the  surface  has  no  tendency  to  sink,  but  rather  the  reverse. 

This  singular  anomaly  in  the  behavior  of  water  is  attended  with  the 
most  beneficial  consequences  in  shielding  the  inhabitants  of  the  waters 
from  excessive  cold.  The  deep  lakes  of  the  North  American  continent 
never  freeze,  the  intense  and  prolonged  cold  of  the  winters  of  those  regions 
being  insufficient  to  reduce  the  temperature  of  such  masses  of  water  to  4°. 
Ice,  however,  of  great  thickness  forms  over  the  shallow  portions  and  the 
rivers,  and  accumulates  in  mounds  upon  the  beaches,  where  the  waves  are 
driven  up  by  the  winds 

Above  the  freezing-point,  s^-water  has  no  point  of  maximum  density. 
The  more  it  is  cooled  the  denser  it  becomes,  until  it  solidifies  at  -2  6°.f 
The  gradual  expansion  of  pure  water  cooled  below  4°  must  be  carefully 
distinguished  from  the  great  and  sudden  increase  of  volume  it  exhibits  in 
the  act  of  freezing,  in  which  respect  it  resembles  many  other  bodies  which 


*  According  to  the  latest  researches  of  Kopp,  the  point  of  greatest  density  of  the  water  is 
4-08°  C.  (39-34°  F.).  According  to  the  determinations  of  this  physicist,  the  volume  of  water 
«=  1  at  0°  C.  changes  when  heated  to  the  following  volumes : 


2°  0-99991 
4°  0  99988 
0-99990 
0-99999 
1-00012 
1-00031 
1-00056 


10° 
12° 
14° 


16°  1-00085 
18°  1-00118 
20°  1-00157 
22°  1-00200 
1-00247 
1-00272 
1-00406 


24° 
25° 


35° 
40° 
45° 
50° 
55° 
60° 
65° 


1-00570 
1-00753 
1-00954 
1-01177 
1-01410 
OO1659 
1-01930 


70°  1-02225 

75°  1.02544 

80°  1-02858 

85°  1-03189 

90°  1-03540 

95°  1-03909 

500°  1-04299 


•J  Neumann,  PoggewJorff's  Aunajen.,  cxiij.  382, 


HEAT. 

expand  on  solidifying.  The  force  thus  exerted  by  freezing  water  is  enor- 
mous. Thick  iron  shells  quite  filled  with  water,  and  exposed,  with  their 
fuse-holes  securely  plugged,  to  the  cold  of  a  Canadian  winter  night,  have 
been  found  split  on  the  following  morning.  The  freezing  of  water  in  the 
joints  and  crevices  of  rocks  is  a  most  potent  agent  in  their  disintegration. 
Expansion  of  Gases.  —  This  is  a  point  of  great  practical  importance  to  the 
chemist,  and  happily  we  have  very  excellent  evidence  upon  the  subject. 
The  following  four  propositions  exhibit,  at  a  single  view,  the  principal 
facts  of  the  case: 

1.  All  gases  expand  nearly  alike  for  equal  increments  of  heat;  and  all 

vapors,  when  remote  from  their  condensing  points,  follow  the  same 
law. 

2.  The  rate  of  expansion  is  not  altered  by  a  change  in  the  state  of  com- 

pression, or  elastic  force  of  the  gas  itself. 

3.  The  rate  of  expansion  is  uniform  for  all  degrees  of  heat. 

4.  The  actual  amount  of  expansion  is  equal  to  ^|¥  or  7^7  or  0-03666  of 

the  volume  of  the  gas  at  0°  Centigrade,  for  each  degree  of  the  same 
scale.* 

It  will  be  unnecessary  to  enter  into  any  description  of  the  methods  of 
investigation  by  which  these  results  have  been  obtained;  the  advanced 
student  will  find  in  Pouillet's  Elements  dc  Physique,  and  in  the  papers  of 
Magnus  and  Regnault,f  all  the  information  he  may  require. 

In  the  practical  manipulation  of  gases,  it  very  often  becomes  necessary 
to  make  a  correction  for  temperature,  or  to  discover  how  much  the  volume 
of  a  gas  would  be  increased  or  diminished  by  a  particular  change  of  tem- 
perature ;  this  can  be  effected  with  great  facility.  Let  it  be  required,  for 
example,  to  find  the  volume  which  100  cubic  inches  of  any  gas  at  10° 
would  become  on  the  temperature  rising  to  20°. 

The  rate  of  expansion  is  ^\^  or  ^J-7  of  the  volume  at  0°  for  each  degree; 
or  3000  measures  at  0°  become  3011  at  1°,  3022  at  2°,  3110  at  10°,  and 
3220  at  20°.  Hence 

Meas.  at  10°.        Meas.  at  20°.        Moas.  at  10°.        Meas.  at  20°. 
3110        :        3220       =        100        :       103-537 

If  this  calculation  is  required  to  be  made  on  the  Fahrenheit  scale,  it 
mtist  be  remembered  that  the  zero  of  that  scale  is  32°  below  the  melting- 
point  of  ice.  Above  this  temperature  the  expansion  for  each  degree  of 
the  Fahrenheit  scale  is  T|¥  of  the  original  volume. 

This,  and  the  correction  for  pressure,  are  operations  of  very  frequent 
occurrence  in  chemical  investigations,  and  the  student  will  do  well  to  become 
familiar  with  them. 

Note.  —  Of  the  four  propositions  stated  in  the  text,  the  first  and  second 
have  recently  been  shown  to  be  true  within  certain  limits  only;  and  the 
third,  although  in  the  highest  degree  probable,  would  be  very  difficult  to 
demonstrate  rigidly;  in  fact,  the  equal  rate  of  expansion  of  air  is  assumed 
in  all  experiments  on  other  substances,  and  becomes  the  standard  by  whick 
the  results  are  measured. 

The  rate  of  expansion  for  the  different  gases  is  not  absolutely  the  same, 
but  the  difference  is  so  small  that  for  most  purposes  it  may  with  perfect 
safety  be  neglected.  Neither  is  the  state  of  elasticity  altogether  indifferent, 

*  The  fraction  3^  jy^  is  very  convenient  for  calculation. 


t  Poggentlorff'H  Annalen,  iv.  1.  —  Ann.  Chim.  Phys.,  3d  series,  iv.  5,  and  v.  52.  —  See  also 
Watts's  Dictionary  ot  Chemistry,  art.  HEAT,  vol.  iii.  p.  46. 


52 


HEAT. 


the  expansion  being  sensibly  greater  for  an  equal  rise  of  temperature  when 
the  gas  is  in  a  compressed  state. 

It  is  important  to  notice  that  the  greatest  deviations  from  the  rule  are 
exhibited  by  those  gases  which,  as  will  hereafter  be  seen,  are  most  easily 
liquefied,  such  as  carbon  dioxide,  cyanogen,  and  sulphur  dioxide;  and  that 
the  discrepancies  become  smaller  and  smaller  as  the  elastic  force  is  lessened ; 
so  that,  if  means  existed  for  comparing  the  different  gases  in  states  equally 
distant  from  their  points  of  condensation,  there  is  reason  to  believe  that  the 
law  would  be  strictly  fulfilled. 

The  experiments  of  Dalton  and  Gay-Lussac  give  for  the  rate  of  expan- 
sion ^ly  of  the  volume  at  0°:  this  is  no  doubt  too  high.  Those  of  Rudberg 
give  27 5-;  those  of  Magnus  and  of  Regnault  ^7^. 

The  ready  expansibility  of  air  by  heat  gives  rise  to  the  phenomena  of 
winds.     In  the  temperate  regions  of  the  earth  these  are  very  variable  and 
uncertain,  but  within  and  near   the  tropics  a 
much  greater  regularity  prevails;  of  this  the 
trade-winds  furnish  a  beautiful  example. 

The  smaller  degree  of  obliquity  with  which 
the  sun's  rays  fall  in  the  localities  mentioned, 
occasions  the  broad  belt  thus  stretching  round 
the  earth  to  become  more  heated  than  any  other 
part  of  the  surface.  The  heat  thus  acquired  by 
absorption  is  imparted  to  the  lower  stratum  of 
air,  which,  becoming  expanded,  rises,  and  gives 
place  to  another:  and  in  this  manner  an  as- 
cending current  is  established,  the  colder  and 
heavier  air  streaming  in  laterally  from  the  more 
temperate  regions,  north  and  south,  to  supply  the  partial  vacuum  thus  occa- 
sioned. A  circulation  so  commenced  will  be  completed,  in  obedience  to  the 
laws  of  hydrostatics,  by  the  establishment  of  counter-currents  in  the 
higher  parts  of  the  atmosphere,  having  directions  the  reverse  of  those  on 
the  surface. 

Such  is  the  effect  produced  by  the  unequal  heating  of  the  equatorial 
parts ;  or,  more  correctly,  such  would  be  the  effect  were  it  not  greatly 
modified  by  the  earth's  movement  of  rotation. 

As  the  circumference  of  the  earth  is,  in  round  numbers,  about  24,000 
miles,  and  since  it  rotates  on  its  axis,  from  west  to  east,  once  in  24  hours, 
the  equatorial  parts  must  have  a  motion  of  1000  miles  per  hour;  this 
velocity  diminishes  rapidly  toward  each  pole,  where  it  is  reduced  to 
nothing. 

The  earth  in  its  rotation  carries  with  it  the  atmosphere,  whose  velocity 
of  movement  corresponds,  in  the  absence  of  disturbing  causes,  with  that 
part  of  the  surface  immediately  below  it.  The 
air  which  rushes  toward  the  equator  to  supply 
the  place  of  that  raised  aloft  by  its  diminished 
density,  brings  with  it  the  degree  of  momen- 
tum belonging  to  that  portion  of  the  earth's 
surface  from  which  it  set  out,  and  as  this  mo- 
mentum is  less  than  that  of  the  earth  under 
its  new  position,  the  earth  itself  travels  faster 
than  the  air  immediately  over  it,  thus  pro- 
ducing the  effect  of  a  wind  blowing  in  a  con- 
trary direction  to  that  of  its  own  motion.  The 
original  north  and  south  winds  are  thus  devi- 
ated from  their  primitive  directions,  and  made 
to  blow  more  or  less  from  the  eastward,  so  that 


HEAT. 


the  combined  effects  of  the  unequal  heating  and  of  the  movement  of  rota- 
tion is  to  generate  in  the  northern  hemisphere  a  constant  north-east  wind, 
and  in  the  southern  hemisphere  an  equally  constant  south-east  wind. 

In  the  same  manner  the  upper  or  return  current,  is  subject  to  a  change 
of  direction  in  the  reverse  order;  the  rapidly  moving  wind  of  the  tropics, 
transferred  laterally  towards  the  poles,  is  soon  found  to  travel  faster  than 
the  earth  beneath  it,  producing  the  effect  of  a  westerly  wind,  which  modi- 
fies the  primary  current. 

The  regularity  of  the  trade-winds  is  much  interfered  with  by  the  neigh- 
borhood of  large  continents,  which  produce  local  effects  upon  a  scale  suffi- 
ciently great  to  modify  deeply  the  direction  and  force  of  the  wind.  This 
is  the  case  in  the  Indian  Ocean.  They  usually  extend  from  about  the  28th 
degree  of  latitude  in  both  hemispheres  to  within  8°  of  the  equator,  but  are 
subject  to  some  variations  in  this  respect.  Between  them,  and  also  beyond 
their  boundaries,  lie  belts  of  calms  and  light  variable  winds;  and  beyond 
these  latter,  extending  into  higher  latitudes  in  both  hemispheres,  westerly 
winds  usually  prevail.  The  general  direction  of  the  trade-wind  of  the 
Northern  hemisphere  is  E.N.E.,  and  that  of  the  Southern  hemisphere 
E.S.E. 

The  trade-winds,  it  may  be  remarked,  furnish  an  admirable  physical 
proof  of  the  reality  of  the  earth's  movement  of  rotation. 

The  theory  of  the  action  of  chimneys,  and  of  natural  and  artificial  ven- 
tilation, belongs  to  the  same  subject. 

Let  the  reader  turn  to  the  demonstration  given  of  the  Archimedean 
hydrostatic  theorem :  let  him  once  more  imagine  a  body  immersed  in 
water,  and  having  a  density  equal  to  that  of  the  water;  it  will  remain  in 
equilibrium  in  any  part  beneath  the  surface,  and  for  these  reasons:  The 
force  which  presses  it  downward  is  the  weight  of  the  body  added  to  the 
weight  of  the  column  of  water  above  it;  the  force  which  presses  it  upward 
is  the  weight  of  a  column  of  water  equal  to  the  height  of  both  conjoined  ;  — 
the  density  of  the  body  is  that  of  water,  that  is,  it  weighs  as  much  as  an 
equal  bulk  of  that  liquid;  consequently,  the  downward  and  upward  forces 
are  equally  balanced,  and  the  body  remains  at  rest. 

Next,  let,  the  circumstances  be  altered;  let  the  body  be  lighter  than  an 
equal  bulk  of  water;  the  pressure  upward  of  the  column  of  water  a  c  is 
no  longer  compensated  by  the  downward   pres- 
sure of  the  corresponding   column  of  solid  and  Fig.  35. 
water  above  it;   the  former  force  preponderates, 
and  the  body  is  driven  upward.     If,  on  the  con- 
trary, the  body  be  specifically  heavier  than  wa- 
ter, then  the  latter  force  has  the  ascendency,  and 
the  boily  sinks. 

All  things  so  described  exist  in  a  common 
chimney  ;  the  solid  body,  of  the  same  density  as 
that  of  the  fluid  in  which  it  floats,  is  represented 
by  the  air  in  the  chimney  funnel;  the  space  ft  i' 
represents  the  whole  atmosphere  above  it.  When 
the  air  inside  and  outside  the  chimney  is  at  the 
same  temperature,  equilibrium  takes  place,  be- 
cause the  downward  tendency  of  the  air  within  is  counteracted  by  the 
upward  pressure  of  that  without. 

Now,  let  the  chimney  be  heated;  the  air  suffers  expansion,  and  a  portion 
is  expelled ;  the  chimney  therefore  contains  a  smaller  weight  of  air  than 
it  did  before ;  the  external  and  internal  columns  no  longer  balance  each 
other,  and  the  warmer  and  lighter  air  is  forced  upward  from  below,  and 
its  place  supplied  by  cold  air.  If  the  brick-work,  or  other  material  of 
which  the  chimney  is  constructed,  retain  its  temperature,  this  second  por- 

5* 


54:  HEAT. 

tion  of  air  is  disposed  of  like  the  first,  and  the  ascending  current  continues, 
so  long  as  the  sides  of  the  chimney  are  hotter  than  the  surrounding  air. 

Sometimes,  owing  to  sudden  changes  of  temperature  in  the  atmosphere, 
the  chimney  may  happen  to  be  colder  than  the  air  about  it.  The  column 
within  forthwith  suffers  contraction  of  volume ;  the  deficiency  is  filled  up 
from  without,  and  the  column  becomes  heavier  than  one  of  similar  height 
on  the  outside;  the  result  is,  that  it  falls  out  of  the  chimney,  just  as  the 
heavy  body  sinks  in  the  water,  and  has  its  place  occupied  by  air  from 
above.  A  descending  current  is  thus  produced,  which  may  be  often  no- 
ticed in  the  summer  season,  by  the  smoke  from  neighboring  chimneys  find- 
ing its  way  into  rooms  which  have  been  for  a  considerable  time  without  fire. 

The  ventilation  of  mines  has  long  been  conducted  upon  the  same  prin- 
ciple, and  more  recently  it  has  been  applied  to  dwelling-houses  and  assembly- 
rooms.  The  mine  is  furnished  with  two  shafts,  or  with  one  shaft  divided 
throughout  by  a  diaphragm  of  boards ;  and  these  are  so  arranged,  that  air 
forced  down  the  one  shall  traverse  the  whole  extent  of  the  workings  before 
it  escapes  by  the  other.  A  fire  kept  up  in  one  of  these  shafts,  by  rarefy- 
.  ing  the  air  within,  and  causing  an  ascending  current,  occasions  fresh  air 
to  traverse  every  part  of  the  mine,  and  sweep  before  it  the  noxious  gases 
•>  but  too  frequently  present. 

CONDUCTION   OF   HEAT. 

Different  bodies  possess  very  different  conducting  powers  with  respect 
to  heat :  if  two  similar  rods,  the  one  of  iron,  the  other  of  glass,  be  held  in 
the  flame  of  a  spirit-lamp,  the  iron  will  soon  become  too  hot  to  be  touched, 
while  the  glass  may  be  grasped  with  impunity  within  an  inch  of  the  red- 
hot  portion. 

Experiments  made  by  analogous  but  more  accurate  methods  have  estab- 
lished a  numerical  comparison  of  the  conducting  powers  of  many  bodies. 
The  following  may  he  taken  as  a  specimen  :  — 


Silver        .         .         .     1000 
Copper  .        .          736 

Gold  .         .         .532 

Brass     ...  236 

Tin  ...       145 

Iron  119 


Steel  .         .         .116 

Lead        ...  85 

Platinum     ...       84 
German  silver  .  63 

Bismuth  18 


As  a  class,  the  metals  are  by  very  far  the  best  conductors,  although  much 
difference  exists  between  them ;  stones,  dense  woods,  and  charcoal  follow 
next  in  order :  then  liquids  in  general,  and  gases,  whose  conducting  power 
is  almost  inappreciable. 

Under  favorable  circumstances,  nevertheless,  both  liquids  and  gases 
may  become  rapidly  heated  :  heat  applied  to  the  bottom  of  the  containing 
vessel  is  very  speedily  communicated  to  its  contents :  this,  however,  is  not 
so  much  by  conduction  as  by  convection,  or  carrying.  A  complete  circu- 
lation is  set  up ;  the  portions  in  contact  with  the  bottom  of  the  vessel  get 
heated,  become  lighter,  and  rise  to  the  surface,  and  in  this  way  the  heat 
becomes  communicated  to  the  whole.  If  these  movements  be  prevented  by 
dividing  the  vessel  into  a  great  number  of  compartments,  the  really  low 
conducting  power  of  the  substance  is  made  evident ;  and  this  is  the  reason 
why  certain  organic  fabrics,  as  wool,  silk,  feathers,  and  porous  bodies  in 
general,  the  cavities  of  which  are  full  of  air,  exhibit  such  feeble  powers 
of  conduction. 

The  circulation  of  heated  water  through  pipes  is  now  extensively  applied 
to  the  warming  of  buildings  and  conservatories;  and  in  chemical  works  a 
serpentine  metal  tube  containing  hot  oil  is  often  used  for  heating  stills  and 
evaporating-pans:  the  two  extremities  of  the  tube  are  connected  with  the 


HEAT.  OO 

ends  of  another  spiral  built  into  a  small  furnace  at  the  lower  level,  and  an 
unintermitting  circulation  of  the  liquid  takes  place  as  long  as  heat  is 
applied. 

CHANGE   OF   STATE. 

Solid  bodies  when  heated  are  expanded;  many  are  liquefied,  t.  e.,  they 
fuse.  The  fusion  of  solids  is  frequently  preceded  by  a  gradual  softening, 
more  especially  when  the  temperature  approaches  the  point  of  fusion. 
This  phenomenon  is  observed  in  the  case  of  wax  or  iron.  In  the  case  of 
other  solids  —  of  zinc  and  lead,  for  instance  —  and  several  other  metals, 
this  softening  is  not  observed.  Generally,  bodies  expand  during  the  pro- 
cess of  fusion ;  an  exception  to  this  rule  is  water,  which  expands  during 
freezing  (10  vol.  of  water  produce  nearly  11  vol.  of  ice),  while  ice  when 
fusing  produces  a  proportionately  smaller  volume  of  water.  The  expansion 
of  bodies  during  fusion,  and  at  temperatures  preceding  fusion,  or  the  con- 
traction during  solidification  and  further  refrigeration,  is  very  unequal. 
Wax  expands  considerably  before  fusing,  and  comparatively  little  during 
fusion  itself.  Wax,  when  poured  into  moulds,  fills  them  perfectly  during 
solidification,  but  afterwards  contracts  considerably.  Stearic  acid,  on  the 
contrary,  expands  very  little  before  fusion,  but  rather  considerably  during 
fusion,  and  consequently  pure  stearic  acid  when  poured  into  moulds  solidi- 
fies to  a  rough  porous  mass,  contracting  little  by  further  cooling.  The 
addition  of  a  little  wax  to  stearic  acid  prevents  the  powerful  contraction 
in  the  moment  of  solidification,  and  renders  it  more  fit  for  being  moulded. 

Latent  Heal  of  Fusion.  —  During  fusion  bodies  absorb  a  certain  quantity 
of  heat,  which  is  not  indicated  by  the  thermometer;  at  a  given  tempera- 
ture—  the  fusing-point,  for  instance  —  a  certain  weight  of  substance  con- 
tains when  solid  less  heat  than  when  liquid. 

If  equal  weights  of  water  at  0°  and  water  at  79°  be  mixed,  the  tempera- 
ture of  the  mixture  will  be  the  mean  of  the  two  temperatures,  or  39-5°. 
If  the  same  experiment  be  repeated  with  snow  or  finely-powdered  ice  at 
0°,  and  water  at  79°,  the  temperature  of  the  whole  will  be  only  0°,  but  the 
ice  will  have  been  melted, 

1  !bb;  :f  :±  ^?;}  =2  '-.  ^er  at  39.50 

IS: 

In  the  last  experiment,  therefore,  as  much  heat  has  been  apparently  lost 
as  would  have  raised  a  quantity  of  water  equal  to  that  of  the  ice  through 
a  range  of  79°. 

The  heat,  thus  become  insensible  to  the  thermometer  in  effecting  the 
liquefaction  of  the  ice,  is  called  latent  heatj  or,  better,  heat  of  fluidity. 

Again,  let  a  perfectly  uniform  source  of  heat  be  imagined,  of  such 
intensity  that  a  pound  of  water  placed  over  it  would  have  its  temperature 
raised  5°  per  minute.  Starting  with  water  at  0°,  in  rather  less  than  10 
minutes  its  temperature  would  have  risen  79°;  but  the  same  quantity  of 
ice  at  0°,  exposed  for  the  same  interval  of  time,  would  not  have  its  tem- 
perature raised  a  single  degree.  But,  then,  it  would  have  become  water; 
the  heat  received  would  have  been  exclusively  employed  in  effecting  the 
change  of  state. 

This  heat  is  not  lost,  for  when  the  water  freezes  it  is  again  evolved.  If 
a  tall  jar  of  water,  covered  to  exclude  dust,  be  placed  in  a  situation  where 
it  shall  be  quite  undisturbed,  and  at  the  same  time  exposed  to  great  cold, 
the  temperature  of  the  water  may  be  reduced  10°  or  more  below  its  freez- 


56 


HEAT. 


ing-point  without  the  formation  of  ice ;  *  but  then,  if  a  little  agitation  be 
communicated  to  the  jar,  or  a  grain  of  sand  dropped  into  the  water,  a  por- 
tion instantly  solidifies,  and  the  temperature  of  the  whole  rises  to  0°  ;  the 
heat  disengaged  by  the  freezing  of  a  small  portion  of  the  water  will  have 
been  sufficient  to  raise  the  whole  contents  of  the  jar  5°. 

This  curious  condition  of  instable  equilibrium  shown  by  the  very  cold 
water  in  the  preceding  experiment,  may  be  reproduced  with  a  variety  of 
solutions  which  tend  to  crystallize  or  solidify,  but  in  which  that  change  is 
for  a  while  suspended.  Thus,  a  solution  of  crystallized  sodium  sulphate 
in  its  own  weight  of  warm  water,  left  to  cool  in  an  open  vessel,  deposits  a 
large  quantity  of  the  salt  in  crystals.  If  the  warm  solution,  however,  be 
filtered  into  a  clean  flask,  which  when  full  is  securely  corked  and  set  aside 
to  cool  undisturbed,  no  crystals  will  be  deposited,  even  after  many  days, 
until  the  cork  is  withdrawn  and  the  contents  of  the  flask  violently  shaken. 
Crystallization  then  rapidly  takes  place  in  a  very  beautiful  manner,  and 
the  whole  becomes  perceptibly  warm. 

The  law  thus  illustrated  in  the  case  of  water  is  perfectly  general. 
Whenever  a  solid  becomes  a  liquid,  a  certain  fixed  and  definite  amount  of 
heat  disappears,  or  becomes  latent ;  and  conversely,  whenever  a  liquid  be- 
comes a  solid,  heat  to  a  corresponding  extent  is  given  out. 

The  following  table  exhibits  the  melting  points  of  several  substances, 
and  their  latent  heats  of  fusion  expressed  in  gram-degrees  —  that  is  to 
say,  the  numbers  in  the  column  headed  "latent  heat"  denote  the  number 
of  grams  of  water  the  temperature  of  which  would  be  raised  1°  Centigrade 
by  the  quantity  of  heat  required  to  fuse  one  grain  of  the  several  solids:  — 


Substance. 

Melting 
Point. 

Latent 
Heat. 

Substance. 

Melting 
Point. 

Latent 
Heat. 

39° 

2-82 

Tin 

235° 

14-25 

44 

5-0 

Silver 

1000 

21-1 

332 

5-4 

Zinc                      .     •     . 

433 

28-1 

Sulphur  .     . 
Iodine       .     . 

115 
107 

9-4 
11-7 

Calcium  chloride  ") 
(CaCl2  GH20)      / 

28-5 

40-7 

Bismuth  .     . 

270 

12-6 

Potassium  nitrate  . 

339 

47-4 

Cadmium 

320 

13-6 

Sodium  nitrate       .     . 

310-5 

63-0 

When  a  solid  substance  can  be  made  to  liquefy  by  a  weak  chemical 
attraction,  cold  results,  from  sensible  heat  becoming  latent.  This  is  the 
principle  of  the  many  frigorific  mixtures  to  be  found  described  in  some  of 
the  older  chemical  treatises.  When  snow  or  powdered  ice  is  mixed  with 
common  salt,  and  a  thermometer  plunged  into  the  mass,  the  mercury  sinks 
to  — 17-7°C.  (0°  F.),  while  the  whole  after  a  short  time  becomes  fluid  by  the 
attraction  between  the  water  and  the  salt ;  such  a  mixture  is  very  often 
used  in  chemical  experiments  to  cool  receivers  and  condense  the  vapors 
of  volatile  liquids.  Powdered  crystallized  calcium  chloride  and  snow  pro- 
duce cold  enough  to  freeze  mercury.  Even  powdered  potassium  nitrate, 

*  Fused  bodies,  when  cooled  down  to  or  below  their  fusing  point,  frequently  remain  liquid, 
more  especially  when  not  in  contact  with  solid  bodies  Thus,  water  in  a  mixture  of  oil  of 
almonds  and  chloroform,  of  specific,  gravity  equal  to  its  own,  remains  liquid  to  — 10°:  in  a  simi- 
lar manner  fused  sulphur  or  phosphorus,  floating  in  a  solution  of  zinc  chloride  of  appropriate 
concentration,  retains  the  liquid  condition  at  temperatures  40°  below  its  fusing  point.  Liquid 
bodies,  thus  cooled  below  their  fusing  point,  frequently  solidify  when  touched  with  a  solid  sub- 
stance, invariably  when  brought  in  contact  with  a  fragment  of  the  same  body  in  the  solid 
condition. 


HEAT.  57 

or  sal-ammoniac,  or  ammonium  nitrate,  dissolved  in  water,  occasions  a 
very  notable  depression  of  temperature :  in  every  case,  in  short,  in  which 
solution  is  unaccompanied  by  energetic  chemical  action,  cold  is  produced. 

No  relation  can  be  traced  between  the  actual  melting-point  of  a  sub- 
stance, and  its  latent  heat  when  in  the  fused  state. 

Latent  Heat  of  Vaporization.  —  A  law  of  exactly  the  same  kind  as  that 
described  affects  universally  the  gaseous  condition ;  change  of  state  from 
solid  or  liquid  to  gas  is  accompanied  by  absorption  of  sensible  heat,  and 
the  reverse  by  its  disengagement.  The  latent  heat  of  steam  and  other 
vapors  may  be  ascertained  by  a  mode  of  investigation  similar  to  that 
employed  in  the  case  of  water. 

When  water  at  0°  is  mixed  with  an  equal  weight  of  water  at  100°,  the  whole 
is  found  to  possess  the  mean  of  the  two  temperatures,  or  50° ;  on  the  other 
hand,  1  part  by  weight  of  steam  at  100°,  when  condensed  in  cold  water,  is 
found  to  be  capable  of  raising  5-4  parts  of  the  latter  from  the  freezing  to 
the  boiling-point,  or  through  a  range  of  100°.  Now  100  X  5-4=540° ;  that 
is  to  say,  steam  at  100°,  in  becoming  water  at  100°,  parts  with  enough 
heat  to  raise  a  weight  of  water  equal  to  its  own  (if  it  were  possible)  540°, 
of  the  thermometer.  When  water  passes  into  steam,  the  same  quantity  of 
sensible  heat  becomes  latent. 

The  vapors  of  other  liquids  seem  to  have  less  latent  heat  than  that  of 
water.  The  following  table  is  by  Dr.  Th.  Andrews,  and  serves  well  to 
illustrate  this  point.  The  latent  heats  are  expressed,  as  in  the  last  table, 
in  gram-degrees: 

Vapor  of  water 535-90° 

alcohol 202-40 

ether 90-45 

oxalic  ether      .         .         .         .         .         72-72 

acetic  ether          .         .         .         .         .     92-68 

ethylic  iodide  ....         46-87 

pyroxylic  spirit  .....  263-70 

carbon  bisulphide     ....         86-67 

tin  tetrachloride  .  30-35 

bromine    ......         45-66 

oil  of  turpentine          ....     74-03 

Ebullition  is  occasioned  by  the  formation  of  bubbles  of  vapor  within  the 
body  of  the  evaporating  liquid,  which  rise  to  the  surface  like  bubbles  of 
permanent  gas.  This  occurs  in  different  liquids  at  very  different  tempera- 
tures. Under  the  same  circumstances,  the  boiling-point  is  quite  constant, 
and  often  becomes  a  physical  character  of  great  importance  in  distinguish- 
ing liquids  which  much  resemble  each  other.  A  few  cases  may  be  cited 
in  illustration : 

Substance.  Boiling-point. 

Aldehyde 20-8° 

Ether 34-9 

Carbon  bisulphide          ......     46-1 

Alcohol 78-4 

Water 100 

Nitric  acid,  strong     ......       120 

Oil  of  turpentine  .         .         .         .         .         .157 

Sulphuric  acid 326-6 

Mercury 350 

For  ebullition  to  take  place,  it  is  necessary  that  the  elasticity  of  the 
vapor  should  be  able  to  overcome  the  cohesion  of  the  liquid  and  the  pres- 


58  HEAT. 

sure  upon  its  surface :  hence  the  extent  to  which  the  boiling-point  may  be 
modified. 

Water,  under  the  usual  pressure  of  the  atmosphere,  boils  at  100° 
(212°  F.)  :  in  a  partially  exhausted  receiver  or  on  a  mountain-top  it  boils 
at  a  much  lower  temperature:  and  in  the  best  vacuum  of  an  excellent  air- 
pump,  over  oil  of  vitriol,  which  absorbs  the  vapor,  it  will  often  enter  into 
violent  ebullition  while  ice  is  in  the  act  of  forming  upon  the  surface. 

On  the  other  hand,  water  confined  in  a  very  strong  metallic  vessel  may 
be  restrained  from  boiling  by  the  pressure  of  its  own  vapor  to  an  almost 
unlimited  extent;  a  temperature  of  177°  or  204°  is  very  easily  obtained; 
and,  in  fact,  it  is  said  that  it  may  be  made  red-hot,  and  yet  retain  its 
fluidity. 

There  is  a  very  simple  and  beautiful  experiment  illustrative  of  the  effect 
of   diminished  pressure  in  depressing  the  boiling-point    of  a  liquid.     A 
p{     36         little  water  is  made  to  boil  for  a  few  minutes  in  a  flask  or 
retort  placed  over  a  lamp,  until  the  air  has  been  chased  out, 
and  the  steam  issues  freely  from  the  neck.     A  tightly  fitting 
cork  is  then  inserted,   and  the   lamp  at  the  same  moment 
withdrawn.     When  the  ebullition  ceases,  it  may  be  renewed 
at  pleasure  for  a  considerable  time  by  the  affusion  of  cold 
water,  which,  by  condensing  the  vapor  within,  occasions  a 
partial  vacuum. 

The  nature  of  the  vessel,  or,  rather,  the  state  of  its  surface, 
exercises  an  influence  upon  the  boiling-point,  and  this  to  a 
much  greater  extent  than  was  formerly  supposed.  It  has 
long  been  noticed  that  in  a  metallic  vessel  water  boils,  under 
the  same  circumstances  of  pressure,  at  a  temperature  one  or  two  degrees 
below  that  at  which  ebullition  takes  place  in  glass:  but  it  has  lately  been 
shown  *  that  by  particular  management  a  much  greater  difference  can  be 
observed.  If  two  similar  glass  flasks  be  taken,  the  one  coated  in  the  in- 
side with  a  film  of  shellac,  and  the  other  completely  cleansed  by  hot  sul- 
phuric acid,  water  heated  over  a  lamp  in  the  first  will  boil  at  99-4°,  while 
in  the  second  it  will  often  rise  to  105°  or  even  higher;  a  momentary  burst 
of  vapor  then  ensues,  and  the  thermometer  sinks  a  few  degrees,  after  which 
it  rises  again.  In  this  state,  the  introduction  of  a  few  metallic  filings,  or 
angular  fragments  of  any  kind,  occasions  a  lively  disengagement  of  vapor, 
while  the  temperature  sinks  to  100°,  and  there  remains  stationary.  These 
remarkable  effects  must  be  attributed  to  an  attraction  between  the  surface 
of  the  vessel  and  the  liquid. 

When  out  of  contact  with  solid  bodies,  liquids  not  only  solidify  with  re- 
luctance, but  also  assume  the  gaseous  condition  with  greater  difficulty. 
Drops  of  water  or  of  aqueous  saline  solutions  floating  on  the  contact- 
surface  of  two  liquids,  of  which  one  is  heavier  and  the  other  lighter,  may 
be  heated  from  10  to  20  degrees  above  the  ordinary  boiling-point;  explo- 
sive ebullition,  however,  is  instantaneously  induced  by  contact  with  a  solid 
substance. 

A  cubic  inch  of  water  in  becoming  steam  under  the  ordinary  pressure 
of  the  atmosphere  expands  into  1696  cubic  inches,  or  nearly  a  cubic 
foot. 

Steam,  not  in  contact  with  ivater,  is  affected  by  heat  in  the  same  manner 
as  the  permanent  gases ;  its  rate  of  expansion  and  increase  of  elastic  force 
are  practically  the  same.  When  water  is  present,  the  rise  of  temperature 
increases  the  quantity  and  density  of  the  steam,  and  hence  the  elastic  force 
increases  in  a  far  more  rapid  proportion. 

This  elastic  force  of  steam  in  contact  with  water,  at  different  tempera- 

*  Marcet '  Ann.  Chim.  Phys.'  3d  scries,  v.  449. 


HEAT. 


51) 


lures,  has  been  very  carefully  determined  by  Arago  and  Dulong,  and  lately 
by  Magnus  and  llegnault.  The  force  is  expressed  in  atmospheres :  the  ab- 
solute pressure  upon  any  given  surface  can  be  easily  calculated,  allowing 
14  6  Ib  per  square  inch  to  each  atmosphere.  The  experiments  were  carried 
to  twenty-five  atmospheres;  at  which  point  the  difficulties  and  danger 
became  so  great  as  to  put  a  stop  to  the  inquiry:  the  rest  of  the  table  is 
the  result  of  calculations  founded  on  the  data  so  obtained: 


Pressure  of  Steam 
iu  atmospheres. 


1-5 

2 

2-5 

5 

5-5 

6 

6-5 

7       , 

7-5 

8 

9 

10 
11 

12       , 
13 
14 
15 
16 


Corresponding 
temperature. 

Pressure  of  Steam 
in  atmospheres. 

100° 

3 

. 

112 

3 

•5 

122 

4 

. 

129 

4 

•5 

153 

17 

j 

157 

18 

160 

19 

t 

163 

20 

167 

21 

t 

169 

22 

172 

23 

. 

177 

24 

182 

25 

. 

186 

30 

190 

35 

•m 

194 

40 

197 

45 

§ 

200-5 

50 

203 

Corresponding 
temperature. 

135° 

140-5 

145  5 

149 

207 

209 

212 

214 

217 

219 

222 

224 

226 

236 

245 

253 

255 

266 


It  is  very  interesting  to  know  the  amount  of  heat  requisite  to  convert 
water  of  any  given  temperature  into  steam  of  the  same  or  another  given 
temperature.  The  most  exact  experiments  on  this  subject  have  been  made 
by  Regnault.  He  arrived  at  this  result,  that  when  the  unit-weight  of  steam 
at  the  temperature  t°  is  converted  into  water  of  the  same  temperature,  and 
then  cooled  to  0°,  it  gives  out  the  quantity  of  heat  T,  which  is  represented 
by  the  formula: 

T  =  606  •  5  -f  0  •  305  t. 

This  formula  appears  to  hold  good  for  temperatures  above  and  below  the 
ordinary  boiling-point  of  water.  The  following  table  gives  the  values  of 
T,  corresponding  to  the  respective  temperatures  in  the  first  columns: 


t 

0° 

50 

100 

150 

200 


T 

606  •  5° 

621-7 

637-0 

652-2 

667-5 


T  is  called  the  total  heat  of  steam,  being  the  heat  required  to  raise  water 
from  0°  to  t,  together  with  that  which  becomes  latent  by  the  transformation 
of  water  of  t  into  steam  at  t.  Regnault  states,  as  a  result  of  some  very  deli- 
cate experiments,  that  the  heat  necessary  to  raise  a  unit-weight  of  water 
from  0°  to  t  is  not  exactly  denoted  by  t;  the  discrepancy,  however,  is  so 
small  that  it  may  be  disregarded.  Employing  the  approximate  value,  the 


60  HEAT. 

latent  heat  of  steam,  L,  at  any  temperature  will  be  found  by  subtracting  t 
from  the  total  heat;  or,  according  to  the  formula: 

L=  606  5  —  0-595  t. 

This  equation  shows  us  the  remarkable  fact  that  the  latent  heat  of  steam 
diminishes  as  the  temperature  rises.  Before  Regnault's  experiments  were 
made,  two  laws  of  great  simplicity  were  generally  admitted,  one  of  which, 
however,  contradicted  the  other.  Watt  concluded,  from  experiments  of  his 
own,  as  well  as  from  theoretical  speculations,  that  the  total  heat  of  steam 
would  be  the  same  at  all  temperatures.  Were  this  true,  equal  weights  of 
steam  passed  into  cold  water  would  always  exhibit  the  same  heating  power, 
no  matter  what  the  temperature  of  the  steam  might  be.  Exactly  the  same 
absolute  amount  of  heat,  and  consequently  the  same  quantity  of  fuel,  would 
be  required  to  evaporate  a  given  weight  of  water  in  vacuo  at  a  temperature 
which  the  hand  can  bear,  or  under  great  pressure,  and  at  a  high  tempera- 
ture. Watt's  Law,  though  agreeing  well  with  the  rough  practical  results 
obtained  by  engineers,  is  only  approximately  true ;  and  the  same  may  be 
said  of  the  deductions  which  have  just  been  made  from  it.  The  second  law, 
in  opposition  to  Watt's,  is  that  of  Southern,  stating  the  latent  heat  of  steam 
to  be  the  same  at  all  temperatures.  Regnault's  researches  have  shown 
that  neither  Watt's  law  (T  constant),  nor  Southern's  law  (L  constant)  is 
correct. 

The  economical  applications  of  steam  are  numerous  and  extremely  valu- 
able: they  may  be  divided  into  two  classes:  those  in  which  the  heating 
power  is  employed,  and  those  in  which  its  elastic  force  is  brought  into  use. 
The  value  of  steam  as  a  source  of  heat  depends  upon  the  facility  with 
which  it  may  be  conveyed  to  distant  points,  and  upon  the  large  amount  of 
latent  heat  it  contains,  which  is  disengaged  in  the  act  of  condensation.  An 
invariable  temperature  of  100°,  or  higher,  may  be  kept  up  in  the  pipes  or 
other  vessels  in  which  the  steam  is  contained  by  the  expenditure  of  a  very 
small  quantity  of  the  latter.  Steam-baths  of  various  forms  are  used  in  the 
arts  with  great  convenience,  and  also  by  the  scientific  chemist  for  drying 
filters  and  other  objects  where  excessive  heat  would  be  hurtful:  a  very 
good  instrument  of  the  kind  was  contrived  by  Mr.  Everitt.  It  is  merely  a 
small  kettle  (fig.  37),  surmounted  by  a  double  box  or  jacket,  into  which 
the  substance  to  be  dried  is  put,  and  loosely  covered  by  a  card.  The  appa- 
ratus is  placed  over  a  lamp,  and  may  be  left  without  attention  for  many 
hours.  A  little  hole  in  the  side  of  the  jacket  gives  vent  to  the  excess  of 
steam. 

The  principle  of  the  steam-engine  may  be  described  in  a  few  words:  its 
mechanical  details  do  not  belong  to  the  design  of  the  present  volume.     The 
machine  consists  essentially  of  a  cylinder  or  metal 
Fig.  37.  a  (fig.  38),  in  which  a  closely  fitting  solid  piston 

works,  the  rod  of  which  passes,  air-tight,  through 
a  stuffing-box  at  the  top  of  the  cylinder,  and  is 
connected  with  the  machinery  to  be  put  in  motion, 
directly,  or  by  the  intervention  of  an  oscillating 
beam.  A  pipe  communicates  with  the  interior  of 
the  cylinder,  and  also  with  a  vessel  surrounded 
with  cold  water,  called  the  condenser  b,  into  which 
a  jet  of  cold  water  can  at  pleasure  be  introduced. 
A  sliding-valve  arrangement,  shown  at  c,  serves  to 
open  a  communication  between  the  boiler  and  the 
cylinder,  and  between  the  cylinder  and  the  con- 
denser in  such  a  manner  that  while  the  steam  is 
allowed  to  press  with  all  its  force  upon  one  side  of  the  piston,  the  other, 
open  to  the  condenser,  is  necessarily  vacuous.  The  valve  is  shifted  by  the 


HEAT. 


61 


Fig.  38. 


engine  itself  at  the  proper  moment,  so  that  the  piston  is  alternately  driven 

by  the  steam  up  and  down  against  a  vacuum.    A  large  air-pump,  not  shown 

in  the  engraving,   is    connected    with    the 

condenser,   and  serves  to    remove  any  air 

that  may  enter  the  cylinder,  and  also  the 

water  produced  by  condensation,  together 

with  that  which  may  have  been  injected. 

Such  is  the  vacuum  or  condensing  steam- 
engine.  In  what  is  called  the  high-pres- 
sure engine,  the  condenser  and  air-pump 
are  suppressed,  and  the  steam  is  allowed 
to  escape  at  once  from  the  cylinder  into 
the  atmosphere.  It  is  obvious  that  in  this 
arrangement  the  steam  has  to  overcome 
the  whole  pressure  of  the  air,  and  a  much 
greater  elastic  force  is  required  to  produce 
the  same  effect;  but  this  is  to  a  very  great 
extent  compensated  by  the  absence  of  the 
air-pump  and  the  increased  simplicity  of 
the  whole  machine.  Large  engines,  both 
on  shore  and  in  steamships,  are  usually 
constructed  on  the  condensing  principle, 
the  pressure  seldom  exceeding  six  or  seven 
pounds  per  square  inch  above  that  of  the 
atmosphere;  for  small  engines  the  high- 
pressure  plan  is,  perhaps,  preferable. 
Locomotive  engines  are  of  this  kind. 

A  peculiar  modification  of  the  steam- 
engine,  employed  in  Cornwall,  for  draining 
the  deep  mines  of  that  counti^y,  is  now  get- 
ting into  use  elsewhere  for  other  purposes. 
In  this  machine,  economy  of  fuel  is  carried 

to  a  most  extraordinary  extent,  engines  having  been  known  to  perform  the 
dull/  of  raising  more  than  100, 000, 000  Ibs.  of  water  one  foot  high  by  the  con- 
sumption of  a  single  bushel  of  coals.  The  engines  are  single-acting,  the  down- 
stroke,  which  is  made  against  a  vacuum,  being  the  effective  one,  and  em- 
ployed to  lift  the  enormous  weight  of  the  pump-rods  in  the  shaft  of  the 
•mine.  When  the  piston  reaches  the  bottom,  the  communication  both  with 
the  boiler  and  the  condenser  is  cut  off,  while  an  equilibrium-valve  is  opened 
connecting  the  upper  and  lower  extremities  of  the  cylinder,  whereupon 
the  weight  of  the  pump-rods  draws  the  piston  to  the  top  and  makes  the 
up-stroke.  The  engine  is  worked  expansively,  as  it  is  termed,  steam  of 
high  tension  being  employed,  which  is  cut  off  at  one-eighth  or  even  one- 
tenth  of  the  stroke. 

The  process  of  distillation,  which  may  now  be  noticed,  is  very  simple: 
its  object  is  either  to  separate  substances  which  rise  in  vapor  at  different 
temperatures,  or  to  part  a  volatile  liquid  from  a  substance  incapable  of 
volatilization.  The  same  process  applied  to  bodies  which  pass  directly 
from  the  solid  to  the  gaseous  condition,  and  the  reverse,  is  called  sublimation. 
Every  distillatory  apparatus  consists  essentially  of  a  boiler,  in  which  the 
vapor  is  raised,  and  of  a  condenser,  in  which  it  returns  to  the  liquid  or 
solid  condition.  In  the  still  employed  for  manufacturing  purposes,  the 
latter  is  usually  a  spiral  metal  tube  immersed  in  a  tub  of  water.  The 
common  retort  and  receiver  constitute  the  simplest  arrangement  for  distil- 
lation on  the  small  scale;  the  retort  is  heated  by  a  gas  lamp,  and  the  re- 
ceiver is  kept  cool,  if  necessary,  by  a  wet  cloth,  or  it  may  be  surrounded 
with  ice.  (Fig.  39.) 
6 


62 


HEAT. 


Liebig's  condenser*  (fig.  40)  is  a  very  valuable  instrument  in  the  labora- 
tory; it  consists  of  a  glass  tube  tapering  from  end  to  end,  fixed  by  per- 


forated  corks  in  the  centre  of  the  metal  pipe,  provided  with  tubes  so  ar- 
ranged that  a  current  of  cold  water  may  circulate  through  the  apparatus. 
By  putting  ice  into  the  little  cistern,  the  water  may  be  kept  at  0°,  and 
extremely  volatile  liquids  condensed. 

Fig.  40. 


Liquids  evaporate  at  temperatures  below  their  boiling-points:  in  this 
case  the  evaporation  takes  place  slowly  from  the  surface.  Water,  or  alco- 
hol, exposed  in  an  open  vessel,  at  the  temperature  of  the  air,  gradually 
disappears;  the  more  rapidly,  the  warmer  and  drier  the  air. 

This  fact  was  formerly  explained  by  supposing  that  air  and  gases  in 
general  had  the  power  of  dissolving  and  holding  in  solution  certain  quan- 

[*  Invented  by  Weitzel,  the  elder,  of  Stockholm,  and  well  described  and  figured  in  Gray'a 
Operative  Chemist. — R.  B.] 


HEAT. 


63 


titles  of  liquids,  and  that  this  power  increased  with  the  temperature:   such 
an  idea  is  incorrect. 

If  a  barometer-tube  be  carefully  filled  with  mercury  and  inverted  in  the 
usual  manner,  and  then  a  few  drops  of  water  passed  up  the  tube  into  the 
vacuum  above,  a  very  remarkable  effect  will  be  observed; — the  mercury 
will  be  depressed  to  a  small  extent,  and  this  depression  will  increase  with 
increase  of  temperature.  Now,  as  the  space  above  the  mercury  is  void 
of  air,  and  the  weight  of  the  few  drops  of  water  quite  inadequate  to  ac- 
count for  this  depression,  it  must  of  necessity  be  imputed  to  the  vapor 
which  instantaneously  rises  from  the  water  into  the  vacuum ;  p.  41 
and  that  this  effect  is  really  due  to  the  elasticity  of  the  aqueous 
vapor,  is  easily  proved  by  exposing  the  barometer  to  a  heat  of 
100°  C.  (212°  F.),  when  the  depression  of  the  mercury  will  be 
complete,  and  it  will  stand  at  the  same  level  within  and  with- 
out the  tube;  indicating  that  at  that  temperature  the  elasticity 
of  the  vapor  is  equal  to  that  of  the  atmosphere  —  a  fact  which 
the  phenomenon  of  ebullition  has  already  shown. 

By  placing  over  the  barometer  a  wide  open  tube  dipping 
into  the  mercury  below,  and  then  filling  this  tube  Avith  water 
at  different  temperatures,  the  tension  of  the  aqueous  vapor 
for  each  degree  of  the  thermometer  may  be  accurately  deter- 
mined by  its  depressing  effect  upon  the  mercurial  column; 
the  same  power  which  forces  the  latter  down  one  inch  against 
the  pressure  of  the  atmosphere,  would  of  course  elevate  a 
column  of  mercury  to  the  same  height  against  the  vacuum,  and 
in  this  way  the  tension  may  be  conveniently  expressed.  The 
following  table  was  drawn  up  by  Dalton,  to  whom  we  owe  the 
method  of  investigation: 


Temperature. 

Tension  in  inches 

F. 

C. 

of  mercury. 

?)'2° 

0° 

.      0-200 

40    . 

4-4 

.      0263 

50     . 

10 

.      0-375 

60    . 

15-5 

.      0-524 

70     . 

21-1 

.      0721 

80     . 

26-6 

.      1-000 

90     . 

32-2 

.       1-360 

100     . 

37-7 

.      1-860 

110     . 

43-3 

.      2-530 

120     . 

48-8 

.      3-330 

Temperature.        Tension  in  inches 

F. 

C.             c 

>f  mercury. 

130° 

.     54-4°     . 

434 

140 

.     60 

5-74 

150 

.     65-5      . 

7-42 

160 

.     71-1      . 

9-46 

170 

.     76-6      . 

12-13 

180 

.     82-2      . 

15-15 

190 

.     87-7      . 

19-00 

200 

.     93-3      . 

23  64 

212 

.   100 

3000 

Another  table  representing  the  tension  of  the  vapor  of  water,  drawn  up 
by  llegnault,  is  given  at  the  end  of  the  work. 

Other  liquids  tried  in  this  manner  are  found  to  emit  vapors  of  greater  or 
less  tension,  for  the  same  temperature,  according  to  their  different  degrees 
of  volatility :  thus,  a  little  ether  introduced  into  the  tube  depresses  the 
mercury  10  inches  or  more  at  the  ordinary  temperature  of  the  air;  oil  of 
vitriol,  on  the  other  hand,  does  not  emit  any  sensible  quantity  of  vapor 
until  a  much  greater  heat  is  applied ;  and  that  given  off  by  mercury  itself 
in  warm  summer  weather,  although  it  may  be  detected  by  very  delicate 
moans,  is  far  too  little  to  exercise  any  effect  upon  the  barometer.  In  the 
case  of  water,  the  evaporation  is  quite  distinct  and  perceptible  at  the  lowest 
temperatures,  when  frozen  to  solid  ice  in  the  barometer-tube:  snow  on  the 
ground,  or  on  a  house-top,  may  often  be  noticed  to  vanish,  from  the  same 
cause,  day  by  day  in  the  depth  of  winter,  when  melting  is  impossible. 

There  exists  for  each  vapor  a  state  of  density  which  it  cannot  pass  with- 
out losing  its  gaseous  condition,  and  becoming  liquid;  this  point  is  called 


64  HEAT. 

the  condition  of  maximum  density.  When  a  volatile  liquid  is  introduced 
in  sufficient  quantity  into  a  vacuum,  this  condition  is  always  reached,  and 
then  evaporation  ceases.  Any  attempt  to  increase  the  density  of  this  vapor 
by  compressing  it  into  a  smaller  space  will  be  attended  by  the  liquefaction 
of  a  portion,  the  density  of  the  remainder  being  unchanged.  If  a  little 
ether  be  introduced  into  a  barometer,  and  the  latter  slowly  sunk  into  a 
very  deep  cistern  of  mercury  (fig.  42),  it  will  be  found  that  the  height  of 
the  column  of  mercury  in  the  tube  above  that  in  the  cistern  remains  un- 
altered until  the  upper  extremity  of  the  barometer  ap- 
preaches  the  surface  of  the  metal  in  the  column  and  all 
the  ether  has  become  liquid.  It  will  be  observed  also, 
that,  as  the  tube  sinks,  the  stratum  of  liquid  ether  in- 
creases  in  thickness,  but  no  increase  of  elastic  force  oc- 
curs  in  the  vapor  above  it,  and,  consequently,  no  increase 
of  density;  for  tension  and  density  are  always,  under 
ordinary  circumstances  at  least,  directly  proportionate  to 
each  other. 

The  point  of  maximum  density  of  vapor  is  dependent 
upon  the  temperature;  it  increases  rapidly  as  the  tem- 
perature rises.  This  is  well  shown  in  the  case  of  water. 
Thus,  taking  the  spec,  grav,  of  atmospheric  air  at  100° 
=1000,  that  of  aqueous  vapor  in  its  greatest  state  of 
compression  for  the  temperature  will  be  as  follows: 

Temperature.  Specific  gravity.  "Weight  of  100  cubic 

C.  F.  inches. 

0°  .  32°  .  5-690  .           0-180  grains. 

10  50  10-293  .           0'247 

15-5  .  60  .  14-108  .           0-338 

37-7  .  100  .  46-500  .           1-113 

65*5  .  150  .  170-293  .           4'076 

100  .  212  .  625-000  .  14-962 

The  last  number  was  experimentally  found  by  Gay- 
Lussac;  the  others  are  calculated  from  that  by  the  aid  of 
Dalton's  table  of  tensions,  on  the  assumption  that  steam, 
not  in  a  state  of  saturation,  that  is,  below  the  point  of 
greatest  density,  obeys  the  laws  of  Mariotte  (which  is, 
however,  only  approximately  true),  and  that  when  it  is 
cooled  it  contracts  like  the  permanent  gases. 

Thus,  there  are  two  distinct  methods  by  which  a  vapor 
may  be  reduced  to  the  liquid  form — pressure,  by  causing 
increase  of  density  until  the  point  of  maximum  density 
for  a  given  temperature  is  reached ;  arid  cold,  by  which 
the  point  of  maximum  density  is  itself  lowered.  The 
most  powerful  effects  are  produced  when  both  are  con- 
joined. 

For  example,  if  100  cubic  inches  of  vapor  of  water  at  100°  F.,  in  the 
state  above  described,  had  its  temperature  reduced  to  50°  F.,  not  less  than 
0-89*  grain  of  liquid  water  would  necessarily  separate,  or  very  nearly 
eight-tenths  of  the  whole. 

Evaporation  into  a  space  filled  with  air  or  gas  follows  the  same  law  as 
evaporation  into  a  vacuum :  as  much  vapor  arises,  and  the  condition  of 
maximum  density  is  assumed  in  the  same  manner,  as  if  the  space  were 
perfectly  empty ;  the  sole  difference  lies  in  the  length  of  time  required. 

*  100  cub.  inch,  aqueous  vapor  at  100°  F.,  weighing  1-113  grain,  would  at  50°  F.  become 
reduced  to  91-07  cub.  inch.,  weighing  0-225  grain. 


HEAT.  65 

When  a  liquid  evaporates  into  a  vacuum,  the  point  of  greatest  density  is 
attained  at  once,  while  in  the  other  case  some  time  elapses  before  this 
happens :  the  particles  of  air  appear  to  oppose  a  sort  of  mechanical  resist- 
ance to  the  rise  of  the  vupor.  The  ultimate  effect  is,  however,  precisely 
the  same. 

When  to  a  quantity  of  perfectly  dry  gas  confined  in  a  vessel  closed  by 
mercury  a  little  water  is  added,  the  latter  immediately  begins  to  evaporate, 
and  after  some  time  as  much  vapor  will  be  found  to  have  risen  from  it  as 
if  no  gas  had  been  present,  the  quantity  depending  entirely  on  the  tempera- 
ture to  which  the  whole  is  subjected.  The  tension  of  this  vapor  will  add 
itself  to  that  of  the  gas.  and  produce  an  expansion  of  volume,  which  will  be 
indicated  by  an  alteration  of  level  in  the  mercury. 

Vapor  of  water  exists  in  the  atmosphere  at  all  times  and  in  all  situations, 
and  there  plays  a  most  important  part  in  the  economy  of  nature.  The  pro- 
portion of  aqueous  vapor  present  in  the  air  is  subject  to  great  variation, 
and  it  often  becomes  important  to  determine  its  quantity.  This  is  easily 
done  by  the  aid  of  the  foregoing  principles. 

Deiv-Point.  —  If  the  aqueous  vapor  be  in  its  condition  of  greatest  possible 
density  for  the  temperature,  or,  as  it  is  frequently,  but  most  incorrectly, 
expressed,  the  air  be  saturated  with  vapor  of  water,  the  slightest  reduction 
of  temperature  will  cause  the  deposition  of  a  portion  in  the  liquid  form. 
If,  on  the  contrary,  as  is  almost  always  in  reality  the  case,  the  vapor  of 
water  be  below  its  state  of  maximum  density,  that  is,  in  an  expanded  con- 
dition, it  is  clear  that  a  considerable  fall  of  temperature  may  occur  before 
liquefaction  commences.  The  degree  at  which  this  takes  place  is  called  the 
dew-point,  and  it  is  determined  with  great  facility  by  a  very  simple  method. 
A  little  cup  of  thin  tin  plate  or  silver,  well  polished,  is  filled  with  water  at 
the  temperature  of  the  air,  and  a  delicate  thermometer  inserted.  The 
water  is  then  cooled  by  dropping  in  fragments  of  ice,  or  dissolving  in  it 
powdered  sal-ammoniac,  until  moisture  begins  to  make  its  appearance  on  the 
outside,  dimming  the  bright  metallic  surface.  The  temperature  of  the  dew- 
point,  is  then  read  off  upon  the  thermometer,  and  compared  with  that  of 
the  air. 

Suppose,  by  w^  of  example,  that  the  latter  were  70°  F.,  and  the  dew- 
point  50°  F.,  the  elasticity  of  the  watery  vapor  present  would  correspond 
to  a  maximum  density  proper  to  50°  F.,  and  would  support  a  column  of 
mercury  0-375  inch  high.  If  the  barometer  on  the  spot  stood  at  30  inches, 
therefore,  29-025  inches  would  be  supported  by  the  pressure  of  the  dry  air, 
and  the  remaining  0-375  inch  by  the  vapor.  Now  a  cubic  foot  of  such  a 
mixture  must  be  looked  upon  as  made  up  of  a  cubic  foot  of  dry  air,  and  a 
cubic  foot  of  watery  vapor,  occupying  the  same  space,  and  having  tensions 
indicated  by  the  numbers  just  mentioned.  A  cubic  foot,  or  1728  cubic 
inches  of  vapor,  at  70°  F.,  would  become  reduced  by  contraction,  according 
to  the  usual  law,  to  1062-8  cubic  inches  at  50°  F. ;  this  vapor  would  be  at  its 
maximum  density,  having  the  specific  gravity  pointed  out  in  the  table ; 
hence  1602-8  cubic  inches  would  weigh  4-11  grains.  The  weight  of  the 
aqueous  vapor  contained  in  a  cubic  foot  of  air  will  thus  be  ascertained.  In 
this  country  the  difference  between  the  temperature  of  the  air  and  the  dew- 
point  seldom  reaches  30°  F.  (16-6°  C.)  degrees;  but  in  the  Deccan,  with  a 
temperature  of  90°  F.  (32-2°  C.),  the  dew-point  sinks  as  low  as  29°  F.,  mak- 
ing the  degrees  of  dryness  61°  F.* 

Another  method  of  finding  the  proportion  of  moisture  present  in  the  air 
is  to  observe  the  rapidity  of  evaporation,  which  is  always  in  some  relation 
to  the  degree  of  dryness.  The  bulb  of  a  thermometer  is  covered  with  mus- 
lin, and  kept  wet  with  water;  evaporation  produces  cold,  as  will  presently  be 
seen,  and  accordingly  the  thermometer  soon  sinks  below  the  actual  tem- 

*  Daniel!,  Introduction  to  Chemical  Philosophy,  r-  15-*- 
6* 


HEAT. 


Fig.  43. 


perature  of  the  air.  When  it  comes  to  rest,  the  degree  is  noticed,  and  from 
a  comparison  of  the  two  temperatures  an  approximation  to  the  dew-po^nt 
can  be  obtained  by  the  aid  of  a  mathematical  formula  con- 
trived for  the  purpose.  This  is  called  the  wet-bulb  hygrom- 
eter: it  is  often  made  in  the  manner  shown  in  fig.  43,  where 
one  thermometer  serves  to  indicate  the  temperature  of  the  air, 
and  the  other  to  show  the  rate  of  evaporation,  being  kept  wet 
by  the  thread  dipping  in  the  water  reservoir. 

Liquefaction  of  Gases.  —  The  perfect  resemblance  in  every 
respect  which  vapors  bear  to  permanent  gases,  led,  very 
naturally,  to  the  idea  that  the  latter  might,  by  the  application 
of  suitable  means,  be  made  to  assume  the  liquid  condition,  and 
this  surmise  was,  in  the  hands  of  Mr.  Faraday,  to  a  great  ex- 
tent verified.  Out  of  the  small  number  of  such  substances 
tried,  not  less  than  eight  gave  way;  and  it  is  quite  fair  to 
infer  that,  had  means  of  sufficient  power  been  at  hand,  the 
rest  would  have  shared  the  same  fate,  and  proved  to  be  nothing 
more  than  the  vapors  of  volatile  liquids  in  a  state  very  far  re- 
moved from  that  of  their  maximum  density.  The  subjoined 
table  represents  the  results  of  Mr.  Faraday's  first  investiga- 
tions, with  the  pressure  in  atmospheres,  and  the  temperatures 
at  which  the  condensation  takes  place.* 


Sulphur  dioxide 
Hydrogen  sulphide 
Carbon  dioxide 
Chlorine 

Nitrogen  monoxide 
Cyanogen 
Ammonia 
Hydrochloric  acid 


Atmospheres. 

2 

.  17  . 
36 
4  . 

50 

.   3-6 
6-5  . 

,  40  , 


Temperatures. 
C.  I1. 

7-2°       45° 


10 
0 

15-5 
7-2 
7-2 

10 

10 


50 
32 
60 
45 
45 
50 
50 


The  method  of  proceeding  was  very  simple :  the  materials  were  scaled 
up  in  a  strong,  narrow  tube,  together  with  a  little  pressure-gauge,  consist- 
ing of  a  slender  tube,  closed  at  one  end,  and  having  within  it,  near  the 

open   extremity,  a  globule   of 

Fig.  44.  mercury.     The  gas  being  dis- 

engaged by  heat,  accumulated 
in  the  tube,  and  by  its  own 
pressure  brought  about  con- 
densation. The  force  required 
for  this  purpose  was  judged 
of  by  the  diminution  of  volume  of  the  air  in  the  gauge. 

Mr.  Faraday  has  since  resumed,  with  the  happiest  results,  the  subject 
of  the  liquefaction  of  the  permanent  gases.  By  using  narrow  green  glass 
tubes  of  great  strength,  powerful  condensing  syringes,  and  an  extremely 
low  temperature,  produced  by  means  to  be  presently  described,  olefiant  gas, 
hydriodic  and  hydrobromic  acids,  phosphoretted  hydrogen,  and  the  gaseous 
fluorides  of  silicon  and  boron,  were  successively  liquefied.  Oxygen,  hydro- 
gen, nitrogen,  nitrogen  dioxide,  carbon  monoxide,  and  marsh  gas,  refused 
to  liquefy  at — 166°  F.,  while  subjected  to  pressures  varying  from  27  to 
58  atmospheres. 

Sir  Isambard  Brunei,  and,  more  recently,  M.  Thilorier,  of  Paris,  succeeded 


Phil.  Trans,  for  1823,  p.  189. 


HEAT. 


67 


in  obtaining  liquid  carbon  dioxide  (commonly  called  carbonic  acid)  in 
great,  abundance.  The  apparatus  of  M.  Thilorier  consists  of  a  pair  of  ex- 
tremely strong  metallic  vessels,  one  of  which  is  destined  to  serve  the  pur- 
pose of  a  retort,  and  the  other  that  of  a  receiver.  They  are  made  either 
of  thick  cast  iron  or  gun-metal,  or,  still  better,  of  the  best  and  heaviest 
boiler-plate,  and  arc  furnished  with  stop-cocks  of  a  peculiar  kind,  the 
workmanship  of  which  must  be  excellent.  The  generating  vessel  or  retort 
has  a  pair  of  trunnions  upon  which  it  swings  in  an  iron  frame.  The  joints 
are  secured  by  collars  of  lead,  and  every  precaution  taken  to  prevent  leak- 
age under  the  enormous  pressure  the  vessel  has  to  bear.  The  receiver  re- 
sembles the  retort  in  every  respect;  it  has  a  similar  stop-cock,  and  is  con- 
nected with  the  retort  by  a  strong  copper  tube  and  a  pair  of  union  screw- 
joints;  a  tube  passes  from  the  stop-cock  downwards,  and  terminates  near 
the  bottom  of  the  vessel. 

The  operation  is  thus  conducted :  2|  Ib.  of  acid  sodium  carbonate,  and 
6£lb.  of  water  at  100°  F.,  are  introduced  into  the  generator;  oil  of  vitriol 
to  the  amount  of  1^  Ib.  is  poured  into  a  copper  cylindrical  vessel,  which  is 

Fig.  45. 


lowered  down  into  the  mixture,  and  set  upright;  the  stop-cock  is  then 
screwed  into  its  place,  and  forced  home  by  a  spanner  and  mallet.  The 
machine  is  next  tilted  up  on  its  trunnions,  that  the  acid  may  run  out  of  the 
cylinder  and  mix  with  the  other  contents  of  the  generator;  and  this  mix- 
ture is  favored  by  swinging  the  whole  backward  and  forward  for  a  few 
minutes,  after  which  it  may  be  suffered  to  remain  a  little  time  at  rest. 

The  receiver,  surrounded  with  ice,  is  next  connected  with  the  generator, 
and  both  cocks  opened;  the  liquefied  carbon  dioxide  distils  over  into  the 
colder  vessel,  and  there  again  in  part  condenses.  The  cocks  are  now 
closed,  the  vessels  disconnected,  the  cock  of  the  generator  opened  to  allow 
the  contained  gas  to  escape;  and,  lastly,  when  the  issue  of  gas  has  <jnitc- 
,  the  stop-cock  itself  is  unscrewed,  and  the  sodium  sulphate  turned 


68 


HEAT. 


Fig.  46. 


out.  This  operation  must  be  repented  five  or  six  times  before  any  very 
considerable  quantity  of  liquefied  carbon  dioxide  will  have  accumulated  in 
the  receiver.  When  the  receiver  thus  charged  has  its  stop-cock  opened,  a 
stream  of  the  liquid  is  forcibly  driven  up  the  tube  by  the  elasticity  of  the 
gas  contained  in  the  upper  part  of  the  vessel. 

The  experimenter  incurs  great  personal  danger  in  using  this  apparatus, 
unless  the  utmost  care  be  taken  in  its  management.  A  dreadful  accident 
occurred  in  Paris  by  the  bursting  of  one  of  the  iron  vessels. 

Liquid  carbon  dioxide  is  also  very  frequently  prepared  by  means  of  an 
apparatus  constructed  by  M.  Natterer,  of  Vienna,  which  enables  the  ex- 
perimentalist to  work  with  less  risk.  The  gas  disengaged  by  means  of 
sulphuric  acid  from  acid  potassium  carbonate,  is  pumped  by  means  of  a 
force-pump  into  a  wrought-iron  vessel,  exactly  as  the  air  is  pumped  into 
the  receiver  of  an  air-gun.  When  a  certain  pressure  has  been  reached, 
the  gas  is  liquefied,  and  if  the  pumping  be  continued,  considerable  quan- 
tities of  the  liquid  carbon  dioxide  may  be  thus  obtained.  By  this  appa- 
ratus nitrous  oxide  gas  has  been  condensed  to  a  liquid  without  the  use  of 
frigorific  mixtures. 

The  cold  produced  by  evaporation  has  been 
already  adverted  to:  it  is  simply  an  effect 
arising  from  the  conversion  of  sensible  heat 
into  latent  by  the  rising  vapor,  and  it  may  be 
illustrated  in  a  variety  of  ways.  Ether  drop- 
ped on  the  hand  thus  produces  the  sensation 
of  great  cold;  and  water  contained  in  a  thin 
glass  tube,  surrounded  by  a  bit  of  rag,  is 
speedily  frozen  when  the  rag  is  kept  wetted 
with  ether. 

When  a  little  water  is  put  into  a  watch-glass,  supported  by  a  triangle  of 
wire  over  a  shallow  glass  dish  of  sulphuric  acid  placed  on  the  plate  of  a 
good  air-pump,  the  whole  covered  with  a  low  receiver,  and  the  air  with- 
drawn as  perfectly  as  possible,  the  water  is  in  a  few  minutes  converted 
into  a  solid  mass  of  ice.  The  absence  of  the  impediment  of  the  air,  and 
the  rapid  absorption  of  watery  vapor  by  the  oil  of  vitriol,  induce  such 
quick  evaporation  that  the  water  has  its  temperature  almost  immediately 
reduced  to  the  freezing-point. 

The  same  fact  is  shown  by  Wollaston's  cryophorus,  or  frost-carrier.  It 
is  a  glass  vessel  of  the  figure  represented  in  fig.  47.  and  contains  a  small 
quantity  of  water,  the  rest  of  the  space  being  vacuous.  When  all  the 
water  is  turned  into  the  bulb,  and  the  empty  extremity  plunged  into  a 
mixture  of  ice  and  salt,  the  solidification  of  the  vapor  gives  rise  to  so  quick 
an  evaporation  from  the  surface  of  the  water,  that  the  latter  freezes. 

Fig.  47. 


All  means  of  producing  artificial  cold  yield  to  that  derived  from  the  eva- 
poration of  the  liquefied  carbon  dioxide  just  mentioned.  When  a  jet  of 
that  liquid  is  allowed  to  issue  into  the  air  from  a  narrow  aperture,  so  intense 
a  degree  of  cold  is  produced  by  the  evaporization  of  a  part,  that  the  re- 
mainder freezes  to  a  solid,  and  falls  in  a  shower  of  snow.  By  suffering  this 
jet  of  liquid  to  flow  into  a  metal  box  provided  for  the  purpose,  shown  in 


HEAT. 


69 


fig.  45,  a  large  quantity  of  the  solid  oxide  may  be  obtained:  it  closely  re- 
sembles snow  in  appearance,  and  when  held  in  the  hand  occasions  a  painful 
sensation  of  cold,  while  it  gradually  disappears.  When  it  is  mixed  with  a 
little  ether,  and  poured  upon  a  mass  of  mercury,  the  latter  is  almost  in- 
stantly frozen,  and  in  this  way  pounds  of  the  solidified  metal  may  be  ob- 
tained. The  addition  of  the  ether  facilitates  the  contact  of  the  carbon 
dioxide  with  the  mercury. 

The  temperature  of  a  mixture  of  solid  carbon  dioxide  and  ether  in  the 
air,  measured  by  a  spirit-thermometer,  was  found  to  be — 106°  F. ;  when  the 
same  mixture  was  placed  beneath  the  receiver  of  an 
air-pump,  and  exhaustion  rapidly  made,  the  tem- 
perature sank  to  — 160°  F.  This  was  the  method 
of  obtaining  extreme  cold  employed  by  Mr.  Far- 
aday in  his  last  experiments  on  the  liquefaction 
of  gases.  Under  such  circumstances  the  liquefied 
hydriodic  and  hydrobromic  acids,  sulphur  diox- 
ide, carbon  dioxide,  nitrogen  monoxide,  hydrogen 
sulphide,  cyanogen,  and  ammonia,  froze  to  color- 
less transparent  solids,  and  alcohol  became  thick 
and  oily. 

The  principle  of  the  cryophorus  has  been  very 
happily  applied  by  Mr.  Daniell  to  the  construction 
of  a  dew-point  hygrometer,  fig.  48.  It  consists 
of  a  bent  glass  tube  terminated  by  two  bulbs,  one 
of  which  is  half  filled  with  ether,  the  whole  being 
vacuous  as  respects  atmospheric  air.  A  delicate 
thermometer  is  contained  in  the  longer  limb,  the 
bulb  of  which  dips  into  the  ether;  a  second  ther- 
mometer on  the  stand  serves  to  show  the  actual 
temperature  of  the  air.  The  upper  bulb  is  cov- 
ered with  a  bit  of  muslin.  When  an  observation 
is  to  be  made,  the  liquid  is  all  transferred  to  the 
lower  bulb,  and  ether  dropped  upon  the  upper 
one,  until  by  the  cooling  effect  of  evaporation  a  distillation  of  the  contained 
liquid  takes  place  from  one  part  of  the  apparatus  to  the  other,  by  which 
such  a  reduction  of  temperature  of  the  ether  is  brought  about  that  dew  is 
deposited  on  the  outside  of  the  bulb,  which  is  made  of  black  glass  in  order 
.that  it  may  be  more  easily  seen.  The  difference  of  temperature  indicated 
by  the  two  thermometers  is  then  read  off. 


SPECIFIC  HEAT. 

It  is  a  very  remarkable  fact  that  equal  weights  of  different  substances 
having  the  same  temperature  require  different  amounts  of  heat  to  raise 
them  to  a  given  degree  of  temperature.  If  1  Ib.  of  water,  at  100°,  be 
mixed  with  1  Ib.  at  40°,  then,  as  is  well  known,  a  mean  temperature 

100  4-  40 
of ~ —  ~0  is  obtained.     In  the  same  way  the  mean  temperature  is 

found  when  warm  and  cold  oil,  or  warm  and  cold  mercury,  &c.,  are  mixed 
together.  But  if  1  Ib.  of  water  at  100°  be  mixed  with  1  Ib.  of  olive  oil  at 
40°,  or  with  1  Ib.  of  mercury  at  40°,  then  instead  of  the  mean  temperature 
of  70°,  in  the  one  case  80°,  in  the  other  case  98°,  will  be  obtained:  20 
degrees  of  heat,  which  the  water  (by  cooling  from  100°  to  80°)  gave  to  the 
same  weight  of  oil,  were  sufficient  to  raise  the  oil  40°,  that  is,  from  40°  to 
80° ;  and  2°,  which  the  water  lost  by  cooling  from  100°  to  98°,  sufficed  to 
heat  an  equal  quantity  of  mercury  58°,  namely,  from  40°  to  98°. 


70  HEAT. 

It  is  evident  from  these  experiments  that  the  quantities  of  heat  which 
equal  weights  of  water,  olive  oil,  and  mercury,  require  to  raise  their  tem- 
perature to  the  same  height,  are  unequal,  and  that  they  are  in  the  propor- 
tion of  the  numbers  1  :  f  £  :  •£%,  or  1  :  1  :  J^-. 

These  quantities  of  heat,  expressed  relatively  to  the  quantity  of  heat  re- 
quired to  raise  the  temperature  of  an  equal  weight  of  water  from  0°  to  1° 
C.,  are  called  the  specific  heats  of  the  various  substances:  thus  the  ex- 
periments just  described  show  that  the  specific  heat  of  olive  oil  is  |-,  that 
is  to  say,  the  quantity  of  heat  which  would  raise  the  temperature  of  any 
given  quantity  of  olive  oil  from  0°  to  1°  would  raise  that  of  an  equal  weight 
of  water  only  from  0°  to  |-°,  or  of  half  that  quantity  of  water  from  0° 
to  1°. 

The  specific  heats  of  bodies  are  sometimes  said  to  measure  their  relative 
capacities  for  heat. 

There  are  three  distinct  methods  by  which  the  specific  heats  of  various 
substances  may  be  estimated.  The  first  of  these  is  by  observing  the  quantity 
of  ice  melted  by  a  given  weight  of  the  substance  heated  to  a  particular 
temperature;  the  second  is  by  noting  the  time  which  the  heated  body  re- 
quires to  cool  down  through  a  certain  number  of  degrees;  and  the  third  is 
the  method  of  mixture,  on  the  principle  illustrated:  this  latter  method  is 
preferred  as  the  most  accurate. 

The  determination  of  the  specific  heat  of  different  substances  has  oc- 
cupied the  attention  of  many  experimenters;  among  these,  Dulong  and 
Petit,  and  recently  Regnault  and  Kopp,  deserve  especial  mention. 

From  the  observation  of  these  and  other  physicists,  it  follows  that  each 
body  has  its  peculiar  specific  heat,  and  that  the  specific  heat  increases 
with  increase  of  temperature.  If,  for  example,  the  heat  which  the  unit 
of  water  loses  by  cooling  from  10°  to  0°  be  marked  at  10°,  then  the  loss  by 
cooling  from  50°  to  0°  \\ill  be,  not  50,  corresponding  to  the  difference  of 
temperature,  but  50-1.  By  cooling  from  100°  to  0°  it  is  100-5,  and  rises  to 
203-2  when  the  water  is  heated  under  great  pressure  to  200°  and  afterwards 
cooled  to  0°.  Similar  and  even  more  striking  differences  have  been  found 
with  other  substances.  It  has  also  been  proved  that  the  specific  heat  of 
any  substance  is  greater  in  the  liquid  than  in  the  solid  state.  For  example, 
the  specific  heat  of  ice  is  0-504,  that  is,  not  more  than  half  as  great  as  that 
of  liquid  water. 

It  is  remarkable  that  the  specific  heat  of  water  is  greater  than  that  of 
all  other  solid  and  liquid  substances,  and  is  only  exceeded  by  that  of 
hydrogen.  The  specific  heat  of  the  solid  parts  of  the  crust  of  the  globe  is 
on  an  average  i,  and  that  of  an  atmosphere  nearly  1  that  of  water. 

If  the  specific  heat  of  any  body  within  certain  degrees  of  temperature  be 
accurately  known,  then  from  the  quantity  of  heat  which  this  body  gives  out 
when  quickly  dipped  into  cold  water,  the  temperature  to  the  which  the  body 
was  heated  may  be  determined.  Pouillet  has  founded  on  this  fact  a  method 
of  measuring  high  temperatures,  and  for  this  purpose,  with  the  help  of 
the  air-thermometer,  he  has  determined  the  specific  heat  of  platinum  up 
to  1600°. 

The  determination  of  the  specific  heat  of  gases  is  attended  with  peculiar 
difficulties,  on  account  of  the  comparatively  large  volume  of  small  weights 
of  gases.  For  many  gases,  however,  satisfactory  results  have  been  ob- 
tained by  the  method  of  mixing. 

When  a  gas  expands,  heat  becomes  latent.  The  amount  of  heat  required, 
therefore,  to  raise  a  gas  to  any  given  temperature  increases  the  more  the 
gas  in  question  is  allowed  to  expand.  The  quantity  of  heat  which  the 
unit-weight  of  a  gas  requires  in  order  to  raise  its  temperature  1°  without 
its  volume  undergoing  any  change  (which  can  only  take  place  by  the  pres- 
sure being  simultaneously  augmented)  is  called  the  specific  heat  of  the 


HEAT.  71 

gas  at  constant  volume.  The  quantity  of  heat  required  by  the  unit-weight 
of  a  gas  to  raise  its  temperature  1°,  it  being  at  the  same  time  allowed  to 
dilate  to  such  an  extent  that  the  pressure  to  which  it  is  exposed  remains 
unchanged,  is  called  the  specific  heat  of  the  gas  at  constant  pressure.  Ac- 
cording to  what  has  already  been  stated,  the  specific  heat  at  constant  pres- 
sure must  be  greater  than  that  at  constant  volume.  Dulong  found,  in  the 
case  of  atmospheric  air,  of  oxygen,  of  hydrogen,  and  of  nitrogen,  that  the 
two  specific  heats  are  in  the  proportion  1-421  :  1.  For  carbon  monoxide, 
however,  he  obtained  the  proportion  of  1-423,  for  carbon  dioxide  1-337,  for 
nitrogen  dioxide  1-343,  and  for  olefiant  gas  1-24  to  1.  The  exact  determi- 
nation of  these  ratios  is  extremely  difficult,  and  the  results  of  different 
physicists  by  no  means  agree. 

The  first  satisfactory  comparison  of  the  specific  heat  of  air  with  that  of 
water  was  made  by  Count  Rumford;  later  comparisons  of  the  specific  heat 
of  various  gases  have  been  made  by  Delaroche  and  Berard,  Dulong  and 
Hegnault. 

The  first  researches  of  Delaroche  and  Berard  furnished  the  results  em- 
bodied in  the  following  table:  — 

SPECIFIC  HEAT. 


Atmospheric  air     . 
Oxygen 
Hydrogen 
Nitrogen     . 
Carbon  monoxide  . 
Nitrogen  monoxide 
Carbon  dioxide 
Olefiant  gas 


Equal  volumes.  Equal  weights. 

The  volumes            Tin-  pressure  Air  —  1.  \Vater  —  1. 
constant.                 coustaut. 

1  .         1  0-26G9 

1  .         0-9045  0-2414 

1  .       14-4510  3-8569 

1  .         1-0295  0-2748 

1  .         1-0337  0-2759 

•227         .         1-160  .         0-7607  0-2030 

•249         .         1-175  .         0-7685  0-2051 

754                  1-531  1-5829  0-4225 


The  latest  and  most  trustworthy  determinations  are  those  of  Regnault, 
which  are  given  in  the  subjoined  table.  Its  second  column  of  figures, 
headed  "For  equal  weights.  Water  =  1,"  contains  the  specific  heats  of 
the  gases  under  constant  pressure,  that  of  water  being  taken  equal  to  1. 
As  it  is  both  useful  and  interesting  to  compare  the  quantities  of  heat  which 
gases,  having  equal  volumes  at  0°  and  760  mm.,  require  to  raise  them  1°,  the 
pressure  remaining  constant,  they  have  been  given  under  the  head  "For 
equal  volumes  "  in  the  third  column  of  the  table,  wherein,  it  should  be  stated, 
the  unit  of  heat,  is  the  amount  of  heat  required  to  heat  a  unit-weight  of 
water  1°,  while  the  unit  of  volume  is  the  volume  of  a  unit-weight  of  air  at 
0°  and  760  mm.  The  first  column  gives  the  specific  gravity  of  the  gases  re- 
ferred to  air  as  1. 

SPECIFIC  HEAT  AT  CONSTANT  PRESSURE. 

Specific  Gravity.        For  equal  weights.          For  equal 
Gases.  Air  —  1.  Water  =  1.  volumes. 

Atmospheric  air     ...  1  .  0  2377  .  0-2377 

Oxygen 1-1056  .  0-2175  .  02405 

Nitrogen         ....  0-9713  .  02438  .  0.2368 

Hydrogen 0-0692  .  3-4090  .  0-2359 

Chlorine          ....  2-4502  .  0-1210  .  02965 

Bromine  vapor ....  5-4772  .  0-0555  .  0-3040 

Carbon  monoxide  .         .         .  0-9670  .  0-2450  .  0-2370 

Carbon  dioxide           .         .  1-5210  .  0-2169  .  0-3307 


72 


HEAT. 


Specific  Gravity. 

Gases.  Air  =  1. 

Nitrogen  monoxide     .         .         .  1-5241 

Nitrogen  dioxide    .         .         .  1-0384 

Olefiant  gas        ....  0-9672 

Marsh  gas      .         .         .         .  0-5527 

Aqueous  vapor  ....  0-6220 

Sulphuretted  hydrogen .         .  1-1746 

Sulphur  dioxide          .         .  2-2112 

Vapor  of  carbon  bisulphide      .  2-6258 

Hydrochloric  acid         .         .  1-2596 

Ammonia  .....  0-5894 


For  equal  weights.        For  equal 
Water  ^  1.  volumes. 


0-2262 
0-2317 
0-4040 
0-5929 
0-4805 
0-2432 
0-1544 
0-1569 
01852 
0-5084 


0-3447 
0-2406 
0-4106 
0-3277 
0-2989 
0-2857 
0-3414 
0-4122 
0-2333 
0-2996 


The  researches  of  Delaroche  and  Berard  led  them  to  suppose  that  the 
specific  heat  of  gases  increased  rapidly  as  the  temperature  was  raised,  and 
that  for  a  given  volume  of  gas  it  increased  in  proportion  to  the  density  or 
tension  of  the  gas.  Regnault  found,  however,  the  quantity  of  heat  which  a 
given  volume  of  gas  requires  to  raise  it  to  a  certain  temperature,  to  be  in- 
dependent of  its  density ;  and  that  for  each  degree  between  —  30°  and  225° 
it  is  constant.  Carbon  dioxide,  however,  forms  an  exception  to  this  rule,  its 
specific  heat  increasing  with  the  temperature.  Regnault  believes  that  other 
gases  agree  with  carbon  dioxide  in  showing  this  anomaly,  but  he  has  not 
established  it  by  experiment.  In  the  table,  mean  values  for  temperatures 
between  10°  and  200°  have  been  given. 

Several  physicists  have  held  that  the  specific  heats  of  elementary  gases, 
referred  to  equal  volumes,  are  identical.  The  numbers  which  Regnault 
found  for  chlorine  and  bromine,  however,  show  that  the  law  does  not  hold 
good  for  all  elementary  gases. 

It  has  been  already  stated  that,  when  a  gas  expands,  heat  becomes  latent. 
If  a  gas  on  expanding  be  not  supplied  with  the  requisite  heat,  its  tempera- 
ture falls  on  account  of  its  own  free  heat  becoming  latent.  On  the  other 
hand,  if  a  gas  be  compressed,  this  latent  heat  becomes  free,  and  causes  an 
elevation  of  temperature, '  which,  under  favorable  circumstances,  may  be 
raised  to  ignition :  syringes  by  which  tinder  is  kindled  are  constructed  on 
this  principle. 

Dulong  and  Petit  observed  in  the  course  of  their  investigation  a  most  re- 
markable circumstance.  If  the  specific  heats  of  bodies  be  computed  upon 
equal  weights,  numbers  are  obtained  all  different,  and  exhibiting  no  simple 
relations  among  themselves;  but  if,  instead  of  equal  weights,  quantities  be 
taken  in  the  proportion  of  the  atomic  weights,  an  almost  perfect  coinci- 
dence in  the  numbers  will  be  observed,  showing  that  some  exceeding  inti- 
mate connection  must  exist  between  the  relations  of  bodies  to  heat  and 
their  chemical  nature;  and  when  the  circumstance  is  taken  into  view, 
that  relations  of  even  a  still  closer  kind  link  together  chemical  and 
electrical  phenomena,  it  is  not  too  much  to  expect  that  ere  long  some  law 
may  be  discovered  far  more  general  than  any  with  which  we  are  yet  ac- 
quainted. 

In  the  following  table  the  elementary  bodies  are  arranged  nearly 
in  the  order  of  their  specific  heats,  as  determined  by  Regnault,  begin- 
ning with  those  whose  specific  heat  is  the  greatest;  and  this  order,  it 
will  be  observed,  is  the  inverse  of  that  of  the  atomic  weights  in  the  third 
column :  — 


HEAT. 


73 


Specific  Heats  of  Elementary  Bodies. 


r 

Elements. 

Specific  Heat 
(that  of 
Water=l). 

Atomic 
Weights. 

Product  of 
Sp.  Heat  X 
At.  Weight. 

Lithium  .... 

09408 

7 

6-59 

Sodium 

0.2934 

23 

6-75 

Aluminium 

0-2143 

27.5 

5-89 

Phosphorus^'   '    < 

0-2120 

0-1887 

}    3>    { 

657 
5-85 

Sulphur 

0-2026 

32 

6-48 

Potassium 

0-1696 

39 

6-61 

Iron    .... 

0-1138 

56 

6-37 

Nickel     .... 

0-1086 

58-7 

6-37 

Cobalt 

0-1070 

58-7 

6-28 

Copper    .... 

0-9515 

63-5 

6-04 

Zinc    .... 

0-9555 

65 

6-24 

Arsenic  .... 

0-8140 

75 

6-10 

Selenium 

0-7616 

79 

6-02 

Bromine  (solid) 

0-8432 

80 

6-75 

Palladium   . 

0-5928 

106-5 

6-31 

Silver      .... 

0-5701 

108 

6-16 

Cadmium    . 

0-5669 

112 

6.35 

Tin          . 

05623 

118 

6-63 

Antimony    . 

0-5077 

122 

6-19 

Iodine     .... 

0-5412 

127 

6-87 

Tellurium  . 

0-4737 

128 

6-06 

Gold        .... 

0-3242 

196-7 

6-38 

Platinum     . 

0-3113 

197-4 

6-15 

««•«*{£$*   '  .  ' 

0-3192 
0-3332 

}     200       { 

6-38 
6-66 

Lead        .... 

0-3140 

207 

6-50 

Bismuth 

0-3084 

210 

6-48 

A  comparison  of  the  numbers  in  the  fourth  column  of  this  table  shows 
that  for  a  considerable  number  of  elementary  bodies  in  the  solid  state  the 
specific  heats  are  very  nearly  proportional  to  the  atomic  weights,  so  that 
the  products  of  the  specific  heats  of  the  elements  into  their  atomic  weights 
give  nearly  a  constant  quantity,  the  mean  value  being  6-4.  This  quantity 
may  be  taken  to  represent  the  atomic  heat  of  the  several  elements  in  the 
solid  state,  or  the  quantity  of  heat  which  must  be  imparted  to  or  removed 
from  atomic  proportions  of  the  several  elements,  in  order  to  produce  equal 
variations  of  temperature. 

Nevertheless,  this  law  must  not  be  understood  as  perfectly  general,  for 
there  are  three  elements,  namely,  carbon,  boron,  and  silicon,  which  exhibit 
decided  exceptions  to  it,  as  shown  by  the  following  numbers: 
7 


HEAT. 


Elements. 

Specific  Heat. 

Atomic 
Weights. 

Product  of 
Sp.  Heat  X 
At.  Weight. 

Boron,  crystallized 

0-2500 

11 

2-75 

(  wood  charcoal 
Carbon  ^  graphite 
(  diamond  . 

0-2415 
0-2008 
0-1469 

t  "  { 

2-90 
2-41 
1-76 

Si!ic°'>{Sdallized-  . 

0-1774 
0-1750 

)  »  i 

497 
4-70 

The  specific  heats  and  molecular  weights  of  similarly  constituted  com- 
pounds exhibit,  for  the  most  part,  the  same  relation  as  that  which  is  observed 
between  the  specific  heats  and  atomic  weights  of  the  elements. 


SOURCES  OF  HEAT. 

The  first  and  greatest  source  of  heat,  compared  with  which  all  others 
are  totally  insignificant,  is  the  sun.  The  luminous  rays  are  accompanied 
by  rays  of  a  heating  nature,  which,  striking  against  the  surface  of  the  earth, 
elevate  its  temperature ;  this  heat  is  communicated  to  the  air  by  convection, 
as  already  described,  air  and  gases  in  general  not  being  sensibly  heated  by 
the  passage  of  the  rays. 

A  second  source  of  heat  is  supposed  to  exist  in  the  interior  of  the  earth. 
It  has  been  observed  that  in  sinking  mine-shafts,  boring  for  water,  &c.,  the 
temperature  rises  in  descending,  at  the  rate,  it  is  said,  of  about  |°  C.  (1°  F.) 
for  every  45  feet,  or  65°  C.  (117°  F.)  per  mile.  On  the  supposition  that  the 
rise  continues  at  the  same  rate,  the  earth,  of  the  depth  of  less  than  two 
miles,  would  have  the  temperature  of  boiling  water ;  at  nine  miles  it  would 
be  red-hot;  and  at  30  or  40  miles  depth  all  known  substances  would  be  in 
a  state  of  fusion.* 

According  to  this  idea,  the  earth  must  be  looked  upon  as  an  intensely 
heated  fluid  spheroid,  covered  with  a  crust  of  solid  badly  conducting  matter, 
cooled  by  radiation  into  space,  and  bearing  somewhat  the  same  proportions 
in  thickness  to  the  ignited  liquid  within,  that  the  shell  of  an  egg  bears  to 
its  fluid  contents.  Without  venturing  to  offer  any  opinion  on  this  theory,  it 
may  be  sufficient  to  observe  that  it  is  not  positively  at  variance  with  any 
known  fact ;  that  the  figure  of  the  earth  is  really  such  as  would  be  assumed 
by  a  fluid  mass ;  and,  lastly,  that  it  offers  the  best  explanation  we  have  of 
the  phenomena  of  hot  springs  and  volcanic  eruptions,  and  agrees  with  the 
chemical  nature  of  their  products. 

Among  the  other  sources  of  heat  are  chemical  combination  and  mechani- 
cal work. 

The  disengagement  of  heat  in  the  act  of  combination  is  a  phenomenon  of 
the  utmost  generality.  The  quantity  of  heat  given  out  in  each  particular 
case  is  fixed  and  definite;  its  intensity  is  dependent  upon  the  time  over 
which  the  action  is  extended.  Many  admirable  researches  on  this  subject 
have  been  published ;  but  their  results  will  be  more  advantageously  con- 
sidered at  a  later  part  of  this  work,  in  connection  with  the  laws  of  chemical 
combination. 

*  The  Artesian  well  at  Crenelle,  near  Paris,  has  a  depth  of  1794-5  English  feet;  it  is  bored 
through  the  chalk  basin  to  the  sand  beneath.  The  temperature  of  the  water,  which  is  exceed- 
ingly abundant,  is  82°  F.;  the  mean  temperature  of  Paris  is  51°  F.;  the  difference  is  31°  F.; 
which  gives  a  rate  of  about  1°  for  58  feet. 


HEAT.  75 

Heat  produced  by  Mechanical  Work. — Heat  and  motion  are  convertible  one 
into  the  other.  The  powerful  mechanical  effects  produced  by  the  elasticity 
of  the  vapor  evolved  from  heated  liquids  afford  abundant  illustration  of  the 
conversion  of  heat  into  motion ;  and  the  production  of  heat  by  friction,  by 
the  hammering  of  metals,  and  in  the  condensation  of  gases  (p.  72),  shows 
with  equal  clearness  that  motion  may  be  converted  into  heat. 

In  some  cases  the  rise  of  temperature  thus  produced  appears  to  be  due  to 
a  diminution  of  heat-capacity  in  the  body  operated  upon,  as  in  the  case  of 
a  compressed  gas  just  alluded  to.  Malleable  metals,  also,  as  iron  and  copper, 
which  become  heated  by  hammering  or  powerful  pressure,  are  found  thereby 
to  have  their  density  sensibly  increased  and  their  capacity  for  heat  dimin- 
ished. A  soft  iron  nail  may  be  made  red-hot  by  a  few  dexterous  blows  on 
an  anvil;  but  the  experiment  cannot  be  repeated  until  the  metal  has  been 
annealed,  and  in  that  manner  restored  to  its  former  physical  state. 

But  the  amount  of  heat  which  can  be  developed  by  mechanical  force  is, 
in  most  cases,  out  of  all  proportion  to  what  can  be  accounted  for  in  this 
way.  Sir  H.  Davy  melted  two  pieces  of  ice  by  rubbing  them  together  in  a 
vacuum  at  the  temperature  of  0° ;  and  Count  Rumford  found  that  the  heat 
developed  by  the  boring  of  a  brass  cannon  was  sufficient  to  bring  to  the 
boiling-point  two  and  a  half  gallons  of  water,  while  the  dust  or  shavings 
of  metal,  cut  by  the  borer,  weighed  only  a  few  ounces.  In  these  and  all 
similar  cases  the  heat  appears  as  a  direct  result  of  the  force  expended ;  the 
motion  is  converted  into  heat. 

The  connection  between  heat  and  mechanical  force  appears  still  more  in- 
timate when  it  is  shown  that  they  are  related  by  an  exact  numerical  law,  a 
given  quantity  of  the  one  being  always  convertible  into  a  definite  amount 
of  the  other.  The  first  approximate  determination  of  this  most  important 
numerical  relation  was  made  by  Count  Rumford  in  the  manner  just  alluded 
to.  A  brass  cylinder  enclosed  in  a  box  containing  a  known  weight  of  water 
at  60°  F.  was  bored  by  a  steel  borer  made  to  revolve  by  horse-power,  and 
the  time  was  noted  which  elapsed  before  the  water  was  raised  to  the  boiling- 
point  by  the  heat  resulting  from  the  friction.  In  this  manner  it  was  found 
that  the  heat  required  to  raise  the  temperature  of  a  pound  of  water  by  1° 
F.  is  equivalent  to  1034  times  the  force  expended  in  raising  a  pound  weight 
one  foot  high,  or  to  1034  "foot  pounds,"  as  it  is  technically  expressed.  This 
estimate  is  now  known  to  be  too  high,  no  account  having  been  taken  of  the 
heat  communicated  to  the  containing  vessel,  or  of  that  which  was  lost  by 
dispersion  during  the  experiment. 

For  the  most  exact  determinations  of  the  mechanical  equivalent  of  heat 
we  are  indebted  to  the  careful  and  elaborate  researches  of  Mr.  J.  P.  Joule. 
From  experiments  made  in  the  years  1840-43  on  the  relations  between  the 
heat  and  mechanical  power  generated  by  the  electric  current,  Mr.  Joule 
was  led  to  conclude  that  the  heat  required  to  raise  the  temperature  of  a 
pound  of  water  1°  F.  is  equivalent  to  838  foot-pounds;  this  he  afterwards 
reduced  to  772 ;  and  a  nearly  equal  result  was  afterwards  obtained  by  ex- 
periments on  the  condensation  and  rarefaction  of  gases ;  but  this  estimate 
has  since  been  found  to  be  likewise  too  great. 

The  most  trustworthy  results  are  obtained  by  measuring  the  quantity  of 
heat  generated  by  the  friction  between  solids  and  liquids.  It  was  for  a  long 
time  believed  that  no  heat  was  evolved  by  the  friction  of  liquids  and  gases. 
But  in  1842  Meyer  showed  that  the  temperature  of  water  may  be  raised 
22°  or  23°  F.  by  agitating  it.  The  warmth  of  the  sea  after  a  few  days  of 
stormy  weather  is  also  probably  an  effect  of  fluid  friction. 

The  apparatus  employed  by  Mr.  Joule  for  the  determination  of  this  im- 
portant constant,  by  means  of  the  friction  of  water,  consisted  of  a  brass 
paddle-wheel  furnished  with  eight  sets  of  revolving  vanes,  working  between 
four  sets  of  stationary  vanes.  This  revolving  apparatus,  of  which  fig.  49 


76 


HEAT. 


shows 
copper 


Fig.  49. 


Fig.  50. 


motion 
pended 


a  vertical,  and  fig.  50  a  horizontal  section,  was  firmly  fitted  into  a 
vessel  (see  fig.  51)  containing  water,  in  the  lid  of  which  were  two 

necks,  one  for  the  axis  to  revolve  in 
without  touching,  the  other  for  the 
insertion  of  a  thermometer.  A 
similar  apparatus,  but  made  of  iron, 
and  of  smaller  size,  having  six  rota- 
tory and  eight  sets  of  stationary 
vanes,  was  used  for  the  experiments 
on  the  friction  of  mercury.  The 
apparatus  for  the  friction  of  cast- 
iron  consisted  of  a  vertical  axis  car- 
rying a  bevelled  cast-iron  wheel, 
against  which  a  bevelled  wheel  was 
pressed  by  a  lever.  The  wheels 
were  enclosed  in  a  cast-iron  vessel 
filled  with  mercury,  the  axis  passing 
through  the  lid.  In  each  apparatus 

was  given  to  the  axis  by  the  descent  of  leaden  weights  w  (fig.  51)  sus- 
by  strings  from  the  axis  of  two  wooden  pulleys,  one  of  which  is 

Fig.  51. 


TV- 


at  p,  their  axis  being  supported  on  friction  wheels  d  d,  and  the  pulleys 
were  connected  by  fine  twine  with  a  wooden  roller  r,  which,  by  means  of  a 
pin,  could  be  easily  attached  to  or  removed  from  the  friction  apparatus. 

The  mode  of  experimenting  was  as  follows :  —  The  temperature  of  the 
frictional  apparatus  having  been  ascertained,  and  the  weights  wound  up, 
the  roller  was  fixed  to  the  axis,  and  the  precise  height  of  the  weights  as- 
certained; the  roller  was  then  set  at  liberty,  and  allowed  to  revolve  till  the 
weights  touched  the  floor.  The  roller  was  then  detached,  the  weights 
wound  up  again,  and  the  friction  renewed.  This  having  been  repeated 
twenty  times,  the  experiment  was  concluded  with  another  observation  of 
the  temperature  of  the  apparatus.  The  mean  temperature  of  the  apart- 
ment was  ascertained  by  observations  made  at  the  beginning,  middle,  and 
end  of  each  experiment.  Corrections  were  made  for  the  effects  of  radia- 
tion and  conduction;  and,  in  the  experiments  with  water,  for  the  quantities 
of  heat  absorbed  by  the  copper  vessel  and  the  paddle-wheel.  In  the  ex- 
periments with  mercury  and  cast-iron,  the  heat-capacity  of  the  entire  ap- 
paratus was  ascertained  by  observing  the  heating  effect  which  it  produced 
on  a  known  quantity  of  water  in  which  it  was  immersed.  In  all  the  ex- 


HEAT.  77 

periments,  corrections  were  also  made  for  the  velocity  with  which  the 
weights  came  to  the  ground,  and  for  the  friction  and  rigidity  of  the  strings. 
The  thermometers  used  were  capable  of  indicating  a  variation  of  tempera- 
ture as  small  as  ^¥  of  a  degree  Fahrenheit. 

The  following  table  contains  a  summary  of  the  results  obtained  by  this 
method;  the  second  column  gives  the  results  as  they  were  obtaine  in  air; 
in  the  third  column  the  same  results  corrected  for  a  vacuum  :  — 

Material  Equivalent  Equivalent 

employed.  in  air.  in  vacno.  Mean. 

Water       .        .  773-640  772-692  772-692 

Mercury.         .          {™*  ™»|}  774-083 

Cast-iron.         .  ™  ™«  774,87 


In  the  experiments  with  cast-iron,  the  friction  of  the  wheels  produced  a 
considerable  vibration  in  the  frame-work  of  the  apparatus,  and  a  loud 
sound  ;  it  was  therefore  necessary  to  make  allowance  for  the  quantity  of 
force  expended  in  producing  these  effects.  Tae  number  772-692,  obtained 
by  the  friction  of  water,  is  regarded  as  the  most  trustworthy  ;  but  even  this 
may  be  a  little  too  high  ;  because  even  in  the  friction  of  fluids  it  is  impos- 
sible entirely  to  avoid  vibration  and  sound.  The  conclusions  deduced  from 
these  experiments  are:  — 

1.  That  the  quantity  of  heat  produced  by  the  friction  of  bodies,  whether  solid  or 
liquid,  is  always  proportional  to  the  force  expended. 

2.  That  the  quantity  of  heat  capable  of  increasing  the  temperature  of  lib.  of 
wafer  (weighed  in  vacuo,  and  between  55°  and  60°)  by  1°  F.,  requires  for  its  evo- 
lution the  expenditure  of  a  mechanical  force  represented  by  the  fall  of  772lbs. 
through  the  space  of  1  foot. 

Or,  the  heat  capable  of  increasing  the  temperature  ofl  gram  of  water  by  1°  C., 
is  equivalent  to  a  force  represented  by  the  fall  of  423-55  grams  through  the  space 
of  1  metre.  This  is  consequently  the  effect  of  "  a  unit  of  heat.  ^ 

Experiments  made  by  other  philosophers  on  the  work  done  by  a  steam- 
engine,  on  the  heat  evolved  by  an  electro-magnetic  engine  at  rest  and  in 
motion,  and  on  the  he.at  evolved  in  the  circuit  of  a  voltaic  battery  and  in  a 
metallic  wire  through  which  an  electric  current  is  passing,  have  given  values 
for  the  mechanical  equivalent  of  heat  very  nearly  equal  to  the  above. 

DYNAMICAL  THEORY  OF  HEAT. 

For  a  very  long  time  two  rival  theories  have  been  held  regarding  the 
nature  of  heat:  on  the  one  hand,  heat  has  been  viewed  as  having  a  material 
existence,  though  differing  from  ordinary  matter  in  being  without  weight, 
and  in  other  respects;  on  the  other  hand,  it  has  been  regarded  as  a  state 
or  condition  of  ordinary  matter,  and  generally  as  a  condition  of  motion. 
From  the  latter  part  of  the  last  century,  until  the  modern  researches  upon 
the  mechanical  equivalent,  the  former  view  had  by  far  the  greater  number 
of  adherents.  Its  popularity  may  be  chiefly  traced  to  the  teaching  of  Black 
and  Lavoisier.  By  the  former  of  these  philosophers,  the  various  capacities 
for  heat,  or  specific  heats  of-  different  bodies,  seem  to  have  been  regarded 
as  analogous  to  the  various  proportions  of  the  same  acid  required  to  neu- 
tralize equal  quantities  of  different  bases,  while  the  solid,  liquid,  and 
gaseous  states  were  explained  by  Black  as  representing  so  many  distinct 
proportions  in  which  heat  was  capable  of  combining  with  ordinary  matter. 
Very  similar  views  were  advocated  by  Lavoisier:  he  regarded  all  gases  as 
compounds  of  a  base  characteristic  of  each,  with  caloric,  and  supposed  that 
when,  as  the  result  of  chemical  action,  they  assumed  the  liquid  or  solid 
state,  this  caloric  was  set  free  and  appeared  as  sensible  heat. 
7* 


78  HEAT. 

Heat  was  compared  by  these  philosophers  to  a  material  substance,  in  order 
to  explain  its  then  known  quantitative  relations ;  and  from  this  point  of 
view  the  conception  introduced  by  them  had  the  great  advantage  of  being 
more  easily  grasped  than  any  which  the  advocates  of  the  immaterial  nature 
of  heat  had  to  offer  in  its  place.  It  was  much  easier  to  conceive  of  definite 
quantities  of  an  exceedingly  subtile  substance  or  fluid,  than  of  definite 
quantities  of  motion,  which  was  itself  undefined  as  to  its  nature.  It  was  a 
direct  consequence  of  the  material  view,  that  heat  should  be  considered  as 
indestructible  and  as  incapable  of  being  produced,  and  therefore  that  the 
total  quantity  of  heat  in  the  universe  should  be  regarded  as  at  all  times  the 
same. 

But,  on  the  other  hand,  this  hypothesis  did  not  afford  a  satisfactory  ex- 
planation of  the  production  of  heat  by  mechanical  means.  Here  it  was  not 
easy  to  deny  the  actual  generation  of  heat,  or  to  explain  the  effects  as  de- 
pending merely  on  its  altered  distribution.  Nevertheless,  the  evolution  of 
heat  by  friction  and  percussion  was  generally  considered,  by  the  advocates 
of  the  material  view,  as  in  some  way  resulting  from  a  diminution  in  the 
capacities  for  heat  of  the  bodies  operated  upon ;  and  this  explanation  de- 
rived considerable  support  from  the  remark,  made  by  Black,  that  a  piece 
of  soft  iron,  which  has  been  once  made  red-hot  by  hammering  (see  p.  75), 
cannot  be  so  heated  a  second  time  until  it  has  been  heated  to  redness  in  a 
fire  and  allowed  to  cool.  In  this  case,  certainly,  it  seemed  as  though  the 
hammering  forced  out  heat  from  the  mass  of  iron,  like  water  from  a  sponge, 
and  that  a  fresh  supply  was  taken  up  when  the  iron  was  put  in  the  fire. 
This  explanation,  however,  did  not  satisfy  Rumford,  who,  in  the  investi- 
gation described  above,  made  direct  experiments  upon  the  specific  heat  of 
the  chips  of  metal  detached  by  the  friction,  and  found  it  to  be  identical  with 
that  of  brass  under  ordinary  circumstances.  Still  more  decisive  proof  that 
the  heat  generated  by  friction  cannot  be  ascribed  to  a  diminution  of  specific 
heat  in  the  substances  operated  on  was  afforded  by  Davy's  experiment  on 
the  liquefaction  of  ice  by  friction ;  for  in  this  case  the  ice  was  converted 
into  a  liquid  having  twice  the  specific  heat  of  the  ice  itself.  Hence  Davy  * 
drew  the  conclusion  that,  "The  immediate  cause  of  the  phenomena  of  heat 
is  motion,  and  the  laws  of  its  communication  are  precisely  the  same  as  the 
laws  of  the  communication  of  motion." 

The  mechanical,  or  dynamical  theory,  which  regarded  heat  as  consisting 
in  a  state  of  molecular  motion,  cannot  however  be  said  to  have  been  defi- 
nitely established,  until  it  also  was  made  quantitative, — until  it  was  shown 
that  exact  numerical  laws  regulate  the  production  of  heat  by  work  or  of 
work  by  heat,  equally  with  its  production  during  solidification  and  disap- 
pearance during  fusion. 

To  illustrate  the  general  nature  of  the  dynamical  theory  of  heat,  we 
give  an  outline  of  the  view  of  the  constitution  of  gases,  first  put  forward, 
in  its  present  form,  by  Joule ;  f  and  subsequently  developed  by  Kronig,J 
and  Clausius,$  and  of  the  explanation  of  the  relations  existing  between 
solids,  liquids,  and  gases,  which  has  been  deduced  from  it  by  the  last-named 
philosopher. 

First,  then,  it  is  assumed  that  the  particles  of  all  bodies  are  in  constant 
motion,  and  that  this  motion  constitutes  heat,  the  kind  and  quantity  of  mo- 
tion varying  according  to  the  state  of  the  body,  whether  solid,  liquid,  or 
gaseous. 

In  gases,  the  molecules  —  each  molecule  being  an  aggregate  of  atoms  — 
are  supposed  to  be  constantly  moving  forward  in  straight  lines,  and  with  a 

*  Elements  of  Chemical  Philosophy,  1812,  pp.  94,  95.  f  Ann.  Ch.  Phys.  [3]  1.  381. 

J  Pogg.  Ann.  xcix.  315.  \  Ibid.  353. 


HEAT.  79 

constant  velocity,  till  they  impinge  against  each  other,  or  against  an  im- 
penetrable wall.  This  constant  impact  of  the  molecules  produces  the  ex- 
pansive tendency  or  elasticity  which  is  the  peculiar  characteristic  of  the 
pisrous  state.  The  rectilinear  movement  is  not,  however,  the  only  one  with 
which  the  particles  are  affected.  For  the  impact  of  two  molecules,  unless 
it  takes  place  exactly  in  the  line  joining  their  centres  of  gravity,  must  give 
rise  to  a  rotatory  motion;  and,  moreover,  the  ultimate  atoms  of  which  the 
molecules  are  composed  may  be  supposed  to  vibrate  within  certain  limits, 
being,  in  fact,  thrown  into  vibration  by  the  impact  of  the  molecules.  This 
vibratory  motion  is  called  by  Clausius,  the  motion  of  the  constituent  atoms. 
The  total  quantity  of  heat  in  the  gas  is  made  up  of  the  progressive  motion 
of  the  molecules,  together  with  the  vibratory  and  other  motions  of  the  con- 
stituent atoms;  but  the  progressive  motion  alone,  which  is  the  cause  of  the 
expansive  tendency,  determines  the  temperature,  Now,  the  outward  pressure 
exerted  by  the  gas  against  the  containing  envelope  arises,  according  to  the 
hypothesis  under  consideration,  from  the  impact  of  a  great  number  of 
gaseous  molecules  against  the  sides  of  the  vessel.  But  at  any  given  tem- 
perature, that  is,  with  any  given  velocity,  the  number  of  such  impacts  taking 
place  in  a  given  time,  must  vary  inversely  as  the  volume  of  the  given  quan- 
tity of  gas ;  hence  the  pressure  varies  inversely  as  the  volume  or  directly  as  the 
density,  which  is  Boyle's  law. 

When  the  volume  of  the  gas  is  constant,  the  pressure  resulting  from  the 
impact  of  the  molecules  is  proportional  to  the  sum  of  the  masses  of  all  the 
molecules  multiplied  into  the  squares  of  their  velocities;  in  other  words,  to 
the  so-called  vis  viva  or  working  force  of  the  progressive  motion.  If,  for  ex- 
ample, the  velocity  be  doubled,  each  molecule  will  strike  the  sides  of  the 
vessel  with  a  twofold  force,  and  its  number  of  impacts  in  a  given  time  will 
also  be  doubled :  hence  the  total  pressure  will  be  quadrupled. 

Now,  we  know  that  when  a  given  quantity  of  any  perfect  gas  is  main- 
tained at  a  constant  volume,  it  tends  to  expand  by  ^y-g-  of  its  bulk  at  zero 
for  each  degree  Centigrade.  Hence  the  pressure  or  elastic  force  increases 
proportionally  to  the  temperature  reckoned  from  — 273°  C. ;  that  is  to  say, 
to  the  absolute  temperature.  Consequently,  the  absolute  temperature  is  pro- 
portional to  the  working  force  of  the  progressive  motion. 

Moreover,  as  the  motions  of  the  constituent  particles  of  a  gas  depend  on 
the  manner  in  which  its  atoms  are  united,  it  follows  that  in  any  given  gas 
the  different  motions  must  be  to  one  another  in  a  constant  ratio ;  and,  there- 
fore, the  vis  viva  or  working  force  of  the  progressive  motion  must  be  an 
aliquot  part  of  the  entire  working  force  of  the  gas:  hence  also  the  absolute 
temperature  is  proportional  to  the  total  working  force  arising  from  all  the 
motions  of  the  particles  of  the  gas. 

From  this  it  follows  that  the  quantity  of  heat  which  must  be  added  to  a 
gas  of  constant  volume  in  order  to  raise  its  temperature  by  a  given  amount, 
is  constant  and  independent  of  the  temperature.  In  other  words,  the 
specific  heat  of  a  gas  referred  to  a  given  volume  is  constant,  a  result  which 
agrees  with  this  experiments  of  Regnault,  mentioned  at  p.  72.  The  result 
may  be  otherwise  expressed,  as  follows :  —  The  total  or  working  force  of  ihe 
gas  is  to  the  ivorking  force  of  the  progressive  motion  of  Ihe  molecules,  which  is  the 
measure  of  the  temperature,  in  a  constant  ratio.  This  ratio  is  different  for  dif- 
ferent gases,  and  is  greater  as  the  gas  is  more  complex  in  its  constitution : 
in  other  words,  as  its  molecules  are  made  up  of  a  greater  number  of -atoms. 
The  specific  heat  referred  to  a  constant  pressure  is  known  to  differ  from  the 
true  specific  heat  only  by  a  constant  quantity. 

The  relations  just  considered  between  the  pressure,  volume,  and  temper- 
ature of  gases,  presuppose,  however,  certain  conditions  of  molecular  con- 
stitution, which  are,  perhaps,  never  rigidly  fulfiled ;  and.  accordingly,  Ilie 
experiments  of  Magnus  and  Regnault  show  (p.  52)  that  gases  do  exhibit 


80  HEAT. 

slight  deviations  from  Gay-Lussac  and  Boyle's  laws.  What  the  conditions 
are  which  strict  adherence  to  these  laws  would  require,  will  be  better  under- 
stood by  considering  the  differences  of  molecular  constitution  which  must 
exist  in  the  solid,  liquid,  and  gaseous  states. 

A  movement  of  molecules  must  be  supposed  to  exist  in  all  three  states. 
In  the  solid  state,  the  motion  is  such  that  the  molecules  oscillate  about 
certain  positions  of  equilibrium,  which  they  do  not  quit,  unless  they  are 
acted  upon  by  external  forces.  This  vibratory  motion  may,  however,  be  of 
a  very  complicated  character.  The  constituent  atoms  of  a  molecule  may 
vibrate  separately;  the  entire  molecules  may  also  vibrate  as  such  about 
their  centres  of  gravity,  and  the  vibrations  may  be  either  rectilinear  or 
rotatory.  Moreover,  when  extraneous  forces  act  upon  the  body,  as  in 
shocks,  the  molecules  may  permanently  alter  their  relative  positions. 

In  the  liquid  state  the  molecules  have  no  determinate  positions  of  equili- 
brium. They  may  rotate  completely  about  their  centres  of  gravity,  and 
may  also  move  forward  into  other  positions.  But  the  repulsive  action 
arising  from  the  motion  is  not  strong  enough  to  overcome  the  mutual  attrac- 
tion of  the  molecules  and  separate  them  completely  from  each  other,  A 
molecule  is  not  permanently  associated  with  its  neighbors,  as  in  the  solid 
state;  it  does  not  leave  them  spontaneously,  but  only  under  the  influence 
offerees  exerted  upon  it  by  other  molecules,  with  which  it  then  comes  into 
the  same  relation  as  with  the  former.  There  exists,  therefore,  in  the  liquid 
state,  a  vibratory,  rotatory,  and  progressive  movement  of  the  molecules,  but 
so  regulated,  that  they  are  not  thereby  forced  asunder,  but  remain  within 
a  certain  volume  Avithout  exerting  any  outward  pressure. 

In  the  gaseous  state,  on  the  other  hand,  the  molecules  are  removed  quite 
beyond  the  sphere  of  their  mutual  attractions,  and  travel  onward  in  straight 
lines  according  to  the  ordinary  laws  of  motion.  When  two  such  molecules 
meet,  they  fly  apart  from  each  other,  for  the  most  part  with  a  velocity 
equal  to  that  with  which  they  came  together.  The  perfection  of  the  gaseous 
state,  however,  implies:  — 1.  That  the  space  actually  occupied  by  the  mole- 
cules of  the  gas  be  infinitely  small  in  comparison  with  the  entire  volume  of 
the  gas. — 2.  That  the  time  occupied  in  the  impact  of  a  molecule,  either 
against  another  molecule  or  against  the  sides  of  the  vessel,  be  infinitely 
small  in  comparison  with  the  interval  between  any  two  impacts.  —  3.  That 
the  influence  of  the  molecular  forces  be  infinitely  small.  When  these  con- 
ditions are  not  completely  fulfilled,  the  gas  partakes  more  or  less  of  the 
nature  of  a  liquid,  and  exhibits  certain  deviations  from  Gay-Lussac  and 
Boyle's  laws.  Such  is,  indeed,  the  case  with  all  known  gases;  to  a  very 
slight  extent  with  those  which  have  not  yet  been  reduced  into  the  liquid 
state ;  but  to  a  greater  extent  with  vapors  and  condensable  gases,  especially 
near  the  points  of  condensation. 

Let  us  now  return  to  the  consideration  of  the  liquid  state.  It  has  been 
said  that  the  molecule  of  a  liquid,  when  it  leaves  those  with  which  it  is  as- 
sociated, ultimately  takes  up  a  similar  position  with  regard  to  other  mole- 
cules. This,  however,  does  not  preclude  the  existence  of  considerable  ir- 
regularities in  the  actual  movements.  Now,  at  the  surface  of  the  liquid,  it 
may  happen  that  a  particle,  by  a  peculiar  combination  of  the  rectilinear, 
rotatory,  and  vibratory  movements,  may  be  projected  from  the  neighboring 
molecules  with  such  force  as  to  throw  it  completely  out  of  their  sphere  of 
action*  before  its  projectile  velocity  can  be  annihilated  by  the  attractive 
force  which  they  exert  upon  it.  The  molecule  will  then  be  driven  forward 
into  the  space  above  the  liquid,  as  if  it  belonged  to  a  gas,  and  that  space, 
if  originally  empty,  will  in  consequence  of  the  action  just  described,  become 
more  and  more  filled  with  these  projected  molecules,  which  will  comport 
themselves  within  it  exactly  like  a  gas,  impinging  and  exerting  pressure 
upon  the  sides  of  the  envelope.  One  of  these  sides,  however,  is  formed  by 


HEAT.  81 

the  surface  of  the  liquid,  and  when  a  molecule  impinges  upon  this  surface, 
it  will,  in  general,  not  be  driven  back,  but  retained  by  the  attractive  forces 
of  the  other  molecules.  A  state  of  equilibrium,  not  static,  but  dynamic, 
will  therefore  be  attained,  when  the  number  of  molecules  projected  in  a 
given  time  into  the  space  above,  is  equal  to  the  number  which  in  the  same 
time  impinge  upon  and  are  retained  by  the  surface  of  the  liquid.  This  is 
the  process  of  vaporization.  The  density  of  the  vapor  required  to  insure 
the  compenzation  just  mentioned,  depends  upon  the  rate  at  which  the  par- 
ticles are  projected  from  the  surface  of  the  liquid,  and  this  again  upon  the 
rapidity  of  their  movement  within  the  liquid,  that  is  to  say,  upon  the  tem- 
perature. It  is  clear,  therefore,  that  the  density  of  a  saturated  vapor  must 
increase  with  the  temperature. 

If  the  space  above  the  liquid  is  previously  filled  with  a  gas,  the  molecules 
of  this  gas  will  impinge  upon  the  surface  of  the  liquid,  and  thereby  exert 
pressure  upon  it;  but  as  these  gas-molecules  occupy  but  an  extremely  small 
proportion  of  the  space  above  the  liquid,  the  particles  of  the  liquid  will  be 
projected  into  that  space  almost  as  if  it  were  empty.  In  the  middle  of  the 
liquid,  however,  the  external  pressure  of  the  gas  acts  in  a  different  manner. 
There  also  it  may  happen  that  the  molecules  may  be  separated  with  such 
force  as  to  produce  a  small  vacuum  in  the  midst  of  the  liquid.  But  this 
space  is  surrounded  on  all  sides  by  masses  which  afford  no  passage  to  the 
disturbed  molecules ;  and  in  order  that  they  may  increase  to  a  permanent 
vapor-bubble,  the  number  of  molecules  projected  from  the  inner  surface  of 
the  vessel  must  be  such  as  to  produce  a  pressure  outwards  equal  to  the  ex- 
ternal pressure  tending  to  compress  the  vapor-bubble.  The  boiling  of  the 
liquid  will,  therefore,  be  higher  as  the  external  pressure  is  greater. 

According  to  this  view  of  the  process  of  vaporization,  it  is  possible  that 
vapor  may  rise  from  a  solid  as  well  as  from  a  liquid;  but  it  by  no  means 
necessarily  follows  that  vapor  must  be  formed  from  all  bodies  at  all  tempera- 
tures. The  force  which  holds  together  the  molecules  of  a  body  may  be 
too  great  to  be  overcome  by  any  combination  of  molecular  movements,  so 
long  as  the  temperature  does  not  exceed  a  certain  limit. 

The  production  and  consumption  of  heat  which  accompany  changes  in  the 
state  of  aggregation,  or  of  the  volume  of  bodies,  are  easily  explained,  ac- 
cording to  the  preceding  principles,  by  taking  account  of  the  work  done  by 
the  acting  forces.  This  work  is  partly  external  to  the  body,  partly  internal. 
To  consider  first  the  internal  work  : 

.  When  the  molecules  of  a  body  change  their  relative  positions,  the  change 
may  take  place  either  in  accordance  with  or  in  opposition  to  the  action  of 
the  molecular  forces  existing  within  the  body.  In  the  former  case,  the 
molecules,  during  the  passage  from  one  state  to  the  other,  have  a  certain 
velocity  imparted  to  them,  which  is  immediately  converted  into  heat;  in  the 
latter  case,  the  velocity  of  their  movement,  and  consequently  the  tempera- 
ture of  the  body,  is  diminished.  In  the  passage  from  the  solid  to  the  liquid 
state,  the  molecules,  although  not  removed  from  the  spheres  of  their  mutual 
attractions,  nevertheless  change  their  relative  positions  in  opposition  to  the 
molecular  forces,  which  forces  have,  therefore,  to  be  overcome.  In  evapo- 
ration, a  certain  number  of  the  molecules  are  completely  separated  from  the 
remainder,  which  again  implies  the  overcoming  of  opposing  forces.  In 
both  cases,  therefore,  work  is  done,  and  a  certain  portion  of  the  working 
force  of  the  molecules,  that  is,  of  the  heat  of  the  body,  is  lost.  But  when 
once  the  perfect  gaseous  state  is  attained,  the  molecular  forces  are  com- 
pletely overcome,  and  any  further  expansion  may  take  place  without  inter- 
nal work,  and,  therefore,  without  loss  of  heat,  provided  there  is  no  external 
resistance. 

But  in  nearly  all  cases  of  change  of  state  or  volume,  there  is  a  certain 
amount  of  external  resistance  to  be  overcome,  and  a  corresponding  loss  of 


82  HEAT. 

heat.  When  the  pressure  of  a  gas,  that  is  to  say,  the  impact  of  its  atoms, 
is  exerted  against  a  movable  obstacle,  such  as  a  piston,  the  molecules  lose 
just  so  much  .of  their  moving  power  as  they  have  imparted  to  the  piston, 
and,  consequently,  their  velocity  is  diminished  and  the  temperature  lowered. 
On  the  contrary,  when  a  gas  is  compressed  by  the  motion  of  a  piston,  its 
molecules  are  driven  back  with  greater  velocity  than  that  with  which  they 
impinged  on  the  piston,  and,  consequently,  the  temperature  of  the  gas  is 
raised. 

When  a  liquid  is  converted  into  vapor,  the  molecules  have  to  overcome 
the  atmospheric  pressure  or  other  external  resistance,  and,  in  consequence 
of  this,  together  with  the  internal  work  already  spoken  of,  a  large  quantity 
of  heat  disappears,  or  is  rendered  latent,  the  quantity  thus  consumed  being, 
to  a  considerable  extent,  affected  by  the  external  pressure.  The  liquefac- 
tion of  a  solid  not  being  attended  with  much  increase  of  volume,  involves 
but  little  external  work;  nevertheless  the  atmospheric  pressure  does  in- 
fluence, to  a  slight  amount,  both  the  latent  heat  of  fusion  and  the  melting- 
point. 


LIGHT.  83 


LIGHT. 

nnWO  views  have  been  entertained  respecting  the  nature  of  light.  Sir 
Isaac  Newton  imagined  that  luminous  bodies  emit,  or  shoot  out,  infi- 
nitely small  particles  in  straight  lines,  which,  by  penetrating  the  transparent 
parts  of  the  eye  and  falling  upon  the  nervous  tissue,  produce  vision.  Other 
philosophers  drew  a  parallel  between  the  properties  of  light  and  those  of 
sound,  and  considered  that,  as  sound  is  certainly  the  effect  of  undulations, 
or  little  waves,  propagated  through  elastic  bodies  in  all  directions,  so  light 
might  be  nothing  more  than  the  consequence  of  similar  undulations  trans- 
mitted with  inconceivable  velocity  through  a  highly  elastic  medium,  of  ex- 
cessive tenuity,  filling  all  space,  and  occupying  the  intervals  between  the 
particles  of  material  substances.  To  this  medium  they  gave  the  name  of 
ether.  The  wave  hypothesis  of  light  is  at  present  generally  adopted.  It  is 
in  harmony  with  all  the  known  phenomena  discovered  since  the  time  of 
Newton,  not  a  few  of  which  were  first  deduced  from  the  undulatory  theory, 
and  afterwards  verified  by  experiment.  Several  well-known  facts  are  in 
direct  opposition  to  the  theory  of  emission. 

A  ray  of  light  emitted  from  a  luminous  body  proceeds  in  a  straight  line, 
and  with  extreme  velocity.  Certain  astronomical  observations  afford  the 
means  of  approximating  to  a  knowledge  of  this  velocity.  The  satellites  of 
Jupiter  revolve  about  the  planet  in  the  same  manner  as  the  moon  about  the 
earth,  and  the  time  required  by  each  satellite  for  the  purpose  is  exactly 
known  from  its  periodical  entry  into  or  exit  from  the  shadow  of  the  planet. 
The  time  required  by  one  is  only  42  hours.  Homer,  the  astronomer  of 
Copenhagen,  found  that  this  period  appeared  to  be  longer  when  the  earth, 
in  its  passage  round  the  sun,  moved  from  the  planet  Jupiter ;  and,  on  the 
contrary,  he  observed  that  the  periodic  time  appeared  to  be  shorter  when 
the  earth  moved  in  the  direction  towards  Jupiter.  The  difference,  though 
very  small  for  a  single  revolution  of  the  satellite,  increases,  by  the  addition 
of  'many  revolutions,  during  the  passage  of  the  earth  from  its  nearest  to 
its  greatest  distance  from  Jupiter,  that  is,  in  about  half  a  year,  till  it 
amounts  to  16  minutes  and  16  seconds.  Homer  concluded  from  this,  that 
the  light  of  the  sun,  reflected  from  the  satellite,  required  that  time  to 
pass  through  a  distance  equal  to  the  diameter  of  the  orbit  of  the  earth ; 
and  since  this  place  is  little  short  of  200  millions  of  miles,  the  velocity  of 
light  cannot  be  less  than  200,000  miles  in  a  second  of  time.  It  will  be  seen 
hereafter  that  this  rapidity  of  transmission  is  rivalled  by  that  of  electricity. 
Another  astronomical  phenomenon,  observed  and  correctly  explained  by 
Bradley,  the  aberration  of  the  fixed  stars,  leads  to  the  same  result.  Phy- 
sicists have,  moreover,  succeeded  in  measuring  the  velocity  of  light  for 
terrestrial,  and,  indeed,  comparatively  small  distances;  the  results  of 
these  experiments  essentially  correspond  with  those  given  by  astronomical 
observations. 

When  a  ray  of  light  falls  upon  a  boundary  between  two  media,  a  part  of 
it,  and,  in  exceptional  cases,  the  whole,  is  reflected  into  the  first  medium, 
whilst  the  other  part  penetrates  the  second  medium. 

The  law  of  regular  reflection  is  extremely  simple.  If  a  line  be  drawn 
perpendicular  to  the  surface  upon  which  the  ray  falls,  and  the  angle  con- 
tained between  the  ray  and  the  perpendicular  measured,  it  will  be  found, 


LIGHT. 


Fig.  52. 


Fig.  53. 


that  the  ray,  after  reflection,  takes  such  a  course  as  to  make  with  the  per- 
pendicular an  equal  angle  on  the  opposite  side  of  the  latter.     A  ray  of  light, 

R,  falling  at  the  point  p,  will  be  reflected 
in  the  direction  PR',  making  the  angle 
R'PP'  equal  to  the  angle  RPPX  ;  and  a  ray 
from  the  point  r  falling  upon  the  same  spot 
will  be  reflected  to  rf  in  virtue  of  the  same 
law.  Further,  it  is  to  be  observed  that  the 
incident  and  reflected  rays  are  always  con- 
tained in  the  same  normal  plane. 

The  same  rule  holds  good  if  the  mirror 
be  curved,  as  a  portion  of  a  sphere,  the 
curve  being  considered  as  made  up  of  a 
multitude  of  little  planes.  Parallel  rays 
cease  to  be  so  when  reflected  from  curved  surfaces,  becoming  divergent  or 
convergent  according  as  the  reflecting  surface  is  convex  or  concave. 

Bodies  with  rough  and  uneven  surfaces,  the  smallest  parts  of  which  are 
inclined  towards  each  other  without  order,  reflect  the  light  diffused.  The 
perception  of  bodies  depends  upon  the  diffused  reflected  light. 

It  has  just  been  stated  that  light  passes  in 
straight  lines ;  but  this  is  true  only  so  long  as 
the  medium  through  which  it  travels  pre- 
serves the  same  density  and  the  same  chemi- 
cal nature :  when  this  ceases  to  be  the  case, 
the  ray  of  light  is  bent  from  its  course  into  a 
new  one,  or  is  said  to  be  refracted. 

Let  E  be  a  ray  of  light  falling  upon  a  plate 
of  some  transparent  substance  with  parallel 
sides,  such  as  a  piece  of  thick  plate  glass,  — 
in  short,  any  transparent  homogeneous  ma- 
terial which  is  either  non-crystalline,  or  crys- 
tallizes in  the  regular  system ;  and  let  A  be 
its  point  of  contact  with  the  upper  surface. 
The  ray,  instead  of  holding  a  straight  course 
and  passing  into  the  glass  in  the  direction  A  B,  will  be  bent  downwards  to 
c ;  and,  on  leaving  the  glass,  and  issuing  into  the  air  on  the  other  side,  it 
will  again  be  bent,  but  in  the  opposite  direction,  so  as  to  make  it  parallel 
to  the  continuation  of  its  former  track,  provided  there  be  one  and  the  same 
medium  on  the  upper  and  lower  side  of  the  plate.  The  general  law  is  thus 
expressed: — When  the  ray  passes  from  a  rare  to  a  denser  medium,  it  is 
usually  refracted  towards  a  line  perpendicular  to  the  surface  of  the  latter; 
and  conversely,  when  it  leaves  a  dense  medium  for  a  rarer  one,  it  is  re- 
fracted from  a  line  perpendicular  to  the  surface  of  the  denser  substance ;  in 
the  former  case  the  angle  of  incidence  is  greater  than  that  of  refraction ;  in 
the  latter  it  is  less.  In  both  cases  the  direction  of  the  refracted  ray  is  in 
the  plane  R  A  s,  which  is  formed  by  the  falling  ray  and  the  perpendicular 
s  A  drawn  from  the  spot  where  the  ray  is  refracted ;  the  angle  RAS  =  BAS/, 
is  called  the  angle  of  incidence.  The  angle  c  A  s/  is  called  the  angle  of  re- 
fraction. The  difference  of  these  two  angles,  that  is,  the  angle  CAB,  is  the 
refraction. 

The  amount  of  refraction,  for  the  same  medium,  varies  with  the  obliquity 
with  which  the  ray  strikes  the  surface.  When  perpendicular  to  the  latter, 
the  ray  passes  without  change  of  direction  at  all;  and  in  other  positions, 
the  refraction  increases  with  the  obliquity. 

Let  R  represent  a  ray  of  light  falling  upon  the  surface  of  a  mass  of  plate 
glass  at  the  point  A.  From  this  point  let  a  perpendicular  fall  and  be  con- 
tinued into  the  new  medium ;  and  around  the  same  point,  as  a  centre,  let 


\ 


\ 


LIGHT. 


85 


Fig.  54. 


a  circle  be  drawn.  According  to  the  law  just  stated,  the  refraction  must 
be  towards  the  perpendicular;  in  the  direction  A B/,  for  example.  Let  the 
}ines  a — rtj  af — a',  at  right  angles  to  the  per- 
pendicular, be  drawn,  and  their  length  com- 
pared by  means  of  a  scale  of  equal  parts,  and 
noted;  their  length  will  in  the  case  supposed 
be  in  the  proportion  of  3  to  2.  These  lines 
are  termed  the  sines  of  the  angles  of  incidence 
and  refraction  respectively. 

Now  let  another  ray  be  taken,  such  as  r ; 
it  is  refracted  in  the  same  manner  to  r',  the 
bending  being  greater  from  the  increased 
obliquity  of  the  ray;  but  what  is  very  re- 
markable, if  the  sines  of  the  two  new  angles 
of  incidence  and  refraction  be  again  com- 
pared, they  will  still  be  found  to  bear  to  each 
other  the  proportion  of  3  to  2.  The  fact  is 
expressed  by  saying,  that  so  long  as  the  light  passes  from  one  to  the  other 
of  the  same  two  media,  the  ratio  of  the  sines  of  the  angles  of  incidence  and  re- 
fraction is  constant.  This  ratio  is  called  the  index  of  refraction. 

Different  bodies  possess  different  refractive  powers ;  generally  speaking, 
the  densest  substances  refract  most.  Combustible  bodies  have  been  noticed 
to  possess  greater  refractive  power  than  their  density  would  indicate,  and 
from  this  observation  Sir  I.  Newton  predicted  the  combustible  nature  of  the 
diamond  long  before  anything  was  known  respecting  its  chemical  nature. 

The  method  adopted  for  describing  the  comparative  refractive  power  of 
different  bodies,  is  to  state  the  ratio  borne  by  the  sine  of  the  angle  of  inci- 
dence in  the  first  medium,  and  on  the  boundary  of  the  second,  to  the  sine 
of  the  angle  of  refraction  in  this  second  medium ;  this  is  called  the  index  of 
refraction  of  the  two  substances;  it  is  greater  or  less  than  unity,  according 
as  the  second  medium  is  denser  or  rarer  than  the  first.  In  the  case  of  air 
and  plate  glass  the  index  of  refraction  is  1-5. 

When  the  index  of  refraction  of  any  particular  substance  is  once  known, 
the  effect  of  the  latter  upon  a  ray  of  light  entering  it  in  any  position  can  be 
calculated  by  the  law  of  sines.  The  following  table  exhibits  the  indices  of 
refraction  of  several  substances,  supposing  the  ray  to  pass  into  them  from 
the  air :  — 


Substances. 
Tabasheer* 
Ice 
Water 


Index  of  refraction. 
.     .     1-10 
.     .  1-30 
1-34 


Fluor  spar 1-40 

Plate  glass  ....  1-50 
Rock-crystal  .  .  .  .1-60 
Chrysolite  .  .  .  .  1-69 
Bisulphide  of  carbon  .  1-70 


Substances.  Index  of  refraction. 

Garnet 1-80 

Glass,  with  much  oxide 

of  lead 1-90 

Zircon 2-00 

Phosphorus 2-20 

Diamond 2-50 

Chromate  of  lead  .     .     .  3-00 

Cinnabar 3-20 

Fig.  55. 


When  a  luminous  ray  enters  a  mass  of  substance 
differing  in  refractive  power  from  the  air,  and  whose 
surfaces  are  not  parallel,  it  becomes  permanently 
deflected  from  its  course  and  altered  in  its  direction. 
It  is  upon  this  principle  that  the  properties  of  prisms 
and  lenses  depend.  To  take  an  example.  —  Fig.  55 
represents  a  triangular  prism  of  glass,  upon  the 
side  of  which  the  ray  of  light  R  may  be  supposed  to  fall.  This  ray  will 


8 


*  A  siliceous  deposit  in  the  joints  of  the  bamboo. 


86  LIGHT. 

of  course  be  refracted,  on  entering  the  glass,  towards  a  line  perpendicular 
to  the  first  surface,  and  again,  from  a  line  perpendicular  to  the  second  sur- 
face on  emerging  into  the  air.  The  result  is  the  deflecton  a  c  R,  which  is 
equal  to  the  sum  of  the  two  deflections  which  the  ray  undergoes  in  passing 
through  the  prism. 

A  convex  lens  is  thus  enabled  to  converge  rays  of  light  falling  upon  it,  and 
a  concave  lense  to  separate  them  more  widely ;  each  separate  part  of  the 
surface  of  the  lens  producing  its  own  independent  effect. 

The  light  of  the  sun  and  celestial  bodies  in  general,  as  well  as  that  of  the 
electric  spark  and  of  all  ordinary  flames,  is  of  a  compound  nature.  If  a  ray 
of  light  from  any  of  the  sources  mentioned  be  admitted  into  a  dark  room  by 
a  small  hole  in  a  shutter,  or  otherwise,  and  suffered  to  fall  upon  a  glass 
prism  in  the  manner  shown  in  fig.  56,  it  will  not  only  be  refracted  from  its 
straight  course,  but  will  be  decomposed  into  a  number  of  colored  rays, 
which  may  be  received  upon  a  white  screen  placed  behind  the  prism.  When 
solar  light  is  employed,  the  colors  are  extremely  brilliant,  and  spread  into 

Fig.  56. 


an  oblong  space  of  considerable  length.  The  upper  part  of  this  image,  or 
spectrum,  will  be  violet  and  the  lower  red,  the  intermediate  portion,  com- 
mencing from  the  violet,  being  indigo,  blue,  green,  yellow,  and  orange,  all 
graduating  imperceptibly  into  each  other.  This  is  the  celebrated  experi- 
ment of  Sir  Isaac  Newton ;  from  it  he  drew  the  inference  that  white  light 
is  composed  of  seven  primitive  colors,  the  rays  of  which  are  differently  re- 
frangible by  the  same  medium,  and  hence  capable  of  being  thus  separated. 
The  violet  rays  are  most  refrangible,  and  the  red  rays  least.* 

Bodies  of  the  same  mean  refractive  power  do  not  always  equally  disperse 
or  spread  out  the  differently  colored  rays  to  the  same  extent;  because  the 
principal  yellow  or  red  rays,  for  instance,  are  equally  refracted  by  two 
prisms  of  different  materials,  it  does  not  follow  that  the  blue  or  the  violet 
will  be  similarly  affected.  Hence,  prisms  of  different  varieties  of  glass,  or 
other  transparent  substances,  give,  under  similar  circumstances,  very  dif- 
ferent spectra,  both  as  respects  the  length  of  the  image,  and  the  relative 
extent  of  the  colored  bands. 

The  appearance  of  the  spectrum  may  also  vary  with  the  nature  of  the 
source  of  light:  the  investigation  of  these  differences,  however,  involves 
the  use  of  a  more  delicate  apparatus.  Fig.  57  shows  the  principle  of  such 
an  apparatus,  which  is  called  a  spectroscope.  The  light,  passing  through  a 
fine  slit,  s,  impinges  upon  a  flint-glass  prism,  p,  by  which  it  is  dispersed. 
The  decomposed  light  emerges  from  the  prism  in  several  directions  between 
r  (red  rays)  and  v  (violet  rays) ;  and  the  spectrum  thus  produced  is  observed 

*  The  colors  of  natural  objects  are  supposed  to  result  from  the  power  possessed  by  their 
surfaces  of  absorbing  some  of  the  colored  rays,  while  they  reflect  or  transmit,  as  the  case  may 
be,  the  remainder  of  the  rays.  Thus  an  object  appears  red  because  it  absorbs  or  causes  to 
disappear  the  yellow  and  blue  rays  composing  the  white  light  by  which  it  is  illuminated. 
Any  color  which  remains  after  the  deduction  of  another  color  from  white  light,  is  said  to  be 
cnmpJenifntari/  to  the  latter.  Complementary  colors,  when  acting  simultaneously,  reproduce 
white  light.  Thus  in  the  example  already  quoted,  red  and  green  —  the  latter  resulting  from 
yellow  and  blue  —  are  complementary  colors.  The  fact  of  complementary  colors  giving  rise 
to  white  light  may  be  readily  illustrated  by  mixing  in  appropriate  quantities  a  rose-red  solu.^ 
ticm  of  cobalt  and  green  solution  of  nickel;  the  resulting  liquid  is  nearly  colorless. 


LIGHT. 


87 


by  the  telescope  t,  which  receives  only  part  of  it  at  once ;  but  the  several 
parts  may  be  readily  examined  by  turning  slightly  either  the  prism,  j?,  or 
the  telescope,  t. 

Fig.  57. 


If  the  solar  spectrum  be  examined  in  this  manner,  numerous  dark  lines 
parallel  with  the  edge  of  the  prism  are  observed.  They  were  discovered 
in  1802  by  Dr.  Wollaston,  and  subsequently  more  minutely  investigated  by 
Fraunhofer.  They  are  generally  known  as  Fraunhofer's  lines.  These  dark 
lines,  which  exist  in  great  numbers,  and  of  very  varying  strength,  are  ir- 
regularly distributed  over  the  whole  spectrum.  Some  of  them,  in  con- 
sequence of  their  peculiar  strength  and  their  mutual  position,  may  always 
be  easily  recognized ;  the  more  conspicuous  are  represented  in  fig.  58.  The 
same  dark  lines,  though  paler,  and  much  more  difficult  to  recognize,  are 

Fig.  58. 

Red.  Orange.  Yellow.  Green.    Blue.        Indigo.    Tiolet. 
A      B    C      D         "E"^      F  G  H 


Sun 


Na 


Dark 

lines. 


Sr 


Bright 
lines. 


observed  in  the  spectrum  of  planets  lighted  by  the  sun ;  for  instance,  in 
the  light  emanating  from  Venus.  On  the  other  hand,  the  dark  lines  ob- 
served in  the  spectra,  which  are  produced  by  the  light  emanating  from  fixed 
stars  —  from  Sirius,  for  instance  —  differ  in  position  from  those  previously 
mentioned. 

Sources  of  light  which  contain  no  volatile  constituents  —  incandescent 
platinum  wire,  for  example  —  furnish  continuous  spectra,  exhibiting  no  such 
lines.  But  if  volatile  substances  be  present  in  the  source  of  light,  bright 
lines  are  observed  in  the  spectrum,  which  are  frequently  characteristic  of 
the  volatile  substances. 

Professor  Pliicker,  of  Bonn,  has  investigated  the  spectra  which  are  pro- 
duced by  the  electric  light  when  developed  in  very  rarefied  gases.  He 
found  the  bright  lines  and  the  dark  stripes  between  the  lines  varying  con- 
siderably with  different  gases.  When  the  electric  light  was  developed  in  a 


88 


LIGHT. 


mixture  of  two  gases,  the  spectrum  thus  obtained  exhibited  simultaneously 
the  peculiar  spectra  belonging  to  the  two  gases  of  which  the  mixture  con- 
sisted. When  the  experiment  was  made  in  gaseous  compounds  capable  of 
being  decomposed  by  the  electrical  current,  this  decomposition  was  indicated 
by  the  spectra  of  the  separated  constituents  becoming  perceptible. 

Many  years  ago  the  spectra  of  colored  flames  were  examined  by  Sir  John 
Herschel,  Fox  Talbot,  and  W.  A.  Miller.  Within  the  last  few  years  results 
of  the  greatest  importance  have  been  obtained  by  Kirchhoff  and  Bunsen, 

Fig.  59. 


who  have  investigated  the  spectra  furnished  by  the  incandescence  of  vola- 
tile substances:  these  researches  have  enriched  chemistry  with  a  new 
method  of  analysis, — the  analysis  by  spectrum  observations.  In  order  to 
recognize  one  of  the  metals  of  the  alkalies  or  of  the  alkaline  earths,  it  is 
generally  sufficient  to  introduce  a  minute  quantity  of  a  moderately  volatile 
compound  of  the  metal  on  the  loop  of  a  platinum  wire  into  the  edge  of  the 
very  hot,  but  scarcely  luminous  flame,  of  a  mixture  of  air  and  coal-gas,  and 
to  examine  the  spectrum  which  is  furnished  by  the  flame  containing  the 
vapor  of  the  metal  or  its  compound.  Fig.  59  exhibits  the  apparatus  which 
is  used  in  performing  experiments  of  this  description.  The  light  of  the 
flame  in  which  the  metallic  compound  is  evaporated  passes  through  the  fine 
slit  in  the  disc,  s,  into  a  tube,  the  opposite  end  of  which  is  provided  with  a 
convex  lens.  This  lens  collects  the  rays  diverging  from  the  slit,  and  throws 
them  parallel  upon  the  prism,  p.  The  light  is  decomposed  by  the  prism, 
and  the  spectrum  thus  obtained  is  observed  by  means  of  the  telescope,  which 
may  be  turned  round  the  axis  of  the  stand  carrying  the  prism.  Foreign 
light  is  excluded  by  an  appropriate  covering. 

The  limits  of  this  elementary  treatise  do  not  permit  us  to  describe  the 
ingenious  arrangements  which  have  been  contrived  for  sending  the  light 
from  different  sources  through  the  same  prism  at  different  heights,  whereby 
their  spectra,  the  solar  spectrum,  for  instance,  and  that  of  a  flame,  may  be 
placed  in  a  parallel  position,  the  one  above  the  other,  and  thus  be  compared.* 
The  spectra  of  flames  in  which  different  substances  are  volatilized  frequently 
exhibit  such  characteristically  distinct  phenomena,  that  they  may  be  used 
with  the  greatest  advantage  fcfr  the  discrimination  of  these  substances.  Thus 
the  spectrum  of  a  flame  containing  sodium  (Na)  exhibits  a  bright  line  on 

*  See  the  article  "  Spectral  Analysis,"  by  Prof.  Roscoe,  in  Watts's  Dictionary  of  Chemistry, 
vol.  i. 


LIGHT.  89 

the  yellow  portion,  the  spectrum  of  potassium  .(K)  a  characteristic  bright 
line  at  the  extreme  limit  of  the  red,  and  another  at  the  opposite  violet  limit 
of  the  spectrum.  Lithium  (Li)  shows  a  bright  brilliant  line  in  the  red,  and 
a  paler  line  in  the  yellow  portion ;  strontium  (Sr)  a  bright  line  in  the  blue, 
one  in  the  orange,  and  six  less  distinct  ones  in  the  red  portion  of  the  spec- 
trum. The  diagram  (fig.  58)  exhibits  the  most  remarkable  of  the  dark 
lines  (Fraunhofers  lines),  and  the  position  of  the  bright  lines  in  the 
spectra  of  flames  containing  the  vapors  of  compounds  of  the  several  metals 
enumerated. 

The  delicacy  of  these  spectral  reactions  is  very  considerable,  but  unequal 
in  the  case  of  different  metals.  The  presence  of  YTre.imT.Tnnj'  Srain  °f  sodium 
in  the  flame  is  still  easily  recognizable  by  the  bright  yellow  line  in  the 
spectrum.  Lithium,  when  introduced  in  the  form  of  a  volatile  compound, 
imparts  to  the  flame  a  red  color;  but  this  coloration  is  no  longer  perceptible 
when  a  volatile  sodium  compound  is  simultaneously  present,  the  yellow 
coloration  of  the  flame  predominating  under  such  circumstances.  On  the 
other  hand,  when  a  mixture  of  one  part  of  lithium  and  1000  parts  of 
sodium  is  volatilized  in  a  flame,  the  spectrum  of  the  flame  exhibits,  together 
with  the  bright  yellow  sodium  line,  likewise  the  red  line  characteristic  of 
lithium.  The  observation  of  bright  lines  not  belonging  to  any  of  the  pre- 
viously known  bodies  has  led  to  the  discovery  of  new  elements.  Thus, 
Bunsen  and  Kirchhoff,  when  examining  the  spectrum  of  a  flame  in  which  a 
mixture  of  alkaline  salt  was  evaporated,  observed  some  bright  lines,  which 
could  not  be  attributed  to  any  of  the  known  elements,  and  were  thus  led  to 
the  discovery  of  the  two  new  metals,  caesium  and  rubidium.  By  the  same 
method  a  new  element,  thallium,  has  been  more  recently  discovered  by  Mr. 
Crookes. 

For  the  examination  of  the  bright  lines  in  the  spectra  of  metals,  the 
electric  spark,  passing  between  two  points  of  the  metal  under  examination, 
may  be  conveniently  employed  as  a  source  of  light.  Small  quantities  of 
the  metal  are  invariably  volatilized ;  and  the  spectrum  developed  by  the 
electric  light  exhibits  the  bright  lines  characteristic  of  the  metal  employed. 
These  lines  were  observed  by  Wheatstone  as  early  as  1835.  This  method  of 
investigation  is  more  especially  applicable  to  the  examination  of  the  spectra 
of  the  heavy  metals. 

By  a  series  of  theoretical  considerations,  Professor  Kirchhoff  has  arrived 
at  the  conclusion  that  the  spectrum  of  an  incandescent  gas  is  reversed  —  i.  e., 
that  the  bright  lines  become  dark  lines,  if  there  be  behind  the  incandescent 
gas  a  very  luminous  source  of  light,  which  by  itself  furnishes  a  continuous 
spectrum.  Kirchhoff  and  Bunsen  have  fully  confirmed  this  conclusion  by 
experiment.  Thus  a  volatile  lithium  salt  produces,  as  just  pointed  out,  a 
very  distinct  bright  line  in  the  red  portion  of  the  spectrum ;  but  if  bright 
sunlight,  or  the  light  emitted  by  a  solid  body  heated  to  the  most  powerful 
incandescence,  be  allowed  to  fall  through  the  flame  upon  the  prism,  the 
spectrum  exhibits,  in  the  place  of  this  bright  line,  a  black  line  similar  in 
every  respect  to  Fraunhofers  lines  in  the  solar  spectrum.  In  like  manner 
the  bright  strontium  line  is  reversed  into  a  dark  line.  Kirchhoff  and  Bunsen 
have  expressed  the  opinion  that  all  the  Fraunhofer  lines  in  the  solar  spec- 
trum are  bright  lines  thus  reversed.  In  their  conception,  the  sun  is  sur- 
rounded by  aluminous  atmosphere,  containing  a  certain  number  of  volatilized 
substances,  which  would  give  rise  in  the  spectrum  to  certain  bright  lines, 
if  the  light  of  the  solar  atmosphere  alone  could  reach  the  prism ;  but  the 
intense  light  of  the  powerful  incandescent  body  of  the  sun  which  passes 
through  the  solar  atmosphere,  causes  these  bright  lines  to  be  reversed,  and 
to  appear  as  dark  lines  on  the  ordinary  solar  spectrum.  Kirchhoff  and 
Bunsen  have  thus  been  enabled  to  attempt  the  investigation  of  the  chemical 
constituents  of  the  solar  atmosphere,  by  ascertaining  the  elements  which, 

8* 


90  LIGHT. 

when  in  the  state  of  incandescent  vapor,  develop  bright  spectral  lines,  co- 
inciding with  Fraunhofer's  lines  in  the  solar  spectrum.  Fraunhofer's  line 
D  (fig.  58)  coincides  most  accurately  with  the  bright  spectral  line  of  sodium, 
and  may  be  artificially  produced  by  reversing  the  latter;  sodium  would  thus 
appear  to  be  a  constituent  of  the  solar  atmosphere.  Kirchhoff  has  proved, 
moreover,  that  sixty  bright  lines  perceptible  in  the  spectrum  of  iron  cor- 
respond, both  as  to  position  and  distinction,  most  exactly  with  the  same 
number  of  dark  lines  in  the  solar  spectrum;  and,  accordingly,  he  believes 
iron,  in  the  state  of  vapor,  to  be  present  in  the  solar  atmosphere.  In  a 
similar  manner  this  physicist  has  endeavored  to  establish  the  presence  of 
several  other  elements  in  the  solar  atmosphere. 

Absorption  Spectra.  —  The  relative  quantities  of  the  several  colored  rays 
absorbed  by  a  colored  medium  of  given  thickness  may  be  observed  by  view- 
ing a  line  of  light  through  a  prism  and  the  colored  medium ;  the  spectrum 
will  then  be  seen  to  be  diminished  in  brightness  in  some  parts,  and  perhaps 
cut  oif  altogether  in  others.  This  mode  of  observation  is  often  of  great  use 
in  chemical  analysis,  as  many  colored  substances  when  thus  examined  afford 
very  characteristic  spectra,  the  peculiarities  of  which  may  often  be  dis- 
tinguished, even  though  the  solution  of  the  substance  under  examination 
contains  a  sufficient  amount  of  colored  impurities  to  change  its  color  very 
considerably.  The  following  method  of  making  the  observation  is  given  by 
Professor  Stokes.* 

A  small  prism  is  to  be  chosen  of  dense  flint  glass,  ground  to  an  angle  of 
60°,  and  just  large  enough  to  cover  the  eye  comfortably.  The  top  and 
bottom  should  be  flat,  for  convenience  of  holding  the  prism  between  the 
thumb  and  fore-finger,  and  laying  it  down  on  a  table,  so  as  not  to  scratch 
or  soil  the  faces.  A  fine  line  of  light  is  obtained  by  making  a  vertical  slit 
in  a  board  six  inches  square,  or  a  little  longer  in  a  horizontal  direction,  and 
adapting  to  the  aperture  two  pieces  of  thin  metal.  One  of  the  metal  pieces 
is  movable,  to  allow  of  altering  the  breadth  of  the  slit.  About  the  fiftieth 
of  an  inch  is  a  suitable  breadth  for  ordinary  purposes.  The  board  and 
metal  pieces  should  be  well  blackened. 

On  holding  the  board  at  arm's  length  against  the  sky  or  a  luminous  flame, 
the  slit  being,  we  will  suppose,  in  a  vertical  direction,  and  viewing  the  line 
of  light  thus  formed  through  the  prism  held  close  to  the  eye,  with  its  edge 
vertical,  a  pure  spectrum  is  obtained  at  a  proper  azimuth  of  the  prism. 
Turning  the  prism  round  its  axis  alters  the  focus,  and  the  proper  focus  is 
got  by  trial.  The  whole  of  the  spectrum  is  not,  indeed,  in  perfect  focus  at 
once,  so  that  in  scrutinizing  one  part  after  another  it  is  requisite  to  turn 
the  prism  a  little.  When  daylight  is  used,  the  spectrum  is  known  to  be 
pure  by  its  showing  the  principal  fixed  lines ;  in  other  cases  the  focus  is  got 
by  the  condition  of  seeing  distinctly  the  other  objects,  whatever  they  may 
be,  which  are  presented  in  the  spectrum.  To  observe  the  absorption-spec- 
trum of  a  liquid,  an  elastic  band  is  put  round  the  board  near  the  top,  and  a 
test-tube  containing  the  liquid  is  slipped  under  the  band,  which  holds  it  in 
its  place  behind  the  slit.  The  spectrum  is  then  observed  just  as  before,  the 
test-tube  being  turned  from  the  eye. 

To  observe  the  whole  progress  of  the  absorption,  different  degrees  of 
strength  must  be  used  in  succession,  beginning  with  a  strength  which 
does  not  render  any  part  of  the  spectrum  absolutely  black,  unless  it  be  one 
or  more  very  narrow  bands,  as  otherwise  the  most  distinctive  features  of 
the  absorption  might  be  missed.  If  the  solution  be  contained  in  a  wedge- 
shaped  vessel  instead  of  a  test-tube,  the  progress  of  the  absorption  may  be 
watched  in  a  continuous  manner  by  sliding  the  vessel  before  the  eye.  Some 
observers  prefer  using  a  wedge-shaped  vessel  in  combination  with  the  slit, 

*  Chem.  Soc.  Journ.  xvii.  306. 


LIGHT. 


91 


the  slit  being  perpendicular  to  the  edge  of  the  wedge.  In  this  case  each 
element  of  the  slit  forms  an  elementary  spectrum  corresponding  to  a  thick- 
ness of  the  solution  which  increases  in  a  continuous  manner  from  ihe  edg« 
of  the  wedge,  where  it  vanishes.  This  is  the  mode  of  observation  adopted 
by  Gladstone.* 

Fig.  00  represents  the  effect  produced  in  this  way  by  a  solution  of 
chromic  chloride,  and  fig.  61  that  produced  by  a  solution  of  potassium 
permanganate. 


Fig.  60. 


Fig.  SI. 


C  d    F    3E  D 


OB 


The  right-hand  side  of  these  figures  corresponds  with  the  red  end  of  the 
spectrum ;  the  letters  refer  to  Fraunhofer's  lines.  The  lower  part  of  each 
figure  shows  the  pure  spectrum  seen  through  the  thinnest  part  of  the  wedge ; 
and  the  progress  of  the  absorption,  as  the  thickness  of  the  liquid  increases, 
is  seen  by  the  gradual  obliteration  of  the  spectrum  towards  the  upper  part 
of  the  figures. 

Fluorescence. — An  examination  into  a  peculiar  mode  of  analysis  of  light, 
discovered  by  Sir  John  Herschel,  in  a  solution  of  quinine  sulphate,  has 
within  the  last  few  years  led  to  the  discovery  of  a  most  remarkable  fact. 
Mr.  Stokes  has  observed  that  light  of  certain  refrangibility  and  color  is 
capable  of  experiencing  a  peculiar  influence  in  being  dispersed  by  certain 
media,  and  of  undergoing  thereby  an  alteration  of  its  refrangibility  and  color. 
This  curious  change,  called  fluorescence,  can  be  produced  by  a  great  number 
of  bodies,  both  liquid  and  solid,  transparent  and  opaque.  Frequently  the 
change  affects  only  the  extreme  limits;  at  other  times  larger  portions,  and 
in  a  few  cases  even  the  whole,  or,  at  all  events,  the  major  part  of  the  spec- 
trum. A  dilute  solution  of  quinine  sulphate,  for  instance,  changes  the 
violet  and  the  dark-blue  light  to  sky-blue ;  by  a  decoction  of  madder  in  a 
solution  of  alum  all  rays  of  higher  refrangibility  than  yellow  are  converted 
into  yellow;  by  an  alcoholic  solution  of  the  coloring  matter  of  leaves  all  the 
rays  of  the  spectrum  become  red.  In  all  cases  in  which  this  peculiar  phe- 
nomenon presented  itself  in  a  greater  or  less  degree,  Mr.  Stokes  observed 
that  it  consisted  in  a  diminution  of  the  refrangibility.  Thus,  rays  of  so 
high  a  degree  of  refrangibility,  that  they  extend  far  beyond  the  extreme 
limits  of  the  spectrum  visible  under  ordinary  circumstances,  may  be  ren- 
dered luminous,  and  converted  into  blue  and  even  red  light. 

DOUBLE  REFRACTION  AND  POLARIZATION.  —  A  ray  of  common  light  made 
to  pass  through  certain  crystals  of  a  particular  order  is  found  to  undergo  a 
.very  remarkable  change.  It  becomes  split  or  divided  into  two  rays,  one  of 


*  Chem.  Soc.  Journ.  x.  79. 


92 


LIGHT. 


Fig.  62. 


which  follows  the  general  law  of  refraction,  while  the  other  takes  a  new 
and  extraordinary  course,  dependent  on  the  position  of  the  crystal.  This 
effect,  which  is  called  double  refraction,  is  beautifully  illustrated  in  the  case 
of  Iceland  spar,  or  crystallized  calcium  carbonate.  On  placing  a  rhomb  of 
this  substance  on  a  piece  of  white  paper  on  which  a  mark  or  line  has  been 
made,  the  object  will  be  seen  double. 

Again,  if  a  ray  of  light  be  suffered  to  fall  on  a  plate  of  glass  at  an  angle 
of  56°  45',  the  portion  of  the  ray  which  suffers  reflection  will  be  found  to 
have  acquired  properties  which  it  did  not  before  possess ;  for  on  throwing 
it,  at  the  same  angle,  upon  a  second  glass  plate,  it  will  be  observed  that 
there  are  two  particular  positions  of  the  latter,  namely,  those  in  which  the 
planes  of  incidents  are  at  right  angles  to  one  another,  when  the  ray  of  light 
is  no  longer  reflected,  but  entirely  refracted.  Light  which  has  suffered  this 
change  is  said  to  be  polarized. 

The  light  which  passes  through  the  first  or  polarizing  plate  is,  also,  to  a 
certain  extent,  in  this  peculiar  condition,  and  by  employing  a  series  of 
similar  plates  held  parallel  to  the  first,  this  effect  may 
be  greatly  increased ;  a  bundle  of  fifteen  or  twenty 
such  plates  may  be  used  with  great  convenience  for  the 
experiment.  It  is  to  be  remarked,  also,  that  the  light 
polarized  by  transmission  in  this  manner  is  in  an  oppo- 
site state  to  that  polarized  by  reflection;  that  is,  when 
examined  by  a  second  or  analyzing  plate,  held  at  the 
angle  before  mentioned,  it  will  be  seen  to  be  reflected 
when  the  other  is  transmitted,  and  to  be  dispersed  when 
the  first  is  reflected. 

It  is  not  every  substance  which  is  capable  of  polar- 
izing light  in  this  manner;  glass,  water,  and  certain 
other  bodies  bring  about  the  change  in  question,  each 
having  a  particular  polarizing  angle  at  which  the  effect 
is  greatest.  The  metals  also  can,  by  reflection,  polarize 
the  light,  but  they  do  so  very  imperfectly.  The  two  rays  into  which  a 
pencil  of  common  light  divides  itself  in  passing  through  a  doubly  refracting 
crystal  are  found  on  examination  to  be  polarized  in  a  very  complete  manner, 
and  also  transversely,  the  one  being  capable  of  reflection  when  the  other 
vanishes  or  is  transmitted.  The  two  rays  are  said  to  be  polarized  in  op- 
posite directions.  With  a  rhomb  of  transparent  Iceland  spar  of  tolerably 
large  dimensions,  the  two  oppositely  polarized  rays  may  be  widely  separated 
and  examined  apart. 

Certain  doubly  refracting  crystals  absorb  the  one  of  these  rays,  but  not 
the  other.  Through  a  plate  of  such  a  crystal  one  ray  passes  and  becomes 
entirely  polarized ;  the  other,  which  is  likewise  polarized,  but  in  another 
plane,  is  removed  by  absorption.  The  best  known  of  these  media  is  tour- 
maline. When  two  plates  of  this  mineral,  cut  parallel  to  the  axis  of  the 
crystal,  are  held  with  their  axes  parallel,  as  in  fig.  63,  light  traverses  them 
both  freely;  but  when  one  of  them  is  turned  round  in  the  manner  shown  in 
fig.  64,  so  as  to  make  the  axes  cross  at  right  angles,  the  light  is  almost 


Fig.  03. 


Fig.  64. 


LIGHT.  93 

wholly  stopped,  if  the  tourmalines  are  good.  A  plate  of  the  mineral  thus 
becomes  an  excellent  test  for  discriminating  between  polarized  light  and 
that  which  has  not  undergone  the  change. 

Some  of  the  most  splendid  phenomena  of  the  science  of  light  are  ex- 
hibited when  thin  plates  of  doubly  refracting  substances  are  interposed 
between  the  polarizing  arrangement  and  the  analyzer. 

Instead  of  the  tourmaline  plate,  which  is  always  colored,  frequent  use  is 
made  of  two  Nichol's  prisms,  or  conjoined  prisms  of  calcium  carbonate, 
which,  in  consequence  of  a  peculiar  cutting  and  combination,  possess  the 
property  of  allowing  only  one  of  the  oppositely  polarized  rays  to  pass.  A 
more  advantageous  method  of  cutting  and  combining  prisms  has  been  given 
by  M.  Foucault.  His  prisms  are  as  serviceable  as  and  less  expensive  than 
those  of  Nichol.  If  two  Nichol's  or  Foucault's  prisms  be  placed  one  behind 
the  other  in  precisely  similar  positions,  the  light  polarized  by  the  one  goes 
through  the  other  unaltered.  But  when  one  prism  is  slightly  turned  round 
in  its  setting,  a  cloudiness  is  produced ;  and  by  continuing  to  turn  the  prism, 
this  increases  until  perfect  darkness  ensues.  This  happens,  as  with  the  tour- 
maline plates,  when  the  two  prisms  cross  one  another.  The  phenomenon 
is  the  same  with  colorless  as  with  colored  light. 

CIRCULAR  POLARIZATION. — Supposing  that  polarized  light,  colored,  for  ex- 
ample, by  going  through  a  plate  of  red  glass,  has  passed  through  the  first 
Nichol's  prism,  and  been  altogether  obstructed  in  consequence  of  the  posi- 
tion of  the  second  prism,  then,  if  between  the  two  prisms  a  plate  of  rock- 
crystal  formed  by  a  section  at  right  angles  to  the  principal  axis  of  the  crystal, 
be  interposed,  the  light  polarized  by  the  first  prism  will,  by  passing  through 
the  plate  of  quartz,  be  enabled  partially  to  pass  through  the  second  Nichol's 
prism.  Its  passage  through  the  second  prism  can  then  again  be  interrupted 
by  turning  the  second  prism  round  to  a  certain  extent.  The  rotation  re- 
quired varieg  with  the  thickness  of  the  plate  of  rock-crystal,  and  also  with 
the  color  of  the  light  employed.  It  increases  from  red  in  the  following 
order  —  yellow,  green,  blue,  violet. 

This  property  of  rock-crystal  was  discovered  by  Arago.  The  kind  of 
polarization  has  been  called  circular  polarization.  The  direction  of  the 
rotation  is  with  many  plates  towards  the  right  hand ;  in  other  plates  it  is 
towards  the  left.  The  one  class  is  said  to  possess  right-handed  polarization, 
the  other  class  left-handed  polarization.  For  a  long  time  quartz  was  the 
only  solid  body  known  to  exhibit  circular  polarization.  Others  have  since 
been  found  which  possess  this  property  in  a  far  higher  degree.  Thus,  a 
plate  of  cinnabar  acts  fifteen  times  more  powerfully  than  a  plate  of  quartz 
of  equal  thickness. 

Biot  observed  that  many  solutions  of  organic  substances  exhibit  the 
property  of  circular  polarization,  though  to  a  far  less  extent  than  rock- 
crystal.  Thus,  solutions  of  cane-sugar,  glucose,  and  tartaric  acid,  possess 
right-handed  polarization;  whilst  albumen,  uncrystallizable  sugar,  and  oil 
of  turpentine,  are  left-handed.  In  all  these  solutions  the  amount  of  circular 
polarization  increases  with  the  concentration  of  the  liquid  and  the  thickness 
of  the  column  through  which  the  light  passes.  Hence  circular  polarization 
is  an  important  auxiliary  in  chemical  analysis.  In  order  to  determine  the 
amount  of  polarization  which  any  liquid  exhibits,  it  is  put  into  a  glass  tube 
not  less  than  from  ten  to  twelve  inches  long,  which  is  closed  with  glass 
plates.  This  is  then  placed  between  the  two  Nichol's  prisms,  which  have 
previously  been  so  arranged  with  regard  to  each  other  that  no  light  could 
pass  through.  An  apparatus  of  this  description,  the  saccharimeter,  is  used 
for  determining  the  concentration  of  solutions  of  cane-sugar. 

The  form  of  this  instrument  may  be  seen  in  fig.  (35.  The  two  Nichol's 
prisms  are  enclosed  in  the  corresponding  fastenings  a  and  6.  Between  the 
two  there  is  a  space  to  receive  the  tube,  which  is  filled  with  the  solution  of 


94 


LIGHT. 


sugar.  If  the  prisms  are  crossed  in  the  way  above  mentioned  before  the 
tube  is  put  in  its  place,  that  is,  if  they  are  placed  so  that  no  light  passes 
them,  then  by  the  action  of  the  solution  of  sugar  the  light  is  enabled  to 
pass,  and  the  Nichol's  prism,  a,  must  be  turned  through  a  certain  angle 
before  the  light  is  again  perfectly  stopped.  The  magnitude  of  this  angle  is 
observed  on  the  circular  disk  s  s,  which  is  divided  into  degrees,  and  upon 
which,  by  the  turning  of  the  prism,  an  index  z  is  moved  along  the  division. 
When  the  tube  is  exactly  ten  inches  long,  and  is  closed  at  both  ends  by  flat 
glass  plates,  and  when  it  is  filled  with  solution  containing  10  per  cent,  by 
weight  of  cane-sugar,  and  free  from  any  other  substance  possessing  an  ac- 
tion on  light,  the  angle  of  rotation  is  13-35°.  Since  the  magnitude  of  this 
angle  stands  in  direct  relation  to  the  length  of  the  column  of  liquid  and 
also  to  the  quantity  of  sugar  in  solution,  it  is  clear  that  the  quantity  of 
sugar  in  any  given  solution,  when  the  length  of  the  column  of  liquid  is  I 
inches,  and  the  angle  of  rotation  is  a  degrees,  can  be  determined  by  the 

a    X    I 
equation  '  =  33^-. 

This  process  is  not  sufficient  when  the  solution  contains  cane-sugar  and 
uncrystallizable  sugar :  for  the  latter  rotates  the  ray  to  the  left ;  in  that 

Fig.  65. 

c 


dud* 


case  only  the  difference  of  the  two  actions  is  obtained.  But  if  the  whole 
quantity  of  sugar  be  changed  into  uncrystallizable  sugar,  and  the  experi- 
ment be  repeated,  then  from  the  results  of  the  two  observations  the  quan- 
tity of  both  kinds  of  sugar  can  easily  be  calculated. 

It  is  difficult  to  find  exactly  that  position  of  the  Nichol's  prisms  in  which 


LIGHT.  95 

the  greatest  darkness  prevails.  To  make  the  measurements  more  exact  and 
easy,  Soleil  has  made  some  additions  to  the  apparatus.  At  <?,  before  the 
prism  6,  a  plate  of  rock-crystal  cut  at  right  angles  to  the  axis  is  placed. 
It  is  divided  in  the  centre  of  the  field  of  vision,  half  consisting  of  quartz 
rotating  to  the  right  hand,  and  half  of  the  variety  which  rotates  to  the  left ; 
it  is  0-148  inch  (3'75  millimetre)  thick,  this  thickness  being  found  by  ex- 
periment to  produce  the  greatest  difference  in  the  color  of  the  two  halves, 
when  one  prism  is  slightly  rotated.  The  solution  of  sugar  has  precisely  the 
same  action  on  the  rotation,  since  it  increases  the  action  of  the  half  which 
has  a  right-handed  rotation,  and  lessens  the  action  of  the  half  which  rotates 
to  the  left.  Hence  the  two  halves  will  assume  a  different  color  when  the 
smallest  quantity  of  sugar  is  present  in  the  liquick  By  slightly  turning  the 
Nichol's  prism  a,  this  difference  can  be  again  removed.  Soleil  has  intro- 
duced another  more  delicate  means  of  effecting  this  at  the  part p,  which  he 
calls  the  compensator.  The  most  important  parts  of  this  are  separately 
represented  in  fig.  65.  It  consists  of  two  exactly  equal  right-angled  prisms, 
of  left-handed  quartz,  whose  surfaces,  cf  and  e,  are  cut  perpendicular  to  the 
optic  axis.  These  prisms  can,  by  means  of  the  screw  v  and  a  rack  and 
pinion,  be  made  to  slide  on  one  another,  so  that,  when  taken  together,  they 
form  a  plate  of  varying  thickness,  bounded  by  parallel  surfaces.  One  of 
the  frames  has  a  scale  p,  the  other  a  vernier  n.  When  this  points  to  zero 
of  the  scale,  the  optical  action  of  the  two  prisms  is  exactly  compensated  by 
a  right-handed  plate  of  rock-crystal,  so  that  an  effect  is  obtained  as  regards 
circular  polarization,  as  if  the  whole  system  wrere  not  present.  As  soon, 
however,  as  the  screw  is  moved,  and  thus  the  thickness  of  the  plate  formed 
by  the  two  prisms  is  changed  (we  will  suppose  it  increased),  then  a  left- 
handed  action  ensues,  which  must  be  properly  regulated,  until  it  compen- 
sates the  opposite  action  of  a  solution  of  sugar.  Thus  a  convenient  method 
is  obtained  of  rendering  the  color  of  the  double  plate  uniform,  when  it  has 
ceased  to  be  so  by  the  action  of  the  sugar. 

Faraday  has  made  the  remarkable  discovery  that,  if  a  very  strong  electric 
current  be  passed  round  a  substance  which  possesses  the  property  of  circular 
polarization,  the  amount  of  rotation  is  altered  to  a  considerable  degree. 

HEATING  AND  CHEMICAL  KAYS  OF  THE  SOLAR  SPECTRUM. — The  luminous 
rays  of  the  sun  are  accompanied,  as  already  mentioned,  by  others  which 
possess  heating  powers.  If  the  temperature  of  the  different-colored  spaces 
in  the  spectrum  be  tried  with  a  delicate  thermometer,  it  will  be  found  to  in- 
crease from  the  violet  to  the  red  extremity,  and  when  the  prism  is  of  some 
particular  kinds  of  glass,  the  greatest  effect  will  be  manifested  a  little  beyond 
the  visible  red  rays.  The  position  of  the  greatest  heating  effect  in  the 
spectrum  materially  depends  on  the  absorptive  nature  of  the  glass.  Trans- 
parent though  this  medium  is  to  the  rays  of  light,  it  nevertheless  absorbs  a 
considerable  quantity  of  the  heat  rays.  Transparent  rock-salt  is  almost 
without  absorptive  action  on  the  thermal  rays.  In  the  spectrum  obtained 
by  passing  the  solar  rays  through  prisms  of  rock-salt,  the  greatest  thermal 
effect  is  found  at  a  position  far  beyond  the  last  visible  red  rays.  It  is  in- 
ferred from  this  that  the  chief  mass  of  the  heating  rays  of  the  sun  are 
among  the  least  refrangible  components  of  the  solar  beam. 

Again,  it  has  long  been  known  that  chemical  changes  both  of  combination 
and  of  decomposition,  but  more  particularly  the  latter,  can  be  effected  by 
the  action  of  light.  Chlorine  and  hydrogen  combine  at  common  tempera- 
tures only  under  the  influence  of  light ;  and  parallel  cases  occur  in  great 
n  umbers  in  organic  chemistry.  The  blackening  and  decomposition  of  silver 
salts  are  familiar  instances  of  the  chemical  powers  of  the  same  agent.  Now, 
it  is  not  always  the  luminous  part  of  the  ray  which  effects  these  changes; 


96  LIGHT. 

they  are  chiefly  produced  by  certain  invisible  rays,  which  accompany  the 
others,  and  are  found  most  abundantly  beyond  the  violet  part  of  the  spec- 
trum. It  is  there  that  certain  chemical  effects  are  most  marked,  although 
the  intensity  of  the  light  is  exceedingly  feeble.  From  the  fact  that  some 
salts  of  silver  are  less  readily  decomposed  by  the  luminous  —  yellow, 
orange,  and  red  rays  —  than  by  certain  rays  which  extend  beyond  the  or- 
dinary visible  spectrum,  it  has  been  concluded  that  there  exists  in  the  sun- 
beam, in  addition  to  heat  and  light,  a  principle  having  a  distinct  action,  to 
which  the  provisional  term  actinism  has  been  given  —  from  d*rtj,  a  ray.  The 
actinic  rays  are  thus  directly  opposed  to  the  heating  rays  in  the  common 
spectrum  in  their  degree  of  refrangibility,  since  they  exceed  all  the  others 
in  this  respect.  The  luminous  rays,  too,  under  peculiar  conditions,  exert 
decomposing  powers  upon  silver  salts.  The  result  of  the  action  of  any  ray 
depends,  moreover,  greatly  on  the  physical  state  of  the  surface  upon  which 
it  falls,  and  on  the  chemical  constitution  of  the  body ;  indeed,  for  every 
kind  of  ray  a  substance  may  be  found  which  under  particular  circumstances 
will  be  affected  by  it ;  and  thus  it  appears  that  the  chemical  functions  are 
by  no  means  confined  to  any  set  of  rays  to  the  exclusion  of  the  rest. 

Upon  the  chemical  changes  produced  by  light  is  based  the  art  of  photo- 
graphy. In  the  year  1802,  Mr.  Thomas  Wedgwood  proposed  a  method  of 
copying  paintings  on  glass  by  placing  behind  them  white  paper  or  leather 
moistened  with  a  solution  of  silver  nitrate,  which  became  decomposed  and 
blackened  by  the  transmitted  light  in  proportion  to  the  intensity  of  the 
latter;  and  Davy,  in  repeating  these  experiments,  found  that  he  could  thus 
obtain  tolerably  accurate  representations  of  objects  of  a  texture  partly 
opaque  and  partly  transparent,  such  as  leaves  and  the  wings  of  insects, 
and  even  copy  with  a  certain  degree  of  success  the  images  of  small  objects 
obtained  by  the  solar  microscope.  These  pictures,  however,  required  to 
be  kept  in  the  dark,  and  could  only  be  examined  by  candle-light,  otherwise 
they  became  obliterated  by  the  blackening  of  the  whole  surface  from  which 
the  salt  of  silver  could  not  be  removed  These  attempts  at  light-painting 
attracted  but  little  notice  till  the  publication  of  Mr.  Fox  Talbot's  papers, 
read  before  the  Royal  Society,  in  January  and  February,  1839,  in  which 
he  detailed  two  methods  of  fixing  the  pictures  produced  by  the  action  of 
light  on  paper  impregnated  with  silver  chloride,  and  at  the  same  time  de- 
scribed a  plan  by  which  the  sensibility  of  the  prepared  paper  may  be  in- 
creased to  the  extent  required  for  receiving  impressions  from  the  images 
of  the  camera  obscura. 

Very  shortly  afterwards,  Sir  John  Herschel  proposed  to  employ  solutions 
of  the  alkaline  hyposulphites  for  removing  the  excess  of  silver  chloride 
from  the  paper,  and  thus  preventing  the  further  action  of  light;  and  this 
plan  has  been  found  exceedingly  successful.  The  greatest  improvement, 
however,  which  the  curious  art  of  photogenic  drawing  has  received,  is  due 
to  Mr.  Talbot,  who,  in  a  communication  to  the  Royal  Society,  described 
a  method  by  which  paper  of  such  sensibility  could  be  prepared  as  to  per- 
mit its  application  to  the  taking  of  portraits  of  living  persons  by  the  aid 
of  a  good  camera  obscura,  the  time  required  for  a  perfect  impression 
seldom  exceeding  a  few  seconds.  The  plan  at  present  in  use  is  the 
following: 

Writing-paper  of  good  quality  is  washed  on  one  side  with  a  solution  of 
thirty  grains  of  silver  nitrate  in  one  ounce  of  distilled  water,  and  then  left 
to  dry  spontaneously  in  a  dark  room ;  when  dry,  it  is  immersed  for  from 
five  to  ten  minutes  in  a  solution  of  one  ounce  of  potassium  iodide  in  twenty 
ounces  of  water.  The  paper  is  then  soaked  in  water  for  half  an  hour, 
changing  the  water  three  or  four  times  to  remove  the  excess  of  potassium 
iodide,  and  is  then  dried.  These  operations  should  be  performed  by  candle- 
light. When  required  for  use,  the  paper,  thus  coated  with  yellow  silver 


LIGHT.  97 

iodide,  is  brushed  over  with  a  solution  made  by  adding  together  one  part 
of  a  solution  of  silver  nitrate,  fifty  grains  to  one  ounce  of  water;  two 
parts  glacial  acetic  acid,  and  three  purts  of  a  saturated  solution  of  gallic 
acid;  after  a  few  seconds  the  excess  is  removed  by  blotting-paper.  This, 
which  is  called  Talbotype  or  Calotype  paper,  is  now  ready  for  use;  exposure 
to  diffused  daylight  for  one  second  suffices  to  make  an  impression  upon  it, 
and  even  the  light  of  the  moon  produces  the  same  effect,  although  a  much 
longer  time  is  required.  For  landscapes  and  fixed  objects,  and  when  the 
paper  is  required  to  be  prepared  long  beforehand,  the  above  mixture  of 
"gallo-nitrate"  should  be  diluted  with  from  twenty  to  fifty  volumes  of 
water,  since,  especially  in  hot  weather,  without  this  precaution  the  paper 
blackens  spontaneously. 

The  images  of  the  camera  obscura  are  at  first  invisible,  but  are  made  to 
appear  in  full  intensity,  by  once  more  washing  the  paper  with  a  mixture 
of  one  part  of  the  silver  solution  (fifty  grains  to  an  ounce  of  water)  and 
four  parts  of  the  saturated  solution  of  gallic  acid.  The  image  soon  appears, 
and  should  be  fully  developed  in  a  few  minutes. 

The  picture  is  of  course  negative,  the  lights  and  shadows  being  reversed; 
to  obtain  positive  copies,  nothing  more  is  necessary  than  to  place  a  piece  of 
photographic  pap'er  prepared  with  silver  chloride,  or  a  piece  of  talbotype 
paper,  beneath  the  negative  cover,  to  press  the  two  papers  in  contact  by 
means  of  a  glass,  and  to  expose  the  whole  to  the  light  of  the  sun  for  a 
short  time,  or  longer  to  diffused  daylight. 

Before  this  can  be  done,  the  negative  must,  however,  be  fixed,  otherwise 
it  will  blacken:  this  is  done  temporarily  by  washing  with  a  solution  of 
potassium  bromide,  ten  grains  in  an  ounce  of  water,  and  then  rinsing  in 
common  water.  The  ultimate  fixing  is  effected  by  immersion  in  a  solution 
of  one  part  of  sodium  hyposulphite,  in  from  four  to  ten  parts  of  water: 
the  weaker  solution  should  be  used  hot,  about  82°  C.  (180°  F.),  and  the 
immersion  continued  until  the  yellow  tint  arising  from  the  undecomposed 
iodide  disappears :  finally,  repeatedly  washing  in  hot  water,  drying,  and 
saturating  with  white  wax,  terminates  the  process. 

The  positives  are  also  fixed  by  sodium  hyposulphite,  by  potassium  cyanide, 
or  by  ammonia;  all  of  which  act  by  removing  the  undecomposed  silver 
chloride.  The  conservation  of  the  positive  is  a  point  of  difficulty.  Mr. 
Malone  recommends  immersion  in  a  strong  solution  of  caustic  potassa, 
heated  to  about  82°  C. ;  a  change  of  tint  ensues,  and  greater  permanence  is 
acquired.  After  removal  of  the  alkali  and  any  sulphur  and  chlorine  com- 
pounds present,  the  picture  should  be  sized  and  hot-pressed,  or  varnished, 
keeping  the  finished  proof  most  carefully  excluded  from  sulphuretted 
vapors. 

Sir  John  Herschel  has  shown  that  a  great  number  of  other  substances  can 
be  employed  in  these  photographic  processes  by  taking  advantage  of  the 
singular  deoxidizing  effects  of  certain  portions  of  the  solar  rays.  Paper 
washed  with  a  solution  of  ferric  salt  becomes  capable  of  receiving  impres- 
sions of  this  kind,  which  may  afterwards  be  made  evident  by  potassium  fer- 
ricyanide,  or  gold  chloride.  Vegetable  colors  are  also  acted  upon  in  a  very  cu- 
rious and  apparently  definite  manner  by  the  different  parts  of  the  spectrum. 

The  daguerreotype,  the  announcement  of  which  was  first  made  in  the 
summer  of  1839,  by  M.  Daguerre,  who  had  been  occupied  with  this  subject 
from  182G,  if  not  earlier,  is  another  remarkable  instance  of  the  decomposing 
effects  of  the  solar  rays.  A  clean  and  highly  polished  plate  of  silvered 
copper  is  exposed  for  a  certain  period  to  the  vapor  of  iodine,  and  then 
transported  to  the  camera  obscura.  In  the  most  improved  state  of  the  pro- 
cess, a  very  short  time  suffices  for  effecting  the  necessary  change  in  the 
film  of  silver  iodide.  The  picture,  however,  only  becomes  visible  by  expos- 
ing it  to  the  vapor  of  mercury,  which  attaches  itself,  in  the  form  of  exceed- 

9 


98  LIGHT. 

ingly  minute  globules,  to  those  parts  which  have  been  most  acted  upon,  that 
is  to  say,  to  the  lights,  the  shadows  being  formed  by  the  dark  polish  of  the 
metallic  plate.  Lastly,  the  drawing  is  washed  with  sodium  hyposulphite, 
to  remove  the  undecomposed  silver  iodide  and  render  it  permanent. 

The  images  of  objects  thus  produced  bear  the  most  minute  examination 
with  a  magnifying  glass,  the  smallest  details  being  depicted  with  perfect 
fidelity. 

Great  improvements  have  been  necessarily  made  in  the  application  of 
this  beautiful  art  to  taking  portraits.  By  the  joint  use  of  bromine  and 
iodine  the  plates  are  rendered  far  more  sensitive,  and  the  time  of  sitting  is 
shortened  to  a  very  few  seconds.  In  fact,  the  sensitiveness  of  the  photo- 
graphic plate  has  been  so  increased,  that  excellently  denned  pictures  of 
objects  in  rapid  motion,  horses  jumping,  ships  sailing,  &c.,  have  been  ob- 
tained. When  the  operation  is  completed,  the  color  of  the  plate  is  much 
improved  by  the  deposition  of  an  exceedingly  thin  film  of  gold,  which  com- 
municates a  warm  purplish  tint,  and  removes  the  previous  dull  leaden-gray 
hue,  to  most  persons  very  oifensive. 

The  difficulty  of  obtaining  good  paper  for  the  talbotype  has  led  to  the  in- 
vention of  various  substitutes:  albumen  on  glass  and  collodion  are  used  with 
success;  a  soluble  iodide,  or  some  analogous  salt,  is  mixed  with  either 
liquid,  and  the  mixture  applied  to  a  glass  or  porcelain  plate,  dried,  and  im- 
mersed in  a  solution  of  silver  nitrate ;  thus  a  sensitive  coating  is  formed, 
upon  which  the  images  of  the  camera  or  microscope  are  thrown,  and  de- 
veloped by  subsequent  treatment  with  deoxidizing  agents,  —  either  pyro- 
gallic  acid,  gallic  acid,  or  a  ferrous  salt  may  be  used.  The  fixing  is  accom- 
plished by  sodium  hyposulphite.  The  result  is  either  negative  or  positive 
at  the  will  of  the  operator.  The  proofs  on  porcelain  or  glass  may  be  burned 
in,  and  perhaps  thus  rendered  indestructible  by  time. 

Etching  and  lithographic  processes,  by  combined  chemical  and  photo- 
graphic agency,  promise  to  be  of  considerable  utility.  The  earliest  is  that 
of  Niepce :  he  applied  a  bituminous  coating  to  a  metal  plate,  upon  which  an 
engraving  was  superimposed.  The  light  being  thus  partially  interrupted, 
acted  unequally  upon  tlie  varnish ;  a  liquid  hydro-carbon,  petroleum,  used 
as  a  solvent,  removed  the  bitumen  wherever  the  light  had  not  acted;  an 
engraving  acid  could  now  bite  the  unprotected  metal,  which  could  event- 
ually be  printed  from  in  the  usual  way.  Dr.  Donne  and  Dr.  Berres,  by 
submitting  the  daguerreotype  to  the  action  of  nitric  acid  and  its  vapor,  ob- 
tained etchings  from  which  proofs  could  be  taken.  Mr.  Grove,  by  using 
chlorine  evolved  by  voltaic  agency,  succeeded  in  obtaining  a  more  manage- 
able process  Very  successful  results  have  also  been  obtained  by  M.  Fizeau, 
who  submits  the  daguerreotype  to  the  action  of  a  mixture  of  dilute  nitric 
acid,  common  salt,  and  potassium  nitrate,  when  the  silver  only  is  attacked, 
the  mercurialized  portion  of  the  image  resisting  the  acid ;  an  etching  is  thus 
obtained  following  minutely  the  lights  and  shadows  of  the  picture.  To 
deepen  this  etching,  the  silver  chloride  formed  is  removed  by  ammonia,  the 
plate  is  boiled  in  caustic  potassa  and  again  treated  with  acid,  and  so  on  till  the 
etching  is  of  sufficient  depth.  In  extreme  cases  electro-gilding  is  resorted 
to,  and  an  engraving  acid  used  to  get  still  more  powerful  impressions. 

Among  the  latest  results  are  those  obtained  by  Mr.  Talbot  on  steel  plates: 
he  uses  a  mixture  of  potassium  bichromate  and  gelatin,  which  hardens  by 
exposure  to  the  light;  the  parts  not  affected  are  removed  by  washing. 
Platinum  tetrachloride  is  used  as  an  etching  liquid ;  it  has  the  advantage 
of  biting  with  greater  regularity  than  nitric  acid. 

The  bitumen  process  of  M.  Niepce  has  been  applied  to  lithographic  stone ; 
and  positives  obtained  from  negative  talbotypes  have  been  printed  off  by 
a  modification  of  the  ordinary  lithographic  process.  M.  Niepce  finds  that 
ether  dissolves  tiie  altered  bitumen,  while  naphtha,  or  benzol,  attacks,  by 
preference  the  bitumen  in.  its 


RADIATION    OF    HEAT. 


99 


RADIATION,  REFLECTION,    ABSORPTION,   AND   TRANS- 
MISSION  OP  HEAT. 

RADIATION  OF  HEAT. 

IF  a  red-hot  ball  be  placed  upon  a  metallic  support,  and  left  to  itself, 
cooling  immediately  commences,  and  only  stops  when  the  temperature 
of  the  ball  is  reduced  to  that  of  the  surrounding  air.  This  eft'ect  takes 
place  in  three  ways:  heat  is  conducted  away  from  the  ball  through  the 
substance  or  the  support;  another  portion  is  removed  by  the  convective 
power  of  the  air:  and  the  residue  is  thrown  oif  from  the  heated  body  in 
straight  lines  or  rays  which  pass  through  air  without  Interruption,  and 
become  absorbed  by  neighboring  objects  which  happen  to  be  presented 
to  their  impact. 

This  radiant  or  radiated  heat  resembles,  in  very  many  respects,  ordinary 
light;  it  moves  with  great  velocity;  it  suffers  reflection  from  surfaces;  it 
enters  and  traverses  media,  undergoing  at  the  same  time  refraction,  ab- 
sorption, and  polarization;  in  fact,  it  is  in  all  these  cases  obedient  to  the 
same  laws  which  regulate  the  corresponding  phenomena  in  optics. 

The  fact  of  the  reflection  of  heat  may  be  very  easily  proved.  If  a  person 
stand  before  a  fire  in  such  a  position  that  his  face  may  be  screened  by  the 
mantelshelf,  and  if  he  then  take  a  bright  piece  of  metal,  as  a  sheet  of 
tinned  plate,  and  hold  it  in  such  a  manner  that  the  fire  may  be  seen  by 
reflection,  a  distinct  sensation  of  heat  will  at  the  same  moment  be  felt. 

The  apparatus  best  fitted  for  studying  these  facts  consists  of  a  pair  of 
concave  metallic  mirrors  of  the  form  called  parabolic.  The  parabola  is  a 
curve  possessing  very  peculiar  properties,  one  of  the 
most  prominent  being  the  following: — A  tangent 
drawn  to  any  part  of  the  curve  makes  equal  angles 
with  two  lines,  one  of  which  proceeds  from  the  point 
where  the  tangent  touches  the  curve  in  a  direction 
parallel  to  what  is  called  the  axis  of  the  parabola, 
and  the  other  from  the  same  spot  through  a  point  in 
front  of  the  curve  called  the  focus.  It  results  from 
this  that  parallel  rays,  either  of  light  or  he-it,  falling 
upon  a  mirror  of  this  particular  curvature  in  a  di- 
rection parallel  with  the  axis  of  the  parabola,  will 
be  all  reflected  to  a  single  point  at  the  focus;  and 
rays  diverging  from  this  focus,  and  impinging  upon 
the  mirror,  will,  after  reflection,  become  parallel 
(fig.  M). 

For  practical  purposes  the  parabolic  reflector  is 

generally  replaced  by  a  spherical  mirror  of  but  little  extent  as  compared 
with  its  radius  of  curvature.  The  line  drawn  from  the  centre  of  the  cur- 
vature to  the  middle  of  the  reflector,  i.  e.,  the  radius  of  the  sphere,  is  the 
principal  axis,  and  the  middle  of  this  radius  is  the  focus  of  the  spherical 
reflector.  This  focus  exhibits  nearly  all  the  characters  of  the  focus  of  thepar- 
abolic  reflector.  The  spherical  reflector  is  much  more  easily  constructed  than 
the  parabolic;  it  has,  moreover,  the  advantage  that  evei-y  line  drawn  from 
the  centre  of  the  curvature  towards  the  surface  of  the  mirror  may  be 


Fig.  66. 


100 


RADIATION    OF    HEAT. 


looked  upon  as  an  axis  (collateral  axis),  and  the  middle  of  such  line  as  a 
focus  (collateral  focus),  and  used  as  such. 

If  two  such  mirrors  be  placed  opposite  to  each  other  at  a  considerable 
distance,  and  so  adjusted  that  their  axes  shall  be  coincident,  and  a  hot 
body  placed  in  the  focus  of  the  one,  while  a  thermometer  occupies  that  of 
the  other,  the  reflection  of  the  rays  of  heat  will  become  manifest  by 
their  effect  upon  the  instrument.  In  this  manner,  with  a  pair  of  by  no 
means  very  perfect  mirrors,  18  inches  in  diameter,  separated  by  an  interval 
of  20  feet  or  more,  amadou  or  gunpowder  may  be  readily  fired  by  a  red- 
hot  ball  in  the  focus  of  the  opposite  mirror  (fig.  67). 

Fig.  67. 


The  power  of  radiation  varies  exceedingly  with  different  bodies,  as  may 
be  easily  proved.  If  two  similar  vessels  of  equal  capacity,  and  constructed 
of  thin  metal,  one  having  its  surface  highly  polished,  while  that  of  the 
other  is  covered  with  lampblack,  be  filled  with  hot  water  of  the  same  tem- 
perature, and  their  rate  of  cooling  observed  from  time  to  time  with  a 
thermometer,  it  will  be  constantly  found  that  the  blackened  vessel  loses 
heat  much  faster  than  the  one  with  bright  surfaces  ;  and  since  both  are 
put  on  a  footing  of  equality  in  other  respects,  this  difference,  which  will 
often  amount  to  many  degrees,  must  be  ascribed  to  the  superior  emissive 
power  of  the  film  of  soot. 

By  another  arrangement,  a  numerical  comparison  can  be  made  of  these 
differences.  A  cubical  metallic  vessel  is  prepared,  each  of  whose  sides 
is  in  a  different  condition,  one  being  polished,  another  rough,  a  third  cov- 
ered with  lampblack,  &c.  The  vessel  is  filled  with  water,  kept  constantly 
at  100°  by  a  small  steam-pipe.  Each  of  its  sides  is  then  presented  in  suc- 
cession to  a  good  concave  mirror,  having  in  its  focus  one  of  the  bulbs  of 
the  differential  thermometer  before  described  (fig.  26),  the  bulb  itself 
being  blackened.  The  effect  produced  on  this  instrument  is  taken  as  a 
measure  of  the  comparative  radiating  powers  of  the  different,  surfaces. 
Sir  John  Leslie  obtained  by  this  method  of  experimenting  the  following 
results : 


Emissive  power. 
Lampblack  .         .         .100 
Writing-paper            .           98 
Glass                                .       90 

Emissive  power. 
Tarnished  lead     .         .     45 
Clean  lead         .         .         19* 
Polished  iron        .         .     15 

Graphite  ...           75 

Polished  silver          .         12 

*  The  supposed  influence  of  mere  difference  of  surface  has  been  called  in  question  by  Mellon  i, 
who  attributes  to  other  causes  the  effects  observed  by  Leslie  and  others,  among  which  super- 
ficial oxidation  and  differences  of  physical  condition  with  respect  to  hardness  and  density  are 
among  the  most  important.  With  metals  not  subject  to  tarnish,  scratching  the  surface  in- 
creases the  emissive  power  when  the  plates  have  been  i-olled  or  hammered,  ?'.  e.,  are  in  a  com- 
pressed state,  and  diminishes  it,  on  the  contrary,  when  the  metal  has  been  cast  and  carefully 
polished  without  burnishing.  In  the  case  of  ivory,  marble,  and  jet,  where  compression  cannot 
take  place,  no  difference  is  perceptible  in  the  radiating  power  of  polished  and  rough  surfaces. 
(Ann.  Ch.  Phys.,  Ixx.  435.) 


RADIATION  OF  HEAT.  101 

The  best  reflecting  surfaces  are  always  the  worst  radiators;  polished 
metal  reflects  nearly  all  the  heat  that  falls  upon  it,  while  its  radiating 
power  is  the  feeblest  of  any  substance  tried,  and  lampblack,  which  reflects 
nothing,  radiates  most  perfectly. 

The  power  of  absorbing  heat  is  in  direct  proportion  to  the  power  of 
emission.  The  polished  metal  mirror,  in  the  experiment  with  the  red-hot 
ball,  remains  quite  cold,  although  only  a  few  inches  from  the  latter;  or, 
again,  if  a  piece  of  gold  leaf  be  laid  upon  paper,  and  a  heated  iron  held 
over  it  until  the  paper  is  completely  scorched,  it  will  be  found  that  the  film 
of  metal  has  perfectly  defended  that  portion  beneath  it. 

The  faculty  of  absorption  seems  to  be  a  good  deal  influenced  by  color. 
Dr.  Franklin  found  that  when  pieces  of  cloth  of  various  colors  were  placed 
on  snow  exposed  to  the  feeble  sunshine  of  winter,  the  snow  beneath  became 
unequally  melted,  the  effect  being  always  in  proportion  to  the  depth  of  the 
color;  and  Dr.  Stark  has  since  obtained  a  similar  result  by  a  different 
method  of  experimenting.  According  to  the  late  researches  of  Melloni, 
this  effect  depends  less  on  the  color  than  on  the  nature  of  the  coloring 
matter  which  covers  the  surface  of  the  cloth.  According  to  Melloni,  color 
does  not  influence  absorption  when  the  heat  rays  are  emitted  from  a  non- 
luminous  source,  such  as  a  cube  filled  with  hot  water;  it  has,  however, 
great  effect  on  the  absorption  of  heat  rays  given  off  from  a  luminous  body, 
as  the  sun,  &c. 

These  facts  afford  an  explanation  of  two  very  interesting  and  important 
natural  phenomena,  namely,  the  origin  of  dew,  and  the  cause  of  the  land- 
and  sea-breezes  of  tropical  countries.  While  the  sun  remains  above  the 
horizon,  the  heat  radiated  by  the  surface  of  the  earth  into  space  is  com- 
pensated by  the  absorption  of  the  solar  beams;  but  when  the  sun  sets,  and 
the  supply  ceases,  while  the  emission  of  heat  goes  on  as  actively  as  before, 
the  surface  becomes  cooled  until  its  temperature  sinks  below  that  of  the 
air.  The  air  in  contact  with  the  earth  of  course  participates  in  this  re- 
duction of  temperature;  the  aqueous  vapor  present  speedily  reaches  its 
point  of  maximum  density,  and  then  begins  to  deposit,  moisture,  whose 
quantity  will  depend  upon  the  proportion  of  vapor  in  the  atmosphere,  and 
on  the  extent  to  which  the  cooling  process  has  been  carried. 

It  is  observed  that  dew  is  most  abundant  in  a  clear  calm  night,  suc- 
ceeding a  hot  day:  under  these  circumstances  the  quantity  of  vapor  in 
the  air  is  usually  very  great,  and  at  the  same  time  radiation  proceeds  with 
most  facility.  At  such  times  a  thermometer  laid  on  the  ground  will,  after 
some  time,  indicate  a  temperature  of  5°,  8°,  or  even  10°  below  that  of  the 
air  a  few  feet  higher.  Clouds  hinder  the  formation  of  dew  by  reflecting 
back  to  the  earth  the  heat  radiated  from  its  surface,  and  thus  preventing 
the  necessary  reduction  of  temperature;  and  the  same  effect  is  produced 
by  a  screen  of  the  thinnest  material  stretched  at  a  little  height  above  the 
ground.  In  this  manner  gardeners  often  preserve  delicate  plants  from 
destruction  by  the  frosts  of  spring  and  autumn.  The  piercing  cold  felt 
just  before  and  at  sunrise,even  in  the  height  of  summer,  is  the  consequence 
of  this  refrigeration  having  reached  its  maximum. 

Wind  also  effectually  prevents  the  deposition  of  dew,  by  constantly 
renewing  the  air  lying  upon  the  earth  before  it  has  had  its  temperature 
sufficiently  reduced  to  cause  condensation  of  moisture. 

Many  curious  experiments  may  be  made  by  exposing  on  the  ground  at 
night  bodies  which  differ  in  their  powers  of  radiation.  If  a  piece  of  black 
cloth  and  a  plate  of  bright  metal  be  thus  treated,  the  former  will  be  often 
found  in  the  morning  covered  with  dew,  while  the  latter  remains  dry. 

Land  and  sea  breezes  are  certain  periodical  winds  common  to  most  sea- 
coasts  within  the  tropics,  but  by  no  means  confined  to  those  regions.  It 
is  observed  that  a  few  hours  after  sunrise  a  breeze  springs  up  at  sea,  and 


102  TRANSMISSION  OF   HEAT. 

blows  directly  on  shore,  and  that  its  intensity  increases  as  the  day 
advances,  and  declines  and  gradually  expires  near  sunset.  Shortly  after- 
wards a  wind  arises  in  exactly  the  opposite  direction,  namely,  from  the 
land  towards  the  sea,  lasts  the  whole  of  the  night,  and  only  ceases  with 
the  reappearance  of  the  sun. 

It  is  easy  to  give  an  explanation  of  these  effects.  When  the  sun  shines 
at  once  upon  the  surface  of  the  earth  and  that  of  the  sea,  the  two  become 
unequally  heated,  because  the  water,  although  it  possesses  greater  power 
of  absorbing  heat,  is  yet  more  slowly  warmed,  in  consequence  of  its 
greater  capacity  for  heat,  and  the  greater  depth  to  which  the  rays  of  the 
sun  can  penetrate.  The  air  over  the  heated  surface  of  the  ground,  being 
expanded  by  heat,  rises,  and  has  its  place  supplied  by  colder  air  flowing 
from  the  sea,  producing  the  sea-breeze.  When  the  sun  sets,  both  sea  and 
land  begin  to  cool  by  radiation:  the  rate  of  cooling  of  the  latter  will,  how- 
ever, far  exceed  that  of  the  former,  and  its  temperature  will  rapidly  fall. 
The  air  above  becoming  cooled  and  condensed,  flows  outwards  in  obedience 
to  the  laws  of  fluid  pressure,  and  displaces  the  warmer  air  of  the  ocean. 
In  this  manner,  by  an  interchange  of  air  between  sea  and  land,  the  other- 
wise oppressive  heat  is  moderated,  to  the  great  advantage  of  those  who 
inhabit  such  localities.  The  land  and  sea  breezes  extend  to  a  small  distance 
only  from  shore,  but  afford,  notwithstanding,  essential  aid  to  coasting 
navigation,  since  vessels  on  either  tack  enjoy  a  fair  wind  during  the 
greater  part  of  both  day  and  night. 

TRANSMISSION  OF  HEAT;  DIATHERMANCY. 

Rays  of  heat,  in  passing  through  air,  receive  scarcely  more  obstruction 
than  those  of  light  under  similar  circumstances;  but  with  other  trans- 
parent media  the  case  is  different.  If  a  parabolic  mirror  be  taken,  and 
its  axis  directed  towards  the  sun,  the  rays  both  of  heat  and  light  will  be 
reflected  to  the  focus,  which  will  exhibit  a  temperature  sufficiently  high 
to  fuse  a  piece  of  metal,  or  fire  a  combustible  body.  If  a  plate  of  glass  be 
now  placed  between  the  mirror  and  the  sun,  the  effect  will  be  perceptibly 
diminished. 

Now,  let  the  same  experiment,  be  made  with  the  heat  of  a  kettle  filled 
with  boiling  water ;  the  heat  will  be  concentrated  by  reflection  as  before, 
but,  on  interposing  the  glass,  the  heating  effect  at  the  focus  will  be  reduced 
to  nothing.  Thus,  the  rays  of  heat  coming  from  the  sun  traverse  even 
glass  in  considerable  quantity,  but  not  so  easily  as  air,  whilst  rays  from 
hot  water  are  entirely  stopped  by  glass. 

In  the  year  1833,  M.  Melloni  published  the  first  of  a  series  of  exceed- 
ingly valuable  researches  on  this  subject,  which  are  to  be  found  in  detail 
in  various  volumes  of  the  Annales  de  Chimie  et  d-e  Physique.*  It  will  be 
necessary,  in  the  first  instance,  to  describe  the  method  of  operation 
followed  by  this  philosopher. 

Not  long  before,  two  very  remarkable  facts  had  been  discovered:  Orsted, 
in  Copenhagen,   showed  that  a  current  of  electricity, 
however  produced,   exercises  a  singular  and  perfectly  Fig.  68. 

definite  action  on  a  magnetic  needle;  and  Seebeck,  in     — » 

Berlin,  found  that  an  electric  current  may  be  generated     '        -r 
by  the  unequal  effects  of  heat  on  different  metals  in  con-       ^  -=^&^==-T^. 
tact.     If   a  wire    conveying  an    electrical   current  be 
brought  near  a  magnetic  needle,  the   latter  will  imme- 
diately alter  its  position  and  assume  a  new  one  as  nearly 
perpendicular  to   the  wire  as  the  mode  of  suspension 
and  the  magnetism  of  the  earth  will  permit.     Vi  hen  the 
wire,  for  example,  is  placed  directly  over   tha   needle 

*  Translated  also  in  Taylor's  "  Scientific  Memoirs." 


RADIATION  OF  HEAT. 


103 


Fig. 


and  parallel  to  its  length,  while  the  current  it  carries  travels  from  north  to 
south,  the  needle  is  deflected  from  its  ordinary  direction,  and  the  north 
pole  driven  to  the  eastward.  When  the  current  is  reversed,  the  same  pole 
deviates  to  an  equal  amount  towards  the  west.  Placing  the  wire  below 
the  needle  instead  of  above,  produces  the  same  effect  as  reversing  the 
current. 

When  the  needle  is  subjected  to  the  action  of  two  currents  in  oppo- 
site directions,  the  one  above  and  the  other  below,  they  will  obviously 
concur  in  their  effects.  The  same  thing  happens  when  the  wire  carrying 
the  current  is  bent  upon  itself,  and  the  needle  placed  between  the  two  por- 
tions; and  since  every  time  the  bending  is  repeated,  a  fresh  portion  of  the 
current  is  made  to  act  in  the  same  manner  upon  the  needle,  it  is  easy  to 
see  how  a  current,  too  feeble  to  produce  any  effect  when  a  simple  straight 
wire  is  employed,  may  be  made  by  this  contrivance  to  exhibit  a  powerful 
action  on  the  magnet.  It  is  on  this  principle 
that  instruments  called  galvanometers,  galvano- 
scopes,  or  multipliers,  are  constructed ;  they  serve 
not  only  to  indicate  the  existence  of  electrical 
currents,  but  to  show,  by  the  effects  upon  the 
needle,  the  direction  in  which  they  are  moving. 
The  delicacy  of  the  instrument  can  be  extraor- 
dinarily increased  by  the  use  of  a  very  long 
coil  of  wire  and  two  needles  of  equal  strength, 
and  with  opposite  poles  conjoined  (fig.  82).  These  needles  are  hung  by 
untwisted  silk,  one  between  the  coils  and  the  other  above  them,  so  that  the 
current  acts  in  the  same  direction  on  both.  The  thickness  of  the  wire  has 
some  influence  on  the  delicacy  of  the  instrument.  For  the  following 
experiments  it  should  not  be  less  than  J?  of  an  inch  thick. 

Where  two  pieces  of  different  metals,  connected  together  at  each  end, 
have  one  of  their  joints  more  heated  than  the  other,  an  electric  current  is 
immediately  set  up.  Of  all  the  metals  tried, 
bismuth  and  antimony  form  the  most  power- 
ful combination.  A  single  pair  of  bars  hav- 
ing one  of  their  junctions  heated  in  the  man- 
ner shown  (fig.  70),  can  develop  a  current 
strong  enough  to  deflect  a  compass-needle 
placed  within ;  and,  by  arranging  a  number 
in  a  series  and  heating  their  alternate  ends, 
the  intensity  of  the  current  may  be  very 
much  increased.  Such  an  arrangement  is 
called  a  thermo-electric  pile.  Melloni  con- 
structed a  very  small  thermo-electric  pile  of 

this  kind,  containing  fifty-five  slender  bars  of  bismuth  and  antimony,  laid  side 
by  side  and  soldered  together  at  their  alternate  ends,  as  shown  in  natural  size 
in  fig.  71.  He  connected  this  pile  with  an  exceed- 
ingly delicate  multiplier,  and  found  himself  in 
the  possession  of  an  instrument  for  measuring 
small  variations  of  temperature,  far  surpassing 
in  delicacy  the  air-thermometer  in  its  most  sen- 
sitive form,  and  having  great  advantages  in 
other  respects  over  that  instrument  when  em-  iui 

ployed  for  the  purposes  to  which  he  devoted  it.     ^^^:pm°ro^5l^.^l~:vw^ 

The  substances  whose  powers  of  transmission     j__li_Z!!r 
were  to  be  examined  were   cut  into  plates  of  a     |  —^^^j.u.TJLL.^.r-pr — ^^j 
determinate    thickness,    and,    after    being    well 
polished,  arranged  in  succession  in  front  of  the  r1 

little  pile,  the  extremity  of  which  was  blackened  j 


Fig. 


104 


TRANSMISSION    OF    HEAT. 


to  promote  the  absorption  of  the  rays.  A  perforated  screen,  the  area  of 
whose  aperture  equalled  that  of  the  face  of  the  pile,  was  placed  between 
the  source  of  heat  and  the  body  under  trial,  while  a  second  screen  served 
to  intercept  all  radiation  until  the  moment  of  the  experiment. 

After  much  preliminary  labor,  for  the  purpose  of  testing  the  capabilities 
of  the  apparatus  and  the  value  of  its  indications,  an  extended  series   of 

Fig.  72. 


researches  was  undertaken  and  carried  on  during  a  long  period  with  great 
success;  some  of  the  most  curious  results  are  given  in  the  annexed  table. 
Four  different  sources  of  heat  were  employed  in  these  experiments, 
differing  in  their  nature  and  in  their  degrees  of  intensity:  the  naked  flame 
of  an  oil-lamp ;  a  coil  of  platinum  wire  heated  to  redness ;  blackened  cop- 
per at  390° ;  and  the  same  heated  to  100°. 


Transmission  of  100  rays 

of  heat  from 

Substances. 

e, 

. 

30 

if 

(Thickness  of  plate  0-1  inch,  nearly.) 

2  § 
3-= 

§;§. 

1,1 

O 

«s 

^l 

^l 

Rock-salt,  transparent  and  colorless   . 

92 

92 

92 

92 

Fluor-spar,  colorless        ..... 

78 

69 

42 

33 

Rock-salt,  muddy         ...... 

65 

65 

65 

65 

Beryl       ........ 

54 

23 

13 

0 

46 

38 

24 

20 

Iceland  spar    ....... 

39 

28 

6 

0 

Plate-glass  ........ 

39 

24 

6 

0 

Rock-crystal  ....... 

88 

28 

6 

0 

Rock-crystal,  brown    ...... 

37 

28 

6 

0 

Tourmaline,  dark-green  ..... 

18 

16 

3 

0 

Citric  acid,  transparent       ..... 

11 

2 

0 

0 

Alum,  transparent  ...... 

9 

2 

0 

0 

Sugar-candy        ....... 

8 

0 

0 

0 

Fluor-spar,  green,  translucent  • 

8 

6 

4 

3 

Ice,  pure  and  transparent  ..... 

6 

0 

0 

0 

On  examining  this  remarkable  table,  which  is  an  abstract  of  one  much 
more  extensive,  the  first  thing  that  strikes  the  eye  is  the  want  of  connection 
between  the  power  of  transmitting  heat  and  that  of  transmitting  light. 
Taking,  for  instance,  the  oil-lamp  as  the  source  of  heat:  out  of  the  quan- 
tity of  heat  represented  by  100  rays  falling  upon  the  pile,  the  proportion 


TRANSMISSION    OF    HEAT.  105 

transmitted  by  similar  plates  of  rock-salt,  glass,  and  alum,  maybe  expressed 
by  the  numbers,  9li,  39,  and  9;  and  yet  these  bodies  are  equally  trans- 
parent with  respect  to  light.  Generally  speaking,  color  was  found  to 
interfere  with  the  transmissive  power,  but  to  a  very  unequal  extent:  thus, 
in  fluor-spar,  colorless,  greenish,  and  deep  green,  the  quantities  transmitted 
were  78,  46,  and  8,  while  the  difference  between  colorless  and  brown  rock- 
crystal  was  only  1.  Bodies  absolutely  opaque,  as  wood,  metals,  and  black 
marble,  stopped  the  rays  completely,  although  it  was  found  that  the  faculty 
of  transmission  was  possessed,  to  a  certain  extent,  by  some  which  were 
neai'ly  in  that  condition,  as  thick  plates  of  brown  quartz,  black  mica,  and 
black  glass. 

A  great  difference  is  noticed  in  heat-rays  derived  from  different  sources. 
Out  of  100  rays  from  each  source  which  fell  on  rock-salt,  the  same  pro- 
portion was  always  transmitted  whether  the  rays  proceeded  from  the  in- 
tensely heated  flame,  the  red-hot  platinum  wire,  or  the  copper  at  390°  or 
100°;  but  this  is  true  of  no  other  substance  in  the  list.  In  the  case  of 
plate-glass,  we  have  the  numbers  39,  24,  G,  and  0  as  representatives  of  the 
comparative  quantities  of  heat  transmitted  through  the  plate  from  each 
source ;  or  in  three  varieties  of  fluor-spar,  as  in  the  following  statement : 

Flame.  Red  heat.  390°.  100°. 

Colorless                  .    78                69  42  33 

Greenish                       46                38  24  20 

Dark  green              .      8                  6                  4  3 

One  substance,  beryl,  out  of  100  rays  from  the  intensely  heated  source, 
suffers  54  to  pass;  and  out  of  the  same  number  (that  is,  an  equal  quantity 
of  heat)  from  metal  at  100°  none  at  all;  whilst  another  substance,  fluor- 
spar, transmits  rays  from  the  two  sources  mentioned  in  the  proportion  of 
8  to  3. 

These,  and  many  other  curious  phenomena,  are  fully  and  completely  ex- 
plained on  the  supposition,  that  among  the  invisible  rays  of  heat  differences 
are  to  be  found  exactly  analogous  to  those  differences  between  rays  of  light 
which  we  are  accustomed  to  call  colors.  Hock-salt  and  air  are  the  only  sub- 
stances yet  known  which  are  truly  diathermanous,  or  equally  transparent  to 
all  kinds  of  heat-rays :  they  are  to  the  latter  what  white  glass  or  water  is 
to  light;  they  suffer  rays  of  every  description  to  pass  with  equal  facility. 
All  other  bodies  act  like  colored  glasses,  absorbing  certain  rays  more  abund- 
antly than  the  rest,  and  coloring,  as  it  were,  the  heat  which  passes  through 
them. 

These  heat-tints  have  no  direct  relation  to  ordinary  colors;  their  exist- 
ence is,  nevertheless,  almost  as  clearly  made  out  as  that  of  the  colored 
rays  of  the  spectrum.  Bodies  at  a  comparatively  low  temperature  emit 
rays  of  such  a  tint  only  as  to  be  transmissible  by  a  few  substances:  as  the 
temperature  rises,  rays  of  other  heat-colors  begin  to  make  their  appearance, 
and  transmission  of  some  portion  of  these  rays  takes  place  through  a  great 
number  of  bodies;  while  at  the  temperature  of  intense  ignition  we  find 
rays  of  all  colors  thrown  out,  some  of  which  will  certainly  find  their  way 
through  a  great  variety  of  substances.  The  kind  of  rays  emitted  by  dif- 
ferent bodies  of  the  same  temperature  is  by  no  means  the  same,  but  seems 
materially  to  depend  on  the  nature  of  the  radiating  body.  When  a  bundle 
of  heterogeneous  rays  passes  through  a  medium,  those  of  one  kind  are 
powerfully  absorbed,  while  those  of  another  are  not  affected.  By  their 
transmission  through  the  body  the  rays  have  undergone  a  sifting:  if  now 
these  sifted  rays  be  passed  through  a  second  plate  of  the  same  medium,  a 
much  smaller  proportional  loss  will  occur  than  in  the  case  of  the  first  plate, 
because  the  rays  which  the  medium  readily  takes  up  are  mostly  wanting, 


106 


TRANSMISSION    OF   HEAT. 


while  those  which  easily  pass  through  the  body  in  question  are  present  in 
more  notable  quantity.  The  same  thing  happens  when  a  number  of  plates 
are  interposed;  the  rays  after  traversing  one  plate  are  but  little  inter- 
rupted by  others  of  a  similar  nature. 

By  cutting  rock-salt  into  prisms  and  lenses,  it  is  easy  to  show  that 
radiated  heat  may  be  refracted  like  ordinary  light,  and  its  beams  made  to 
converge  or  diverge  at  pleasure;  and,  lastly,  to  complete  the  analogy,  it 
has  been  shown  to  manifest  the  phenomena  of  interference,  and  to  be 
susceptible  of  polarization  by  transmission  through  plates  of  double-re- 
fracting minerals,  in  the  manner  as  light  itself. 

The  absorptive  power  of  gases  and  vapors  for  rays  of  heat  by  which 
they  are  traversed  had  long  been  neglected  ;  and  it  is  only  recently  that 
we  have  become  indebted  to  Professor  Tyndall  and  Professor  Magnus  for 
some  researches  upon  this  subject.  The  absorptive  power  of  perfectly  dry 
air,  of  oxygen,  nitrogen,  and  hydrogen  in  the  state  of  purity  is  very  small ; 
the  absorptive  power  of  compound  gases  and  vapors,  e.  g.  of  water-vapor, 
carbonic  oxide,  carbonic  acid,  and  more  especially  of  olefiant  gas,  ammonia, 
and  the  vapors  of  volatile  oils,  is  much  greater.  The  following  table  gives, 
according  to  Tyndall,  the  relative  absorptive  powers  of  different  gases  for 
dark  rays  of  heat  emanating  from  copper  at  270°,  when  the  gases  are  ex- 
amined under  a  pressure  of  one  atmosphere: — 


Atmospheric  air  . 
Oxygen     . 
Nitrogen 
Hydrogen 
Chlorine       . 
Hydrochloric  acid 
Carbon  monoxide 


1 
1 
1 
1 

39 
62 
90 


Carbon  dioxide     . 
Nitrogen  monoxide 
Hydrogen  sulphite 
Marsh  gas 
Sulphurous  oxide 
Olefiant  gas 
Ammonia 


.  90 
355 

.  390 
403 

.  710 
970 

1195 


The  absorptive  power  of  a  gas  increases  with  an  increases  of  the  density, 
but  is,  in  the  case  of  gases  endowed  with  a  high  absorptive  power,  by  no 
means  proportionate  to  the  density. 

Rays  of  heat  of  the  above  description  are  not  capable  of  passing  through 
a  tube  3  feet  long  filled  with  ammonia  of  the  ordinary  pressure  of  the  at- 
mosphere; such  a  layer  of  ammonia,  though  quite  colorless  and  transparent 
to  light,  is  perfectly  impermeable  (it  might  be  said  black)  to  heat.  The 
element  chlorine,  though  colored  and  less  transparent  to  light,  allows  the 
rays  of  heat  to  pass  more  freely  than  the  compound  hydrochloric  acid, 
which  is  colorless  and  more  transparent  to  light.  These  examples  show 
that  the  absorptive  power  of  gases  for  rays  of  heat  is  perfectly  independent 
of  that  for  rays  of  light. 

From  Tyndall's  experiments  it  appears  also  that  vapor  of  water,  weight 
for  weight,  transcends  all  other  gases  in  heat-absorbing  power;  so  much, 
indeed,  that  the  aqueous  vapor  in  the  air,  though  not  amounting  on  the 
average  to  more  than  0-45  per  cent,  of  the  whole,  exerts  an  absorptive 
action  on  heat-rays  many  times  greater  than  the  air  through  which  it  is 
diffused.  This  great  absorbing  power  of  water-vapor  has  a  powerful  effect 
in  checking  the  cooling  down  of  the  earth's  surface  by  radiation ;  and  it 
is  in  great  part  from  this  cause  that  in  moist  climates,  like  that  of  Eng- 
land, the  range  of  temperature  between  night  and  day,  and  between  summer 
and  winter,  is  so  much  less  than  in  drier  climates  under  the  same  latitude. 

It  has  'been  established  by  experiment,  and  likewise  theoretically  de- 
monstrated by  Kirchhoff,  that  of  two  bodies,  the  one  which  has  the  greater 
power  of  absorbing  rays  of  heat,  possesses  also  the  greater  power  of 
radiating  them,  and  that  the  law  mentioned  on  page  92,  according  to 
which  the  power  of  absorbing  heat  is  in  direct  proportion  to  the  power  of 
emission,  holds  good  also  for  gases. 


MAGNETISM. 


MAGNETISM. 

A  PARTICULAR  species  of  iron  ore  has  long  been  remarkable  for  its  prop- 
J_\_  erty  of  attracting  small  pieces  of  iron,  and  causing  them  to  adhere 
to  its  surface;  it  is  called  loadstone,  or  magnetic  iron  ore. 

If  a  piece  of  this  loadstone  be  carefully  examined,  it  will  be  found  that 
the  attractive  force  for  particles  of  iron  is  greatest  at  certain  particular 
points  of  its  surface,  while  elsewhere  it  is  much  diminished  or  even  alto- 
gether absent.  These  attractive  points  are  denominated  poles,  and  the 
loadstone  itself  is  said  to  be  endowed  with  magnetic  polarity. 

If  one  of  the  pole-surfaces  of  a  natural  loadstone  be  rubbed  in  a  partic- 
ular manner  over  a  bar  of  steel,  its  characteristic  properties  will  be  com- 
municated to  the  bar,  which  will  then  be  found  to  attract  iron-filings  like  the 
loadstone  itself.  Further,  the  attractice  force  will  appear  to  be  greatest  at 
two  points  situated  very  near  the  extremities  of  the  bar,  and  least  of  all 
towards  the  middle.  The  bar  of  steel  so  treated  is  said  to  be  magnetized, 
or  to  constitute  an  artificial  magnet. 

When  a  magnetized  bar  or  natural  magnet  is  suspended  at  its  centre  in 
any  convenient  manner,  so  as  to  be  free  to  move  in  a  horizontal  plane,  it  is 
always  found  to  assume  a  particular  direction  with  regard  to  the  earth,  one 
end  pointing  nearly  north  and  the  other  nearly  south.  If  the  bar  be  moved 
from  this  position,  it  will  tend  to  reassume  it,  and,  after  a  few  oscillations, 
settle  at  rest  as  before.  The  pole  which  points  towards  the  astronomical 
north  is  usually  distinguished  as  the  north  pole  of  the  bar,  and  that  which 
points  southward,  as  the  south  pole.  A  suspended  magnet,  either  natural 
or  artificial,  of  symmetrical  form,  serves  to  exhibit  certain  phenomena  of 
attraction  and  repulsion  in  the  presence  of  a  second  magnet,  which  de- 
serve particular  attention.  When  a  north  pole  is  presented  to  a  south 
pole,  or  a  south  pole  to  a  north,  attraction  ensues  between  them;  the  ends 
of  the  bars  approach  each  other,  and,  if  permitted,  adhere  with  considerable 
force;  when,  on  the  other  hand,  a  north  pole  is  brought  near  a  second 
north  pole,  or  a  S'mth  pole  near  another  south  pole,  mutual  repulsion  is  ob- 
served, and  the  ends  of  the  bars  recede  from  each  other  as  far  as  possible. 
Poles  of  an  opposite  name  attract,  and  of  a  similar  name  repel  each  other.  Thus, 
a  small  bar  or  needle  of  steel,  properly  magnetized  and  suspended,  and 
having  its  poles  marked,  becomes  an  instrument  fitted  not  only  to  discover 
the  existence  of  magnetic  power  in  other  bodies,  but  to  estimate  the  kind 
of  polarity  affected  by  their  different  parts. 

A  piece  of  soft  iron  brought  into  the  neighborhood  of  a  magnet  acquires 
itself  magnetic  properties:  the  intensity  of  the  power  thus  conferred  de- 
pends upon  that  of  the  magnet  and  upon  the  interval  which  divides  the 
two,  becoming  greater  as  that  interval  decreases,  and  greatest  of  all  when 
in  actual  contact.  The  iron,  iinder  these  circumstances,  is  said  to  be  mag- 
netized by  induction  or  influence,  and  the  effect,  which  in  an  instant 
reaches  its  maximum,  is  at  once  destroyed  by  removing  the  magnet. 

When  steel  is  substituted  for  iron  in  this  experiment,  the  inductive  action 
is  hardly  perceptible  at  first,  and  only  becomes  manifest  after  the  lapse  of 
a  certain  time:  in  this  condition,  when  the  steel  bar  is  removed  from  the 
magnet,  it  retains  a  portion  of  the  induced  polarity.  It  becomes,  indeed, 


108 


MAGNETISM. 


Fig.  73. 


a  permanent  magnet,  similar  to  the  first,  and  retains  its  peculiar  properties 
for  an  indefinite  period. 

A  particular  name  is  given  to  this  resistance  which  steel  always  offers  in 
a  greater  or  less  degree  both  to  the  development  of  magnetism  arid  its  sub- 
sequent destruction;  it,  is  called  specific  coercive  power. 

The  rule  which  regulates  the  induction  of  magnetic  polarity  in  all  cases 
is  exceedingly  simple,  and  most  important  to  be  remembered.  The  pole 
produced  is  always  of  the  opposite  name  to  that  which  produced  it,  a 

north  pole  developing  south  polarity, 
and  a  south  pole  north  polarity.  The 
north  pole  of  the  magnet  figured  in  the 
sketch  induces  south  polarity  in  all  the 
nearer  extremities  of  the  pieces  of  iron 
or  steel  which  surround  it,  and  a  state 
similar  to  its  own  in  all  the  more  remote 
extremities.  The  iron  thus  magnetized 
is  capable  of  exerting  a  similar  induc- 
tive action  on  a  second  piece,  and  that 
upon  a  third,  and  so  to  a  great  number, 
the  intensity  of  the  force  diminishing 
as  the  distance  from  the  permanent 
magnet  increases.  It  is  in  this  way 
that  a  magnet  is  enabled  to  hold  up  a 
number  of  small  pieces  of  iron,  or  a 
bunch  of  filings,  each  separate  piece 
becoming  a  magnet  for  the  time  by  in- 
duction. 

Magnetic  polarity,  similar  in  degree  to  that  which  iron  presents,  has 
been  found  only  in  some  of  the  compounds  of  iron,  in  nickel  arid  in  cobalt. 
Magnetic  attractions  and  repulsions  are  not  in  the  slightest  degree  inter- 
fered with  by  the  interposition  of  substances  destitute  of  magnetic  proper- 
ties. Thick  plates  of  glass,  shellac,  metals,  wood,  or  of  any  substances 
except  those  above  mentioned,  may  be  placed  between  a  magnet  and  a  sus- 
pended needle,  or  a  piece  of  iron  under  its  influence,  the  distance  being 
preserved,  without  the  least  perceptible  alteration  in  its  attractive  power-, 
or  force  of  induction. 

One  kind  of  polarity  cannot  be  exhibited  without  the  other.  In  other 
words,  a  magnetic  pole  cannot  be  insulated.  If  a  magnetized  bar  of  steel 
be  broken  at  its  neutral  point,  or  in  the  middle,  each  of  the  broken  ends 
acquires  an  opposite  pole,  so  that  both  portions  of  the  bar  become  perfect 
magnets;  and,  if  the  division  be  carried  still  further,  if  the  bar  be  broken 
into  a  hundred  pieces,  each  fragment  will  be  a  complete  magnet,  having 
its  own  north  and  south  poles. 

This  experiment  serves  to  show  very  clearly  that  the  apparent  polarity 
of  the  bar  is  the  consequence  of  the  polarity  of  each  individual  particle, 


Fig.  74. 


the  poles  of  the  bar  being  merely  points  through  which  the  resultants  of 
all  these  forces  pass ;  the  largest  magnet  is  made  up  of  an  immense  number 


MAGNETISM.  109 

of  little  magnets  regularly  arranged  side  by  side,  all  having  their  north 
poles  looking  one  way,  and  their  south  poles  the  other.  The  middle  portion 
of  such  a  system  cannot  possibly  exhibit  attractive  or  repulsive  effects  on 
an  external  body,  because  each  pole  is  in  close  juxtaposition  with  one  of 
an  opposite  name  and  of  equal  power;  hence  their  forces  will  be  exerted 
in  opposite  directions  and  neutralize  each  other's  influence.  Such  will  not 
be  the  case  at  the  extremities  of  the  bar;  there  uncoinpensated  polarity 
will  be  found  capable  of  exerting  its  specific  power. 

This  idea  of  regular  polarization  of  particles  of  matter  in  virtue  of  a 
pair  of  opposite  and  equal  forces,  is  not  confined  to  magnetic  phenomena; 
it  is  the  leading  principle  in  electrical  science,  and  is  constantly  reproduced 
in  some  form  or  other  in  every  discussion  involving  the  consideration  of 
molecular  forces. 

Artificial  steel  magnets  are  made  in  a  great  variety  of  forms:  such  as 
small  light  needles,  mounted  with  an  agate  cap  for  suspension  upon  a  fine 
point;  straight  bars  of  various  kinds;  bars  curved  into  the  shape  of  a 
horse-shoe,  &c.  All  these  have  regular  polarity  communicated  to  them  by 
certain  processes  of  rubbing  or  touching  with  another  magnet,  which  re- 
quire care,  but  are  not  otherwise  difficult  of  execution.  When  great  power 
is  wished  for,  a  number  of  bars  may  be  screwed  together,  with  their  similar 
ends  in  contact,  and  in  this  way  it  is  easy  to  construct  permanent  steel 
magnets  capnble  of  sustaining  great  weights.  To  prevent  the  gradual 
destruction  of  magnetic  force,  which  would  otherwise  occur,  it  is  usual  to 
arm  each  pole  with  a  piece  of  soft  iron  or  keeper,  which,  becoming  mag- 
netized by  induction,  serves  to  sustain  the  polarity  of  the  bar,  and  in  some 
cases  even  increases  its  energy. 

The  direction  spontaneously  assumed  by  a  suspended  needle  indicates 
that  the  earth  itself  has  the  properties  of  an  enormous  magnet,  whose 
south  magnetic  force  is  concentrated  in  the  northern  hemisphere.  A  line 
joining  the  two  poles  of  such  a  needle  or  bar  indicates  the  direction  of  the 
so-called  magnetic  meridian  of  the  place,  which  is  a  vertical  plane  coincident 
with  the  direction  of  the  needle. 

The  magnetic  meridian  of  a  place  is  not  usually  coincident  with  its  geo- 
graphical meridian,  but  makes  with  the  latter  a  certain  single  called  the 
declination  of  the  needle. 

The  amount  of  the  declination  of  the  needle  from  the  true  north  and 
south  not  only  varies  at  different  places,  but  in  the  same  place  is  subject 
to  daily,  yearly,  and  secular  fluctuations,  which  are  called  the  variations 
of  declination.  Thus,  at  the  commencement  of  the  17th  century,  the  de- 
clination, in  London,  was  eastward;  in  1660  it  was  0;  that  is,  the  needle 
pointed  due  north  and  south.  Afterwards  it  became  westerly,  slowly  in- 
creasing until  the  year  1818,  when  it  reached  24°  3CK,  since  which  time  it 
has  been  slowly  diminishing,  and,  in  the  present  year  (1868)  it  is  20°  10X. 

Of  late  the  march  of  the  daily  variations  of  declination  has  been  care- 
fully compared  with  the  positions  of  the  sun  as  well  as  the  moon  at  the 
corresponding  period.  This  inquiry,  suggested  by  General  Sabine,  and 
carried  on  for  a  number  of  years  in  several  localities,  has  led  to  the  re- 
markable result  that  these  celestial  bodies  exert  a  definite  influence  upon 
the  magnetic  needle,  and  must  therefore  be  considered  as  magnets,  like  the 
earth  itself. 

If  a  steel  bar  be  supported  on  a  horizontal  axis  passing  exactly  through 
its  centre  of  gravity,  it  will  of  course  remain  equally  balanced  in  any 
position  in  which  it  may  happen  to  be  placed;  if  the  bar  so  adjusted  be 
then  magnetized,  it  will  be  found  to  take  a  permanent  direction,  the  north 
pole  being  downwards,  and  the  bar  making,  in  London,  an  angle  of  about 
68°,  with  a  horizontal  plane  passing  through  the  axis.  This  is  called  the 
dip  or  inclination  of  the  needle,  and  shows  the  direction  in  which  the  force 
10 


110  MAGNETISM. 

of  terrestrial  magnetism  is  most  energetically  exerted.  The  amount  of  this 
dip  is  different  in  different  latitudes.  Near  the  equator  it  is  very  small, 
the  needle  remaining  nearly  or  quite  horizontal;  as  the  latitude  increases, 
the  dip  becomes  more  decided ;  and  over  the  magnetic  pole  the  bar  becomes 
completely  vertical.  Such  a  situation  is,  in  fact,  to  be  found  in  the  northern 
hemisphere,  considerably  south  of  the  geographical  pole,  on  the  west  coast 
of  Boothia  Felix,  lat.  70°  5'  N.  and  long.  96°  46'  W.  ;  the  dipping-needle 
has  here  been  seen  to  point  directly  downwards,  while  the  horizontal  or 
compass-needle  ceased  to  traverse.  In  the  southern  hemisphere  it  is  the 
south  pole  which  dips.  The  position  of  the  south  magnetic  pole  has  been 
determined  by  the  observations  of  Captain  James  Ross  to  be  about  lat. 
73°  S.  and  long.  180°  E. 

By  observing  a  great  number  of  points  near  the  equator  in  which  the 
dip  becomes  reduced  to  nothing,  a  line,  cutting  the  equator  in  two  points, 
may  be  traced  around  the  earth,  called  the  magnetic  equator,  and  on  both 
sides,  a  number  of  smaller  closed  curves  called  lines  of  equal  dip.  These 
lines  present  great  irregularities  when  compared  with  the  equator  itself 
and  the  parallels  of  latitude,  the  magnetic  equator  deviating  from  the  ter- 
restrial one  as  much  as  12°  at  its  point  of  greatest  divergence.  Like  the 
horizontal  declination,  the  dip  is  also  subject  to  change  at  the  same  place. 
Observations  have  not  yet  been  made  during  sufficient  time  to  determine 
accurately  the  law  and  rate  of  alteration,  and  great  practical  difficulties 
exist  also  in  the  construction  of  the  instruments.  In  the  year  1773,  it  was 
about  72°:  in  London  at  the  present  time  it  is  67°  57/. 

The  inductive  power  of  the  magnetism  of  the  earth  may  be  shown  by 
holding  in  a  vertical  position  a  bar  of  very  soft  iron;  the  lower  end  will 
be  found  to  possess  north  polarity,  and  the  upper,  the  contrary  state.  On 
reversing  the  bar,  the  poles  are  also  reversed.  All  masses  of  iron  what- 
ever, when  examined  by  a  suspended  needle,  will  be  found  in  a  state  of 
magnetic  polarity  by  the  influence  of  the  earth;  iron  columns,  tools  in  a 
smith's  shop,  fire-irons,  and  other  like  objects,  are  all  usually  magnetic, 
and  those  made  of  steel  permanently  so.  On  board  ship,  the  presence  of 
so  many  large  masses  of  iron — guns,  anchors,  water-tanks,  &c.,  —  thus 
polarized  by  the  earth,  causes  a  derangement  of  the  compass-needles  to  a 
very  dangerous  extent:  happily  a  plan  has  been  devised  for  determining 
the  amount  of  this  local  attraction  in  different  positions  of  the  ship,  and 
making  suitable  corrections. 

The  mariner's  compass,  which  is  nothing  more  than  a  suspended  needle 
attached  to  a  circular  card  marked  with  the  points,  was  not  in  general  use 
in  Europe  before  the  year  1300,  although  the  Chinese  have  had  it  from  very 
early  antiquity.  Its  value  to  the  navigator  is  now  very  much  increased  by 
correct  observations  of  the  exact  amount  of  the  declination  in  various 
parts  of  the  world. 

Probably  every  substance  in  the  world  contributes  something  to  the 
magnetic  action  of  the  earth;  for  according  to  the  latest  discoveries  of 
Faraday,  magnetism  is  not  peculiar  to  those  substances  which  have  more 
especially  been  called  magnetic,  such  as  iron,  nickel,  cobalt;  but  it  is  the 
property  of  all  metals,  though  to  a  much  smaller  degree.  Very  powerful 
magnets  are  required  to  show  this  remarkable  fact.  Large  horse-shoe 
magnets,  made  by  the  action  of  the  electric  current,  are  most  proper.  The 
magnetic  action  on  different  substances  which  are  capable  of  being  easily 
moved,  differs  not  only  according  to  the  size,  but  also  according  to  the  na- 
ture of  the  substance.  In  consequence  of  this,  Faraday  divides  all  bodies 
into  two  classes.  He  calls  the  one  magnetic,  or,  better,  paramagnetic,  and 
the  other  diamagnetic. 

The  matter  of  which  a  paramagnetic  (magnetic)  body  consists  is  attracted 
by  both  poles  of  the  horse-shoe  magnet;  on  the  contrary,  the  matter  of  a 


MAGNETISM.  Ill 

diamagnetic  body  is  repelled.  When  a  small  iron  bar  is  hung  by  untwisted 
silk  between  the  poles  of  the  magnet,  so  that  its  long  diameter  can  easily 
move  in  a  horizontal  plane,  it  arranges  itself  axially,  that  is,  parallel  to  the 
straight  line  which  joins  the  poles,  or  to  the  magnetic  axis  of  the  poles; 
assuming  at  the  end  which  is  nearest  the  north  pole,  a  south  pole,  and  at 
the  end  nearest  the  south  pole,  a  north  pole.  Whenever  the  little  bar  is 
removed  from  this  position,  after  a  few  oscillations,  it  returns  again  to  its 
previous  position.  The  whole  class  of  paramagnetic  bodies  behave  in  a 
precisely  similar  way  under  similar  circumstances;  but  in  the  intensity  of 
the  effects  great  differences  occur. 

Diamagnetic  bodies,  on  the  contrary,  have  their  long  diameters  placed 
equatorially,  that  is,  at  right  angles  to  the  magnetic  axis.  They  behave, 
as  if  at  the  end  opposite  to  each  pole  of  the  magnet  the  same  kind  of  po- 
larity existed. 

In  the  first  class  of  substances,  besides  iron,  which  is  the  best  represen- 
tative of  the  class,  we  have  nickel,  cobalt,  manganese,  chromium,  cerium, 
titanium,  palladium,  platinum,  osmium,  aluminium,  oxygen,  and  also  most 
of  the  compounds  of  these  bodies;  most  of  them,  even  when  in  solution. 
According  to  Faraday,  the  following  substances  are  also  feebly  paramag- 
netic (magnetic)  :  paper,  sealing-wax,  Indian-ink,  porcelain,  asbestos, 
fluor-spar,  minium,  cinnabar,  binoxide  of  lead,  sulphate  of  zinc,  tourma- 
line, graphite,  and  charcoal. 

In  the  second  class  are  placed  bismuth,  antimony,  zinc,  tin,  cadmium, 
sodium,  mercury,  lead,  silver,  copper,  gold,  arsenic,  uranium,  rhodium, 
iridium,  tungsten,  phosphorus,  iodine,  sulphur,  chlorine,  hydrogen,  and 
many  of  their  compounds.  Also,  glass  free  from  iron,  water,  alcohol, 
ether,  nitric  acid,  hydrochloric  acid,  resin,  wax,  olive  oil,  oil  of  turpentine, 
caoutchouc,  sugar,  starch,  gum,  and  wood.  These  are  diamagnetic. 

If  diamagnetic  and  paramagnetic  bodies  are  combined,  their  peculiar 
properties  are  destroyed.  In  most  of  these  compounds,  occasionally,  in 
consequence  of  the  presence  of  the  smallest  quantity  of  iron,  the  peculiar 
magnetic  power  remains  more  or  less  in  excess.  Thus  green  bottle-glass 
and  many  varieties  of  crown  glass  are  magnetic  in  consequence  of  the  iron 
they  contain. 

In  order  to  examine  the  magnetic  properties  of  fluids,  they  are  placed  in 
very  thin  glass  tubes,  the  ends  of  which  are  then  closed  by  melting;  they 
are  then  hung  horizontally  between  the  poles  of  the  magnet.  Under  the 
influence  of  poles  sufficiently  powerful,  they  begin  to  swing,  and  according 
as  the  fluid  contents  are  paramagnetic  (magnetic)  or  diamagnetic,  they 
assume  an  axial  or  equatorial  position. 

Faraday  has  tried  the  magnetic  condition  of  gases  in  different  ways. 
One  method  consisted  in  making  soap-bubbles  with  the  gas  which  he 
wished  to  investigate,  and  bringing  these  near  the  poles.  Soap  and  water 
alone  is  feebly  diamagnetic.  A  bubble  filled  with  oxygen  was  strongly 
attracted  by  the  magnet.  All  other  gases  in  the  air  are  diamagnetic,  that 
is,  they  are  repelled.  But,  as  Faraday  has  shown,  in  a  different  way,  this 
partly  arises  from  the  paramagnetic  (magnetic)  property  of  the  air.  Thus 
he  found  that  nitrogen,  when  this  differential  action  was  eliminated,  was 
perfectly  indifferent,  whether  it  was  condensed  or  rarefied,  whether  cooled 
or  heated.  When  the  temperature  is  raised,  the  diamagnetic  property  of 
gases  in  the  air  is  increased.  Hence  the  flame  of  a  candle  or  of  hydrogen 
is  strongly  repelled  by  the  magnet.  Even  warm  air  is  diamagnetic  in  cold 
air. 

For  some  time  it  had  been  believed  that  bodies  in  a  crystalline  form  had 
a  special  and  peculiar  beharior  when  placed  between  the  poles  of  a  mair- 
net.  It  appeared  as  though  the  magnetic  directing  power  of  the  crystal 
had  some  peculiar  relation  to  the  position  of  its  optic  axis ;  so  that,  inde- 


112  MAGNETISM. 

pendently  of  the  magnetic  property  of  the  substance  of  the  crystal,  if  the 
crystal  was  positively  optical,  it  possessed  the  power  of  placing  its  optic 
axis  parallel  with  the  line  which  joined  the  poles  of  the  magnet,  while 
optically  negative  crystals  tried  to  arrange  their  axis  at  right  angles  to 
this  line.  This  supposition  is  disproved  by  the  excellent  investigation  of 
Tyndall  and  Knoblauch,  who  showed  that  exceptions  to  the  above  law  arc 
furnished  by  all  classes  of  crystals,  and  proved  that  the  action,  instead  of 
being  independent  of  the  magnetic  nature  of  the  mass,  was  completely  re- 
versed where,  in  isomorphous  crystals,  a  magnetic  constituent  was  substi- 
tuted for  a  diamagnetic  one.  Rejecting  the  various  new  forces  assumed, 
Tyndall  and  Knoblauch  referred  the  observed  phenomena  to  the  modifi- 
cation of  the  magnetic  force  by  structure,  and  they  imitated  the  effects 
exactly,  by  means  of  substances  whose  structure  had  been  modified  by 
compression.  In  a  Inter  investigation,  Tyndall  demonstrated  the  funda- 
mental principle  on  which  these  phenomena  depend,  showing  that  the  entire 
mass  of  a  magnetic  body  is  most  strongly  attracted  when  the  attracting 
force  acts  parallel  to  the  line  of  compression  ;  and  that  a  diamagnetic  sub- 
stance is  most  strongly  repelled  when  the  repulsion  acts  along  the  same 
line.  Hence  when  such  a  body  is  freely  suspended  in  the  magnetic  field, 
the  line  of  compression  must  set  axial  or  equatorial,  according  as  the  mass 
is  magnetic  or  diamagnetic.  Faraday  was  the  first  to  establish  a  differen- 
tial action  of  this  kind  in  the  case  of  bismuth  ;  Tyndall  extended  it  to 
several  magnetic  and  diamagnetic  crystals,  and  showed  that  it  was  not 
confined  to  them,  but  was  a  general  property  of  matter.  It  was  also 
proved  that  for  a  fixed  distance  the  attraction  of  a  magnetic  sphere,  and 
the  repulsion  of  a  diamagnetic  sphere,  followed  precisely  the  same  law, 
both  being  exactly  proportioned  to  the  square  of  the  exciting  current. 

The  phenomena  of  diamagnetism  naturally  suggest  the  inquiry,  whether 
the  repulsion  exerted  by  a  magnetic  pole  on  diamagnetic  bodies  is  a  force 
distinct  from  that  of  magnetism  as  exerted  upon  iron  and  other  bodies  of 
the  magnetic  class ;  or  whether,  on  the  other  hand,  the  magnetic  and  dia- 
magnetic conditions  of  matter  are  merely  relative,  so  that  all  bodies  are 
magnetic  in  different  degrees,  and  the  apparent  repulsion  of  a  diamagnetic 
body,  such  as  bismuth,  is  merely  the  result  of  its  being  attracted  by  the 
magnet  less  than  the  particles  of  the  surrounding  medium,  just  as  a  balloon 
recedes  from  the  earth  because  its  weight  is  less  than  that  of  an  equal  bulk 
of  the  surrounding  air.  It  is  easy  to  show  that  the  same  body  may  appear 
magnetic  or  diamagnetic,  according  to  the  medium  in  which  it  is  placed. 
Ferrous  sulphate  is  a  magnetic  substance,  and  water  is  diamagnetic:  hence 
it  is  possible,  by  varying  the  strength  of  an  aqueous  solution  of  this  salt, 
to  make  it  either  magnetic,  indifferent,  or  diamagnetic  when  suspended  in 
air.  Again,  a  tube  containing  a  solution  of  ferrous  protosulphate  suspended 
horizontally  within  ajar  also  filled  with  a  solution  of  the  same  salt,  and 
placed  between  the  poles  of  two  powerful  electro-magnets,  will  place  itself 
axially  or  equatorially,  according  as  the  solution  contained  in  it  is  stronger 
or  weaker  than  that  in  the  jar.  In  the  same  manner,  then,  we  may  conceive 
that  bismuth  places  itself  equatorially  between  two  magnetic  poles,  because 
it  is  less  magnetic  than  the  surrounding  air.  But  the  diamagnetism  of 
bismuth  and  other  bodies  of  the  same  class  shows  itself  in  a  vacuum  as 
well  as  in  air :  hence,  if  diamagnetism  is  not  to  be  regarded  as  a  distinct 
force,  we  must  suppose  that  the  ether  is  also  magnetic,  and  occupies  in  the 
magnetic  scale  the  place  intermediate  between  magnetic  and  diamagnetic 
bodies. 

That  a  body  suspended  in  a  medium  of  greater  magnetic  susceptibility 
than  itself  will  recede  from  a  magnetic  pole  in  its  neighborhood,  in  con- 
sequence of  the  greater  force  with  which  the  particles  of  the  medium  are 
impelled  towards  the  magnet,  is  so  obvious  a  consequence  of  mechanical 


MAGNETISM.  113 

laws  that  we  can  scarcely  avoid  attributing  the  movements  of  diamagnetic 
bodies  to  the  cause  just  mentioned ;  at  least,  when  the  body  is  suspended  in 
air  or  other  magnetic  gas.  There  is,  however,  some  difficulty  in  reconciling 
the  above  described  phenomena  of  compressed  and  crystallized  bodies 
with  this  view;  and,  moreover,  Tyndall  has  shown,  by  a  method  which 
we  cannot  here  describe,*. that  diamagnetic  bodies  possess  opposite  poles, 
analogous  to  those  of  magn'etic  bodies,  each  of  these  poles  being  attracted 
by  one  pole  of  a  magnet  and  repelled  by  the  other.  This  polarity  shows 
decidedly  that  the  properties  of  diamagnetic  bodies  cannot  be  wholly  due 
to  the  differential  action  above  mentioned ;  for  if  they  were,  every  part  of 
a  diamagnetic  body  would  be  repelled  by  either  pole  of  a  magnet.  Dia- 
magnetism  must  therefore,  for  the  present  at  least,  be  regarded  as  a  force 
distinct  from  magnetism. 

*  Phil.  Trans.,  1855  and  1856.  Seo  also  Watts'a  Dictionary  of  Chemistry,  vol.  iii.  p.  776. 

10* 


114:  ELECTRICITY. 


ELECTRICITY. 

IF  glass,  amber,  or  sealing-wax  be  rubbed  with  a  dry  cloth,  it  acquires 
the  power  of  attracting  light  bodies,  as  feathers,  dust,  or  bits  of  paper: 
this  is  the  result  of  a  new  and  peculiar  condition  of  the  body  rubbed, 
called  electrical  excitation. 

If  a  light  downy  feather  be  suspended  by  a  thread  of  white  silk,  and  a 
dry  glass  tube,  excited  by  rubbing,  be  presented  to  it,  the  feather  will  be 
strongly  attracted  to  the  tube,  adhere  to  its  surface  for  a  few  seconds,  and 
then  fall  oft'.  If  the  tube  be  now  excited  anew,  and  presented  to  the  feather, 
the  latter  will  be  strongly  repelled. 

The  same  experiment  may  be  repeated  with  shellac  or  resin;  the  feather 
in  its  ordinary  state  will  be  drawn  towards  the  excited  body,  and,  after 
touching,  again  driven  from  it  with  a  certain  degree  of  force. 

Now,  let  the  feather  be  brought  into  contact  with  the  excited  glass,  so 
as  to  be  repelled  by  that  substance,  and  let  a  piece  of  excited  sealing-wax 
be  presented  to  it:  a  degree  of  attraction  will  be  observed  far  exceeding 
that  exhibited  when  the  feather  is  in  its  ordinary  state.  Or,  again,  let  the 
feather  be  made  repulsive  for  sealing-wax,  and  then  the  excited  glass  bo 
presented:  strong  attraction  will  ensue. 

The  reader  will  at  once  see  the  perfect  parallelism  between  the  effects 
described  and  some  of  the  phenomena  of  magnetism,  the  electrical  excite- 
ment having  a  twofold  nature,  like  the  opposite  polarities  of  the  magnet. 
A  body  to  which  one  kind  of  excitement  has  been  communicated  is  at- 
tracted by  another  body  in  the  opposite  state,  and  repelled  by  one  in  the 
same  state;  the  excited  glass  and  resin  being  to  each  other  as  the  north 
and  south  poles  of  a  pair  of  magnetized  bars. 

To  distinguish  these  two  different  forms  of  excitement,  terms  are  em- 
ployed which,  although  originating  in  some  measure  in  theoretical  views 
of  the  nature  of  the  electrical  disturbance,  may  be  understood  by  the 
student  as  purely  arbitrary  and  distinctive:  it  is  customary  to  call  the 
electricity  manifested  by  glass  rubbed  with  silk  positive  or  vitreous,  and  that 
developed  in  the  case  of  shellac,  and  bodies  of  the  same  class  rubbed  with 
flannel,  negative  or  resinous.  The  kind  of  electricity  depends  in  some  measure 
upon  the  nature  of  the  surface  and  the  quality  of  the  rubber;  smooth  and 
perfectly  clean  glass,  rubbed  with  silk,  becomes  positive,  but  when  ground 
or  roughened  by  sand  or  emery,  it  acquires,  under  the  same  circumstances, 
a  negative  charge.  Glass  dried  over  a  gas  flame  and  rubbed  with  wool  is 
generally  also  negative ;  when  dried  over  a  fire  of  wood-charcoal  it  remains 
positive. 

The  repulsion  shown  by  bodies  in  the  same  electrical  state  is  taken  ad- 
vantage of  to  construct  instruments  for  indicating  electrical  excitement  and 
pointing  out  its  kind.  Two  balls  of  elder  pith,  hung  by  threads  or  very 
fine  metal  wires,  serve  this  purpose  in  many  cases:  they  open  out  when 
excited,  in  virtue  of  their  mutual  repulsion,  and  show  by  the  degree  of 
divergence  the  extent  to  which  the  excitement  has  been  carried.  A  pair 
of  gold  leaves  suspended  to  a  metal  rod  having  a  brass  plate  on  its  upper 
end  constitute  a  much  more  delicate  arrangement,  and  one  of  great  value 
in  all  electrical  investigations.  The  rod  should  be  covered  with  a  thick 


ELECTRICITY. 


115 


coating  of  shellac,  and  it  must  be  fastened  by  means  of  a  cork,  air-tight, 
into  a  glass  flask.  The  flask  must  have  been  perfectly  dried  previously  by 
warming  it.  These  instruments  are  called  electroscopes  or  electrometers: 

Fig.  75.  Fig.  76. 


when  excited  by  the  communication  of  a  known  kind  of  electricity,  they 
show  by  an  increased  or  diminished  divergence,  the  state  of  an  electrified 
body  brought  into  their  neighborhood. 

One  kind  of  electricity  can  no  more  be  developed  without  the  other  than 
one  kind  of  magnetism:  the  rubber  and  the  body  rubbed  always  assume 
opposite  states,  and  the  positive  condition  on  the  surface  of  a  mass  of  matter 
is  invariably  accompanied  by  a  negative  state  in  all  surrounding  bodies. 

Fig.  77. 


The  induction  of  magnetism  in  soft  iron  has  its  exact  counterpart  in 
electricity :  a  body  already  electrified  disturbs  or  polarizes  the  particles 
of  all  surrounding  substances  in  the  same  manner  and  according  to  the 
same  law,  inducing  a  state  opposite  to  its  own  in  the  nearer  portions, 
and  a  similar  state  in  the  more  remote  parts.  A  series  of  globes  sus- 
pended by  silk  threads,  in  the  manner  represented  in  fig.  77,  will  each 
become  electric  by  induction  when  a  charged  body  is  brought  near  the  end 
of  the  series,  like  so  many  pieces  of  iron  in  the  vicinity  of  a  magnet,  the 
positive  half  of  each  globe  looking  in  one  and  the  same  direction,  and  the 
negative  half  in  the  opposite  one.  The  positive  and  negative  signs  are 
intended  to  represent  the  states. 

The  intensity  of  the  induced  electrical  disturbance  diminishes  with  the 
distance  from  the  charged  body;  if  this  be  removed  or  discharged,  all  the 
effects  cease  at  once. 

So  far,  the  greatest  resemblance  may  be  traced  between  these  two  sets 
of  phenomena;  but  here  it  seems  in  great  measure  to  cease.  The  magnetic 
polarity  of  a  piece  of  steel  can  awaken  polarity  in  a  second  piece  in  con- 
tact with  it  by  the  act  of  induction,  and  in  so  doing  loses  nothing  whatever 
of  its  power:  this  is  an  effect  completely  different  from  the  apparent 
transfer  or  discharge  of  electricity  constantly  witnessed,  which  in  the  air 
and  in  liquids  often  gives  rise  to  the  appearance  of  a  bright  spark  of  fire. 
Indeed,  ordinary  magnetic  effects  comprise  two  groups  of  phenomena  only, 


116 


ELECTRICITY. 


those,  namely,  of  attraction  and  repulsion,  and  those  of  induction.  But 
in  electricity,  in  addition  to  phenomena  very  closely  resembling  these,  we 
have  the  effects  of  discharge,  to  which  there  is  nothing  analogous  in  magnetism, 
and  which  takes  place  in  an  instant  when  any  electrified  body  is  put  in 
communication  with  the  earth  by  any  one  of  the  class  of  substances  called 
conductors  of  electricity,  all  signs  of  electrical  disturbance  then  ceasing. 

These  conductors  of  electricity,  which  thus  permit  discharge  to  take 
place  through  their  mass,  are  contrasted  with  another  class  of  substances 
called  non-conductors  or  insulators.  The  difference,  however,  is  only  one 
of  degree,  not  of  kind:  the  very  best  conductors  offer  a  certain  resistance 
to  the  electrical  discharge,  and  the  most  perfect  insulators  permit  it  to  a 
small  extent.  The  metals  are  by  far  the  best  conductors;  glass,  silk, 
shellac,  and  dry  gas  or  vapor  of  any  sort,  the  very  worst;  and  between 
these  there  are  bodies  of  all  degrees  of  conducting  power. 

Electrical  discharges  take  place  silently  and  without  disturbance  in  good 
conductors  of  sufficient  size.  But  if  the  charge  be  very  intense,  and  the 
conductor  very  small,  or  imperfect  from  its  nature,  it  is  often  destroyed 
with  violence. 

When  a  break  is  made  in  a  conductor  employed  in  effecting  the  discharge 
of  a  highly  excited  body,  disruptive  or  spark-discharge,  so  well  known, 
takes  place  across  the  intervening  air,  provided  the  ends  of  the  conductor 
be  not  too  distant.  The  electrical  spark  itself  presents  many  points  of 
interest  in  the  modifications  to  which  it  is  liable. 

The  time  of  transit  of  the  electrical  wave  through  a  chain  of  good  con- 
ducting bodies  of  great  length  is  so  minute  as  to  be  altogether  inappreci- 
able to  ordinary  means  of  observation.  Professor  Wheatstone's  very  in- 
genious experiments  on  the  subject  give,  in  the  instance  of  motion  through 
a  copper  wire,  a  velocity  surpassing  that  of  light. 

Fig.  78. 


Electrical  excitation  is  apparent  only  upon  the  surfaces  of  conductors, 
or  those  portions  directed  towards  other  objects  capable  of  assuming  the 
opposite  state.  An  insulated  ball  charged  with  positive  electricity,  and 
placed  in  the  centre  of  the  room,  is  maintained  in  that  state  by  the  induc- 
tive action  of  the  walls  of  the  apartment,  which  immediately  become  nega- 


ELECTRICITY. 


117 


lively  electrified :  in  the  interior  of  the  bull  there  is  absolutely  no  electricity 
to  be  found,  although  it  may  be  constructed  of  open  metal  gauze,  with 
meshes  half  an  inch  wide.  Even  on  the  surface  the  distribution  of  elec- 
trical force  is  not  always  the  same;  it  depends  upon  the  figure  of  the  body 
itself,  and  its  position  with  regard  to  surrounding  objects.  The  polarity 
is  always  highest  in  the  projecting  extremities  of  the  same  conducting  mass, 
and  greatest  of  all  when  these  are  attenuated  to  points;  in  which  case  the 
inequality  becomes  so  great  that  discharge  takes  place  to  the  air,  and  the  ex- 
cited condition  cannot  be  maintained. 

By  the  aid  of  these  principles,  the  construction  and  use  of  the  common 
electrical  machine,  and  other  pieces  of  apparatus  of  great  practical  utility, 
will  become  intelligible. 

A  glass  cylinder  (fig.  78)  is  mounted  with  its  axis  in  a  horizontal  position, 
and  provided  with  a  handle  or  winch  by  which  it  may  be  turned.  A  leather 
cushion  is  made  to  press  by  a  spring  against  one  side  of  the  cylinder, 
while  a  large  metal  conducting  body,  armed  with  a  number  of  points  next 
the  glass,  occupies  the  other:  both  cushion  and  conductor  are  insulated  by 
glass  supports,  and  to  the  upper  edge  of -the  former  a  piece  of  silk  is  at- 
tached, long  enough  to  reach  half  round  the  cylinder.  Upon  the  cushion  is 
spread  a  quantity  of  soft  amalgam  of  tin,  zinc,  and  mercury,*  mixed  up 
with  a  little  grease :  this  substance  is  found  by  experience  to  excite  glass 
most  powerfully.  The  cylinder,  as  it  turns,  thus  becomes  charged  by  fric- 
tions against  the  rubber,  and  as  quickly  discharged  by  the  row  of  points 
attached  to  the  great  conductor ;  and  as  the  latter  is  also  completely  insu- 
lated, its  surface  speedily  acquires  a  charge  of  positive  electricity,  which 
may  be  communicated  by  contact  to  other  insulated  bodies.  The  maximum 
effect  is  produced  when  the  rubber  is  connected  by  a  chain  or  wire  with  the 

Fig.  79. 


earth.     If  negative  electricity  be  wanted,  the  rubber  must  be  insulated  and 
the  conductor  discharged. 

*  1  part  tin,  1  zinc,  and  6  mercury.     An  amalgam  of  permanent  softness  and  great  efficacy  is 
>tained  by  mixing  65  parts  mercury,  24  tin,  and  11  zinc.     It  is  better  applied  to  silk  than  to 

iitltnr 


obtained  by 
leather. 


118  ELECTRICITY. 

Another  form  of  the  electrical  machine  .consists  of  a  circular  plate  of 
glass  (fig.  79)  moving  upon  an  axis,  and  provided  with  two  pairs  of  cush- 
ions or  rubbers,  attached  to  the  upper  and  lower  parts  of  the  wooden 
frame,  covered  with  amalgam,  between  which  the  plate  moves  with  con- 
siderable friction.  An  insulated  conductor,  armed  as  before  with  points, 
discharges  the  plate  as  it  turns,  the  rubber  being  at  the  same  time  con- 
nected with  the  ground  by  the  wood-work  of  the  machine,  or  by  a  strip  of 
metal.  This  modification  of  the  apparatus  is  preferred  in  all  cases  where 
considerable  power  is  wanted. 

In  the  practical  management  of  electrical  apparatus,  great  care  must  be 
taken  to  prevent  deposition  of  moisture  from  the  air  upon  the  surface  of 
the  glass  supports,  which  should  always  be  varnished  with  fine  lac  dissolved 
in  alcohol;  the  slightest  film  of  water  is  sufficient  to  destroy  the  power  of 
insulation.  The  rubbers  also  must  be  carefully  dried,  and,  like  the  plate, 
cleansed  from  adhering  dust  before  use,  and  the  amalgam  renewed  if  need- 
ful: in  damp  weather  much  trouble  is  often  experienced  in  bringing  the 
machine  into  powerful  action. 

When  the  conductor  of  the  machine  is  charged  with  electricity,  it  acts  in- 
directly on,  and  accumulates  the  contrary  electricity  to  its  own,  at  the  sur- 
face of  all  the  surrounding  conductors.  It  produces  the  greatest  effect  on 
the  conductor  that  is  nearest  to  it  and  is  in  the  best  connection  with  the 
ground,  whereby  the  electricity  of  the  same  kind  as  that  of  the  machine 
may  pass  to  the  earth.  As  the  inducing  electricity  attracts  the  induced 
electricity  of  an  opposite  kind,  so,  on  the  other  hand,  is  the  former  attracted 
by  the  latter.  Hence,  the  electricity  which  the  conductor  receives  from 
the  machine  must  especially  accumulate  at  that  spot  to  which  another  good 
conductor  of  electricity  is  opposed.  If  a  metal  disc  is  in  connection  with 
the  conductor  of  a  machine,  and  if  another  similar  disc,  which  is  in  good 
connection  with  the  earth,  is  placed  opposite  to  it,  we  have  an  arrange- 
ment by  which  tolerably  large  and  good  conducting  surfaces  can  be  brought 
close  to  one  another:  thus  the  positive  condition  of  the  first  disc,  as  well 
as  the  negative  condition  of  the  other,  must  be  increased  to  a  very  con- 
siderable degree:  the  limit  is  in  this  case,  however,  soon  reached,  because 
the  intervening  air  easily  permits  spark-discharge  to  take  place  through 
its  substance.  With  a  solid  insulating  body,  as  glass  or  lac,  this  happens 
with  much  greater  difficulty,  even  when  the  plate  of  insulating  matter  is 
very  thin.  It  is  on  this  principle  that  instruments  for  the  accumulation  of 
electricity  depend,  among  which  the  Leyden  jar  is  the  most  important. 

A  thin  glass  jar  is  coated  on  both  sides  with  tinfoil,  care 
being  taken  to  leave  several  inches  of  the  upper  part  un- 
covered (fig.  80) ;  a  wire,  terminating  in  a  metallic  knob, 
communicates  with  the  internal  coating.  When  the  out- 
side of  the  jar  is  connected  with  the  earth,  and  the  knob 
put  in  contact  with  the  conductor  of  the  machine,  the 
inner  and  outer  surfaces  of  the  glass  become  respectively 
positive  and  negative,  until  a  very  great  degree  of  in- 
jrgiii"  '~~^JJL  tensity  has  been  attained.  On  completing  the  connec- 

'll1    ifi™  t*on  Between  the  two  coatings  by  a  metallic  wire  or  rod, 

dischai'ge  occurs  in  the  form  of  an  exceedingly  bright 
spark,  accompanied  by  a  loud  snap ;   and  if  the  human 
body  be  interposed  in  the  circuit,  the  peculiar  and  dis- 
agreeable sensation  of  the  electric  shock  is  felt  at  the 
moment  of  its  completion. 
By  enlarging  the  dimensions  of  the  jar,  or  by  connecting  together  a  num- 
ber of  such  jars  in  such  a  manner  that  all  may  be  charged  and  discharged 
simultaneously,   the  power  of  the  apparatus  may  be  greatly  augmented. 
Thin  wires  of  metal  may  be  fused  and  dissipated ;  pieces  of  wood  may  be 


ELECTRICITY.  119 

shattered ;  many  combustible  substances  set  on  fire ;  and  all  the  well-known 
effects  of  lightning  exhibited  upon  a  small  scale. 

The  electric  spark  is  often  very  conveniently  employed  in  chemical 
inquiries  for  firing  gaseous  mixtures  in  closed  vessels.  A  small  Leyden  jar 
charged  by  the  machine  is  the  most  effective  contrivance  for  this  purpose; 
but,  not  unfrequently,  a  method  may  be  resorted  to  which  involves  less 
preparation.  The  most  convenient  means  of  generating  electricity  is  that 
proposed  by  Blinsen.  A  large  porcelain  tube,  which  is  dry  and  warm,  is 
wrapped  round  and  rubbed  briskly  by  a  dry  silken  cloth.  After  each  rub 
the  tube  is  brought  in  the  immediate  neighborhood  of  the  knob  of  a  small 
Leyden  jar,  the  outer  coating  of  this  vessel  being  in  connection  with  the 
earth.  The  electrophorus  is  also  frequently  used  for  this  purpose.  This 
instrument  consists  of  a  round  tray  or 

disli  of  tinned  plate,  having  a  stout  wire  Fig.  81. 

round  its  upper  edge ;  the  width  may  be 
about  twelve  inches,  and  the  depth  half 
sin  inch.  This  tray  is  filled  with  melted 
shellac,  and  the  surface  rendered  as  even 
as  possible.  A  brass  disc,  with  rounded 
edge,  of  about  nine  inches  diameter,  is 
also  provided,  and  fitted  with  an  insulat- 
ing handle.  When  a  spark  is  wanted,  the 
resinous  plate  is  excited  by  striking  it 
with  a  dry,  warm  piece  of  fur,  or  a  silk 
handkerchief;  the  cover  is  placed  upon  it,  and  touched  by  the  finger,  to- 
gether with  the  rim  of  the  plate.  When  the  cover  is  raised,  it  is  found  so 
strongly  charged  by  induction  with  positive  electricity,  as  to  give  a  bright 
spark;  and,  as  the  resin  is  not  discharged  by  the  cover,  which  merely 
touches  it  at  a  few  points,  sparks  may  be  drawn  as  often  as  may  be  wished. 

It  is  not  known  to  what  cause  the  disturbance  of  the  electrical  equili- 
brium of  the  atmosphere  is  due:  experiment  has  shown  that  the  higher 
regions  of  the  air  are  usually  in  a  positive  state,  the  intensity  of  which 
reaches  a  maximum  at  a  particular  period  of  the  day.  In  cloudy  and 
stormy  weather  the  distribution  of  the  atmospheric  electricity  becomes 
much  deranged,  clouds  near  the  surface  of  the  earth  often  appearing  in  a 
negative  state. 

The  circumstances  of  a  thunder-storm  exactly  resemble  those  of  the 
charge  and  discharge  of  a  coated  plate  or  jar;  the  cloud  and  the  earth 
represent  the  two  coatings,  and  the  intervening  air  the  bad  conducting 
body  or  dielectric.  The  polarities  of  the  opposed  surface  and  of  the  in- 
sulating medium  between  them  become  raised  by  mutual  induction,  until 
violent  disruptive  discharge  takes  place  through  the  air  itself,  or  through 
any  other  bodies  which  may  happen  to  be  in  the  interval.  When  these 
are  capable  of  conducting  freely,  the  discharge  is  silent  and  harmless;  but 
in  other  cases  it  often  proves  highly  destructive.  These  dangerous  effects 
are  now  in  a  great  measure  obviated  by  the  use  of  lightning-rods  attached 
to  buildings,  the  erection  of  which,  however,  demands  a  number  of  pre- 
cautions not  always  understood  or  attended  to.  The  masts  of  ships  may 
be  guarded  in  like  manner  by  metal  conductors :  Sir  W.  Snow  Harris  has 
devised  a  most  ingenious  plan  for  the  purpose,  which  is  now  adopted,  with 
the  most  complete  success,  in  the  Koyal  Navy. 

ELECTRIC  CURRENT;   ELECTRIC  BATTERY. 

When  two  solid  conducting  bodies  are  plunged  into  a  liquid  which  acts 
upon  them  unequally,  the  electric  equilibrium  is  also  disturbed,  the  one 
acquiring  the  positive  condition,  and  the  other  the  negative.  Thus,  pieces 


120 


ELECTRICITY. 


of  zinc  and  platinum  put  into  dilute  sulphuric  acid,  constitute  an  arrange- 
ment capable  of  generating  electrical  force:  the  zinc  being  the  metal  at- 
tacked, becomes  negative  ;  and  the  platinum  remaining  unaltered,  assumes, 
the  positive  condition ;  and  on  making  a  metallic  communication  in  any 
way  between  the  two  plates,  discharge  ensues,  as  when  the  two  surfaces 
of  a  coated  and  charged  jar  are  put  into  connection. 

No  sooner,  however,  has  this  occurred,  than  the  disturbance  is  repeated; 
and  as  these  successive  charges  and  discharges  take  place  through  the  fluid 
and  metals  with  inconceivable  rapidity,  the  result  is  an  apparently  con- 
tinuous action,  to  which  the  term  electrical  current  is  given. 

It  is  necessary  to  guard  against  the  idea,  which  the  term  naturally  sug- 
gests, of  an  actual  bodily  transfer  of  something  through  the  substance  of 
the  conductors,  like  water  through  a  pipe:  the  real  nature  of  all  these 
phenomena  is  entirely  unknown,  and  may  perhaps  remain  so;  the  expres- 
sion is  convenient  notwithstanding,  and  consecrated  by  long  use;  and  with 
this  caution,  the  very  dangerous  error  of  applying  figurative  language  to 
describe  an  effect,  and  then  seeking  the  nature  of  the  effect  from  the 
common  meaning  of  words,  may  be  avoided. 

The  intensity  of  the  electrical  excitement  developed  by  a  single  pair 
of  metals  and  a  liquid  is  too  feeble  to  affect  the  most  delicate  gold-leaf 
electroscope;  but,  by  arranging  a  number  of  such  alternations  in  a  con- 
nected series,  in  such  a  manner  that  the  direction  of  the  current  shall  be 
the  same  in  each,  the  intensity  may  be  very  greatly  exalted.  The  two  in- 
struments invented  by  Volta,  called  the  pile  and  crown  of  cups,  depend 
upon  this  principle. 

Upon  a  plate  of  zinc  is  laid  a  piece  of  cloth,  rather  smaller  than  itself, 
steeped  in  dilute  acid,  or  any  liquid  capable  of  exerting  chemical  action 
upon  the  zinc  ;  upon  this  is  placed  a  plate  of  copper, 
silver,  or  platinum;  then  a  second  piece  of  zinc,  another 
cloth,  and  a  plate  of  inactive  metal,  until  a  pile  of  about 
twenty  alternations  has  been  built  up.  If  the  two  termi- 
nal plates  be  now  touched  with  wet  hands,  the  sensation 
of  the  electrical  shock  will  be  experienced  ;  but,  unlike 
the  momentary  effect  produced  by  the  discharge  of  ajar, 
the  sensation  can  be  repeated  at  will  by  repeating  the 
contact,  and  with  a  pile  of  one  hundred  such  pairs,  excited 
by  dilute  acid,  it  will  be  nearly  insupportable.  When 
such  a  pile  is  insulated,  the  two  extremities  exhibit  strong 
positive  and  negative  states;  and  when  connection  is 
made  between  them  by  wires  armed  with  points  of  hard 
charcoal  or  plumbago,  the  discharge  takes  place  in  the 
form  of  a  bright  enduring  spark  or  stream  of  fire. 
The  second  form  of  apparatus,  or  crown  of  cups,  is  precisely  the  same 
in  principle,  although  different  in  appearance.  A  number  of  cups  or 


ELECTRICITY.  121 

glasses  are  arranged  in  a  row  or  circle,  each  containing  a  piece  of  active 
arid  a  piece  of  inactive  metal,  and  a  portion  of  exciting  liquid  —  zinc,  cop- 
per, and  dilute  sulphuric  acid,  for  example.  The  copper  of  the  first  cup 
is  connected  with  the  zinc  of  the  second,  the  copper  of  the  second  with 
the  zinc  of  the  third,  and  so  to  the  end  of  the  series.  On  establishing  a 
communication  between  the  first  and  last  plates  by  means  of  a  wire,  or 
otherwise,  discharge  takes  place  as  before. 

When  any  such  electrical  arrangement  consists  merely  of  a  single  pair 
of  conductors  and  an  interposed  liquid,  it  is  called  a  simple  circuit;  when 
two  or  more  alterations  are  concerned,  the  term  "compound  circuit"  is 
applied:  they  are  called  also,  indifferently,  voltaic  batteries.  In  every 
form  of  such  apparatus,  however  complex  it  may  appear,  the  direction  of 
the  current  may  be  easily  understood  and  remembered.  The  polarity  or 
disturbance  may  be  considered  to  commence  at  the  surface  of  the  metal 
attacked,  and  to  be  propagated  through  the  liquid  to  the  inactive  conductor, 
and  thence  back  again  by  the  connecting  wire,  these  extremities  of  the 
battery  being  always  respectively  negative  and  positive  when  the  appara- 
tus is  insulated.  In  common  language,  it  is  said  that  the  current  in  every 
battery  in  an  active  state  starts  from  the  metal  attacked,  passes  through 
the  liquid  to  the  second  metal  or  conducting  body,  and  returns  by  the  wire 
or  other  channel  of  communication:  hence,  in  the  pile  and  crown  of  cups 
just  described,  the  current  in  the  battery  is  always  from  the  zinc  to  the 
copper ;  and  out  of  the  battery,  from  the  copper  to  the  zinc,  as  shown  by 
the  arrows. 

In  the  modification  of  Volta's  original  pile,  made  by  Mr.  Cruikshank, 
the  zinc  and  copper  plates  are  soldered  together  and  cemented  water-tight 
into  a  mahogany  trough,  which  thus  becomes  divided  into  a  series  of  cells 
or  compartments  capable  of  receiving  the  exciting  liquid.  This  apparatus 
is  well  fitted  to  exhibit  effects  of  tension,  to  act  upon  the  electroscope,  and 
give  shocks:  hence  its  advantageous  employment  in  the  application  of 
electricity  to  medicine,  as  a  very  few  minutes  suffice  to  prepare  it  for  use. 

Fig.  84. 


The  crown  of  cups  was  also  put  into  a  much  more  manageable  form  by  Dr. 
Babingtori,  and  still  further  improved,  as  will  hereafter  be  seen,  by  Dr. 
Wollaston.  Subsequently,  various  alterations  have  been  made  by  different 
experimenters  with  a  view  of  obviating  certain  defects  in  the  common 
batteries,  of  which  a  description  will  be  found  towards  the  middle  of  the 
volume. 

The  term  "  galvanism,"  sometimes  applied  to  this  branch  of  electrical 
science,  is  used  in  honor  of  Professor  Galvani,  of  Bologna,  who,  in  1790, 
made  the  very  curious  observation  that  convulsions  could  be  produced  in 
the  limbs  of  a  dead  frog  when  certain  metals  were  made  to  touch  the  nerve 
and  muscle  at  the  same  moment.  It  was  Volta,  however,  who  pointed  out 
the  electrical  origin  of  these  motions;  and  although  the  explanation  he 
offered  of  the  source  of  the  electrical  disturbance  is  no  longer  generally 
adopted,  his  name  is  very  properly  associated  with  the  invaluable  instru- 
ment his  genius  gave  to  science. 

In  the  year  1822,  Professor  Seebeck,  of  Berlin,  discovered  another  source 
of  electricity,  to  which  allusion  has  already  been  made  —  namely,  in- 
equality of  temperature  and  conducting  power  in  different  metals  placed 
11 


122  ELECTKO-MAGNETISM. 

in  contact,  or  in  the  same  metal  in  different  states  of  compression  and 
density.  Even  with  a  great  number  of  alternations,  the  current  produced 
is  exceedingly  feeble  compared  with  that  generated  by  the  voltaic  pile. 

Some  animals  of  the  class  of  fishes,  as  the  torpedo  or  electric  ray,  and  the 
electric  eel  of  South  America,  are  furnished  with  a  special  organ  or  appa- 
ratus for  developing  electrical  force,  which  is  employed  in  defence,  or  in 
the  pursuit  of  prey.  Electricity  is  here  seen  to  be  closely  connected  with 
nervous  power:  the  shock  is  given  at  the  will  of  the  animal,  and  great  ex- 
haustion follows  repeated  exertion  of  the  power. 

ELECTRO-MAGNETISM;  INDUCTION. 

Although  the  fact  that  electricity  is  capable,  under  certain  circum- 
stances, both  of  inducing  and  of  destroying  magnetism,  has  long  been  known 
from  the  effects  of  lightning  on  the  compass-needle  and  upon  small  steel 
articles,  as  knives  and  forks,  to  which  polarity  has  suddenly  been  given 
by  the  stroke,  it  was  not  till  1819  that  the  laws  of  these  phenomena  were 
discovered  by  Oersted,  of  Copenhagen,  and  shortly  afterwards  fully  devel- 
oped by  Ampere. 

The  action  which  a  current  of  electricity,  proceeding  from  any  so.urce, 
exerts  upon  a  magnetized  needle,  is  quite  peculiar.  The  poles  or  centres 
of  magnetic  force  are  neither  attracted  nor  repelled  by  the  wire  carrying 
the  current,  but  made  to  move  around  the  latter  by  a  force  which  may  be 
termed  tangential,  and  is  exerted  in  a  direction  perpendicular  at  once  to 
that  of  the  current,  and  to  the  line  joining  the  pole  and  the  wire.  Both 
poles  of  the  magnet  being  thus  acted  upon  at  the  same  time,  and  in  con- 
trary directions,  the  needle  is  forced  to  arrange  itself  across  the  current, 
so  that  its  axis,  or  the  line  joining  the  poles,  may  be  perpendicular  to  the 
wire;  and  this  is  always  the  position  which  the  needle  will  assume  when 
the  influence  of  terrestrial  magnetism  is  in  anyway  removed.  This  curious 
angular  motion  may  even  be  shown  by  suspending  a  magnet  in  such  a 
way  that  only  one  of  its  poles  shall  be  subjected  to  the  current;  a  perma- 
nent movement  of  rotation  will  continue  as  long  as  the  current  is  kept  up, 
its  direction  being  changed  by  altering  the  pole,  or  reversing  the  current. 
The  movable  connections  are  made  by  mercury,  into  which  the  points  of 
the  conducting  wires  dip. 

It  is  often  of  great  practical  consequence  to  be  able  to  predict  the  di- 
rection in  which  a  particular  pole  shall  move  by  a  given  current,  because 
in  all  galvanoscopes  and  other  instruments  involving  these  principles,  the 
movement  of  the  needle  is  taken  as  an  indication  of  the  direction  of  the  cir- 
culating current.  And  this  is  easily  done  by  a  simple  mechanical  aid  to 
the  memory:  Let  the  current  be  supposed  to  pass  through  a  watch  from 

the  face  to  the  back;  the  motion  of  the 

Fig.  85.  north  pole  will  be  in  the  direction  of  the 

hands.  Or  a  little  piece  of  apparatus 
may  be  used  if  reference  is  often  required : 
this  is  a  piece  of  pasteboard,  or  other 
suitable  material,  cut  into  the  form  of  an 
arrow  for  indicating  the  current,  crossed 
by  a  magnet  having  its  poles  marked,  and 
arranged  in  the  true  position  with  respect 
to  the  current.  The  direction  of  the  lat- 
ter in  the  wire  of  the  galvanoscope  can  at  once  be  known  by  placing  the 
representative  magnet  in  the  direction  assumed  by  the  needle  itself. 

The  common  galvanoscope  (fig.  86),  consisting  of  a  coil  of  wire  having 
a  compass-needle  suspended  on  a  point  within  it,  is  greatly  improved  by  the 
addition  of  a  second  needle,  as  already  in  part  described  (p.  102),  and  by 


ELECTRO-MAGNETISM. 


123 


a  better  mode  of  suspension,  a  long  fibre  of  silk  being  used  for  the  purpose. 
The  two  needles  are  of  equal  size,  and  magnetized  as  nearly  as  possible 
to  the  same  extent;  they  are  then  immovably  fixed  together  parallel,  and 

Fig.  86. 


with  their  poles  opposed,  and  hung  with  the  lower  needle  in  the  coil  and 
the  upper  one  above  it.  The  advantage  gained  is  twofold:  the  system  is 
astatic,  unaffected,  or  nearly  so,  by  the  magnetism  of  the  earth ;  and  the 
needles,  being  both  acted  upon  in  the  same  manner  by  the  current,  are 
urged  with  much  greater  force  than  one  alone  would  be,  all  the  actions  of 
every  part  of  the  coil  being  strictly  concurrent.  A  divided  circle  is  placed 
below  the  upper  needle,  by  which  the  angular  motion  can  be  measured; 
and  the  whole  is  enclosed  in  glass,  to  shield  the  needles  from  the  agitation 
of  the  air.  The  whole  is  shown  in  fig.  86. 

The  action  between  the  pole  and  the  wire  is  mutual,  as  may  be  shown 
by  rendering  the  wire  itself  movable,  and  placing  a  magnet  in  its  vicinity: 
on  completing  the  circuit,  the  wire  will  be  put  in  motion,  and,  if  the 
arrangement  permits,  it  will  rotate  around  the  magnetic  pole. 

A  little  consideration  will  show  that,  from  the  peculiar  nature  of  the 
electro-dynamic  force,  a  wire  carrying  a  current,  bent  into  a  spiral  or  helix, 
must  possess  the  properties  of  an  ordinary  mag- 
netized bar,  its  extremities  being  attracted  and 
repelled  by  the  poles  of  a  magnet.  Such  is  really 
found  to  be  the  case,  as  may  be  proved  by  a  va- 
riety of  arrangements,  among  which  it  will  bo 
sufficient  to  cite  the  beautiful  little  apparatus  of 
Professor  de  la  Rive.  A  short  wide  glass  tube  is 
fixed  into  a  cork  ring  of  considerable  size  (fig.  87) ; 
a  little  voltaic  battery,  consisting  of  a  single  pair 
of  copper  and  zinc  plates,  is  fitted  to  the  tube, 
and  to  these  the  ends  of  the  spiral  are  soldered. 
On  filling  the  tube  with  dilute  acid,  and  floating 
the  whole  in  a  large  basin  of  water,  the  helix  will 
be  observed  to  arrange  itself  in  the  magnetic  meridian,  and  on  trial  it  will 
be  found  to  obey  a  magnet  held  near  it  in  the  most  perfect  manner,  as  long 
as  the  current  circulates. 

When  an  electric  current  is  passed  at  right  angles  to  a  piece  of  iron  or 
steel,  the  latter  acquires  magnetic  polarity,  either  temporary  or  permanent, 
as  the  case  may  be,  the  direction  of  the  current  determining  the  position 


Fig.  87. 


124  ELECTRO-MAGNETISM. 

of  the  poles.  This  effect  is  prodigiously  increased  by  causing  the  current 
to  circulate  a  number  of  times  round  the  bar,  which  then  acquires  extra- 
ordinary magnetic  power.  A  piece  of  soft  iron,  worked 
into  the  form  of  a  horse-shoe  (fig.  88),  and  surrounded 
by  a  coil  of  copper  wire  covered  with  silk  or  cotton  for 
the  purpose  of  insulation,  furnishes  an  excellent  illus- 
tration of  the  inductive  energy  of  the  current  in  this  re- 
spect: when  the  ends  of  the  wire  are  put  into  commu- 
nication with  a  small  voltaic  battery  of  a  single  pair  of 
plates,  the  iron  instantly  becomes  so  highly  magnetic  as 
to  be  capable  of  sustaining  a  very  heavy  weight. 

Ampere  discovered,  in  the  course  of  his  investigations, 
a  number  of  extremely  interesting  phenomena  resulting 
from  the  action  of  electrical  currents  on  each  other, 
which  become  evident  when  arrangements  are  made  for 
giving  mobility  to  the  conducting  wires.  He  found  that 
when  two  currents,  flowing  in  the  same  direction,  are 
made  to  approach  each  other,  strong  attraction  takes 
place  between  them,  and,  when  in  opposite  directions, 
an  equally  strong  repulsion.  These  effects,  which  are 
not  difficult  to  demonstrate,  have  absolutely  no  relation, 
that  can  be  traced,  to  ordinary  electrical  attractions  and 
repulsions,  from  which  they  must  be  carefully  distinguished;  they  rfre 
purely  dynamic,  having  to  do  with  electricity  in  motion.  Ampere  founded 
upon  this  discovery  a  most  beautiful  and  ingenious  hypothesis  of  magnetic 
actions  in  general,  which  explains  very  clearly  the  influence  of  the  current 
upon  the  needle. 

A  current  of  electricity  can  thus  develop  magnetism  in  a  transverse 
direction  to  its  own  ;  in  the  same  manner,  magnetism  can  call  into  activity 
electric  currents.  If  the  two  extremities  of  the  coil  of  the  electro-magnet 
above  described  be  connected  with  a  galvanoscope,  and  the  iron  magnetized 
by  the  application  of  a  permanent  steel  horse-shoe  magnet  to  the  ends  of 
the  bar,  a  momentary  current  will  be  developed  in  the  wire,  and  pointed 
out  by  the  movement  of  the  needle.  It  lasts  but  a  single  instant,  the  needle 
returning  after  a  few  oscillations  to  a  state  of  rest.  On  removing  the  mag- 
net, whereby  the  polarity  of  the  iron  is  at  once  destroyed,  a  second  current 
or  wave  will  become  apparent,  but  in  the  opposite  direction  to  that  of  the 
first.  By  employing  a  very  powerful  steel  magnet,  surrounding  its  iron 
keeper  or  armature  with  a  very  long  coil  of  wire,  and  then  making  the 
armature  itself  rotate  in  front  of  the  faces  of  the  magnet,  so  that  its  induced 
polarity  shall  be  rapidly  reversed,  magneto-electric  currents  may  be  pro- 
duced, of  such  intensity  as  to  give  bright  sparks  and  most  powerful  shocks, 
and  exhibit  all  the  phenomena  of  voltaic  electricity.  Fig.  89  represents  a 
very  powerful  arrangement  of  this  kind. 

When  two  covered  wires  are  twisted  together  or  laid  side  by  side  for  some 
distance,  and  a  current  transmitted  through  the  one,  a  momentary  electrical 
wave  will  be  induced  in  the  other  in  the  reverse  direction ;  and  on  breaking 
connection  with  the  battery,  a  second  single  wave  will  become  evident  by 
the  aid  of  the  galvanoscope,  in  the  same  direction  as  that  of  the  primary 
current.  In  the  same  way,  when  a  current  of  electricity  passes  through 
one  turn  in  a  coil  of  wire,  it  induces  two  secondary  currents  in  all  the 
other  turns  of  the  coil;  when  the  circuit  is  closed,  the  first  is  mov- 
ing in  the  opposite  direction  to  the  primary  current;  the  second,  when 
the  circuit  is  broken,  has  a  motion  in  the  same  direction  as  the  primary 
current.  The  effect  of  the  latter  is  added  to  that  of  the  primary  current. 
Hence,  if  a  wire  coil  be  made  part  of  the  conducting  wire  of  a  weak  electric 
pile,  and  if  the  primary  current,  by  means  of  an  appropriate  arrangement, 


ELECTRO-MAGNETISM.  125 

be  made  and  broken  in  rapid  succession,  we  can  increase  in  a  remarkable 
manner  the  effects  which  are  produced  at  the  moment  of  breaking  the  cir- 

Fig.  89. 


cuit  either  at  the  place  of  interruption,  such  as  the  spark-discharges,  or  in 
secondary  closing  conductors,  as  in  the  action  on  the  nerves  or  the  decom- 
position of  water. 

If  two  copper  wires,  the  one  above  the  other,  be  twisted  round  the  same 
hollow  cylinder,  and  one  of  these  wires  —  for  instance,  the  inner  one  —  be 
made  part  of  a  galvanic  circuit,  a  current  of  short  duration  is  induced  in 
the  outer  wire,  both  by  making  and  by  breaking  contact.  The  strength  of 
this  current  can  be  very  appreciably  increased  by  filling  the  hollow  cylinder 
with  a  bundle  of  thin  iron  rods,  when  magnetic  and  electrical  induction  are 
made  to  co-operate.  The  more  frequently  contact  is  alternately  made  and 
broken,  the  greater  is  the  number  of  induced  currents  that  follow  each 
o.ther,  and  the  more  powerful,  within  certain  limits,  is  the  action.  Dr. 
Neef  has  constructed  an  ingenious  contrivance,  in  which  contact  is  made 
and  broken  by  the  current  itself,  whereby  his  induction  apparatus  actually 
becomes  an  electrical  machine.  Fig.  90  exhibits  the  original  apparatus 
slightly  modified.  The  arrangement  consists  essentially  of  an  elastic  copper 
strip  a  a',  which  is  fixed  at  a',  and  carries  at  b  a  small  plate  of  soft  iron." 
The  latter  hangs  over  the  iron  rods  of  the  induction  coil,  which  are  some- 
what raised  in  this  particular  point,  but  without  touching  them.  The  end, 
a,  of  the  copper  strip  is  covered  with  a  little  plate  of  platinum,  which 
presses  against  a  platinum  point  of  the  screw  c.  The  current,  having  trav- 
ersed the  inner  coil,  passes  from  the  point  c,  to  the  plate  a,  in  order  to 
return  through  the  copper  strip  a  a',  and  the  wire  sf.  By  the  passage  of 
the  current  the  iron  rods  have  become  magnetic  and  attract  the  iron  plate, 
6,  whereby  the  end,  #,  of  the  copper  strip  is  removed  from  the  platinum 
point,  and  contact  is  broken.  But  as  soon  as  the  current  ceases,  the  iron 
rods  lose  their  magnetism,  the  elastic  copper  strip  returns  to  its  former 
position,  and  establishes  again  the  current  for  a  short  time.  The  screws,  c 
and  d,  regulate  the  position  of  the  spring  and  the  time  of  its  oscillations, 
the  velocity  of  which  may  be  estimated  by  the  pitch  of  the  notes  produced. 
This  apparatus,  which  was  first  made  by  Dr.  Neef,  in  1830,  has  been  con- 


126  ELECTRICITY    OF    VAPOK. 

siderably  improved  within  the  last  few  years.  Ruhmkorff  especially,  by  a 
more  perfect  isolation  of  the  wire  coils,  has  succeeded  to  a  much  greater 
extent  in  preserving  the  electrical  induction.  He  has  thus  obtained  a  state 

Fig.  90. 


of  electrical  tension  which  resembles  that  produced  by  frictional  electricity ; 
the  spark  is  capable  of  crossing  the  air  in  measurable  distances,  not  in 
isolated  discharges,  but  in  streams  of  brilliant  light.  The  shocks  of  this 
apparatus  resemble  those  of  a  moderate  Leyden  jar,  but  diifer  from  the 
latter  by  the  rapidity  with  which  they  may  be  repeated  at  pleasure.  By 
means  of  Ruhmkorff 's  coil,  Grove  has  lately  effected  decompositions  in 
water  and  other  bad  conducting  liquids,  which  resemble  those  obtained 
many  years  ago  by  Wollaston  by  means  of  the  electrical  machine.  Those 
phenomena  of  decomposition,  which  in  water,  for  instance,  furnish  oxygen 
and  hydrogen  at  the  same  pole,  must  be  distinguished  from  true  electrical 
decompositions ;  they  are,  in  fact,  effects  of  heat,  as  Grove  has  pointed  out. 

ELECTRICITY  OF  VAPOR. 

The  electricity  exhibited  under  certain  peculiar  circumstances  "by  a  jet 
of  steam,  first  observed  by  mere  accident,  but  since  closely  investigated  by 
Sir  W.  Armstrong,  and  also  by  Faraday,  is  now  referred  to  the  friction, 
not  of  the  pure  steam  itself,  but  of  particles  of  condensed  water,  against 
the  interior  of  the  exit-tube.  It  has  been  proved  with  certainty  in  the  last 
few  years  that  evaporation  alone  is  not  capable  of  disturbing  the  electrical 
equilibrium,  and  the  hope  first  entertained,  that  these  phenomena  would 
throw  light  upon  the  cause  of  electrical  excitement  in  the  atmosphere,  is 
now  abandoned.  The  steam  is  usually  positive,  if  the  jet-pipe  be  constructed 
of  wood  or  clean  metal,  but  the  introduction  of  the  smallest  trace  of  oily 
matter  causes  a  change  of  sign.  The  intensity  of  the  charge  is,  cseleris 
paribus,  increased  with  the  elastic  force  of  the  steam.  By  this  means 
effects  have  been  obtained  very  far  surpassing  those  of  the  most  powerful 
plate  electrical  machines  ever  constructed. 

Although  no  electricity  can  be  directly  evolved  by  evaporation,  yet  va- 
por possesses  in  a  high  degree  the  property  of  discharging  into  the  at- 
mosphere that  electricity  which  often  accumulates  in  bodies  from  which  it 
arises.  The  fresh  branches  and  leaves  of  trees  do  this  to  the  greatest  ex- 
tent. When  moistened  with  rain  or  dew,  their  surfaces  become  positively 
electrical,  whilst  the  internal  parts,  even  to  the  roots,  become  negatively 
electrical. 


PAKT  II. 

CHEMISTRY  OF  ELEMENTARY  BODIES. 


rpHE  term  element  or  elementary  substance  is  applied  in  chemistry  to  those 
X  forms  of  modifications  of  matter  which  have  hitherto  resisted  all  at- 
tempts to  decompose  them.  Nothing  is  ever  meant  to  be  affirmed  concern- 
ing their  real  nature;  they  are  simply  elements  to  us  at  the  present  time; 
hereafter,  by  new  methods  of  research,  or  by  new  combinations  of  those 
already  possessed  by  science,  many  of  the  substances  which  now  figure  as 
elements  may  possibly  be  shown  to  be  compounds;  this  has  already  hap- 
pened, and  may  again  take  place. 

The  elementary  bodies,  at  present  recognized,  amount  to  sixty-four  in 
number ;  of  these,  about  fifty  belong  to  the  class  of  metals.  Several  of 
these  are  of  recent  discovery,  and  as  yet  very  imperfectly  known.  The 
distinction  between  metals  and  non-metallic  substances,  or  metalloids,  al- 
though very  convenient  for  purposes  of  description,  is  entirely  arbitrary, 
since  the  two  classes  graduate  into  each  other  in  the  most  complete  manner. 

It  will  be  proper  to  commence  with  the  latter  and  less  numerous  division. 
The  elements  are  named  as  in  the  subjoined  table,  the  most  important  be- 
ing distinguished  by  the  largest  and  most  conspicuous  type,  those  next  in 
importance  by  medium  type,  whilst  the  names  of  elements  which  are  either 
of  rare  occurrence,  or  of  which  our  knowledge  is  very  imperfect,  are 
printed  in  the  smallest  type. 


METALLOIDS. 

BORON. 

BROMINE. 

CARBON. 

CHLORINE. 

FLUORINE. 

HYDROGEN. 

IODINE. 

NITROGEN. 

OXYGEN. 

PHOSPHORUS. 

Selenium. 

SILICIUM. 

SULPHUR. 

Tellurium. 


METALS. 


ALUMINIUM. 

ANTIMONY. 

ARSENIC. 

BARIUM. 

Beryllium. 

BISMUTH. 

Cadmium. 

Caesium. 

CALCIUM, 

Cerium. 

CHROMIUM. 

COBALT. 

COPPER. 

Didymium. 

Erbium. 

GOLD. 

Indium. 


Iridium. 

IRON. 

Lanthanum. 

LEAD. 

Lithium. 

MAGNESIUM. 

MANGANESE. 

MERCURY. 

Molybdenum. 

NICKEL. 

Niobium. 

Osmium. 

PALLADIUM. 

PLATINUM. 

POTASSIUM. 

Rhodium. 

Rubidium. 


Ruthenium. 

SILVER. 

SODIUM. 

STRONTIUM. 

Tantalum. 

Terbium. 

Thallium. 

Thorinum. 

TIN. 

TITANIUM. 

TlTNGSTK.V. 

URANIUM. 

Vanadium. 

Yttrium. 

ZINC. 

Zirconium. 

127 


128 


OXYGEN. 


OXYGEN. 

Whatever  plan  of  classification,  founded  on  the  natural  relations  of  the 
elements,  be  adopted,  it  will  always  be  found  most  advantageous,  in  the 
practical  study  of  chemistry,  to  commence  with  the  consideration  of  the 
great  constituents  of  the  ocean  and  the  atmosphere. 

Oxygen  was  discovered  in  the  year  1774,  by  Scheele,  in  Sweden,  and  Dr. 
Priestley,  in  England,  independently  of  each  other,  and  described  under  the 
terms  empyreal  air  and  dephlogislicated  air.  The  name  oxygen*  was  given 
to  it  by  Lavoisier  some  time  afterward.  Oxygen  exists  in  a  free  and  un- 
combined  state  in  the  atmosphere,  mingled  with  another  gaseous  body,  ni- 
trogen. No  very  good  direct  means  exist,  however,  for  separating  it  from 
the  latter;  and,  accordingly,  it  is  always  obtained  for  purposes  of  experi- 
ment by  decomposing  certain  of  its  compounds,  which  are  very  numerous. 

The  red  oxide  of  mercury,  or  red  precipitate  of  the  old  writers,  may  be 
employed  with  this  view.  In  this  substance  the  attraction  which  holds 
together  the  mercury  and  the  oxygen  is  so  feeble,  that  simple  exposure  to 
heat  suffices  to  bring  about  decomposition.  The  red  precipitate  is  placed 

Fig.  91, 


in  a  short  tube  of  hard  glass,  to  which  is  fitted  a  perforated  cork,  furnished 
with  a  piece  of  narrow  glass  tube,  bent  as  in  fig.  91.  The  heat  of  a  spirit- 
lamp  being  applied  to  the  substance,  decomposition  speedily  commences; 
globules  of  metallic  mercury  collect  in  the  cool  part  of  the  wide  tube, 
which  answers  the  purpose  of  a  retort,  while  gas  issues  in  considerable 
quantity  from  the  apparatus.  This  gas  is  collected  and  examined  by  the 
aid  of  the  pneumatic  trough,  which  consists  of  a  vessel  of  water  provided 
with  a  shelf,  upon  which  stand  the  jars  or  bottles  destined  to  receive  the 
gas,  filled  with  water  and  inverted.  By  keeping  the  level  of  the  liquid 
above  the  mouth  of  the  jar,  the  water  is  retained  in  the  latter  by  the  pres- 
sure of  the  atmosphere,  and  entrance  of  air  is  prevented.  When  the  jar  is 
brought  over  the  extremity  of  the  gas-delivering  tube,  the  bubbles  of  gas 
rising  through  the  water,  collect  in  the  upper  part  of  the  jar,  and  displace 
the  liquid.  As  soon  as  one  jar  is  filled,  it  may  be  removed,  still  keeping 
its  mouth  below  the  water-level,  and  another  substituted.  The  whole  ar- 
rangement is  shown  in  fig.  91. 

*  From  <5£uf,  acid,  and  yev,  a  root  signifying  production. 


OXYGEN.  129 

The  experiment  here  described  is  more  instructive  as  an  excellent,  case 
of  the  resolution  by  simple  means  of  a  compound  body  into  its  constituents,* 
than  valuable  as  a  source  of  oxygen  gas.  A  better  and  more  economical 
method  is  to  expose  to  heat  in  a  retort,  or  flask  furnished  with  a  bent  tube, 
a  portion  of  the  salt  called  potassium  chlorate.  A  common  Florence  flask 
serves  perfectly  well,  the  heat  of  a  spirit-lamp  being  sufficient.  The  salt 
melts  and  decomposes  with  ebullition,  yielding  a  very  large  quantity  of 
oxygen  gas,  which  may  be  collected  in  the  way  above  described.  The  first 
portion  of  the  gas  often  contains  a  little  chlorine.  The  white  saline  residue 
in  the  flask  is  potassium  chloride.  This  plan,  which  is  very  easy  of  execu- 
tion, is  always  adopted  when  very  pure  gas  is  required  for  analytical  pur- 
poses.f 

A  third  method,  very  good  when  perfect  purity  is  not  demanded,  is  to 
heat  to  redness,  in  an  iron  retort  or  gun-barrel,  the  black  manganese  oxide 
of  commerce,  which  under  these  circumstances  suffers  decomposition,  al- 
though not  to  the  extent  manifest  in  the  red  precipitate.  J 

If  a  little  of  the  black  manganese  oxide  be  finely  powdered  and  mixed 
with  potassium  chlorate,  and  the  mixture  heated  in  a  flask  or  retort  by  a 
lamp,  oxygen  will  be  disengaged  with  the  utmost  facility,  and  at  a  far  lower 
temperature  than  when  the  chlorate  alone  is  used.§  All  the  oxygen  comes 
from  the  chlorate,  the  manganese  remaining  quite  unaltered.  The  materials 
should  be  well  dried  in  a  capsule  before  their  introduction  into  the  flask. 
This  experiment  affords  an  instance  of  an  effect  by  no  means  rare,  in 
which  a  body  seems  to  act  by  its  mere  presence,  without  taking  any  obvi- 
ous part  in  the  change  brought  about. 

Methods  for  the  preparation  of  oxygen  on  a  large  scale  will  be  found 
described  under  the  heads  of  sulphuric  acid  and  barium  dioxide. 

Whatever  method  be  chosen  —  and  the  same  remark  applies  to  the  col- 
lection of  all  other  gases  by  similar  means  —  the  first  portions  of  gas  must 
be  suffered  to  escape,  or  be  received  apart,  as  they  are  contaminated  by 
the  atmospheric  air  of  the  apparatus.  The  practical  management  of  gases 
is  a  point  of  great  importance  to  the  chemical  student,  and  one  with  which 
he  must  endeavor  to  familiarize  himself.  The  water-trough  just  described 
is  one  of  the  most  indispensable  articles  of  the  laboratory,  and  by  its  aid 
all  experiments  on  gases  are  carried  on  when  the  gases  themselves  are  not 
sensibly  acted  upon  by  water.  The  trough  is  best  constructed  of  japanned 
copper,  the  form  and  dimensions  being  regulated  by  the  magnitude  of  the 
jars.  It  should  have  a  firm  shelf,  so  arranged  as  to  be  always  about  an 
inch  below  the  level  of  the  water,  and  in  the  shelf  a  groove  should  be  made 
about  half  an  inch  in  width,  and  tbe  same  in  depth,  to  admit  the  extremity 

*  Chemists  are  in  the  habit  of  representing  the  elements  by  symbols,  and  their  compounds  by 
formulas.  The  same  symbolical  language,  which  is  fully  explained  in  a  subsequent  section  of 
the  work  ((Jeneral  Principles  of  Chemical  Philosophy),  is  used  for  representing  the  changes 
which  the  chemical  compounds  undergo.  For  the  benefit  of  the  advanced  student,  the  formula} 
expressing  the  more-  important  decompositions  are  now  given  in,  foot-notes.  The  decomposition 
of  mercuric  oxide  is  thus  represented:  — 

HgO  = 


Mercuric  oxide. 
KC103 


Potassium  chlorate.  Potassium  chloride. 

."MnOo  =  Mn304 


Manganese  dioxide.  MangaxxMO-man-  Oxygen. 

ganic  oxide. 

§  [The  manganese  oxide  should  not  contain  any  combustible  matter,  or  an  explosion  will 
result.  Accidents  have  occurred  from  this  cause,  anil  a  preliminary  trial  should  lie  made  by  heat- 
ing a  small  quantity  in  a  metal  cup,  should  there  be  any  doubt  of  the  purity  of  the  oxide.— 
R.  U.J 


130 


OXYGEN. 


of  the  delivery-tube  beneath  the  jar,  which  stands  securely  upon  the  shelf. 
When  the  pneumatic  trough  is  required  of  tolerably  large  dimensions,  it 
may  with  great  advantage  have  the  form  and  disposition  represented  in 

Fig.  92. 


Fig.  93. 


fig.  92.  The  end  of  the  groove  spoken  of,  which  crosses  the  shelf  or  shal- 
low portion,  is  shown  at  a. 

Gases  are  transferred  from  jar  to  jar  with  the  utmost  facility,  by  first 
filling  the  vessel,  into  which  the  gas  is  to  be  passed  with  water,  inverting 
it,  carefully  retaining  its  mouth  below  the  water-level,  and  then  bringing 
beneath  it  the  aperture  of  the  jar  containing  the  gas.  On  gently  inclining 
the  latter,  the  gas  passes  by  a  kind  of  inverted  decantation  into  the  second 
vessel.  When  the  latter  is  narrow,  a  funnel  may  be  placed  loosely  in  its 
neck,  by  which  loss  of  gas  will  be  prevented. 

Ajar  wholly  or  partially  filled  with  gas  at 
the  pneumatic  trough  may  be  removed  by 
placing  beneath  it  a  shallow  basin,  or  even  a 
common  plate,  so  as  to  carry  away  enough 
water  to  cover  the  edge  of  the  jar :  and  many 
gases,  especially  oxygen,  may  be  so  preserved 
for  many  hours  without  material  injury. 

Gas-jars  are  often  capped  at  the  top,  and 
fitted  with  a  stop-cock  for  transferring  gas 
to  bladders  or  caoutchouc  bags.  When  such 
a  vessel  is  to  be  filled  with  water,  it  may  be 
slowly  sunk  in  an  upright  position  in  the 
well  of  the  pneumatic  trough,  the  stop-cock 
being  open  to  allow  the  air  to  escape,  until 
the  water  reaches  the  brass  cap.  The  cock 
is  then  to  be  turned,  and  the  jar  lifted  upon 
the  shelf,  and  filled  with  gas  in  the  usual  way. 
If  the  trough  be  not  deep  enough  for  this 

method  of  proceeding,  the  mouth  may  be  applied  to  the  stop-cock,  and  the 
vessel  filled  by  sucking  out  the  air  until  the  water  rises  to  the  cap.  In  all 
cases  it  is  proper  to  avoid  as  much  as  possible  wetting  the  stop-cocks  and 
other  brass  apparatus. 

Mr.  Pepys  contrived,  many  years  ago,  an  admirable  piece  of  apparatus 
for  storing  and  retaining  large  quantities  of  gas.  It  consists  of  a  drum  or 
reservoir  of  sheet  copper,  surmounted  by  a  shallow  trough  or  cistern,  the 
communication  between  the  two  being  made  by  a  couple  of  tubes,  a  i,  fur- 
nished with  stop-cocks,  one  of  which,  A/,  passes  nearly  to  the  bottom  of  the 
drum,  as  shown  in  fig.  94.  A  short  wide  open  tube,  c,  is  inserted  obliquely 
near  the  bottom  of  the  vessel,  into  which  a  plug  may  be  tightly  screwed. 


OXYGEN. 


131 


Fig.  94. 


A  stop-cock,  g,  near  the  top,  serves  to  transfer  gas  to  a  bladder  or  tube- 
apparatus.  A  glass  water-gauge,  d  e,  affixed  to  the  side  of  the  drum,  and 
communicated  with  both  top  and  bottom, 
indicates  the  level  of  the  liquid  within. 

To  use  the  gas-holder,  the  plug  is  first 
screwed  into  the  lower  opening,  and  the 
drum  completely  filled  with  water.  All 
three  stop-cocks  are  then  to  be  closed  and 
the  plug  removed.  The  pressure  of  the 
atmosphere  retains  the  water  in  the  gas- 
holder, and  if  no  air-leakage  occurs,  the 
escape  of  water  is  inconsiderable.  The 
extremity  of  the  delivery-tube  is  now  to 
be  well  pushed  through  the  open  aperture 
into  the  drum,  so  that  the  bubbles  of  gas 
may  rise  without  hindrance  to  the  upper 
part,  displacing  the  water,  which  flows 
out  in  the  same  proportion  into  a  vessel 
placed  for  its  reception.  When  the  drum 
is  filled,  or  enough  gas  has  been  collected, 
the  tube  is  withdrawn  and  the  plug  screwed 
into  its  place. 

When  a  portion  of  the  gas  is  to  be  transferred  to  a  jar,  the  latter  is  to  be 
filled  with  water  at  the  pneumatic  trough,  carried  by  the  help  of  a  basin 
or  plate  to  the  cistern  of  the  gas-holder,  and  placed  over  the  shorter  tube. 
On  opening  the  cock  of  the  neighboring  tube,  the  hydrostatic  pressure  of 
the  column  of  water  will  cause  compression  of  the  gas,  and  increase  its 
elastic  force,  so  that,  on  gently  turning  the  cock  beneath  the  jar,  it  will 
ascend  into  the  latter  in  a  rapid  stream  of  bubbles.  The  jar,  when  filled, 
may  again  have  the  plate  slipped  beneath  it,  and  be  removed  without  dif- 
ficulty. 

Oxygen,  when  free  or  uncombined,  is  known  only  in  the  gaseous  state, 
all  attempts  to  reduce  it  to  the  liquid  or  solid  condition  by  cold  and  pressure 
having  completely  failed.  When  pure,  it  is  colorless,  tasteless,  and  in- 
odorous. It  is  the  sustaining  principle  of  animal  life,  and  of  all  the 
ordinary  phenomena  of  combustion. 

Bodies  which  burn  in  the  air,  burn  with  greatly  increased  splendor  in 
oxygen  gas.  If  a  taper  be  blown  out,  and  then  introduced  while  the  wick 
remains  red-hot,  it  is  instantly  rekindled:  a  slip  of  wood  or  a  match  is 
relighted  in  the  same  manner.  This  effect  is  highly  characteristic  of  oxygen, 
there  being  but  one  other  gas  which  possesses  the  same  property;  and  this 
is  easily  distinguished  by  other  means.  The  experiment  with  the  match  is 
also  constantly  used  as  a  rude  test  of  the  purity  of  the  gas  when  it  is  about 
to  be  collected  from  the  retort,  or  when  it  has  stood  some  time  in  contact 
with  water  exposed  to  air. 

When  a  bit  of  charcoal  is  affixed  to  a  wire,  and  plunged  with  a  single  point 
red-hot  into  a  jar  of  oxygen,  it  burns  with  great  brilliancy,  throwing  off 
beautiful  scintillations,  until,  if  the  oxygen  be  in  excess,  it  is  completely 
consumed.  An  iron  wire,  or,  still  better,  a  steel  watch-spring,  armed  at 
its  extremity  with  a  bit  of  lighted  amadou,  and  introduced  into  a  vessel  of 
oxygen  gas,  exhibits  a  most  beautiful  phenomenon  of  combustion.  If  the 
experiment  be  made  in  a  jar  standing  on  a  plate,  the  fused  globules  of  black 
iron  oxide  fix  themselves  in  the  glaze  of  the  latter,  after  falling  through  a 
stratum  of  water  half  an  inch  in  depth.  Kindled  sulphur  burns  with  great 
beauty  in  oxygen;  and  phosphorus,  under  similar  circumstances,  exhibits 
a  splendor  which  the  eye  is  unable  to  support. 

In  these  an4  many  other  similar  cases  which  might  be  mentioned,  the 


132  OXYGEN. 

same  ultimate  effect  is  produced  as  in  atmospheric  air ;  the  action  is,  how- 
ever, more  energetic,  from  the  absence  of  the  gas  which,  in  the  air,  dilutes 
the  oxygen  and  enfeebles  its  chemical  powers.  The  process  of  respiration 
in  animals  is  an  effect  of  the  same  nature  as  common  combustion.  The 
blood  contains  substances  which  slowly  burn  by  the  aid  of  the  oxygen  thus 
introduced  into  the  system.  When  this  action  ceases,  life  becomes  extinct. 

Oxygen  is  bulk  for  bulk  a  little  heavier  than  atmospheric  air,  its  specific 
gravity  being  1-10503,  referred  to  that  of  air  as  unity,  and  16  referred  to 
that  of  hydrogen  as  unity.  A  litre  of  oxygen  at  the  standard  temperature 
and  pressure,  that  is  to  say,  at  0°  C.,  and  700  millimetres  barometric  pres- 
sure, weighs  1-43028  gram.  At  15-5°  C.  (60°  F.),  and  under  a  pressure  of 
30  inches,  100  cubic  inches  of  the  gas  weigh  34-29  grains.* 

It  has  been  already  remarked,  that  to  determine  with  the  utmost  degree 
of  accuracy  the  specific  gravity  of  a  gas,  is  an  operation  of  very  great 
practical  difficulty,  but  at  the  same  time  of  very  great  importance.  There 
are  several  methods  which  may  be  adopted  for  this  purpose :  the  one  de- 
scribed below  appears,  on  the  whole,  to  be  the  simplest  and  best.  It  re- 
quires, however,  the  most  scrupulous  care,  and  the  observance  of  a  number 
of  minute  precautions  which  are  absolutely  indispensable  to  success. 

The  plan  of  the  operation  is  as  follows:  A  large  glass  globe  is  to  be  filled 
with  the  gas  to  be  examined  in  a  perfectly  pure  and  dry  state,  having  a 
known  temperature,  and  an  elastic  force  equal  to  that  of  the  atmosphere  at 
the  time  of  the  experiment.  The  globe  so  filled  is  to  be  weighed.  It  is 
then  to  be  exhausted  at  the  air-pump  as  far  as  possible,  and  again  weighed. 
Lastly,  it  is  to  be  filled  with  dry  air,  the  temperature  and  pressure  of  which 
are  known,  and  its  weight  once  more  determined.  On  the  supposition 
that  the  temperature  and  elasticity  are  the  same  in  both  cases,  the  specific 
gravity  is  at  once  obtained  by  dividing  the  weight  of  the  gas  by  that  of 
the  air. 

The  globe  or  flask  must  be  made  very  thin,  and  fitted  with  a  brass  cap, 
surmounted  by  a  small  but  excellent  stop-cock.  A  delicate  thermometer 
should  be  placed  in  the  inside  of  the  globe,  secured  to  the  cap.  The  gas 
must  be  generated  at  the  moment,  and  conducted  at  once  into  the  previously 
exhausted  vessel,  through  a  long  tube  filled  with  fragments  of  pumice 
moistened  with  oil  of  vitriol,  or  some  other  extremely  hygroscopic  substance, 
by  which  it  is  freed  from  all  moisture.  As  the  gas  is  necessarily  generated 
under  some  pressure,  the  elasticity  of  that  contained  in  the  filled  globe 
will  slightly  exceed  the  pressure  of  the  atmosphere ;  and  this  is  an  ad- 
vantage, since,  by  opening  the  stop-cock  for  a  single  instant,  when  the 
globe  has  attained  an  equilibrium  of  temperature,  the  tension  becomes  ex- 
actly that  of  the  air,  so  that  all  barometrical  correction  is  avoided,  unless 
the  pressure  of  the  atmosphere  should  sensibly  vary  during  the  time  oc- 
cupied by  the  experiment.  It  is  hardly  necessary  to  remark  that  the 
greatest  care  must  also  be  taken  to  purify  and  dry  the  air  used  as 
the  standard  of  comparison,  and  to  bring  both  gas  and  air  as  nearly 
as  possible  to  the  same  temperature,  to  obviate  the  necessity  of  a  cor- 
rection, or  at  least  to  diminish  almost  to  nothing  the  errors  involved  by 
such  a  process. 

Oxides. — The  compounds  formed  by  the  direct  union  of  oxygen  with 
other  bodies  bear  the  general  name  of  oxides  :  these  are  very  numerous 
and  important.  They  are  conveniently  divided  into  three  principal  groups 
or  classes.  The  first  division  contains  all  those  oxides  which  resemble  in 
their  chemical  relations  the  oxides  of  potassium,  sodium,  silver,  or  lead : 
these  are  denominated  alkaline  or  basic  oxides.  The  oxides  of  the  second 
group  have  properties  opposed  to  those  of  the  bodies  mentioned ;  the  oxides 

*  Dumas,  Ann.  Chim.  Phys.  [3],  iii.  275. 


OXYGEN.  133 

of  sulphur  and  phosphorus  may  be  taken  as  the  typical  representatives  of 
the  class:  they  are  called  acid  oxides,  and  are  capable  of  uniting  with  the 
basic  oxides,  and  forming  compounds  called  salts.  Thus,  when  the  oxide 
of  sulphur,  called  sulphuric  oxide,  is  passed  in  the  state  of  vapor  over 
heated  barium  oxide,  combination  takes  place,  attended  with  vivid  incan- 
descence, and  a  salt  called  barium  sulphate  is  produced,  containing  all  the 
elements  of  the  two  original  bodies,  namely,  barium,  sulphur,  and  oxygen. 

There  is  also  an  intermediate  group  of  oxides  called  neutral  oxides,  from 
their  slight  disposition  to  enter  into  combination.  The  black  oxide  of 
manganese,  already  mentioned,  is  an  excellent  example.  It  must  not  be 
supposed,  however,  that  the  three  groups  of  oxides  just  mentioned  are 
separated  from  each  other  by  decided  lines  of  demarcation ;  on  the  con- 
trary, they  blend  into  one  another  by  imperceptible  degrees,  and  the  same 
oxide  may,  in  many  cases,  exhibit  either  acid  or  basic  relations  according 
to  the  circumstances  under  which  it  is  placed. 

Among  salts,  there  is  a  particular  group,  namely,  the  hydrogen  salts,  con- 
taining the  elements  of  an  acid  oxide,  and  water  (hydrogen  oxide),  which 
are  especially  distinguished  as  acids,  because  many  of  them  possess  in  an 
eminent  degree  the  properties  to  which  the  term  acid  is  generally  applied, 
such  as  a  sour  taste,  corrosive  action,  solubility  in  water,  and  the  power 
of  reddening  certain  blue  vegetable  colors.  A  characteristic  property  of 
these  acids,  or  hydrogen  salts,  is  their  power  of  exchanging  their  hydrogen 
for  a  metal  presented  to  them  in  the  free  state,  or  in  the  form  of  oxide. 
Thus,  sulphuric  acid,  which  contains  sulphur,  oxygen,  and  hydrogen, 
readily  dissolves  metallic  zinc,  the  metal  taking  the  pluce  of  the  hydrogen, 
which  is  evolved  as  gas,  and  forming  a  salt  containing  sulphur,  oxygen, 
and  zinc ;  in  fact,  a  zinc  sulphate,  produced  from  a  hydrogen  sulphate  by 
substitution  of  zinc  for  hydrogen.*  The  same  substitution  and  formation 
of  zinc  sulphate  take  place  when  zinc  oxide  is  brought  in  contact  with  sul- 
phuric acid;  but  in  this  case  the  hydrogen,  instead  of  being  evolved  as 
gas,  remains  combined  with  the  oxygen  derived  from  the  zinc  oxide,  form- 
ing water,  f 

A  series  of  oxides  containing  quantities  of  oxygen  in  the  proportion  of 
the  numbers  1,  2,  3,  united  with  a  constant  quantity  of  another  element, 
are  distinguished  as  monoxide,  dioxide,  and  trioxide  respectively,  the  Greek 
numerals  indicating  the  several  degrees  of  oxidation.  A  compound  inter- 
mediate between  a  monoxide  and  a  dioxide  is  called  a  sesquioxide,  e.  g.  : 

Chromium.      Oxygen. 

Chromium  monoxide       .         •         .         .         .         .     62-5     -f-     16 
Chromium  sesquioxide         .....          52-5     -f-     24 

Chromium  dioxide 52-5     -f-     32 

Chromium  trioxide 52-5     -f     48 

When  a  metal  forms  two  basic  or  salifiable  oxides,  they  are  distinguished 
by  adjectival  terms  ending  in  ous  for  the  lower,  and  ic  for  the  higher  de- 
gree of  oxidation,  e.  g. : 

Iron.        Oxygen. 

Iron  monoxide,  or  Ferrous  oxide       .         .         .         .     56     -j-     lt> 
Iron  sesquioxide,  or  Ferric  oxide  .         .         .          56     -f-     24 

The  salts  resulting  from  the  action  of  acids  on  these  oxides  are  also  dis- 
tinguished as  ferrous  and  ferric  salts  respectively. 

Acid  oxides  of  the  same  element,  sulphur  for  example,  are  also  dis- 
tinguished by  the  terminations  ous  and  ic,  applied  as  above ;  their  jicids, 

*  S04H2    +     Zn   =   S04Zn  +  H2  t  S04H2    +     Zn  0  =  S04Zn  +  OIL, 

12 


134  OXYGEN. 

or  hydrogen  salts,  receive  corresponding  names;  and  the  salts  formed 
from  these  acids  are  distinguished  by  names  ending  in  ite  and  ale  respec- 
tively. Thus,  for  the  oxides  and  salts  of  sulphur : 

Sulphur.        Oxygen. 

Sulphurous  oxide 82     4-     32 

Hydrogen. 

Hydrogen  sulphite,  or  Sulphurous  acid          .         32     4.     48    -f-         2 

Lead. 
Lead  sulphite 32     -f     48    -f     207 

Sulphuric  oxide 32     -f-     48 

Hydrogen. 
Hydrogen  sulphate,  or  Sulphuric  acid       .         .     32     -\-     64     -f-        2 

Lead. 

Lead  sulphate 32     -f     64    -f     207 

The  acids  above  spoken  of  are  oxygen-acids;  and  formerly  it  was  sup- 
posed that  all  acids  contained  oxygen  —  that  element  being,  indeed,  re- 
garded as  the  acidifying  principle;  hence  its  name  (p.  128).  At  present, 
however,  we  are  acquainted  with  many  bodies  which  possess  all  the  char- 
acters above  specified  as  belonging  to  an  acid,  and  yet  do  not  contain 
oxygen.  For  example,  hydrochloric  acid  (formerly  called  muriatic  acid, 
or  spirit  of  salt)  —  which  is  a  hydrogen  chloride,  or  compound  of  hydrogen 
and  chlorine  —  is  intensely  sour  and  corrosive;  reddens  litmus  strongly; 
dissolves  zinc,  which  drives  out  the  hydrogen  and  takes  its  place  in  com- 
bination with  the  chlorine,  forming  zinc-chloride ;  and  dissolves  most  me- 
tallic oxides,  exchanging  its  hydrogen  for  the  metal,  and  forming  a  metal- 
lic chloride  and  water.* 

Bromine,  iodine,  and  fluorine  also  form,  with  hydrogen,  acid  compounds 
analogous  in  every  respect  to  hydrochloric  acid. 

Compounds  of  chlorine,  bromine,  iodine,  fluorine,  sulphur,  selenium, 
phosphorus,  &c.,  with  hydrogen  and  metals,  are  grouped,  like  the  oxygen 
compounds,  by  names  ending  in  ide:  thus  we  speak  of  zinc  chloride,  cal- 
cium fluoride,  hydrogen  sulphide,  copper  phosphide,  &c.  The  numerical 
prefixes,  mono,  di,  iri,  &c.,  as  also  the  terminations  ous  and  ic,  are  applied 
to  these  compounds  in  the  same  manner  as  to  the  oxides,  thus : 


Hydrogen  bromide 

Potassium  monosulphide     . 
Potassium  disulphide 
Potassium  trisulphide 
Potassium  tetrasulphide 
Potassium  pentasulphide    . 

Hydrogen. 
1 
Potassium. 

78-2 
.     78-2 
78-2 
.     78-2 
78-2 

Iron. 
56 

Bromine. 
4-           80 
Sulphur, 
-f         32 
-f         64 
4-         96 
-f       128 
-}-       160 
Chlorine. 
4-         71 

.     56 

4-       105-5 

Stannous  sulphide 

Tin. 
118 
118 

Sulphur. 
4-         64 
4-       128 

The  Latin  prefixes  uni,bi,ter,  quadro,  &c.,  are  often  used  instead  of  the 
corresponding  Greek  prefixes ;  there  is  no  very  exact  rule  respecting  their 

*  Action  of  hydrochloric  acid  on  zinc : 

2HC1     +     Zn     —     ZnCl2     +     H2 
Action  of  hydrochloric  acid  on  zinc  oxide : 
2HC1     +    ZnO  =  ZnClg  +  OHa 


OXYGEN.  135 

use :  but,  generally  speaking,  it  is  best  to  employ  a  Greek  or  Latin  prefix, 
according  as  the  word  before  which  it  is  placed  is  of  Greek  or  Latin  origin  ; 
thus,  c&'oxide  corresponds  to  bisulphide  ;  on  the  whole,  however,  the  Greek 
prefixes  are  most  generally  employed. 

OZONE.  —  It  has  long  been  known  that  dry  oxygen,  or  atmospheric  air, 
when  exposed  to  the  action  of  a  series  of  electric  sparks,  emits  a  peculiar 
and  somewhat  metallic  odor.  The  same  odor  may  be  imparted  to  moist 
oxygen  by  allowing  phosphorus  to  remain  for  some  time  in  it,  and  by 
several  other  processes.  A  more  accurate  examination  of  this  odorous  air 
has  shown  that,  in  addition  to  the  smell,  it  possesses  several  properties 
not  exhibited  by  oxygen  in  its  ordinary  state.  One  of  its  most  char- 
acteristic effects  is  the  liberation  of  iodine  from  potassium  iodide.  This 
odorous  principle  has  been  the  subject  of  many  researches,  in  particular 
by  Schonbein,  of  Basle,  who  proposed  for  it  the  name  of  ozone.* 

An  easy  method  of  exhibiting  the  production  of  ozone  is  to  transmit  a 
current  of  oxygen  through  a  tube  into  which  a  pair  of  platinum  wires  is 
sealed,  with  the  points  at  a  little  distance  apart;  on  connecting  one  of  the 
wires  with  the  prime  conductor  of  an  electrical  machine  in  good  action, 
and  the  other  with  the  ground,  the  characteristic  odor  of  ozone  is  im- 
mediately developed  in  the  issuing  gas ;  but,  notwithstanding  the  powerful 
odor  thus  produced,  only  a  small  portion  of  the  oxygen  undergoes  this 
change.  Andrews  and  Tait  have  shown  that,  to  obtain  the  maximum  of 
ozone,  it  is  necessary  to  transmit  the  discharge  silently,  between  very  fine 
points;  if  sparks  are  allowed  to  pass,  a  considerable  portion  of  the  ozone 
is  reconverted  into  ordinary  oxygen  as  fast  as  it  is  formed.  Siemens  pre- 
pares ozone  by  induction:  he  forms  a  sort  of  Leyden  jar,  by  coating  the 
interior  of  a  long  tube  with  tin-foil,  and  passes  over  this  tube  a  second 
wider  tube  coated  with  tin-foil  on  its  outer  surface.  Between  the  two  tubes 
a  current  of  pure  dry  oxygen  is  passed,  which  becomes  electrified  by  in- 
duction, on  connecting  the  inner  and  outer  coating  with  the  terminal  wires 
of  an  induction-coil;  by  this  means  it  is  said  that  from  10  to  15  per  cent, 
of  the  oxygen  may  be  converted  into  ozone. 

Ozone  may  also  be  obtained  in  several  ways,  without  the  aid  of  elec- 
tricity; thus  it  is  formed  in  small  quantity  when  a  stick  of  phosphorus  is 
suspended  in  a  bottle  filled  with  moist  air;  by  the  slow  oxidation  of  ether, 
oil  of  turpentine,  and  other  essential  oils  ;  in  the  electrolytic  decomposition 
of  water;  and  by  the  action  of  strong  sulphuric  acid  on  potassium  per- 
m'anganate.^  There  has  been  considerable  discussion  about  the  nature  and 
composition  of  ozone;  but  the  most  trustworthy  experiments  seem  to  show 
that,  in  whatever  way  produced,  it  is  merely  a  modified  form  of  oxygen. 

Ozone  is  insoluble  in  water  and  in  solutions  of  acids  or  alkalies,  but  is 
absorbed  by  a  solution  of  potassium  iodide.  Air  charged  with  it  exerts  an 
irritating  action  on  the  lungs.  Ozone  is  decomposed  by  heat,  gradually  at 
100°  C.  (212°  F.,)  instantly  at  290°  C.  (554°  F.)  It  is  an  extremely  power- 
ful oxidizing  agent;  possesses  strong  bleaching  and  disinfecting  powers; 
corrodes  cork,  caoutchouc,  and  other  organic  substances ;  and  rapidly 
oxidizes  iron,  copper,  and  even  silver  when  moist,  as  well  as  dry  mercury 
and  iodine.  It  is  remarkable  that  the  absorption  of  ozone  by  these  and 
other  agents  is  not  attended  with  any  contraction  of  volume.  The  expla- 
nation of  this  fact  appears  to  be,  that  oxygen  when  ozonized  diminishes  in 
volume  (in  the  proportion  of  3  to  2,  according  to  Soret),  and  that  when 
the  ozone  is  decomposed  by  a  metal  or  other  substance,  one  portion  of  it 
enters  into  combination,  while  the  remainder,  which  is  set  free  as  ordinary 
oxygen,  occupies  the  same  bulk  as  the  ozone  itself. 

*  From  8$civ,  to  emit  an  odor. 

[f  Also,  according  to  A.  Houseau.by  the  action  of  sulphuric  acid  on  barium  dioxide.  — R.  B.] 


136 


HYDROGEN. 


The  most  delicate  test  for  the  presence  of  ozone  in  any  gas  is  afforded  by 
a  strip  of  paper  moistened  with  a  mixture  of  starch  and  solution  of  po- 
tassium iodide.  On  exposing  such  paper  to  the  action  of  ozone,  the  po- 
tassium iodide  is  decomposed,  its  potassium  combining  with  oxygen,  while 
the  iodine  is  liberated,  and  forms  a  deep  blue  compound  with  the  starch. 
Now,  when  paper  thus  prepared  is  exposed  to  the  open  air  for  five  or  ten 
minutes,  it  often  acquires  a  blue  tint,  the  intensity  of  which  varies  on  dif- 
ferent days.  Hence  it  has  been  plausibly  supposed  that  ozone  is  present 
in  the  air  in  variable  quantity.  But  iodine  may  be  liberated  from  po- 
tassium iodide  by  many  other  agents,  especially  by  certain  oxides  of  ni- 
trogen, which  are  very  likely  to  be  present  in  the  air  in  minute  quantities: 
hence  the  existence  of  ozone  in  the  air  cannot  be  proved  to  be  present  by 
this  reaction  alone. 


HYDROGEN. 

Hydrogen  may  be  obtained  for  experimental  purposes  by  deoxidizing 
•water,  of  which  it  forms  a  characteristic  component.* 

If  a  tube  of  iron  or  porcelain,  containing  a  quantity  of  filings  or  turnings 
of  iron,  be  fixed  across  a  furnace,  and  its  middle  portion  be  made  red-hot, 
and  then  the  vapor  of  water  transmitted  over  the  heated  metal,  a  large 
quantity  of  permanent  gas  will  be  disengaged  from  the  tube,  and  the  iron 
will  become  converted  into  oxide,  and  acquire  an  increase  in  weight.  The 
gas  is  hydrogen:  it  may  be  collected  over  water  and  examined. 

Hydrogen  is,  however,  more  easily  obtained  by  decomposing  hydrochloric 
or  dilute  sulphuric  acid  with  zinc,  the  metal  then  displacing  the  hydrogen 
in  the  manner  already  explained  (p.  133). 

The  simplest  method  of  preparing  the  gas  is  the  following :   A  wide-necked 

bottle  is  chosen,  and  fitted  with  a  sound 

Fig.  95,  cork,  perforated  by  two   holes   for  the 

reception  of  a  small  tube-funnel  reach- 
ing nearly  to  the  bottom  of  the  bottle, 
and  a  piece  of  bent  glass  tube  to  convey 
away  the  disengaged  gas.  Granulated 
zinc,  or  scraps  of  the  malleable  metal, 
are  put  into  the  bottle,  together  with  a 
little  water,  and  sulphuric  acid  slowly 
added  by  the  funnel,  the  point  of  which 
should  dip  into  the  liquid.  The  evolu- 
tion of  gas  is  easily  regulated  by  the 
supply  of  acid;  and  when  enough  has 
been  discharged  to  expel  the  air  of  the 
vessel,  it  may  be  collected  over  water 
in  a  jar,  or  passed  into  a  gas-holder. 
In  the  absence  of  zinc,  filings  of  iron  or 
small  nails  may  be  used,  but  with  less 
advantage. 

A  little  practice  will  soon  enable  the 
pupil  to  construct  and  arrange  a  variety  of  useful  forms  of.  apparatus,  in 
which  bottles,  and  other  articles  always  at  hand,  are  made  to  supersede 
more  costly  instruments.  Glass  tube,  purchased  by  weight  of  the  maker, 


Hence  the  name,  from  vdwp,  water,  and  ysv. 


HYDROGEN. 


137 


may  be  cut  by  scratching  with  a  file,  and  then  applying  a  little  force  with 
both  hands.  It  may  be  softened  and  bent,  when  of  small  dimensions,  by  the 
flame  of  a  spirit-lamp,  or  a  candle,  or,  better,  by  a  gas  jet.  Corks  may  be 
perforated  by  a  heated  wire,  and  the  hole  rendered  smooth  and  cylindrical 
by  a  round  file ;  or  the  ingenious  cork-borer  of  Dr.  Mohr,  now  to  be  had  of 
all  instrument-makers,  may  be  used  instead.  Lastly,  in  the  event  of  bad 
fitting,  or  unsoundness  in  the  cork  itself,  a  little  yellow  wax  melted  over  the 
surface,  or  even  a  little  grease  applied  with  the  finger,  renders  it  sound  and 
air-tight,  when  not  exposed  to  heat. 

Hydrogen  is  colorless,  tasteless,  and  inodorous  when  quite  pure.  To  ob- 
tain it  in  this  condition,  it  must  be  prepared  from  the  purest  zinc  that  can 
be  obtained,  and  passed  in  succession  through  solutions  of  potash  and  silver 
nitrate.  When  prepared  from  commercial  zinc,  it  has  a  slight  smell,  which 
is  due  to  impurity,  and  when  iron  has  been  used,  the  odor  is  very  strong 
and  disagreeable.  It  is  inflammable  and  burns,  when  kindled,  with  a  pale, 
yellowish  flame,  evolving  much  heat,  but  very  little  light.  The  result  of  the 
combustion  is  water.  It  is  even  less  soluble  in  water  than  oxygen,  and  has 
never  been  liquefied.  Although  destitute  of  poisonous  properties,  it  is  in- 
capable of  sustaining  life. 

Hydrogen  is  the  lightest  substance  known ;  Dumas  and  Bous-  Fig.QQ. 
singault  place  its  density  between  0-0691  and  0-0695,*  referred 
to  that  of  air  as  unity.  The  weight  of  a  litre  of  hydrogen  at 
0°  C.,  and  under  a  barometric  pressure  of  0-760  metre,  is 
0-08961  gram ;  consequently,  a  gram  of  hydrogen  occupies  a 
space  of  11-15947  litres. f  At  15-5°  C.  (60°  F.),  and  30  inches 
barometric  pressure,  100  cubic  inches  weigh  2-14  grains. 

When  a  gas  is  much  lighter  or  much  heavier  than  atmos- 
pheric air,  it  may  often  be  collected  and  examined  without  the 
aid  of  the  pneumatic  trough.  A  bottle  or  narrow  jar  may  be 
filled  with  hydrogen  without  much  admixture  of  air,  by  invert- 
ing it  over  the  extremity  of  an  upright  tube  delivering  the  gas. 
In  a  short  time,  if  the  supply  be  copious,  the  air  will  be  wholly 
displaced,  and  the  vessel  filled.  It  may  now  be  removed,  the 
vertical  position  being  carefully  retained,  and  closed  by  a  stop- 
per or  glass  plate.  If  the  mouth  of  the  jar  be  wide,  it  must 
be  partially  closed  by  a  piece  of  cardboard  during  -the  operation.  This 
method  of  collecting  gases  by  displacement  is  often  extremely  useful.  Hy- 
drogen was  formerly  used  for  filling  air-balloons,  being  made  for  the  pur- 
pose on  the  spot  from  zinc  or  iron  and  dilute  sulphuric  acid.  Its  use  is  now 
superseded  by  that  of  coal-gas,  which  may  be  made  very  light  by  employ- 
ing a  high  temperature  in  the  manufacture.  Although  far  inferior  to  pure 
hydrogen  in  buoyant  power,  it  is  found  in  practice  to  possess  advantages 
over  that  substance,  while  its  greater  density  is  easily  compensated  by  in- 
creasing the  magnitude  of  the  balloon. 

There  is  a  very  remarkable  property  possessed  by  gases  and  vapors  in 
general,  which  is  seen  in  a  high  degree  of  intensity  in  the  case  of  hydrogen ; 
this  is  what  is  called  diffusive  power.  If  two  bottles  containing  gases  which 
do  not  act  chemically  upon  each  other  at  common  temperatures  be  connected 
by  a  narrow  tube  and  left  for  some  time,  the  gases  will  be  found,  at  the  ex- 
piration of  a  certain  period,  depending  much  upon  the  narrowness  of  the 
tube  and  its  length,  uniformly  mixed,  even  though  they  differ  greatly  in 
density,  and  the  system  has  been  arranged  in  a  vertical  position,  with  the 
heavier  gas  downwards.  Oxygen  and  hydrogen  can  thus  be  made  to  mix, 
in  a  few  hours,  against  the  action  of  gravity,  through  a  tube  a  yard  in 

*  Ann.Chim.  Phys.,  3d  series,  viii.  201. 

•f-  A-;  ii  near  approximation,  it  nuiy  li«  remembered  that  a  litre  of  hydrogen  weighs  0-09  gram, 
or  '.)  <  fiiti-rains,  and  a  gram  of  hydrogen  occupies  11-1  litres. 


138  HYDKOGEN. 

length,  and  not  more  than  one  quarter  of  an  inch  in  diameter :  and  the  fact 
is  true  of  all  other  gases  which  are  destitute  of  direct  action  upon  each 
other. 

If  a  vessel  be  divided  into  two  portions  by  a  diaphragm  or  partition  of 
porous  earthenware  or  dry  plaster  of  Paris,  and  each  half  filled  with  a  dif- 
ferent gas,  diffusion  will  immediately  commence  through  the  pores  of  the 
dividing  substance,  and  will  continue  until  perfect  mixture  has  taken  place. 
All  gases,  however,  do  not  permeate  the  same  porous  body,  or,  in  other 
words,  do  not  pass  through  narrow  orifices  with  the  same  degree  of  facility. 
Professor  Graham,  to  whom  we  are  indebted  for  a  very  valuable  investiga- 
tion of  this  interesting  subject,  has  established  the  existence  of  a  very 
simple  relation  between  the  rapidity  of  diffusion  and  the  density  of  the  gas, 
which  is  expressed  by  saying  that  the  diffusive  power  varies  inversely  as 
the  square  root  of  the  density  of  the  gas  itself.  Thus,  in  the  experiment 
supposed,  if  one  half  of  the  vessel  be  filled  with  hydrogen  and  the  other 
half  with  oxygen,  the  two  gases  will  penetrate  the  diaphragm  at  very  dif- 
ferent rates ;  four  cubic  inches  of  hydrogen  will  pass  into  the  oxygen  side, 
while  one  cubic  inch  of  oxygen  travels  in  the  opposite  direction.  The  den- 
sities of  the  two  gases  are  to  each  other  in  the  proportion  of  1  to  16;  their 
relative  rates  of  diffusion  will  be  inversely  as  the  square  roots  of  these 
numbers,  i.  e.,  as  4  to  1. 

In  order,  however,  that  this  law  may  be  accurately  observed,  it  is  neces- 
sary that  the  porous  plate  be  very  thin ;  with  plates  of  stucco  an  inch  thick 
or  more,  which  really  consist  of  a  congeries  of  long  capillary  tubes,  a  dif- 
ferent law  of  diffusion  is  observed.*  An  excellent  material  for  diffusion 
experiments  is  the  artificially  compressed  graphite  of  Mr.  Brockedon,  of  the 
quality  used  for  making  writing- pencils.  It  may  be  reduced  by  cutting  and 
grinding  to  the  thickness  of  a  wafer,  but  still  retains  considerable  tenacity. 
The  pores  of  this  substance  appear  to  be  so  small  as  entirely  to  prevent  the 
transmission  of  gases  in  mass,  so  that,  to  use  the  language  of  Mr.  Graham, 
it  acts  like  a  molecular  sieve,  allowing  only  molecules  to  pass  through. 

The  simplest  and  most  striking  method  of  exhibiting  the 
Fig.  97.  phenomenon  of  diffusion  is  by  the  use  of  Graham's  diffu- 

sion-tube. This  is  merely  a  piece  of  wide  glass  tube  ten  or 
twelve  inches  long,  having  one  of  its  extremities  closed  by 
a  plate  of  plaster  of  Paris  about  half  an  inch  thick,  and 
well  dried.  When  the  tube  is  filled  by  displacement  with 
hydrogen,  and  then  set  upright  in  a  glass  of  water,  the 
level  of  the  liquid  rises  in  the  tube  so  rapidly,  that  its 
movement  is  apparent  to  the  eye,  and  speedily  attains  a 
height  of  several  inches  above  the  water  in  the  glass.  The 
gas  is  actually  rarefied  by  its  superior  diffusive  power  over 
that  of  the  external  air. 

It  is  impossible  to  over-estimate  the  importance  in  the 
economy  of  Nature  of  this  very  curious  law  affecting  the 
constitution  of  gaseous  bodies:  it  is  the  principal  means 
by  which  the  atmosphere  is  preserved  in  a  uniform  state, 
and  the  accumulation  of  poisonous  gases  and  exhalations 
in  towns  and  other  confined  localities  prevented. 
A  partial  separation  of  gases  and  vapors  of  unequal  diffusibility  may  be 
effected  by  allowing  the  mixture  to  permeate  through  a  plate  of  graphite  or 
porous  earthenware  into  a  vacuum.  This  effect,  called  atmolysis,  is  best  ex- 
hibited by  means  of  an  instrument  called  the  tube-afmoh/ser.  This  is  simply 
a  narrow  tube  of  unglazed  earthenware,  such  as  a  tobacco-pipe  stem,  two 
feet  long,  which  is  placed  within  a  shorter  tube  of  glass,  and  secured  in  its 

*  See  Bunsen's  Gasometry,  p.  203 ;  Graham's  Elements  of  Chemistry,  2d  ed.,  ii.  624 ;  Watts's 
Dictionary  of  Chemistry,  ii.  815. 


HYDROGEN.  139 

position  by  corks.  The  glass  tube  is  connected  with  an  air-pump,  and  the 
annular  space  between  the  two  tubes  is  made  as  nearly  vacuous  as  possible. 
Air  or  other  mixed  gas  is  then  allowed  to  flow  along  the  clay  tube  in  a  slow 
stream,  and  collected  as  it  issues.  The  gas  or  air  atmolysed  is,  of  course, 
reduced  in  volume,  much  gas  penetrating  through  the  pores  of  the  clay 
tube  into  the  air-pump  vacuum,  and  the  lighter  gas  diffusing  the  more  rap- 
idly, so  that  the  proportion  of  the  denser  constituent  is  increased  in  the  gas 
collected.  In  one  experiment,  the  proportion  of  oxygen  in  the  air,  after 
traversing  the  atmolyser,  was  increased  from  20-8  per  cent.,  which  is  the 
normal  proportion,  to  24-5  per  cent.  With  a  mixture  of  oxygen  and  hy- 
drogen, the  separation  is,  of  course,  still  more  considerable.* 

A  distinction  must  be  carefully  drawn  between  real  diffusion  through  small 
apertures,  and  the  apparently  similar  passage  of  gases  through  membran- 
ous diaphragms,  such  as  caoutchouc,  bladder,  gold-beater's  skin,  etc.  In 
this  mode  of  passage,  which  is  called  osmose,  the  rate  of  interchange  de- 
pends partly  on  the  relative  diffusibilities  of  the  gases,  partly  on  the  differ- 
ent degrees  of  adhesion  exerted  by  the  membrane  on  the  different  gases, 
by  virtue  of  which  the  gas  which  adheres  most  powerfully  penetrates  the 
diaphragm  most  easily  and,  attaining  the  opposite  surface,  mixes  with  the 
other.  A  sheet  of  caoutchouc  tied  over  the  mouth  of  a  wide-mouthed 
bottle  filled  with  hydrogen,  is  soon  pressed  inwards,  even  to  bursting.  If 
the  bottle  be  filled  with  air,  and  placed  in  an  atmosphere  of  hydrogen, 
the  swelling  and  bursting  takes  place  outwards.  If  the  membrane  is  moist, 
the  result  is  likewise  affected  by  the  different  solubilities  of  the  gases  in  the 
water  or  other  liquid  which  wets  it.  For  example,  the  diffusive  power  of 
carbonic  acid  into  atmospheric  air  is  very  small,  but  it  passes  into  the  latter 
through  a  wet  bladder  with  the  utmost  ease,in  virtue  of  its  solubility  in  the 
water  with  which  the  membrane  is  moistened.  It  is  by  such  a  process  that 
the  function  of  respiration  is  performed ;  the  aeration  of  the  blood  in  the 
lungs,  and  the  disengagement  of  the  carbonic  acid,  are  effected  through 
wet  membranes ;  the  blood  is  never  brought  into  actual  contact  with  the 
air,  but  receives  its  supply  of  oxygen,  and  disembarrasses  itself  of  carbonic 
acid,  by  this  kind  of  spurious  diffusion. 

The  high  diffusive  power  of  hydrogen  against  air  renders  it  impossible  to 
retain  that  gas  for  any  length  of  time  in  a  bladder  or  caoutchouc  bag ;  it  is 
even  unsafe  to  keep  it  long  in  a  gas-holder,  lest  it  should  become  mixed 
with  air  by  slight  accidental  leakage,  and  rendered  explosive. 

The  passage  of  gases  through  membranes  like  caoutchouc  or  varnished 
silk,  as  well  as  through  wet  membranes  like  bladder,  appears  to  depend 
upon  an  actual  liquefaction  of  the  gases,  which  then  become  capable  of  pen- 
etrating the  substance  of  the  membrane  (as  ether  and  naphtha  do),  and  may 
again  evaporate  on  the  surface  and  appear  as  gases.  The  unequal  absorp- 
tion of  gases  in  this  manner  often  effects  a  much  more  complete  separation 
of  the  components  of  a  gaseous  mixture  than  can  be  attained  by  the  atmo- 
lytic  method  above  described.  Thus,  Graham  has  shown  that  oxygen  is  ab- 
sorbed and  condensed  by  caoutchouc  two-and-a-half  times  more  abundantly 
than  nitrogen,  and  that  when  one  side  of  a  caoutchouc  film  is  freely  ex- 
posed to  the  air,  while  a  vacuum  is  produced  on  the  other  side,  the  film 
allows  41-6  per  cent,  of  oxygen  to  pass  through,  instead  of  21  per  cent, 
usually  present  in  the  air,  so  that  the  air  which  passes  through  is  capable  of 
rekindling  wood  burning  without  flame. 

Even  metals  appear  to  possess  this  power  of  absorbing  and  liquefying 
gases.  Deville  and  Troost  have  observed  the  remarkable  fact  that  hydrogen 
gas  is  capable  of  penetrating  platinum  and  iron  tubes  at  a  red  heat,  and 
Graham  is  of  opinion  that  this  effect  may  be  connected  with  a  power  resi- 
dent in  these  and  certain  other  metals  to  absorb  and'  liquefy  hydrogen, 
possibly  in  its  character  as  a  metallic  vapor.  Platinum  in  the  form  of 

*  Graham,  Phil.  Trans.  1863 


140  HYDROGEN. 

wire  or  plate,  at  a  low  red  heat,  can  take  up  3-8  volumes  of  hydrogen 
measured  cold,  and  palladium  foil  condenses  as  much  as  643  times  its  vol- 
ume of  hydrogen  at  a  temperature  below  100°  C.  In  the  form  of  sponge, 
platinum  absorbed  1-48  times  its  volume  of  hydrogen,  and  palladium  90 
volumes.  This  absorption  of  gases  by  metals  is  called  occlusion.* 

The  meteoric  iron  of  Lenarto  contains  a  considerable  quantity  of  oc- 
cluded hydrogen.  When  placed  in  a  good  vacuum,  it  yields  2-85  times  its 
volume  of  gas,  of  which  85-68  per  cent,  consist  of  hydrogen,  with  4-46 
carbon  monoxide  and  9-86  nitrogen.  Now,  hydrogen  has  been  recognized 
by  spectrum  analysis  in  the  light  of  the  fixed  stars,  and  constitutes,  ac- 
cording to  the  observations  of  father  Secchi,  the  principal  element  in  the 
atmosphere  of  a  numerous  class  of  stars.  "  The  iron  of  Lenarto,"  says 
Mr.  Graham,  "has,  no  doubt,  come  from  such  an  atmosphere,  in  which 
hydrogen  greatly  prevailed.  This  meteorite  may  be  looked  upon  as  holding 
imprisoned  within  it,  and  bringing  to  us,  the  hydrogen  of  the  stars."  f 

The  rates  of  effusion  of  gases,  that  is  to  say,  their  rates  of  passage 
through  a  minute  aperture  in  a  thin  plate  of  metal  or  other  substance  into 
a  vacuum,  follow  the  same  law  as  their  rates  of  diffusion,  that  is  to  say, 
they  are  inversely  as  the  square  roots  of  the  densities  of  the  gases.  Never- 
theless, the  phenomena  of  diffusion  and  effusion  are  essentially  different  in 
their  nature,  the  effusive  movement  affecting  masses  of  a  gas,  whereas  the 
diffusive  movement  affects  only  molecules ;  and  a  gas  is  usually  carried  by 
the  former  kind  of  impulse  with  a  velocity  many  thousand  times  greater 
than  by  the  latter.  Mixed  gases  are  effused  at  the  same  rates  as  one  gas 
of  the  actual  density  of  the  mixture:  and  no  separation  of  the  gases  oc- 
curs, as  in  diffusion  into  a  vacuum. 

The  law  of  effusion  just  stated  is  true  only  under  the  condition  that  the 
gas  shall  pass  through  a  minute  aperture  in  a  very  thin  plate.  If  the  plate 
be  thicker,  so  that  the  aperture  becomes  a  tube,  very  different  rates  of 
efflux  are  observed;  and  when  the  capillary  tube  becomes  considerably 
elongated,  so  that  its  length  exceeds  its  diameter  at  least  400  times,  the  rates 
of  flow  of  different  gases  into  a  vacuum  again  assume  a  constant  ratio  to 
each  other,  following,  however,  a  law  totally  distinct  from  that  of  effusion. 
The  principal  general  results  observed  with  relation  to  this  phenomenon  of 
"Capillary  Transpiration"  are  as  follows:  — 

1.  The  rate  of  transpiration  of  the  same  gas  increases,  cseteris  paribus, 
directly  as  the  pressure:  in  other  words,  equal  volumes  of  gas  at  different 
densities  require  times  inversely  proportional  to  their  densities.  ^  2.  With 
tubes  of  equal  diameter,  the  volume  transpired  in  equal  times  is  inversely 
as  the  length  of  the  tube.  8.  As  the  temperature  rises,  the  transpiration 
of  equal  volumes  becomes  slower.  4.  The  rates  of  transpiration  of  different 
gases  bear  a  constant  relation  to  each  other,  totally  independent  of  their 
densities,  or,  indeed,  of  any  known  property  of  the  gases.  Equal  weights 
of  oxygen,  nitrogen,  and  carbon  monoxide  are  transpired  in  equal  times ; 
so  likewise  are  equal  weights  of  nitrogen,  nitrogen  dioxide,  and  carbon  mon- 
oxide ;  and  of  hydrogen  chloride,  carbon  dioxide,  and  nitrogen  monoxide.  J 

COMBINATION   OF   HYDROGEN  WITH   OXYGEN. 

It  has  been  already  stated  that,  although  the  light  emitted  by  the  flame 
of  pure  hydrogen  is  exceedingly  feeble,  yet  the  temperature  of  the  flame  is 
very  high.  The  temperature  may  be  still  further  exalted  by  previously 
mixing  the  hydrogen  with  as  much  oxygen  as  it  requires  for  combination, 

*  Graham,  Phil.  Trans.  1866;  Journal  of  the  Chemical  Society,  [2]  v.  235. 

t  Proceorlinsjs  of  the  Royal  Society,  xv.  502 

J  Graham,  Phil.  Trans.  1846,  p.  591 ;  and  1S49,  p.  349 ;  also  Elements  of  Chemistry,  2d  ed.  i.  82. 


HYDROGEN. 


that  is,  as  will  presently  be  seen,  with  half  its  volume.  Such  a  mixture 
burns  like  gunpowder,  independently  of  the  external  air.  When  raised  to 
the  temperature  required  for  combination,  the  two  gases  unite  with  explo- 
sive violence.  If  a  strong  bottle,  holding  not  more  than  half  a  pint*  be 
filled  with  such  a  mixture,  the  introduction  of  a  lighted  match  or  red-hot 
wire  determines  in  a  moment  the  union  of  the  gases.  By  certain  precau- 
tions, a  mixture  of  oxygen  and  hydrogen  can  be  burned  at  a  jet  without 
communication  of  fire  to  the  contents  of  the  vessel;  the  flame  is  in  this  case 
solid. 

A  little  consideration  will  show,  that  all  ordinary  flames  burning  in  the 
air  or  in  pure  oxygen  are,  of  necessity,  hollow.  The  act  of  combustion  is 
nothing  more  than  the  energetic  union  of  the  substance  burned  with  the 
surrounding  oxygen  ;  and  this  union  can  take  place  only  at  the  surface  of 
the  burning  body.  Such  is  not  the  case,  however,  with  the  flame  now 
under  consideration  ;  the  combustible  and  the  oxygen  are  already  mixed, 
and  only  require  to  have  their  temperature  a  little  raised  to  cause  them  to 
combine  in  every  part.  The  flame  so  produced  is  very  different  in  physical 
characters  from  that  of  a  simple  jet  of  hydrogen  or  any  other  combustible 
gas;  it  is  long  and  pointed,  and  very  remarkable  in  appearance. 

The  safety-jet  of  Mr.  Hemming,  the  construction  of  which  involves  a 
principle  not,  yet  discussed,  may  be  adapted  to  a  common  bladder  contain- 
ing the  mixture,  and  held  under  the  arm,  and  the  gas  forced  through  the 
jet  by  a  little  pressure.  Although  this  jet,  properly  constructed,  is  believed 
to  be  safe,  it  is  best  to  use  nothing  stronger  than  a  bladder,  for  fear  of  in- 
jury in  the  event  of  an  explosion.  The  gases  are  often  contained  in  sepa- 
rate reservoirs,  a  pair  of  large  gas-holders,  for  example,  and  only  suffered 
to  mix  in  the  jet  itself,  as  in  the  contrivance  of  Professor  Daniell:  in  this 
way  all  danger  is  avoided.  The  eye  speedily  becomes  accustomed  to  the 
peculiar  appearance  of  the  true  hydro-oxygen  flame,  so  as  to  permit  the 
supply  of  each  gas  to  be  exactly  regulated  by  suitable  stop-cocks  attached 
to  the  jet  (fig.  98). 


Fig.  98. 


Fig.  99, 
P* 


A  piece  of  thick  platinum  wire  introduced  into  the  flame  of  the  hydro- 
oxygen  blowpipe  melts  with  the  greatest  ease;  a  watch-spring  or  small 


142  HYDROGEN. 

Bteel  file  burns  with  the  utmost  brilliancy,  throwing  off  showers  of  beautiful 
sparks;  an  incombustible  oxidized  body,  as  magnesia  or  lime,  becomes  so 
intensely  ignited  as  to  glow  with  a  light  insupportable  to  the  eye,  and  to 
be  susceptible  of  employment  as  a  most  powerful  illuminator,  as  a  sub- 
stitute for  the  sun's  rays  in  the  solar  microscope,  and  for  night-signals  in 
trigonometrical  surveys. 

If  a  long  glass  tube,  open  at  both  ends,  be  held  over  a  jet  of  hydrogen 
(fig.  99),  a  series  of  musical  sounds  are  sometimes  produced  by  the  partial 
extinction  and  rekindling  of  the  flame  by  the  ascending  current  of  air. 

These  little  explosions  succeed  each  other  at  regular  intervals,  and  so 
rapidly  as  to  give  rise  to  a  musical  note,  the  pitch  depending  chiefly  upon 
the  length  and  diameter  of  the  tube. 

Although  oxygen  and  hydrogen  may  be  kept  mixed  at  common  tempera- 
tures for  any  length  of  time,  without  combination  taking  place,  yet,  under 
particular  circumstances,  they  unite  quietly  and  without  explosion.  Many 
years  ago,  Professor  Dobereiner,  of  Jena,  made  the  curious  observation, 
that  finely  divided  platinum  possessed  the  power  of  determining  the  union 
of  the  gases;  and,  more  recently,  Mr.  Faraday  has  shown  that  the  state  of 
minute  division  is  by  no  means  indispensable,  since  rolled  plates  of  the 
metal  have  the  same  property,  provided  their  surfaces  are  absolutely  clean. 
Neither  is  the  effect  strictly  confined  to  platinum ;  other  metals,  as  palla- 
dium and  gold,  and  even  stones  and  glass,  exhibit  the  same  property,  al- 
though to  a  far  inferior  degree,  since  they  often  require  to  be  aided  by  a 
little  heat.  When  a  piece  of  platinum-foil,  which  has  been  cleaned  by  hot 
oil  of  vitriol  and  thorough  washing  with  distilled  water,  is  thrust  into  a 
jar  containing  a  mixture  of  oxygen  and  hydrogen  standing  over  water, 
combination  of  the  two  gasas  immediately  begins,  and  the  level  of  the  water 
rapidly  rises,  while  the  platinum  becomes  so  hot  that  drops  of  water  acci- 
dentally falling  upon  it  enter  into  ebullition.  If  the  metal  be  very  thin  and 
exceedingly  clean,  and  the  gases  very  pure,  its  temperature  rises  after  a 
time  to  actual  redness,  and  the  residue  of  the  mixture  explodes.  But  this 
is  an  effect  altogether  accidental,  and  dependent  upon  the  high  temperature 
of  the  platinum,  which  high  temperature  has  been  produced  by  the  pre- 
ceding quiet  combination  of  the  two  bodies.  When  the  platinum  is  reduced 
to  a  state  of  minute  division,  and  its  surface  thereby  much  extended,  it  be- 
comes immediately  red-hot  in  a  mixture  of  hydrogen  and  oxygen,  or  hydro- 
gen and  air;  a  jet  of  hydrogen  thrown  upon  a  little  of  the  spongy  metal, 
contained  in  a  glass  or  capsule,  is  at  once  kindled,  and  on  this  principle 
machines  for  the  production  of  instantaneous  light  have  been  constructed. 

These,  however,  act  well  only  when  constantly  used;  the  spongy  plati- 
num is  apt  to  become  damp  by  absorption  of  moisture  from  the  air,  and  its 
power  is  then  for  the  time  lost. 

The  best  explanation  that  can  be  given  of  these  curious  effects  is  to  sup- 
pose that  solid  bodies  in  general  have,  to  a  greater  or  less  extent,  the  prop- 
erty of  condensing  gases  upon  their  surfaces,  or  even  liquefying  them  (as 
shown  p.  139),  and  that  this  faculty  is  exhibited  preeminently  by  certain 
of  the  non-oxidizable  metals,  as  platinum  and  gold.  Oxygen  and  hydrogen 
may  thus,  under  these  circumstances,  be  brought,  as  it  were,  within  the 
sphere  of  their  mutual  attractions  by  a  temporary  increase  of  density, 
whereupon  combination  ensues. 

Coal-gas  and  ether  or  alcohol  vapor  may  be  made  to  exhibit  the  phenom- 
enon of  quiet  oxidation  under  the  influence  of  this  remarkable  surface-ac- 
tion. A  close  spiral  of  slender  platinum  wire,  a  roll  of  thin  foil,  or  even  a 
common  platinum  crucible,  heated  to  dull  redness,  and  then  held  in  a  jet  of 
coal-gas,  becomes  strongly  ignited,  and  remains  in  that  state  as  long  as  the 
supply  of  mixed  gas  and  air  is  kept  up,  the  temperature  being  maintained 
by  the  heat  disengaged  in  the  act  of  union.  Sometimes  the  metal  becomes 
white-hot,  and  then  the  gas  takes  fire. 


HYDROGEN. 


Fig.  100. 


A  very  pleasing  experiment  may  be  made  by  attaching  such  a  coil  of  wire 
to  a  cord,  and  suspending  it  in  a  glass  containing  a  few  drops  of  ether, 
having  previously  made  it  red-hot  in  the  flame  of  a  spirit- 
lamp.  The  wire  continues  to  glow  until  the  oxygen  of 
the  air  is  exhausted,  giving  rise  to  the  production  of  an 
irritating  vapor  which  attacks  the  eyes.  The  combustion 
of  the  ether  is  in  this  case  but  partial ;  a  portion  of  its 
hydrogen  is  alone  removed,  and  the  whole  of  the  carbon 
left  untouched. 

A  coil  of  thin  platinum  wire  may  be  placed  over  the 
wick  of  a  spirit-lamp,  or  a  ball  of  spongy  platinum  sus- 
tained just  above  the  cotton:  on  lighting  the  lamp,  and 
then  blowing  it  out  as  soon  as  the  metal  appears  red-hot, 
slow  combustion  of  the  spirit  drawn  up  by  the  capillarity 
of  the  wick  will  take  place,  accompanied  by  the  pungent 
vapors  just  mentioned,  which  may  be  modified,  and  even 
rendered  agreeable,  by  dissolving  in  the  liquid  some 
sweet-smelling  essential  oil  or  resin. 

Hydrogen  forms  numerous  compounds  with  other  bodies,  although  it  is 
greatly  surpassed  in  this  respect,  not  only  by  oxygen,  but  by  many  of  the 
other  elements.  The  chemical  relations  of  hydrogen  tend  to  place  it  among 
the  metals.  The  great  discrepancy  in  physical  properties  is  perhaps  more 
apparent  than  real.  Hydrogen  is  not  yet  known  in  the  solid  state,  while, 
on  the  other  hand,  the  vapor  of  the  metal  mercury  is  as  transparent  and 
colorless  as  hydrogen  itself.  This  vapor  is  only  about  seven  times  heavier 
than  atmospheric  air,  so  that  the  difference  in  this  respect  is  not  nearly  so 
great  as  that  in  the  other  direction  between  air  and  hydrogen. 

There  are  two  oxides  of  hydrogen  —  namely,  water,  and  a  very  peculiar 
substance,  discovered  in  the  year  1818  by  M.  Thenard,  called  hydrogen 
dioxide. 

It  appears  that  the  composition  of  water  was  first  demonstrated  in  the 
year  1781  by  Cavendish ;  *  but  the  discovery  of  the  exact  proportions  in 
which  oxygen  and  hydrogen  unite  in  generating  that  most  important  com- 
pound has,  from  time  to  time  to  the  present  day,  occupied  the  attention  of 
some  of  the  most  distinguished  cultivators  of  chemical 
science.  There  are  two  distinct  methods  of  research  in 
chemistry  —  the  analytical,  or  that  in  which  the  com- 
pound is  resolved  into  its  elements,  and  the  synthetical, 
in  which  the  elements  are  made  to  unite  and  produce 
the  compound.  The  first  method  is  of  much  more  gen- 
eral application  than  the  second ;  but  in  this  particular 
instance  both  may  be  employed,  although  the  results  of 
the  synthesis  are  the  more  valuable. 

The  decomposition  of  water  may  be  effected  by  voltaic 
electricity.  When  water  is  acidulated  so  as  to  render  it 
a  conductor,!  and  a  portion  interposed  between  a  pair 
of  platinum  plates  connected  with  the  extremities  of  a 
voltaic  apparatus  of  moderate  power,  decomposition  of 
the  liquid  takes  place  in  a  very  interesting  manner ;  oxy- 
gen, in  a  state  of  perfect  purity,  is  evolved  from  the  wa- 
ter in  contact  with  the  plate  belonging  to  the  copper  end 
of  the  battery,  and  hydrogen,  equally  pure,  is  disengaged  at  the  plate  con- 

*  A  claim  to  the  discovery  of  the  composition  of  water,  on  behalf  of  James  Watt,  has  been 
very  strongly  urged,  and  supported  by  such  evidence  that  the  reader  of  the  controversy  may 
be  led  to  the  conclusion  that  the  discovery  was  made  by  both  parties,  nearly  simultaneously, 
and  unknown  to  each  other.  See  the  article  "  Gas,"  by  Dr.  Paul,  in  Watts's  Dictionary  of  Chem- 
istry, ii.  780. 

t  See  the  section  on  "  Electro-chemical  Decomposition." 


Fig.  101. 


144 


HYDROGEN. 


Fig.  102. 


nected  with  the  zinc  extremity,  the  middle  portions  of  liquid  remaining  ap- 
parently unaltered.  By  placing  small  graduated  jars  over  the  platinum 
plates,  the  gases  can  be  collected,  and  their  quantities  determined.  The 
whole  arrangement  is  shown  in  fig.  101 ;  the  conducting  wires  pass  through 
the  bottom  of  the  glass  cup,  and  away  to  the  battery. 

When  this  experiment  has  been  continued  a  sufficient  time,  it  will  be 
found  that  the  volume  of  the  hydrogen  is  a  very  little  above  twice  that  of 
the  oxygen :  were  it  not  for  the  accidental  circumstance  of  oxygen  being 
sensibly  more  soluble  in  water  than  hydrogen,  the  proportion  of  two  to 
one  by  measure  would  come  out  exactly. 

Water,  as  Mr.  Grove  has  shown,  is  likewise  decomposed  into  its  constit- 
uents by  heat.       The   effect  is  produced  by  introducing  platinum  balls, 
ignited  by  electricity  or  other  means,  into  water  or  steam. 
The  two  gases  are   obtained  in  very  small  quantities  at  a 
time. 

When  oxygen  and  hydrogen,  both  as  pure  as  possible,  are 
mixed  in  the  proportions  mentioned,  passed  into  a  strong 
glass  tube  standing  over  mercury,  and  exploded  by  the  elec- 
tric spark,  all  the  mixture  disappears,  and  the  mercury  is 
forced  lip  into  the  tube,  filling  it  completely.  The  same 
experiment  may  be  made  with  the  explosion-vessel  or  eudi- 
ometer of  Cavendish  (fig.  102).  The  instrument  is  exhausted 
at  the  air-pump,  and  then  filled  from  a  capped  jar  with  the 
mixed  gases;  on  passing  an  electric  spark  by  the  wires 
shown  at  a,  explosion  ensues,  and  the  glass  becomes  bedewed 
with  moisture ;  and  if  the  stop-cock  be  then  opened  under 
water,  the  latter  will  rush  in  and  fill  the  vessel,  leaving 
merely  a  bubble  of  air,  the  result  of  imperfect  exhaustion. 
The  process  upon  which  most  reliance  is  placed,  is  that  in 
which  pure  copper  oxide  is  reduced  at  a  red-heat  by  hy- 
drogen, and  the  water  so  formed  is  collected  and  weighed. 
This  oxide  suffers  no  change  by  heat  alone,  but  the  momen- 
tary contact  of  hydrogen,  or  any  common  combustible  mat- 
ter, at  a  high  temperature,  suffices  to  reduce  a  corresponding 
portion  to  the  metallic  state.  Fig.  103  will  serve  to  convey 
some  idea  of  the  arrangement  adopted  in  researches  of  this 
kind. 

A  copious  supply  of  hydrogen  is  procured  by  the  action 
of  dilute  sulphuric  acid  upon  the  purest  zinc  that  can  be 
obtained ;  the  gas  is  made  to  pass  in  succession  through  so- 
lutions of  silver  and  strong  caustic  potash,  by  which  its 
purification  is  completed.  After  this  it  is  conducted  through 
a  tube  three  or  four  inches  in  length,  filled  with  fragments 
of  pumice-stone  steeped  in  concentrated  oil  of  vitriol,  or 
with  anhydrous  phosphoric  acid.  These  substances  have  so 
great  an  attraction  for  aqueous  vapor,  that  they  dry  the  gas 
completely  during  its  transit.  The  extremity  of  this  tube 
is  shown  at  a.  The  dry  hydrogen  thus  arrives  at  the  part 
of  the  apparatus  containing  the  copper  oxide  represented 
at  b;  this  consists  of  a  two-necked  flask  of  very  hard  white  glass,  main- 
tained at  a  red-heat  by  a  spirit-lamp  placed  beneath.  As  the  decomposition 
proceeds,  the  water  produced  by  the  reduction  of  the  oxide  begins  to  con- 
dense in  the  second  neck  of  the  flask,  whence  it  drops  into  the  receiver  c, 
provided  for  the  purpose.  A  second  desiccating  tube  prevents  the  loss  of 
aqueous  vapor  by  the  current  of  gas  which  passes  in  excess. 

Before  the  experiment  can  be  commenced,  the  copper  oxide,  the  purity 
of  which  is  well  ascertained,  must  be  heated  to  redness  for  some  time  in  a 


HYDJiOGEN.  145 

current  of  dry  air ;  it  is  then  suffered  to  cool,  and  very  carefully  weighed 
with  t lie  flask.  The  empty  receiver  and  second  drying-tube  are  also  weighed, 
the  disengagement  of  gas  set  up,  and  when  the  air  has  been  displaced,  heat 

Fig.  103. 


is  slowly  applied  to  the  oxide.  The  action  is  at  first  very  energetic ;  the 
oxide  often  exhibits  the  appearance  of  ignition;  but  as  the  decomposition 
proceeds,  it  becomes  more  sluggish,  and  requires  the  application  of  a  con- 
siderable heat  to  effect  its  completion. 

When  the  process  is  at  an  end,  and  the  apparatus  perfectly  cool,  the 
stream  of  gas  is  discontinued,  dry  air  is  drawn  through  the  whole  arrange- 
ment, and,  lastly,  the  parts  are  disconnected  and  reweighed.  The  loss  of 
the  copper  oxide  gives  the  oxygen;  the  gain  of  the  receiver  and  its 
drying-tube  indicates  the  water;  and  the  difference  between  the  two, 
the  hydrogen. 

A  set  of  experiments,  made  in  Paris  in  the  year  1820,*  by  Dulong  and 
Berzelius,  gave  as  a  mean  result,  for  the  composition  of  water  by  weight, 
8-009  parts  oxygen  to  1  part  hydrogen ;  numbers  so  nearly  in  the  proportion 
of  8  to  1,  that  the  latter  have  usually  been  assumed  to  be  true. 

More  recently  the  subject  has  been  reinvestigated  by  Dumas,  f  with  the 
most  scrupulous  precision,  and  the  above  supposition  fully  confirmed.  The 
composition  of  water  may  therefore  be  considered  as  established ;  it  con- 
tains by  weight  8  parts  oxygen  to  1  part  hydrogen,  and  by  measure,  1  vol- 
ume oxygen  to  2  volumes  hydrogen.  The  densities  of  the  gases,  as  already 
mentioned,  correspond  very  closely  with  these  results. 

The  physical  properties  of  water  are  too  well  known  to  need  lengthened 
description :  it  is,  when  pure,  colorless  and  transparent,  destitute  of  taste 
and  odor,  and  an  exceedingly  bad  conductor  of  electricity  of  low  tension. 
It  attains  its  greatest  density  towards  4-5°  C.  (40°  F.),  freezes  at  0°  C.  (32° 
F.),J  and  boils  under  the  ordinary  atmospheric  pressure  at  or  near  100°  C. 
(212°  F.).  It  evaporates  at  all  temperatures. 

The  weight  of  a  cubic  centimetre  of  water  at  the  maximum  density  is 
chosen  as  the  unit  of  weight  of  the  metrical  system,  and  called  a  gram; 
consequently  a  litre  or  cubic  decimetre  =  100  cubic  centimetres  of  water, 
at  the  same  temperature,  weighs  1000  grams,  or  1  kilogram. 

A  cubic  inch  of  water  at  16-7°  C.  (62°  F.)  weighs  252-45  grains;  a  cubic 
foot  weighs  nearly  1000  ounces  avoirdupois;  and  an  imperial  gallon  weighs 
70,000  grains,  or  10  Ibs.  avoirdupois.  Water  is  825  times  heavier  than  air. 
To  all  ordinary  observations,  it  is  incompressible;  very  accurate  experi- 
ments have  nevertheless  shown  that  it  does  yield  to  a  small  extent  when 
the  power  employed  is  very  great,  the  diminution  of  volume  for  each  atmo- 
sphere of  pressure  being  about  51-millionth  of  the  whole. 

Clear  water,  although  colorless  in  small  bulk,  is  blue  like  the  atmosphere 
when  viewed  in  mass.  This  is  seen  in  the  deep  ultramarine  tint  of  the 

*  Ann.  Chim.  Phys.  XT.  386.  t  Ibid.  3d  series,  viii.  1S9. 

J  According  to  Dufonr.  the  specific  gravity  of  ice  is  09175;  water,  therefore,  on  freezing, 
expands  by  JUth  of  its  volume. 

13 


146  HYDROGEN. 

ocean,  and  perhaps  in  a  still  more  beautiful  manner  in  the  lakes  of  Switzer- 
land and  other  Alpine  countries,  and  in  the  rivers  which  issue  from  them, 
the  slightest  admixture  of  mud  or  suspended  impurity  destroying  the  effect. 
The  same  magnificent  color  is  visible  in  the  fissures  and  caverns  found  in  the 
ice  of  the  glaciers,  which  is  usually  extremely  pure  and  transparent  within, 
although  foul  upon  the  surface. 

The  specific  gravity  of  steam  or  vapor  of  water  is  found  by  experiment 
to  be  0-625,  compared  with  air  at  the  same  temperature  and  pressure,  or  9 
as  compared  with  hydrogen.  Now,  it  has  been  already  shown  that  water 
is  composed  of  two  volumes  of  hydrogen  and  one  volume  of  oxygen ;  and 
if  the  weight  of  one  volume  of  hydrogen  be  taken  as  unity,  that  of  two 
volumes  hydrogen  (==  2)  and  one  volume  oxygen  (=  16)  will  together  make 
18,  which  is  the  weight  of  two  volumes  of  water-vapor.  Consequently 
water  in  the  state  of  vapor  consists  of  two  volumes  of  hydrogen  and  one  volume  of 
oxygen  condensed  into  two  volumes.  A  method  of  demonstrating  this  important 
fact  by  direct  experiment  has  been  devised  by  Dr.  Hofmann.  It  consists  in 
exploding  a  mixture  of  two  volumes  hydrogen  and  one  volume  oxygen,  by 
the  electric  spark,  in  a  eudiometer  tube  enclosed  in  an  atmosphere  of  the 
vapor  of  a  liquid  (amylic  alcohol)  which  boils  at  a  temperature  considerably 
above  that  of  boiling  water,  so  that  the  water  produced  by  the  combination 
of  the  gases  remains  in  the  state  of  vapor  instead  of  at  once  condensing  to 
the  liquid  form.  It  is  then  seen  that  the  three  volumes  of  mixed  gas  are 
reduced  after  the  explosion  to  two  volumes.* 

Water  seldom  or  never  occurs  in  nature  in  a  state  of  perfect  purity:  even 
the  rain  which  falls  in  the  open  country  contains  a  trace  of  ammoniacal 
salt,  while  rivers  and  springs  are  invariably  contaminated  to  a  greater  or 
less  extent  with  soluble  matters,  saline  and  organic.  Simple  nitration 
through  a  porous  stone  or  a  bed  of  sand  will  separate  suspended  impurities, 
but  distillation  alone  will  free  the  liquid  from  those  which  are  dissolved. 
In  the  preparation  of  distilled  water,  which  is  an  article  of  large  consump- 
tion in  the  scientific  laboratory,  it  is  proper  to  reject  the  first  portions 
which  pass  over,  and  to  avoid  carrying  the  distillation  to  dryness.  The 
process  may  be  conducted  in  a  metal  still  furnished  with  a  worm  or  condenser 
of  silver  or  tin ;  lead  must  not  be  used. 

The  ocean  is  the  great  recipient  of  the  saline  matter  carried  down  by  the 
rivers  which  drain  the  land:  hence  the  vast  accumulation  of  salts.  The 
following  table  will  serve  to  convey  an  idea  of  the  ordinary  composition  of 
sea-water ;  the  analysis  is  by  Dr.  Schweitzer, j-  of  Brighton,  the  water  being 
that  of  the  British  Channel : 

1000  grains  contained  — 

Water           .....  964-745 

Sodium  Chloride            .             .             .  27-059 

Potassium  Chloride              .             .             .  0-766 

Magnesium  Chloride      .             .             .  3-666 

Magnesium  Bromide            .             .             .  0-029 

Magnesium  Sulphate     .             .             .  2-296 

Calcium  Sulphate     ....  1-406 

Calcium  Carbonate        .             .             .  0-033 

Traces  of  Iodine  and  Ammoniacal  salt  •  • 


1000-000 

Its  specific  gravity  was  found  to  be  1-0274  at  15-5  C.  (60°  F.). 
Sea-water  is  liable  to  variations  of  density  and  composition  by  the  influ- 

*  For  a  description  of  the  apparatus,  see  Hofmann'a  "  Modern  Chemistry  "  (1865),  p.  51. 
f  Philosophical  Magazine,  July,  1839. 


HYDROGEN. 


147 


ence  of  local  causes,  such  as  the  proximity  of  large  rivers,  or  masses  of 
melting  ice,  and  other  circumstances. 

Natural  springs  are  often  impregnated  to  a  great  extent  with  soluble 
substances  derived  from  the  rocks  they  traverse:  such  are  the  various 
mineral  waters  scattered  over  the  whole  earth,  and  to  which  medicinal 
virtues  are  attributed.  Some  of  these  hold  ferrous  oxide  in  solution,  and 
are  effervescent  from  carbonic  acid  gas ;  others  are  alkaline,  probably  from 
traversing  rocks  of  volcanic  origin ;  some  contain  a  very  notable  quantity 
of  iodine  or  bromine.  Their  temperatures,  also,  are  as  variable  as  their 
chemical  nature.  A  tabular  notice  of  some  of  the  most  remarkable  of  these 
waters  will  be  found  in  the  Appendix. 

Water  enters  into  direct  combination  with  other  bodies,  forming  a  class 
of  compounds  called  hydrates;  the  action  is  often  very  energetic,  much 
heat  being  evolved,  as  in  the  case  of  the  slaking  of  lime,  which  is  really 
the  production  of  a  hydrate  of  that  base.  Sometimes  the  attraction  be- 
tween the  water  and  the  second  body  is  so  great  that  the  compound  is  not 
decomposable  by  any  heat  that  can  be  applied ;  the  hydrates  of  potash  and 
soda,  and  of  phosphoric  oxide,  furnish  examples.  Oil  of  vitriol  is  a  hy- 
drate of  sulphuric  oxide,  from  which  the  water  cannot  be  thus  separated. 

Water  very  frequently  combines  with  saline  substances  in  a  loss  inti- 
mate manner  than  that  above  described,  constituting  what  is  called  water 
of  crystallization,  from  its  connection  with  the  geometrical  figure  of  the  salt. 
In  this  case  it  is  easily  driven  off  by  the  application  of  heat. 

Lastly,  the  solvent  properties  of  water  far  exceed  those  of  any  other 
liquid  known.  Among  salts  a  very  large  proportion  are  soluble  to  a  greater 
or  less  extent,  the  solubility  usually  increasing  with  the  temperature,  so 
that  a  hot  saturated  solution  deposits  crystals  on  cooling.  There  are  a 
few  exceptions  to  this  law,  one  of  the  most  remarkable  of  which  is  coin- 


0°     10°     20°     30°       40°     50°      60°       70°       80°      90°      100°     110°  F. 
32°     50°     68°     86°     104°    122°     140°     158°    176°     194°     212°     230°  C. 

Temperature. 

mon  salt,  the  solubility  of  which  is  nearly  the  same  at  all  temperatures: 
the  hydrate  and  certain  organic  salts  of  calcium,  also,  dissolve  more  freely 
in  cold  than  in  hot  water. 


148  HYDROGEN'. 

The  diagram  (fig.  104)  exhibits  the  unequal  solubility  of  different 
in  water  of  different  temperatures.  The  lines  of  solubility  cut  the  verticals 
raised  from  points  indicating  the  temperatures,  upon  the  lower  horizontal 
line,  at  heights  proportioned  to  the  quantities  of  salt  dissolved  by  100 
parts  of  water.  The  diagram  shows,  for  example,  that  100  parts  of  water 
dissolve,  of  potassium  sulphate  3  pts.  at  0°  C.,  17  pts.  at  50°,  and  26  pts. 
at  100°.  There  are  salts  which,  like  sodium  chloride,  possess,  as  already 
mentioned,  very  nearly  the  same  degree  of  solubility  in  water  at  all  tem- 
peratures;  in  others,  like  potassium  sulphate  or  potassium  chloride,  the 
solubility  increases  directly  with  the  increment  of  temperature ;  in  others, 
again,  like  potassium  nitrate  or  potassium  chlorate,  the  solubility  aug- 
ments much  more  rapidly  than  the  temperature.  The  diagram  exhibits  the 
differences  in  the  deportment  of  these  different  salts  very  conspicuously, 
by  a  straight  horizontal  line,  by  a  straight  inclined  line,  and  lastly  by 
curves,  the  convexity  of  which  is  turned  toward  the  lower  horizontal  line. 

In  the  diagram,  the  solubility  of  salt  is  represented  by  the  quantity  of 
anhydrous  salt  dissolved  by  100  parts  of  water.  This  is,  in  fact,  the  com- 
mon mode  of  stating  the  solubility  of  salts.  It  is  obvious,  however,  that 
salts  containing  water  of  hydration  or  water  of  crystallization  cannot, 
within  certain  limits  of  temperature,  dissolve  in  water  in  the  anhydrous 
state,  but  must  be  dissolved  as  hydrates.  The  solubility  of  a  hydrated  salt 
frequently  differs  very  considerably  from  that  of  the  same  salt  in  the  anhy- 
drous state.  Again,  many  salts  form  more  than  one  hydrate ;  and  these 
several  hydrates  may  also  differ  in  their  solubility.  Sodium  sulphate 
forms  a  peculiar  hydrate,  consisting,  in  100  parts,  of  53  parts  of  anhy- 
drous salt  and  47  parts  of  water,  which  is  obtained  in  crystals,  when  a 
solution  of  sodium  sulphate,  saturated  at  100°  C.  (212°  F.),  is  considerably 
cooled  out  of  contact  with  the  air:  this  hydrate  is  much  more  soluble  than 
Glauber's  salt,  the  other  hydrate  of  sodium  sulphate,  which  differs  from 
the  former  one  in  its  crystalline  form,  and  consists,  in  100  parts,  of  44-2 
parts  of  anhydrous  salt  and  55-8  parts  of  water.  When  a  solution  of 
sodium  sulphate  is  saturated  at  the  boiling-point  of  water,  and  cooled  to 
the  common  temperature  without  depositing  any  crystals,  the  salt  exists  in 
the  form  of  the  more  soluble  hydrate.  This  salt,  when  coming  in  contact 
with  the  dust  of  the  air,  or  with  a  small  crystal  oC  common  Glauber's  salt, 
is  suddenly  transformed  into  the  less  soluble  hydrate,  part  of  which  sepa- 
rates from  the  solution,  in  the  form  of  Glauber's  salt.  From  0°  to  33°  C. 
(32°  to  91°  F.)  sodium  sulphate  dissolves  as  Glauber's  salt,  the  solubility  of 
which  increases  with  the  temperature;  hence  the  rapid  rise  of  the  curve 
representing  the  solubility  of  the  salt  in  the  diagram.  Above  33°  C. 
(91°  F.)  the  hydrate  of  sodium  sulphate  is,  even  in  solution,  decomposed, 
being  more  and  more  thoroughly  converted  into  the  anhydrous  salt  as  the 
temperature  increases.  Sodium  sulphate  appears,  however,  far  less  solu- 
ble in  the  anhydrous  state,  and  hence  the  diminution  of  solubility  of  the 
salt  when  its  solution  is  heated  above  33°  C.  (91°  F.),  which  is  exhibited  by 
the  diagram. 

Liquid  Diffusion.  Dialysis. — When  a  solution  having  a  sp.  gr.  greater 
than  water  is  introduced  into  a  cylindrical  glass  vessel,  and  then  water  very 
cautiously  poured  upon  it,  in  such  a  manner  that  the  two  layers  of  liquid 
remain  unmoved,  the  substance  dissolved  in  the  lower  liquid  will  gradually 
pass  into  the  supernatant  water,  though  the  vessel  may  have  been  left  un- 
disturbed, and  the  temperature  remain  unchanged.  This  gradual  passage 
of  a  dissolved  substance  from  its  original  solution  into  pure  water,  taking 
place  notwithstanding  the  higher  specific  gravity  of  the  substance  which 
opposes  this  passage,  is  called  the  diffusion  of  liquids.  The  phenomena  of  this 
diffusion  have  been  lately  investigated  by  Mr.  Graham,  who  has  arrived  at 
very  important  results.  Different  substances,  when  in  solution  of  the  same 


HYDROGEN. 


149 


concentration,  and  under  other  similar  circumstances,  diffuse  with  very 
unequal  velocity.  Hydrochloric  acid,  for  instance,  diffuses  with  greater 
rapidity  than  potassium  chloride,  potassium  chloride  more  rapidly  than 
sodium  chloride,  and  the  latter,  again,  more  quickly  than  magnesium  sul- 
phate ;  gelatin,  albumin,  and  caramel  diffuse  very  slowly.  Diffusion  is 
generally  found  to  take  place  more  rapidly  at  high  than  at  low  temperatures. 
Diffusion  is  more  particularly  rapid  with  crystallized  substances,  though 
not  exclusively,  for  hydrochloric  acid  and  alcohol  are  among  the  highly 
diffusive  bodies.  Diffusion  is  slow  with  non-crystalline  bodies,  which,  like 
gelatin,  are  capable  of  forming  a  jelly,  though  even  here  exceptions  are 
met  with.  Mr.  Graham  calls  the  substances  of  great  diffusibility  crystal- 
lot  Is y  the  substances  of  low  diffusibility  colloids.  The  unequal  power  of 
diffusion  with  which  different  substances  are  endowed  frequently  furnishes 
the  means  of  separating  them.  When  water  is  poured  with  caution,  so  as 
to  prevent  mixing,  upon  a  solution  containing  equal  quantities  of  potassium 
chloride  and  sodium  chloride,  the  more  diffusible  potassium  chloride  travels 
more  rapidly  upwards  than  the  less  diffusible  sodium  chloride,  and  very 
considerable  portions  of  potassium  chloride  will  have  reached  the  upper 
layers  of  the  water  before  the  sodium  chloride  has  arrived  there  in  ap- 
preciable quantity.  The  separation  of  rapidly  diffusible  crystalloids  and 
slowly  diffusible  colloils  succeeds  still  better. 

A  more  perfect  separation  of  crystalloids  and  colloids  may  be  accom- 
plished in  the  following  manner:  Mr.  Graham  has  made  the  important  ob- 
servation, that  certain  membranes,  and  also  parchment  paper,  when  in 
contact,  on  the  one  surface,  with  a  solution  containing  a  mixture  of  crys- 
talloilal  and  coll»ilal  substances,  and,  on  the  other  surface,  with  pure 
water,  will  permit  the  passage  to  the  water  of  the  crystalloids,  but  not  of 
the  colloids.  To  carry  out  this  important  mode  of  separation,  which  is  des- 
ignated by  the  term  dialysis,  the  lower  mouth  of  a  glass  vessel,  open  on 
both  sides  (fig.  105),  is  tied  over  with  parchment  paper  placed  upon  an  .ap- 
propriate support  (fig.  106),  and  transferred,  together  with  the  latter,  into 
a  larger  vessel  filled  with  water  (fig.  107) ;  or  the  vessel  may  be  suspended, 
as  shown  in  fig.  108.  The  liquid  containing  the  different  substances  in 


Fig.  105. 


Fig.  108. 


solution  is  then  poured  into  the  inner  vessel,  so  as  to  form  a  layer  of 
about  half  an  inch  in  height  upon  the  parchment  paper.  The  crystalloidal 
substances  gradually  pass  through  the  parchment  paper  into  the  outer 


150 


HYDROGEN. 


water,  which  may  be  renewed  from  time  to  time :  the  colloidal  substances 
are  almost  entirely  retained  by  the  liquid  in  the  inner  vessel.  In  this  man- 
ner Mr.  Graham  has  prepared  several  colloids,  free  from  crystalloids;  lie 
has  shown,  moreover,  that  poisonous  crystalloids,  such  as  arscnious  acid 
or  strychnine,  even  when  mixed  with  very  large  proportions  of  colloidal 
substances,  pass  over  into  the  water  of  the  dialyzer  in  such  a  state  of 
purity  that  their  presence  may  be  established  by  re-agents  with  the  utmost 
facility. 

Osmose. — When  two  different  liquids  are  separated  by  a  porous  dia- 
phragm, as,  for  instance,  by  a  membrane,  and  the  liquids  mix  through  this 
diaphragm,  it  is  found  that  in  most  cases  the  quantities  travelling  in  op- 
posite direction  are  unequal.  Suppose  three  cylinders,  the  lower  mouths 
of  which  are  tied  over  Avith  bladders,  filled  respectively  with  concentrated 
solutions  of  copper  sulphate,  sodium  chloride,  and  alcohol,  and  let  them  be 
immersed  in  vessels  containing  water  to  such  a  depth  that  the  liquids  inside 
and  outside  are  level  (fig.  109).  After  some  time  the  liquid  within  the 
tube  is  found  to  have  risen  appreciably  above  the  level  of  the  water 
(fig.  110).  On  the  other  hand,  if  the  cylinder  tilled  with  pure  water  be  im- 
mersed in  a  solution  of  copper  sulphate,  or  of  sodium  chloride,  or  in  al- 
cohol, the  liquid  in  the  cylinder  is  seen  to  diminish  after  sometime  (fig  111). 
A  larger  quantity  of  water  passes  through  the  bladder  into  the  solution  of 


Fig.  110. 


Fig.  111. 


copper  sulphate,  of  sodium  chloride,  or  into  alcohol,  than  the  amount  of 
either  of  these  three  liquids  which  passes  through  the  bladder  into  the 
water.  The  mixing  of  dissimilar  substances  through  a  porous  diaphragm 
is  called  osmose.  The  passage  in  larger  proportion  of  one  liquid  into  an- 
other is  designated  by  the  term  exosjnose. 

These  phenomena  are  due  to  the  attraction  which  the  two  liquids  have 
for  each  other,  and  to  the  difference  of  the  attraction  exercised  by  the 
diaphragm  upon  these  liquids.  Bladder  takes  up  a  much  larger  quantity 
of  water  than  of  a  solution  of  salt  or  of  alcohol.  Very  rarely  only  one  of 
the  liquids  traverses  the  diaphragm;  generally  two  currents  of  unequal 
strength  move  in  opposite  directions.  When  water  is  separated  by  an 
animal  membrane  from  a  solution  of  salt  or  from  alcohol,  not  only  is  a 
transition  of  water  to  these  liquids  observed,  but  a  small  quantity  of 
hydrochloric  acid  and  of  alcohol  also  passes  over  into  the  water.  In  some 
cases,  however,  when  colloidal  substances  in  concentrated  solutions  are  on 
one  side  of  the  diaphragm  and  water  on  the  other,  the  latter  alone  traverses 
the  diaphragm,  not  a  trace  of  the  former  passing  through  to  the  water. 

Water  likewise  dissolves  gases.  Solution  of  gases  in  water  (or  in  other 
liquids)  is  called  absorption,  unless  this  solution  gives  rise  to  the  formation 
of  chemical  compounds  in  definite  proportions.  The  phenomena  of  absorp- 


HYDROGEN. 


151 


tion  have  been  more  particularly  studied  by  Bunsen,  and  it  is  to  this  phi- 
losopher that  we  are  indebted  for  the  most  accurate  examination  of  this 
subject. 

Water  dissolves  very  unequal  quantities  of  the  different  gases  and  very 
unequal  quantities  of  the  same  gas  at  different  temperatures.  1  vol.  of 
water  absorbs,  at  the  temperatures  stated  in  the  table,  and  under  the  pres- 
sure of  30  inches  of  mercury,  the  following  volumes  of  different  gases, 
measured  at  0°  C.  and  30  inches  pressure : 


10° 

20° 


0°C. 
10° 
20° 
30° 
40° 


Oxygen. 

0-041 
0-033 
0-028 

Chlorine. 

2-59 
2-16 
1-75 
1-37 


Nitrogen. 

0-020 
0-016 
0-014 

Hydrogen 
Sulphide. 

4-37 
3-59 
2-91 
2-33 
1-86 


Hydrogen. 

0.019 
0-019 
0-019 

Sulphurous 
Oxide. 

53-9 
3G-4 
27-3 
20-4 
15-6 

Nitrogen 
Monoxide. 

1-31 

0-92 
0-67 

Hydrochlo- 
ric Acid. 

505 
472 
441 
412 

387 

Carbon 
Dioxide. 

1.80 
1-18 
0-90 

Ammo- 
nia. 

1180 
898 
680 
536 
444 


When  the  pressure  increases,  a  larger  quantity  of  the  gases  is  absorbed. 
Gases  moderately  soluble  in  water  follow  in  their  solubility  the  law  of 
Henry  and  Dalton,  according  to  which  the  quantity  of  gas  dissolved  is  pro- 
portional to  the  pressure.  At  10°  C.  1  vol.  of  water  absorbs  under  a  pres- 
sure of  1  atmosphere  1-18  vol.  of  carbon  dioxide,  measured  at  0°  and  under 
a  pressure  of  30  inches  mercury.  The  quantity  of  carbon  dioxide  dissolved 
under  a  pressure  of  2  atmospheres,  and  measured  under  conditions  pre- 
cisely similar  to  those  of  the  previous  experiments,  equals  2-36  vol.  Again, 
1  vol.  of  water  dissolves  under  a  pressure  of  *-  atmosphere,  0.59  vol.  of 
carbon  dioxide  also  measured  at  0°  and  under  30  inches  of  mercury.  Gases 
which  are  exceedingly  soluble  in  water  do  not  obey  this  law,  except  at 
higher  temperatures,  when  the  solubility  has  been  already  considerably 
diminished. 

It  deserves,  however,  to  be  noticed,  that  the  pressure  which  determines 
the  rate  of  absorption  of  a  gas  is  by  no  means  the  general  pressure  to 
which  the  absorbing  liquid  is  exposed,  but  that  pressure  which  the  gas 
under  consideration  would  exert  if  it  were  alone  present  in  the  space  with 
which  the  absorbing  liquid  is  in  contact.  Thus,  supposing  water  to  be  in 
contact  with  a  mixture  of  1  vol.  of  carbon  dioxide  and  3  vol.  of  nitrogen, 
under  a  pressure  of  4  atmospheres,  the  amount  of  carbon  dioxide  dissolved 
by  the  water  will  be  by  no  means  equal  to  that  which  the  water  would  have 
absorbed  if  it  had  been  at  the  same  pressure  of  4  atmospheres  in  contact 
with  pure  carbon  dioxide.  In  a  mixture  of  carbon  dioxide  and  nitrogen 
in  the  stated  proportions,  the  carbon  dioxide  exercises  only  },  the  nitrogen 
only  f,  of  the  total  pressure  of  the  gaseous  mixture  (4  atmospheres);  the 
partial  pressure  due  to  the  carbon  dioxide  is  in  this  case  1  atmosphere,  that 
due  to  the  nitrogen  3  atmospheres;  and  water,  though  exposed  to  a  pressure 
of  4  atmospheres,  cannot,  under  these  circumstances,  absorb  more  carbon 
dioxide  than  it  would  if  it  were  in  contact  with  pure  carbon  dioxide  under 
a  pressure  of  1  atmosphere. 

It  is  necessary  to  bear  this  in  mind  in  order  to  understand  why  the  air 
which  is  absorbed  by  water  out  of  the  atmosphere  differs  in  composition 
from  atmospheric  air.  The  latter  consists  very  nearly  of  21  vol.  of  oxygen 
and  79  vol.  of  nitrogen  In  atmospheric  air  which  acts  under  a  pressure  of 
1  atmosphere,  the  oxygen  exerts  a  partial  pressure  of  T?^,  the  nitrogen  a 


152  HYDROGEN. 

partial  pressure  of  T^97  atmosphere.  At  10°  C.  (50°  F.)  1vol.  of  water  (see 
the  above  table)  absorbs  0-033  vol.  of  oxygen,  and  0-016  vol.  of  nitrogen, 
supposing  these  gases  to  act  in  the  pure  state  under  a  pressure  of  1  atmo- 
sphere. But  under  the  partial  pressures  just  indicated,  water  of  10°  C. 
cannot  absorb  more  than  T2J^  X  0-033  =  0-007  of  oxygen,  and  T7^-  x  0  01G 
=  0-013  vol.  of  nitrogen.  In  0-007 -j- 0-013  =  0-020  vol.  of  gaseous  mixture 
absorbed  by  water  there  are  consequently  0-007  vol.  of  oxygen,  and  0-013 
vol.  of  nitrogen,  or  in  20  vol.  of  this  mixture,  7  vol.  of  oxygen  and  13  vol. 
of  nitrogen,  or  in  100  vol.  of  the  gaseous  mixture,  35  vol.  of  oxygen  and 
69  vol.  of  nitrogen.  The  air  contained  at  the  common  temperature  in 
water  is  thus  seen  to  be  very  much  richer  in  oxygen  than  ordinary  atmo- 
spheric air. 

Water  containing  a  gas  in  solution,  when  exposed  in  a  vacuum  or  in  a 
space  filled  with  another  gas,  allows  the  gas  absorbed  to  escape  until  the 
quantity  retained  corresponds  with  the  share  of  the  pressure  belonging  to 
the  gas  evolved.  If  the  latter  be  constantly  removed  by  a  powerful  ab- 
sorbent or  by  a  good  air-pump,  it  is  in  most  cases  easy  to  separate  every 
trace  of  gas  from  the  water.  The  same  result  is  obtained  when  water  con- 
taining a  gas  in  solution  is  exposed  in  a  space  of  comparatively  infinite 
size  filled  with  another  gas.  Water  in  which  nitrogen  monoxide  is  dis- 
solved loses  the  latter  entirely  by  mere  exposure  to  the  atmosphere,  and 
the  gas  evolved  cannot,  at  any  moment,  exert  more  than  an  infinitely  small 
share  of  the  pressure.  If  water  be  freed  from  gases  by  ebullition,  the 
separation  depends  partly  upon  the  diminution  of  the  solubility  by  the  in- 
crease of  temperature,  partly  also  upon  the  formation  above  the  surface 
of  the  liquid  of  a  constantly  renewed  atmosphere  into  which  the  gas  still 
retained  by  the  liquid  may  escape. 

Some  gases  which  are  absorbed  in  large  quantities,  and  very  quickly  by 
water,  —  hydrochloric  acid,  for  instance, — cannot  be  perfectly  ex'pelled 
either  by  the  protracted  action  of  another  gas  (exposure  to  the  atmosphere) 
or  by  ebullition :  in  such  cases  the  liquid  still  charged  with  gas  evaporates 
as  a  whole  when  it  has  assumed  a  certain  composition.  This  composition 
varies,  however,  if  the  liquid  be  submitted  to  a  current  of  air,  with  the 
temperature ;  and  if  it  be  boiled,  with  the  pressure  under  which  ebullition 
takes  place. 

Liquids  also  lose  the  gas  they  contain  in  solution  by  freezing:  hence  the 
air-bubbles  in  ice,  which  consist  of  the  air  which  had  been  absoi'bed  from 
the  atmosphere  by  the  water.  Gas  is  retained  by  liquids  at  the  freezing 
temperature  only  when  it  forms  a  chemical  combination  in  definite  propor- 
tion with  the  liquid.  Water  containing  chlorine  or  sulphurous  acid  in  so- 
lution freezes  without  evolution  of  gas,  with  formation  of  solid  hydrates  of 
chlorine  or  sulphurous  acid. 

Pure  water  generally  dissolves  gases  more  copiously  than  water  contain- 
ing solid  bodies  in  solution  (salt  water,  for  instance).  If  in  some  few  cases 
exceptions  are  observed  to  take  place,  they  appear  to  depend  upon  the  for- 
mation of  feeble  but  true  chemical  compounds  in  definite  proportion ;  the 
fact  that  carbon  dioxide  is  more  copiously  absorbed  by  water  containing 
sodium  phosphate  in  solution  than  by  pure  water  may  perhaps  be  explained 
in  this  manner. 

When  water  is  heated  in  a  strong  vessel  to  a  temperature  above  that  of 
the  ordinary  boiling-point,  its  solvent  powers  are  still  further  increased. 
Dr.  Turner  inclosed  in  the  upper  part  of  a  high-pressure  steam-boiler, 
worked  at  149°  C.  (300°  F.),  pieces  of  plate  and  crown  glass.  At  the  ex- 
piration of  four  months  the  glass  was  found  completely  corroded  by  the 
action  of  the  water;  what  remained  was  a  white  mass  of  silica,  destitute 
of  alkali,  while  stalactites  of  siliceous  matter,  above  an  inch  in  length, 
depended  from  the  little  wire  cage  which  enclosed  the  glass.  This  experi- 


NITROGEN.  153 

ment,  tends  to  illustrate  the  changes  which  may  be  produced  by  the  action 
of  water  at  a  high  temperature  in  the  interior  of  the  earth  upon  felspathic 
and  other  rocks.  The  phenomenon  is  manifest  in  the  Geyser  springs  of 
Iceland,  which  deposit  siliceous  sinter.* 

HYDROGEN  DIOXIDE, f  sometimes  called  oxygenated  water,  is  an  exceedingly 
interesting  substance,  but  very  difficult  of  preparation.  It  is  formed  by  dis- 
solving barium  dioxide  in  dilute  hydrochloric  acid  carefully  cooled  by  ice, 
and  then  precipitating  the  barium  by  sulphuric  acid;  the  excess  of  oxygen 
of  the  dioxide,  instead  of  being  disengaged  as  gas,  unites  with  a  portion 
of  the  water,  and  converts  it  into  hydrogen  dioxide.  This  treatment  is 
repeated  with  the  same  solution,  and  fresh  portions  of  the  barium  dioxide, 
until  a  considerable  quantity  of  the  latter  has  been  consumed,  and  a  cor- 
responding amount  of  hydrogen  dioxide  formed.  The  liquid  yet  contains 
hydrochloric  acid,  to  get  rid  of  which  it  is  treated  in  succession  with  silver 
sulphate  and  baryta-water.  The  whole  process  requires  the  utmost  care 
and  attention.  The  barium  dioxide  itself  is  prepared  by  exposing  pure 
baryta,  contained  in  a  red-hot  porcelain  tube,  to  a  stream  of  oxygen.  The 
solution  of  hydrogen  dioxide  may  be  concentrated  under  the  air-pump 
receiver  until  it  acquires  the  specific  gravity  of  1-45.  In  this  state  it  pre- 
sents the  aspect  of  a  colorless,  transparent,  inodorous  liquid,  possessing 
remarkable  bleaching  powers.  It  is  very  prone  to  decomposition;  the  least 
elevation  of  temperature  causes  effervescence,  due  to  the  escape  of  oxygen 
gas;  near  100°  it  is  decomposed  with  explosive  violence.  Hydrogen  dioxide 
contains  exactly  twice  as  much  oxygen  as  water,  or  16  parts  to  1  part  of 
hydrogen. 

A  trioxide  of  hi/drogen  is  said  to  exist,  although  it  has  never  been  obtained 
in  the  pure  state.  It  is  likewise  a  powerful  oxidizing  agent,  and  altogether 
similar  in  its  properties  to  the  dioxide.  According  to  the  researches  of 
Dr.  Baumert,  minute  quantities  of  this  substance  are  formed  in  the  decom- 
position of  water  by  electricity,  and  impart  the  odor  by  which  the  prod- 
ucts of  this  process  are  characterized  ;  but,  according  to  the  experiments 
of  Andrews  and  others,  already  referred  to  (p.  135),  the  supposed  trioxide 
really  consists  of  active  oxygen  or  ozone,  with  a  small  quantity  of  hydrogen 
dioxide. 


NITROGEN. 

Nitrogen  J  constitutes  about  four-fifths  of  the  atmosphere,  and  enters  into 
a  great  variety  of  combinations.  It  may  be  prepared  by  several  methods. 
One  of  the  simplest  of  these  is  to  burn  out  the  oxygen  from  a  confined  por- 
tion of  air  by  phosphorus,  or  by  a  jet  of  hydrogen. 

A  small  porcelain  capsule  is  floated  on  the  water  of  the  pneumatic  trough, 
and  a  piece  of  phosphorus  is  placed  in  it  and  set  on  fire.  A  bell-jar  is 
then  inverted  over  the  whole,  and  suffered  to  rest  on  the  shelf  of  the 

*  Philosophic,-)]  Mnpa/ino.  Oct.  1834. 

f  In  symbols  the  composition  of  water  and  hydrogen  dioxide  is  thus  expressed:  — 

Wator OH2. 

Hydrogen  dioxide 02H/;. 

J  7.  c.  Generator  of  nitre;  also  called  Azote,  from  a,  privative,  and  £w>j,  life. 


154  NITROGEN. 

trough,  so  as  to  project  a  little  over  its  edge.     At  first  the  heat  causes 
expansion  of  the   air  of  the  jar,    and    a  few  bubbles  are  expelled,  after 
which  the  level  of  the  water  rises  considerably.    When 
Fig.\\1.  the  phosphorus  becomes  extinguished  by  exhaustion 

of  the  oxygen,  and  time  has  been  given  for  the  sub- 
sidence of  the  cloud  of  finely  divided  snow-like  phos- 
phoric oxide  which  floats  in  the  residual  gas,  the 
nitrogen  may  be  transferred  into  another  vessel,  and 
its  properties  examined. 

Prepared  by  the  foregoing  process,  nitrogen  is  con- 
taminated with  a  little  vapor  of  phosphorus,  which 
communicates  its  peculiar  odor.  A  preferable  method 
is  to  fill  a  porcelain  tube  with  turnings  of  copper,  or, 
still  better,  with  the  spongy  metal  obtained  by  redu- 
cing the  oxide  with  hydrogen;  to  heat  this  tube  to  red- 
ness, and  then  pass  through  it  a  slow  stream  of  at- 
mospheric air,  the  oxygen  of  which  is  entirely  removed 
during  its  progress  by  the  heated  copper. 

If  chlorine  gas  be  passed  into  solution  of  ammonia,  the  latter  substance, 
which  is  a  compound  of  nitrogen  with  hydrogen,  is  decomposed ;  the  chlorine 
combines  with  the  hydrogen,  and  the  nitrogen  is  set  free  with  effervescence. 
In  this  manner  very  pure  nitrogen  can  be  obtained.  In  making  this  ex- 
periment, it  is  necessary  to  stop  short  of  saturating  or  decomposing  the 
whole  of  the  ammonia ;  otherwise  there  will  be  great  risk  of  accident  from 
the  formation  of  an  exceedingly  dangerous  explosive  compound,  produced 
by  the  contact  of  chlorine  with  an  ammoniacal  salt. 

Another  very  easy  and  perfectly  safe  method  of  obtaining  pure  nitrogen 
is  to  decompose  a  solution  of  potassium  nitrite  with  ammonium  chloride 
(sal-ammoniac).  The  potassium  nitrite  is  prepared  by  passing  the  red 
vapors  of  nitrous  acid  obtained  by  heating  dilute  nitric  acid  with  starch 
into  a  solution  of  caustic  potash.  On  boiling  the  resulting  solution  with 
sal-ammoniac,  nitrogen  gas  is  evolved,  while  potassium  chloride  remains 
in  solution. * 

Nitrogen  is  destitute  of  color,  taste,  and  odor;  it  is  a  little  lighter  than 
air,  its  density  being,  according  to  Dumas,  0-972.  A  litre  of  the  gas  at  0° 
C.  and  760  mm.  barometric  pressure  weighs  1-25658  gram.  100  cubic  inches, 
at  60°  F.  and  30  inches  barometer,  weigh  30-14  grains.  Nitrogen  is  in- 
capable of  sustaining  combustion  or  animal  existence,  although,  like  hydro- 
gen, it  has  no  positive  poisonous  properties;  neither  is  it  soluble  to  any 
notable  extent  in  water  or  in  caustic  alkali;  it  is,  in  fact,  best  character- 
ized by  negative  properties. 

The  exact  composition  of  the  atmosphere  has  repeatedly  been  made  the 
subject  of  experimental  research.  Besides  nitrogen  and  oxygen,  the  air 
contains  a  little  carbon  dioxide  (carbonic  acid),  a  very  variable  proportion 
of  aqueous  vapor,  a  trace  of  ammonia,  and,  perhaps,  a  little  carburetted 
hydrogen.  The  oxygen  and  nitrogen  are  in  a  state  of  mixture,  not  of  com- 
bination, yet  their  ratio  is  always  uniform.  Air  has  been  brought  from 
lofty  Alpine  heights,  and  compared  with  that  from  the  plains  of  Egypt; 
it  has  been  brought  from  an  elevation  of  21.000  feet  by  the  aid  of  the  bal- 
loon; it  has  been  collected  and  examined  in  London  and  Paris,  and  many 
other  places;  still  the  proportion  of  oxygen  and  nitrogen  remains  unaltered, 
the  diffusive  energy  of  the  gases  being  adequate  to  maintain  this  perfect 
uniformity  of  mixture.  The  carbon  dioxide,  on  the  ccntrary,  being  much 

*  The  reaction  is  represented  by  the  equation, 

NQ2K       +       NII4C1       -        KC1       -f  20II2     +      N2 

Potassium         Ammonium        Potassium  "Water.        Nitrogen 

nitrite.               chloride.            chloride.  gas. 


NITROGEN,  s 


155 


influenced  by  local  causes,  varies  considerably.  In  the  following  table  the 
proportions  of  oxygen  and  nitrogen  are  given  on  the  authority  of  Duinas, 
and  the  carbon  dioxide  on  that  of  De  Saussure:  the  ammonia,  the  discovery 
of  which  in  atmospheric  air  is  due  to  Liebig,  is  too  small  in  quantity  for 
direct  estimation. 


Nitrogen 
Oxygen 


Composition  of  the  Atmosphere. 
By  weight. 
77  parts 
23     " 


By  measure. 
79-19 
20-81 


100  100-00 

Carbon  dioxide,  from  3-7  measures  to  6-2  measures  in  10,000  measures 

of  air. 

Aqueous  vapor  variable,  depending  much  upon  the  temperature. 
Ammonia,  a  trace. 

Dr.  Frankland  has  analyzed  samples  of  air  taken  by  himself  in  the  valley 
of  Chamouni,  on  the  summit  of  Mont  Blanc,  and  at  the  Grands  Mulcts. 
The  following  are  the  results  of  his  analyses: 


Chamouni  (3000  feet) 
Grands  Mulcts  (11,000  feet) 
Mont  Blanc  (15,732  feet)    . 


Carbon  dioxide. 
.    0-OC3 
0-111 
.    0-061 


Oxygen. 
20-894 
20-802 
20-903 


Fig.  113. 


A  litre  of  pure  and  dry  air  at  0°  C.  and  760  mm.  pressure  weighs  1-29366 
grams.  100  cubic  inches  at  60°  F.  and  30  inches  barom.  weigh  30-935 
grains:  hence  a  cubic  foot  weighs  536-96  grains,  which  is  ^-^  of  the  weight 
of  a  cubic  foot  of  water  at  the  same  temperature. 

The  analysis  of  air  is  very  well  effected  by  passing  it  over  finely  divided 
copper  contained  in  a  tube  of  hard  glass,  carefully  weighed  and  then  heated 
to  redness:  the  nitrogen  is  suffered  to  flow  into  an  ex- 
hausted glass  globe,  also  previously  weighed.  The  in- 
crease of  weight  after  the  experiment  gives  the  informa- 
tion sought. 

An  easier,  but  less  accurate  method  consists  in  intro- 
ducing into  a  graduated  tube,  standing  over  water,  a 
known  quantity  of  the  air  to  be  examined,  and  then 
passing  into  the  latter  a  stick  of  phosphorus  affixed  to 
the  end  of  a  wire.  The  whole  is  left  about  twenty-four 
hours,  during  which  the  oxygen  is  slowly  but  completely 
absorbed,  after  which  the  phosphorus  is  withdrawn,  and 
the  residual  gas  read  off. 

Liebig  has  proposed  to  use  an  alkaline  solution  of  py- 
rogallic  acid  (a  substance  which  will  be  described  in  the 
department  of  organic  chemistry)  for  the  absorption  of 
oxygen.  The  absorptive  power  of  such  a  solution,  which 
turns  deep  black  on  coming  in  contact  with  the  oxygen,  is 
very  considerable.  Liebig's  method  combines  great  ac- 
curacy with  unusual  rapidity  and  facility  of  execution. 

Another  plan  is  to  mix  the  air  with  hydrogen  and  pass  an  electric  spark 
through  the  mixture:  after  explosion  the  volume  of  gas  is  read  off  and 
compared  with  that  of  the  air  employed.  Since  the  analysis  of  gaseous 
bodies  by  explosion  is  an  operation  of  great  importance  in  practical  chem- 
istry, it  may  be  worth  while  describing  the  process  in  detail,  as  it  is  appli- 
cable, with  certain  obvious  variations,  to  a  number  of  analogous  cases. 


156  NITROGEN. 

A  convenient  form  of  apparatus  for  the  purpose,  when  great  accuracy 
is  not  required,  is  the  syphon  eudiometer  of  Dr.  Ure :   this  consists  of  a 
stout  glass  tube,  having  an  internal  diameter  of  about 
Fig.  114.  one  third  of  an  inch,  closed  at  one  end,  and  bent  into 

the  form  represented  in  fig.  114.  Two  pieces  of 
platinum  wire,  melted  into  the  glass  near  the  closed 
extremity,  serve  to  give  passage  to  the  spark.  The 
closed  limb  is  carefully  graduated.  When  required 
for  use,  the  instrument  is  filled  with  mercury,  and 
inverted  in  a  vessel  of  the  same  liquid.  A  quantity 
of  the  air  to  be  examined  is  then  introduced,  the 
manipulation  being  precisely  the  same  as  with  expe- 
riments over  water;  the  open  end  is  stopped  with 
the  thumb,  and  the  air  transferred  to  the  closed  ex- 
tremity. The  instrument  is  next  held  upright,  and 
after  the  level  of  the  mercury  has  been  made  equal 
on  both  sides  by  displacing  a  portion  from  the  open 
limb  by  thrusting  down  a  piece  of  stick,  the  volume 
of  air  is  read  off.  This  done,  the  open  part  of  the 
tube  is  again  filled  up  with  mercury,  closed  with  the 
finger,  inverted  into  the  liquid  metal,  and  a  quantity 
of  pure  hydrogen  introduced,  equal,  as  nearly  as  can 
be  guessed,  to  about  half  the  volume  of  the  air.  The  eudiometer  is  once 
more  brought  into  the  erect  position,  the  level  of  the  mercury  equalized, 
and  the  volume  again  read  off;  the  quantity  of  hydrogen  added  is  thus 
accurately  ascertained.  All  is  now  ready  for  the  explosion;  the  instrument 
is  held  in  the  way  represented,  the  open  end  being  firmly  closed  by  the 
thumb,  while  the  knuckle  of  the  fore-finger  touches  the  nearer  platinum 
wire;  the  spark  is  then  passed  by  the  aid  of  a  charged  jar  or  a  good  elec- 
trophorus,  and  the  explosion  ensues.  The  air  confined  by  the  thumb  in 
the  open  part  of  the  tube  acts  as  a  spring  and  moderates  the  explosive 
effect.  Nothing  now  remains  but  to  equalize  the  level  of  the  mercury  by 
pouring  a  little  more  into  the  instrument,  and  then  to  read  off  the  volume 
for  the  last  time. 

What  is  required  to  be  known  from  this  experiment  is  the  diminution  the 
mixture  suffers  by  explosion ;  for  since  the  hydrogen  is  in  excess,  and  since 
that  body  unites  with  oxygen  in  the  proportion  by  measure  of  two  to  one, 
one-third  part  of  that  diminution  must  be  due  to  the  oxygen  contained  in 
the  air  introduced.  As  the  amount  of  the  latter  is  known,  the  proportion 
of  oxygen  it  contains  thus  admits  of  determination.  The  case  supposed 
will  render  this  clear. 

Air  introduced 100  measures. 

Air  and  hydrogen    .         .         .         .         .         150 
Volume  after  explosion         ....      87 

Diminution       ......  63 

63 

—  —  21 ;  oxygen  in  the  hundred  measures. 
3 

The  syphon  eudiometer  in  the  simple  form  above  described  is  not  well 
adapted  for  accurate  analysis,  especially  when,  as  in  the  analysis  of  many 
gaseous  mixtures,  caustic  potash  and  other  re-agents  have  to  be  introduced 
into  the  closed  limb,  to  absorb  some  of  the  components  of  the  mixture,  or 
of  the  products  resulting  from  the  explosion;  but  it  forms  the  essential 
part  of  the  more  exact  and  complex  forms  of  eudiometer  devised  by  Reg- 


NITROGEN. 


157 


Fig.  115. 


n.'iult,  and  by  Frankland  and  Ward,  in  which  provision  is  made  for  accu- 
rately adjusting  the  level  of  the  mercury,  and  for  quickly  transferring  the 
gas  to  another  tube  in  which  it  may  be  subjected  to  the  action  of  absorbing 
agents,  and  then  returning  it  to  the  syphon  tube  for  measurement.* 

The  simplest,  and,  on  the  whole,  the  most  convenient  form  of  eudiometer 
consists  of  a  straight  graduated  glass  tube  (fig.  115)  closed  at  the  top,  and 
having  platinum  wires  inserted  near  the  closed  end.  This  tube  is  filled 
with  mercury,  and  inverted  in  a  mercurial  pneumatic  trough. 

A  quantity  of  air,  sufficient  to  fill  about  one  sixth  of  the  tube,  is  then  in- 
troduced, and  its  volume  accurately  as- 
certained by  reading  off  with  a  telescope 
the  number  of  divisions  on  the  tube  to 
which  the  mercury  reaches,  whilst  the 
height  of  the  column  of  mercury  in  the 
tube  above  the  trough,  together  with 
that  of  the  barometer,  and  the  tempera- 
ture of  the  air,  are  also  read  off.  A 
quantity  of  pure  hydrogen  gas  is  now 
added,  more  than  sufficient  to  unite  with 
all  the  oxygen  present;  and  the  volume 
of  the  gas  and  the  pressure  exerted  upon 
it,  are  then  determined  as  before.  An 
electric  spark  is  npw  passed  through 
the  mixture,  care  being  taken  to  prevent 
any  escape,  by  pressing  the  open  end  of 
the  eudiometer  against  a  piece  of  sheet 
caoutchouc  under  the  mercury  in  the 
trough.  After  the  explosion,  the  volume 
is  again  determined  as  before,  and  is 
found  to  be  less  than  that  before  the  ex- 
plosion. 

One  third  of  the  diminution  gives,  as  already  explained,  the  volume  of 
oxygen  contained  in  the  air  taken  for  analysis. 

Compounds  of  Nitrogen  and  Oxygen. 

There  are  five  distinct  compounds  of  nitrogen  and  oxygen,  thus  named 
and  constituted :  — 

Composition. 


Nitrogen  monoxide  f 

Nitrogen  dioxide 

Nitrogen  trioxide,  or  Nitrous  oxide . 

Nitrogen  tetroxide 

Nitrogen  pentoxide,  or  Nitric  oxide  . 


By  weight.  By  volume. 
Nitrogen.    Oxygen.    Nitrogen.    Oxygen. 

28  .  16  2.1 

.  28  .  32  2.2 

28  .  48  2.3 

.  28  .  64  2.4 

28     ,     80  2.5 


A  comparison  of  these  numbers  Vill  show  that  the  quantities  of  oxygen 
which  unite  with  a  given  quantity  of  nitrogen  are  to  one  another  in  the 
ratio  of  the  numbers  1,  2,  3,  4,  5. 

See  the  article  "  Analysis  of  Gases,"  by  Dr.  Russell,  in  Watts's  "  Dictionary  of  Chemistry," 


f  In  symbols  the  composition  of  these  bodies  is  thus  expressed:  — 
Nitrogen  monoxide       .         .        .        N2O 
Nitrogen  dioxide       ....     N202  or  NO 
Nitrogen  trioxide  .        .        .        N2O3 

Nitrogen  tetroxide    ....    N2'»4orN02 
Nitrogen  pentoxide       .        .        .        N205. 


158  NITROGEN. 

The  third  and  fifth  of  the  compounds  in  the  table  are  capable  of  taking 
up  the  elements  of  water  and  of  metallic  oxides  to  form  salts  (p.  133),  called 
respectively  nitrites  and  nitrates,  the  hydrogen  salts  being  also  called  nitrous 
and  nitric  acid.*  The  other  three  nitrogen  oxides  do  not  form  salts.  It  will 
be  convenient  to  commence  the  description  of  these  compounds  with  the 
last  on  the  list,  viz.,  the  pentoxide,  as  its  salts,  the  nitrates,  are  the  sources 
from  which  all  the  other  compounds  in  the  series  are  obtained. 

NITROGEN  PENTOXIDE  or  NITRIC  OXIDE  (also  called  Anhydrous  Nitric  Acid 
OT  Nitric  Anhydride]. — This  compound  was  discovered  in  1849  by  Deville, 
who  obtained  it  by  exposing  silver  nitrate,  which  may  be  regarded  as  a 
compound  of  nitrogen  pentoxide  with  silver  and  oxygen,  to  the  action  of 
chlorine  gas.  Chlorine  and  silver  then  combine,  forming  silver  chloride, 
which  remains  in  the  apparatus,  while  oxygen  and  nitrogen  pentoxide 
separate. •}•  The  latter  is  a  colorless  substance,  crystallizing  in  six-sided 
prisms,  which  melt  at  30°  and  boil  between  45°  and  50°,  when  they  begin 
to  decompose.  Nitrogen  pentoxide  sometimes  explodes  spontaneously.  It 
dissolves  in  water  with  great  rise  of  temperature,  forming  hydrogen  nitrate 
or  nitric  acid. 

NITRATES  —  NITRIC  ACID. — In  certain  parts  of  India,  and  in  other  hot 
dry  climates  where  rain  is  rare,  the  surface  of  the  soil  is  occasionally  covered 
by  a  saline  efflorescence,  like  that  sometimes  apparent  on  newly  plastered 
walls :  this  substance  collected,  dissolved  in  hot  water,  and  crystallized  from 
the  filtered  solution,  furnishes  the  highly  important  salt  known  in  commerce 
as  nitre  or  saltpetre,  and  consisting  of  potassium  nitrate.  To  obtain  nitric 
acid,  equal  weights  of  powdered  nitre  and  strong  sulphuric  acid  are  in- 
troduced into  a  glass  retort,  and  heat  is  applied  by  means  of  an  Argand  gas- 
lamp  or  charcoal  chauffer,  (see  fig.  38).  A  flask,  cooled  by  a  wet  cloth,  is 
adapted  to  the  retort  to  serve  for  a  receiver.  No  luting  of  any  kind  must 
be  used. 

As  the  distillation  advances,  the  red  fumes  which  first  arise  disappear, 
but  towards  the  end  of  the  process  they  again  become  manifest.  When 
this  happens,  and  very  little  liquid  passes  over,  while  the  greater  part  of 
the  saline  matter  of  the  retort  is  in  a  state  of  tranquil  fusion,  the  opera- 
tion may  be  stopped;  and  when  the  retort  is  quite  cold,  water  maybe 
introduced  to  dissolve  out  the  saline  residue.  The  reaction  consists  in  an 
interchange  between  the  potassium  of  the  nitre  and  half  the  hydrogen  of 
the  sulphuric  acid  (hydrogen  sulphate),  whereby  there  are  formed  hydro- 
gen nitrate  which  distils  over,  and  hydrogen  and  potassium  sulphate 
which  remains  in  the  retort.  J 

In  the  manufacture  of  nitric  ac.id  on  the  large  scale,  the  glass  retort  is 
replaced  by  a  cast-iron  cylinder,  and  the  receiver  by  a  series  of  earthen 
condensing  vessels  connected  by  tubes.  Sodium  nitrate,  found  native  in 
Peru,  is  now  generally  substituted  for  potassium  nitrate. 

Nitric  acid  thus  obtained  has  a  specific  gravity  of  from  15  to  1-52;  it 
has  a  golden-yellow  color,  due  to  nitr.ogen  trioxide,  or  tetroxide,  which 
is  held  in  solution,  and,  when  the  acid  is  diluted  with  water,  gives  rise  by 
its  decomposition  to  a  disengagement  of  nitric  oxide.  Nitric  acid  is  ex- 

*  Hydrogen  nitrate,  or  Nitrous  acid    ....        N203.OH2  or  NOH2 

Potassium  nitrate N2O3.OK2  or  NOK2 

Hydrogen  nitrate,  or  Nitric  acid       ....        N2O5.OII2or  N03H 

Potassium  nitrite N205.OK2  or  N03K. 

t  N03Ag  +  Cla  =  2AgCl  +  0  +  N205. 

j        N03K        +        S04H2        =        N03H        +  S04HK 

Potassium  Hydrogen  Hydrogen  Hydrogen  and  po- 

nitrate.  sulphate.  nitrate.  tassium  sulphate. 


NITROGEN.  159 

coedingly  corrosive,  staining  the  skin  deep  yellow,  and  causing  total  dis- 
organization. Poured  upon  red-hot  powdered  charcoal,  it  causes  brilliant 
combustion;  and  when  added  to  warm  oil  of  turpentine,  acts  upon  that 
substance  so  energetically  as  to  set  it  on  fire. 

Pure  nitric  acid,  in  its  most  concentrated  form,  is  obtained  by  mixing 
the  above  with  about  an  equal  quantity  of  strong  sulphuric  acid,  redistil- 
ling, collecting  apart  the  first  portion  which  conies  over,  and  exposing  it 
in  a  vessel  slightly  warmed  and  sheltered  from  the  light,  to  a  current  of 
dry  air  made  to  bubble  through  it,  which  completely  removes  the  nitrous 
acid.  In  this  state  the  product  is  as  colorless  as  water:  it  has  the  sp.  gr. 
1-517  at  15-5°  (60°  F.),  boils  at  84-5°  (184°  F.),  and  consists  of  54  parts 
nitrogen  pentoxide  and  9  parts  water.  Although  nitric  acid  in  a  more 
dilute  form  acts  very  violently  upon  many  metals,  and  upon  organic  sub- 
stances generally,  this  is  not  the  case  with  the  most  concentrated  acid: 
even  at  a  boiling  heat,  it  refuses  to  attack  iron  or  tin;  and  its  mode  of 
action  on  lignin,  starch,  and  similar  substances  is  quite  peculiar  and  very 
much  less  energetic  than  that  of  an  acid  containing  more  water. 

On  boiling  nitric  acid  of  different  degrees  of  concentration,  at  the  ordi- 
nary atmospheric  pressure,  a  residue  is  left,  boiling  at  120/5°  and  29  inches 
barometer,  and  Laving  the  sp.  gr.  1-414  at  15-5°.  This  acid  was  formerly 
supposed  to  be  a  definite  compound  of  nitric  acid  with  water;  but  Roscoe 
has  recently  proved  this  assumption  to  be  incorrect,  the  composition  of  the 
acid  varying  according  to  the  pressure  under  which  the  liquid  boils. 

The  nitrates  form  a  very  extensive  and  important  group  of  salts,  which 
are  remarkable  for  being  all  soluble  in  water.  Hydrogen  nitrate  is  of 
great  use  in  the  laboratory,  and  also  in  many  branches  of  industry. 

The  acid  prepared  in  the  way  described  is  apt  to  contain  traces  of 
chlorine  from  common  salt  in  the  nitre,  and  sometimes  of  sulphate  from 
accidental  splashing  of  the  pasty  mass  in  the  retort.  To  discover  these 
impurities,  a  portion  is  diluted  with  four  or  five  times  its  bulk  of  distilled 
water,  and  divided  between  two  glasses.  Solution  of  silver  nitrate  is 
dropped  into  the  one,  and  solution  of  barium  nitrate  into  the  other;  if  no 
change  ensue  in  either  case,  the  acid  is  free  from  the  impurities  men- 
tioned. 

Nitric  acid  has  been  formed  in  small  quantity  by  a  very  curious  process, 
namely,  by  passing  a  series  of  electric  sparks  through  a  portion  of  air 
in'  contact  with  water  or  an  alkaline  solution.  The  amount  of  acid  so 
formed  after  many  hours  is  very  minute;  still  it  is  not  impossible  that 
powerful  discharges  of  atmospheric  electricity  may  sometimes  occasion 
a  trifling  production  of  nitric  acid  in  the  air.  A  very  minute  quantity  of 
nitric  acid  is  also  produced  by  the  combustion  of  hydrogen  and  other  sub- 
stances in  the  atmosphere ;  it  is  also  formed  by  the  oxidation  of  ammonia. 

Nitric  acid  is  not  so  easily  detected  in  solution  in  small  quantities  as 
many  other  acids.  Owing  to  the  solubility  of  all  its  compounds,  no  precip- 
itant can  be  found  for  this  substance.  An  excellent  mode  of  testing  it  is 
based  upon  its  power  of  bleaching  a  solution  of  indigo  in  sulphuric  acid 
when  boiled  with  that  liquid.  The  absence  of  chlorine  must  be  insured 
in  this  experiment  by  means  which  will  hereafter  be  described:  otherwise 
the  result  is  equivocal. 

The  best  method  for  the  detection  of  nitric  acid  is  the  following.  Tho 
substance  to  be  examined  is  boiled  with  a  small  quantity  of  water,  and 
the  solution  cautiously  mixed  with  an  equal  volume  of  concentrated  sul- 
phuric acid;  the  liquid  is  then  allowed  to  cool,  and  a  strong  solution  of 
ferrous  sulphate  carefully  poured  upon  it,  so  as  to  form  a  separate  layer. 
If  large  quantities  of  nitric  acid  are  present,  the  surface  of  contact,  first, 
and  then  the  whole  of  the  liquid,  becomes  black.  If  but  small  quantities 
of  nitric  acid  are  present,  the  liquid  becomes  reddish-brown  or  purple. 


100  NITROGEN. 

The  ferrous  sulphate  reduces  the  nitric  acid  to  nitrogen  dioxide,  which, 
dissolving  in  the  solution  of  ferrous  sulphate,  imparts  to  it  a  dark  color. 

NITROGEN  MONOXIDE  (sometimes  called  Nitrous   Oxide;   also   Laughing- 
Gas}. —  When  solid  ammonium  nitrate  is  heated  in  a  retort  or  flask,*  fig. 
116,   furnished  with  a  perforated  cork  and  bent 
-  H6.  tube,  it  is  resolved  into  water  and  nitrogen  mon- 

oxide.f 

No  particufar  precaution  is  required  in  the 
operation,  save  due  regulation  of  the  heat,  and 
the  avoidance  of  tumultuous  disengagement  of 
the  gas. 

Nitrogen  monoxide  is  a  colorless,  transparent, 
and  almost  inodorous  gas,  of  distinctly  sweet  taste. 
Its  specific  gravity  is  1-525;  a  litre  of  it  weighs 
0-97172  grams ;  100  cubic  inches  weigh  47-29  grains. 
It  supports  the  combustion  of  a  taper  or  a  piece  of 
phosphorus  with  almost  as  much  energy  as  pure 
oxygen :  it  is  easily  distinguished,  however,  from 
that  gas  by  its  solubility  in  cold  water,  which  dis- 
solves nearly  its  own  volume  :  hence  it  is  necessary 
to  use  tepid  water  in  the  pneumatic  trough  or  gas- 
holder; otherwise  great  loss  of  gas  will  ensue. 
Nitrous  oxide  has  been  liquefied,  but  with  diffi- 
culty: it  requires,  at  7-2°  C.  (45°  F.),  a  pressure 
of  50  atmospheres :  the  liquid,  when  exposed  under  the  bell-glass  of  the 
air-pump,  is  rapidly  converted  into  a  snow-like  solid.  When  mixed  with 
an  equal  volume  of  hydrogen,  and  fired  by  the  electric  spark  in  the  eudi- 
ometer, it  explodes  with  violence,  and  liberates  its  own  measure  of  nitrogen. 
Every  two  volumes  of  the  gas  must  consequently  contain  two  volumes  of 
nitrogen  and  one  volume  of  oxygen,  the  whole  being  condensed  or  con- 
tracted one  third  —  a  constitution  resembling  that  of  vapor  of  water. 

The  most  remarkable  property  of  this  gas  is  its  intoxicating  power  iipon 
the  animal  system.  If  quite  pure,  or  merely  mixed  with  atmospheric  air, 
it  may  be  respired  for  a  short  time  without  danger  or  inconvenience.  The 
effect  is  very  transient,  and  is  not  followed  by  depression. 

NITROGEN  DIOXIDE  (sometimes  called  Nitric  Oxide). — Clippings  or  turn- 
ings of  copper  are  put  into  the  apparatus  employed  for  preparing  hydrogen 
(p.  137),  together  with  a  little  water,  and  nitric  acid  is  added  by  the  funnel 
until  brisk  effervescence  is  excited.  The  gas  may  be  collected  over  cold 
water,  as  it  is  not  sensibly  soluble. 

The  reaction  is  a  simple  deoxidation  of  some  of  the  nitric  acid  by  the 
copper:  the  metal  is  oxidized,  and  the  oxide  so  formed  is  dissolved  by  an- 
other portion  of  the  acid.  Nitric  acid  is  very  prone  to  act  thus  upon 
certain  metals.  J 

The  gas  obtained  in  this  manner  is  colorless  and  transparent:  in  contact 
with  air  or  oxygen  gas  it  produces  deep  red  fumes,  which  are  readily  ab- 
sorbed by  water:  this  character  is  sufficient  to  distinguish  it  from  all  other 

*  Florence  oil-flnsks,  which  may  be  purchased  at  a  very  trifling  sum,  constitute  exceedingly 
useful  vessels  lor  chemical  purposes,  and  often  supersede  retorts  or  other  expensive  apparatus. 
They  are  rendered  still  more  valuable  by  cutting  the  neck  smoothly  round  with  a  hot  iron, 
Foftening  it  in  the  flame  of  a  good  Argand  gas-lamp,  and  then  turning  over  the  edge  so  as  to 
form  a  lip,  or  border.  The  neck  will  then  bear  a  tightly  fitting  cork  without  risk  of  splitting. 
f  N03NII4  =  OII2  +  N20 

Ammonium  Water.  Nitrogen 

nitrate.  monoxide. 

%       8N03H     +        Cu3      =  N202  +        3(N08y3n        +     4H20 

Nitric  acid.          Copper.        Nitrogen  dioxide.        Copper  nitrate.         Water. 


NITROGEN.  161 

gaseous  bodies.     A  lighted  taper  plunged  into   the  gas  is  extinguished; 
lighted  phosphorus,  however,  burns  in  it  with  great  brilliancy. 

The  specific  gravity  of  nitrogen  dioxide  is  1-039;  a  litre  weighs  1-34343 
grams.  It  contains  equal  measures  of  oxygen  and  nitrogen  gases  united 
without  condensation.  When  this  gas  is  passed  into  the  solution  of  a  fer- 
rous salt,  it  is  absorbed  in  large  quantity,  and  a  deep-brown  or  nearly  black 
liquid  produced,  which  seems  to  be  a  definite  compound  of  the  two  sub- 
stances (p.  159).  The  compound  is  again  decomposed  by  boiling. 

NITROGEN  TRIOXIDE,  or  NITROUS  OXIDE. — When  four  measures  of  ni- 
trogen dioxide  are  mixed  with  one  measure  of  oxygen,  and  the  gases,  per- 
fectly dry,  are  exposed  to  a  temperature  of  — 18°,  they  condense  to  a  thin 
mobile  blue  liquid,  which  emits  orange-red  vapors. 

Nitrous  oxide,  sufficiently  pure  for  most  purposes,  is  obtained  by  pouring 
concentrated  nitric  acid  on  lumps  of  arsenious  acid,  and  gently  warming 
the  mixture,  in  order  to  start  the  reaction.  Nitrous  oxide  is  then  evolved 
as  an  orange-red  gas,  arsenic  acid  remaining  behind. 

Nitrous  oxide  is  decomposed  by  water,  being  converted  into  nitric  acid 
and  nitrogen  dioxide.*  For  this  reason  it  cannot  be  made  to  unite  directly 
with  metallic  oxides;  potassium  nitrite  may,  however,  be  prepared  by 
fusing  potassium  nitrate,  whereby  part  of  its  oxygen  is  driven  off;  and 
many  other  salts  of  nitrous  acid  may  be  obtained  by  indirect  means.  Thus 
a  solution  of  potassium  or  sodium  nitrite  may  be  prepared  by  passing  the 
vapor  of  nitrogen  trioxide,  obtained  as  above  by  heating  nitric  acid  with 
arsenious  acid  (or  with  starch),  into  a  solution  of  caustic  potash  or  soda. 

NITROGEN  TETROXIDE  (also  called  Nitric  Peroxide}.  —  This  is  the  principal 
constituent  of  the  deep-red  fumes  always  produced  when  nitrogen  dioxide 
escapes  into  the  air. 

When  carefully  dried  lead  nitrate  is  exposed  to  heat  in  a  retort  of  hard 
glass,  it  is  decomposed,  lead  oxide  remaining  behind,  while  a  mixture  of 
oxygen  and  nitrogen  tetroxide  is  evolved.  By  surrounding  the  receiver 
with  a  very  powerful  freezing  mixture,  the  latter  is  condensed  in  trans- 
parent crystals,  or  if  the  slightest  trace  of  moisture  is  present,  as  a  color- 
less liquid,  which  acquires  a  yellow  and  ultimately  a  red  tint,  as  the  tem- 
perature rises.  At  27-8°  it  boils,  giving  off  its  well-known  red  vapor,  the 
intensity  of  the  color  of  which  is  greatly  augmented  by  elevation  of  tem- 
perature. Its  vapor  is  absorbed  by  strong  nitric  acid,  which  thereby  ac- 
quires a  yellow  or  red  tint,  passing  into  green,  then  into  blue,  and  after- 
wards disappearing  altogether  on  the  addition  of  successive  portions  of 
water.  The  deep-red  fuming  acid  of  commerce,  called  nitrous  acid,  is  simply 
nitric  acid  impregnated  Avith  nitrogen  tetroxide. 

Nitrogen  tetroxide  is  decomposed  by  water  at  very  low  temperatures  in 
such  a  manner  as  to  yield  nitric  and  nitrous  acid ;  f  but  when  added  to 
excess  of  water  at  ordinary  temperatures,  it  yields  nitric  acid,  and  the 
products  of  decomposition  of  nitrous  acid,  namely,  nitric  acid  and  nitrogen 
dioxide.  In  like  manner,  when  passed  into  alkaline  solutions,  it  forms  a 
nitrate  and  a  nitrite  of  the  alkali-metal;  but  it  has  been  also  supposed  to 
unite  directly,  under  certain  circumstances,  with  metallic  oxides  —  lead 
oxide,  for  example  —  forming  definite  crystalline  salts,  and  has  hence  been 
called  hyponitric  acid;  but  it  is  most  probable  that  these  salts  are  compounds 
of  nitrates  and  nitrites.  | 

*          3N203  +        OIL,     -        2N03II        +  2N«Oo 

Nitrogen  trioxide.         Water.         Nitric  acid.        Nitrogen  dioxide, 
t  N.,04  -f          Olio        =        NOjH        +        NO.JI 

Nitrogen  tetroxide.  Water.  Nitric  acid.          Nitrous  acid. 

I  E.g.,    2("Nn04-n>0)         -         (NO.y.,1'1)         +         (NO._,)oPh 

Lead  byponitrate.  Li-ad  nitrate.  Lead  nitrite. 

14* 


162  NITROGEN    AND    HYDROGEN;   AMMONIA. 

Nitrogen  appears  to  combine,  under  favorable  circumstances,  with  metals. 
When  iron  is  heated  to  redness  in  an  atmosphere  of  ammonia,  it  becomes 
brittle  and  crystalline,  and  shows  an  increase  in  weight,  said  to  vary  from 
6  to  12  per  cent.  ;  while,  according  to  other  observers,  the  physical  charac- 
ters of  the  metal  are  changed  without  sensible  alteration  of  weight.  By 
heating  copper  in  ammonia,  no  compound  of  nitrogen  with  copper  is  pro- 
duced. But  when  ammonia  is  passed  over  copper  oxide  heated  to  800°, 
water  is  formed,  and  a  soft  brown  powder  produced,  which,  when  heated 
further,  evolves  nitrogen,  and  leaves  metallic  copper.  The  same  effect  is 
produced  by  the  contact  of  strong  acids.  A  similar  compound  of  chromium 
with  nitrogen  appears  to  exist. 

NITROGEN  AND  HYDROGEN ;  AMMONIA. 

When  powdered  sal-ammoniac  is  mixed  with  moist  calcium  hydrate 
(slaked  lime),  and  gently  heated  in  a  glass  flask,  a  large  quantity  of  gas- 
eous matter  is  disengaged,  which  must  be  collected  over  mercury,  or  by 
displacement,  advantage  being  taken  of  its  low  specific  gravity. 

Ammonia  gas  thus  obtained  is  colorless ;  it  has  a  strong  pungent  odor, 
and  possesses  in  an  eminent  degree  those  properties  to  which  the  term 
alkaline  is  applied ;  that  is  to  say,  it  turns  the  yellow  color  of  turmeric  to 
brown,  that  of  reddened  litmus  to  blue,  and  combines  readily  with  acids, 
neutralizing  them  completely;  by  these  reactions  it  is  easily  distinguished 
from  all  other  bodies  possessing  the  same  physical  characters.  Under  a 
pressure  of  6-5  atmospheres  at  15-5°,  ammonia  condenses  to  the  liquid 
form.*  Water  dissolves  about  700  times  its  volume  of  this  gas,  forming 
a  solution  which  in  a  more  dilute  state  has  long  been  known  under  the 
name  of  liquor  ammonise;  by  heat,  a  great  part  is  again  expelled  j-  The 
solution  is  decomposed  by  chlorine,  sal-ammoniac  being  formed,  and  ni- 
trogen set  free. 

Ammonia  has  a  density  of  0-589;  a  litre  weighs  0-76271  grams.  It  can- 
not be  formed  by  the  direct  union  of  its  elements,  although  it  is  sometimes 
produced  under  rather  remarkable  circumstances  by  the  deoxidation  of 
nitric  acid.J  The  great  sources  of  ammonia  are  the  feebly  compounded 
azotised  principles  of  the  animal  and  vegetable  kingdoms,  which,  when  left 
to  putrefactive  change,  or  subjected  to  destructive  distillation,  almost  in- 
variably give  rise  to  an  abundant  production  of  this  substance. 

The  analysis  of  ammonia  gas  is  easily  effected.  When  a  portion  is  con- 
fined in  a  graduated  tube  over  mercury,  and  electric  sparks  passed  through 
it  for  a  considerable  time,  the  volume  of  the  gas  gradually  increases  until 
it  becomes  doubled.  On  examination,  the  tube  is  found  to  contain  a  mixture 
of  3  measures  of  hydrogen  gas  and  1  measure  of  nitrogen.  Every  two 
volumes  of  the  ammonia,  therefore,  contained  three  volumes  of  hydrogen 
and  one  of  nitrogen,  the  whole  being  condensed  to  the  extent  of  one  half. 
The  weight  of  the  two  constituents  is  in  the  proportion  of  3  parts  hydrogen 
to  14  parts  nitrogen,  g 

*  [At  the  temperature  of  — 75°  F..  liquid  ammonia  freezes  into  a  colorless  solid,  heavier  than 
the  liquid  itself  — (Faraday.)  —  K.  B.] 

t  A  concentrated  solution  of  ammonia  has  recently  been  applied  by  M.  Carr6  for  producing 
intense  cold  (for  the  manufacture  of  ice).  The  apparatus  used  for  this  purpose  consists  of  two 
strong  iron  cylinders  connected  by  tubes,  the  one  cylinder  containing  the  solution  of  am- 
monia, the  other  being  empty,  and  the  whole  apparatus  being  perfectly  air-tight.  The  empty 
cylinder  is  now  cooled  with* water,  and  the  other  cylinder  is  gently  warmed.  The  ammonia 
escapes  from  the  solution,  and  is  condensed  by  its  own  pressure  in  the  cooled  cylinder.  If  the 
source  of  heat  be  now  removed,  the  liquefied  ammonia  is  again  absorbed  by  the  water,  and  the 
heat  necessary  for  its  transformation  into  vapor  being  taken  from  the  iron  vessel,  the  water 
eurrounding  it  is  converted  into  ice:  by  this  process  the  temperature  may  be  reduced  to  — 15° 
C.  (+  5°  F.) 

J  A  mode  of  converting  the  nitrogen  of  the  atmosphere  into  ammonia,  by  a  succession  of 
chemical  operations,  will  be  found  under  the  head  of  Cyanogen. 

§  The  formula  of  ammonia  is  NH3. 


CARBON.  163 

Ammonia  may  also  be  decomposed  into  its  elements  by  transmission 
through  a  red-hot  tube. 

Solution  of  ammonia  is  a  very  valuable  reagent,  and  is  employed  in  a 
great  number  of  chemical  operations,  for  some  of  which  it  is  necessary  to 
have  it  perfectly  pure.  The  best  mode  of  preparation  is  the  following: 

Equal  weights  of  sal-ammoniac  and  quicklime  are  taken  ;  the  lime  is 
slaked  in  a  covered  basin,  and  the  salt  reduced  to  powder.  These  are  mixed 
and  introduced  into  the  flask  employed  in  preparing  solution  of  hydrochloric 
acid,*  together  with  just  enough  water  to  damp  the  mixture,  and  cause  it 
to  aggregate  into  lumps ;  the  rest  of  the  apparatus  is  arranged  exactly  as 
in  the  former  case,  with  an  ounce  or  two  of  water  in  the  wash-bottle,  or 
enough  to  cover  the  ends  of  the  tubes,  and  the  gas  conducted  afterwards 
into  pure  distilled  water,  artificially  cooled  as  before.  The  cork  joints  are 
made  tight  with  wax ;  a  little  mercury  is  put  into  the  safety-funnel,  heat 
cautiously  applied  to  the  flask,  and  the  whole  left  to  itself.  The  disen- 
gagement of  ammonia  is  very  regular  and  uniform.  Calcium  chloride, 
with  excess  of  calcium  hydrate  (slaked  lime),  remains  in  the  flask. 

The  decomposition  of  the  salt  may  be  represented  in  the  manner  shown 
by  the  following  diagram : 

(  Ammonia  —  Ammonia. 

Sal-ammoniac  <  Hydrochloric)  Hydrogen ^^*~  Water. 

(       acid  .     .      )  Chlorine. 


T .  f    Oxygen ^*\^^       f  Calcium 

{    Calcium  — ^  j  chloridc.f 

Solution  of  ammonia  should  be  perfectly  colorless,  leave  no  residue  on 
evaporation,  and  when  supersaturated  by  nitric  acid,  give  no  cloud  or  mud- 
diness  with  silver  nitrate.  Its  density  diminishes  with  its  strength,  that  of 
the  most  concentrated  being  about  0'875 ;  the  value  in  alkali  of  any  sample 
of  liquor  ammonia)  is  most  safely  inferred,  not  from  a  knowledge  of  its 
density,  but  from  the  quantity  of  acid  a  given  amount  will  saturate.  The 
mode  of  conducting  this  experiment  will  be  found  described  under  Alka- 
limetry. 

When  solution  of  ammonia  is  mixed  with  acids  of  various  kinds,  salts  are 
generated,  which  resemble  in  the  most  complete  manner  the  corresponding 
potassium  and  sodium  compounds:  these  are  best  discussed  in  connection 
with  the  latter. \  Any  ammoniacal  salt  can  at  once  be  recognized  by  the 
evolution  of  ammonia  which  takes  place  when  it  is  heated  with  slaked  lime, 
or  solution  of  potash  or  soda. 


CARBON. 

This  substance  occurs  in  a  state  of  purity,  and  crystallized,  in  two  distinct 
and  very  dissimilar  forms  —  namely,  as  diamond,  and  as  graphite  or  plum- 

*  See  fig.  132,  p.  182. 

f        2NII4C1          +        CaO        =        2Nir3  -f-        CaCl2        +        H.,0 

Sill-ammoniac.  Limo  Ammonia.  Calcium  Water. 

chloride. 

t  The  ammonia  salts  may  be  regarded  either  as  direct  compounds  of  ammonia,  NII3,  with 
acids  (IICI.  fur  example),  or  as  resulting  from  the  replacement  of  the  hydrogen  of  an  acid  by 
the  group  NH4.  called  timmtmiitni,  which  in  this  sense  is  a  compound  metal,  chemically  equiv- 
alent to  potassium,  sodium,  silver,  etc.  Thus: 

Ammonia  bydroehlorate  NIT3.TrCl  =         NTT4.C1  Ammoniujn  chloride. 

"        nitrate  NHo.HNO,        =         NIT4.\03  "          nitrite. 

sulphate        (NI^-HoSC^       =      (NII4)2.S04         "          sulphate. 

The  formula;  in  the  second  column  arc  exactly  analogous  to  those  of  the  potassium  salts, 
KCK  KN03,  K2S04. 


164: 


CARBON. 


bago.  It  constitutes  a  large  proportion  of  all  organic  structures,  animal 
and  vegetable :  when  these  latter  are  exposed  to  destructive  distillation  in 
close  vessels,  a  great  part  of  their  carbon  remains,  obstinately  retaining 
some  of  the  hydrogen  and  oxygen,  and  associated  with  the  earthy  and  alka- 
line matter  of  the  tissue,  giving  rise  to  the  many  varieties  of  charcoal,  coke, 
etc.  This  residue,  when  perfectly  separated  from  all  foreign  matter,  con- 
stitutes a  third  variety  of  carbon. 

The  diamond  is  one  of  the  most  remarkable  substances  known :  long 
prized  on  account  of  its  brilliancy  as  an  ornamental  gem,  the  discovery  of 
its  curious  chemical  nature  confers  upon  it  a  high  degree  of  scientific  in- 
terest. Several  localities  in  India,  the  island  of  Borneo,  and  more  espe- 
cially Brazil,  furnish  this  beautiful  substance.  It  is  always  distinctly  crys- 
tallized, often  quite  transparent  and  colorless,  but  now  and  then  having  a 
shade  of  yellow,  pink,  or  blue.  The  origin  and  true  geological  position  of 
the  diamond  are  unknown ;  it  is  always  found  embedded  in  gravel  and 
transported  materials  whgse  history  cannot  be  traced.  The  crystalline 
form  of  the  diamond  is  that  of  the  regular  octohedron  or  cube,  or  some  fig- 
ure geometrically  connected  with  these.  Many  of  the  octohedral  crystals 
exhibit  a  very  peculiar  appearance,  arising  from  the  faces  being  curved  or 
rounded,  which  gives  to  the  crystal  an  almost  spherical  figure. 

The  diamond  is  infusible  and  unalterable  even  by  a  very  intense  heat, 
provided  air  be  excluded ;  but  when  heated,  thus  protected,  between  the 
poles  of  a  strong  galvanic  battery,  it  is  converted  into  coke  or  graphite ; 
heated  to  whiteness  in  a  vessel  of  oxygen,  it  burns  with  facility,  yielding 
carbonic  acid  gas. 

Fig.  117. 


The  diamond  is  the  hardest  substance  known :  it  admits  of  being  split  or 
cloven  without  difficulty  in  certain  particular  directions,  but  can  only  be 
cut  or  abraded  by  a  second  portion  of  the  same  material ;  the  powder  rubbed 
off  in  this  process  serves  for  polishing  the  new  faces,  and  is  also  highly  use- 
ful to  the  lapidary  and  seal-engraver.  One  very  curious  and  useful  appli- 
cation of  the  diamond  is  made  by  the  glazier:  a  fragment  of  this  mineral, 
like  a  bit  of  flint,  or  any  other  hard  substance,  scratches  the  surface  of  the 
glass ;  a  crystal  of  diamond  having  the  rounded  octohedral  figure  spoken  of, 
held  in  one  particular  position  on  the  glass  —  namely,  with  an  edge  formed 
by  the  meeting  of  two  adjacent  faces  presented  to  the  surface  —  and  then 
drawn  along  with  gentle  pressure,  causes  a  split  or  cut,  which  penetrates 
to  a  considerable  depth  into  the  glass,  and  determines  its  fracture  with  per- 
fect certainty. 

Graphite  or  plumbago  appears  to  consist  essentially  of  pure  carbon,  al- 
though most  specimens  contain  iron,  the  quantity  of  which  varies  from  a 
mere  trace  up  to  five  per  cent.  Graphite  is  a  somewhat  rare  mineral :  the 
finest  and  most  valuable  for  pencils  is  brought  from  Borrowdale,  in  Cumber- 
land, where  a  kind  of  irregular  vein  is  found  traversing  the  ancient  slate 
beds  of  that  district.*  Crystals  are  not  common :  when  they  occur,  they 

*  The  graphite  which  can  be  directly  cut  for  pencils  occurring  only  in  limited  quantity, 
powdered  graphite,  obtained  from  the  inferior  varieties  of  the  mineral,  is  now  frequently 
consolidated  lor  this  purpose.  The  mechanical  division  of  graphite  presents  considerable 


CARBON.  165 

have  the  figure  of  a  short  six-sided  prism  —  a  form  bearing  no  geometric 
relation  to  that  of  the  diamond. 

Graphite  is  often  formed  artificially  in  certain  metallurgic  operations: 
the  brilliant  scales  which  sometimes  separate  from  melted  cast-iron  on 
cooling,  called  by  the  workmen  "kish,"  consist  of  graphite. 

Lampblack,  the  soot  produced  by  the  imperfect  combustion  of  oil  or 
resin,  is  the  best  example  that  can  be  given  of  carbon  in  its  uncrystallized 
or  amorphous  state.  To  the  same  class  belong  the  different  kinds  of  char- 
coal. That  prepared  from  wood,  either  by  distillation  in  a  large  iron  retort, 
or  by  the  smothered  combustion  of  a  pile  of  fagots  partially  covered  with 
earth,  is  the  most  valuable  as  fuel.  Coke,  the  charcoal  of  pit-coal,  is  much 
more  impure ;  it  contains  a  large  quantity  of  earthy  matter,  and  very  often 
sulphur,  the  quality  depending  very  much  upon  the  mode  of  .preparation. 
Charcoal  from  bones  and  animal  matters  in  general  is  a  very  valuable  sub- 
stance, on  account  of  the  extraordinary  power  it  possesses  of  removing 
coloring  matters  from  organic  solutions;  it  is  used  for  this  purpose  by  the 
sugar-refiners  to  a  very  great  extent,  and  also  by  the  manufacturing  and 
scientific  chemist.  The  property  in  question  is  possessed  by  all  kinds  of 
charcoal  in  a  small  degree. 

Charcoal  made  from  box,  or  other  dense  wood,  has  the  property  of  con- 
densing gases  and  vapors  into  its  pores:  of  ammoniacal  gas  it  is  said  to 
absorb  not  less  than  ninety  times  its  volume,  while  of  hydrogen  it  takes  up 
less  than  twice  its  own  bulk,  the  quantity  being  apparently  connected  with 
the  property  in  the  gas  of  suffering  liquefaction.  This  property  of  absorb- 
ing gases,  as  well  as  the  decolorizing  power,  no  doubt  depends  in  some  way 
upon  the  same  peculiar  action  of  surface  so  remarkable  in  the  case  of  pla- 
tinum in  a  mixture  of  oxygen  and  hydrogen.  The  absorbing  power  is,  in- 
deed, considerably  increased  by  saturating  charcoal  with  solution  of  pla- 
tinum, and  subsequently  igniting  it,  so  as  to  coat  the  charcoal  with  a  thin 
film  of  platinum.  Dr.  Stenhouse,  who  suggested  this  plan,  finds  that  the 
gases  thus  absorbed  undergo  a  kind  of  oxidation  within  the  pores  of  the 
charcoal.* 

Compounds  of  Carbon  and  Oxygen, 
There   are   two   direct   inorganic   compounds   of    carbon    and    oxygen 

difficulties,  which  may  be  entirely  obviated  by  adopting  a  chemical  process  suggested  by  Sir 
Benjamin  Brodie,  applicable,  however,  only  to  certain  varieties,  such  as  Ceylon  graphite.  This 
process  consists  in  introducing  the  coarsely  powdered  graphite,  previously  mixed  with  ^  of 
its  weight  of  potassium  chlorate,  into  2  parts  of  concentrated  sulphuric  acid,  which  is  heated 
in  a  water-bath  until  tlie  evolution  of  acid  fumes  ceases.  The  acid  is  then  removed  by  water, 
and  the  graphite  dried.  Thus  prepared,  this  substance,  when  heated  to  a  temperature  ap- 
proaching a  red  heat,  swells  up  to  a  bulky  mass  of  finely  divided  graphite.  The. graphite 
lately  discovered  in  Siburi-i,  which  attracted  such  general  attention  at  the  Exhibition  of  1862, 
likewise  admits  of  being  purified  by  Sir  B.  Brodie's  process. 

[*  It  removes  from  solution  in  tatter  the  vegetable  bases,  bitter  principles,  and  astringent 
subst  mres  when  employed  in  excess,  requiring  from  twice  to  twenty  times  their  weight  for 
total  precipitation.  A  soiurio:i  of  iodine  in  w.ite.r,  or  of  iodide  of  potassium,  is  quickly  deprived 
Of  color.  .Metallic  salts  dissolved  in  water,  or  diluted  alcohol,  are  precipitated,  though  not 
entirely,  requiring  about  thirty  times  their  weight  of  animal  charcoal.  Arsenious  acid  is 
totally  carried  out  of  solution.  In  these  cases  it  acts  in  three  different  ways  :  the  salt  is  ab- 
Korbed  unaltered;  the  oxide  in  til  •  salt  may  be  reduced;  or,  the  salts  precfpitated  in  a  basic 
condition,  the  solution  showing  an  acid  reaction  as  soon  as  the  carbon  begins  to  act.  It  is  in 
this  last  cas  •  csp-ciilly  th  if  traces  of  the  bases  can  be  detected,  the  acid  set  free  preventing 
thttir  total  precipitation.  The  precipitation  may  hence  be  prevented  by  adding  an  excess  of 
acid,  and  the  bases  after  precipitation  may  be  dissolved  out  by  boiling  with  an  acid  solution.— 
Warrington,  M  >m  Oliiin.  Soc.  1845:  G  irrod.  I'harrn.  Journ.  1845;  Weppen,  Ann.  dft  Chim.  1846. 
Carbon  is  a  combustible  uniting  with  oxygen  and  producing  carbonic  acid.  Its  different  forms 
exhibit  much  difference  in  this  respect:  in  the  very  porous  condition  of  charcoal  it  burns 
readily,  while  in  its  most  dense  form,  the  diamond, 'it  requires  a  bright-red  heat  and  pure 
oxygen  gas.  In  the  form  of  charcoal,  it  conducts  heat  slowly  and  electricity  readilv.  Carbon 
is  insoluble  in  water  and  not  liable  to  be  affected  by  air  and  moisture.  It  retards  putrefac- 
tion. — 11.  B.] 


166 


CARBON. 


called  carbon  monoxide  and  carbon  dioxide :    their  composition  may  be 
thus  stated: 


Composition  by  weight. 


Carbon  monoxide 
Carbon  dioxide 


Carbon. 

.    12 

12 


Oxygen. 
16 

32 


CARBON  DIOXIDE,  or  CARBONIC  OXIDE  (commonly  called  Carbonic  Acid], 
is  always  produced  when  charcoal  burns  in  air  or  oxygen  gas :  it  is  most 
conveniently  obtained,  however,  for  study,  by  decomposing  a  carbonate 
with  one  of  the  stronger  acids.  For  this  purpose,  the  apparatus  for  gen- 
erating hydrogen  may  again  be  employed:  Fragments  of  marble  are  put 
into  the  bottle  with  enough  water  to  cover  the  extremity  of  the  funnel- 
tube,  and  hydrochloric  or  nitric  acid  is  added  by  the  latter,  until  the  gas  is 
freely  disengaged.  Chalk-powder  and  dilute  sulphuric  acid  may  be  used 
instead.  The  gas  may  be  collected  over  water,  although  with  some  loss; 
or  very  conveniently  by  displacement,  if  it  be  required  dry,  as  shown  in 
fig.  118.  The  long  drying-tube  is  filled  with  fragments  of  calcium  chloride, 

Fig.  118. 


and  the  heavy  gas  is  conducted  to  the  bottom  of  the  vessel  in  which  it  is 
to  be  received,  the  mouth  of  the  latter  being  lightly  closed.* 

Carbon  dioxide  is  a  colorless  gas ;  it  has  an  agreeable  pungent  taste  and 
color,  but  cannot  be  respired  for  a  minute  without  insensibility  following. 
Its  specific  gravity  is  1-524,-j-  a  litre  weighing  1-96664  grams  and  100  cubic 
inches  weighing  47-26  grains. 

Fig.  119.  This    gas    is    very  hurtful   to    animal    life,    even 

when  largely   diluted  with  air;    it   acts    as    a    nar- 


*  In  connecting  tube-apparatus  for  conveying  gases  or  cold 
liquids,  not  corrosive,  little  tubes  of  caoutchouc  about  an  inch  long 
are  inexpressibly  useful.  These  are  made  by  bending  a  piece  of 
sheet  india-rubber  loosely  round  a  glass  tube  or  rod,  and  cutting 
off  the  superfluous  portion  with  sharp  scissois.  The  fresh-cut 
edges  of  the  caoutchouc,  pressed  strongly  together,  cohere  com- 
pletely, and  the  tube  is  perfect,  provided  they  have  not  been 
soiled  by  touching  with  the  finders.  The  connectors  are  secured 
by  two  or  three  turns  of  thin  silk  cord.  Tubes  of  various  sizes, 
made  of  vulcanized  india-rubber,  are  now  articles  of  commerce, 
and  may  be  conveniently  substituted  for  those  made  in  the  labo- 
ratory. The  glass  tubes  are  sold  by  weight,  and  are  easily  bent  in 
the  flame  of  a  spirit-lamp,  and,  when  necessary,  cut  by  scratching 
with  a  file,  and  broken  asunder. 

f  Dulong  and  Berzelius. 


CARBON.  167 

cotic  poison.  Hence  the  danger  arising  from  imperfect  ventilation, 
the  use  of  fireplaces  and  stoves  of  all  kinds  unprovided  with  proper 
chimneys,  and  the  crowding  together  of  many  individuals  in  houses 
and  ships  without  efficient  means  for  renewing  the  air;  for  carbon 
dioxide  is  constantly  disengaged  during  the  process  of  respiration,  which, 
as  we  have  seen  (p.  131),  is  nothing  but  a  process  of  slow  combustion. 
This  gas  is  sometimes  emitted  in  large  quantity  from  the  earth  in  volcanic 
districts,  and  it  is  constantly  generated  where  organic  matter  is  in  the  act 
of  undergoing  fermentive  decomposition.  The  fatal  "after-damp"  of  the 
coal-mines  contains  a  large  proportion  of  carbon  dioxide. 

A  lighted  taper  plunged  into  carbon  dioxide  is  instantly  extinguished 
even  to  the  red-hot  snutf.  When  diluted  with  three  times  its  volume  of 
air,  it  still  retains  the  power  of  extinguishing  a  light.  The  gas  is  easily 
known  from  nitrogen,  which  is  also  incapable  of  supporting  combustion, 
by  its  rapid  absorption  by  caustic  alkali,  or  by  lime-water ;  the  turbidity 
communicated  to  the  latter  from  the  production  of  insoluble  calcium  car- 
bonate is  very  characteristic. 

Cold  water  dissolves  about  its  own  volume  of  carbon  dioxide,  whatever 
be  the  density  of  the  gas  with  which  it  is  in  contact  (comp.  p.  151);  the 
solution  temporarily  reddens  litmus-paper.  In  common  soda-water,  and 
also  in  eifervescent  wines,  examples  may  be  seen  of  the  solubility  of  the 
gas.  Even  boiling  water  absorbs  a  perceptible  quantity. 

Some  of  the  interesting  phenomena  attending  the  liquefaction  of  carbon 
dioxide  have  been  already  described:  it  requires  for  the  purpose  a  pres- 
sure of  between  27  and  28  atmospheres  at  0°,  according  to  Mr.  Adams. 
The  liquefied  oxide  is  colorless  and  limpid,  lighter  than  water,  and  four 
times  more  expansible  than  air:  it  mixes  in  all  proportions  with  ether, 
alcohol,  naphtha,  oil  of  turpentine,  and  carbon  disulphide,  and  is  insoluble 
in  water  and  fat  oils.  In  this  condition  it  does  not  exhibit  any  of  the 
properties  of  an  acid. 

Carbon  dioxide  exists,  as  already  mentioned,  in  the  air:  relatively  its 
quantity  is  but  small ;  but  absolutely,  taking  into  account  the  vast  extent 
of  the  atmosphere,  it  is  very  great,  and  fully  adequate  to  the  purpose  for 
which  it  is  designed,  — namely,  to  supply  to  plants  their  carbon,  these  lat- 
ter having  the  power,  by  the  aid  of  their  green  leaves,  of  decomposing 
carbon  dioxide,  retaining  the  carbon,  and  expelling  the  oxygen.  The 
presence  of  light  is  essential  to  this  effect,  but  of  the  manner  in  which  it 
is  produced  we  are  yet  ignorant. 

The  carbonates  form  a  very  large  and  important  group  of  salts,  some  of 
which  occur  in  nature  in  great  quantities,  as  the  carbonates  of  calcium 
and  magnesium.  They  contain  the  elements  of  carbon  dioxide  and  a  me- 
tallic oxide:  calcium  carbonate,  for  example,  being  composed  of  44  parts 
by  weight  of  carbon  dioxide  and  56  parts  of  calcium  oxide  or  lime,  or  of 
12  carbon,  48  oxygen,  and  40  calcium ;  *  but  they  are  never  formed  by  the 
direct  union  of  dry  carbon  dioxide  with  a  dry  metallic  oxide,  the  inter- 
vention of  water  being  always  required  to  bring  about  the  combination. 
Potassium  carbonate  (pearlash)  is  the  chief  constituent  of  wood-ashes; 
sodium  carbonate  is  contained  in  the  ashes  of  marine  plants,  and  is  manu- 
factured on  a  very  large  scale  by  heating  sodium  sulphate  with  lime  and 
coal.  These  carbonates  are  soluble  in  water.  The  other  metallic  carbon- 
ates, which  are  insoluble,  may  be  formed  by  mixing  a  solution  of  potas- 
sium or  sodium  carbonate  with  a  soluble  metallic  salt;  thus,  when  solu- 
tions of  lead  nitrate  and  sodium  carbonate  are  mixed  together,  the  lead 
and  sodium  change  places,  forming  sodium  nitrate,  which  remains  dis- 
solved, and  lead  carbonate,  which,  being  insoluble  in  water,  is  precipi- 

*  C03Ca  or  COg.CaO. 


168  CARBON. 

tated  *  in  the  form  of  a  white  powder.     This  is  an  example  of  double  de- 
composition, the  most  frequent  of  all  forms  of  chemical  action. 

The  solution  of  carbon  dioxide  in  water  may  be  supposed  to  contain 
hydrogen  carbonate,  or  carbonic  acid,  consisting  of  12  parts  by  weight  of 
carbon,  48  oxygen,  and  2  hydrogen ;  f  but  this  compound  is  not  known  in 
the  separate  state,  only  in  aqueous  solution. 

CARBON  MONOXIDE,  or  CARBONOUS  OXIDE  (commonly  called  Carbonic 
Oxide). — When  carbon  dioxide  is  passed  over  red-hot  charcoal  or  metallic 
iron,  one-half  of  its  oxygen  is  removed,  and  it  becomes  converted  into 
carbon  monoxide.  A  very  good  method  of  preparing  this  gas  is  to  intro- 
duce into  a  flask  fitted  with  a  bent  tube  some  crystallized  oxalic  acid,  or 
salt  of  sorrel,  and  pour  upon  it  five  or  six  times  as  much  strong  oil  of 
vitriol. J  On  heating  the  mixture,  the  organic  acid  is  resolved  into  water, 
carbon  dioxide,  and  carbon  monoxide ;  and  by  passing  the  gases  through 
a  strong  solution  of  caustic  potash,  the  first  is  withdrawn  by  absorption, 
while  the  second  remains  unchanged.  Another  and,  it  may  be,  preferable 
method,  is  to  heat  finely  powdered  yellow  potassium  ferrocyanide  with 
eight  or  ten  times  its  weight  of  concentrated  sulphuric  acid.  The  salt  is 
entirely  decomposed,  yielding  a  most  copious  supply  of  perfectly  pure 
carbonous  oxide  gas,  which  may  be  collected  over  water  in  the  usual 
manner.  $ 

Carbon  monoxide  is  a  combustible  gas ;  it  burns  with  a  beautiful  pale- 
blue  flame,  generating  carbon  dioxide.  It  has  never  been  liquefied.  It  is 
colorless,  has  very  little  odor,  and  is  extremely  poisonous — much  more  so 
than  carbon  dioxide.  Mixed  with  oxygen,  it  explodes  by  the  electric  spark, 
but  with  some  difficulty.  Its  specific  gravity  is  0-973;  a  litre  weighs 
1-2515  grams;  100  cubic  inches  weigh  30-21  grains. 

The  relation  by  volume  of  these  oxides  of  carbon  may  thus  be  made  in- 
telligible: carbon  dioxide  contains  its  own  volume  of  oxygen,  that  gas 
suffering  no  change  of  bulk  by  its  conversion.  One  measure  of  carbon 
monoxide,  mixed  with  half  a  measure  of  oxygen  and  exploded,  yields  one 
measure  of  carbon  dioxide  ;  hence  carbon  monoxide  contains  half  its  volume 
of  oxygen. 

Carbon  monoxide  unites  with  chlorine  under  the  influence  of  light,  form- 
ing a  pungent,  suffocating  compound,  possessing  acid  properties,  called 
phosgene  gas,  or  carbonyl  chloride.  It  made  by  mixing  equal  volumes  of 
carbon  monoxide  and  chlorine,  both  perfectly  dry,  and  exposing  the  mix- 
ture to  sunshine:  the  gases  unite  quietly,  the  color  disappears,  and  the 
volume  becomes  reduced  to  one  half.  A  more  convenient  method  for  pre- 
paring this  gas  consists  in  passing  carbon  monoxide  through  antimony 
pentachloride.  It  is  decomposed  by  water. 


*    COgNa^        +        (N03)2Pb        =        2N03Na        +        C03Pb 

Sodium  Lead  Sodium  Lead 

carbonate.  nitrate.  nitrate.  carbonate, 

t  C  03II2  or  C02OII2. 

%  2C04TT2        =        CO        +        C02        +        OTT2 
Oxalic  Carbon  Carbon  "Water. 

acid.  monoxide.          dioxide. 

g  The  reaction  is  represented  by  the  equation : 

C6N0K4Fe  +  60Ha  +  6S04H2  =  6CO  +  2S04K2  +  3S04(NH4)2  +  S04Fe 
Potassium  Water.  Sulphuric  Carbon  Potassium  Ammonium  Ferrous 
ferrocyanide.  acid.  monoxide,  sulphate.  sulphate.  sulphate. 

See  a  paper  by  the  author  in  the  Memoirs  of  the  Chemical  Society,  i.  251. 


COMPOUNDS  OF  CARBON  AND  HYDROGEN.  169 

Compounds  of  Carbon  and  Hydrogen. 

The  compounds  of  carbon  and  hydrogen  already  known  are  exceedingly 
numerous:  perhaps  all,  in  strictness,  belong  to  the  domain  of  organic 
chemistry,  as  they  cannot,  except  in  very  few  cases,  be  formed  by  the  di- 
rect union  of  their  elements,  but  always  arise  from  the  decomposition  of  a 
complex  body  of  organic  origin.  It  will  be  found  convenient,  notwith- 
standing, to  describe  two  of  thorn  in  this  part  of  the  volume,  as  they  very 
well  illustrate  the  important  subjects  of  combustion  and  the  nature  of  flame. 

METHANE  or  MARSH  GAS  ;  LIGHT  CARBONETTED  HYDROGEN  ;  FIRE-DAMP. — 
This  gas  is  but  too  often  found  to  be  abundantly  disengaged  in  coal- 
mines from  the  fresh-cut  surface  of  the  coal,  and  from  remarkable  aper- 
tures or  "blowers,"  which  emit  for  a  great  length  of  time  a  copious  stream 
or  jet  of  gas,  probably  existing  in  a  state  of  compression,  pent  up  in  the 
coal. 

The  mud  at  the  bottom  of  pools  in  which  water-plants  grow,  on  being 
stirred,  suffers  bubbles  of  gas  to  escape,  which  may  be  easily  collected. 
This,  on  examination,  is  found  to  be  chiefly  a  mixture  of  light  carbonetted 
hydrogen  and  carbon  dioxide :  the  latter  is  easily  absorbed  by  lime-water 
or  caustic  potash. 

For  a  long  time,  no  method  was  known  by  which  the  gas  in  question 
could  be  produced  in  a  state  approaching  to  purity  by  artificial  means; 
the  various  illuminating  gases  from  pit-coal  and  oil,  and  that  obtained  by 
passing  the  vapor  of  alcohol  through  a  red-hot  tube,  contain  large  quan- 
tities of  light  carbonetted  hydrogen,  associated,  however,  with  other  sub- 
stances which  hardly  admit  of  separation;  but  Dumas  has  discovered  a 
method  by  which  that  gas  can  be  produced  at  will;  perfectly  pure,  and 
in  any  quantity.* 

A  mixture  is  made  of  40  parts  crystallized  sodium  acetate,  40  parts  solid 
sodium  hydrate,  and  60  parts  quicklime  in  powder.  This  mixture  is  trans- 
ferred to  a  flask  or  retort,  and  strongly  heated ;  the  gas  is  disengaged  in 
great  abundance,  and  may  be  collected  over  water,  while  sodium  carbonate 
remains  behind. f 

Methane  is  a  colorless  and  nearly  inodorous  gas,  which  does  not  affect 
vegetable  colors.  It  burns  with  a  yellow  flame,  generating  carbon  dioxide 
and  water.  It  is  not  poisonous,  and  may  be  respired  to  a  great  extent 
without  apparent  injury.  The  density  of  this  compound  is  about  0-559,  a 
litre  weighing  0.71558  grams,  and  100  cubic  inches  weighing  17-41  grains; 
it  contains  carbon  and  hydrogen  associated  in  the  proportion  of  12  parts 
by  weight  of  the  former  to  4  of  the  latter.  J 

When  100  measures  of  this  gas  are  mixed  with  200  of  pure  oxygen  in  the 
eudiometer,  and  the  mixture  exploded  by  the  electric  spark,  100  measures 
of  gas  remain,  which  are  entirely  absorbable  by  a  little  solution  of  caustic 
potash.  Now,  carbon  dioxide  contains  its  own  volume  of  oxygen:  hence 
one-half  the  oxygen  added  —  that  is,  100  measures  —  must  have  been  con- 
sumed in  uniting  with  the  hydrogen.  Consequently,  the  gas  must  contain 
twice  its  own  measure  of  hydrogen,  and  enough  carbon  to  produce,  when 
completely  burned,  an  equal  quantity  of  carbon  dioxide. 

*  Ann.  Chim.  Phys.  Ixxiii.  93. 

•j-  The  reaction  is  repi-osi-nted  by  the  equation: 

C2H302Na       +       NallO       =       CH4       +       C08Na3 
Sodium  Sodium  Marsh  Sodium 

acetate.  hydrate.  gas.  carbonate. 

The  use  of  the  lime  is  merely  to  prevent  the  sodium  hydrate  from  fusing  and  attacking  the 
lass. 

J  The  two  carbides  of  hydrogen  here  described  are  represented  by  the  following  formula  : 
Methane  or  Marsh  gas    .    .    CH4.  Ethene  or  Olefiant  gas    .    .    C2H4. 

15 


170          COMPOUNDS    OF    CARBON    AND    HYDROGEN. 

When  chlorine  is  mixed  with  marsh  gas  over  water,  no  change  follows, 
provided  light  be  excluded.  The  presence  of  light,  however,  brings  about 
decomposition,  hydrochloric  acid,  carbon  dioxide,  and  sometimes  other 
products,  being  formed.  It  is  important  to  remember  that  this  gas  is  not 
acted  upon  by  chlorine  in  the  dark. 

ETHENE  or  OLEFIANT  GAS.  —  Strong  spirit  of  wine  is  mixed  with  five  or 
six  times  its  weight  of  oil  of  vitriol  in  a  glass  flask,  the  tube  of  which  passes 
into  a  wash-bottle  containing  caustic  potash.  A  second  wash-bottle,  partly 
filled  with  oil  of  vitriol,  is  connected  with  the  first,  and  furnished  with  a 
tube  dipping  into  the  water  of  the  pneumatic  trough.  On  the  first  applica- 
tion of  heat  to  the  contents  of  the  flask,  alcohol,  and  afterwards  ether, 
make  their  appearance ;  but,  as  the  temperature  rises,  and  the  mixture 
blackens,  the  ether-vapor  diminishes  in  quantity,  and  its  place  becomes  in 
great  part  supplied  by  a  permanent  inflammable  gas ;  carbon  dioxide  and 
sulphurous  oxide  are  also  generated  at  the  same  time,  besides  traces  of 
other  products.  The  two  last-mentioned  gases  are  absorbed  by  the  alkali 
in  the  first  bottle,  and  the  ether-vapor  by  the  acid  in  the  second,  so  that  the 
olefiant  gas  is  delivered  tolerably  pure.  The  entire  reaction  is  too  complex 
to  be  discussed  at  the  present  moment ;  it  will  be  found  fully  described  in 
another  part  of  the  volume ;  but  the  ethene  may  be  regarded  as  resulting 
from  a  simple  dehydration  of  the  alcohol  by  the  oil  of  vitriol.*  Olefiant 
gas  thus  produced  is  colorless,  neutral,  and  but  slightly  soluble  in  water. 
Alcohol,  ether,  oil  of  turpentine,  and  even  olive  oil,  as  Faraday  has  observed, 
dissolve  it  to  a  considerable  extent.  It  has  a  faint  odor  of  garlic.  On  the 
approach  of  a  kindled  taper,  it  takes  fire,  and  burns  with  a  splendid  white 
light,  far  surpassing  in  brilliancy  that  produced  by  marsh  gas.  This  gas, 
when  mixed  with  oxygen,  and  fired,  explodes  with  extreme  violence.  Its 
density  is  0-981 ;  a  litre  wreighs  1-25194  grams;  100  cubic  inches  weigh  30-57 
grains. 

By  the  use  of  the  eudiometer,  as  already  described,  it  has  been  found  that 
each  measure  of  ethene  requires  for  complete  combustion  exactly  three  of 
oxygen,  and  produces  under  these  circumstances  two  measures  of  carbon 
dioxide ;  whence  it  is  evident  that  it  contains  twice  its  own  volume  of  hy- 
drogen combined  with  twice  as  much  carbon  as  in  methane. 

By  weight,  these  proportions  will  be  24  parts  carbon  and  4  parts  hydrogen. 

Ethene  is  decomposed  by  passing  it  through  a  tube  heated  to  bright  red- 
ness; a  deposit  of  charcoal  and  tar  takes  place,  and  the  gas  becomes  con- 
verted into  marsh  gas,  or  even  into  free  hydrogen,  if  the  temperature  be  very 
high.  This  latter  change  is,  of  course,  attended  by  increase  of  volume. 

Chlorine  acts  upon  ethene  in  a  very  remarkable  manner.  When  the  two 
bodies  are  mixed,  even  in  the  dark,  they  combine  in  equal  measures,  and 
give  rise  to  a  heavy  oily  liquid,  of  sweetish  taste  and  ethereal  odor,  to 
which  the  name  of  ethene  chloride,  or  Dutch  liquid,-}-  is  given.  It  is  from 
this  peculiarity  that  the  term  olefiant  gas  is  derived. 

A  pleasing  and  instructive  experiment  may  also  be  made  by  mixing  in  a 
tall  jar  two  measures  of  chlorine  and  one  of  ethene,  and  then  quickly  ap- 
plying a  light  to  the  mouth  of  the  vessel.  The  chlorine  and  hydrogen  unite 
with  flame,  which  passes  quickly  down  the  jar,  while  the  whole  of  the  carbon 
is  set  free  in  the  form  of  a  thick  black  smoke, 

COAL  AND  OIL  GASES.  —  The  manufacture  of  coal-gas  is.  at  the  present 
moment,  a  branch  of  industry  of  great  interest  and  importance  in  several 
points  of  view.  The  process  is  one  of  great  simplicity  of  principle,  but 
requires,  in  practice,  some  delicacy  in  management  to  yield  a  good  result. 

*C2IT60  =  C«H4  -f  OH2 

Alcohol.  Ethene.  Water. 


COMPOUNDS    OF    CARBON    AND    HYDROGEN.          171 

When  pit-coal  is  subjected  to  destructive  distillation,  a  variety  of  products 
show  themselves  —  permanent  gases,  steam,  and  volatile  oils,  besides  a  not 
inconsiderable  quantity  of  ammonia  from  the  nitrogen  always  present  in 
the  coal.  These  substances  vary  very  much  in  their  proportions  with  the 
temperature  at  which  the  process  is  conducted,  the  permanent  gases  be- 
coming more  abundant  with  increased  heat,  but,  at  the  same  time,  losing 
much  of  their  value  for  the  purposes  of  illumination. 

The  coal  is  distilled  in  cast-iron  retorts,  maintained  at  a  bright-red  heat, 
and  the  volatilized  product  is  conducted  into  a  long  horizontal  pipe  of  large 
dimensions,  always  half  filled  with  liquid,  into  which  the  extremity  of  each 
separate  tube  dips:  this  is  called  the  hydraulic  main.  The  gas  and  its 
accompanying  vapors  are  next  made  to  traverse  a  refrigerator  —  usually  a 
scries  of  iron  pipes,  cooled  on  the  outside  by  a  stream  of  water;  here  the 
condensation  of  the  tar  and  the  ammoniacal  liquid  becomes  complete,  and 
the  gas  proceeds  onward  to  another  part  of  the  apparatus,  in  which  it  is 
deprived  of  the  sulphuretted  hydrogen  and  carbonic  acid  gases  always  pres- 
ent in  the  crude  product.  This  was  formerly  effected  by  slaked  lime,  which 
readily  absorbs  the  compounds  in  question.  The  use  of  lime,  however,  has 
been  almost  superseded  by  that  of  a  mixture  of  sawdust  and  iron  oxide. 
This  mixture,  after  having  been  employed,  is  exposed  for  some  time  to  the 
atmosphere,  and  is  then  fit  for  use  a  second  time.  The  purifiers  are  large 
iron  vessels,  filled  either  with  slaked  lime  or  with  the  iron  oxide  mixture. 
The  gas  is  admitted  at  the  bottom  of  the  vessel,  and  made  to  pass  over  a 
large  surface  of  the  purifying  agents.  The  last  part  of  the  operation, 
which,  indeed,  is  often  omitted,  consists  in  passing  the  gas  through  dilute 
sulphuric  acid,  in  order  to  remove  ammonia.  The  quantity  thus  separated 
is  very  small,  relatively,  to  the  bulk  of  the  gas,  but,  in  an  extensive  work, 
becomes  an  object  of  importance. 

Coal-gas  thus  manufactured  and  purified  is  preserved  for  use  in  immense 
cylindrical  receivers,  closed  at  the  top,  suspended  in  tanks  of  water  by 
chains  to  which  counterpoises  are  attached,  so  that  the  gas-holders  rise 
and  sink  in  the  liquid  as  they  become  filled  from  the  purifiers  or  emptied 
by  the  mains.  These  latter  are  made  of  large  diameter,  to  diminish  as 
much  as  possible  the  resistance  experienced  by  the  gas  in  passing  through 
such  a  length  of  pipe.  The  joints  of  these  mains  are  still  made  in  so  im- 
perfect a  manner  that  immense  loss  is  experienced  by  leakage  when  the 
pressure  upon  the  gas  at  the  works  exceeds  that  exerted  by  a  column  of 
water  an  inch  in  height.* 

Coal-gas  varies  very  much  in  composition,  judging  from  its  variable  den- 
sity and  illuminating  powers,  and  from  the  analyses  which,have  been  made. 
The  difficulties  of  such  investigations  are  very  great,  and  unless  particular 
precaution  be  taken,  the  results  are  merely  approximative.  The  purified 
gas  is  believed  to  contain  the  following  substances,  of  which  the  first  is  the 
most  abundant,  and  the  second  the  most  valuable : 

Methane,  or  Marsh  gas. 
Ethene,  or  Olefiant  gas. 
Hydrogen. 

*  It  may  give  some  idea  of  the  extent  of  this  species  of  manufacture,  to  mention  that  in  the 
year  1838,  for  lighting  London  and  the  suburbs  alone,  there  were  eighteen  public  gas-works, 
and  £2,800,000  invested  in  pipes  and  apparatus.  The  yearly  revenue  amounted  to  £450.000,  and 
the  consumption  of  coal  in  the  same  period  to  180,000  tons,  1460  millions  of  cubic  feet  of  g;i$ 
being  made  in  the  year.  There  were  134,300  private  lights,  and  30,400  street  lamps.  S«MI  tons 
of  coal  were  used  in  the  retorts  in  the  space  of  twenty-four  hours  at  mid-winter,  and  7,l-0,uu) 
cubic  feet  of  gas  consumed  in  the  longest  night.  —  Ure,  Dictionary  of  Arts  and  Manufacture!. 

Since  that  time,  the  production  of  gas  has  been  enormously  increased.  The  amount  of  coal 
used  in  London  for  gas-making  in  1857  is  estimated  at  more  than  800,000  tons,  yielding  not  less 
than  7,000,000  of  cubic  feet  of  gas.  In  the  same  year,  the  mains  in  the  London  streets  had 
reached  the  extraordinary  length  of  2000  miles. 


172  COMBUSTION,    AND 

Carbon  Monoxide. 

Nitrogen. 

Vapors  of  volatile  liquid  Hydrocarbons.* 

Vapor  of  Carbon  Bisulphide. 

Separated  by  Condensation  and  by  the  Purifiers. 

Tar  and  Volatile  Oils. 

Ammonium  Sulphate,  Chloride,  and  Sulphide. 

Hydrogen  Sulphide. 

Carbon  Dioxide. 

Hydrocyanic  acid,  or  Ammonium  Cyanide. 

Sulphocyanic  acid,  or  Ammonium  Sulphocyanate. 

A  far  better  illuminating  gas  may  be  prepared  from  oil,  by  dropping  it 
into  a  red-hot  iron  retort  filled  with  coke  ;  the  liquid  is  in  great  part  decom- 
posed and  converted  into  permanent  gas,  which  requires  no  purification,  as 
it  is  quite  free  from  the  ammoniacal  and  sulphur  compounds  which  vitiate 
gas  from  coal,  ^lany  years  ago,  this  article  was  prepared  in  London ;  it 
was  compressed  for  the  use  of  the  consumer  into  strong  iron  vessels,  to  the 
extent  of  30  atmospheres ;  these  were  furnished  with  a  screw-valve  of  pe- 
culiar construction,  and  exchanged  for  others  when  exhausted.  The  com- 
parative high  price  of  the  material,  and  other  circumstances,  led  to  the 
abandonment  of  the  undertaking.  On  the  Continent,  gas  is  now  extensively 
prepared  from  wood. 

COMBUSTION,  AND  THE  STRUCTURE  OF  FLAME. 

When  any  solid  substance  capable  of  bearing  the  fire  is  heated  to  a  cer- 
tain point,  it  emits  light,  the  character  of  which  depends  upon  the  tempera- 
ture, Thus,  a  bar  of  platinum  or  a  piece  of  porcelain,  raised  to  a  particu- 
lar temperature,  becomes  what  is  called  red-hot,  or  emissive  of  red  light : 
at  a  higher  degree  of  heat,  this  light  becomes  whiter  and  more  intense,  and 
when  urged  to  the  utmost,  as  in  the  case  of  a  piece  of  lime  placed  in  the 
flame  of  the  oxyhydrogen  blowpipe,  the  light  becomes  exceedingly  powerful, 
and  acquires  a  tint  of  violet.  Bodies  in  these  states  are  said  to  be  incan- 
descent or  ignited, 

Again,  if  the  same  experiment  be  made  on  a  piece  of  charcoal,  similar 
effects  will  be  observed ;  but  something  in  addition :  for  whereas  the  plati- 
num or  porcelain,  when  removed  from  the  fire,  or  the  lime  from  the  blow- 
pipe flame,  begin  immediately  to  cool,  and  emit  less  and  less  light,  until 
they  become  completely  obscure,  the  charcoal  maintains  to  a  great  extent 
its  high  temperature.  Unlike  the  other  bodies,  too,  which  suffer  no  change 
whatever,  either  of  weight  or  substance,  the  charcoal  gradually  wastes 
away  until  it  disappears.  This  is  what  is  called  combustion,  in  contradis- 
tinction to  mere  ignition ;  the  charcoal  burns,  and  its  temperature  is  kept 
up  by  the  heat  evolved  in  the  act  of  union  with  the  oxygen  of  the  air. 

In  the  most  general  sense,  a  body  in  a  state  of  combustion  is  one  in  the  act 
of  undergoing  intense  chemical  action :  any  chemical  action  whatsoever,  if 
its  energy  rise  sufficiently  high,  may  produce  the  phenomenon  of  combus- 
tion, by  heating  the  body  to  such  an  extent  that  it  becomes  luminous. 

In  all  ordinary  cases  of  combustion,  the  action  lies  between  the  burning 
body  and  the  oxygen  of  the  air ;  and  since  the  materials  employed  for  the 
economical  production  of  heat  and  light  consist  of  carbon  chiefly,  or  that 
substance  conjoined  with  a  certain  proportion  of  hydrogen  and  oxygen,  all 
common  effects  of  this  nature  are  cases  of  the  rapid  and  violent  oxidation 
of  carbon  and  hydrogen  by  the  aid  of  the  free  oxygen  of  the  air.  The  heat 

*  These  bodies  increase  the  illuminating  power,  and  confer  on  the  gas  its  peculiar  odor. 


THE    STRUCTURE    OF    FLAME. 


173 


must  be  referred  to  the  act  of  chemical  union,  and  the  light  to  the  elevated 
temperature. 

By  this  principle,  it  is  easy  to  understand  the  means  which  must  be 
adopted  to  increase  the  heat  of  ordinary  fires  to  the  point  necessary  to  melt 
refractory  metals,  and  to  bring  about  certain  desired  effects  of  chemical 
decomposition.  .If  the  rate  of  consumption  of  the  fuel  can  be  increased  by 
a  more  rapid  introduction  of  air  into  the  burning  mass,  the  intensity  of  the 
heat  will  of  necessity  rise  in  the  same  ratio,  the  quantity  of  heat  evolved 
being  fixed  and  definite  for  the  same  constant  quantity  of  chemical  action. 
This  increased  supply  of  air  may  be  effected  by  two  distinct  methods:  it 
may  be  forced  into  the  fire  by  bellows  or  blowing-machines,  as  in  the  com- 
mon forge  and  in  the  blast,  and  cupola-furnaces  of  the  iron-worker,  or  it 
may  be  drawn  through  the  burning  materials  by  the  help  of  a  tall  chimney, 
the  fireplace  being  closed  on  all  sides,  and  no  entrance  of  air  allowed,  save 
between  the  bars  of  the  grate.  Such  is  the  kind  of  furnace  generally  em- 
ployed by  the  scientific  chemist  in  assaying  and  in  the  reduction  of  metallic 
oxides  by  charcoal :  the  principle  will  be  at  once  understood  by  the  aid  of 
the  sectional  drawing  (fig.  120),  in  which  a  crucible  is  represented  arranged 
in  the  fire  for  an  operation  of  the  kind  mentioned. 

Fig.  121. 


The  "reverberatory  "  furnace  (fig.  121)  is  one  very  much  used  in  the 
arts  when  substances  are  to  be  exposed  to  heat  without  contact  with  the 
fuel.  The  fire-chamber  is  separated  from  the  bed  or  hearth  of  the  furnace 
by  a  low  wall  or  bridge  of  brick-work,  and  the  flame  and  heated  air  are  re- 
flected downward  by  the  arched  form  of  the  roof.  Any  degree  of  heat  can 
be  obtained  in  a  furnace  of  this  kind  —  from  the  temperature  of  dull  red- 
ness to  that  required  to  melt  very  large  quantities  of  cast-iron.  The  fire 
is  urged  by  a  chimney  provided  with  a  sliding-plate,  or  damper,  to  regulate 
the  draught. 

Solids  and  liquids,  as  melted  metal,  possess,  when  sufficiently  heated, 
the  faculty  of  emitting  light:  the  same  power  is  exhibited  by  gaseous 
bodies,  but  the  temperature  required  to  render  a  gas  luminous  is  incom- 
parably higher  than  in  the  cases  already  described.  Gas  or  vapor  in  this 
15* 


174  COMBUSTION,    AND 

condition  constitutes  flame,  the  actual  temperature  of  which  generally  ex- 
ceeds that  of  the  white  heat  of  solid  bodies. 

,  The  light  emitted  from  pure  flame  is  often  exceedingly  feeble ;  but  the 
illuminating  power  may  be  immensely  increased  by  the  presence  of  solid 
matter.  The  flame  of  hydrogen,  or  of  the  mixed  gases,  is  scarcely  visible 
in  full  daylight;  in  a  dusty  atmosphere,  however,  it  becomes  much  more 
luminous  by  igniting  to  intense  whiteness  the  floating  particles  with  which 
it  comes  in  contact.  The  piece  of  lime  in  the  blow-pipe  flame  cannot  have 
a  higher  temperature  than  that  of  the  flame  itself;  yet  the  light  it  throws 
off  is  infinitely  greater. 

On  the  other  hand,  it  is  possible,  as  recently  pointed  out  by  Dr.  Frank- 
land,  to  produce  very  bright  flames  in  which  no  solid  particles  are  present. 
Metallic  arsenic  burnt  in  a  stream  of  oxygen  produces  an  intense  white 
flame,  although  both  the  metal  itself  and  the  product  of  its  combustion 
(arsenious  oxide)  are  gaseous  at  the  temperature  of  the  flame.  The  com- 
bustion of  a  mixture  of  nitrogen  dioxide  and  carbon  bisulphide  also  pro- 
duces a  dazzling  white  flame,  without  any  separation  of  solid  matter. 

The  conditions  most  essential  to  luminosity  in  a  flame  are  a  high  tem- 
perature, and  the  presence  of  gases  or  vapors  of  considerable  density.  The 
effect  of  high  temperature  is  seen  in  the  greater  brightness  of  the  flame 
of  sulphur,  phosphorus,  and  indeed  all  substances,  when  burnt  in  pure 
oxygen,  as  compared  with  that  which  results  from  their  combustion  in  com- 
mon air;  in  the  former  case  the  whole  of  the  substances  present  take  part 
in  the  combustion  and  generate  heat,  whereas  in  the  latter  the  temperature 
is  lowered  by  the  presence  of  a  large  quantity  of  nitrogen,  which  contrib- 
utes nothing  to  the  effect.  The  relation  between  the  luminosity  of  a  flame 
and  the  vapor-densities  of  its  constituents  may  be  seen  from  the  following 
table,  in  which  the  vapor-densities  are  referred  to  that  of  hydrogen  as  unity. 

Relative  Densities  of  Gases  and  Vapors. 


Hydrogen         ...  1 

Water 9 

Hydrochloric  acid  .         .          18|- 
Carbon  dioxide    .         .         .22 
Sulphur  dioxide       .         .         32 


Arsenious  chloride  .         .         9f 

Phosphoric  oxide     .  71,  or  142 

Metallic  arsenic  .  .          .     150 

Arsenious  oxide  198 


A  comparison  of  these  numbers  shows  that  the  brightest  flames  are  those 
which  contain  the  densest  vapors.  Hydrogen  burning  in  chlorine  produces 
a  vapor  more  than  twice  as  heavy  as  that  resulting  from  its  combustion  in 
oxygen,  and  accordingly  the  light  produced  in  the  former  case  is  stronger 
than  in  the  latter;  carbon  and  sulphur  burning  in  oxygen  produce  vapors 
of  still  greater  density,  namely,  carbon  dioxide  and  sulphur  dioxide,  and 
their  combustion  gives  a  still  brighter  light;  lastly,  phosphorus,  which  has 
a  very  dense  vapor,  and  likewise  yields  a  product  of  great  vapor-density, 
burns  in  oxygen  with  a  brilliancy  which  the  eye  can  scarcely  endure. 
Moreover,  the  luminosity  of  a  flame  is  increased  by  condensing  the  sur- 
rounding gaseous  atmosphere,  and  diminished  by  rarefying  it.  The  flame 
of  arsenic  burning  in  oxygen  may  be  rendered  quite  feeble  by  rarefying 
the  oxygen;  and  on  the  contrary  the  faint  flame  of  an  ordinary  spirit-lamp 
becomes  very  bright  when  placed  under  the  receiver  of  a  condensing  pump. 
Frankland  has  also  found  that  candles  give  much  less  light  when  burning 
on  the  top  of  Mont  Blanc  than  in  the  valley  below,  although  the  rate  of 
combustion  in  the  two  cases  is  nearly  the  same.  The  effect  of  condensa- 
tion in  increasing  the  brightness  of  a  flame  is  also  strikingly  seen  in  the 
combustion  of  a  mixture  of  oxygen  and  hydrogen,  which  gives  but  a  feeble 


THE    STRUCTURE    OF    FLAME. 


175 


Fig.  122. 


V C 


Fig.  123. 


light  when  burnt  under  the  ordinary  atmospheric  pressure,  as  in  the  oxy- 
hydrogen  blowpipe,  but  a  very  briglit  flash  when  exploded  in  the  Cavendish 
eudiometer  (p.  144),  in  which  the  water-vapor  produced  by  the  combustion 
is  prevented  from  expanding. 

Flames  burning  in  the  air,  and  not  supplied  with  oxygen  from  another 
source,  are,  as  already  stated,  hollow,  the  chemical  action  being  necessarily 
confined  to  the  spot  where  the  two  bodies  unite.  That  of  a 
lamp  or  candle,  when  carefully  examined,  is  seen  to  consist 
of  three  separate  portions.  The  dark  central  part,  easily 
rendered  evident  by  depressing  upon  the  flame  a  piece  of 
fine  wire-gauze,  consists  of  combustible  matter  drawn  up  by 
the  capillarity  of  the  wick,  and  volatilized  by  the  heat.  This 
is  surrounded  by  a  highly  luminous  cone  or  envelope,  which, 
in  contact  with  a  cold  body,  deposits  soot.  On  the  outside, 
a  second  cone  is  to  be  traced,  feeble  in  its  light-giving  power, 
but  having  an  exceedingly  high  temperature.  The  most 
probable  explanation  of  these  appearances  is  as  follows : 
Carbon  and  hydrogen  are  very  unequal  in  their  attraction 
for  oxygen,  the  latter  greatly  exceeding  the  former  in  this 
respect:  consequently,  when  both  are  present,  and  the  sup- 
ply of  oxygen  limited,  the  hydrogen  takes  up  the  greater  portion  of  the 
oxygen,  to  the  exclusion  of  a  great  part  of  the  carbon.  Now,  this  happens, 
in  the  case  under  consideration,  at  some  little  distance  within  the  outer 
surface  of  the  flame  —  namely,  in  the  luminous  portion;  the  little  oxygen 
which  has  penetrated  thus  far  inward  is  mostly  consumed  by  the  hydrogen, 
and  hydro -carbons  are  separated,  rich  in  carbon  and 
of  great  density  in  the  state  of  vapor  (naphthalene, 
chryscne,  pyrene,  etc.).  These  hydro-carbons,  which 
would  form  smoke  if  they  were  cooler,  and  are  depos- 
ited on  a  cold  body  held  in  the  flame  in  the  form  of 
soot,*  become  intensely  ignited  by  the  burning  hydro- 
gen, and  evolve  a  light  whose  whiteness  marks  a  very 
elevated  temperature.  In  the  exterior  and  scarcely 
visible  cone,  these  hydro-carbons  undergo  combustion. 

A  jet  of  coal-gas  exhibits  the  same  phenomena  ;  but 
if  the  gas  be  previously  mingled  with  air,  or  if  air 
be  forcibly  mixed  with,  or  driven  into  the  flame,  no 
such  separation  of  carbon  occurs;  the  hydrogen  and 
carbon  burn  together,  forming  vapors  of  much  lower 
density,  and  the  illuminating  power  almost  disappear-s. 

The  common  mouth  blowpipe  is  a  little  instrument 
of  great  utility ;  it  is  merely  a  brass  tube  fitted  with 
an  ivory  mouthpiece,  and  terminated  by  a  jet  having 
a  small  aperture,  by  which  a  current  of  air  is  driven 
across  the  flame  of  a  candle.  The  best  form  is  per- 
haps that  contrived  by  Mr.  Pepys,  and  shown  in  fig. 
123.  The  flame  so  produced  is  very  peculiar. 

Instead  of  the  double  envelope  just  described,  two 
long  pointed  cones  are  observed  (fig.  124),  which, 
when  the  blowpipe  is  good,  and  the  aperture  smooth 
and  round,  are  very  well  defined,  the  outer  cone  being 
yellowish  and  the  inner  blue.  A  double  combustion  is, 
in  fact,  going  on,  by  the  blast  in  the  inside,  and  by  the 

external  air.     The  space  between  the  inner  and  outer  cones  is  filled  with 
exceedingly  hot  combustible  matter,  possessing  strong  reducing  or  deoxidiz- 
ing powers  ;  while  the  highly  heated  air  just  beyond  the  point  of  the  exterior 
*  Soot  is  not  pure  carbon,  but  a  mixture  of  heavy  hydro-carbons. 


176 


COMBUSTION,  AND 


Fig.  124. 


cone  oxidizes  with  great  facility.  A  small  portion  of  matter,  supported  on  a 
piece  of  charcoal,  or  fixed  in  a  ring  at  the  end  of  a  fine  platinum  wire,  can  thus 
in  an  instant  be  exposed  to  a  very  high  degree 
of  heat  under  these  contrasted  circumstances, 
and  observations  of  great  value  made  in  a  very 
short  time.  The  use  of  the  instrument  requires 
an  even  and  uninterrupted  blast  of  some  dura- 
tion, by  a  method  easily  acquired  with  a  little 
patience :  it  consists  in  employing  for  the  pur- 
pose the  muscles  of  the  cheeks  alone, 'respira- 
tion being  conducted  through  the  nostrils,  and 
the  mouth  from  time  to  time  replenished  with 
air,  without  intermission  of  the  blast. 

The  Argand  lamp,  adapted  to  burn  either  oil 

or  spirit,  but  especially  the  latter,  is  a  very  useful  piece  of  chemical  appa- 
ratus. In  this  lamp  the  wick  is  cylindrical,  the  flame  being  supplied  with 
air  both  inside  and  outside :  the  combustion  is  greatly  aided  by  the  chim- 
ney, which  is  made  of  copper  when  the  lamp  is  used  as  a  source  of  heat. 

Fig.  125  exhibits,  in  section,  an  excellent  lamp  of  this  kind  for  burning 
alcohol  or  wood-spirit.  It  is  constructed  of  thin  copper,  and  furnished  with 
ground  caps  to  the  wick-holder  and  aperture,*  by  which  the  spirit  is  intro- 


Fig.  125. 


Fig.  126. 


duced,  in  order  to  prevent  loss  when  the  lamp  is  not  in  use.  Glass  spirit- 
lamps  (fig.  126),  fitted  with  caps  to  prevent  evaporation,  are  very  convenient 
for  occasional  use,  being  always  ready  and  in  order.f 

In  London,  and  other  large  towns  where  coal-gas  is  to  be  had,  it  is  con- 
stantly used  with  the  greatest  economy  and  advantage  in  every  respect  as 
a  source  of  heat.  Retorts,  flasks,  capsules,  and  other  vessels,  can  be  thus 


Fig.  127. 


*  When  in  use,  this  aperture  must  always  be 
open,  otherwise  an  accident  is  sure  to  happen  ; 
the  heat  expands  the  air  in  the  lamp,  and  the 
spirit  is  forced  out  in  a  state  of  inflammation. 

f  [A  modification  of  the  Argand  lamp  con- 
trived by  the  late  Professor  J.  K.  Mitchel  is  ad- 
vantageous, from  the  wick-holder  being  kept 
constantly  cool  by  the  current  of  air  always 
passing  between  it  and  the  body  of  the  lamp. 
"  It  is  made  of  tinned  iron.  The  alcohol  is  poured 
out  by  means  of  the  hollow  handle,  arid  is  ad- 
mitted to  the  cylindrical  burner  by  two  or  three 
tubes  which  are  placed  at  the  very  bottom  of  the 
fountain.  By  such  an  arrangement  of  parts,  the 
alcohol  may  be  added  as  it  is  consumed,  and  the 
flame  kept  uniform  ;  and  as  the  pipes  which  pass 
to  the  burner  are  so  remote  from  the  flame, 

the,  alcohol   never  becomes  heated  so  as  to  fly  off  through  the  vent-hole,  and  thus  to  cause 

greater  waste  and  danger  of  explosion."  K.  B.] 


THE   STRUCTURE   OF    FLAME. 


177 


Fig.  128. 


Fig.  129. 


exposed  to  an  easily  regulated  and  invariable  temperature  for  many  succes- 
sive hours.  Small  platinum  crucibles  may  be  ignited  to  redness  by  placing 
them  over  the  flame  on  a  little  wire  triangle.  The  arrangement  shown  in 
fig.  127,  consisting  of  a  common  Argand  gas-burner 
fixed  on  a  heavy  and  low  foot,  and  connected  with  a 
flexible  tube  of  caoutchouc  or  other  material,  is  very 
convenient. 

A  higher  temperature,  and  perfectly  smokeless  flame, 
is,  however,  obtained  by  burning  the  gas  previously 
mixed  with  air.  Such  a  flame  is  easily  produced  by 
placing  a  cap  of  wire-gauze  on  the  chimney  of  the  Ar- 
gand burner  just  described,  and  setting  fire  to  the  gas 
above  the  wire-gauze.  The  flame  does  not  penetrate 
below,  but  the  gas  in  passing  up  the  chimney  becomes 
mixed  with  air,  and  this  mixture  burns  above  the  cap 
with  a  blue,  smokeless  flame. 

Another  kind  of  burner  for  producing  a  smokeless 
flame  has  been  contrived  by  Professor  Bunsen,  and  is 
now  very  generally  used  in  chemical  laboratories.  In 
this  burner  (fig.  129)  the  gas,  supplied  by  a  flexible  tube,  t,  passes  through 
a  set  of  small  holes  into  the  box  at  a,  in  which  it  mixes  with  atmospheric 
air  entering  freely  by  a  number  of  holes  near  the 
top  of  the  box.  The  gaseous  mixture  passes  up  the 
tube  b,  and  is  inflamed  at  the  top,  where  it  burns 
with  a  tall,  blue,  smokeless  flame,  giving  very  little 
light,  but  much  heat.  By  arranging  two  or  more 
such  tubes,  together  with  an  air-box  containing  a 
sufficient  number  of  holes,  a  very  powerful  burner 
may  be  constructed. 

Considerable  improvements  in  this  form  of  burner 
have  been  made  by  Mr.  Griffin,  who  has  also  con- 
structed, on  the  same  principle,  powerful  gas-fur- 
naces, affording  heat  sufficient  for  the  decomposition 
of  silicates,  and  the  fusion  of  considerable  quantities  of  copper  or  iron.* 
The  principle  of  burning  a  mixture  of  gas  and  air  is  also  applied  in  Hof- 
manu's  gas-furnace  for  organic  analysis,  which  will  be  described  under  Or- 
ganic Chemistry. 

•The  kindling-point,  or  temperature  at  which  combustion  commences,  is 
very  different  with  different  substances  :  phosphorus  will  sometimes  take  fire 
in  the  hand ;  sulphur  requires  a  temperature  exceeding  that  of  boiling 
water;  charcoal  must  be  heated  to  redness.  Among  gaseous  bodies  the 
same  fact  is  observed :  hydrogen  is  inflamed  by  a  red-hot  wire ;  light 
carbonetted  hydrogen  requires  a  white  heat  to  effect  the  same  thing.  When 
flame  is  cooled  by  any  means  below  the  temperature  at  which  the  rapid 
oxidation  of  the  combustible  gas  occurs,  it  is  at  once  extinguished.  Upon 
this  depends  the  principle  of  Sir  H.  Davy's  invaluable  safety-lamp. 

Mention  has  already  been  made  of  the  frequent  disengagement  of  great 
quantities  of  light  carbonetted  hydrogen  gas  in  coal-mines.  This  gas, 
mixed  with  seven  or  eight  times  its  volume  of  atmospheric  air,  becomes 
highly  explosive,  taking  fire  at  a  light  and  burning  with  a  pale-blue  flame  ; 
and  many  fearful  accidents  have  occurred  from  the  ignition  of  large  quan- 
tities of  mixed  gas  and  air  occupying  the  extensive  galleries  and  workings 
of  a  mine.  Sir  H.  Davy  undertook  an  investigation  with  a  view  to  discover 
some  remedy  for  this  constantly  occurring  calamity  :  his  labors  resulted  in 
some  exceedingly  important  discoveries  respecting  flame,  which  led  to  the 
construction  of  the  lamp  which  bears  his  name. 

*  See  the  article  on  Gas-burners  and  Furnaces  in  Watts's  "Dictionary  of  Chemistry,"  ii.  782. 


178 


COMBUSTION,   AND 


When  two  vessels  filled  with  a  gaseous  explosive  mixture  are  connected 
by  a  narrow  tube,  and  the  contents  of  one  fired  by  the  electric  spark,  or 
otherwise,  the  flame  is  not  communicated  to  the  other,  provided  the  diameter 
of  the  tube,  its  length,  and  the  conducting  power  for  heat  of  its  material, 
bear  a  certain  proportion  to  each  other;  the  flame  is  extinguished  by  cool- 
ing, and  its  transmission  rendered  impossible. 

In  this  experiment,  high  conducting  power  and  diminished  diameter 
compensate  for  diminution  in  length ;  and  to  such  an  extent  can  this  be 
carried,  that  metallic  gauze,  which  may  be  looked  upon  as  a  series  of  very 
short  square  tubes  arranged  side  by  side,  when  of  sufficient  degree  of  fine- 
ness, arrests  in  the  most  complete  manner  the  passage  of  flame  in  explosive 
mixtures  depending  upon  the  inflammability  of  the  gas.  Now  the  fire-damp 
mixture  has  an  exceedingly  high  kindling-point ;  a  red  heat  does  not  cause 
inflammation ;  consequently,  the  gauze  will  be  safe  for  this  substance,  when 
flame  would  pass  in  almost  any  other  case. 

The  miner's  safety  lamp  is  merely  an  ordinary  oil-lamp,  the  flame  of 
which  is  enclosed  in  a  cage  of  wire-gauze,  made  double  at  the  upper  part, 

Fig.  130.  Fig.  131. 


containing  about  400  apertures  to  the  square  inch.  The  tube  for  supplying 
oil  to  the  reservoir  reaches  nearly  to  the  bottom  of  the  latter,  while  the 
wick  admits  of  being  trimmed  by  a  bent  wire  passing  with  friction  through 
a  small  tube  in  the  body  of  the  lamp ;  the  flame  can  thus  be  kept  burning  for 
any  length  of  time,  without  the  necessity  of  unscrewing  the  cage.  When  this 
lamp  is  taken  into  an  explosive  atmosphere,  although  the  fire-damp  may  burn 
within  the  cage  with  such  energy  as  sometimes  to  heat  the  metallic  tissue 
to  dull  redness,  the  flame  is  not  communicated  to  the  mixture  on  the  outside. 
These  effects  may  be  conveniently  studied  by  suspending  the  lamp  in  a 
large  glass  jar,  and  gradually  admitting  coal-gas  below.  The  oil-flame  is 
at  first  elongated,  and  then,  as  the  proportion  of  gas  increases,  extin- 
guished, while  the  interior  of  the  gauze  cylinder  becomes  filled  with  the 
burning  mixture  of  gas  and  air.  As  the  atmosphere  becomes  purer,  the 
wick  is  once  more  relighted.  These  appearances  are  so  remarkable  that 


CHLORINE.  179 

the  lamp  becomes  an  admirable  indicator  of  the  state  of  the  air  in  different 
parts  of  the  mine.* 

The  same  great  principle  has  been  ingeniously  applied  by  Mr.  Hemming 
to  the  construction  of  the  oxy-hydrogen  safety-jet  before  mentioned.  This 
is  a  tube  of  brass  about  four  inches  long,  filled  with  straight  pieces  of  fine 
brass  wire,  the  whole  being  tightly  wedged  together  by  a  pointed  rod,  for- 
cibly driven  into  the  centre  of  the  bundle,  (fig.  i31.)  The  arrangement  thus 
presents  a  series  of  metallic  tubes,  very  long  in  proportion  to  their  diam- 
eter, the  cooling  powers  of  which  are  so  great  as  to  prevent  the  possibility 
of  the  passage  of  flame,  even  with  oxygen  and  hydrogen.  The  jet  may  be 
used,  as  before  mentioned,  with  a  common  bladder,  without  a  chance  of 
explosion.  The  fundamental  fact  of  flame  being  extinguished  by  contact 
with  a  cold  body,  may  be  elegantly  shown  by  twisting  a  copper  wire  into  a 
short  spiral,  about  0-1  inch  in  diameter,  and  then  passing  it  cold  over  the 
flame  of  a  wax  candle;  the  latter  is  extinguished.  If  the  spiral  be  now 
heated  to  redness  by  a  spirit-lamp,  and  the  experiment  repeated,  no  such 
effect  follows. 


-    CHLORINE. 

This  substance  is  a  member  of  a  very  important  natural  group,  containing 
also  iodine,  bromine,  and  fluorine.  So  great  a  degree  of  resemblance  exists 
between  these  bodies  in  all  their  chemical  relations,  especially  between 
chlorine,  bromine,  and  iodine,  that  the  history  of  one  will  almost  serve, 
with  a  few  little  alterations,  for  that  of  the  rest. 

Chlorine f  is  a  very  abundant  substance:  in  common  salt  it  exists  in  com- 
bination with  sodium.  It  is  most  easily  prepared  by  pouring  strong  hy- 
drochloric acid  upon  finely  powdered  black  oxide  of  manganese  contained 
in  a  retort  or  flask,  arid  applying  a  gentle  heat ;  a  heavy  yellow  gas  is  dis- 
engaged, which  is  the  substance  in  question. 

It  may  be  collected  over  warm  water,  or  by  displacement:  the  mercurial 
trough  cannot  be  employed,  as  the  chlorine  rapidly  acts  upon  the  metal,  and 
becomes  absorbed. 

The  reaction  is  very  easily  explained.  Hydrochloric  acid  is  a  compound 
of  chlorine  and  hydrogen:  when  this  is  mixed  with  a  metallic  monoxide, 
double  interchange  of  elements  takes  place,  water  and  chloride  of  the  metal 
being  produced.  But  when  some  of  the  dioxides  are  substituted,  an  addi- 
tional effect  ensues  —  namely,  the  decomposition  of  a  second  portion  of 
hydrochloric  acid  by  the  oxygen  in  excess,  the  hydrogen  of  which  is  with- 
drawn and  the  chlorine  set  free. 

Hydrochloric  f  Chlorine Chlorine. 

acid          {  Hydrogen  _____      Water. 

I  Manganese  — __^  Manganese  Chloride. 

(  Oxygen 

Hydrochloric  f  Chlorine 

acid          \  Hydrogen  :::::::=*-  Water  4 

*  This  is  the  true  use  of  the  lamp  —  namely,  to  permit  the  viewer  or  superintendent,  with- 
out n-k  to  himself,  to  examine  the  state  of  the  air  in  every  part  of  the  mine;  not  to  enable 
workmen  to  continue  their  labors  in  an  atmosphere  habitually  explosive,  which  must  be  unfit 
for  human  respiration,  although  the  evil  effects  may  be  slow  to  appear.  Owners  of  coal-mines 
should  be  compelled  cither  to  adopt  efficient  means  of  ventilation,  or  to  close  workings  of  thia 
dangerous  character  altogether. 

f  From  xAwpoj,  yellowish^green,  the  name  given  to  it  by  Sir  H.  Davy. 

t        Mn02        +        4HC1        =        G32        +        MnCl2        +        20Ha 
Manganese        Hydrochloric      Chlorine.         Manganese  Water, 

dioxide.  acid.  chloride. 


180 


CHLORINE. 


Fig.  132. 


Chlorine  was  discovered  by  Scheele  in  1774,  but  its  nature  was  long  mis- 
understood. It  is  a  yellow  gaseous  body,  of  intolerably  suffocating  proper- 
ties, producing  very  violent  cough  and  irritation  when  inhaled  even  in  ex- 
ceedingly small  quantity.  It  is  soluble  to  a  considerable  extent  in  water, 
that  liquid  absorbing  at  15-5°  (60°  F.)>  about  twice  its 
volume,  and  acquiring  the  color  and  odor  of  the  gas. 
When  this  solution  is  exposed  to  light,  it  is  slowly 
changed,  by  decomposition  of  water,  into  hydrochloric 
acid,  the  oxygen  being  at  the  same  time  liberated. 
When  moist  chlorine  gas  is  exposed  to  a  cold  of  0°, 
yellow  crystals  are"  formed,  which  consist  of  a  definite 
compound  of  chlorine  and  water,  containing  35-5  parts 
of  the  former  to  90  of  the  latter. 

Chlorine  has  a  specific  gravity  of  2-47;  a  litre  of  it 
weighs  3-17344  grams;  exposed  to  a  pressure  of  about 
four  atmospheres,  it  condenses  to  a  yellow  limpid  liquid. 
Chlorine  has  but  little  attraction  for  oxygen,  its  chem- 
ical energies  being  principally  exerted  towards  hydro- 
gen and  the  metals.  A  lighted  taper  plunged  into  the 
gas,  continues  to  burn  w-ith  a  dull-red  light,  and  emits 
a  large  quantity  of  smoke,  the  hydrogen  of  the  wax 
being  alone  consumed,  and  the  carbon  separated.  If  a 
piece  of  paper  be  wetted  with  oil  of  turpentine,  and 
thrust  into  a  bottle  filled  with  chlorine,  the  chemical 
action  of  the  latter  upon  the  hydrogen  is  so  violent  as 
to  cause  inflammation,  accompanied  by  a  copious  deposit 
of  soot.  Although  chlorine  can,  by  indirect  means,  be 
made  to  combine  with  carbon,  yet  this  never  occurs 
under  the  circumstances  described. 
Phosphorus  takes  fire  spontaneously  in  chlorine,  burning  with  a  pale  and 
feebly  luminous  flame.  Several  of  the  metals,  as  copper  leaf,  powdered 
antimony,  and  arsenic,  undergo  combustion  in  the  same  manner.  A  mix- 
ture of  equal  measures  of  chlorine  and  hydrogen  explodes  with  violence  on 
the  passage  of  an  electric  spark,  or  on  the  application  of  a  lighted  taper, 
hydrochloric  acid  gas  being  formed.  Such  a  mixture  may  be  retained  in 
the  dark  for  any  length  of  time  without  change :  exposed  to  diffuse  day- 
light, the  two  gases  slowly  unite,  while  the  direct  rays  of  the  sun  induce 
instantaneous  explosion. 

The  most  characteristic  property  of  chlorine  is  its  bleaching  power;  the 
most  stable  organic  coloring  principles  are  instantly  decomposed  and  de- 
stroyed by  this  remarkable  agent:  indigo,  for  example,  which  resists  the 
action  of  strong  oil  of  vitriol,  is  converted  by  chlorine  into  a  brownish  sub- 
stance, to  which  the  blue  color  cannot  be  restored.  The  presence  of  water 
is  essential  to  these  changes,  for  the  gas  in  a  state  of  perfect  dryness  is 
incapable  even  of  affecting  litmus. 

Chlorine  is  largely  used  in  the  arts  for  bleaching  linen  and  cotton  goods, 
rags  for  the  manufacture  of  paper,  &c.  For  these  purposes,  it  is  employed, 
sometimes  in  the  state  of  gas,  sometimes  in  that  of  solution  in  water,  but 
more  frequently  in  combination  with  lime,  forming  the  substance  called 
bleaching-powder.  When  required  in  large  quantities,  it  is  often  made  by 
pouring  slightly  diluted  oil  of  vitriol  upon  a  mixture  of  common  salt  and 
manganese  oxide  contained  in  a  large  leaden  vessel.  The  decomposition 
which  ensues  may  be  thus  represented : 


CHLORINE. 


181 


Sodium 

chloride 
Sulph.  oxide 

Manganese 
dioxide. 

Sulph.  oxide. 


f  Chlorine 
1  Sodium 


-Chlorine. 

Sodium  sulphate. 


|  Manganese 
\      sulphate.' 


Chlorine  is  one  of  the  best  and  most  potent  substances  that  can  be  used 
for  the  purpose  of  disinfection,  but  its  employment  requires  care.  Bleach- 
ing-powder  mixed  with  water,  and  exposed  to  the  air  in  shallow  vessels, 
becomes  slowly  decomposed  by  the  carbonic  acid  of  the  atmosphere,  and  the 
chlorine  is  evolved:  if  a  more  rapid  disengagement  be  wished,  a  little  acid 
of  any  kind  may  be  added.  In  the  absence  of  bleaching-powder,  either  of 
the  methods  for  the  production  of  the  gas  described  may  be  had  recourse 
to,  always  taking  care  to  avoid  an  excess  of  acid. 

HYDROGEN  CHLORIDE;  HYDROCHLORIC,  CIILORHYDRIC,  OR  MURIATIC  ACID. — 
This  substance,  in  a  state  of  solution  in  water,  has  been  long  known.  The 
gas  is  prepared  with  the  utmost  ease  by  heating  in  a  flask  fitted  with  a 
cork  and  bent  tube,  a  mixture  of  common  salt  and  oil  of  vitriol  diluted  with 
a  small  quantity  of  water ;  it  must  be  collected  by  displacement,  or  over 
mercury.  It  is  a  colorless  gas,  which  fumes  strongly  in  the  air  from  con- 
densing the  atmospheric  moisture ;  it  has  an  acid,  suffocating  odor,  but  is 
much  less  offensive  than  chlorine.  Exposed  to  a  pressure  of  40  atmospheres, 
it  liquefies. 

Hydrochloric  acid  gas  has  a  density  of  1-269  compared  with  air,  or  18-25 
compared  with  hydrogen  as  unity.  It  is  exceedingly  soluble  in  water,  that 
liquid  taking  up  at  the  temperature  of  the  air  about  418  times  its  bulk. 
The  gas  and  solution  are  powerfully  acid. 

The  action  of  oil  of  vitriol  on  common  salt,  or  any  analogous  substance, 
is  thus  easily  explained :  f 


Sodium  chloride 


Sulphuric  acid 


f  Chlorine 
\  Sodium 
f Hydrogen 
4  Oxygen 
^Sulphur 


Hydrochloric 
acid. 


Sodium  sulphate. 


The  composition  of  this  substance  may  be  determined  by  synthesis :  when 
a  measure  of  chlorine  and  a  measure  of  hydrogen  are  fired  by  the  electric 
spark,  two  measures  of  hydrochloric  acid  gas  result,  the  combination  being 
unattended  by  change  of  volume.  By  weight  it  contains  35-5  parts  of 
chlorine  and  1  part  of  hydrogen. 

Solution  of  hydrochloric  acid,  the  liquid  acid  of  commerce,  is  a  very  im- 
portant preparation,  and  of  extensive  use  in  chemical  pursuits:  it  is  best 
prepared  by  the  following  arrangement:  — 

A  large  glass  flask,  containing  a  quantity  of  common  salt,  is  fitted  with  a 
cork  and  bent  tube,  in  the  manner  represented  in  fig.  132:  this  tube  passes 
through  and  below  a  second  short  tube  into  a  wide-necked  bottle,  containing 
a  little  water,  into  which  the  open  tube  dips.  A  bent  tube  is  adapted  to 
another  hole  in  the  cork  of  the  wash-bottle,  so  as  to  convey  the  purified  gas 

*      2NaCl  -f      Mn02      +      2S04H2      =      C12     +    S04Nju>  +  S04Mn      +      20Ho 

Sodium  Manganese        Hydrogen      Chlorine.        Sodium     Manganous        Water, 

chloride.  dioxide.          sulphate.                           sulphate,     sulphate. 

f      2NaCl  +         S04H2        =         2TIC1         +         SO4Na» 

Sodium  Hvdroiron             Hvdroffen               Sodium 


Sodium 
chloride. 

16 


Hydrogen 
sulphate. 


Hydrogf-n 
chloride. 


4a2 
Bodtam 

sulphate. 


182 


CHLOKINE. 


into  a  quantity  of  distilled  water,  by  which  it  is  instantly  absorbed  •  the 
joints  are  made  air-tight  by  melting  a  little  yellow  wax  over  the  corks. 

A  quantity  of  oil  of  vitriol,  about  equal  in  weight  to  the  salt,  is  then  slowly 
introduced  by  the  funnel;  the  disengaged  gas  is  at  first  wholly  absorbed  by 
the  water  in  the  wash-bottle,  but  when  this  becomes  saturated,  it  passes 
into  the  second  vessel  and  there  dissolves.  When  all  the  acid  has  been 
added,  heat  may  be  applied  to  the  flask  by  a  charcoal  chauffer,  until  its 
contents  appear  nearly  dry,  and  the  evolution  of  gas  almost  ceases,  when  the 
process  may  be  stopped.  As  much  heat  is  given  out  during  the  condensa- 
tion of  the  gas,  it  is  necessary  to  surround  the  condensing  vessel  with  cold 

Fig.  133, 


The  simple  wash-bottle,  shown  in  the  last  figure,  will  be  found  an  ex- 
ceedingly useful  contrivance  in  a  great  number  of  chemical  operations.  It 
serves  in  the  present,  and  in  many  similar  cases,  to  retain  any  liquid  or 
solid  matter  mechanically  carried  over  with  the  gas,  and  it  may  be  always 
employed  when  a  gas  of  any  kind  is  to  be  passed  through  an  alkaline  or 
other  solution.  The  open  tube  dipping  into  the  liquid  prevents  the  pos- 
sibility of  absorption,  by  which  a  partial  vacuum  would  be  occasioned,  and 
the  liquid  of  the  second  vessel  lost  by  being  driven  into  the  first. 

The  arrangement  by  which  the  acid  is  introduced  also  deserves  a  moment's 
notice.  The  tube  is  bent  twice  upon  itself,  and  a  bulb  blown  in  one  portion : 
the  liquid  poured  into  the  funnel  rises  upon  the  opposite  side  of  the  first 
bend  until  it  reaches  the  second  ;  it  then  flows  over  and  runs  into  the  flask. 
Any  quantity  can  then  be  got  into  the  latter  without  the  introduction  of  air, 
and  without  the  escape  of  gas  from  the  interior.  The  funnel  acts  also  as 
a  kind  of  safety-valve,  and  in  both  directions ;  for  if  by  any  chance  the 
delivery-tube  should  be  stopped,  and  the  issue  of  gas  prevented,  its  in- 


CHLORINE.  183 

creased  elastic  force  soon  drives  the  little  column  of  liquid  out  of  the  tube, 
the  gas  escapes,  and  the  vessel  is  saved.     On  the  other  hand,  any  absorp- 
tion within  is  quickly  compensated  by  the  entrance  of  air  through 
the  liquid  in  the  bulb. 

The  plan  employed  on  the  large  scale  by  the  manufacturer  is  the     tt 
same  in  principle  as  that  described;   he  merely  substitutes  a  large 
iron  cylinder,  or  apparatus  made  of  lead,  for  the  flask,  and  vessels 
of  stoneware  for  those  of  glass. 

On  distilling  an  aqueous  solution  of  hydrochloric  acid,  an  acid 
is  produced  boiling  at  110°  (230°  F.)  which  contains  20-22  per  cent, 
of  anhydrous  hydrochloric  acid:  a  more  concentrated  solution 
when  heated  gives  off  hydrochloric  acid  gas;  a  weaker  solution 
loses  water.  Roscoe  and  Dittmar  have  proved  that  the  composition 
of  the  distillate  varies  with  the  atmospheric  pressure;  it  cannot, 
therefore,  be  viewed  as  a  chemical  compound. 

Pure  solution  of  hydrochloric  acid  is  transparent  and  colorless : 
when  strong,  it  fumes  in  the  air  by  evolving  a  little  gas.  It  leaves 
no  residue  on  evaporation,  and  gives  no  precipitate  or  opacity  with 
diluted  solution  of  barium  chloride.  When  saturated  with  the  gas, 
it  has  a  specific  gravity  of  1-21,  and  contains  about  42  per  cent,  of 
real  acid.  The  commercial  acid,  which  is  obtained  in  immense 
quantity  as  a  secondary  product  in  the  manufacture  of  sodium  sulphate  by 
the  action  of  sulphuric  acid  upon  common  salt,  has  usually  a  yellow  color, 
and  is  very  impure,  containing  salts,  sulphuric  acid,  chloride  of  iron,  and 
organic  matter.  It  may  be  rendered  sufficiently  pure  for  most  purposes  by 
diluting  it  to  the  density  of  1-1,  which  happens  when  the  strong  acid  is 
mixed  with  its  own  bulk  or  rather  less  of  water,  and  then  distilling  it  in 
a  retort  furnished  with  a  Liebig's  condenser. 

A  mixture  of  nitric  and  hydrochloric  acids  has  long  been  known  under 
the  name  of  aqua  regia,  from  its  property  of  dissolving  gold.  When  these 
two  substances  are  heated  together,  they  both  undergo  decomposition,  nitro- 
gen tetroxide  and  chlorine  being  evolved.  This,  at  least,  appears  to  be  the 
final  result  of  the  action:  at  a  certain  stage,  however,  two  peculiar  sub- 
stances, consisting  of  nitrogen,  oxygen,  and  chlorine  (chloronitric  acid  gas* 
and  chloronitrous  gasf),  appear  to  be  formed.  It  is  only  the  chlorine  which 
attacks  the  metal. 

The  presence  of  hydrochloric  acid,  or  any  other  soluble  chloride,  is  easily 
detected  by  solution  of  silver  nitrate.  A  white  curdy  precipitate  is  pro- 
duced, insoluble  in  nitric  acid,  freely  soluble  in  ammonia,  and  subject  to 
blacken  by  exposure  to  light. 

Oxides  and  Oxacids  of  Chlorine. 

There  are  four  oxacids  of  chlorine,  which  may  be  regarded  as  oxides  of 
hydrochloric  acid;  thus: 

Composition  by  weight.f 

Chlorine.        Hydrogen.       Oxygen. 

Hydrochloric  acid          .         .         .         35-5     -f-        1 
Hypochlorous  acid     ....     35-5  1       -j-       16 

Chlorous  acid          ....         35-5     -f        1  32 

Chloric  acid 35-5     -f        *  48 

Perchloric  acid      ....         35-5     +1       +       64 

*  NOC12.  t  NOC1. 

J  Hypochlorous  acid    .        .        .        .  CIIIO 

Chlorous  acid C1H02 

Chloric  acid C1HO3 

Perchloric  acid C1HOV 


184:  CHLORINE. 

The  anhydrous  chlorine  oxides  corresponding  to  hypochlorous  and  chlorous 
acids  are  known,  namely:  * — - 

Chlorine.         Chlorine.        Oxygen. 

Chlorine  monoxide,  or  Hypochlorous  oxide  .     .     35-5     -f-     35-5     -f-     16 
Chlorine  trioxide,  or  Chlorous  oxide      ....  35-5     -j-     35-5     -j-     48 

Also  an  oxide  to  which  there  is  no  corresponding  acid,  namely :  — 

Chlorine.  Oxygen. 

Chlorine  tetroxide         .         .         .         .         2    X    35-5     -j-     64 

The  oxides  corresponding  to  chloric  and  perchloric  acid  have  not  been  ob- 
tained. 

Hypochlorous  and  chloric  acids  are  produced  by  the  action  of  chlorine  on 
certain  metallic  oxides  in  presence  of  water;  hypochlorous  and  chlorous 
acids  also  by  direct  oxidation  of  hydrochloric  acid.  Perchloric  acid  and 
chlorine  tetroxide  result  from  the  decomposition  of  chloric  acid. 

HYPOCHLOROUS  OXIDE,  ACID,  AND  SALTS.  —  The  oxide  is  best  prepared  by 
the  action  of  chlorine  gas  upon  dry  mercuric  oxide.  This  oxide,  prepared 
by  precipitation,  and  dried  by  exposure  to  a  strong  heat,  is  introduced  into 
a  glass  tube  kept  cool  and  well  washed,  dry  chlorine  gas  is  slowly  passed 
over  it.  Mercuric  chloride  and  hypochlorous  oxide  are  thereby  formed ; 
the  latter  is  collected  by  displacement.  The  reaction  by  which  it  is  pro- 
duced may  be  thus  illustrated: 

Chlorine  ___^-  Hypochlorous  oxide. 

Mercuric  f  Mercury 

oxide  \  Oxygen 

Chlorine •-  Mercuric  chloride,  j- 

The  mercuric  chloride,  however,  does  not  remain  as  such ;  it  combines 
with  another  portion  of  the  oxide  when  the  latter  is  in  excess,  forming  a 
peculiar  brown  compound,  an  oxychloride  of  mercury.  It  is  remarkable 
that  the  crystalline  mercuric  oxide  prepared  by  calcining  the  nitrate,  or  by 
the  direct  oxidation  of  the  metal,  is  scarcely  acted  upon  by  chlorine  under 
the  circumstances  described. 

Hypochlorous  oxide  is  a  pale-yellow  gaseous  body,  containing,  in  every 
two  measures,  two  measures  of  chlorine  and  one  of  oxygen,  and  is  there- 
fore analogous  in  constitution  to  water.  It  explodes,  although  with  no 
great  violence,  by  slight  elevation  of  temperature.  Its  odor  is  peculiar, 
and  quite  different  from  that  of  chlorine.  When  the  flask  or  bottle  in 
which  the  gas  is  received  is  exposed  to  artificial  cold  by  the  aid  of  a  mix- 
ture of  ice  and  salt,  the  hypochlorous  oxide  condenses  to  a  deep-red  liquid, 
slowly  soluble  in  water,  and  very  subject  to  explosion. J 

Hypochlorous  acid  is  produced  by  the  solution  of  hypochlorous  oxide  in 
water ;  also  by  passing  air  saturated  with  hydrochloric  acid  gas  through  a 
solution  of  potassium  permanganate  acidulated  with  hydrochloric  acid  and 
heated  in  a  water  bath :  the  distillate  is  a  solution  of  hypochlorous  acid, 
formed  by  oxidation  of  the  hydrochloric  acid;  thirdly,  by  decomposing  a 
metallic  hypochlorite  with  sulphuric  acid  or  other  oxacid;  fourthly,  by 
passing  chlorine  gas  into  water  holding  in  suspension  a  solution  containing 
metallic  oxides,  hydrates,  carbonates,  sulphates,  phosphates,  &c.,  the  most 

*  Chlorine  monoxide  or  Hypochlorous  oxide         ....        C120 

Chlorine  trioxide  or  Chlorous  oxide C1203 

Chlorine  tetroxide C1204. 

f  2HgO  +  CU        —        HgCVHgO  +  C120 

Mercuric  Chlorine.  Mercuric  Hypochlorous 

oxide.  oxychloride.  oxide. 

%  Pelouze  Ann.  Chim.  Phys.  [3],  vii.  112. 


CHLOROUS    OXIDE.  185 

advantageous  for  the  purpose  being  mercuric  oxide,  or  calcium  carbonate 
(chalk).* 

The  aqueous  solution  of  hypochlorous  acid  has  a  yellowish  color,  an  acid 
taste,  and  a  characteristic  sweetish  smell.  The  strong  acid  decomposes 
rapidly  even  when  kept  in  ice.  The  dilute  acid  is  more  stable,  but  is  de- 
composed by  long  boiling  into  chloric  acid,  water,  chlorine,  and  oxygen. 
Hydrochloric  acid  decomposes  it,  with  formation  of  chlorine. f  It  is  a 
very  powerful  bleaching  and  oxidizing  agent,  converting  many  of  the  ele- 
ments—  iodine,  selenium,  and  arsenic,  for  example  —  into  their  highest 
oxides,  and  at  the  same  time  liberating  chlorine. 

Metallic  hypochlorites  may  be  obtained  in  the  pure  state  by  neTitralizing 
hypochlorous  acid  with  metallic  hydrates,  such  as  those  of  sodium,  cal- 
cium, copper,  &c. ;  but  they  are  usually  prepared  by  passing  chlorine  gas 
into  solutions  of  alkalies  or  alkaline  carbonates,  or  over  the  dry  hydrates 
of  the  earth-metals  —  dry  slaked  lime,  for  example.  In  this  process  a 
metallic  chloride  is  formed  at  the  same  time.J  The  salts  thus  obtained 
constitute  the  bleaching  and  disinfecting  salts  of  commerce.  They  will  be 
more  fully  described  under  the  head  of  calcium  salts. 

CHLOROUS  OXIDE,  ACID,  AND  SALTS. — The  oxide  is  prepared  by  heating 
in  a  flask  filled  to  the  neck,  a  mixture  of  4  parts  of  potassium  chlorate 
and  3  parts  of  arsenious  acid,  or  oxide,  with  12  parts  of  nitric  acid  pre- 
viously diluted  with  4  parts  of  water.  During  the  operation,  which  must 
be  performed  in  a  water-bath,  a  greenish-yellow  gas  is  evolved,  which  is 
permanent  in  a  freezing  mixture  of  ice  and  salt,  but  liquefiable  by  extreme 
cold.  It  dissolves  freely  in  water  and  in  alkaline  solutions,  forming 
chlorous  acid  and  metallic  chlorites.  The  reaction  by  which  chlorous 
oxide  is  formed  is  somewhat  complicated.  The  arsenious  acid  deprives 
the  nitric  acid  of  part  of  its  oxygen,  reducing  it  to  nitrous  acid,  which  is 
then  reoxidized  at  the  expense  of  the  chloric  acid,  reducing  it  to  chlorous 
oxide.  $ 

Chlorous  Acid  may  be  prepared  by  condensing  chlorous  oxide  in  water, 
or  by  decomposing  a  metallic  chlorite  with  dilute  sulphuric  or  phosphoric 
acid.  Its  concentrated  solution  is  a  greenish-yellow  liquid  having  strong 
bleaching  and  oxidizing  properties.  It  does  not  decompose  carbonates, 
but  acts  strongly  with  caustic  alkalies  and  earths  to  form  chlorites. 

<  CHLORINE  TETROXIDE. — When  potassium  chlorate  is  made  into  a  paste 
with  concentrated  sulphuric  acid,  and  cooled,  and  this  paste  is  very  cau- 
tiously heated  by  warm  water  in  a  small  glass  retort,  a  deep-yellow  gas  is 
evolved,  which  is  the  body  in  question;  it  can  be  collected  only  by  dis- 
placement, since  mercury  decomposes  and  water  absorbs  it. 

Chlorine  tetroxide  has  a  powerful  odor,  quite  different  from  that  of  the 
preceding  compounds,  and  of  chlorine  itself.  It  is  exceedingly  explosive, 
being  resolved  with  violence  into  its  elements  by  a  temperature  short  of 
the  boiling-point  of  water.  Its  preparation  is,  therefore,  always  attended 
with  danger,  and  should  be  performed  only  on  a  small  scale.  It  is  com- 
posed by  measure  of  one  volume  of  chlorine  and  two  volumes  of  oxygen, 

*    COgCa      +        OH2       -f        C14        =        C02       -f       CaCl2        +        2C1IIO 

Calcium  Water.  Chlorine.          Carbon  Calcium          Hypochlorous 

carbonate.  dioxide.  chloride.  acid, 

f  C1HO    +    C1H         =      02II    —    C12. 
%  CaII202        +        C14        ="      CaCloOo"        +        CaCL>        +        OIL, 

Calcium  Chlorine.  Calcium  Calcium  Water. 

hydrate.  hypochlorite.  chloride, 

g    2C10?TI         +         2NOoH         —          2N03H        +         OIL,       -}-  C1203 

Chloric  acid.        Nitrons  acid.  Nitric  acid.  Water.         Chlorous  oxide. 

10* 


186  CHLORIC    ACID. 

condensed  into  two  volumes.*  It  may  be  liquefied  by  cold.  The  solution 
of  the  gas  in  water  bleaches. 

The  euchlorine  of  Davy,  prepared  by  gently  heating  potassium  chlorate 
with  dilute  hydrochloric  acid,  is  probably  a  mixture  of  chlorous  acid  arid 
free  chlorine. 

The  production  of  chlorine  tetroxide  from  potassium  chlorate  and  sul- 
phuric acid  depends  upon  the  spontaneous  splitting  of  the  chloric  acid  into 
chlorine  tetroxide  and  perchloric  acid,  which  latter  remains  as  u  potas- 
sium salt.f 

When  a  mixture  of  potassium  chlorate  and  sugar  is  touched  with  a 
drop  of  oil  of  vitriol,  it  is  instantly  set  on  fire,  the  chlorine  tetroxide 
disengaged  being  decomposed  by  the  combustible  substance  with  such 
violence  as  to  cause  inflammation.  If  crystals  of  potassium  chlorate  be 
thrown  into  a  glass  of  water,  a  few  small  fragments  of  phosphorus  added, 
and  then  oil  of  vitriol  poured  down  a  narrow  funnel  reaching  to  the  bot- 
tom of  the  glass,  the  phosphorus  will  burn  beneath  the  surface  of  the 
water,  by  the  assistance  of  the  oxygen  of  the  chlorine  tetroxide  disen- 
gaged. The  liquid  at  the  same  time  becomes  yellow,  and  acquires  the 
odor  of  that  gas. 

CHLORIC  ACID.  —  This  is  the  most  important  compound  of  the  series.  When 
chlorine  is  passed  to  saturation  into  a  moderately  strong  hot  solution  of 
potassium  hydrate  or  carbonate,  and  the  liquid  concentrated  by  evaporation, 
it  yields,  on  cooling,  flat  tabular  crystals  of  a  colorless  salt,  consisting  of 
potassium  chlorate.  The  mother-liquor  contains  potassium  chloride.  J 

From  potassium  chlorate,  chloric  acid  may  be  obtained  by  boiling  the 
salt  with  a  solution  of  hydrofluosilicic  acid,  which  forms  an  almost  insoluble 
potassium  salt,  decanting  the  clear  liquid,  and  digesting  it  with  a  little  silica, 
which  removes  the  excess  of  the  hydrofluosilicic  acid.  Filtration  through 
paper  must  be  avoided. 

By  cautious  evaporation,  the  acid  may  be  so  far  concentrated  as  to  assume 
a  sirupy  consistence ;  it  is  then  very  easily  decomposed.  It  sometimes  sets 
fire  to  paper,  or  other  dry  organic  matter,  in  consequence  of  the  facility 
with  which  it  is  deoxidized  by  combustible  bodies. 

The  chlorates  are  easily  recognized ;  they  give  no  precipitate  when  in 
solution  with  silver  nitrate ;  they  evolve  pure  oxygen  when  heated,  passing 
thereby  into  chlorides ;  and  they  afford,  when  treated  with  sulphuric  acid, 
the  characteristic  explosive  yellow  gas  already  described.  The  dilute  solu- 
tion of  the  acid  has  no  bleaching  power. 

PERCHLORIC  ACID.  —  When  powdered  potassium  chlorate  is  thrown  by 
small  portions  at  a  time  into  hot  nitric  acid,  a  change  takes  place  of  the  same 
description  as  that  which  happens  when  sulphuric  acid  is  used,  but  with  this 
important  difference :  that  the  chlorine  arid  oxygen,  instead  of  being  evolved 
in  a  dangerous  state  of  combination,  are  emitted  in  a  state  of  mixture.  The 
result  of  the  reaction  is  a  mixture  of  potassium  nitrate  and  perchlorate, 
which  may  be  readily  separated  by  their  difference  of  solubility. 

Perchloric  acid  is  obtained  by  distilling  potassium  perchlorate  with  sul- 
phuric acid.  Pure  perchloric  acid  is  a  colorless  liquid,  of  1-782  sp.  gr.  at 
15-5°  (60°  F.),  not  solidifying  at  —35°  (—31°  F.) ;  it  soon  becomes  colored 

*  Its  formula  is  C1204. 

t     eClOgK  +    -3S04II2  =        2C1204  +        2C104TI        +        3S04K2      +      2H«0 

Potassium  Hydrogen               Chlorine               Hydrogen               Potassium          Water. 

chlorate.  sulphate.              tetroxide.            perchlorate.             sulphate. 

J      3K20  +        C16        =        5KC1        +  C103K 

Potassium  Chlorine.  Potassium  Potassium 

oxide.  chloride.  chlorate. 


PERCHLORIC    ACID.  187 

even  if  kept  in  the  dark,  and  after  a  few  weeks  decomposes  with  explosion. 
The  vapor  of  perchloric  acid  is  transparent  and  colorless:  in  contact  with 
moist  air,  it  produces  dense  white  fumes.  The  acid,  when  cautiously  mixed 
with  a  small  quantity  of  water,  solidities  to  a  crystalline  mass,  which  is  a 
compound  of  perchloric  acid  with  one  molecule  of  water.*  When  brought 
in  contact  with  carbon,  ether,  or  other  organic  substances,  perchloric  acid 
explodes  with  nearly  as  much  violence  as  chloride  of  nitrogen. 

COMPOUND  OF  CHLORINE  AND  NITROGEN.  — When  sal-ammoniac  or  ammonia 
nitrate  is  dissolved  in  water,  and  a  jar  of  chlorine  inverted  in  the  solution, 
the  gas  is  absorbed,  and  a  deep-yellow  oily  liquid  is  observed  to  collect  upon 
the  surface  of  the  solution,  ultimately  sinking  in  globules  to  the  bottom. 
This  is  nitrogen  chloride,  the  most  dangerously  explosive  substance  known. 
The  following  is  the  safest  method  of  conducting  the  experiment:  — 

A  somewhat  dilute  and  tepid  solution  of  pure  sal-ammoniac  in  distilled 
water  poured  into  a  clean  basin,  and  a  bottle  of  chlorine,  the  neck  of  which 
is  quite  free  from  grease,  inverted  into  it.  A  shallow  and  heavy  leaden  cup 
is  placed  beneath  the  mouth  of  the  bottle  to  collect  the  product.  When 
enough  has  been  obtained,  the  leaden  vessel  may  be  withdrawn  with  its 
dangerous  contents,  the  chloride  remaining  covered  with  a  stratum  of  water. 
The  operator  should  protect  his  face  with  a  strong  wire-gauze  mask  when 
experimenting  upon  this  substance. 

The  change  may  be  explained  by  the  following  diagram:  — 

Chlorine __— ^Nitrogen  chloride. 

Chlorine ^^  ^-"""^^- Hydrochloric  acid. 

!l  Nitrogen         ^ 
\  Hydrogen  — ' 
Hydrochloric  acid  —  —  Hydrochloric  acid.f 

Nitrogen  chloride  is  very  volatile,  and  its  vapor  is  exceedingly  irritating 
to  the  eyes.  It  has  a  specific  gravity  of  1-653.  It  may  be  distilled  at  71° 
(160°  F.),  although  the  experiment  is  attended  with  great  danger.  Between 
93°  (200°  F.)  and  105°  (221°  F.)  it  explodes  with  the  most  fearful  violence. 
Contact  with  almost  any  combustible  matter,  as  oil  or  fat  of  any  kind,  de- 
termines the  explosion  at  common  temperatures ;  a  vessel  of  porcelain,  glass, 
or  even  of  cast-iron,  is  broken  to  pieces,  and  the  leaden  cup  receives  a  deep 
indentation.  This  body  has  usually  been  supposed  to  contain  nitrogen  and 
chlorine  in  the  proportion  of  14  parts  of  the  former  to  106-5  parts  of  the 
latter,  but  recent  experiments  upon  the  corresponding  iodine  compound 
(p.  191)  induce  a  belief  that  it  contains  hydrogen.  J 

CHLORINE  AND  CARBON.  —  Several  compounds  of  chlorine  and  carbon  are 
known. g  They  are  obtained  indirectly  by  the  action  of  chlorine  upon 
certain  organic  compounds,  and  will  be  described  under  Organic  Chemistry. 

*  C104H  +  OH2. 

f      NH4C1     +  6C1     -        NC13        +        4IIC1 

Ammonium        Chlorine        Nitrogen         Hydrochloric 

chloride.  trichloride.  acid. 

%  Instead  of  NC13,  it  may  in  reality  be  NHC12,  or  NHaCl. 
g  C2C12,  C2C14,  C2C16)  and  CC14. 


188  BROMINE.  —  IODINE. 


BROMINE, 

BROMINE*  was  discovered  by  Balard  in  1826.  It  is  found  in  sea-water, 
and  is  a  frequent  constituent  of  saline  springs,  chiefly  as  magnesium  bro- 
mide :  a  celebrated  spring  of  the  kind  exists  near  Kreuznach  in  Prussia. 
Bromine  may  be  obtained  pure  by  the  following  process,  which  depends 
upon  the  fact  that  ether,  agitated  with  an  aqueous  solution  of  bromine, 
removes  the  greater  part  of  that  substance. 

The  mother-liquor,  from  which  the  less  soluble  salts  have  separated  by 
crystallization,  is  exposed  to  a  stream  of  chlorine,  and  then  shaken  up 
with  ether;  the  chlorine  decomposes  the  magnesium  bromide,  and  the 
ether  dissolves  the  bromine  thus  set  free.  On  standing,  the  ethereal  solu- 
tion, having  a  fine  red  color,  separates,  and  may  be  removed  by  a  funnel 
or  pipette.  Caustic  potash  is  then  added  in  excess,  and  heat  applied  ; 
potassium  bromide  and  bromate  are  formed.  The  solution  is  evaporated 
to  dryness,  and  the  saline  matter,  after  ignition  to  redness  to  decompose 
the  bromate,  is  heated  in  a  small  retort  with  manganese  dioxide  and  sul- 
phuric acid  diluted  with  a  little  water,  the  neck  of  the  retort  being 
plunged  into  cold  water.  The  bromine  volatilizes  in  the  form  of  a  deep- 
red  vapor,  which  condenses  into  drops  beneath  the-  liquid. 

Bromine  is  at  common  temperatures  a  red  thin  liquid  of  an  exceedingly 
intense  color,  and  very  volatile;  it  freezes  at  about  — 7°  (19°  F. ),  and 
boils  at  63°  (143°  F.)  The  density  of  the  liquid  is  2-976,  and  that  of  the 
vapor  5  -54  compared  with  air,  and  80  compared  with  hydrogen.  The 
odor  of  bromine  is  very  suffocating  and  offensive,  much  resembling  that 
of  iodine,  but  more  disagreeable.  It  is  slightly  soluble  in  water,  more 
freely  in  alcohol,  and  most  abundantly  in  ether.  The  aqueous  solution 
bleaches. 

HYDROGEN  BROMIDE,  or  HYDROBROMIC  ACID.-}- — This  substance  bears 
the  closest  resemblance  to  hydriodic  acid:  it  has  the  same  constitution  by 
volume,  very  nearly  the  same  properties,  and  may  be  prepared  by  means 
exactly  similar,  substituting  the  one  body  for  the  other  (see  page  189). 
The  solution  of  hydrobromic  acid  has  also  the  power  of  dissolving  a  large 
quantity  of  bromine,  thereby  acquiring  a  red  tint.  Hydrobromic  acid 
contains  by  weight  80  parts  bromine  and  1  part  hydrogen. 

BROMIC  AciD.J  —  Caustic  alkalis  in  presence  of  bromine  undergo  the 
same  change  as  with  chlorine,  a  metallic  bromide  and  bromate  being  pro- 
duced: these  may  often  be  separated  by  the  inferior  solubility  of  the  lat- 
ter. Bromic  acid,  obtained  from  barium  bromate,  closely  resembles  chloric 
acid;  it  is  easily  decomposed.  The  bromates,  when  heated,  lose  oxygen  and 
become  bromides. 

A  hypobromous  acid  corresponding  to  hypochlorous  acid  is  likewise 
known. 


IODINE. 

This  element  was  first  noticed  in  1812  by  M.  Courtois,  of  Paris.  Minute 
traces  are  found  in  combination  with  sodium  or  potassium  in  sea-water, 
and  occasionally  a  much  larger  proportion  in  that  of  certain  mineral 
springs.  It  seems  to  be  in  some  way  beneficial  to  many  marine  plants,  as 

*  From  /3f>w/*0f,  a  noisome  smell :  a  very  appropriate  term, 
f  IIBr.  J  Br03H. 


IODINE.  189 

these  latter  have  the  power  of  abstracting  it  from  the  surrounding  water, 
and  accumulating  it  in  their  tissues.  It  is  from  this  source  that  all  the 
iodine  of  commerce  is  derived.  It  has  lately  been  found  in  minute  quan- 
tity in  some  aluminous  slates  of  Sweden,  arid  in  several  varieties  of  coal 
and  turf. 

Kdp,  or  the  half-vitrified  ashes  of  sea-weeds,  prepared  by  the  inhabi- 
tants of  the  Western  Islands  and  the  northern  shores  of  Scotland  and  Ire- 
land, is  treated  with  water,  and  the  solution  filtered.  The  liquid  is  then 
concentrated  by  evaporation  until  it  is  reduced  to  a  very  small  volume, 
the  sodium  chloride,  sodium  carbonate,  potassium  chloride,  and  other 
salts  being  removed  as  they  successively  crystallize.  The  dark-brown 
mother-liquor  left  contains  very  nearly  the  whole  of  the  iodine,  as  iodide  of 
sodium,  magnesium,  &c. :  this  is  mixed  with  sulphuric  acid  and  manganese 
dioxide,  and  gently  heated  in  a  leaden  retort,  when  the  iodine  distils  over 
and  condenses  in  the  receiver.  The  theory  of  the  operation  is  exactly 
analogous  to  that  of  the  preparation  of  chlorine;  in  practice,  however,  it 
requires  careful  management,  otherwise  the  impurities  present  in  the 
solution  interfere  with  the  general  result.* 

The  manganese  is  not  absolutely  necessary;  potassium  or  sodium  iodide, 
heated  with  an  excess  of  sulphuric  acid,  evolves  iodine.  This  effect  is 
due  to  a  secondary  action  between  the  hydriodic  acid  first  produced  and 
the  excess  of  the  sulphuric  acid,  in  which  both  suffer  decomposition, 
yielding  iodine  water,  and  sulphurous  acid. 

Iodine  crystallizes  in  plates  or  scales  of  a  bluish-black  color  and  imper- 
fect metallic  lustre,  resembling  that  of  plumbago:  the  crystals  are  some- 
times very  large  and  brilliant.  Its  density  is  4-918.  It  melts  at  107° 
(2i>5°  p.),  and  boils  at  175°  (347°  F.),  the  vapor  having  an  exceedingly 
beautiful  violet  color.f  It  is  slowly  volatile,  however,  at  common  temper- 
atures, and  exhales  an  odor  much  resembling  that  of  chlorine.  The  den- 
sity of  the  vapor  is  8  716  compared  with  air,  127  compared  with  hydro- 
gen. Iodine  requires  for  solution  about  7000  parts  of  water,  which  never- 
theless acquires  a  brown  color;  in  alcohol  it  is  much  more  freely  soluble. 
Solutions  of  hydriodic  acid  and  the  iodides  of  the  alkaline  metals  also 
dissolve  a  large  quantity :  these  solutions  are  not  decomposed  by  water, 
which  is  the  case  with  the  alcoholic  tincture 

Iodine  stains  the  skin,  but  not  permanently ;  it  has  a  very  energetic 
action  upon  the  animal  system,  and  is  much  used  in  medicine. 

One  of  the  most  characteristic  properties  of  iodine  is  the  production  of 
a  splendid  blue  color  by  contact  with  starch.  The  iodine  for  this  purpose 
must  be  free  or  uncombined.  It  is  easy,  however,  to  make  the  test  available 
for  the  purpose  of  recognizing  the  presence  of  the  element  in  question 
when  a  soluble  iodide  is  suspected  ;  it  is  only  necessary  to  add  a  very  small 
quantity  of  chlorine-water,  when  the  iodine,  being  displaced  from  combi- 
nation, becomes  capable  of  acting  upon  the  starch. 

HYDROGEN  IODIDE,  or  HYDRIODIC  ACID.  —  The  simplest  process  for  pre- 
paring hydriodic  acid  gas  is  to  introduce  into  a  glass  tube,  sealed  at  one 
extremity,  a  little  iodine,  then  a  small  quantity  of  roughly  powdered  glass 
moistened  with  water,  upon  this  a  few  fragments  of  phosphorus,  and  lastly 
more  glass:  this  order  of  iodine,  glass,  phosphorus,  glass,  is  repeated  until 
the  tube  is  half  or  two-thirds  filled.  A  cork  and  narrow  bent  tube  are 
then  fitted,  and  gentle  heat  applied.  The  gas  is  best  collected  by  displace- 
ment of  air.  The  experiment  depends  on  the  formation  of  an  iodide  of 

*-»KI       -f       Mn02       +       2S04IL,     =       I.2      +       S04K2       +       S04Mn       +       20IT2 
Potassium       Manganese          Hydrogen        Iodine.        Potassium        Manganese  Water, 

iodide.  dioxide.  sulphate  sulphate.  sulphate. 

f  Whence  the  name,  from  fu<5>7?,  violet-colored. 


190  IODINE. 

phosphorus  and  its  subsequent  decomposition  by  water,  whereby  hydrogen 
phosphite,  or  phosphorous  acid,  and  hydrogen  iodide  are  produced.*  The 
glass  merely  serves  to  moderate  the  violence 
Fi0- 135-  of  the  action  of  the  iodine  upon  the  phos- 

phorus. 

Hydriodic  acid  gas  greatly  resembles  the 
corresponding  chlorine  compound;  it  is  color- 
less, and  highly  acid ;  it  fumes  in  the  air, 
and  is  very  soluble  in  water.  Its  density  is 
about  4-4  compared  with  air,  64  compared 
with  hydrogen.  By  weight,  it  is  composed 
of  127  parts  iodine  and  1  part  hydrogen; 
and  by  measure  of  equal  volumes  of  iodine 
vapor  and  hydrogen  united  without  con- 
densation. 

Solution  of  hydriodic  acid  may  be  pre- 
pared by  a  process  much  less  troublesome  than 
the  above.  Iodine  in  fine  powder  is  suspended 
in  water,  and  a  stream  of  washed  hydrogen 
sulphide  passed  through  the  mixture;  sul- 
phur is  deposited,  and  the  iodine  converted 
into  hydriodic  acid.  When  the  liquid  has  become  colorless,  it  is  heated,  to 
expel  the  excess  of  hydrogen  sulphide,  and  filtered.  The  solution  cannot 
be  kept  long,  especially  if  it  be  concentrated ;  the  oxygen  of  the  air  grad- 
ually decomposes  the  hydriodic  acid,  and  iodine  is  set  free,  which,  dissolving 
in  the  remainder,  communicates  to  it  a  brown  color. 

Compounds  of  Iodine  and  Oxygen. 
The  most  important  of  these  are  the  iodic  and  periodic  oxides. 

Composition  by  weight.f 

Iodine.        Oxygen. 

Iodic  oxide 127  40 

Periodic  oxide     ......          127  56 

Both  these  are  acid  oxides,  uniting  with  water  and  metallic  oxides,  and 
forming  salts  called  iodates  and  periodates.  The  composition  of  the  hydro- 
gen salts  is  as  follows  :  J  — 

Iodine.  Oxygen.  Hydrogen.  Iodic  oxide.  Water. 

Hydrogen  lodate  or  Iodic  acid  127  -f  48    -f    1      or       834     -f     18 

Hydrogen  Periodate  or  Periodic  acid  127  -j-  56    -f    1      or       386     +     18 

Iodic  acid  may  be  prepared  by  the  direct  oxidation  of  iodine  with  nitric 
acid  of  specific  gravity  1-5;  5  parts  of  dry  iodine  with  200  parts  of  nitric 
acid  are  kept  at  a  boiling  temperature  for  several  hours,  or  until  the  iodine 
has  disappeared.  The  solution  is  then  cautiously  distilled  to  dryness,  and 
the  residue  dissolved  in  water  and  made  to  crystallize. 

Iodic  acid  is  a  very  soluble  substance ;  it  crystallizes  in  colorless,  six- 
sided  tables.  At  107°  (224°  F.)  it  is  resolved  into  water  and  iodic  oxide, 
which  forms  tabular  rhombic  crystals,  and  when  heated  to  the  temperature 
of  boiling  olive  oil,  is  completely  resolved  into  iodine  and  oxygen.  The 
solution  of  iodic  acid  is  readily  deoxidized  by  sulphurous  acid.  The  iodates 

*          p2       +       i6       +  eoilo  =             6HI          +             2P03H3 

Phosphorus.      Iodine.  Water.             Hydrogen  iodide.  Hydrogen  phosphite, 
f  I205  and  laOy. 

J  I206.OH2        =  2I03H;                  I207.OH2        =  2I04H. 


IODINE.  191 

much  resemble  the  chlorates:  that  of  potassium  is  decomposed  by  heat  into 
potassium  iodide  and  oxygen  gas. 

Periodic  Acid.  —  When  solution  of  sodium  iodate  is  mixed  with  caustic 
soda,  and  a  current  of  chlorine  transmitted  through  the  liquid,  two  salts 
are  formed  —  namely,  sodium  chloride  and  a  compound  of  sodium  periodate 
with  sodium  hydrate,  which  is  sparingly  soluble.*  This  is  separated,  con- 
verted into  a  silver-salt,  and  dissolved  in  nitric  acid  :  the  solution  yields,  on 
evaporation,  crystals  of  yellow  silver  periodate,  from  which  the  acid  may 
be  separated  by  the  action  of  water,  which  resolves  the  salt  into  free  acid 
and  insoluble  basic  periodate. 

Periodic  acid  crystallizes  from  its  aqueous  solution  in  deliquescent 
oblique  rhombic  prisms,  which  melt  at  130°  (266°  F.),  and  are  resolved  at 
170°  (338°  F.)  into  water  and  a  white  mass  of  periodic  oxide,  which  at  180° 
or  190°  (356°  —  374°  F.)  gives  off  oxygen  with  great  rapidity,  and  leaves 
iodic  oxide. 

The  solution  of  periodic  acid  is  reduced  by  many  organic  substances, 
and  instantly  by  hydrochloric  acid,  sulphurous  acid,  and  hydrogen  sul- 
phide. With  hydrochloric  acid  it  forms  water,  iodine  chloride,  and  free 
chlorine.  The  metallic  periodates  are  resolved  by  heat  into  oxygen  and 
metallic  iodide. 

Compounds  of  Iodine  and  Nitrogen.  —  When  finely  powdered  iodine  is  put 
into  caustic  ammonia,  it  is  in  part  dissolved,  giving  a  deep-brown  solution, 
and  the  residue  is  converted  into  a  black  powder,  called  nitrogen  iodide.\ 
The  brown  liquid  consists  of  hydriodic  acid,  holding  iodine  in  solution, 
and  is  easily  separated  from  the  solid  product  by  a  filter.  The  latter, 
while  still  wet,  is  distributed  in  small  quantities  upon  separate  pieces  of 
bibulous  paper,  and  left  to  dry  in  the  air. 

Nitrogen  iodide  is  a  black  insoluble  powder,  which,  when  dry,  explodes 
with  the  slightest  touch  —  even  that  of  a  feather  —  and  sometimes  without 
any  obvious  cause.  The  explosion  is,  however,  not  nearly  so  violent  as 
that  of  nitrogen  chloride,  and  is  attended  with  the  production  of  violet 
fumes  of  iodine.  According  to  Dr.  Gladstone,  this  substance  contains  hy- 
drogen, and  may  be  viewed  as  ammonia  in  which  two  thirds  of  the  hy- 
drogen are  replaced  by  iodine.|  According  to  the  researches  of  Bunsen, 
it  must  be  viewed  as  a  combination  of  nitrogen  tri-iodide  with  ammonia.  § 
It  appears,  however,  that  the  substance  called  nitrogen  iodide  varies  in 
composition.  Gladstone,  by  changing  the  mode  of  preparation,  obtained 
several  compounds  of  nitrogen  tri-iodide  with  ammonia. 

Compounds  of  Iodine  and  Chlorine.  —  Iodine  readily  absorbs  chlorine  gas, 
forming,  when  the  chlorine  is  in  excess,  a  solid  yellow  compound,  and 
when  the  iodine  preponderates,  a  brown  liquid.  The  solid  iodide  is 
decomposed  by  water,  yielding  hydrochloric  and  iodic  acids.  || 

Another  definite  compound  is  formed  by  heating  in  a  retort  a  mixture 
of  1  part  iodine  and  4  parts  potassium  chlorate  ;  oxygen  gas  and  iodine 
chloride  are  disengaged,  and  the  latter  may  be  condensed  by  suitable 
means.  Potassium  iodate  and  perchlorate  remain  in  the  retort. 

This  iodine  chloride  is  a  yellow  oily  liquid,  of  suffocating  smell  and 
astringent  taste  ;  it  is  soluble  in  water  and  alcohol  without  decomposition. 
It  probably  consists  of  127  parts  iodine  and  35-5  parts  chlorine.^ 


*   HtyVa      +        SXaTIO      +       C12        =  2Na.Cl        + 

Sodium  Sodium          Chlorine  Sodium  Basic  sodium 

iodate.  hydrate.  chloride.  periodate. 

t  NI3.  t  NHIfr  g  NI3.N% 

||  Hence  it  is  doubtless  ICI5.  f  Id. 


192  FLUORINE. 


FLUORINE. 

This  element  has  never  been  isolated  —  at  least,  in  a  state  fit  for  exam- 
ination; its  properties  are  consequently  in  great  measure  unknown; 
but  from  the  observations  made,  it  is  presumed  to  be  gaseous,  and  to  pos- 
sess color,  like  chlorine.  The  compounds  containing  fluorine  can  be  easily 
decomposed,  and  the  element  transferred  from  one  body  to  another;  but 
its  intense  chemical  energies  towards  the  metals  and  towards  silicium,  a 
component  of  glass,  have  hitherto  baffled  all  attempts  to  obtain  it  pure  in 
the  separate  state.  As  calcium  fluoride,  it  exists  in  small  quantities  in 
many  animal  substances,  such  as  bones.  Several  chemists  have  endeavored 
to  obtain  it  by  decomposing  silver  fluoride  by  means  of  chlorine  in  vessels 
of  fluor-spar,  but  even  these  experiments  have  not  led  to  a  decisive  result. 

HYDROGEN  FLUORIDE,  or  HYDROFLUORIC  ACID.*  —  When  powdered  cal- 
cium fluoride  (fluor-spar)  is  heated  with  concentrated  sulphuric  acid  in  a 
retort  of  platinum  or  lead  connected  with  a  carefully  cooled  receiver  of 
the  same  metal,  a  very  volatile  colorless  liquid  is  obtained,  which  emits 
copious  white  and  highly  suffocating  fumes  in  the  air.  This  was  formerly 
believed  to  be  the  acid  in  the  anhydrous  state.  Louyet,  however,  states 
that  it  still  contains  water,  and  that  hydrofluoric  acid,  like  hydrochloric 
acid,  when  anhydrous,  is  a  gas.  The  anhydrous  acid  may  be  prepared, 
according  to  Fremy,  by  distilling  hydrogen  and  potassium  fluoride  in  a 
platinum  vessel.  The  acid  is  gaseous  at  ordinary  temperatures.  In  a 
frigorific  mixture  it  exists  as  a  liquid,  which  acts  violently  on  water  and 
evolves  white  fumes. 

When  hydrofluoric  acid  is  put  into  water,  it  unites  with  the  latter  with 
great  violence:  the  dilute  solution  attacks  glass  with  great  facility.  The 
concentrated  acid,  dropped  upon  the  skin,  occasions  deep  and  malignant 
ulcers,  so  that  great  care  is  requisite  in  its  management.  Hydrofluoric 
acid  contains  19  parts  fluorine  arid  1  part  hydrogen. 

In  a  diluted  state,  this  acid  is  occasionally  used  in  the  analysis  of  siliceous 
minerals,  when  alkali  is  to  be  estimated:  it  is  employed,  also,  for  etching 
on  glass,  for  which  purpose  the  acid  may  be  prepared  in  vessels  of  lead, 
that  metal  being  but  slowly  attacked  under  these  circumstances.  The 
vapor  of  the  acid  is  also  very  advantageously  applied  to  the  same  object 
in  the  following  manner :  The  glass  to  be  engraved  is  coated  with  etching- 
ground  or  wax,  and  the  design  traced  in  the  usual  way  with  a  pointed 
instrument.  A  shallow  basin  made  by  beating  up  a  piece  of  sheet-lead  is 
then  prepared,  a  little  powdered  fluor-spar  placed  in  it,  and  enough  sul- 
phuric acid  added  to  form  with  the  latter  a  thin  paste.  The  glass  is 
placed  upon  the  basin,  with  the  waxed  side  downward,  and  gentle  heat 
applied  beneath,  which  speedily  disengages  the  vapor  of  hydrofluoric  acid, 
lu  a  very  few  minutes,  the  operation  is  complete:  the  glass  is  then  re- 
moved and  cleaned  by  a  little  warm  oil  of  turpentine.  When  the  experi- 
ment is  successful,  the  lines  are  very  clean  and  smooth. 

No  combination  of  fluorine  and  oxygen  has  yet  been  discovered. 

*HP 


SULPHUR. 


193 


SULPHUB. 

This  is  an  elementary  body  of  great  importance  and  interest.  It  is 
often  found  in  the  free  state  in  connection  with  deposits  of  gypsum  and 
rock-salt;  its  occurrence  in  volcanic  districts  is  probably  accidental. 
Sicily  furnishes  a  large  proportion  of  the  sulphur  employed  in  Europe. 
In  a  state  of  combination  with  iron  and  other  metals,  and  as  sulphuric  acid 
united  to  lime  and  magnesia,  it  is  also  abundant. 

Pure  sulphur  is  a  pale-yellow  brittle  solid,  of  well-known  appearance. 
It  melts  when  heated,  and  distils  over  unaltered,  if  air  be  excluded.  The 
crystals  of  sulphur  exhibit  two  distinct  and  incompatible  forms  —  namely, 
first,  an  octohedron  with  rhombic  base  (fig.  136),  which  is  the  figure  of 
native  sulphur,  and  that  assumed  when  sulphur  separates  from  solution  at 
common  temperatures,  as  when  a  solution  of  sulphur  in  carbon  bisulphide 
is  exposed  to  slow  evaporation  in  the  air ;  and,  secondly,  a  lengthened  prism 
having  no  relation  to  the  preceding:  this  happens  when  a  mass  of  sulphur 
is  melted,  and,  after  partial  cooling,  the  crust  on  the  surface  is  broken  and 
the  fluid  portion  poured  out.  Fig.  137  shows  the  result  of  such  an  experi- 
ment. 


ig.  136. 


Fig.  137. 


The  specific  gravity  of  sulphur  varies  according  to  the  form  in  which  it 
is  crystallized.  The  octohedral  variety  has  the  specific  gravity  2-045;  the 
prismatic  variety  the  specific  gravity  1-982. 

Sulphur  melts  at  111°  (232°  F.)  (at  114-5°,  according  to  Brodie):  at  this 
temperature  it  is  of  the  color  of  amber,  and  thin  and  fluid  as  water;  when 
further  heated,  it  begins  to  thicken,  and  to  acquire  a  deeper  color;  and 
between  221°  (430°  F.)  and  249°  (480°  F.)  it  is  so  tenacious  that  the  vessel 
in  which  it  is  contained  may  be  inverted  for  a  moment  without  the  loss  of 
its  contents.  If  in  this  state  it  be  poured  into  water,  it  retains  for  many 
hours  a  remarkably  soft  and  flexible  condition,  which  should  be  looked  upon 
as  the  amorphous  state  of  sulphur.  After  a  while  it  again  becomes  brittle 
and  crystalline.  From  the  temperature  last  mentioned  to  the  boiling-point 
—  about  400°  (792°  F.)  —  sulphur  again  becomes  thin  and  liquid.  In  the 
preparation  of  commercial  flowers  of  sulphur,  the  vapor  is  conducted  into 
a  large  cold  chamber,  where  it  condenses  in  minute  crystals.  The  specific 
gravity  of  sulphur  vapor  is  2-22,  referred  to  that  of  air  as  unity,  or  32  com- 
pared with  that  of  hydrogen  (Deville). 

Sulphur  is  insoluble  in  water  and  alcohol ;  oil  of  turpentine  and  the  fat 
oils  dissolve  it,  but  the  best  substance  for  the  purpose  is  carbon  bisulphide. 
In  its  chemical  relations  sulphur  bears  great  resemblance  to  oxygen:  to  very 
many  oxides  there  are  corresponding  sulphides,  and  the  sulphides  often 
unite  among  themselves,  forming  crystallizable  compounds  analogous  to 
oxysalts. 
17 


194  SULPHUB. 

Sulphur  is  remarkable  for  the  great  number  of  modifications  which  it  is 
capable  of  assuming.  Of  these,  however,  there  are  two  principal  well- 
characterized  varieties,  one  soluble,  and  the  other  insoluble  in  carbon  bi- 
sulphide, and  many  minor  modifications.  The  soluble  variety  is  distinguished 
by  Berth  elot*  by  the  name  of  electro-negative  sulphur,  because  it  is  the  form 
which  appears  at  the  positive  pole  of  the  voltaic  battery  during  the  decom- 
position of  an  aqueous  solution  of  hydrogen  sulphide,  and  is  separated  from 
the  combinations  of  sulphur  with  the  electro-positive  metals.  The  insolu- 
ble variety  is  distinguished  as  electro-positive  sulphur,  because  it  is  the  form 
which  appears  at  the  negative  pole  during  the  electric  decomposition  of 
sulphurous  acid,  and  separates  from  compounds  of  sulphur  with  the  electro- 
negative elements,  chlorine,  bromine,  oxygen,  &c. 

The  principal  modifications  of  soluble  sulphur  are  the  octohedral  and 
prismatic  varieties  already  mentioned,  and  an  amorphous  variety  which  is 
precipitated  as  a  greenish-white  emulsion,  known  as  milk  of  sulphur  on 
adding  an  acid  to  a  dilute  solution  of  an  alkaline  polysulphide,  such,  for 
example,  as  is  obtained  by  boiling  sulphur  with  milk  of  lime.f  This  amor- 
phous sulphur  changes  by  keeping  into  a  mass  of  minute  octohedral  crystals. 
Sublimed  sulphur  appears  also  to  be  allied  to  this  modification,  but  it  always 
contains  a  small  portion  of  one  of  the  insoluble  modifications. 

The  chief  modifications  of  insoluble  sulphur  are :  1.  The  amorphous  in- 
soluble variety,  obtained  as  a  soft  magma  by  decomposing  chlorine  bisul- 
phide with  water,  or  by  adding  dilute  hydrochloric  acid  to  the  solution  of  a 
hyposulphite.  J  2.  The  plastic  sulphur  already  mentioned  as  obtained  by 
pouring  viscid  melted  sulphur  into  water.  A  very  similar  variety  is  pro- 
duced by  boiling  metallic  sulphides  with  nitric  or  nitro-muriatic  acid. 

Magnus  g  obtained  a  black  modification  of  sulphur  by  repeatedly  heating 
sulphur  to  300°  (572°  F.),  cooling  suddenly,  and  exhausting  with  carbon  bi- 
sulphide; and  this  black  sulphur,  heated  to  a  temperature  between  130° 
and  150°,  passed  into  a  red  modification.  According  to  Mitscherlich,  how- 
ever, pure  sulphur  does  not  exhibit  these  modifications ;  but  various  highly 
colored  products  may  be  obtained  by  melting  sulphur  with  small  quantities 
of  fatty  matters.  Even  the  grease  imparted  by  touching  sulphur  with  the 
fingers  is  sufficient  to  alter  its  color  considerably  when  melted. 

When  solutions  of  hydrogen  sulphide  and  ferric  chloride  are  mixed 
together,  a  blue  precipitate  is  sometimes  formed,  which  is  said  to  be  a 
peculiar  modification  of  sulphur. 

Compounds  of  Sulphur  and  Oxygen. 

There  are  two  oxides  of  sulphur  whose  names  and  composition  are  as 
follows : 

Composition  by  weight. 


Sulphur.        Oxygen. 

Sulphur  dioxide  or  Sulphurous  oxide       .         .         .     32      -f-      32 
Sulphur  trioxide  or  Sulphuric  oxide     .         .         .         32      -f      48 

Both  these  oxides  unite  with  water  and  metallic  oxides,  or  the  elements 
thereof,  producing  salts;  those  derived  from  sulphurous  oxide  are  called 

*  Ann.  Chim  Phys.  [3],  xlix.  430. 

f           CaS5        +        2HC1          =  CaCl2  +       SH2         -f        S4 

Calcium         Hydrochloric  Calcium           Hydrogen          Sulphur, 

pentasulphide.         acid.  chloride.           sulphide. 

%          2C12S2        +        30H2        =        4IIC1  +        S203H2        +        83 

Chlorine  Water.  Hydrochloric    Hypo'sulphurous    Sulphur, 

bisulphide.  acid.                     acid. 
g  Poggendorff  s  Annajen,  xcii.  308. 


SULPHUR.  195 

sulphites,  and  those  derived  from  sulphuric  acid,  sulphates.     The  composi- 
tion of  the  hydrogen  salts,  or  acids,  is  as  follows :  * 

Sulphur.      Oxygen.      Hydrogen.      Sulphurous  oxide.  Water. 
Hydrogen  Sulphite     |         32     +     48+2         =  64          +18 

or  Sulphurous  acid  / 

Sulphuric  oxide.    Water. 
Hydrogen  Sulphate,    j         32     +     64     +      2        =  80          +18 

or  Sulphuric  acid     / 

The  replacement  of  half  or  the  whole  of  the  hydrogen  in  these  acids, 
by  metals,  gives  rise  to  metallic  sulphites  and  sulphates. 

There  are  also  several  acids  of  sulphur,  with  their  corresponding  metal- 
lic salts,  to  which  there  are  no  corresponding  anhydrous  oxides,  viz. : 

1.  Hyposulphurous  or  Thiosulphuric  Acid,  having  the  composition  of  sul- 
phuric acid  in  which  one  fourth  of  the  oxygen  is  replaced  by  sulphur.f 
Its  composition  by  weight  is : 

Sulphur.  Oxygen.  Hydrogen. 

04  +  48  +  2 

2.  A  series  of  acids  called  Polythionic  Acids,\  in  which  the  same  quanti- 
ties of  oxygen  and  hydrogen  are  united  with  quantities  of  sulphur  in  the 
proportion  of  the  numbers  2.  3,  4,  5,g  viz.: 

Sulphur.    Oxygen.      Hydrogen. 
Dithionic,  or  Hyposulphuric  acid     .         .         64     +     96+2 

Trithionic  acid 96     +     96     +       2 

Tetrathionic  acid 128     +     96     +       2 

Pentathionic  acid         .         .         .  .  160     +     96     +       2 

SULPHUR  DIOXIDE,  or  SULPHUROUS  OXIDE.  —  This  is  the  only  product  of 
the  combustion  of  sulphur  in  dry  air  or  oxygen  gas.  It  is  most  conveniently 
prepared  by  heating  sulphuric  acid  with  metallic  mercury  or  copper  clip- 
pings ;  a  portion  of  the  acid  is  decomposed,  one  third  of  the  oxygen  of  the 
sulphuric  oxide  being  transferred  to  the  metal,  while  the  sulphuric  oxide 
is  reduced  to  sulphurous  oxide  which  escapes  as  gas.||  Another  very  simple 
method  of  preparing  sulphurous  oxide  consists  in  heating  concentrated  sul- 
phuric acid  with  sulphur ;  a  very  regular  evolution  of  sulphurous  oxide  is 
thus  obtained.  Sulphurous  oxide  is  a  colorless  gas,  having  the  peculiar 
suffocating  odor  of  burning  brimstone  ;  it  instantly  extinguishes  flame,  and 
is  quite  irrespirible.  Its  density  is  2-21;  a  litre  weighs  2-8605  grams; 
100  cubic  inches  weigh  68-69  grains.  At  —17-8°  (0°  F.),  under  the  ordinary 
pressure  of  the  atmosphere,  this  gas  condenses  to  a  colorless,  limpid  liquid, 
very  expansible  by  heat.  Cold  water  dissolves  more  than  thirty  times  its 
volume  of  sulphurous  oxide.  The  solution,  which  contains  hydrogen  sul- 
phite or  sulphurous  acid,  maybe  kept  unchanged  so  long  as  air  is  excluded, 
but  access  of  oxygen  gradually  converts  the  sulphurous  into  sulphuric  acid, 
although  dry  sulphurous  oxide  and  oxygen  gases  may  remain  in  contact 

*  The  composition  of  these  oxides  and  acids  is  thus  expressed  in  symbols : 
Sulphurous  oxide        ....        S02 

Sulphurous  acid S03II2  =  S02.OH2 

Sulphuric  oxide S03 

Sulphuric  acid S04FI2  rr  S03.OH2 

f  Sulphuric  acid 

Thiosulphuric  acid 

$  From  TroXfif,  many,  and  6uov,  sulphur. 
2  In  symbols: 

Dithionic  acid        ... 
Trithionic  acid  .        .        .        . 
Tetrathionic  acid  ....     S4Ofllla 
Pentathionic  acid      .        .         .        S606H2 
I       2(S03.On2)       +        Cu        =  S03.CuO  +        20H2        +  S02 

Sulphuric  acid.          Copper.  Copper  sulphate.  Water.  Sulphurous  oxide. 


196  SULPHUR. 

for  any  length  of  time  without  change.  When  sulphurous  oxide  and 
aqueous  vapor  are  passed  into  a  vessel  cooled  to  below  — 8-3°  or — 6°  (17°  or 
21°  F.),  a  crystalline  body  forms,  which  contains  about  24-2  sulphurous 
oxide  to  75-8  of  water. 

One  volume  of  sulphurous  oxide  gas  contains  one  volume  of  oxygen  and 
half  a  volume  of  sulphur  vapor,  condensed  into  one  volume. 

Gases  which,  like  the  present,  are  freely  soluble  in  water,  must  be  col- 
lected by  displacement,  or  by  the  use  of  the  mercurial  pneumatic  trough. 
The  manipulation  with  the  latter  is  exactly  the  same  in  principle  as  with 
the  ordinary  water-trough,  but  rather  more  troublesome,  from  the  great 
density  of  the  mercury,  and  its  opacity.  The  whole  apparatus  is  on  a  much 
smaller  scale.  The  trough  is  best  constructed  of  hard,  sound  wood,  and  so 
contrived  as  to  economize  as  much  as  possible  the  expensive  liquid  it  is  to 
contain. 

Sulphurous  acid  has  bleaching  properties ;  it  is  used  in  the  arts  for  bleach- 
ing woollen  goods  and  straw-plait.  A  piece  of  blue  litmus  paper  plunged 
into  the  moist  gas  is  first  reddened  and  then  slowly  bleached. 

The  salts  of  sulphurous  acid  are  not  of  much  importance:  those  of  the 
alkalies  are  soluble  and  crystallizable ;  they  are  easily  formed  by  direct 
combination.  The  sulphites  of  barium,  strontium,  and  calcium  are  insol- 
uble in  water,  but  soluble  in  hydrochloric  acid.  The  stronger  acids  de- 
compose them ;  nitric  acid  converts  them  into  sulphates. 

Sulphurous  oxide  unites,  under  peculiar  circumstances,  with  chlorine, 
and  also  with  iodine,  forming  compounds,  which  have  been  called  chloro- 
and  iodo-sulphuric  acids.  They  are  decomposed  by  water.  It  also  combines 
with  dry  ammoniacal  gas,  giving  rise  to  a  remarkable  compound  ;  and  with 
nitric  oxide  also,  in  presence  of  an  alkali. 

SULPHUR  TRIOXIDE  or  SULPHURIC  OXIDE  (also  called  Anhydrous  Sulphuric 
acid,  or  Sulphuric  anhydride]. — This  compound  maybe  formed  directly  by 
passing  a  dry  mixture  of  sulphurous  oxide  and  oxygen  gases  over  heated 
spongy  platinum;  or  it  may  be  obtained  by  distilling  the  most  concentrated 
sulphuric  acid  with  phosphoric  oxide,  which  then  abstracts  the  water  and 
sets  the  sulphuric  oxide  free.  It  is  usually  prepared,  however,  from  the 
fuming  oil  of  vitriol  of  Nordhausen,  which  may  be  regarded  as  a  solution 
of  sulphuric  oxide  in  sulphuric  acid.  On  gently  heating  this  liquid  in  a 
retort  connected  with  a  receiver  cooled  by  a  freezing  mixture,  the  sulphuric 
oxide  distils  over  in  great  abundance,  and  condenses  into  beautiful  white 
silky  crystals,  resembling  those  of  asbestos.  "When  thrown  into  water, 
it  hisses  like  a  red-hot  iron,  from  the  violence  with  which  combination 
occurs:  the  product  is  sulphuric  acid.  When  exposed  to  the  air,  even 
for  a  few  moments,  it  liquefies  by  absorption  of  moisture.  It  unites  with 
ammoniacal  gas,  forming  a  salt  called  ammonium  sulphamate,  the  nature  of 
which  will  be  explained  further  on. 

SULPHURIC  ACID.  —  This  acid  has  been  known  since  the  fifteenth  century. 

There  are  two  distinct  processes  by  which  it  is  at  present  prepared  — 
namely,  by  the  distillation  of  ferrous  sulphate  (copperas  or  green  vitriol), 
and  by  the  oxidation  of  sulphurous  acid  with  nitrous  and  hyponitric  acids. 

The  first  process  is  still  carried  on  in  some  parts  of  Germany,  especially 
in  the  neighborhood  of  Nordhausen  in  Prussia,  and  in  Bohemia.  The  fer- 
rous sulphate,  derived  from  the  oxidation  of  iron  pyrites,  is  deprived  by 
heat  of  the  greater  part  of  its  water  of  crystallization,  and  subjected  to  a 
high  red  heat  in  earthen  retorts,  to  which  receivers  are  fitted  as  soon  as  the 
acid  begins  to  distil  over.  A  part  gets  decomposed  by  the  very  high  tem- 
perature ;  the  remainder  is  driven  off  in  vapor,  which  is  condensed  by  the 
cold  vessel,  containing  a  very  small  quantity  of  water  or  common  sulphuric 
acid.  The  product  is  a  brown  oily  liquid,  of  about  1-9  specific  gravity,  fum- 


SULPHUR. 


197 


ing  in  the  air,  and  very  corrosive.  It  is  chiefly  made  for  the  purpose  of 
dissolving  indigo. 

The  second  method,  which  is,  perhaps,  with  the  single  exception  men- 
tioned, always  followed  as  the  more  economical,  depends  upon  the  fact  that, 
when  sulphurous  oxide,  nitrogen  tetroxide,  and  water  are  present  together 
in  certain  proportions,  the  sulphurous  oxide  becomes  oxidized  at  the  expense 
of  the  nitrogen  tetroxide,  which  by  the  loss  of  one-half  of  its  oxygen,  sinks 
to  the  condition  of  nitrogen  dioxide.  The  operation  is  thus  conducted:  A 
large  and  very  long  chamber  is  built  of  sheet-lead  supported  by  timber- 
framing:  on  the  outside,  at  one  extremity,  a  small  furnace  or  oven  is  con- 
structed, having  a  wide  tube  leading  into  the  chamber.  In  this,  sulphur  is 
kept  burning,  the  flame  of  which  heats  a  crucible  containing  a  mixture  of 
nitre  and  oil  of  vitriol.  A  shallow  stratum  of  water  occupies  the  floor  of 
the  chamber,  and  a  jet  of  steam  is  also  introduced.  Lastly,  an  exit  is  pro- 
vided at  the  remote  end  of  the  chamber  for  the  spent  and  useless  gases. 
The  effect  of  these  arrangements  is  to  cause  a  constant  supply  of  sulphur- 
ous oxide,  atmospheric  air,  nitric  acid  vapor,  and  water  in  the  state  of 
steam,  to  be  thrown  into  the  chamber,  there  to  mix  and  react  upon  each 
other.  The  nitric  acid  immediately  gives  up  a  part  of  its  oxygen  to  the 
sulphurous  oxide,  and  is  itself  reduced  to  nitrogen  tetroxide;  it  does  not 
remain  in  this  state,  however,  but  suffers  further  deoxidation  until  it  be- 
comes reduced  to  nitrogen  dioxide.  That  substance,  in  contact  with  free 
oxygen,  absorbs  a  portion  of  the  latter,  and  once  more  becomes  tetroxide, 
which  is  again  destined  to  undergo  deoxidation  by  a  fresh  quantity  of  sul- 
phurous oxide.  A  very  small  portion  of  nitrogen  tetroxide,  mixed  with  at- 
mospheric air  and  sulphurous  oxide,  may  thus  in  time  convert  an  indefinite 
amount  of  the  latter  into  sulphuric  acid,  by  acting  as  a  kind  of  carrier  be- 
tween the  oxygen  of  the  air  and  the  sulphurous  oxide.  The  presence  of 
water  is  essential  to  this  reaction. 

We  may  thus  represent  the  change:  * 


46 


•Oxygen     16 
Oxygen     16 
Sulphurous  oxide    (  Sulphur    32 
64          \  Oxygen    32 
Water  18 


Nitrogen  dioxide  30. 


Sulphuric  acid  98. 


Such  is  the  simplest  view  that  can  be  taken  of  the  production  of  sulphuric 
acid  in  the  leaden  chamber ;  but  it  is  too  much  to  affirm  that  it  is  strictly 
true ;  the  reaction  may  be  more  complex.  When  a  little  water  is  put  at 
the  bottom  of  a  large  glass  globe,  so  as  to  maintain  a  certain  degree  of  hu- 
midity in  the  air  within,  and  sulphurous  oxide  and  nitrogen  tetroxide  are 
introduced  by  separate  tubes,  symptoms  of  chemical  action  become  im- 
mediately evident,  and  after  a  little  time  a  white  crystalline  matter  is 
observed  to  condense  on  the  sides  of  the  vessel.  This  substance  appears 
to  be  a  compound  of  sulphuric  acid,  nitrous  acid,  and  a  little  water. j- 
When  thrown  into  water,  it  is  resolved  into  sulphuric  acid,  nitrogen 

*  N02  +         S02         +        OH2        =        NO  +  S04H2 

Nitrogen  Sulphurous         Water.  Nitrogen  Sulphuric 

tetroxide.  oxide.  dioxide.  acid. 

f  Gaultier  do  Claubry  assigned  to  this  curious  substance  the  composition  expressed  by  tho 
formula  2(N203.'20II2').:'>S03,  and  this  view  has  generally  been  received  by  recent  chemical 
writers.  De  la  Provostaye  has  since  shown  that  a  compound  possessing  all  the  essential  prop- 
erties of  the  body  it>  question  may  be  formed  by  bringing  together,  in  a  sealed  glass  tube, 
liquid  sulphurous  oxide  and  liquid  nitrogen  tetroxide,  both  free  from  water.  The  white  crys- 
talline solid  noon  begins  to  form,  and  at  the  expiration  of  twenty-six  hours  the  reaction  ap- 
pears complete.  The  new  product  is  accompanied  by  an  exceedingly  volatile  greenish  liquid 

17* 


198  SULPHUR. 

dioxide,  and  nitric  acid.  This  curious  body  is  certainly  very  often  pro- 
duced in  large  quantity  in  the  leaden  chambers ;  but  that  its  production  is 
indispensable  to  the  success  of  the  process,  and  constant  when  the  operation 
goes  on  well,  and  the  nitrogen  tetroxide  is  not  in  excess,  may  perhaps  ad- 
mit of  doubt. 

The  water  at  the  bottom  of  the  chamber  thus  becomes  loaded  with  sul- 
phuric acid:  when  a  certain  degree  of  strength  has  been  reached,  the  acid 
is  drawn  off  and  concentrated  by  evaporation,  first  in  leaden  pans,  and 
afterwards  in  stills  of  platinum,  until  it  attains  a  density  (when  cold)  of 
1*84,  or  thereabouts;  it  is  then  transferred  to  carboys,  or  large  glass  bot- 
tles fitted  in  baskets,  for  sale.  In  Great  Britain  this  manufacture  is  one 
of  great  national  importance,  and  is  carried  on  to  a  vast  extent.  Sulphuric 
acid  is  now  more  frequently  made  by  burning  iron  pyrites,  or  poor  copper 
ore,  or  zinc-blende,  as  a  substitute  for  Sicilian  sulphur:  it  very  frequently 
contains  arsenic,  from  which  it  may  be  freed,  however,  by  heating  it  with 
a  small  quantity  of  sodium  chloride,  or  by  passing  through  the  heated 
acid  a  current  of  hydrochloric  acid  gas,  whereby  the  arsenic  is  volatilized 
as  trichloride. 

The  most  concentrated  sulphuric  acid,  or  oil  of  vitriol,  as  it  is  often 
called,  is  a  definite  combination  of  40  parts  sulphuric  oxide,  and  9  parts 
water.*  It  is  a  colorless  oily  liquid,  having  a  specific  gravity  of  about  1-85, 
of  intensely  acid  taste  and  reaction.  Organic  matter  is  rapidly  charred 
and  destroyed  by  this  substance.  At  the  temperature  of  — 26°  ( — 15°  F.) 
it  freezes;  at  327°  (620°  F.)  it  boils,  and  may  be  distilled  without  decom- 
position. Oil  of  vitriol  has  a  most  energetic  attraction  for  water ;  it  with- 
draws aqueous  vapor  from  the  air,  and  when  it  is  diluted  with  water,  great 
heat  is  evolved,  so  that  the  mixture  always  requires  to  be  made  with  cau- 
tion. Oil  of  vitriol  is  not  the  only  hydrate  of  sulphuric  oxide;  three 
others  are  known  to  exist.  When  the  fuming  oil  of  vitriol  of  Nordhausen 
is  exposed  to  a  low  temperature,  a  white  crystalline  substance  separates, 
which  is  a  hydrate  containing  half  as  much  water  as  the  common  liquid 
acid.  Then,  again,  a  mixture  of  98  parts  of  strong  liquid  acid  and  18 
parts  of  water  f  congeals  or  crystallizes  at  a  temperature  above  0°,  and 
remains  solid  even  at  7-2°  (45°  F.).  Lastly,  when  a  very  dilute  acid  is 
concentrated  by  evaporation  in  a  vacuum  over  a  surface  of  oil  of  vitriol, 
the  evaporation  stops  when  the  sulphuric  oxide  and  water  bear  to  each 
other  the  proportion  of  80  to  54.  J 

When  the  vapor  of  sulphuric  acid  is  passed  over  red-hot  platinum,  it  is 
decomposed  into  oxygen  and  sulphurous  acid.  St.  Claire  Deville  and  De- 
bray  have  recommended  this  process  for  the  preparation  of  oxygen  on  the 
large  scale,  the  sulphurous  acid  being  easily  separated  by  its  solubility  in 
water  or  alkaline  solutions. 

Sulphuric  acid  acts  readily  on  metallic  oxides;  converting  them  into 
sulphates.  It  also  decomposes  carbonates  with  the  greatest  ease,  expelling 
carbon  dioxide  with  effervescence.  With  the  aid  of  heat  it  likewise  de- 
composes all  other  salts  containing  acids  more  volatile  than  itself.  The 
sulphates  are  a  very  important  class  of  salts,  many  of  them  being  exten- 
sively used  in  the  arts.  Most  sulphates  ate  soluble  in  water,  but  they  are 
all  insoluble  in  alcohol.  The  barium,  calcium,  strontium,  and  lead  salts 

having  the  characters  of  nitrous  acid.  The  white  substance,  on  analysis,  was  found  to  contain 
the  elements  of  two  molecules  of  sulphuric  oxide  and  one  of  nitrous  oxide,  or  N203.2S03.  M. 
de  la  Provostaye  very  ingeniously  explains  the  anomalies  in  the  different  analyses  of  the 
leaden  chamber  product,  by  showing  that  the  pure  substance  forms  crystallizable  combina- 
tions with  different  proportions  of  sulphuric  acid.  (Ann.  Chim.  Phys.  Ixxiii.  362.)  See  also 
Weber  (Jahresbericht  fur  Chemie,  1863,  p.  738;  1865,  p.  93;  Bull.  Soc.  Chim.  de  Paris,  1867, 
i.  15.) 

*  S03.OH2     =     S04Ho.  t  S03.20H2     =     S04H2.OH2. 

t  S03  30H2     =     S04H2.20H2. 


SULPHUR.  199 

are  insoluble,  or  very  slightly  soluble,  in  water;  and  are  formed  by  pre- 
cipitating a  soluble  salt  of  either  of  those  metals  with  sulphuric  acid,  or  a 
soluble  metallic  sulphate.  Barium  sulphate  is  quite  insoluble  in  water; 
consequently  sulphuric  acid,  or  its  soluble  salts,  may  be  detected  with  the 
greatest  ease  by  solution  of  barium  nitrate  or  chloride ;  a  white  precipi- 
tate is  thereby  produced  which  does  not  dissolve  in  nitric  acid. 

HYPOSULPHUROUS,  or  THIOSULPHURIC  ACID. — By  digesting  sulphur  with 
a  solution  of  potassium  or  sodium  sulphite,  a  portion  of  that  substance  is 
dissolved,  and  the  liquid,  by  slow  evaporation,  furnishes  crystals  of  hypo- 
sulphite.* The  acid  itself  is  scarcely  known,  for  it  cannot  be  isolated  : 
when  hydrochloric  acid  is  added  to  a  solution  of  a  hyposulphite,  the  acid 
of  the  latter  is  almost  instantly  resolved  into  sulphur,  which  precipitates, 
and  sulphurous  acid,  easily  recognized  by  its  odor.  In  very  dilute  solu- 
tion, however,  it  appears  to  remain  undecomposed  for  some  time.  The 
most  remarkable  feature  of  the  alkaline  hyposulphites  is  their  property 
of  dissolving  certain  insoluble  salts  of  silver,  as  the  chloride  —  a  property 
which  has  lately  conferred  upon  them  a  considerable  share  of  importance 
in  relation  to  the  art  of  photography.  They  are  also  much  used  as  anti- 
chlores  for  removing  the  last  traces  of  chlorine  from  bleached  goods. 

DITHIONIC,  or  HYPOSULPHURIC  ACID.  —  This  acid  is  prepared  by  sus- 
pending finely  divided  manganese  dioxide  in  water  artificially  cooled,  and 
then  transmitting  a  stream  of  sulp'mrous  acid  gas;  the  dioxide  becomes 
monoxide,  half  its  oxygen  converting  the  sulphurous  into  dithionic  acid.-}- 
The  manganese  dithionate  thus  prepared  is  decomposed  by  a  solution  of 
pure  barium  hydrate,  and  the  barium  salt,  in  turn,  by  enough  sulphuric 
acid  to  precipitate  the  base.  The  solution  of  dithionic  acid  may  be  con- 
centrated by  evaporation  in  a  vacuum,  until  it  acquires  a  density  of  1  -347 ; 
pushed  further,  it  decomposes  into  sulphuric  and  sulphurous  acids.  It 
has  no  odor,  is  very  sour,  and  forms  soluble  salts  with  baryta,  lime,  and 
lead  oxide. 

TRITHIONIC  ACID.  — A  substance  accidentally  formed  by  Langlois,  J  in  the 
preparation  of  potassium  hyposulphite,  by  gently  heating  with  sulphur  a 
solution  of  potassium  carbonate  saturated  with  sulphurous  acid.  It  is  also 
produced  by  the  action  of  sulphurous  oxide  on  potassium  hyposulphite. g 
Its  salts  bear  a  great  resemblance  to  those  of  hyposulphurous  acid,  but 
differ  completely  in  composition,  while  the  acid  itself  is  not  quite  so  prone 
to  change.  It  is  obtained  by  decomposing  the  potassium  salt  with  hydro- 
fluosilicic  acid:  it  may  be  concentrated  under  the  receiver  of  the  air-pump, 
but  is  gradually  decomposed  into  sulphur,  sulphurous  and  sulphuric  acids. 

TETRATHIONIC  ACID. — This  acid  was  discovered  by  Fordos  and  Gelis.  || 
When  iodine  is  added  to  a  solution  of  barium  hyposulphite,  a  large  quantity 
of  that  substance  is  dissolved,  and  a  clear  colorless  solution  obtained, 

*    S03K2  +  S  =  SaOgKa 

Potassium  Sulphur.  Potassium 

sulphite.  hyposulphite. 

t      Mn02          +  2S03H2        =        S206Mn        +        20H2 

Manganese  Sulphurous  Manganese  Water. 

dioxide.  acid.  dithionate. 

t  Ann.  Chim.  Phys.  [2],  Ixxiv.  250. 
§          2S203K2  +  3S02  -  2S306K2  +  S 

Potassium  Sulphurous  Potassium 

hyposulphite.  oxide.  trithionate. 

||  Ann.  Ch.  Pharm.  xliv.  247. 


200 


SULPHUR. 


which,  besides  barium  iodide,  contains  barium  tetrathionate.*  By  suitable 
means,  the  acid  can  be  eliminated,  and  obtained  in  a  state  of  solution.  It 
very  closely  resembles  dithionic  acid.  The  same  acid  is  produced  by  the 
action  of  sulphurous  acid  on  chlorine  disulphide. 

PENTATHIONIC  ACID.  —  Another  acid  of  sulphur  was  discovered  by  Wack- 
enroder,f  who  formed  it  by  the  action  of  hydrogen  sulphide  on  sulphurous 
acid.J  It  is  colorless  and  inodorous,  of  acid  and  bitter  taste,  and  capable 
of  being  concentrated  to  a  considerable  extent  by  cautious  evaporation. 

Under  the  influence  of  heat,  it  is  decomposed  into  sulphur,  sulphurous 
and  sulphuric  acids,  and  hydrogen  sulphide.  The  salts  of  pentathionic  acid 
are  nearly  all  soluble.  The  barium  salt  crystallizes  from  alcohol  in  square 
prisms.  The  acid  is  also  formed  when  lead  dithionate  is  decomposed  by 
hydrogen  sulphide,  and  when  chlorine  monosulphide  is  heated  with  sul- 
phurous acid. 

Sulphur  with  Hydrogen. 

HYDROGEN  MONOSULPHIDE  ;  SULPHYDRIC  ACID  ;  HYDROSULPHURIC  ACID  ; 
SULPHURETTED  HYDROGEN. — There  are  two  methods  by  which  this  important 
compound  can  be  readily  prepared,  namely,  by  the  action  of  dilute  sulphuric 
acid  upon  iron  monosulphide,  and  by  the  decomposition  of  antimony  tri- 
sulphide  with  hydrochloric  acid.  The  first  method  yields  it  most  easily, 
the  second  in  the  purest  state. 

Iron  monosulphide  is  put  into  the  apparatus  for  hydrogen,  already  several 
times  mentioned,  together  with  water,  and  oil  of  vitriol  is  added  by  the 
funnel,  until  a  copious  disengagement  of  gas  takes  place.  This  is  to  be 
collected  over  tepid  water.  The  reaction  is  thus  explained :  — 


Iron  sulphide. 

Water      .     .     . 
Sulphuric  oxide 


/  Sulphur 
\  Iron 
f Hydrogen 
\  Oxygen 


Hydrogen  sulphide. 


Ferrous  sulphate. 


By  the  other  plan,  finely  powdered  antimony  trisulphide  is  put  into  a 
flask  to  which  a  cork  and  bent  tube  can  be  adapted,  and  strong  liquid 
hydrochloric  acid  poured  upon  it.  On  the  application  of  heat,  a  double 
interchange  occurs  between  the  bodies  present,  hydrogen  sulphide  and 
antimony  trichloride  being  formed.  The  action  lasts  only  while  the  heat 
is  maintained. 


Hydrochloric  acid 
Antimony  sulphide, 


Hydrogen  sulphide. 


Antimony  chloride.  | 


Hydrogen  sulphide  is  a  colorless  gas,  having  the  odor  of  putrid  eggs ;  it 
is  most  offensive  when  in  small  quantity,  when  a  mere  trace  is  present  in 
the  air.  It  is  not  irritating,  but,  on  the  contrary,  powerfully  narcotic. 


*        2S203Ba        + 
Barium 
hyposulphite. 

Iodine. 

=            BaT2 
Barium 
iodide. 

+            S406Ba 
Barium 
tetrathionate. 

f    Ann.  Ch  Pharm 

.  Ix.  189. 

J      5S03H2       + 
Sulphurous 
acid. 

5SH2     = 
Hydrogen 
sulphide. 

S506H2      = 
Pentathionic 
acid. 

90H2        +        S6 
Water.            Sulphur. 

\      FeS            + 
Ferrous 
sulphide. 

S04H2 
Hydrogen 
sulphate. 

=            SH2 
Hydrogen 
sulphide. 

=            S04Fe 
Ferrous 
sulphate. 

II                 SbgSg                 + 

Antimonious 
sulphide. 

GHC1 

Hydrogen 
chloride. 

=            3SII2 

Hydrogen 
sulphide. 

+           2SbCl3 
Antimonious 
chloride. 

SULPHUR.  201 

When  set  on  fire,  it  burns  with  a  blue  flame,  producing  sulphurous  acid 
when  the  supply  of  air  is  abundant;  and  depositing  sulphur  when  the 
oxygen  is  deficient.  Mixed  with  chlorine,  it  is  instantly  decomposed,  with 
separation  of  the  whole  of  the  sulphur. 

This  gas  has  a  specific  gravity  of  1-171  referred  to  air,  or  17  referred  to 
hydrogen  as  unity  ;  a  litre  weighs  1-51991  grams. 

A  pressure  of  17  atmospheres  at  10°  (50°  F.)  reduces  it  to  the  liquid  form. 
Cold  water  dissolves  its  own  volume  of  hydrogen  sulphide,  and  the  solution 
is  often  directed  to  be  kept  as  a  test ;  it  is  so  f.  13g 

prone  to  decomposition,  however,  by  the  oxygen 
of  the  air,  that  it  quickly  spoils.  A  much  better 
plan  is  to  keep  a  little  apparatus  for  generating 
the  gas  always  at  hand,  and  ready  for  use  at  a 
moment's  notice.  A  small  bottle  or  flask,  to 
which  a  bit  of  bent  tube  is  fitted  by  a  cork,  is 
supplied  with  a  little  iron  sulphide  and  water ; 
when  required  for  use,  a  few  drops  of  oil  of 
vitriol  are  added,  and  the  gas  is  at  once  evolved. 
The  experiment  completed,  the  liquid  is  poured 
from  the  bottle,  replaced  by  a  little  clean  water, 
and  the  apparatus  is  again  ready  for  use. 

Potassium  heated  in  hydrogen  sulphide  burns 
with  great  energy,  becoming  converted  into  sulphide,  while  pure  hydrogen 
remains,  equal  in  volume  to  the  original  gas.  Taking  this  act  into  account, 
and  comparing  the  density  of  the  gas  with  those  of  hydrogen  and  sulphur 
vapor,  it  appears  that  every  volume  of  hydrogen  sulphide  contains  one 
volume  of  hydrogen  and  half  of  a  volume  of  sulphur-vapor,  the  whole 
condensed  into  one  volume,  a  constitution  precisely  analogous  to  that  of 
water-vapor.  This  corresponds  very  nearly  with  its  composition  by  weight, 
determined  by  other  means  —  namely,  16  parts  sulphur  and  1  part  hydrogen. 

When  a  mixture  of  100  measures  of  hydrogen  sulphide  and  150  measures 
of  pure  oxygen  is  exploded  by  the  electric  spark,  complete  combustion 
ensues,  and  100  measures  of  sulphurous  oxide  gas  result. 

Hydrogen  sulphide  is  a  frequent  product  of  the  putrefaction  of  organic 
matter,  both  animal  and  vegetable ;  it  occurs  also  in  certain  mineral 
springs,  as  at  Harrogate,  and  elsewhere.  When  accidentally  present  in 
the  atmosphere  of  an  apartment,  it  may  be  instantaneously  destroyed  by  a 
small  quantity  of  chlorine  gas. 

There  are  few  reagents  of  greater  value  to  the  practical  chemist  than 
this  substance:  when  brought  in  contact  with  many  metallic  solutions,  it 
gives  rise  to  precipitates,  which  are  often  exceedingly  characteristic  in 
appearance,  arid  it  frequently  affords  the  means  of  separating  metals  from 
each  other  with  the  greatest  precision  and  certainty.  The  precipitates 
spoken  of  are  insoluble  sulphides,  formed  by  the  mutual  decomposition  of 
the  metallic  oxides  or  chlorides  and  hydrogen  sulphide,  water  or  hydro- 
chloric acid  being  produced  at  the  same  time.  All  the  metals  are  in  fact 
precipitated,  whose  sulphides  are  insoluble  in  water  and  in  dilute  acids. 

Arsenic  and  cadmium  solutions  thus  treated  give  bright  yellow  precipi- 
tates, the  former  soluble,  the  latter  insoluble,  in  ammonium  sulphide;  tin 
salts  give  a  brown  or  a  yellow  precipitate,  according  as  the  metal  is  in  the 
form  of  a  stannous  or  a  stannic  salt;  both  soluble  in  ammonium  sulphide. 
Antimony  solutions  give  an  orange-red  precipitate,  soluble  in  ammonium 
sulphide.  Copper,  lead,  bismuth,  mercury,  and  silver  salts  give  dark- 
brown  or  black  precipitates,  insoluble  in  ammonium  sulphide ;  gold  and 
platinum  salts,  black  precipitates,  soluble  in  ammonium  sulphide. 

Hydrogen  sulphide  possesses  the  properties  of  an  acid ;  its  solution  in 
water  reddens  litmus-paper. 


202  SULPHUR. 

The  best  test  for  the  presence  of  this  compound  is  paper  wetted  with 
solution  of  lead  acetate.  This  salt  is  blackened  by  the  smallest  trace  of 
the  gas. 

Hydrogen  duulphide.  —  lhis  substance  corresponds  m  constitution  and 
instability  to  the  hydrogen  dioxide;  it  is  prepared  by  the  following  means: 

Equal  weights  of  slaked  lime  and  flowers  of  sulphur  are  boiled  with  5  or 
G  parts  of  water  for  half  an  hour,  when  a  deep  orange-colored  solution  is 
produced,  containing,  among  other  things,  calcium  disulphide.  This  is 
filtered,  and  slowly  added  to  an  excess  of  dilute  sulphuric  acid,  with  con- 
stant agitation.  A  white  precipitate  of  separated  sulphur  and  calcium 
sulphate  makes  its  appearance,  together  with  a  quantity  of  yellow  oily- 
looking  matter,  which  collects  at  the  bottom  of  the  vessel:  this  io  hydro- 
gen disulphide.* 

If  the  experiment  be  conducted  by  pouring  the  acid  into  the  solution  of 
the  sulphide,  then  nothing  but  finely  divided  precipitated  sulphur  is  ob- 
tained. 

The  disulphide  is  a  yellow,  viscid,  insoluble  liquid,  exhaling  the  odor 
of  sulphuretted  hydrogen;  its  specific  gravity  is  1-769.  It  is  slowly  de- 
composed even  in  the  cold  into  sulphur  and  hydrogen  monosulphide,  and 
instantly  by  a  higher  temperature,  or  by  contact  with  many  metallic 
oxides. 

Carbon  and  Sulphur. 

CAKBON  DISULPHIDE  OR  BISULPHIDE,  f  —  A  white  porcelain  tube  is  filled 
with  pieces  of  charcoal  which  have  been  recently  heated  to  redness  in  a 
covered  crucible,  and  fixed  across  a  furnace  in  a  slightly  inclined  position. 
Into  the  lower  extremity  a  tolerably  wide  tube  is  secured  by  the  aid  of  a 
cork:  this  tube  bends  downward,  and  passes  nearly  to  the  bottom  of  a 
bottle  filled  with  fragments  of  ice  and  a  little  water.  The  porcelain  tube 
being  heated  to  a  bright  redness,  fragments  of  sulphur  are  thrown  into 
the  open  end,  which  is  immediately  afterwards  stopped  by  a  cork.  The 
sulphur  melts,  and  becomes  converted  into  vapor,  which  at  that  high  tem- 
perature combines  with  the  carbon,  forming  an  exceedingly  volatile  com- 
pound, which  is  condensed  by  the  ice  and  collects  at  the  bottom  of  the 
vessel.  This  is  collected  and  redistilled  at  a  ^ery  gentle  heat  in  a  retort 
connected  with  a  good  condenser. 

For  preparation  on  the  large  scale,  a  tubulated  earthen  retort  is  filled 
with  charcoal,  and  the  sulphur  is  dropped  in  through  a  porcelain  tube 
passing  through  the  tubulus  and  reaching  nearly  to  the  bottom ;  or  the 
charcoal  is  contained  in  a  large  iron  cylinder,  and  the  sulphur  introduced 
through  a  pipe  fitted  into  the  lower  part. 

*  The  reaction  which  ensues  when  calcium  hydrate,  sulphur,  and  water  are  boiled  together 
is  rather  complex,  disulplride  or  pentasulphide  of  calcium  being  formed,  together  with  calcium 
hyposulphite,  arising  from  the  transfer  of  the  oxygen  of  the  decomposed  lime  to  another  por- 
tion of  sulphur. 

3CaO        +        S6        =        2CaSa        -f        S203Ca 
Lime.  Sulphur.  Calcium  Calcium 

disulphide.          hyposulphite. 

The  calcium  disulphide,  decomposed  by  an  acid  under  favorable  circumstances,  yields  a  cal- 
cium salt  and  hydrogen  disulphide. 

CaS2        +        S04ITa         =         SH2         +         S04Ca 

Calcium  Sulphuric          Hydrogen  Calcium 

disulphide.  acid.  disulphide.  sulphate. 

When  the  acid  is  poured  into  the  sulphide,  sulphuretted  hydrogen,  water,  and  calcium  sul- 
pliatr  arc.  produced,  while  the  excess  of  sulphur  is  thrown  down  as  a  fine  white  powder,  the 
"precipitated  sulphur"  of  the  Pharmacopoeia.  When  the  object  is  to  prepare  the  latter  sub- 
stance, hydrochloric  acid  must  be  used  in  place  of  sulphuric  acid. 

tcs* 


SULPHUR.  203 

Carbon  disulphide  is  a  transparent,  colorless  liquid  of  great  refractive 
and  dispersive  power.  Its  density  is  1-27'J,  that  of  its  vapor  is  2-67.  It 
boils  at  43°  (110°  F.),  and  emits  vapor  of  considerable  elasticity  at  com- 
mon temperatures.  This  substance  has  a  very  repulsive  odor.  When  set 
on  fire  in  the  air,  it  burns  with  a  blue  flame,  forming  carbon  dioxide  and 
sulphur  dioxide  gases;  and  when  its  vapor  is  mixed  with  oxygen,  it  be- 
comes explosive.  Carbon  disulphide,  when  heated  with  water  in  a  sealed 
tube  to  about  153°  (307°  F.),  is  converted  into  carbon  dioxide  and  hydrogen 
sulphide.  In  contact  with  nascent  hydrogen  (when  heated  with  zinc  and 
dilute  sulphuric  acid),  it  is  converted  into  a  white  crystalline  substance 
containing  carbon,  hydrogen,  and  sulphur,*  crystallizing  in  square  prisms, 
insoluble  in  water,  alcohol,  and  ether,  but  soluble  in  carbon  disulphide, 
subliming  at  150°  (302°  F.),  and  decomposing  at  200°.  Carbon  disulphide 
freely  dissolves  sulphur,  and  by  spontaneous  evaporation  deposits  the  latter 
in  beautiful  crystals;  it  also  dissolves  phosphorus,  iodine,  camphor,  and 
caoutchouc,  and  mixes  easily  with  oils.  It  is  extensively  used  in  the  vul- 
canization of  caoutchouc,  and  in  the  manufacture  of  gutta-percha,  also 
for  extracting  bitumen  from  mineral  substances,  and  oil  from  seeds. 

Carbon  disulphide  unites  with  metallic  sulphides,  forming  salts  called 
sulphocarbonates,  which  have  the  composition  of  carbonates  with  the  oxygen 
replaced  by  sulphur.  By  treating  the  ammonium  salt  with  dilute  sulphuric 
or  hydrochloric  acid,  an  oily  acid  liquid  is  precipitated,  consisting  of 
hydrogen  sulphocarbonate,  or  sulphocarbonic  acid.f 

Compounds  of  Sulphur  with  Chlorine. 

When  dry  chlorine  is  passed  over  the  surface  of  sulphur  kept  melted  in 
a  small  glass  retort  connected  with  a  good  condensing  arrangement,  a  deep 
orange-yellow  mobile  liquid  distils  over,  having  a  peculiar  and  disagree- 
able odor,  and  boiling  at  136°  (276°  F.).  As  this  substance  dissolves  both 
sulphur  and  chlorine,  it  is  not  easy  to  obtain  it  in  a  pure  and  definite 
state.  It  contains  32  parts  sulphur  and  35-5  chlorine,  and  is  called  sulphur 
monochloride  (or  subchloride),  also  chlorine  bisulphide.  J 

It  is  instantly  decomposed  by  water,  hydrochloric  and  hyposulphurous 
acids  being  formed,  and  sulphur  separated.  The  hyposulphurous  acid  in 
its  turn  decomposes  into  sulphur  and  sulphurous  acid.|  By  exposing  the 
above  compound  for  a  considerable  time  to  the  action  of  chlorine,  and  then 
distilling  it  in  a  stream  of  the  gas,  a  deep-red  liquid  is  obtained,  at  a  cer- 
tain stage  of  the  distillation,  heavier  than  water,  boiling  at  164°,  and  con- 
taining twice  as  much  chlorine  as  the  monochloride,  hence  called  sulphur 
dichloride  or  chlorine  mono  sulphide.\\  It  appears,  however,  to  be  not  a  definite 
compound  of  sulphur  and  chlorine,  but  a  mixture  of  the  preceding  with 
the  following  compound. 

A  compound  called  sulphur  tetrachloride,^  containing  32  parts  of  sulphur 
to  142  parts  of  chlorine,  appears  to  exist  in  combination  with  certain  me- 
tallic chlorides,  but  is  not  known  in  the  separate  state.  According  to 
Carius,**  the  red-brown  liquid,  obtained  as  above  mentioned  by  saturating 
chlorine  disulphide  with  chlorine,  is  a  mixture  of  the  monochloride  and 

*  CSH2. 

f  Calcium  carbonate     .    .    .  C03Ca  =        C02.CaO 

Calcium  sulpho-carbonate  .  CS3ra  =        CS2.CaS 

Hydrogen  sulpho-carbonate  CSaII2  CSjj.H2S 


2  3IT20     =      4IIC1       +        So        +        Ss08Ha        (or  S03H2     +        S) 

Sulphur    Water.    Hydrochloric      Sulphur.  Hyposul-    Sulphurous        Sulphur. 

monochloride.  acid.  phurous  acid.      acid. 

I*  Ann^Ch.  Pharm.  cvi.  291  ;  ex.  209;  see  also  Watts's  Pictionary  of  Chemistry,  v.  633. 


204  SELENIUM. 

tetrachloride  in  various  proportions,  according  to  the  temperature  at  which 
the  saturation  is  effected. 

CARBON  OXYCHLORIDE.* —  This  compound,  also  called  phosgene  gas,  has 
been  already  mentioned.  It  is  produced  by  the  direct  combination  of 
chlorine  and  carbon  monoxide  under  the  influence  of  sunshine;  but  is 
more  easily  prepared  by  passing  carbon  monoxide  into  boiling  antimony 
pentachlorides.  It  must  be  received  over  mercury,  as  water  decomposes  it. 

CARBON  SULPHOCHLORIDE.| —  This  compound,  the  sulphur-analogue  of 
the  preceding,  is  produced,  together  with  chlorine  monosulphide,  by  the 
action  of  dry  chlorine  on  carbon  disulphide,J  or  by  passing  a  mixture  of 
hydrogen  sulphide  and  vapor  of  carbon  tetrachloride  through  a  red-hot 
tube.$  It  is  a  yellow  liquid  having  a  very  irritating  odor,  not  acted  upon 
by  water  or  acids,  but  decomposed  by  potash,  yielding  potassium  sulphide, 
potassium  carbonate,  and  carbon  tetrachloride.  || 

SULPHUR  AND  BROMINE. — Bromine  dissolves  sulphur,  forming  a  brown- 
red  liquid  probably  containing  a  sulphur  bromide  analogous  to  sulphur 
monochloride ;  but  it  has  not  been  obtained  pure. 

SULPHUR  AND  IODINE.  —  These  elements  combine  when  heated  together, 
even  under  water.  The  resulting  compound,  containing  32  parts  of  sulphur 
and  127  parts  of  iodine, ^[  is  a  blackish-gray  radio-crystalline  mass,  resem- 
bling native  antimony  sulphide.  It  decomposes  at  higher  temperatures, 
gives  off  iodine  on  exposure  to  the  air,  and  is  insoluble  in  water.  By 
heating  254  parts  of  iodine  with  32  parts  of  sulphur,**  a  compound  is 
obtained  which  smells  like  iodine,  and  is  said  to  be  a  powerful  remedy  in 
skin-diseases.  A  cinnabar-red  sulphur  iodide  is  obtained,  according  to 
Grosourdi,  by  precipitating  iodine  trichloride  with  hydrogen  sulphide. 


SELENIUM. 

This  is  a  very  rare  substance,  much  resembling  sulphur  in  its  chemical 
relations,  and  found  in  association  with  that  element  in  some  few  localities, 
or  replacing  it  in  certain  metallic  combinations,  as  in  the  lead  selenide  of 
Clausthal  in  the  Hartz. 

Selenium  is  a  reddish-brown  solid  body,  somewhat  translucent,  and  hav- 
ing an  imperfect  metallic  lustre.  Its  specific  gravity,  when  rapidly  cooled 
after  fusion,  is  4-3.  At  100°,  or  a  little  above,  it  melts,  and  boils.  It  is 
insoluble  in  water,  and  exhales,  when  heated  in  the  air,  a  peculiar  and 
disagreeable  odor,  which  has  been  compared  to  that  of  decaying  horse- 
radish: it  is  insoluble  in  alcohol,  but  dissolves  slightly  in  carbon  bisulphide, 
from  which  solution  it  crystallizes. 

Two  oxides  of  selenium  are  known.  The  one  containing  the  smallest 
proportion  of  oxygen  is  formed  by  the  imperfect  combustion  of  selenium 
in  air  or  oxygen  gas.  It  is  a  colorless  gas  which  is  the  source  of  the  pe- 
culiar horse-radish  odor  above  mentioned.  Its  composition  is  not  known. 

The  higher  oxide,  called  selenious  oxide,  is  produced  by  burning  selenium 

*  COC12.  t  CSC12. 

t  CS2  +  C14           =  CSC12           +      '  SCI* 

1  CC14  +  SH2           -  2HC1             +  CSC12. 

I  2CSC12  +  3K20  =      2K2S      -f      C03K2      +  CC14. 


TELLURIUM.  205 

in  a  stream  of  oxygen  gas;  it  contains  79-5  parts,  by  weight,  of  selenium, 
and  32  of  oxygen.  It  is  a  white  solid  substance  which  absorbs  water 
rapidly,  forming  a  hydrate,  viz. : 

Selenium.    Oxygen.    Hydrogen.    Selenious     Water. 

oxide. 

Selenious    acid,    or )  «n  A 

Hydrogen  selenite  }         '         '     79'4    +    48+2       or  111-4  +  18 

This  acid,  analogous  in  composition  and  properties  to  sulphurous  acid,  is 
likewise  produced  by  dissolving  selenium  in  nitric  or  nitro-muriatic  acid. 
It  is  deposited  from  its  hot  aqueous  solution  by  slow  cooling  in  prismatic 
crystals  like  those  of  saltpetre;  but  when  the  solution  is  evaporated  to 
dryness,  the  selenious  acid  is  resolved  into  water  and  selenious  oxide,  which 
sublimes  at  a  higher  temperature. 

Selenious  acid  is  a  very  powerful  acid,  approximating  to  sulphuric  acid 
in  the  energy  of  its  reactions.  It  reddens  litmus,  decomposes  carbonates 
with  effervescence,  and  decomposes  nitrates  and  chlorides  with  aid  of  heat. 
Its  solution  precipitates  lead  and  silver  salts,  and  is  decomposed  by  hydro- 
gen sulphide,  yielding  a  precipitate  of  selenium  sulphide.* 

The  metallic  selenites  resemble  the  sulphites.  When  heated  with  sodium 
carbonate  in  the  inner  blowpipe  flames,  they  emit  the  characteristic  odor 
of  selenium.  They  are  not  decomposed  by  boiling  with  hydrochloric  acid. 

Selenic  Acid  is  a  more  highly  oxidized  acid  of  selenium,  analogous  to 
sulphuric  acid,  and  containing  79-4  parts,  by  weight,  of  selenium,  64  of 
oxygen,  and  2  of  hydrogen. f  The  corresponding  anhydrous  oxide  is  not 
known.  Selenic  acid  is  prepared  by  fusing  potassium  or  sodium  nitrate 
with  selenium,  precipitating  the  selenate  so  produced  with  a  lead  salt,  and 
then  decomposing  the  compound  with  hydrogen  sulphide.  The  acid  strongly 
resembles  oil  of  vitriol;  but,  when  very  much  concentrated,  decomposes, 
by  the  application  of  heat,  into  selenious  acid  and  oxygen.  The  selenates 
bear  the  closest  analogy  to  the  sulphates  in  almost  every  particular.  They 
are  decomposed  by  boiling  with  hydrochloric  acid,  chlorine  being  evolved 
and  a  salt  of  selenious  acid  being  produced. 

HYDROGEN  SELENIDE  ;  SELENHYDRIC  ACID  ;  SELENETTED  HYDROGEN.  — 
This  substance  is  produced  by  the  action  of  dilute  sulphuric  acid  upon  po- 
tassium or  iron  selenide.  It  very  much  resembles  sulphuretted  hydrogen, 
being  a  colorless  gas,  freely  soluble  in  water,  and  decomposing  metallic 
solutions  like  that  substance  :  insoluble  selenides  are  thus  produced.  This 
gas  is  said  to  act  very  powerfully  upon  the  lining  membrane  of  the  nose, 
exciting  catarrhal  symptoms,  and  destroying  the  sense  of  smell.  It  contains 
79-4  parts  selenium  and  2  parts  hydrogen.  J 


TELLURIUM. 

This  element  possesses  many  of  the  characters  of  a  metal,  but  it  bears 
so  close  a  resemblance  to  selenium,  both  in  its  physical  properties  and  its 
chemical  relations,  that  it  is  most  appropriately  placed  in  the  same  group 
with  that  body.  Tellurium  is  found  in  a  few  scarce  minerals  in  association 

*    Se03H2      +        2SH2        =        30II2        +        8683. 
Selenious  Hydrogen  Water. 

acid.  sulphide, 

f  Selenic  acid,  Se04H2- 


206  TELLURIUM. 

with  gold,  silver,  lead,  and  bismuth,  apparently  replacing  sulphur,  and  is 
most  easily  extracted  from  the  bismuth  sulpho-telluride  of  Chemnitz  in 
Hungary.  The  finely  powdered  ore  is  mixed  with  an  equal  weight  of  dry 
sodium  carbonate,  the  mixture  made  into  a  paste  with  oil,  and  heated  to 
whiteness  in  a  closely  covered  crucible.  Sodium  telluride  and  sulphide  are 
thereby  produced,  and  metallic  bismuth  is  set  free.  The  fused  mass  is  dis- 
solved in  water,  and  the  solution  freely  exposed  to  the  air,  when  the  sodium 
and  sulphur  oxidize  to  sodium  hydrate  and  hyposulphite,  while  the  tellu- 
rium separates  in  the  metallic  state. 

Tellurium  has  the  color  and  lustre  of  silver  ;  by  fusion  and  slow  cooling 
it  may  be  made  to  exhibit  the  form  of  rhombohedral  crystals  similar  to 
those  of  antimony  and  arsenic.  It  is  brittle,  and  a  comparatively  bad  con- 
ductor of  heat  and  electricity:  it  has  a  density  of  6-26,  melts  at  a  little 
below  a  red-heat,  and  volatilizes  at  a  higher  temperature.  Tellurium  burns 
when  heated  in  the  air,  and  is  oxidized  by  nitric  acid. 

Tellurium  forms  two  oxides,  analogous  in  composition  to  the  oxides  of 
sulphur,  and  likewise  forming  acids  by  combination  with  water. 

Composition  by  weight.* 

Tellurium.    Oxygen.    Hydrogen. 
Tellurous  oxide      .         .         .128  82 


acid  .         .          128     +     48     + 


Telluric      oxide      .         .         .128     +     48 
-  acid    .         .         .         128+64     +     2 

TELLUROUS  OXIDE  may  be  prepared  by  heating  the  precipitated  acid  to 
low  redness.  It  also  separates  in  semi-crystalline  grains  from  the  aqueous 
solution  of  the  acid  when  gently  heated  ;  more  abundantly  and  in  well 
defined  octohedrons  from  the  solution  of  tellurous  acid  in  nitric  acid.  It 
is  fusible  and  volatile,  slightly  soluble  in  water,  but  does  not  redden  litmus. 
When  fused  with  alkaline  hydrates  or  carbonates,  it  forms  tellurites. 

TELLUROUS  ACID  is  best  obtained  by  decomposing  tellurium  tetrachloride 
with  water.  It  may  also  be  prepared  by  dissolving  tellurium  in  nitric  acid 
of  spec.  gr.  1-25,  and  pouring  the  solution,  after  a  few  minutes,  into  a 
mass  of  water.  By  either  process  it  is  obtained  as  a  somewhat  bulky  pre- 
cipitate, which,  when  dried  over  oil  of  vitriol,  appears  as  a  light,  white, 
earthy  mass,  having  a  bitter  metallic  taste.  It  is  slightly  soluble  in  water, 
more  easily  soluble  in  alkalies  and  acids,  the  nitric  acid  solution  alone  being 
unstable.  Sulphurous  acid,  zinc,  phosphorus,  and  other  reducing  agents, 
precipitate  metallic  tellurium  from  the  acidified  solution  of  tellurous  acid. 
Like  selenious  acid,  it  is  decomposed  by  hydrogen  sulphide  and  alkaline 
sulph-hydrates,  with  formation  of  a  dark-brown  tellurium  sulphide,  which 
dissolves  readily  in  excess  of  alkaline  sulph-hydrate,  forming  a  sulpho- 
tellurite. 

Tellurous  acid  is  a  hydrate  in  which  the  acid  and  basic  tendencies  are 
nearly  balanced  ;  in  other  words,  the  tellurium  of  the  compound  can  replace 
the  hydrogen  of  an  acid  to  form  tellurous  salts,  and  the  hydrogen  of  the 
compound  can  be  replaced  by  the  basylous  metals,  to  form  metallic  tellu- 
rites.f  The  tellurites  of  potassium,  sodium,  barium,  strontium,  and  cal- 

*  Tellurous  oxide  Te09 

acid    Te03H2    =    Te02.OH2. 


f     TELLURIUM  SALTS. 
Te(S04)2    Sulphate. 
Te(N03)4  Nitrate. 
Te(C204)2  Oxalate. 
Chloride. 


Telluric     oxide  Te03 

acid    Te04H2    =    Te03.OH2. 


ssr 


TELLURITES. 

Te03H2          Hydrogen  tellurite. 
Te03K2          Potassium  tellurite. 
To03KH       Hydrogen  and  potassium  tellurita 
(Te03)2KH8  Trihydropotassic  tellurite. 


TELLURIUM.  207 

cium,  are  formed  by  fusing  tellurous  oxide,  or  acid,  with  the  carbonates 
of  the  several  metals  in  the  required  proportions.  These  tellurites  are 
all  more  or  less  soluble  in  water.  The  tellurites  of  the  other  metals,  which 
are  insoluble,  are  obtained  by  precipitation. 

TELLURIC  OXIDE  AND  ACID. — Equal  parts  of  tellurous  oxide  and  sodium 
carbonate  are  fused,  and  the  product  is  dissolved  in  water;  a  little  sodium 
hydrate  is  added,  and  a  stream  of  chlorine  passed  through  the  solution. 
The  liquid  is  next  saturated  with  ammonia,  and  mixed  with  solution  of 
barium  chloride,  by  which  a  white  insoluble  precipitate  of  barium  tellurate 
is  thrown  down.  This  is  washed  and  digested  with  a  quarter  of  its  weight 
of  sulphuric  acid,  and  diluted  with  water.  The  filtered  solution  gives,  on 
evaporation  in  the  air,  large  crystals  of  telluric  acid,  containing  water  of 
crystallization.* 

Crystallized  telluric  acid  is  freely,  although  slowly,  soluble  in  water ;  it 
has  a  metallic  taste,  and  reddens  litmus-paper.  The  crystals  give  off  their 
water  of  crystallization  at  100°,  and  the  remaining  acid,  when  strongly 
heated,  gives  off  more  water  and  yields  the  anhydrous  oxide,  which  is  then 
insoluble  in  water,  and  even  in  a  boiling  alkaline  liquid.  At  the  temperature 
of  ignition,  telluric  oxide  loses  oxygen,  and  passes  into  tellurous  oxide. 

The  tellurates  of  the  alkali-metals  f  are  soluble  in  water,  and  are  prepared 
by  dissolving  the  required  quantities  of  telluric  acid  and  an  alkaline  car- 
bonate in  hot  water.  The  other  tellurates  are  insoluble,  and  are  obtained 
by  precipitation. 

TELLURIUM  SULPHIDES.  J  —  Tellurium  forms  two  sulphides,  analogous  in 
composition  to  the  oxides ;  they  are  formed  by  the  action  of  hydrogen  sul- 
phide on  solutions  of  tellurous  acid  and  telluric  acid  respectively.  They 
are  brown  or  black  substances,  which  unite  with  metallic  sulphides,  forming 
salts  called  sulphotellurites  and  sulphotellurates. 

HYDROGEN  TELLURIDE.  —  Tellurhydric  acid,  Hydrotelluric  add,  or  Telluretled 
Hydrogen.  \  —  This  compound  is  a  gas,  resembling  sulphuretted  and  seleni- 
etted  hydrogen.  It  is  prepared  by  the  action  of  hydrochloric  acid  on  zinc 
telluride.  It  dissolves  in  water,  forming  a  colorless  liquid,  which  precipi- 
tates most  metals  from  their  solutions,  and  deposits  tellurium  on  exposure 
to  the  air. 

TELLURIUM  CHLORIDES.  ||  —  Tellurium  forms  a  dichloride  and  a  tetra- 
chloride,  both  volatile  and  decomposable  by  excess  of  water,  the  latter  being 
completely  resolved  into  tellurous  and  hydrochloric  acids. \  The  tetra- 
chloride  unites  with  the  chlorides  of  the  alkali-metals,  to  form  crystallizable 
double  salts. 

The  bromides  and  iodides  of  tellurium  correspond  to  the  chlorides  in  prop- 
erties and  composition. 

*  Crystallized  telluric  acid,  Te04H*20Hs;  acid  dried  at  100°,  Te04Hfc. 

t  Neutral  potassium  tellurate        ....        TV04K3 

T  Acid  Te04KII 

Quadracid      .  Te04KH.Te04Ha 

Anhydrous  quadri  tellurate Te04K2.3Te04. 

t  TeS«  and  TeS2.  §  TeH».  ||  TeCl2  and  TeCl4. 

fiTeC'li       +        3H20     =    411C1          +        Te08H2. 


208  BOKIC    OXIDE. 


BORON. 

This  element,  the  basis  of  boric  or  boracic  acid,  is  prepared  by  heating 
the  double  fluoride  of  boron  and  potassium  with  metallic  potassium  in 
a  small  iron  vessel,  and  washing  out  the  soluble  salts  with  water.  It  is  a  dull, 
greenish-brown  powder,  which  burns  in  the  air  when  heated,  producing 
boric  oxide.  Nitric  acid,  alkalies  in  the  fused  state,  chlorine,  and  other 
agents,  attack  it  readily. 

By  a  process  analogous  to  that  adopted  for  the  preparation  of  the  diamond 
variety  of  silicium,  Wohler  and  Deville  have  procured  also  the  correspond- 
ing modification  of  boron.  It  crystallizes  in  square  octohedrons,  generally 
of  a  brownish  color,  possessing  very  nearly  the  hardness  and  refractive 
power  of  diamond.  It  is  infusible  in  the  flame  of  the  oxy-hydrogen  blow- 
pipe, but  burns  in  oxygen  at  the  same  temperature  at  which  the  diamond 
is  oxidized.  Its  specific  gravity  is  2-68. 

By  fusing  boric  oxide  with  aluminium,  Wohler  and  Deville  likewise  ob- 
tained, together  with  diamond  boron,  a  small  quantity  of  graphite-like 
substance  which  they  at  first  regarded  as  a  graphitoidal  modification  of 
boron ;  but  by  more  recent  experiments,  they  have  found  that  it  is  a  com- 
pound of  boron  with  aluminium.  This  compound  is  obtained  in  larger 
quantity  by  passing  the  vapor  of  boric  chloride  over  fused  aluminium.  It 
crystallizes  in  thin  opaque  six-sided  plates,  having  a  pale  copper-color,  and 
perfect  metallic  lustre. 

BORIC  OXIDE  AND  ACID.*  —  There  is  but  one  oxide  of  boron,  namely, 
boric  oxide,  containing  11  parts  of  boron  and  48  of  oxygen.  It  unites 
with  water  and  metallic  oxides,  forming  boric  acid  and  metallic  borates. 

Boric  or  Boracic  Acid,  or  Hydrogen  Borate,  contains  11  parts  boron,  48 
oxygen,  and  3  hydrogen,  or  7  parts  boric  oxide,  and  54  water.  It  is  found 
in  solution  in  the  water  of  the  hot  volcanic  lagoons  of  Tuscany,  whence  a 
large  supply  is  at  present  derived.  It  is  also  easily  made  by  decomposing 
with  sulphuric  acid  a  hot  solution  of  borax,  a  salt  brought  from  the  East 
Indies,  consisting  of  sodium  borate. 

Boric  acid  crystallizes  in  transparent  colorless  plates,  soluble  in  about  25 
parts  of  cold  water,  and  in  a  much  smaller  quantity  at  the  boiling  heat; 
the  acid  has  but  little  taste,  and  feebly  affects  vegetable  colors.  When 
heated,  it  loses  water,  and  melts  to  a  glassy  transparent  mass  of  anhydrous 
boric  oxide,  which  dissolves  many  metallic  oxides  with  great  ease.  The 
crystals  dissolve  in  alcohol,  and  the  solution  burns  with  a  green  flame. 

Glassy  boric  oxide,  in  a  state  of  fusion  requires  for  its  dissipation  in 
vapor  a  very  intense  and  long-continued  heat ;  the  aqueous  solution  cannot, 
however,  be  evaporated  without  very  appreciable  loss  by  volatilization: 
hence  it  is  probable  that  the  acid  is  far  more  volatile  than  the  anhydrous 
oxide. 

By  heating  in  a  glass  flask  or  retort,  1  part  of  vitrified  boric  oxide,  2  of 
fluor-spar,  and  12  of  oil  of  vitriol,  a  gaseous  boron  fluoride^  may  be  obtained, 
and  received  in  glass  jars  standing  over  mercury.  It  is  a  transparent  gas, 
easily  soluble  in  water,  and  very  heavy ;  it  forms  a  dense  fume  in  the  air,  like 
the  fluoride  of  silicium. 

BORON  NITRIDE.  J  — This  compound,  containing  11  parts  of  boron  and  14 
t  nitrogen,  is  produced  by  heating  boric  oxide  with  metallic  cyanides,  or 

*  Boric  oxide,  B203.    Boric  acid,  B203,  3H20,  or  B03H3. 
B*3-  J  BN. 


SILICIUM.  209 

by  heating  to  bright,  redness  a  mixture  of  sal-ammoniac  and  pure  anhy- 
drous borax.*  It  is  a  white  amorphous  powder,  insoluble  in  water,  infus- 
ible and  non-volatile.  When  heated  in  a  current  of  steam,  it  yields  ammonia 
and  boric  oxide,f  and  likewise  gives  off  a  large  quantity  of  ammonia  when 
fused  with  potash. 

Boron  Chloride^  was  formerly  believed  to  be  a  permanent  gas :  recent  re- 
searches have  proved  that  it  is  a  liquid,  boiling  at  17°,  decomposed  by 
water,  with  production  of  boric  and  hydrochloric  acids,  and  fuming  strongly 
in  the  air.  It  may  be  most  easily  obtained  by  exposing  to  the  action  of 
dry  chlorine  at  a  very  high  temperature  an  intimate  mixture  of  glassy 
boric  oxide  and  charcoal.  It  resembles  in  constitution  the  lower  chloride 
of  phosphorus. 

There  is  also  a  Boron  bromide  $  of  similar  constitution. 


SILICIUM. 

Silicium,  sometimes  called  silicon,  in  union  with  oxygen  constituting 
silica,  or  the  earth  of  flints,  is  a  very  abundant  substance,  and  one  of  great 
importance.  It  enters  largely  into  the  composition  of  many  of  the  rocks 
and  mineral  masses  of  which  the  surface  of  the  earth  is  composed.  The 
following  process  yields  silicium  most  readily.  The  double  fluoride  of  si- 
licium  and  potassium  is  heated  in  a  glass  tube  with  nearly  its  own  weight 
of  metallic  potassium ;  violent  reaction  ensues,  and  silicium  is  set  free. 
When  cold,  the  contents  of  the  tube  are  put  into  cold  water,  which  removes 
the  saline  matter  and  any  residual  potassium,  and  leaves  the  silicium  un- 
touched. So  prepared,  silicium  is  a  dark-brown  powder,  destitute  of  lustre. 
Heated  in  the  air,  it  burns,  and  becomes  superficially  converted  into  silica. 
It  is  also  acted  upon  by  sulphur  and  by  chlorine.  When  silicium  is  strongly 
heated  in  a  covered  crucible,  its  properties  are  greatly  changed;  it  becomes 
darker  in  color,  denser,  and  incombustible,  refusing  to  burn  even  when 
heated  by  the  flame  of  the  oxy-hydrogen  blowpipe. 

According  to  recent  researches  by  Wohler  and  Deville,  silicium,  like 
carbon,  is  capable  of  existing  in  three  different  modifications.  The  modi- 
fication above  mentioned  corresponds  to  the  amorphous  variety  of  carbon 
(lampblack).  The  researches  just  quoted  have  established  the  existence  of 
modifications  corresponding  to  the  diamond,  and  to  the  graphite  variety 
of  carbon.  The  diamond  modification  of  silicium  is  most  readily  obt a ined 
by  introducing  into  a  red-hot  crucible  a  mixture  of  3  parts  of  potassium 
silico-fluoride,  1  part  of  sodium  in  small  fragments,  and  1  part  of  granu- 
lated zinc,  and  heating  to  perfect  fusion.  On  slowly  cooling,  there  is 
formed  a  button  of  zinc,  covered  and  interspersed  with  needle-shaped 
crystals  consisting  of  octohedrons,  joined  in  the  direction  of  the  axis.  This 
crystallized  silicium,  which  may  be  readily  freed  from  zinc  by  treatment 
with  acids,  resembles  crystallized  haematite  in  color  and  appearance:  it 
scratches  glass,  and  fuses  at  a  temperature  approaching  the  melting-point 


2NH4C1 

^  nnii1  )iiintu 

-      2BN      +      B-Os 
Boron              Boric 

Sodium 

chloride. 

nitride.             oxide. 

chloride. 

30H2 
Water. 

•2XTI:i            + 
Ammonia. 

R,0, 
Boric  oxide. 

I  BBra. 

*      Nao0.2B203      -t-       2NII4C1       =      2BN  B,O,  h      wn, 

Anhydrous  »~.-.«..i««i          n,>r«.ti  Boric 

sodium  borate. 
t          2BN  + 

Boron  nitride. 
J   BC1,. 
18* 


210  SILICA. 

of  cast  iron.  The  graphite  modification  of  silicium  is  prepared  by  fusing, 
in  a  Hessian  crucible,  5  parts  of  soluble  glass  (potassium  silicate),  10  parts 
of  cryolite  (sodium  and  aluminium  fluoride),  with  1  part  of  aluminium. 
On  treating  the  resulting  button  of  aluminium  with  hydrochloric  acid,  the 
silicium  remains  in  the  form  of  scaly  crystals,  resembling  graphite,  but  of 
somewhat  brighter  color,  scratching  glass,  like  the  previous  modification. 
It  is  infusible.  Its  specific  gravity  is  2-49. 

SILICA,  or  SILICIC  OXIDE.  —  This  is  the  only  known  oxide; 
it  contains  28  parts  silicium  and  82  parts  oxygen.*  Color- 
less transparent  rock-crystal  consists  of  silica  very  nearly 
in  a  state  of  purity;  common  quartz,  agate,  chalcedony, 
flint,  and  several  other  minerals,  are  also  chiefly  composed 
of  this  substance. 

The  experiment  about  to  be  described  furnishes  silica  in  a 
state  of  complete  purity,  and  at  the  same  time  exhibits  one  of 
the  most  remarkable  properties  of  silicium  —  namely,  its  at- 
traction for  fluorine.    A  mixture  is  made  of  equal  parts  fluor- 
spar and  glass,  both  finely  powdered  and  introduced  into  a 
glass  flask,  with  a  quantity  of  oil  of  vitriol.     A  tolerably 
wide  bent  tube,  fitted  to  the  flask  by  a  cork,  passes  to  the 
bottom  of  a  glass  jar,  into  which  enough  mercury  is  poured 
to  cover  the  extremity  of  the  tube.     The  jar  is  then  half  filled  with  water, 
and  heat  is  applied  to  the  flask. 

The  first  effect  is  the  disengagement  of  hydrofluoric  acid :  this  sub- 
stance, however,  finding  itself  in  contact  with  the  silica  of  the  powdered 
glass,  undergoes  decomposition,  water  and  silicium  fluoride  being  produced. 
The  latter  is  a  permanent  gas,  which  escapes  from  the  flask  by  the  bent  tube. 
By  contact  with  a  large  quantity  of  water,  it  is  in  turn  decomposed,  yield- 
ing silica,  which  separates  in  a  beautiful  gelatinous  condition,  and  an  acid 
liquid,  which  is  a  double  silicium  and  hydrogen  fluoride,  commonly  called 
hydrofluosilicic  or  silicofluoric  acid.f  The  silica  may  be  collected  on  a 
cloth  filter,  well  washed,  dried,  and  heated  to  redness  to  expel  water. 

The  acid  liquid  is  kept  as  a  test  for  barium  and  potassium,  with  which 
it  forms  nearly  insoluble  precipitates,  the  double  fluoride  of  silicium  and 
potassium  being  used,  as  was  stated,  in  the  preparation  of  silicium.  Sili- 
cium fluoride,  instead  of  being  condensed  into  water,  may  be  collected  over 
mercury :  it  is  a  permanent  gas,  destitute  of  color,  and  very  heavy.  Ad- 
mitted into  the  air,  it  condenses  the  moisture  of  the  latter,  giving  rise  to  a 
thick  white  cloud.  It  is  important  in  the  experiment  above  described  to 
keep  the  end  of  the  delivery-tube  from  touching  the  water  of  the  jar,  other- 
wise it  almost  instantly  becomes  stopped :  the  mercury  effects  this  object, 

Pure  silica  may  also  be  prepared  by  another  method,  which  is  very  in- 
structive, inasmuch  as  it  is  the  basis  of  the  proceeding  adopted  in  the  ana- 
lysis of  all  siliceous  minerals.  Powdered  rock-crystal  or  fine  sand  is 
mixed  with  about  three  times  its  weight  of  dry  sodium  carbonate,  and  the 
nixture  fused  in  a  platinum  crucible.  When  cold,  the  glassy  mass  is  boiled 
with  water,  by  which  it  is  softened  and  almost  entirely  dissolved.  An  ex- 
it hydrochloric  acid  is  then  added  to  the  filtered  liquid,  and  the  whole 

*  Si02. 

t  (1)  Reaction  of  hydro-fluoric  acid  upon  silica  • 

+  Si02     -     20II2        +        SiF4 

Hydrofluonc  gUfol          Water.        *    Silicfum 

acid-  fluoride. 

(2)  Decomposition  of  fluoride  of  silicium  by  water: 
SiP4      +        OJJ        -      Si 


silicic  acid. 


COMPOUNDS  OF  SILICIUM.  211 

evaporated  to  complete  drynes.s.  By  this  treatment  the  gelatinous  silica 
thrown  down  by  the  acid  becomes  completely  insoluble,  and  remains  behind 
when  the  dry  saline  mass  is  treated  with  acidulated  water,  by  which  the 
alkaline  salts,  alumina,  ferric  oxide,  lime,  and  many  other  bodies  which 
may  happen  to  be  present,  are  removed.  The  silica  is  washed,  dried,  and 
heated  to  redness. 

The  most  prominent  characters  of  silica  are  the  following:  it  is  a  very 
fine,  white,  tasteless  powder,  having  a  density  of  about  2 -60,  fusible  only 
by  the  oxy-hydrogen  blowpipe.  When  once  dried,  silica  is  not  sensibly 
soluble  in  water  or  dilute  acids  (with  the  exception  of  hydrofluoric  acid). 
But  on  adding  hydrochloric  acid  to  a  very  dilute  solution  of  potassium  sili- 
cate, the  liberated  silica  remains  in  solution.  From  this  mixed  solution  of 
silica  and  potassium  chloride,  the  latter  may  be  separated  by  diffusion 
(comp.  p.  149),  whereby  a  moderately  concentrated  solution  of  silica  in 
water  is  obtained.  This  solution  has  a  distinctly  acid  reaction :  it  presents, 
however,  but  little  stability.  When  kept  for  some  time,  it  gelatinizes,  the 
silica  separating  in  the  insoluble  modification.  The  same  effect  is  produced 
by  the  addition  of  a  few  drops  of  sulphuric  or  nitric  acid,  or  of  a  solution 
of  salt. 

Silica  is  essentially  an  acid  oxide,  forming  salts  with  basic  metallic 
oxides,  and  decomposing  all  salts  of  volatile  acids  when  heated  with  them. 
In  strong  alkaline  liquids  it  is  freely  soluble.  When  heated  with  bases, 
especially  those  which  are  capable  of  undergoing  fusion,  it  unites  with 
them  and  forms  salts,  which  are  sometimes  soluble  in  water,  as  in  the  case 
of  the  potassium  and  sodium  silicates,  when  the  proportion  of  base  is  con- 
siderable. Common  glass  is  a  mixture  of  several  silicates,  in  which  the 
reverse  of  this  happens,  the  silica  being  in  excess.  Even  glass,  however, 
is  slowly  acted  upon  by  water. 

Finely  divided  silica  is  highly  useful  in  the  manufacture  of  porcelain. 

SILICIUM  HYDRIDE,  or  SILICATED  HYDROGEN,  was  discovered  by  Buff  and 
Wohler,  who  obtained  this  gas  by  passing  an  electric  current  through  a 
solution  of  sodium  chloride,  the  positive  pole  employed  consisting  of  alu- 
minium containing  silicium.  More  recently  Wohler  and  Martius  produced 
this  gas  by  treating  magnesium  containing  s-dlicium  with  hydrochloric  acid. 
Both  methods  yield  silicium  hydride  mixed  with  free  hydrogen.  Friedel 
and  Ladenburg,  however,  by  a  process  which  will  be  described  further  on, 
have  obtained  it  pure,  and  shown  that  it  consists  of  28  parts  by  weight  of 
silicium  and  4  parts  of  hydrogen.*  Silicium  hydride  is  a  colorless  gas.  In 
the  impure  state,  as  obtained  by  the  two  processes  above  given,  it  takes 
fire  spontaneously  on  coming  in  contact  with  the  air,  and  burns  with  a 
white  flame  evolving  clouds  of  silica.  Pure  silicium  hydride,  however,  does 
not  ignite  spontaneously  under  the  ordinary  atmospheric  pressure ;  but  on 
passing  a  bubble  of  air  into  the  rarefied  gas  standing  over  mercury,  it  takes 
fire,  and  yields  a  deposit  of  amorphous  silicium  mixed  with  silica.  On 
passing  silicium  hydride  through  a  red-hot  tube,  it  is  decomposed,  silicium 
being  deposited. 

COMPOUNDS  OF  SILICIUM  AND  CHLORINE.  —  Silicium  unites  directly  with 
chlorine,  forming  a  tetrachloride.f  This  compound  is  obtained  by  mixing 
finely  divided  silica  with  charcoal  powder  and  oil,  strongly  heating  the 
mixture  in  a  covered  crucible,  and  then  exposing  the  mass  so  obtained  in  a 
porcelain  tube  heated  to  full  redness,  to  the  action  of  perfectly  dry  chlorine 
gas.  A  good  condensing  arrangement,  supplied  with  ice-cold  water,  must 
be  connected  with  the  porcelain  tube.  The  product  is  a  colorless  and  very 
volatile  liquid,  boiling  at  50°,  of  pungent,  suffocating  odor.  In  contact 

*  SiH<.  t  Si014. 


212 


PHOSPHORUS. 


with  water,  it  yields  hydrochloric  acid  and  gelatinous  silica.  This  sub- 
stance contains  28  parts  silicium  and  142  chlorine. 

When  hydrochloric  acid  gas  is  passed  over  crystallized  silicium,  heated 
to  a  temperature  below  redness,  a  very  volatile  inflammable  liquid  is  ob- 
tained, which,  when  purified  by  distillation,  has  the  composition  of  silicium 
hydrolrichloride,*  containing  28  parts  silicium,  1  hydrogen,  and  106-5 
chlorine.  This  compound  is  decomposed  by  water,  forming  a  white  oxy- 
genated body,  probably  silicium  hydrotrioxide,^  which  by  prolonged  contact 
with  water  is  further  decomposed,  with  evolution  of  hydrogen  and  forma- 
tion of  silica. 

A  mixture  of  silicium  hydrotrichloride  and  bromine,  heated  to  100°  in  a 
closed  vessel,  becomes  dark-colored,  and  is  converted  into  the  bromotri- 
chloride.  J 

Silicium  tetrabromide,%  obtained  like  the  tetrachloride,  resembles  that 
compound,  but  is  less  volatile. 


PHOSPHORUS, 

Phosphorus  in  the  state  of  phosphoric  acid  is  contained  in  the  ancient 
unstratified  rocks,  and  in  the  lavas  of  modern  origin.  As  these  disintegrate 
and  crumble  down  into  fertile  soil,  the  phosphates  pass  into  the  organism 
of  plants,  and  ultimately  into  the  bodies  of  the  animals  to  which  these 
latter  serve  for  food.  The  earthy  phosphates  play  a  very  important  part- 
in  the  structure  of  the  animal  frame,  by  communicating  stiffness  and  in- 
flexibility to  the  bony  skeleton. 

Phosphorus  was  discovered  in  1669  by  Brandt,  of  Hamburg,  who  pre- 
pared it  from  urine.  The  following  is  an  outline  of  the  process  now 
adopted.  Thoroughly  calcined  bones  are  reduced  to  powder,  and  mixed 
with  two  thirds  of  their  weight  of  sulphuric  acid  diluted  with  a  considerable 
quantity  of  water:  this  mixture,  after  standing  some  hours,  is  filtered,  and 
the  nearly  insoluble  calcium  sulphate  is  washed. 
14°-  The  liquid  is  then  evaporated  to  a  syrupy  con- 

sistence, mixed  with  charcoal  powder,  and  the 
desiccation  completed  in  an  iron  vessel  exposed 
to  a  high  temperature.  When  quite  dry,  it  is 
transferred  to  a  stoneware  retort,  to  which  a 
wide,  bent  tube  is  luted,  dipping  a  little  way 
into  the  water  contained  in  the  receiver.  A 
narrow  tube  serves  to  give  issue  to  the  gases, 
which  are  conveyed  to  a  chimney.  This  manu- 
facture is  now  conducted  on  a  very  large  scale, 
the  consumption  of  phosphorus,  for  the  appar- 
ently trifling  article  of  instantaneous-light 
matches,  being  something  prodigious. 

Phosphorus,  when  pure,  very  much  resembles 
in  appearance  imperfectly  bleached  wax,  and  is 
soft  and  flexible  at  common  temperatures.  Its 
density  is  1-77,  and  that  of  its  vapor  4-35,  air  being  unity,  or  62  referred 
to  hydrogen  as  unity.  It  melts  at  44°  (111°  F.),  and  boils  at  280°  (536°  F.). 
On  slowly  cooling  melted  phosphorus,  well  formed  dodecahedrons  are  some- 
times obtained.  It  is  insoluble  in  water,  and  is  usually  kept  immersed  in 


*  SiHCl3. 


§  SiBr<. 


PHOSPHORUS.  213 

that  liquid,  but  dissolves  in  oils,  in  native  naphtha,  and  especially  in  car- 
bon bisulphide.  When  set  on  fire  in  the  air,  it  burns  with  a  bright  flame, 
generating  phosphoric  oxide.  Phosphorus  is  exceedingly  inflammable;  it 
sometimes  takes  fire  by  the  heat  of  the  hand,  and  demands  great  care  in 
its  management ;  a  blow  or  hard  rub  will  very  often  kindle  it.  A  stick  of 
phosphorus  held  in  the  air  always  appears  to  emit  a  whitish  smoke,  which 
in  the  dark  is  luminous.  This  effect  is  chiefly  due  to  a  slow  combustion 
which  the  phosphorus  undergoes  by -the  oxygen  of  the  air,  and"  upon  it 
depends  one  of  the  methods  employed  for  the  analysis  of  air,  as  already 
described.  It  is  singular  that  the  slow  oxidation  of  phosphorus  may  be 
entirely  prevented  by  the  presence  of  a  small  quantity  of  olefiant  gas,  or 
the  vapor  of  ether,  or  some  essential  oil;  phosphorus  may  even  be  distilled 
in  an  atmosphere  containing  vapor  of  oil  of  turpentine  in  considerable 
quantity.  Neither  does  the  action  go  on  in  pure  oxygen  —  at  least,  at  the 
temperature  of  15-5°  (60°  F.),  which  is  very  remarkable;  but  if  the  gas 
be  rarefied,  or  diluted  with  nitrogen,  hydrogen,  or  carbonic  acid,  oxidation 
is  set  up. 

A  very  remarkable  modification  of  this  element  is  known  by  the  name  of 
amorphous  phosphorus.  It  was  discovered  by  Schrotter,  and  may  be  made 
by  exposing  common  phosphorus  for  fifty  hours  to  a  temperature  of  from 
240°  to  250°,  (464°-482  F0.),  in  an  atmosphere  which  is  unable  to  act  chem- 
ically upon  it.  At  this  temperature  it  becomes  red  and  opaque,  and  insol- 
uble in  carbon  bisulphide,  whereby  it  may  be  separated  from  ordinary 
phosphorus.  It  may  be  obtained  in  compact  masses  when  common  phos- 
phorus is  kept  for  eight  days  at  a  constant  high  temperature.  It  is  a  coher- 
ent, reddish-brown,  infusible  substance,  of  specific  gravity  between  2-089 
and  2-106.  It  does  not  become  luminous  in  the  dark  until  its  temperature 
is  raised  to  about  200°,  nor  has  it  any  tendency  to  combine  with  the  oxygen 
of  the  air.  When  heated  to  260°  (500°  F.),  it  is  reconverted  into  ordinary 
phosphorus. 

Compounds  of  Phosphorus  and  Oxygen. 

When  phosphorus  is  melted  beneath  the  surface  of  hot  water,  and  a 
stream  of  oxygen  gas  forced  upon  it  from  a  bladder,  combustion  ensues, 
and  the  phosphorus  is  converted  in  great  part  into  a  brick-red  powder, 
which  was  formerly  believed  to  be  a  peculiar  oxide  of  phosphorus ;  but 
Schrotter  has  shown  that  it  is  a  mixture,  consisting  chiefly  of  amorphous 
phosphorus. 

There  are  two  definite  oxides  of  phosphorus,  in  which  the  quantities  of 
oxygen  united  with  the  same  quantity  of  phosphorus  are  to  one  another  as 
3  to  5,*  viz. : 

Composition  by  weight. 

Phosphorus.      Oxygen. 

Phosphorus  Trioxide,  or  Phosphorous  oxide  62    -4-     48 

Phosphorus  Pentoxide,  or  Phosphoric  oxide  62     -\~     80 

Both  these  are  acid  oxides,  uniting  with  water  and  metallic  oxides  to 
form  salts,  called  phosphites  said  phosphates  respectively;  the  hydrogen  salts 
being  also  called  phosphorous  and  phosphoric  acid.  There  is  also  another 
oxygen-acid  of  phosphorus,  containing  a  smaller  proportion  of  oxygen, 
called  hypophosphorous  acid,  to  which  there  is  no  corresponding  anhydrous 
oxide. 

Hypophosphorous  Acid,  f —  When  phosphorus  is  boiled  with  a  solution  of 

*  In  symbols :  — 

Phosphorous  oxide      ....        Pa03 

Phosphoric  oxide PS^B- 

f  Hypophosphorous  acid        .        .        .        P02H3. 


214  PHOSPHORUS. 

potash  or  baryta,  water  is  decomposed,  giving  rise  to  phosphoretted  hy- 
drogen, phosphoric  acid,  and  hypophosphorous  acid;  the  first  escapes  as 
gas,  and  the  two  acids  remain  as  barium  salts.*  By  filtration  the  soluble 
hyp'ophosphite  is  separated  from  the  insoluble  phosphate.  On  adding  to 
the  liquid  the  quantity  of  sulphuric  acid  necessary  to  precipitate  the  base, 
the  hypophosphorous  acid  is  obtained  in  solution.  By  evaporation  it  may 
be  reduced  to  a  syrupy  consistence.  The  acid  is  very  prone  to  absorb  more 
oxygen,  and  is  therefore  a  powerful  deoxidizing  agent.  All  its  salts  are 
soluble  in  water. 

PHOSPHOROUS  OXIDE  is  formed  by  the  slow  combustion  of  phosphorus  in 
the  atmosphere;  or  by  burning  that  substance  by  means  of  a  very  limited 
supply  of  dry  air,  in  which  case  it  is  anhydrous,  and  presents  the  aspect 
of  a  white  powder.  Phosphorous  acid  is  most  conveniently  prepared  by 
adding  water  to  the  trichloride  of  phosphorus,  when  mutual  decomposition 
takes  place,  the  oxygen  of  the  water  being  transferred  to  the  phosphorus, 
generating  phosphorous  acid,  and  its  hydrogen  to  the  chlorine,  giving  rise  to 
hydrochloric  acid.f  By  evaporating  the  solution  to  the  consistence  of  syrup, 
the  hydrochloric  acid  is  expelled,  and  the  residue,  on  cooling,  crj-stallizes. 

Phosphorous  acid  is  very  deliquescent  and  very  prone  to  attract  oxygen 
and  pass  into  phosphoric  acid.  When  heated  in  a  close  vessel,  it  is  resolved 
into  phosphoric  acid  and  pure  phosphoretted  hydrogen  gas.  It  is  composed 
of  110  parts  of  phosphorous  oxide  and  54  parts  of  water,  or,  31  phosphorus, 
48  oxygen,  and  3  hydrogen.;); 

The  phosphites  are  of  little  importance. 

PHOSPHORIC  OXIDE  (also  called  Anhydrous  Phosphoric  Acid,  or  Phosphoric 
Anhydride). — When  phosphorus  is  burned  under  a  bell-jar  by  the  aid  of  a 
copious  supply  of  dry  air,  snow-like  phosphoric  oxide  is  produced  in  great 
quantity.  This  substance  exhibits  as  much  attraction  for  water  as  sulphuric 
oxide:  exposed  to  the  air  for  a  few  moments,  it  deliquesces  to  a  liquid,  and 
when  thrown  into  water,  combines  with  the  latter  with  explosive  violence. 
The  water  then  taken  up  cannot  again  be  separated. 

When  nitric  acid  of  moderate  strength  is  heated  in  a  retort  with  which 
a  receiver  is  connected,  and  fragments  of  phosphorus  are  added  singly, 
taking  care  to  suffer  the  violence  of  the  action  to  subside  between  each 
addition,  the  phosphorus  is  oxidized  to  its  maximum,  and  converted  into 
phosphoric  acid.  By  distilling  oif  the  greater  part  of  the  acid,  transferring 
the  residue  in  the  retort  to  a  platinum  vessel,  and  then  cautiously  raising 
the  heat  to  redness,  the  acid  may  be  obtained  pure.  This  is  the  glacial 
phosphoric  acid  of  the  Pharmacopoeia. 

A  third  method  consists  in  taking  the  acid  calcium  phosphate  produced 
by  the  action  of  sulphuric  acid  on  bone-earth,  precipitating  it  with  a  slight 
excess  of  ammonia  carbonate,  separating  by  a  filter  the  insoluble  calcium- 
salt,  and  then  evaporating  and  igniting  in  a  platinum  vessel  the  mixed 
phosphate  and  sulphate  of  ammonia.  Phosphoric  acid  alone  remains 
behind.  The  acid  thus  obtained  is  not  remarkable  for  its  purity.  One  of 
the  most  advantageous  methods  of  preparing  phosphoric  acid  on  the  large 
scale  in  a  state  of  purity  is  to  burn  phosphorus  in  a  stream  of  dry  atmos- 
pheric air,  by  the  aid  of  a  proper  apparatus,  not  difficult  to  contrive,  in 
which  the  process  may  be  carried  on  continuously.  The  phosphoric  oxide 

*         P8        + 
Phosphorus. 

t        PC13 
Phosphorus 
trichloride. 

=       2P03II3. 


3BaH202 
Barium 

+        6H20        = 
Water. 

3BaH4(P02)2        4 
Barium 

-        2PH3 

Hydrogen 

hydrate. 

hydrophosphite. 

phosphide. 

30H2 
Water. 

=        P03H3        - 
Phosphorous 

f        3HC1 
Hydrochloric 

acid. 

acid. 

PHOSPHORUS. 


215 


obtained  may  be  preserved  in  that  state,  or  converted  into  hydrate  or 
glacial  acid,  by  the  addition  of  water  and  subsequent  fusion  in  a  platinum 
vessel.  The  glacial  phosphoric  acid  is  exceedingly  deliquescent,  and  re- 
quires to  be  kept  in  a  closely  stopped  bottle.  It  contains  142  parts  of  phos- 
phoric oxide  and  18  parts  of  water,  or  31  phosphorus,  48  oxygen,  and  1 
hydrogen.* 

Phosphoric  oxide  is  readily  volatilized,  and  may  be  sublimed  by  the 
heat  of  an  ordinary  spirit-lamp.  The  acid  may  be  fused  in  a  platinum 
crucible  at  a  red  heat;  at  this  temperature,  it  evolves  considerable  quan- 
tities of  vapor,  but  is  still  far  from  its  boiling-point.  Phosphoric  acid  is  a 
very  powerful  acid :  being  less  volatile  than  sulphuric  acid,  it  expels  the 
latter  at  higher  temperatures,  although  it  is  displaced  by  sulphuric  acid 
at  the  common  temperature.  Its  solution  has  an  intensely  sour  taste,  and 
reddens  litmus-paper;  it  is  not  poisonous. 

The  best  reagent  for  the  detection  of  phosphoric  acid  is  molybdate  of 
ammonia.  A  solution  of  this  salt  is  treated  with  hydrochloric  or  nitric 
acid  until  the  precipitate  at  first  formed  is  redissolved.  A  very  small 
quantity  of  the  liquid  to  be  tested  for  phosphoric  acid  is  then  added  to 
this  solution.  If  phosphoric  acid  be  present,  the  liquid  becomes  yellow, 
and  a  yellow  deposit,  consisting  of  molybdic  acid,  phosphoric  acid,  and 
ammonia,  is  formed,  even  if  the  quantity  of  phosphoric  acid  be  very  small. 

There  are  few  bodies  that  present  a  greater  degree  of  interest  to  the 
chemist  than  this  substance :  the  changes  its  compounds  undergo  by  the 
action  of  heat,  chiefly  made  known  to  us  by  the  admirable  researches  of 
Professor  Graham,  will  be  described  in  connection  with  the  general  his- 
tory of  saline  compounds. 

Compounds  of  Phosphorus  and  Hydrogen. 

PHOSPHORUS  TRIHYDRIDE. — PHOSPHINE. — PHOSPHORETTED  HYDROGEN. 
This  body  is  analogous  in  some  of  its  chemical  relations  to  ammoniacal 
gas ;  its  alkaline  properties  are,  however,  much  weaker. 

It  may  be  obtained  in  a  state  of  purity  by  heating  phosphorous  acid  in  a 
small  retort,  the  acid  being  then  resolved  into  phosphoretted  hydrogen 
and  phosphoric  acid.f 

Thus  obtained,  the  gas  has  a  density  of  1-24.  It  contains  31  parts  phos- 
phorus and  3  parts  hydrogen,  and  is  so  constituted  that  every  two  volumes 
contain  3  volumes  of  hydrogen  and  half  a  volume  of  phosphorus  vapor, 
condensed  into  two  volumes.  It  possesses  a  highly  disagreeable  odor  of 
garlic,  is  slightly  soluble  in  water,  and  burns  with  a  brilliant  white  flame, 
forming  water  and  phosphoric  acid. 

Phosphoretted  hydrogen  may  also  be  produced  by  boiling  together,  in  a 
retort  of  small  dimensions,  caustic  potash  or  slaked  lime,  water,  and  phos- 
phorus: the  vessel  should  be  filled  to  the  neck,  and  the  extremity  of  the 
latter  made  to  dip  into  the  water  of  the  pneumatic  trough.  In  the  reaction 
which  ensues,  the  water  is  decomposed,  and  both  its  elements  combine 
with  the  phosphorus. 

f  Hydrogen  __ -^--j  Phosphoretted  hydrogen. 

'      I  Oxygen 
Phosphorus 

Phosphorus 

Lime       ~  '     Cnl"1'"™  hypophosphite.J 


*  P206.H20 

—        2P03H. 

t       4P03H3 
Phosphorous 

=        PH3        + 
Phosphine. 

3P04TI3 

Phosphoric 

„ 

acid. 

acid. 

t            PS        H 
Phosphorus. 

3CaH202 
Calcium 
hydrate. 

+        60H2 
Water, 

=        2PH3        -4 
Phosphine. 

3P204CaTI4 
Calcium  hypo- 
phosphite. 

216  PHOSPHOEUS. 

The  phosphoretted  hydrogen  prepared  by  the  latter  process  has  the  sin- 
gular property  of  spontaneous  inflammability  when  admitted  into  the  air 
or  into  oxygen  gas ;  with  the  latter,  the  experiment  is  very  beautiful,  but 
requires  caution :  the  bubbles  should  be  admitted  singly.  When  kept  over 
water  for  some  time,  the  gas  loses  this  property,  without  otherwise  suffer- 
ing any  appreciable  change ;  but  if  dried  by  calcium  chloride,  it  may  be 
kept  unaltered  for  a  much  longer  time.  M.  Paul  Thenard  has  shown  that 
the  spontaneous  combustibility  of  the  gas  arises  from  the  presence  of  the 
vapor  of  a  liquid  hydrogen  phosphide,  which  can  be  procured  in  small 
quantity,  by  conveying  the  gas  produced  by  the  action  of  water  on  calcium 
phosphide  through  a  tube  cooled  by  a  freezing  mixture.  This  substance 
forms  a  colorless  liquid  of  high  refractive  power  and  very  great  volatility. 
It  does  not  freeze  at — 17-8°  (0°  F.)  In  contact  with  air,  it  inflames  instantly, 
and  its  vapor  in  very  small  quantity  communicates  spontaneous  inflamma- 
bility to  pure  phosphoretted  hydrogen,  and  to  all  other  combustible  gases. 
It  is  decomposed  by  light  into  gaseous  phosphoretted  hydrogen,  and  a 
solid  phosphide  which  is  often  seen  on  the  inside  of  jars  containing  gas 
which,  by  exposure  to  light,  has  lost  the  property  of  spontaneous  inflam- 
mation. Strong  acids  occasion  its  instantaneous  decomposition.  It  is  as 
unstable  as  hydrogen  dioxide.  It  is  to  be  observed  that  the  pure  phospho- 
retted hydrogen  gas  itself  becomes  spontaneously  inflammable  if  heated  to 
the  temperature  of  boiling  water.* 

Phosphoretted  hydrogen  decomposes  several  metallic  solutions,  giving 
rise  to  precipitates  of  insoluble  phosphides.  With  hydriodic  acid  it  forms 
a  crystalline  compound  somewhat  resembling  sal-ammoniac. 

Compounds  of  Phosphorus  with  Chlorine. 

Phosphorus  forms  two  chlorides,  analogous  in  composition  to  the  oxides, 
the  quantities  of  chlorine  combined  with  the  same  quantity  of  phosphorus 
being  to  one  another  in  the  proportion  of  3  to  5. 

PHOSPHORUS  TRICHLORIDE,  or  PHOSPHOROUS  CHLORIDE, •}•  is  prepared  in 
the  same  manner  as  sulphur  bichloride,  by  gently  heating  phosphorus  in 
dry  chlorine  gas.  the  phosphorus  being  in  excess;  or  by  passing  the  vapor 
of  phosphorus  over  fragments  of  calomel  (mercurous  chloride)  contained 
in  a  glass  tube,  and  strongly  heated.  It  is  a  colorless,  thin  liquid,  which 
fumes  in  the  air,  and  has  a  powerful  and  offensive  odor.  Its  specific  gravity 
is  1.45.  Thrown  into  water,  it  sinks  to  the  bottom  of  that  liquid,  and  is 
slowly  decomposed,  yielding  phosphorous  acid  and  hydrochloric  acid.J  It 
contains  31  parts  phosphorus  and  106-5  parts  chlorine. 

PHOSPHORUS  PENTACHLORIDE,  or  PHOSPHORIC  CHLORIDE,  $  is  formed  when 
phosphorus  is  burned  in  excess  of  chlorine.  Pieces  of  phosphorus  are  in- 
troduced into  a  large  tubulated  retort,  which  is  then  filled  with  dry  chlorine 
gas.  The  phosphorus  takes  fire,  and  burns  with  a  pale  flame,  forming  a 
white  volatile  crystalline  sublimate,  which  is  the  pentachloride.  It  may  be 
obtained  in  larger  quantity  by  passing  a  stream  of  dry  chlorine  gas  into 
the  preceding  liquid  trichloride,  which  becomes  gradually  converted  into 
a  solid  crystalline  mass.  Phosphorus  pentachloride  is  decomposed  by 
water,  yielding  phosphoric  and  hydrochloric  acids.  || 

*  Ann.  Chim.  Phys.,  3d  scries,  xiv.  5.     According  to  M.  P.  Thgnard,  the  liquid  phosphide  of 
hydrogen  contains  PH2  and  the  solid  P2H.    The  gas  is  represented  by  the  formula  PH3. 
t  PC18. 

I  PC18     +    30H2    =    3HC1     +    P03H3. 
?  PC15. 
|  PC15    +    40H2    =    5HC1    +    P04H3. 


PHOSPHORUS.  217 

PHOSPHORUS  OXYCHLORIDE.*  —  When  phosphorus  pentachloride  is  heated 
with  a  quantity  of  water  insufficient  to  convert  it  into  phosphoric  acid,  it 
yields,  together  with  hydrochloric  acid,  a  compound  of  phosphorus,  chlo- 
rine, and  oxygen.  This  body  may  also  be  prepared  by  distilling  the  pen- 
tachloride with  dehydrated  oxalic  acid,  or  by  distilling  a  mixture  of  phos- 
phorus pentachloride  and  phosphoric  oxide.  Phosphorus  oxychloride  is  a 
colorless  liquid  of  sp.  gr.  1-7,  possessing  a  very  pungent  odor,  and  boiling 
at  110°  (230°  F.).  It  is  readily  decomposed  by  water  into  hydrochloric 
and  phosphoric  acids. 

A  sulphochloride  f  of  analogous  composition  is  produced  by  the  action  of 
hydrogen  sulphide  on  the  pentachloride.  It  is  a  colorless,  oily  liquid, 
decomposed  by  water. 

Two  bromides  of  phosphorus,  an  oxybromide  and  a  sulphobromide,  are  known, 
corresponding  in  composition  and  properties  with  the  chlorine  compounds, 
and  obtained  by  similar  processes. 

Phosphorus  forms  also  two  iodides^  containing  31  parts  of  phosphorus 
with  2  X  127  and  3  X  127  parts  of  iodine.  The  latter  is  analogous  in 
composition  to  the  trichloride ;  the  former  has  no  chlorine  representative. 
Both  these  compounds  are  obtained  by  dissolving  phosphorus  and  iodine 
together  in  carbon  bisulphide,  and  cooling  the  liquid  till  crystals  are  de- 
posited. Whatever  proportions  of  iodine  and  phosphorus  may  be  used, 
these  two  compounds  always  crystallize  out,  mixed  with  excess  either  of 
iodine  or  of  phosphorus. 

The  di-iodide  melts  at  110°  (230°  F.),  forming  a  red  liquid  which  condenses 
to  a  light  red  solid.  The  tri-iodide  melts  at  55°  (131°  F.),  and  crystallizes 
on  cooling  in  well  denned  prisms.  Both  are  decomposed  by  water,  yielding 
hydriodic  and  phosphorous  acids,  the  di-iodide  also  depositing  yellow 
flakes  of  phosphorus. 

Compounds  of  Phosphorus  with  Sulphur  and  Selenium. 

SULPHIDES.  — When  ordinary  phosphorus  and  sulphur  are  heated  together 
in  the  dry  state,  or  melted  together  under  water,  combination  takes  place 
between  them,  attended  with  vivid  combustion  and  often  with  violent  ex- 
plosion. AVhen  amorphous  phosphorus  is  used,  the  reaction  is  not  explosive, 
though  still  very  rapid. 

Six  compounds  of  sulphur  and  phosphorus  have  been  prepared,  contain- 
ing the  following  proportions  of  sulphur  and  phosphorus,  g 

Composition  by  weight. 

Phosphorus.        Sulphur. 

Hemisulphide         .         .         .         .         .  31  -(- 

Monosulphide    .         .         .         .         .  31  -j-       16 

Sesquisulphide 31  24 

Trisulphide 31  48 

Pentasulphide 31 

Dodecasulphide          .         .         .         .  31  -j-     -^2 

The  fourth  and  fifth  are  analogous  to  phosphorus  and  phosphoric  oxides 
respectively ;  the  others  have  no  known  analogues  in  the  oxygen  series. 
They  may  all  be  formed  by  heating  the  two  bodies  together  in  the  required 
proportions;  but  the  trisulphide  and  pentasulphide  are  more  easily  pre- 
pared by  warming  the  monosulphide  with  additional  proportions  of  sulphur. 
Moreover,  the  two  lower  sulphides  exhibit  isomeric  modifications,  each 
being  capable  of  existing  as  a  colorless  liquid  and  as  a  red  solid.  The 

*  POC13.  t  PSC12.  t  P12  and  I>13. 

§  P4S,        P2S,        P4S3,        P2S3,        P2S5,        and 
19 


218  PHOSPHORUS. 

mono-,  tri-,  and  pentasulphides  of  phosphorus  unite  with  metallic  sulphides, 
forming  sulphur-salts.* 

SELENIDES  OF  PHOSPHORUS,  f  analogous  in  composition  to  the  first,  second, 
fourth,  and  fifth  of  the  sulphides  -above  mentioned,  are  produced  by  heat- 
ing ordinary  phosphorus  and  selenium  together  in  the  required  proportions 
in  a  stream  of  hydrogen  gas.  The  hemiselenide  is  a  dark-yellow,  oily, 
fetid  liquid,  solidifying  at  12°;  the  other  compounds  are  dark-red  solids. 
The  mono-,  tri-,  and  pentaselenides  unite  with  metallic  selenides,  forming 
selenium-salts  analogous  to  the  sulphur-salts  above  mentioned. 


*  Copper  Hyposulphophosphite  P2S2Cn  =  CuS.P2S. 

Copper  Siilphophosphite  P2S4Cu  =:  CuS.P2S3. 

Copper  Sulphophosphate  P~2S6Cu  =  CuS.P2S6. 
f  PSe,  P2Se,  P2Se3>  and  P2Se6. 


ON  THE  GENERAL  PRINCIPLES  OF  CHEMICAL 
PHILOSOPHY. 

rpHE  study  of  the  non-metallic  elements  can  be  pushed  to  a  very  consider- 
l  able  extent,  and  a  large  amount  of  precise  and  exceedingly  important 
information  acquired,  without  much  direct  reference  to  the  great  funda- 
mental laws  of  chemical  union.  The  subject  cannot  be  discussed  in  this 
manner  completely,  as  will  be  obvious  from  frequent  cases  of  anticipation 
.in  many  of  the  foregoing  foot-notes :  still,  much  may  be  done  by  this  simple 
method  of  proceeding.  The  bodies  themselves,  in  their  combinations,  fur- 
nish admirable  illustrations  of  the  general  laws  referred  to ;  but  the  study 
of  their  leading  characters  and  relations  does  not  of  necessity  involve  a 
previous  knowledge  of  these  laws  themselves. 

It  is  thought  that  by  such  an  arrangement  the  comprehension  of  these 
very  important  general  principles  may  become,  in  some  measure,  facili- 
tated by  constant  reference  to  examples  of  combinations,  the  elements  and 
products  of  which  have  already  been  described.  So  much  more  difficult  is 
it  to  gain  a  clear  and  distinct  idea  of  any  proposition  of  great  generality 
from  a  simple  enunciation,  than  to  understand  the  bearing  of  the  same  law 
when  illustrated  by  a  single  good  and  familiar  instance. 

Before  proceeding  further,  however,  it  is  absolutely  necessary  that  these 
matters  should  be  discussed:  the  metallic  compounds  are  so  numerous, 
that  the  establishment  of  some  general  principle,  some  connecting  link, 
becomes  indispensable.  The  doctrines  of  equivalence  and  combining  pro- 
portions, and  the  laws  which  regulate  the  formation  of  saline  compounds, 
supply  this  deficiency. 

THE  LAWS  OP  COMBINATION  BY  WEIGHT. 

(1.)  Constancy  of  Composition. — This  is  the  main  distinction  between 
chemical  combination  and  mechanical  mixture,  or  that  kind  of  adhesion 
which  gives  rise  to  the  solution  of  a  solid  in  a  liquid.  Metals  may  be  fused 
together  to  form  alloys;  water  may  be  mixed  with  alcohol,  alcohol  with 
ether,  and  diiferent  oils  one  with  the  other,  in  any  proportions  whatever, 
the  mixture  always  exhibiting  properties  intermediate  between  those  of  its 
constituents,  and  in  regular  gradation  according  to  the  quantity  of  each 
that  may  be  present;  a  solid  body  may  be  dissolved  in  a  liquid  —  salt  or 
sugar  in  water,  for  example  —  in  any  proportion  up  to  a  certain  limit,  the 
solution  likewise  exhibiting  a  regular  gradation  of  physical  properties, 
according  to  the  quantity  of  the  solid  taken  up.  But  in  a  true  chemical 
compound,  the  properties  of  the  constituent  elements  admit  of  no  variation 
whatever.  Water,  whether  obtained  from  natural  sources,  or  formed  by 
direct  combination  of  its  elements,  always  contains  in  100  parts,  88-9  parts 
of  oxygen  and  11-1  parts  of  hydrogen;  and  a  piece  of  flint,  or  rock-crystal, 
obtained  from  any  part  of  the  world,  invariably  contains  46-6  per  cent,  of 
silicium  to  53-4  of  oxygen.  When  two  or  more  compounds  are  formed  of 
the  same  elements,  as  the  oxides  of  carbon  and  the  chlorides  of  phosphorus 
(pp.  1G4,  216),  there  is  no  gradual  blending  of  one  into  the  other,  as  in  the 
case  of  mixtures ;  but  each  compound  is  sharply  defined  and  separated,  as 
it  were,  from  the  others  by  an  impassable  gulf,  exhibiting  properties  dis- 


220  GENERAL    PRINCIPLES  OF 

tinct  from  those  of  the  others,  and  of  the  elements  themselves  in  the  sepa- 
rate state.  Thus  of  the  two  oxides  of  carbon,  the  monoxide  is  an  inflam- 
mable gas,  lighter  than  air,  and  not  absorbed  by  solution  of  potash,  whereas 
the  dioxide  is  non-inflammable,  heavier  than  air,  and  easily  absorbed  by 
potash;  and  both  compounds  differ  entirely  in  their  characters,  both  from 
carbon  and  from  oxygen  in  the  free  state. 

The  composition  of  chemical  compounds  is  ascertained,  as  already  ob- 
served, by  analysis,  and  in  some  cases  also  by  synthesis.  The  results  are 
usually  stated  in  percentages  (thus,  100  parts  of  zinc  oxide  contain  80-1 
parts  zinc  and  19  9  oxygen),  which  for  many  purposes  is  as  convenient  a 
method  as  can  be  adopted.  But  when  it  is  desired  to  compare  the  compo- 
sition of  several  compounds  of  the  same  elements,  or  of  the  compounds 
formed  by  one  element  with  several  others,  it  is  more  convenient  to  start 
with  a  fixed  quantity  of  the  first  element,  and  specify  the  relative  quan- 
tities of  the  other  element  or  elements  which  combine  with  it.  This  will 
be  easily  seen  by  comparing  the  following  tabular  statements  of  the  com-, 
position  of  the  five  nitrogen  oxides  already  described,  first,  in  percentages, 
secondly,  by  stating  the  several  quantities  of  oxygen  which  unite  with  100 
parts  of  nitrogen. 

!„  100  part, 


Nitrogen.  Oxygen.  Nitrogen.  Oxygen. 

Monoxide      .         .         63-64  36-36  100  175 

Dioxide     .         .         .     46-67  53-33  100  350 

Trioxide        .      •  .         36.85  63-15  100  525 

Tetroxide          .         .     30-44  69-56  100  700 

Pentoxide      .         .         25-93  74-07  100  875 

The  numbers  on  the  left-hand  side  of  the  table  do  not  exhibit  any  simple 
relation ;  but  on  looking  to  the  right-hand  side,  it  is  immediately  seen  that 
the  quantities  of  oxygen  which  unite  with  the  same  quantity  of  nitrogen, 
are  to  one  another  as  the  numbers  1,  2,  3,  4,  5.  And  this  leads  us  to  the 
second  general  law  of  chemical  combination,  viz. :  • 

(2.)  The  Law  of  Multiples.  —  This  law  may  be  thus  stated:  If  two  ele- 
ments, A  and  B,  are  capable  of  uniting  in  several  proportions,  the  quan- 
tities of  B  which  unite  with  a  given  quantity  of  A,  usually  bear  a  simple 
relation  to  one  another,  such  as : 

A  +  B,        A  -f  2B,        A  +  3B,         A  -f-  4B,  &c. ; 
or,  2A  -f  3B,         2A  -f-  5B,         2A  +  7B,  &c. ; 
or,  A     -f  B,  A  +  3B,          A  -f  5B,  &c. 

Numerous  examples  of  this  law  are  afforded  by  the  compounds  of  the 
non-metallic  elements  one  with  the  other;  as,  for  example,  the  oxides  of 
hydrogen,  carbon,  chlorine,  sulphur,  and  phosphorus,  the  chlorides  of 
phosphorus,  &c. ;  and  still  more  numerous  examples  will  be  met  with,  in 
treating  of  the  compounds  of  metals  with  non-metallic  elements. 

It  must  be  observed,  however,  that  more  complex  relations  are  by  no 
means  unfrequent.  The  compounds  of  carbon  and  hydrogen,  for  example, 
are  very  numerous;  and  on  comparing  together  the  quantities  of  hydrogen 
H,  which  unite  with  a  fixed  quantity  of  carbon  C,  we  meet  with  such  rela- 
tions as  50  -f  17H,  7C  +  16H,  11C  +  24H,  15C  +  32H,  &c.  In  short,  the 
simple  relations  above  mentioned  must  be  looked  upon  merely  as  particular 
instances  of  a  large  number  of  possible  relations,  although  they  happen  to 
hold  good  with  reference  to  a  considerable  number  of  important  compounds. 


CHEMICAL    PHILOSOPHY.  221 

(3.)  Law  of  Equivalents.— If  a  body  A  unites  with  certain  ether  bodies 
B,  C,  D,  then  the  quantities  B,  C,  D,  which  combine  with  A,  or  certain 
simple  multiples  of  them,  represent  for  the  most  part  the  proportions  in 
which  they  can  unite  amongst  themselves. 

For  example,  8  parts  by  weight  of  oxygen  are  known  to  unite  with  the 
following  quantities  of  hydrogen,  nitrogen,  &c. : 

Oxygen          8 

Hydrogen 1 

Nitrogen 14 

Carbon          6 

Sulphur 8 

Phosphorus  .         .         .         .  10J  or  y 

Chlorine 35-5 

Iodine  .         .         .         .         .  25f  or  *f » 

Potassium         ....  39 

Iron 28 

Copper 31-7 

Lead 103-5 

Silver 108 

&c.  &c 

And  it  is  found,  moreover,  that  hydrogen  and  chlorine  combine  in  the  pro- 
portions 1  to  35-5;  hydrogen  and  sulphur,  1  to  2X8;  chlorine  and  silver, 
35-5  to  108;  iodine  and  potassium,  127  parts  of  the  former  to  39  of  the 
latter,  &c. ;  phosphorus  and  chlorine,  31  parts  of  the  former  to  3 x  35-5  and 
5x355  of  the  latter,  &c. 

Now,  on  comparing  the  relative  quantities  of  the  elements  contained  in 
all  known  chemical  compounds,  it  is  found:  1.  That  there  is  a  certain 
number  of  elements  which  combine  with  one  another  in  one  proportion  only. 
2.  That  by  far  the  greater  number  of  elements  are  capable  of  uniting  in 
two  or  more  proportions.  The  elements  of  the  former  class  may  be  con- 
veniently called  monogens,  those  of  the  latter  polygons.* 

Hydrogen  and  chlorine  unite  in  the  proportion  of  1  part,  by  weight,  of 
the  former,  to  35-5  p$,rts  of  the  latter,  and  in  no  other.  The  same  quantity 
of  chlorine  combines  with  39-1  parts  of  potassium,  23  of  sodium,  and  108 
of  silver.  These  several  quantities  of  sodium,  potassium,  and  silver,  are 
capable  of  saturating  the  same  quantity  of  chlorine  that  is  saturated  by  1 
part  of  hydrogen.  They  are,  therefore,  in  this  respect  equivalent  to  1  part 
by  weight  of  hydrogen  and  to  each  other.  They  may,  in  fact,  be  made 
directly  to  replace  one  another  in  combination  with  chlorine.  Thus,  when 
sodium  or  potassium  is  heated  in  hydrochloric  acid  gas,  hydrogen  is  set 
free,  and  sodium  or  potassium  chloride  is  formed,  23  parts  of  sodium  or 
31H  parts  of  potassium  always  taking  the  place  of  1  part  of  hydrogen. 
Again,  when  a  solution  of  sodium  chloride  is  mixed  with  silver  nitrate,  the 
sodium  and  silver  change  places,  forming  a  solution  of  sodium  nitrate  and 
a  precipitate  of  silver  chloride;  and  in  this  case  108  parts  of  silver  take 
the  place  of  23  parts  of  sodium.  The  above-mentioned  quantities  of  hy- 
drogen, chlorine,  sodium,  potassium,  and  silver,  are  therefore  called  equiva- 
lent weights. 

There  are  a  few  other  monogenic  elements,  the  names  and  equivalent 
weights  of  which  are  given,  together  with  the  preceding,  in  the  following 
table : 

*  Erlenmeyer,  "  Lehrbuch  der  organischen  Chemie." 
10* 


222    GENERAL    PRINCIPLES    OF    CHEMICAL    PHILOSOPHY. 


Hydrogen  ...  1 
Chlorine  .  .  .  35-5 
Bromine  .  .  .80 
Fluorine  ...  19 
Silver  .  .  108 


Potassium  .         .         .  89-1 

Sodium    .         .         .  23 

Lithium       ...  7 

Caesium    .         .         .  133 

Rubidium    .  85-4 


All  other  elements  are  polygenic,  uniting  with  the  monogens  and  with 
one  another  in  more  than  one  proportion.  With  regard  to  these  elements 
the  question  of  equivalence  appears  at  first  to  be  somewhat  indeterminate; 
in  fact,  according  to  the  idea  of  equivalency  above  defined,  the  equivalent 
value  of  a  polygenic  element  must  vary  according  to  the  proportions  in 
which  it  unites  with  others.  Thus  iron  forms  two  chlorides,  containing  28 
and  18f  parts  of  iron  to  35.5  parts  of  chlorine.  Either  of  these  quantities 
of  iron  may  therefore  be  regarded  as  equivalent  to  1  part  of  hydrogen ;  in 
other  words,  as  the  equivalent  weight  of  iron.  Again,  1  part  of  hydrogen 
unites  with  8  parts  of  oxygen  to  form  water,  and  with  16  parts  to  form  hy- 
drogen dioxide.  Which  of  these  is  the  equivalent  weight  of  oxygen  ?  The 
former  number  has  perhaps  the  best  right  to  be  so  regarded,  because  water 
is  a  more  stable  compound  than  hydrogen-dioxide,  and,  moreover,  8  parts 
by  weight  of  oxygen  frequently  take  the  place  of  1  part  of  hydrogen  in 
processes  of  oxidation,  as  when  alcohol,  a  compound  of  12  parts  carbon,  3 
hydrogen,  and  8  oxygen,  is  oxidized  to  acetic  acid,  containing  12  parts  car- 
bon, 2  hydrogen,  and  16  oxygen.  But  what  number  shall  we  fix  upon  as 
the  equivalent  of  nitrogen  ?  This  element  forms  only  one  compound  with 
hydrogen,  namely,  ammonia,  which  contains  14  parts  of  nitrogen  to  3  of 
hydrogen,  or  4f  nitrogen  to  1  hydrogen.  Accordingly,  the  equivalent  weight 
of  nitrogen  appears  to  be  4f ,  and,  in  fact,  this  quantity  of  nitrogen  can  be 
made  to  take  the  place  of  1  part  of  hydrogen  in  many  organic  compounds. 
But  if  we  look  to  the  compounds  of  nitrogen  with  oxygen,  we  find  that 
these  elements  unite  in  five  different  proportions,  8  parts  of  oxygen  (which 
we  have  seen  to  be  in  most  cases  equivalent  to  1  part  of  hydrogen)  uniting 
with  14,  7,  !/,  |,  or  ^  parts  of  nitrogen,  either  of  which  numbers  may 
therefore  be  regarded  as  equivalent  to  1  part  of  hydrogen.  Lastly,  with 
regard  to  carbon,  the  problem  appears  still  more  indefinite,  inasmuch  as 
that  element  forms  with  hydrogen  a  very  large  number  of  compounds,  and 
appears  to  be  capable  of  uniting  with  it  in  almost  any  proportion. 

We  may,  however,  obtain  a  set  of  comparable  values  by  assuming  as  the 
equivalent  weight  of  each  polygenic  element,  the  smallest  quantity  of  it  which 
unites  with  1  part  of  hydrogen,  or  with  35-5  of  chlorine,  or  generally  with 
the  equivalent  weight  of  any  monogenic  element.  Thus  of  all  the  compounds 
of  hydrogen  and  carbon,  marsh-gas,  or  methane,  which  is  composed  of  12 
parts  carbon  to  4  hydrogen,  or  3  parts  carbon  to  1  hydrogen,  contains  the 
largest  quantity  of  hydrogen  in  proportion  to  the  carbon ;  in  other  words, 
3  parts  of  carbon  is  the  smallest  quantity  that  can  unite  with  1  part  of 
hydrogen  This,  then,  we  shall  regard  as  the  equivalent  weight  of  carbon ; 
and  by  similar  considerations  the  equivalent  weight  of  oxygen  will  be  found 
to  be  8,  that  of  sulphur  16,  of  nitrogen  4f  or  V,  of  phosphorus  V  or  64,  of 
iron  18f,  of  lead  103-5,  &c. 

ATOMIC  WEIGHTS. — Let  us  now  compare  the  hydrogen  compounds  of 
monogenic  and  polygenic  elements,  with  regard  to  the  manner  in  which 
the  hydrogen  contained  in  them  may  be  replaced  by  other  elements.  Com- 
pare first  hydrochloric  acid  and  water.  When  hydrochloric  acid  is  acted 
upon  by  certain  metals,  as  sodium,  zinc,  or  magnesium,  the  whole  of  the 
hydrogen  is  expelled,  and  the  chlorine  enters  into  combination  with  an 
equivalent  quantity  of  the  metal;  thus  36-5  parts  of  hydrochloric  acid 
(=  1  part  hydrogen  -f-  35-5  chlorine)  and  23  sodium  yield  1  part  of  free 


ATOMIC    WEIGHTS.  223 

hydrogen  and  23  -f-  35-5  (=  58  5)  sodium  chloride;  there  is  no  such  thing 
as  the  expulsion  of  part  of  the  hydrogen,  or  the  formation  of  a  compound 
containing  both  hydrogen  and  metal  in  combination  with  the  chlorine. 

With  water,  however,  the  case  is  different.  When  sodium  is  thrown  upon 
water,  9  parts  of  that  compound  (=  1  hydrogen  -f-  8  oxygen)  are  decom- 
posed, in  such  a  manner  that  half  of  the  hydrogen  is  expelled  by  an  equiv- 
alent quantity  of  sodium,  — ,  and  sodium  hydrate  is  formed  containing : 

Sodium.  Hydrogen.  Oxygen. 

•.'";+          I       +        8 

This  compound  remains  in  the  solid  state  when  the  liquid  is  evaporated 
to  dryness;  and  if  it  be  further  heated  in  a  tube  with  sodium,  the  remaining 
half  of  the  hydrogen  is  driven  off,  and  anhydrous  sodium-oxide  remains, 
composed  of  23  parts  sodium  -j-  8  oxygen. 

Water  differs,  therefore,  from  hydrochloric  acid  in  this  respect,  that 
its  hydrogen  may  be  replaced  by  a  monogenic  metal  in  two  equal  portions, 
yielding  successively  a  hydrate  and  an  anhydrous  oxide,  the  relations  of 
which  to  the  original  compound  may  be  thus  represented :  — 

Water.  Sodium-hydrate.  Sodium-oxide. 

Hydrogen.        Oxygen.  Hyd.  Sod.          Ox.  Sodium.  Ox. 


or,  multiplying  by  2,  to  avoid  fractions  of  equivalent  weights: 

Water.  Sodium-hydrate.  Sodium-oxide. 

Hydrogen.         Oxygen.  Hyd.  Sod.          Ox.  Sodium.  Ox. 

(1   +   1)    +    16  (1     +     23)  +  16        (23  +  23)  +  16. 

It  appears  from  this  that  2  x  8,  or  16  parts  of  oxygen,  is  the  smallest 
quantity  of  oxygen  that  can  be  supposed  to  enter  into  the  reaction  just 
considered,  if  we  would  avoid  speaking  of  fractions  of  equivalents;  and 
we  shall  find  hereafter  that  the  same  is  true  with  regard  to  all  other  well- 
defined  reactions  in  which  oxygen  takes  part.  Hence  this  quantity  of 
.oxygen  16  parts  by  weight  (hydrogen  being  the  unit),  is  called  an  indivisible 
weight,  or  atomic  weight,  or  an  atom  of  oxygen.* 

Let  us  now  consider  the  hydrogen  compound  of  nitrogen,  that  is  to 
say,  ammonia.  This  is  composed  of  1  part  of  hydrogen  united  with  4| 
or  Jg4  of  nitrogen.  Now  in  this  compound  the  hydrogen  is  replaceable  by 
thirds.  When  potassium  is  heated  in  ammonia  gas,  a  compound  called 
potassamine  is  formed,  in  which  one  third  of  the  hydrogen  is  replaced  by 
potassium.  Another  compound,  called  tri-potasxamine,  is  also  known,  con- 
sisting of  ammonia  in  which  the  whole  of  the  hydrogen  is  replaced  by  an 
equivalent  quantity  of  potassium:  — 

Nit.  Hydrogen.  Nit.  Hydrogen. 

Ammonia   .         .     —     +   -  - — |-  --    or     14    +    1    +    1    +    1 

0  O  O  o 

Nit.  Hydrogen.        Pot.  Nit.  Hydrogen.        Pot. 

1  j  1  1  ^0 

Potassamine       .      — -     +  —    +  -  -  +  -5-     or     14    +    1    +    1+39 
6  &  o  o 

Nit.  Potassium.  Nit.  Potassium. 

Tripotassamine        ~     +??+-+-!     or     14  +  39  +    39  +  89 
o  o  o  o 

*  Aro/wj,  indivisible. 


224 


ATOMIC   WEIGHTS. 


There  is  also  a  large  class  of  compounds  derived  from  ammonia  in  like 
manner  by  the  replacement  of  £,  f ,  or  the  whole  of  the  hydrogen  by  equi- 
valent quantities  of  certain  groups  of  elements  called  compound  radicals  (see 
page  237).  Hence,  by  reasoning  similar  to  that  which  was  above  applied 
to  water,  it  is  inferred  that  ammonia  is  composed  of  14  parts  by  weight,  or 
3  equivalents,  of  nitrogen  combined  with  3  parts  or  3  equivalents  of  hydro- 
gen, and  that  the  atomic  weight  of  nitrogen  is  14. 

Next  take  the  case  of  marsh-gas  or  methane,  a  compound  of  1  part  hydro- 
gen with  3  parts  carbon.  When  this  gas  is  mixed  with  chlorine,  and  ex- 
posed to  diffused  daylight,  a  new  compound  is  formed,  in  which  one  fourth 
of  the  hydrogen  belonging  to  the  marsh-gas  is  replaced  by  an  equivalent 
quantity  of  chlorine  ;  and  if  the  chlorine  is  in  excess,  and  the  mixture  ex- 
posed to  sunshine,  three  other  compounds  are  formed,  in  which  one  half, 
three  fourths,  and  all  the  hydrogen,  are  thus  replaced.  The  results  may 
be  thus  expressed : 

Methane. 


Carbon. 


Hydrogen. 


Carbon. 


Hydrogen. 


+ 


Carbon.          Hydrogen. 


ior     12     +     1+1-j- 

Chloromethane. 
Chlorine.        Carbon.       Hydrogen. 


Chlorine. 


35-5 


or     12     +1+1+1 


35-5 


Carbon.         Hydrogen. 


Dichloromethane. 

Chlorine.  Carbon.    Hydrogen.  Chlorine. 


~T~  +  ~4~     or     12  +  1  +  1  +  35-5  +  35-5 


3     4-    —  4-  ^ 


Carbon.    Hyd. 


Trichloromethane  or  Chloroform. 
Chlorine.  Carb.       Hyd. 


Chlorine. 


_          1     ,    35-5  ,     35-5 

+<T  +  T+  ~T~ 


35-5 


or  12 


Carbon. 


Tetrachloromethane. 
Chlorine.  Carbon. 


35-5        35-5       35-5 


35-5 

~  °r  12  +  35' 


35'5  +  35>5      35'5 


Chlorinje. 


35'5  +  35'5  +  35'5 


Hence,  by  reasoning  similar  to  the  above,  it  is  inferred  that  marsh-gas 
is  composed  of  12  parts  by  weight,  or  4  equivalents  of  carbon,  and  4  parts, 
or  4  equivalents  of  hydrogen,  and  that  the  atomic  weight  of  carbon  is  12. 
According  to  the  preceding  explanations,  the  equivalent  weight  of  a  poly- 
enic  element  is  the  smallest  auantitv  of  it,  thnt,  «n.n  nnUo  ™uii  0 


,        1 —      --"&  v/^.^iu,Li«,uiviio,  i,uc  cyuivuieiti  iveiurti  ui    a  poiy- 

genie  element  is  the  smallest  quantity  of  it  that  can  unite  with  an  equiva- 
ic.  element,  that  is,  with  1  part  of  hydrogen,  35-5  parts 


lent  of  a  monogenic ,  __  ,0,  «ilAA  ±  plll-t  ux  ^.u-ogen,  00-0  parts 

)1  chlorine,  &c. ;  and  the  atomic  weight,  or  atom,  is  the  smallest,  quantity  of 
an  element  that  can  unite  with  others  without  introducing  fractions  of 
equivalents.  In  the  case  of  a  monogenic  element,  the  atomic  and  equiva- 
lent weights  are  identical,  but  the  atomic  weight  of  a  polygenic  element  is 
always  greater  than  the  equivalent  weight  in  the  ratio  of  1  to  2  3  4  &c 


ATOMIC   WEIGHTS.  225 

Te  have  shown  in  three  cases  how  the  atomic  weight  of  an  element  may 
be  determined  by  the  proportion  in  which  equivalent  substitution  takes 
place  in  its  compounds  with  hydrogen  or  other  monogenic  elements.  Sul- 
phur, selenium,  and  tellurium  form  hydrogen  compounds  exactly  analogous 
in  tins  respect  to  water,  the  hydrogen  being  replaceable  by  halves;  their 
atomic  weights  are  therefore  double  of  their  equivalent  weights.  Silicon 
forms  with  chlorine  a  compound  containing  7  parts  silicon  with  35-5  parts 
chlorine ;  and  in  this  one  fourth  of  the  chlorine  is  replaceable  by  hydro- 
gen or  by  bromine:  hence  the  atomic  weight  of  silicon  is,  like  that  of 
carbon,  equal  to  four  times  the  equivalent  weight,  its  numerical  value  being 
28.  There  are  also  some  elements  in  which  the  atomic  weight  is  equal 
to  five  times,  and  others  in  which  it  is  equal  to  six  times,  the  equivalent 
weight;  higher  ratios  have  not  been  observed. 

It  must  not  be  supposed  that  the  atomic  weights  of  elementary  bodies 
are  always  actually  determined  in  the  manner  above  described.  There  are 
several  other  methods  of  determining  their  numerical  values,  as  will  be 
presently  explained ;  and  the  values  obtained  by  different  methods  do  not 
always  agree ;  but  the  atomic  weights  of  all  the  more  important  elements 
may  be  regarded  as  definitely  fixed  within  small  numerical  errors.  The 
equivalent  value  of  an  element  or  the  ratio  of  the  equivalent  to  the  atomic 
weight,  is  also  subject  to  some  variation,  as  will  be  presently  explained, 
according  to  the  view  which  may  be  taken  of  the  constitution  of  particular 
compounds. 

The  table  on  the  next  page  exhibits  the  values  of  the  atomic  weights  of  the 
elementary  bodies  in  which  chemists  are  now  for  the  most  part  agreed  ;  also 
the  abbreviated  symbols  (the  first  or  first  two  letters  of  their  Latin  names) 
by  which  they  are  designated  in  chemical  formulae. 

SYMBOLIC  NOTATION.  —  The  symbols,  H,  0,  N,  etc.,  stand,  not  for  the 
names  of  the  several  elements,  but  for  quantities  of  them  proportional  to 
the  atomic  weights.  Combination  between  elements  is  represented  by  the 
juxtaposition  of  the  symbols;  thus  NaCl  represents  sodium  chloride,  a 
compound  of  23  parts  by  weight  of  sodium  with  36-5  parts  of  chlorine. 
Two  or  more  atoms  of  an  element  are  represented  by  placing  a  small  figure 
to  the  right  of  the  symbol,  and  a  little  below ;  thus  H2  denotes  2  atoms  of 
hydrogen;  OH2  denotes  water,  a  compound  of  2  atoms  hydrogen  with  1 
atom  oxygen;  PC15,  phosphorus  pentachloride  ;  Fe203,  iron  sesquioxide,  etc. 
The  elements  in  a  compound  are  usually  placed  in  the  order  of  their  equi- 
valencies, the  highest  to  the  left;  but  this  order  is  often  departed  from 
when,  by  so  doing,  the  relation  between  two  or  more  compounds  under  con- 
sideration can  be  more  clearly  brought  to  light. 

The  union  of  two  atomic  groups,  or  molecules,  is  represented  by  placing 
their  symbols  together,  with  a  point  or  comma  between  them;  thus  sal-am- 
moniac, formed  by  the  union  of  ammonia,  N1I3,  and  hydrochloric  acid,  HC1, 
is  represented  by  the  formula  NH8.HC1:  sulphuric  acid,  or  hydrogen  sul- 
phate, which  may  be  regarded  as  sulphur  trioxide  combined  with  water, 
may  be  represented  by  the  formula  S03.OH2. 

A  number  placed  to  the  left  of  a  group  of  symbols  not  separated  by  a 
point  or  comma,  multiplies  the  entire  group;  thus  30H2  denotes  3  molecules 
of  water ;  but  to  denote  the  multiplication  of  a  molecule  compounded  of  two 
other  molecules,  the  whole  formula  must  be  enclosed  in  brackets,  and  the 
numeral  placed  to  the  left  on  the  line,  or  to  the  right  a  little  below  it ;  thus 
2  molecules  of  sal-ammoniac  are  denoted  by  2(NH3.HC1),  or  (NH3  HC1)2. 

If  the  brackets  were  omitted  in  the  first  of  these  formulae,  the  2  would 
multiply  only  the  part  of  the  formula  to  the  left  of  the  point;  e.  g.  30H2.S08 


226 


ATOMIC  WEIGHTS.' 


TABLE  OF  ELEMENTARY  BODIES  WITH  THEIR  SYMBOLS  AND  ATOMIC 
WEIGHTS. 


Name. 

Symbol. 

Atomic 
Weight. 

Name. 

Symbol. 

Atomic 
Weight. 

Aluminium 

Al 

27-4 

Molybdenum 

Mo 

96 

Antimony  (Sti- 
bium) 

Sb 

122 

Nickel 
Niobium 

Ni 
Nb 

58-8 
94 

Arsenic 

As 

75 

Nitrogen 

N 

14 

Barium 

Ba 

137 

Osmium 

Os 

199-2 

Beryllium 
Bismuth 

Be 
Bi 

94 

210 

Oxygen 
Palladium 

0 
Pd 

16 
106-6 

Boron 

B 

11 

Phosphorus 

P 

31 

Bromine 

Br 

80 

Platinum 

Pt 

1974 

Cadmium 

Cd 

112 

Potassium 

Caesium 

Cs 

133 

(Kalium) 

K 

39-1 

Calcium 

Ca 

40 

Rhodium 

Rh 

104-4 

Carbon 

C 

12 

Rubidium 

Rb 

854 

Cerium 

Ce 

92 

Ruthenium 

Ru 

104-4 

Chlorine 

Cl 

35-5 

Selenium 

Se 

794 

Chromium 

Cr 

52-2 

Silicium 

Si 

28 

Cobalt 

Co 

58-8 

Silver  (Argen- 

Copper      (Cu- 

tum) 

Ag 

108 

prum) 

Cu 

634 

Sodium  (Na- 

Didymium 

D 

95 

trium) 

Na 

23 

Erbium 

E 

112-6 

Strontium 

Sr 

87-6 

Fluorine 

F 

19 

Sulphur 

S 

32 

Gold  (Aurum) 

Au 

197 

Tantalum 

Ta 

182 

Hydrogen 

H 

1 

Tellurium 

Te 

128 

Indium 

In 

74 

Terbium  (?) 

Iodine 

I 

127 

Thallium 

Tl 

204 

Iridium 

Ir 

198 

Thorinum 

Th 

115-7 

Iron  (Ferrum) 

Fe 

56 

Tin  (Stannum) 

Sn 

118 

Lanthanum 

La 

93-6 

Titanium 

Ti 

50 

Lead    (Plum- 

Tungsten, or 

bum) 

Pb 

207 

Wolfram 

W 

184 

Lithium 

Li 

7 

Uranium 

U 

120 

Magnesium 

Mg 

24 

Vanadium 

V 

51-2 

Manganese 

Mn 

55 

Yttrium 

Y 

61-7 

Mercury    (Hy- 

Zinc 

Zn 

65-2 

drargyrum) 

Hg 

200 

Zirconium 

Zr 

89-6 

denotes  a  compound  of  3  molecules  of  water  with  1  molecule  of  sulphur 
trioxide. 

Chemical  reactions  are  represented  by  equations,  in  which  the  symbols 
of  the  acting  bodies  are  placed  on  the  left-hand  side,  and  those  of  the 
bodies  formed  by  the  reaction,  on  the  right  hand,  the  molecules  on  either 
side  being  connected  by  the  sign  •-(-.  For  example,  the  action  of  zinc  on  hy- 
drochloric acid,  by  which  zinc  chloride  and  free  hydrogen  are  formed,  is 
represented  by  the  equation : 

Zn     -f     2HC1     =     ZnCl2     +     H2; 

that  of  phosphorus  pentachloride  on  water,  which  yields  hydrochloric  and 
phosphoric  acids,  by  the  equation: 


PC16     -f     40H2    =     5HC1 


P04H3. 


ATOMIC  WEIGHTS.  227 

Numerous  other  examples  will  be  found  in  the  foot-notes  to  the  preceding 
pages. 

Physical  and  Chemical  Relations  of  Atomic  Weights. 

We  have  hitherto  regarded  the  atomic  weights  of  the  elements  as  mere 
numerical  expressions,  or  as  quantities  adopted  to  represent  the  compo- 
sition of  compounds  without  introducing  fractions  of  equivalents.  If  this 
were  all  that  could  be  said  about  them,  they  would  not  be  of  much  impor- 
tance,. We  shall  see,  however,  that  these  same  quantities  exhibit  some  re- 
markable relations  to  the  physical  properties  of  the  elements,  and  to  the 
proportions  in  which  they  combine  together  by  volume. 

1.  To  the  Specific  Heat  of  the  Elementary  Bodies. — The  atomic  weights  of 
the  elements,  determined  according  to  their  modes  of  combination,  are,  for 
the  most  part,  inversely  proportional  to  their  specific  heats;  so  that  the 
product  of  the  specific  heat  into  the  atomic  weight  is  a  constant  quantity. 
The  same  quantity  of  heat  is  required  to  produce  a  given  change  of  tem- 
perature in  7  grams  of   lithium,  56  of   iron,  207  of  lead,   108  of  silver, 
196-7  of  gold,  210  of  bismuth,  &c. 

This  relation,  already  pointed  out  in  the  chapter  on  Heat  (p.  73),  holds 
good  with  respect  to  the  greater  number  of  the  elements ;  but  it  cannot  be 
regarded  as  a  universal  law,  inasmuch  as  three  elements,  carbon,  silicium, 
and  boron,  whose  atomic  weights  are  well  established  on  chemical  grounds, 
exhibit  unmistakable  exceptions  to  it.  Nevertheless,  in  case  of  doubt  as 
to  the  correct  determination  of  the  atomic  weight  of  an  element  according 
'to  its  mode  of  combination,  the  agreement  of  the  value  thus  obtained  with 
the  value  determined  according  to  the  specific  heat,  is  generally  regarded 
as  affording  strong  evidence  in  favor  of  the  result. 

2.  To  the  Crystalline  Forms  of  Compounds.  —  It  is  found  that,  in  many 
cases,  two  or  more  compounds  which,   from  chemical  considerations,  are 
supposed  to  contain  equal  numbers  of  atoms  of  their  respective  elements, 
crystallize  in  the  same  or  in  very  similar  forms.     Such  compounds  are  said 
to  be  isomorphous.*   Thus  the  sulphates  represented  by  the  general  formula 
S04M2  (M  denoting  a  monogenic  metal)  are  isomorphous  with  the  corre- 
sponding selenates  Se04M2 ;    the  phosphates  P04M3  are  isomorphous  with 
the  corresponding  arsenates  As04M3,  &c. 

Accordingly,  these  isomorphous  relations  are  often  appealed  to  for  the 
purpose  of  fixing  the  constitution  of  compounds,  and  thence  deducing  the 
atomic  weights  of  their  elements,  in  cases  which  would  otherwise  be  doubt- 
ful. Thus  aluminium  forms  only  one  oxide,  viz.,  alumina,  which  is  com- 
posed of  18-2  parts  by  weight  of  aluminium  and  16  parts  of  oxygen.  What, 
then,  is  the  atomic  weight  of  aluminium?  The  answer  to  this  question 
will  depend  upon  the  constitution  assigned  to  alumina,  whether  it  is  a  mon- 
oxide, sesquioxide,  dioxide,  &c.  Thus: 

0.  Al. 

Monoxide  .     A10         =    16     +        18-25 

Sesquioxide    A1208       =    48    -f 

Dioxide      .     A102        =     32     -f        36-5 
Trioxide     .     A103        =     48     -f         54-8 

The  numbers  in  the  last  column  of  this  table  ore  the  weights  which  must 
be  assigned  to  the  atom  of  aluminium,  according  to  the  several  modes  of 
constitution  indicated  in  the  first  column ;  but  there  is  nothing  in  the  con- 


*  "looj,  equal ;  /*op^,  form, 


228 


ATOMIC   WEIGHTS. 


Btitution  of  the  oxide  itself  that  can  enable  us  to  decide  between  them. 
Now,  iron  forms  two  oxides,  in  which  the  quantities  of  oxygen  united  with 
the  same  quantity  of  iron  are  to  one  another  as  1  :  1J,  or  as  2  :  3.  These 
are  therefore  regarded  as  monoxide,  FeO,  and  sesquioxide,  Fe203,  and  this 
last  oxide  is  known  to  be  isomorphous  with  alumina.  Consequently  alumina 
is  also  regarded  as  a  sesquioxide,  A1203,  and  the  atomic  weight  of  aluminium 
is  inferred  to  be  27-4. 

..  3.  To  the  Volume-Relations  of  Elements  and  Compounds. — The  atomic  weights 
of  those  elements  which  are  known  to  exist  in  the  state  of  gas  or  vapor  are, 
with  one  or  two  exceptions,  proportional  to  their  specific  gravities  in  the 
same  state.  Taking  the  specific  gravity  of  hydrogen  as  unity,  those  of  the 
following  gases  and  vapors  are  expressed  by  numbers  identical  with  their 
atomic  weights: 

Oxygen     . 
Sulphur 
Selenium 
Tellurium     . 


Hydrogen 
Chlorine 
Bromine 
Iodine 


1 
35.5 


127 


16 
32 

79 
128 


The  exceptions  to  this  rule  are  exhibited  by  phosphorus  and  arsenic,  whose 
vapor-densities  are  twice  as  great  as  their  atomic  weights,  that  of  phos- 
phorus being  62,  and  that  of  arsenic  150;  and  by  mercury  and  cadmium, 
whose  vapor-densities  are  the  halves  of  their  atomic  weights,  that  of  mer- 
cury being  100,  and  that  of  cadmium  56. 

LAWS  OF  COMBINATION  BY  VOLUME. — From  the  preceding  relations,  it 
follows  that  the  volumes  of  any  two  elementary  gases  which  make  up  a 
compound  molecule,  are  to  one  another  in  the  same  ratio  as  the  numbers  of 
atoms  of  the  same  elements  which  enter  into  the  compound,  excepting  in 
the  case  of  phosphorus  and  arsenic,  for  which  the  number  of  volumes  thus 
determined  has  to  be  halved,  and  of  mercury  and  cadmium,  for  which  it 
must  be  doubled  ;  thus : 

The  molecule  HC1      contains         1  vol.  H  and  1  vol.  Cl. 

H20 
"  H3N 

H3P 

"  Cl3As 

"  Cl2Hg" 

If  the  smallest  volume  of  a  gaseous  element  that  can  enter  into  combi- 
nation be  called  the  combining  volume  of  that  element,  the  law  of  combi- 
nation may  be  expressed  as  follows :  The  combining  volumes  of  all  elementary 
gases  are  equal,  excepting  those  of  phosphorus  and  arsenic,  which  are  only  half 
those  of  the  other  elements  in  the  gaseous  state,  a?id  those  of  mercury  and  cadmium, 
which  are  double  those  of  the  other  elements. 

It  appears,  then,  that  in  all  cases  the  volumes  in  which  gaseous  elements 
combine  together  may  be  expressed  by  very  simple  numbers.  This  is  the 
"Law  of  Volumes,"  first  observed  by  Humboldt  and  Gay-Lussac  in  1805, 
with  regard  to  the  combination  of  oxygen  and  hydrogen,  and  afterwards 
established  in  other  cases  by  Gay-Lussac,  whose  observations,  published  in 
his  "Theory  of  Volumes,"  afforded  new  and  independent  evidence  of  the 
combination  of  bodies  in  definite  and  multiple  proportions,  in  corroboration 
of  that  derived  from  the  previously  observed  proportions  of  combination 
by  weight. 

Gay-Lussac  likewise  observed  that  the  product  of  the  union  of  two  gases, 


2 

H 

1 

0. 

3 

H 

1 

N. 

{       3 
tor6 

H 
H 

1 

P. 
P. 

/       3 
tor  6 

Cl 
Cl 

I 

As. 
As. 

2 

'     Cl 

2 

'   Hg. 

ATOMIC    THEORY.  229 

when  itself  a  gas,  sometimes  retains  the  original  volume  of  its  constituents, 
no  contraction  or  change  of  volume  resulting  from  the  combination,  but 
that  when  contraction  takes  place,  which  is  the  most  common  case,  the 
volume  of  the  compound  gas  always  bears  a  simple  ratio  to  the  volumes  of 
its  elements;  and  subsequent  observation,  extended  over  a  very  large  num- 
ber of  compounds,  organic  as  well  as  inorganic,  has  shown  that,  with  a  few 
exceptions,  probably  only  apparent,  the  molecules  of  compound  bodies  in  the 
gaseous  state  occupy  twice  the  volume  of  an  atom  of  hydrogen  gas.  No  matter 
what  may  be  the  number  of  atoms  or  volumes  that  enter  into  the  compound, 
they  all  become  condensed  into  two  volumes,  thus: 

1  vol.  H  and  1  vol.  Cl  form  2  vol.  HC1.  hydrochloric  acid. 

1  "    N     "    1     "    0      "     2    "    NO,  nitrogen  dioxide. 

2  <<    H    "    1     "    0      "     2    "    H20,  water. 

3  "    H    "    1     "    N      "     2    "    H3N,  ammonia. 

3    «    H    «    i    »<    p      «     2    "    H3P,  hydrogen  phosphide. 

Similarly  in  the  union  of  compound  gases,  e.  g. 

1  vol.  ethyl,  C2H6,  and  1  vol.  Cl,  form  2  vol.  C|H6C1,       ethyl 

chloride. 

2  «    ethyl,  C2H5,     «    1    «    0        "2    «    (C2H6)20,     ethyl 

oxide. 
2    " ethene,  C2H4,     "    2    "    Cl      "    2    "    C2H4C12,    ethene 

chloride. 

2    " ethene,  C2H4,     "    1    '<    0       "2    "   C2H40,      ethene 

oxide. 

Hence  it  follows  that  the  specific  gravity  of  any  compound  gas  or  vapor,  re- 
ferred to  hydrogen  as  unity,  is  equal  to  half  its  atomic  or  molecular  weight. 

The  quotient  obtained  by  dividing  the  molecular  weight  of  a  body  by  its 
specific  gravity  is  called  its  Specific  or  Atomic  volume;  hence  the  law  just 
stated  may  also  be  thus  expressed:  The  specific  volumes  of  compound  gases  or 
vapors  referred  to  that  of  hydrogen  as  unity  are,  with  a  few  exceptions,  equal  to  2. 
We  shall  presently  show  that  the  same  law  applies  to  the  specific  volumes 
of  the  elementary  gases  themselves. 

For  many  years  past,  attemj 
the  results  of  Gay-Lussac's  discovery  of  the  law  of  gaseous  combination  by 
volume,  the  specific  volumes  of  the  bodies  in  question  being  determined  by 
tlie  method  pursued  in  the  case  of  gases  —  namely,  by  dividing  the  mole- 
cular weight  by  the  specific  gravity.  The  numbers  obtained  in  this  manner, 
representing  the  specific  volumes  of  the  various  solid  and  liquid  elementary 
substances,  present  far  more  cases  of  discrepancy  than  of  agreement.  The 
latter  are,  however,  sufficiently  numerous  to  excite  great  interest  in  the  in- 
vestigation. Some  of  the  results  pointed  out  are  exceedingly  curious  as 
far  as  they  go,  but  are  not  as  yet  sufficient  to  justify  any  general  conclusion. 
The  inquiry  is  beset  with  many  great  difficulties,  chiefly  arising  from  the 
unequal  expansion  of  solids  and  liquids  by  heat,  and  the  great  differences 
of  physical  state,  and,  consequently,  of  specific  gravity,  often  presented  by 
the  former. 

THE  ATOMIC  THEORY. 

The  laws  of  chemical  combination,  and  the  relations  between  atomic  and 
equivalent  weights  above  explained,  are  the  result  of  pure  experimental  in- 
quiry, and  independent  of  all  hypothesis.  In  this,  however,  as  in  other 
branches  of  science,  the  comprehension  of  experimental  results  may  be 
greatly  facilitated  by  endeavoring  to  refer  them  to  a  general  law  or  mode 
of  action.  That  no  attempt  should  be  made  to  explain  the  manner  iu  which 
20 


230  ATOMIC    THEORY. 

chemical  compounds  are  formed,  and  to  point  out  the  nature  of  the  relations 
between  the  different  modifications  of  matter  which  determine  chemical 
changes,  would,  indeed,  be  contrary  to  the  speculative  tendency  of  the 
human  mind.  Such  an  attempt  — and  a  very  ingenious  and  successful  one 
it  i8 has,  in  fact,  been  made,  namely,  the  atomic  hypothesis  of  Dr.  Dalton. 

From  very  ancient  times,  the  question  of  the  constitution  of  matter  with 
respect  to  divisibility  has  been  debated,  some  adopting  the  opinion  that  this 
divisibility  is  infinite,  and  others,  that  when  the  particles  become  reduced 
to  a  certain  degree  of  tenuity,  far,  indeed,  beyond  any  state  that  can  be 
reached  by  mechanical  means,  they  cease  to  be  further  diminished  in  magni- 
tude; they  become,  in  short,  atoms*  Now,  however  the  imagination  may 
succeed  in  figuring  to  itself  the  condition  of  matter  on  either  view,  it  is 
hardly  necessary  to  mention  that  we  have  absolutely  no  means  at  our  dis- 
posal for  deciding  such  a  question,  which  remains  at  the  present  day  in  the 
same  state  as  when  it  first  engaged  the  attention  of  the  Greek  philosophers, 
or  perhaps  that  of  the  sages  of  Egypt  and  Hindostan  long  before  them. 

Dalton's  hypothesis  sets  out  by  assuming  the  existence  of  such  atoms  or 
indivisible  particles,  and  states,  that  compounds  are  formed  by  the  union  of 
atoms  of  different  bodies,  one  to  one,  one  to  two,  &c.  The  compound  atom, 
or  molecule,  joins  itself  in  the  same  manner  to  a  compound  atom  of  another 
kind,  and  a  combination  of  the  second  order  results.  Let  it  be  granted, 
further,  that  the  atoms  of  different  elements  have  different  weights,  fixed 
and  invariable  for  each,  and  the  hypothesis  becomes  capable  of  rendering 
consistent  and  satisfactory  reasons  for  all  the  observed  numerical  laws  of 
chemical  combination. 

Chemical  compounds  must  always  be  definite:  they  must  always  contain 
the  same  number  of  atoms  of  the  same  kind  arranged  in  a  similar  manner. 
The  same  kind  and  number  of  atoms  need  not,  however,  of  necessity  pro- 
duce the  same  substance,  for  they  may  be  differently  arranged;  and  much 
depends  upon  this  circumstance. 

Again,  the  law  of  multiple  proportions  is  perfectly  well  explained.  One 
atom  of  carbon  unites  with  one  atom  of  oxygen  to  form  carbon  monoxide, 
and  with  two  atoms  to  form  carbon  dioxide ;  one  atom  of  sulphur  with  two 
and  three  atoms  of  oxygen  to  form  the  dioxide  and  trioxide  of  sulphur; 
one  atom  of  phosphorus  with  three  and  five  atoms  of  chlorine  to  form  the 
trichloride  and  pentachloride  of  phosphorus;  two  atoms  of  nitrogen  with 
one,  two,  three,  four  and  five  atoms  of  oxygen  to  form  the  five  oxides  already 
mentioned  (pp.  157,  220). 

The  atomic  hypothesis  likewise  affords  an  easy  explanation  of  the  manner 
in  which  bodies  replace  or  may  be  substituted  one  for  the  other.  Here, 
however,  we  come  upon  an  extension  of  the  original  Daltonian  hypothesis. 
It  was  formerly  supposed  that  when  one  element  replaced  another  in  com- 
bination, the  substitution  always  took  place  atom  for  atom ;  and  accordingly 
the  terms  "atoms"  and  "equivalent"  were  regarded  as  synonymous,  at 
least  so  far  as  numerical  value  was  concerned.  But,  according  to  the 
atomic  weights  now  adopted,  and  determined  by  the  considerations  above 
explained,  we  must  suppose  that  one  atom  of  an  element  may  take  the  place 
of  two,  three,  four  atoms,  &c.,  of  another.  It  is  only,  in  fact,  the  atoms 
of  monogenic  elements  that  can  replace  each  other  one  by  one:  an  atom 
of  a  polygenic  element,  on  the  other  hand,  always  takes  the  place  of,  or  is 
equivalent  to,  two  or  more  atoms  of  a  monogenic  element. 

This  difference  of  equivalent  or  saturating  power  is  often  denoted  by 
placing  dashes  or  Roman  numerals  to  the  right  of  the  symbol  of  an  ele- 
ment, and  at  the  top,  as  0",  B///,  CiT,  &c. ;  and  the  several  elements  are 
designated  aa 


'A.TOJIOJ,  that  which  cannot  be  cut. 


ATOMIC    THEORY. 


231 


Univalent  elements,  or   Monads,  as  H 


Bivalent 

Trivalent 

Quadrivalent 

Quinquivalent 

Sexvalent 


Dyads 

Triads 

Tetrads 

Pentads 

Hexads 


0" 
B/// 

ClT 
P 
W" 


Elements  of  even  equivalency,  viz.,  the  dyads,  tetrads,  and  hexads,  are 
also  included  under  the  general  term  artiads,*  and  those  of  uneven  equiva- 
lency, viz.,  the  monads,  triads,  and  pentads,  are  designated  generally  as 
perissads.  -f 

Another  method  of  indicating  the  equivalent  values  of  the  elementary 
atoms,  and  the  manner  in  which  they  are  satisfied  by  combination,  is  to 
arrange  the  symbols  in  diagrams  in  which  each  element  is  connected  with 
others  by  a  number  of  lines,  or  connecting  bonds,  corresponding  to  its 
degree  of  equivalence ;  J  a  monad  being  connected  with  other  elements  by 
only  one  such  bond,  a  triad  by  three,  a  hexad  by  six,  &c.,  as  in  the  follow- 
ing examples:  — 

Water,  OH2 

Carbon  dioxide,  C02 


Ammonium  chloride,  NH^Cl 


Sulphuric  oxide,  S03. 


Sulphuric  acid,  S04H2 


Nitric  acid,  N03H 


Zinc  nitrate,  N206Zn 


S=0 

II 
0 

0 

II 

H— 0— S— 0— H 

II 
0 

o 

II 

N— 0— H 
II 
0 
0  0 

II  II 

N— 0— Zn— 0— N 


ii 

0  0 

It  must  be  distinctly  understood  that  these  formulae  — which  may  be  called 
constitutional  formulx  —  are  not  intended  to  represent  the  actual  arrangement 

*  "Apriof,  even.  t  ntpiwAf,  uneven. 

1  The  symbols  of  the  elements  in  these  diagrams  are  often  enclosed  in  circles  to  represent  the 
atoms,  with  rays  diverpn-  from  them  to  indicate  the  number  of  connecting  bonds;  such  tor- 
mula-  are  called  graphic  formula' ;  but  the  circles  do  not  add  anything  to  the  clearness  ..1  t 
representation,  and  may  as  well  be  omitted.  For  lecture  and  class  illustration,  solid  diagram* 
are  constructed,  with  wooden  halls  of  various  colors,  to  represent  the  atoms,  having  hole*  ft* 
the  insertion  of  connecting  rods;  these  representations  are  called  glyptic  formula. 


232  ATOMIC   THEORY. 

of  the  atoms  in  a  compound  ;  indeed,  even  if  we  had  a  distinct  notion  of 
the  manner  in  which  the  atoms  of  any  compound  are  arranged,  it  could  not 
be  adequately  represented  on  a  plane  surface.  The  lines  connecting  the 
different  atoms  indicate  nothing  more  than  the  number  of  units  of  equiva- 
lency belonging  to  the  several  atoms,  and  the  manner  in  which  they  are 
disposed  of  by  combination  with  those  of  other  atoms.  Thus  the  formula 
for  nitric  acid  indicates  that  two  of  the  three  constituent  oxygen-atoms  are 
combined  with  the  nitrogen  alone,  and  are  consequently  attached  to  that 
element  by  both  their  units  of  equivalency,  whereas  the  third  oxygen-atom 
is  combined  both  with  nitrogen  and  with  hydrogen. 

By  inspection  of  the  preceding  diagrams,  it  will  be  observed  that  every 
atom  of  a  compound  has  each  of  its  units  of  equivalency  satisfied  by  com- 
bination with  a  unit  belonging  to  some  other  atom.  Such,  indeed,  is  the 
case  in  every  saturated  or  normal  compound.  Accordingly,  it  is  found  that  in 
all  such  compounds  the  sum  of  the  perissad  elements  is  always  an  even  num- 
ber. Thus  a  compound  may  contain  two,  four,  six,  &c.,  monad  atoms,  as 
HC1,  OH2,  CH4,  C2H6,  C3H8,  SiH3Cl  ;  or  one  monad  and  one  triad  atom,  as 
BC13;  or  one  pentad  and  tive  monads,  as  NH4C1;  but  never  an  uneven  num- 
ber of  perissad  atoms.  This  is  the  "law  of  even  numbers"  announced 
some  years  ago  by  Gerhardt  and  Laurent  as  a  result  of  observation.  It 
was  long  received  with  doubt,  but  has  now  been  confirmed  by  the  analysis 
of  so  many  well-defined  compounds,  that  a  departure  from  it  is  looked  upon 
as  a  sure  indication  of  incorrect  analysis. 

For  a  similar  reason,  the  atoms  of  elementary  bodies  rarely  exist  in  the 
free  state,  but,  when  separated  from  any  compound,  tend  to  combine  with 
other  atoms,  either  of  the  same  or  of  some  other  element.  Perissad  ele- 
ments, like  hydrogen,  chlorine,  nitrogen,  &c.,  separate  from  their  compounds 
in  pairs;  their  molecule  contains  two  atoms,  e.g.  H  —  H.  Artiad  elements 
may  unite  in  groups  of  two,  three,  or  more  ;  thus  the  molecule  of  oxygen, 
in  its  ordinary  state,  probably,  contains  two  atoms,  that  of  ozone  three 
atoms;  thus: 

Oxygen          ........    0=0 

Ozone        ........        0  —  0 


0 

The  tendency  of  elementary  atoms  to  separate  in  groups  is  shown  in 
various  ways.  Thus  when  copper  hydride,  Cu2H2  (to  be  hereafter  de- 
scribed), is  decomposed  by  hydrochloric  acid,  a  quantity  of  hydrogen  is 
given  off  equal  to  twice  that  which  is  contained  in  the  hydride  itself;  thus: 

Cu2H2  -f  2HC1  =  Cu2Cl2  +  2HH. 

This  action  is  precisely  analogous  to  that  of  hydrochloric  acid  on  cuprous 
oxide  : 

Cu20  -f  2HC1  =  Cu2Cl2  +  OH2. 

In  the  latter  case,  the  hydrogen  separated  from  the  hydrochloric  acid 
unites  with  oxygen,  in  the  former  with  hydrogen.  Again,  when  solutions 
of  sulphurous  acid  and  sulph-hydric  acid  are  mixed,  the  whole  of  the  sul- 
phur is  precipitated: 

S03H2  -f  2SH2  =  30H2  -f  S.S2 

the  action  being  similar  to  that  of  sulphurous  acid  on  selenhydric  acid: 
S03H2  -f  2SeH2  ==  30H2  -f  S.Se2. 

In  the  one  case,  a  sulphide  of  selenium  is  precipitated;  in  the  other,  a 
sulphide  of  sulphur.  The  precipitation  of  iodine,  which  takes  place  on 


ATOMIC    THEORY.  233 

mixing  hydriodic  acid  with  iodic  acid,  affords  a  similar  instance  of  the 
combination  of  homogeneous  atoms: 

5IH  +      I03H      =  30H2  =        311 

Hydriodic  acid.     Iodic  acid.     Water.      Free  iodine. 

Another  striking  illustration  of  this  mode  of  action  is  afforded  by  the  re- 
duction of  certain  metallic  oxides  by  hydrogen  dioxide.  When  silver  oxide 
is  thrown  into  this  liquid,  water  is  formed;  the  silver  is  reduced  to  the 
metallic  state,  and  a  quantity  of  oxygen  is  evolved  equal  to  twice  that  which 
is  contained  in  the  silver  oxide: 

OAg2     +       02H2       =      OH2     +      Ag2     4-       00 
Silver         Hydrogen         Water.         Silver.         Oxygea. 
oxide.  dioxide. 

Further,  elementary  bodies  frequently  act  upon  others  as  if  their  atoms 
were  associated  in  binary  groups.  Thus,  chlorine  acting  upon  potash 
forms  two  compounds,  the  chloride  and  hypochlorite  of  potassium  (p.  185) : 

C1C1  4-  OKK  =  C1K  4.  OC1K. 

Again,  in  the  action  of  chlorine  upon  many  organic  compounds,  one  atom 
of  chlorine  removes  one  atom  of  hydrogen  as  hydrochloric  acid,  while  an- 
other atom  of  chlorine  takes  the  place  of  the  hydrogen  thus  removed.  For 
example,  in  the  formation  of  chloracetic  acid  by  the  action  of  chorine  on 
acetic  acid: 

C2H402  4-  C1C1  =  HC1  4-  C2H,C10, 
Acetic  acid.  Chloracetic  acid. 

Similarly,  when  metallic  sulphides  oxidize  in  the  air,  both  the  metal  and 
the  sulphur  combine  with  oxygen;  and  sulphur  acting  upon  potash  forms 
both  a  sulphide  and  a  hyposulphite.  In  all  these  cases  the  atoms  of  the 
elementary  bodies  act  in  pairs. 

On  the  supposition  that  the  molecules  of  elementary  bodies  in  the  gaseous 
state  are  made  up  of  two  atoms,  the  specific  volumes  of  these  gases  will 
come  under  the  same  law  as  that  which  applies  to  compounds  (p.  229) ;  and 
it  may  then  be  stated  generally,  that,  with  the  few  exceptions  already  no- 
ticed, the  specific  gravities  of  all  bodies,  simple  and  compound,  in  the  gaseous 
state,  are  equal  to  half  their  molecular  weights ;  or  the  specific  volume  (the  quo- 
tients of  the  molecular  weight  by  the  specific  gravities)  are  equal  to  2. 

Variation  of  Equivalency. — Multivalent  or  polygenic  elements  often  ex- 
hibit varying  degrees  of  equivalency.  Thus  carbon,  which  is  quadrivalent 
in  marsh  gas,  CH4,  and  in  carbon  dioxide,  C02,  is  only  bivalent  in  carbon 
monoxide,  CO ;  nitrogen,  which  is  quinquivalent  in  sal-ammoniac,  NH4C1, 
and  the  other  ammonium  salts,  and  in  nitrogen  pentoxide,  N206,  is  trivalent 
in  ammonia,  NH3,  and  in  nitrogen  trioxide,  N203,  and  univalent  in  nitrogen 
monoxide,  N20  ;  sulphur,  also,  which  is  sexvalent  in  sulphur  trioxide,  S03, 
is  quadrivalent  in  sulphur  dioxide,  S02,  and  bivalent  in  hydrogen  sulphide, 
SH<2,  and  in  many  metallic  sulphides.  In  these  cases,  and  in  all  others  of 
varying  equivalency,  the  variation  always  takes  place  by  two  units  of 
equivalency.  It  is  not  very  easy  to  account  for  these  variations ;  but  it  is 
observed  in  all  cases  that  the  compounds  in  which  the  equivalency  of  a  po- 
lygenic element  is  most  completely  satisfied  are  more  stable  than  the  others, 
and  that  the  latter  tend  to  pass  into  the  former  by  taking  up  the  required 
number  of  univalent  or  bivalent  atoms;  thus,  carbon  monoxide,  CO,  o;isily 
takes  up  another  atom  of  oxygen  to  form  the  dioxide,  C02 :  nitrogen  tri- 
oxide, N2O3,  is  readily  converted  into  the  pentoxide,  N206;  ammonia,  NIT3, 
unites  readily  with  hydrochloric  acid  to  form  sal-ammoniac,  NH4C1,  £c. 
20* 


234  ATOMIC    THEORY. 

Similar  phenomena  are  exhibited  by  many  organo-metallic  bodies,  as  will 
be  explained  further  on. 

From  this  it  seems  most  probable  that  the  true  equivalency  or  atomicity 
of  a  polygeriic  element  is  that  which  corresponds  with  the  maximum  num- 
ber of  monad  atoms  with  which  it  can  combine,  but  that  one  or  two  pairs 
of  its  units  of  equivalency  may,  under  certain  circumstances,  remain  un- 
saturated.  Whether  a  saturated  or  an  unsaturated  element  is  formed,  will 
depend  on  a  variety  of  conditions,  often  in  great  measure  on  the  relative 
quantities  of  the  acting  substances.  Thus,  phosphorus,  which  is  a  pentad 
element,  forms  with  chlorine,  either  a  trichloride,  PC13,  or  a  pentachloride, 
PC16,  according  as  the  phosphorus  or  the  chlorine  is  in  excess  (p.  217).* 

In  compounds  containing  two  or  more  atoms  of  the  same  polygenic 
element,  one  or  more  units  of  equivalence  belonging  to  each  of  these  atoms 
may  be  neutralized  by  combination  with  those  of  another  atom  of  the  same 
kind,  so  that  the  element  in  question  will  appear  to  enter  into  the  compound 
with  less  than  its  normal  degree  of  equivalence.  Thus,  in  ethane,  or  di- 
methyl, C2H6,  which  is  a  perfectly  stable  compound,  having  no  tendency  to 
take  up  an  additional  number  of  atoms  of  hydrogen  or  any  other  element, 
the  carbon  appears  to  be  trivalent  instead  of  quadrivalent ;  similarly  in 
propane,  C3H8,  its  equivalence  appears  to  be  reduced  to  f ;  and  in  quartane 
or  diethyl,  C4H,0,  to  f.  In  all  these  cases,  however,  the  diminution  of 
equivalent  value  in  the  carbon  atoms  is  only  apparent,  as  may  be  seen  from 
the  following  formulae : 

Ethane. 
H 


H—C—H 
H— C— H 

i 


or,  more  shortly,  omitting  the  equivalent  marks  of  the  monad  atoms : 

Ethane.  Propane.  Quartane. 

CH3  CH3  CH3 

CH3  CH2  CH2 

CH3  OH2 

CH3. 

In  each  of  these  compounds,  every  carbon  atom,  except  the  two  outside 
ones,  has  two  of  its  units  of  equivalence  satisfied  by  combination  with  those 
of  the  neighboring  carbon  atoms,  while  each  of  the  two  exterior  ones  has 
only  one  unit  thus  satisfied.  Hence  in  any  similarly  constituted  compound 
containing  n  carbon  atoms,  the  number  of  units  of  equivalence  remaining 
to  be  satisfied  by  the  hydrogen  atoms  is  4n  —  2(n  —  2)  —  2  =  2n  -}-  2. 
The  general  formula  of  this  series  of  hydrocarbons  is,  therefore,  CnH2n+2, 
and  the  equivalent  value  of  the  carbon  is  ^n~\~^. 

n 

*  See  also  Erlemneyer,  "  Lehrbuch  der  organischen  Chemie."    Leipzig  und  Heidelberg, 


ATOMIC   THEORY.  235 

In  other  cases,  multivalent  atoms  may  be  united  by  two  or  more  of  their 
units  of  equivalence,  so  that  their  combining  power  may  appear  to  be  still 
further  reduced,  as  in  the  hydrocarbon,  C2H4,  in  which  the  carbon  may  be 
apparently  bivalent,  and  in  C2H2,  in  which  it  may  appear  to  be  univaleut  ; 
thus: 

H        —  C—  II  C—  H 

H—  C—  H  (j—  H. 

In  all  cases,  the  equivalent  value  or  atomicity  of  an  element  must  be  de- 
termined by  the  number  of  monad  atoms  with  which  it  can  combine.  Of 
dyad  atoms,  indeed,  any  element  or  compound  may  take  up  an  indefinite 
number,  without  alteration  of  its  equivalence  or  combining  powers  ;  for 
each  dyad  atom,  possessing  two  units  of  equivalency,  neutralizes  one  unit 
in  the  compound  which  it  enters,  and  introduces  another,  leaving,  therefore, 
the  equivalence  or  combining  power  of  the  compound  just  what  it  was  be- 
fore. Thus  potassium  forms  only  one  chloride,  KC1,  and  is,  therefore,  uni- 
valent  or  monadic;  but  in  addition  to  the  oxide,  K20,  corresponding  to 
this  chloride,  it  likewise  forms  two  others,  viz.,  K203  and  K204,  in  the  former 
of  which  it  might  be  regarded  as  dyadic,  and  in  the  latter  as  tetradic  ;  but 
the  manner  in  which  dyad  oxygen  enters  these  compounds  is  easily  seen 
by  inspection  of  the  following  diagrams: 

Monoxide  Dioxide  Tetroxide 

0—  K  0—  K 


O-K  A 

J 


O- 


It  is  evident  that  any  number  of  oxygen-atoms  might,  in  like  manner,  be 
inserted  without  disturbing  the  balance  of  equivalency.  If,  indeed,  we 
turn  to  the  sulphides  of  potassium,  in  which  the  sulphur  is  dyadic,  like 
oxygen,  we  find  the  series,  K2Sj,  K2S2,  K2S3,  K2S4,  K2S5,  the  constitution  of 
which  may  be  represented  in  a  precisely  similar  manner.  Hence  the  equi- 
valence of  any  element  must  be  determined  by  the  composition  of  its  chlo- 
rides, bromides,  iodides,  or  fluorides,  not  by  that  of  its  oxides  or  sulphides. 

Assuming  then  that  the  maximum  equivalence  of  a  polygenic  element  is 
that  which  represents  its  normal  mode  of  combination,  the  element  ary 
bodies  may  be  classified  as  in  the  following  table,  in  which  the  names  of 
the  metalloids  are  printed  in  italics,  those  of  the  metals  in  Roman  type,  and 
the  elements  are  further  divided  by  horizontal  lines  into  groups  consisting 
of  elements  closely  related  in  their  chemical  characters:  in  each  of  these 
groups  the  elements  are  arranged  in  the  order  of  their  atomic  weights,  be- 
ginning with  the  lowest.  (See  Table,  p.  226.) 

The  position  of  several  of  the  elements  in  this  arrangement  must  be  re- 
garded as  still  somewhat  doubtful.  Nitrogen,  phosphorus,  arsenic,  antnnn»>/, 
and  bismuth,  though  quinquivalent  in  a  considerable  number  of  compounds, 
as  ammonium-chloride,  NH4C1,  phosphorus  pentachloride,  PC16,  etc.,  never- 
theless form  very  stable  compounds,  as  NH3.  AsCl3,  As203,  etc.,  in  which 
they  are  trivalent.  It  is  true  that  these  compounds  pass  with  tolerable 
facility  into  others  in  which  the  nitrogen,  phosphorus,  etc.,  are  quinqui- 
valent, and  these  latter  show  no  disposition  to  attach  to  themselves  .-my 
additional  number  of  monad  atoms;  but,  on  the  other  hand,  these 


236 


ATOMIC  THEORY. 


compounds  do  not  appear  to  be  very  stable,  inasmuch  as  they  easily  split 
up,  when  volatilized,  in  such  a  manner  as  to  yield  compounds  of  the  triadic 


Monads. 

Dyads. 

Triads. 

Tetrads. 

Pentads. 

Hexads. 

Hydrogen 

Oxygen 

Boron 

Carbon 
Silicon 
Titanium 
Tin 

Nitrogen 
Phosphorus 
Vanadium 
Arsenic 
Antimony 
Bismuth 

Sulphur 
Selenium 
Tellurium 

Fluorine 
Chlorine 
Bromine 
Iodine 

Calcium 
Strontium 
Barium 

Gold 

Thallium 

Chromium 
Molyb- 
denum 
Tungsten 

Aluminium 
Zirconium 

Berylium 
Yttrium 
Lanthanum 
Didymium 
Erbium 
Thorinum 

Lithium 
Sodium 
Potassium 
Rubidium 
Caesium 

Niobium 
Tantalum 

Rhodium 
Ruthenium 
Palladium 
Platinum 
Iridium 
Osmium 

Silver 

Magnesium 
Zinc 
Cadmium 

Lead 

Copper 
Mercurv 

Manganese 
Iron 
Cobalt 
Nickel 
Cerium 
Indium 
Uranium 

class;    sal-ammoniac,  for  example,  into  hydrochloric  acid  and  ammonia, 
phosphorus  pentachloride  into  free  chlorine  and  the  trichloride : 


NH4C1 
PC15 


HC1 

CL 


NH3 
PCI,. 


Iron,  and  the  metals  which  follow  it  in  the  table,  are  sometimes  classed 
as  hexads,  on  account  of  their  analogy  with  chromium,  which  is,  undoubtedly, 
hexadic,  inasmuch  as  it  forms  a  hexnuoride,  CrF6.  Neither  of  these  metals, 
however,  is  known  to  form  any  well-defined  compounds  in  which  it  is  more 
than  quadrivalent,  Iron,  for  example,  is  bivalent  in  the  ferrous  salts,  as 
Fe^do,  arid  quadrivalent  in  the  ferric  compounds,  ferric  chloride,  Fe2Cl6, 

FeCl3 
being  constituted  in  the  manner  shown  by  the  formula  I        .     Manganese 

FeCl3 

is  inferred  to  be  a  hexad,  on  account  of  the  isomorphism  and  similarity  of 
composition  between  the  magnates  and  the  chromates  :  but  the  isomorphism 
of  two  elements,  or  their  corresponding  compounds,  does  not  afford  decided 
proof  of  equal  equivalency,  for  the  fluoniobates  are  known  to  be  isomor- 
phous  with  the  fluosilicates  and  fluotitanates ;  and  yet  niobium  is  a  pentad 
element,  whereas  silicium  and  titanium  are  tetrads. 

Sulphur,  selenium,  and  tellurium,  are  usually  regarded  as  dyads,  on  account 
of  the  close  analogy  of  their  compounds  to  those  of  oxygen,  and  especially 
of  their  hydrogen  compounds,  SH2,  &c.,  to  water.  But  selenium  and  tel- 
lurium form  well-defined  tetrachlorides ;  and  even  sulphur  tetrachloride, 


ATOMIC    THEORY.  237 

SCI/,,  though  it  has  not  been  obtained  in  the  free  state,  is  known  in  combi- 
nation with  metallic  chlorides.  Sulphur  has  also  lately  been  shown  to  form 
certain  organic  compounds  in  which  it  is  tetradic,  and  others  in  which  it 
appears  to  be  hexadic.*  Moreover,  the  chemical  relations  of  the  sulphates 
are  much  more  clearly  represented  by  formulae,  in  which  sulphur  is  sup- 
posed to  be  hexadic  (like  that  given  for  sulphuric  acid  on  page  231),  than 
by  formulae  into  which  it  enters  as  a  dyad;  and  similar  remarks  apply  to 
the  selenates  and  tellurates;  for  these  reasons,  sulphur,  selenium,  and 
tellurium,  are  most  conveniently  regarded  as  hexads,  though  they  sometimes 
enter  into  combination  as  tetrads,  and  very  frequently  as  dyads. 

Compound  Radicals.  —  Suppose  one  or  more  of  the  component  atoms  of  a 
fully  saturated  molecule  to  be  removed:  it  is  clear  that  the  remaining  atom 
or  group  of  atoms  will  no  longer  be  saturated,  but  will  have  a  combining 
power  corresponding  to  the  number  of  units  of  equivalency  removed.  Such 
unsaturated  groups  are  called  residues  or  radicals.  Methane,  CH4,  is  a  fully 
saturated  compound;  but  if  one  of  its  hydrogen  atoms  be  removed,  the 
residue  CH3  (called  methyl},  will  be  ready  to  combine  with  one  atom  of  a 
univalent  element,  such  as  chlorine,  bromine,  &c.,  forming  the  compounds 
CH3C1,  CH3Br,  &c. ;  two  atoms  of  it  unite  in  like  manner  with  one  atom  of 
oxygen,  sulphur,  and  other  bivalent  elements,  forming  the  compounds 
0//(CH3)2,  S"(CH0)2,  &c. ;  three  atoms  with  nitrogen  yielding  N//(CH3)3,  &c. 

The  removal  of  two  hydrogen-atoms  from  CH4  leaves  the  bivalent  radical 
CH2,  called  methene.  which  yields  the  compounds  CH2C12,  CH20,  CH2S,  &c. 
The  removal  of  three  hydrogen  atoms  from  CH4  leaves  the  trivalent  rsuil-al 
CH,  which,  in  combination  with  three  chlorine-atoms,  constitutes  chloro- 
form, CHC13.  And,  finally,  the  removal  of  all  four  hydrogen-atoms  from 
CH4  leaves  the  quadrivalent  radical  carbon  CiT,  capable  of  forming  the  com- 
pounds CC14,  CS2,  &c. 

In  like  manner,  ammonia,  NH3,  in  which  the  nitrogen  is  trivalent,  yields, 
by  removal  of  one  hydrogen-atom,  the  univalent  radical  amidogen  NH2, 
which  with  one  atom  of  potassium  forms  potassamine,  NH2K,  and  when 
combined  with  one  atom  of  the  univalent  radical  methyl,  CH3,  forms  methy- 
lamine,  NH2(CH3),  &c.  The  abstraction  of  two  hydrogen-atoms  from  the 
molecule  NH3,  leaves  the  bivalent  radical  imidogen,  NH,  which  with  two 
methyl-atoms  forms  dimethylamine,  NH(CH3)2,  &c. ;  and  the  removal  of  all 
three  hydrogen-atoms  from  NH3,  leaves  nitrogen  itself,  which  frequently 
acts  as  a  trivalent  element  or  radical,  forming  tripotassamine  NK3,  trime- 
thylamine  N(CII3)3,  &c. 

Finally,  the  molecule  of  water,  OH2,  by  losing  an  atom  of  hydrogen,  is 
converted  into  the  univalent  radical  hydroxyl,  OH,  which,  in  its  relations  to 
other  bodies,  is  analogous  to  chlorine,  bromine,  and  iodine,  and  may  be 
substituted  in  combination  for  one  atom  of  hydrogen  or  other  monads. 
Thus,  water  itself  may  be  regarded  as  H.HO,  analogous  to  hydrochloric 
acid  HC1;  potassium  hydrate  as  K.HO,  analogous  to  potassium  chloride; 
barium  hydrate,  as  Ba//.(OH)2,  analogous  to  barium  chloride  Ba"Cl2. 

In  a  similar  manner,  the  univalent  radical,  potassoxyl,  KO,  may  be  derived 
from  potassium  hydrate ;  the  bivalent  radical,  zincoxyl,  Zn02,  by  abstraction 
of  H2  from  zinc  hydrate,  Zn^HjO^  The  essential  character  of  .these  oxy- 
genated radicals  is  that  each  of  the  oxygen  atoms  contained  in  them  is 
united  to  the  other  atoms  by  one  unit  of  equivalency  only,  so  that  the 
radical  has  necessarily  one  or  two  units  unconnected ;  thus : 

Hydroxyl H~~°~~ 

PotassoxyF 

Zincoxyl 0 — Zn — 0 — 

*  Sulphur  triethiodide,  S«*  (Coirf,)3I 
Sulphur  diethene-dibromide,  S*» 


238  ATOMIC    THEORY. 

From  the  preceding  explanations  of  the  mode  of  derivation  of  compound 
radicals,  it  is  clear  that  there  is  no  limit  to  the  number  of  them  which  may 
be  supposed  to  exist ;  in  fact,  it  is  only  necessary  to  suppose  a  number  of 
units  of  equivalency  abstracted  from  any  saturated  molecule,  in  order  to 
obtain  a  radical  of  corresponding  combining  power  or  equivalent  value. 
But  unless  a  radical  can  be  supposed  to  enter  into  a  considerable  number 
of  compounds,  thus  forming  them  into  a  group  like  the  salts  of  the  same 
metal,  there  is  nothing  gained  in  point  of  simplicity  or  comprehensiveness 
by  assuming  its  existence. 

It  must,  also,  be  distinctly  understood  that  these  compound  radicals  do 
not  necessarily  exist  in  the  separate  state,  and  that  those  of  uneven  equi- 
valency, like  methyl,  cannot  exist  in  that  state,  their  molecules,  if  liberated 
from  combination  with  others,  always  doubling  themselves,  as  we  have  seen 
to  be  the  case  with  most  of  the  elementary  bodies.  Thus  hydroxyl  — 0 — H 
is  not  known  in  the  free  state,  the  actually  existing  compound  containing 
the  same  proportions  of  hydrogen  and  oxygen,  being  02H2  or  H — 0 — 0 — H. 
In  like  manner,  methyl,  CH3,  has  no  separate  existence,  but  dimethyl 
C2H6  is  a  known  compound : 

Methyl.  Dimethyl. 

H  H 

H— C— H  H— C— H 

-H 


H— C— 1 

A 


CHEMICAL  AFFINITY. 

rTlHE  term  chemical  affinity,  or  chemical  attraction,  has  been  invented  to 
.[_  describe  that  particular  power  or  force,  in  virtue  of  which,  union,  often 
of  a  very  intimate  and  permanent  nature,  takes  place  between  two  or  more 
bodies,  in  such  a  way  as  to  give  rise  to  a  new  substance,  having,  for  the 
most  part,  properties  completely  in  discordance  with  those  of  its  components. 

The  attraction  thus  exerted  between  different  kinds  of  matter  is  to  be 
distinguished  from  other  modifications  of  attractive  force  which  are  exerted 
indiscriminately  between  all  descriptions  of  substances,  sometimes  at  enor- 
mous distances,  sometimes  at  intervals  quite  inappreciable.  Examples  of 
the  latter  are  to  be  seen  in  cases  of  what  is  called  cohesion,  when  the  par- 
ticles of  solid  bodies  are  immovably  bound  together  into  a  mass.  Then,  there 
are  other  effects  of,  if  possible,  a  still  more  obscure  kind ;  such  as  the  various 
actions  of  surface,  the  adhesion  of  certain  liquids  to  glass,  the  repulsion 
of  others,  the  ascent  of  water  in  narrow  tubes,  and  a  multitude  of  curious 
phenomena  which  are  described  in  works  on  Natural  Philosophy,  under  the 
head  of  molecular  actions.  From  all  these,  true  chemical  attraction  may  be 
at  once  distinguished  by  the  deep  and  complete  change  of  characters  which 
follows  its  exertion:  we  might  define  affinity  to  be  a  force  by  which  new 
substances  are  generated. 

It  seems  to  be  a  general  law  that  bodies  most  opposed  to  each  other  in 
chemical  properties  evince  the  greatest  tendency  to  enter  into  combination ; 
and,  conversely,  bodies  between  which  strong  analogies  and  resemblances 
can  be  traced  manifest  a  much  smaller  amount  of  mutual  attraction.  For 
example,  hydrogen  and  the  metals  tend  very  strongly  indeed  to  combine 
with  oxygen,  chlorine,  and  iodine,  but  the  attraction  between  the  different 
members  of  these  two  groups  is  incomparably  more  feeble.  Sulphur  and 
phosphorus  stand,  as  it  were,  midway :  they  combine  with  substances  of 
one  and  the  other  class,  their  properties  separating  them  sufficiently  from 
both.  Acids  are  drawn  towards  alkalies,  and  alkalies  towards  acids,  while 
union  among  themselves  rarely  if  ever  takes  place. 

Nevertheless,  chemical  combination  graduates  so  imperceptibly  into  mere 
mechanical  mixture,  that  it  is  often  impossible  to  mark  the  limit.  Solution 
•is  the  result  of  a  weak  kind  of  affinity  existing  between  the  substance  dis- 
solved and  the  solvent  —  an  affinity  so  feeble  as  completely  to  lose  one  of 
its  most  prominent  features  when  in  a  more  exalted  condition  —  namely, 
power  of  causing  elevation  of  temperature ;  for  in  the  act  of  mere  solution, 
the  temperature  falls,  the  heat  of  combination  being  lost  and  overpowered 
by  the  effects  of  change  of  state. 

The  force  of  chemical  attraction  thus  varies  greatly  with  the  nature  of 
the  substances  between  which  it  is  exerted ;  it  is  influenced,  moreover,  to  a 
very  large  extent,  by  external  or  adventitious  circumstances.  An  idea 
formerly  prevailed  that  the  relations  of  affinity  were  fixed  and  constant 
between  the  same  substances,  and  great  pains  were  taken  in  the  prepara- 
tion of  tables  exhibiting  what  was  called  the  precedence  of  affinities, 
order  pointed  out  in  these  lists  is  now  acknowledged  to  represent  the  order 
of  precedence  for  the  circumstances  under  which  the  experiments  were  made, 
but  nothing  more;  so  soon  as  these  circumstances  become  changed,  the 
order  is  disturbed.  The  ultimate  effect,  indeed,  is  not  the  result  of  the  ex- 
ercise of  one  single  force,  but  rather  the  joint  effect  of  a  number,  so  com- 
plicated and  so  variable  in  intensity,  that  it  is  but  seldom  possible  to  pre- 
dict the  consequences  of  any  yet  untried  experiment. 

It  will  be  proper  to  examine  shortly  some  of  these  extraneous  causes  to 

239 


240  CHEMICAL   AFFINITY. 

which  allusion  has  been  made,  which  modify  to  so  great  an  extent  the  direct 
and  original  effects  of  the  specific  attractive  force. 

Alteration  of  temperature  may  be  reckoned  among  these.  When  metallic 
mercury  is  heated  nearly  to  its  boiling-point,  and  in  that  state  exposed  for 
a  lengthened  period  to  the  air,  it  absorbs  oxygen,  and  becomes  converted 
into  a  dark-red  crystalline  powder.  This  very  same  substance,  when  raised 
to  a  still  higher  temperature,  separates  spontaneously  into  metallic  mercury 
and  oxygen  gas.  It  may  be  said,  and  probably  with  truth,  that  the  latter 
change  is  greatly  aided  by  the  tendency  of  the  metal  to  assume  the  vaporous 
state ;  but  precisely  the  same  fact  is  observed  with  another  metal,  palladium, 
which  is  not  volatile,  excepting  at  extremely  high  temperatures,  but  which 
oxidizes  superficially  at  a  red  heat,  and  again  becomes  reduced  when  the 
temperature  rises  to  whiteness. 

Insolubility  and  the  power  of  vaporization  are  perhaps,  beyond  all  other 
disturbing  causes,  the  most  potent;  they  interfere  in  almost  every  reaction 
which  takes  place,  and  very  frequently  turn  the  scale  when  the  opposed  forces 
do  not  greatly  differ  in  energy.  It  is  easy  to  give  examples.  When  a  solu- 
tion of  calcium  chloride  is  mixed  with  a  solution  of  ammonium  carbonate, 
double  interchange  ensues,  calcium  carbonate  and  ammonium  chloride  being 
generated:— CaCl2  -\-  C03  (NH4)2  =  C03Ca  -|-  2NH4C1.  Here  the  action 
can  be  shown  to  be  in  a  great  measure  determined  by  the  insolubility  of 
the  calcium  carbonate.  Again,  when  dry  calcium  carbonate  is  powdered  and 
mixed  with  ammonium  chloride,  and  the  whole  heated  in  a  retort,  a  subli- 
mate of  ammonium  carbonate  is  formed,  while  calcium  chloride  remains 
behind.  In  this  instance,  it  is  no  doubt  the  great  volatility  of  the  new  am- 
moniacal  salt  which  chiefly  determines  the  kind  of  decomposition. 

When  iron  filings  are  heated  to  redness  in  a  porcelain  tube,  and  vapor  of 
water  passed  over  them,  the  water  undergoes  decomposition  with  the  utmost 
facility,  hydrogen  being  rapidly  disengaged,  and  the  iron  converted  into 
oxide.  On  the  other  hand,  oxide  of  iron,  heated  in  a  tube  through  which 
a  stream  of  dry  hydrogen  is  passed,  suffers  almost  instantaneous  reduction 
to  the  metallic  state,  while  the  vapor  of  water,  carried  forward  by  the 
current  of  gas,  escapes  as  a  jet  of  steam  from  the  extremity  of  the  tube. 
In  these  experiments  the  affinities  between  the  iron  and  oxygen  and  the 
hydrogen  and  oxygen  are  so  nearly  balanced,  that  the  difference  of  atmos- 
phere is  sufficient  to  settle  the  point.  An  atmosphere  of  steam  offers  little 
resistance  to  the  escape  of  hydrogen;  an  atmosphere  of  hydrogen  bears 
the  same  relation  to  steam ;  and  this  apparently  trifling  difference  of  circum- 
stances is  quite  enough  for  the  purpose. 

The  decomposition  of  vapor  of  water  by  white-hot  platinum,  pointed  out 
by  Mr.  Grove,  will  probably  be  referred  in  great  part,  to  this  influence  of 
atmosphere,  the  steam  offering  great  facilities  for  the  assumption  of  the 
elastic  condition  by  the  oxygen  and  hydrogen.  The  decomposition  ceases 
as  soon  as  these  gases  amount  to  about  J-^-Q-Q  of  the  bulk  of  the  mixture,  and 
can  only  be  renewed  by  their  withdrawal.  The  attraction  of  oxygen  for 
hydrogen  is  probably  much  weakened  by  the  very  high  temperature.  The 
recombination  of  the  gases  by  the  heated  metal  is  rendered  impossible  by 
their  state  of  dilution. 

What  is  called  the  nascent  state  is  one  very  favorable  to  chemical  com- 
bination. Thus,  nitrogen  refuses  to  combine  with  gaseous  hydrogen ;  yet 
when  these  substances  are  simultaneously  liberated  from  some  previous 
combination,  they  unite  with  great  ease,  as  when  organic  matters  are  de- 
stroyed by  heat,  or  by  spontaneous  putrefactive  change. 

There  is  a  remarkable,  and,  at  the  same  time,  very  extensive  class  of 
actions,  grouped  together  under  the  general  title  of  cases  of  disposing  af- 
finity. Metallic  silver  does  not  oxidize  at  any  temperature:  nay,  more, 
its  oxide  is  easily  decomposed  by  simple  heat;  yet  if  the  finely  divided 
metal  be  mixed  with  siliceous  matter  and  alkali,  and  ignited,  the  whole. 


CHEMICAL    AFFINITY.  241 

fuses  to  a  yellow  transparent  glass  of  silver  silicate.  Platinum  is  attacked 
by  fused  potassium  hydrate,  hydrogen  being  probably  disengaged  while 
the  metal  is  oxidized:  this  is  an  effect  which  never  happens  to  silver  under 
the  same  circumstances,  although  silver  is  a  much  more  oxidable  substance 
than  platinum.  The  fact  is,  that  potash  forms  with  the  oxide  of  the  last- 
named  metal  a  kind  of  saline  compound,  in  which  the  platinum  oxide  acts 
as  an  acid ;  and  hence  its  formation  under  the  disposing  influence  of  the 
powerful  base.  , 

In  the  remarkable  decompositions  suffered  by  various  organic  bodies 
when  heated  in  contact  with  caustic  alkali  or  lime,  we  have  other  examples 
of  the  same  fact.  Products  are  generated  which  are  never  formed  in  the 
absence  of  the  base ;  the  reaction  is  invariably  less  complicated,  and  its 
results  few  in  number  and  more  definite,  than  in  the  event  of  simple  de- 
struction by  a  graduated  heat. 

,  There  is  yet  a  still  more  obscure  class  of  phenomena,  called  catalj/sis,  in 
which  effects  are  brought  about  by  the  mere  presence  of  a  substance  which 
itself  undergoes  no  perceptible  change:  the  experiment  mentioned  in  the 
chapter  on  oxygen,  in  which  that  gas  is  obtained,  with  the  greatest  facility, 
by  heating  a  mixture  of  potassium  chlorate  and  manganese  dioxide,  is  an 
excellent  case  in  point.  The  salt  is  decomposed  at  a  very  far  lower  tem- 
perature than  would  otherwise  be  required,  and  yet  the  manganese  oxide 
does  not  appear  to  undergo  any  alteration,  being  found  after  the  experi- 
ment in  the  same  state  as  before.  It  may,  however,  undergo  a  temporary 
alteration.  We  know,  indeed,  that  this  oxide  is  capable  of  taking  up  an 
additional  proportion  of  oxygen  and  forming  manganic  acid;  and  it  is 
quite  possible  that  in  the  reaction  just  considered  it  may  actually  take 
oxygen  from  the  potassium  chlorate,  and  pass  to  the  state  of  a  higher 
oxide,  which,  however,  is  immediately  decomposed,  the  additional  oxygen 
being  evolved,  and  the  manganese-oxide  returning  to  its  original  state. 
The  same  effect  in  facilitating  the  decomposition  of  the  chlorate  is  produced 
by  cupric  oxide,  ferric  oxide,  and  lead  oxide,  all  of  which  are  known  to 
be  susceptible  of  higher  oxidation.  The  oxides  of  zinc  and  magnesium, 
on  the  contrary,  which  do  not  form  higher  oxides,  are  not  found  to  facili- 
tate the  decomposition  of  the  chlorate  ;  neither  is  any  such  effect  produced 
by  mixing  the  salt  with  other  pulverulent  substances,  such  as  pounded 
glass  or  pure  silica. 

The  so-called  catalytic  actions  are  often  mixed  up  with  other  effects 
which  are  much  more  intelligible,  as  the  action  of  finely  divided  platinum 
on  certain  gaseous  mixtures,  in  which  the  solid  appears  to  condense  the 
gas  upon  its  greatly  extended  surface,  and  thereby  to  induce  combination 
by  bringing  the  particles  within  the  sphere  of  their  mutual  attractions. 

Relations  of  Heal  to  Chemical  Affinity.  — Whatever  may  be  the  real  nature 
of  chemical  affinity,  one  most  important  fact  is  clearly  established  with 
regard  to  it;  namely,  that  its  manifestations  are  always  accompanied  by 
the  production  or  annihilation  of  heat.  Change  of  composition,  or  chem- 
ical action,  and  heat  are  mutually  convertible:  a  given  amount  of  chemical 
action  will  give  rise  to  a  certain  definite  amount  of  heat,  which  quantity 
of  heat  must  be  directly  or  indirectly  expended,  in  order  to  reverse  or 
undo  the  chemical  action  that  has  produced  it.  The  production  of  heat  by 
chemical  action,  and  the  definite  quantitative  relation  between  the  amount 
of  heat  evolved  and  the  quantity  of  chemical  action  which  takes  place,  are 
roughly  indicated  by  the  facts  of  our  most  familiar  experience ;  thus,  for 
instance,  the  only  practically  important  method  of  producing  heat  arti- 
ficially consists  in  changing  the  elements  of  wood  and  coal,  together  with 
atmospheric  oxygen,  into  carbon  dioxide  and  water;  and  every  one  knows 
that  the  heat  which  can  be  thus  obtained  from  a  given  quantity  of  coal  is 
limited,  and  is,  at  least  approximately,  always  the  same. 


242 


CHEMICAL    AFFINITY. 


The  accurate  measurement  of  the  quantity  of  heat  produced  by  a  given 
amount  of  chemical  action  is  a  problem  of  very  great  difficulty;  chiefly 
because  chemical  changes  very  seldom  take  place  alone,  but  are  almost 
always  accompanied  by  physical  changes  involving  further  calorimetric 
eifects,  each  of  which  requires  to  be  accurately  measured  and  allowed  for, 
before  the  effect  due  to  the  chemical  action  can  be  rightly  estimated.  Thus 
the  ultimate  result  has,  in  most  cases,  to  be  deduced  from  a  great  number 
of  independent  measurements,  each  of  which  is  liable  to  a  certain  amount 
of  error.  It  is  therefore  not  surprising  that  the  results  of  various  experi- 
ments should  differ  to  a  comparatively  great  extent,  and  that  some  uncer- 
tainty should  still  exist  as  to  the  exact  quantity  of  heat  corresponding  to 
even  the  simplest  cases  of  chemical  action. 

The  experiments  are  made  by  enclosing  the  acting  substances  in  a  vessel 
called  a  calorimeter,  surrounded  by  water  or  mercury,  the  rise  of  tempera- 
ture in  which  indicates  the  quantity  of  heat  evolved  by  the  chemical  action, 
after  the  necessary  corrections  have  been  made  for  the  heat  absorbed  by  the 
containing  vessel  and  the  other  parts  of  the  apparatus,  and  for  the  amount 
lost  by  radiation,  &c.  Combustions  in  oxygen  and  chlorine  are  made  in  a 
copper  vessel  surrounded  by  water ;  the  heat  evolved  by  the  mutual  action  of 
liquids  or  dissolved  substances  is  estimated  by  means  of  a  smaller  calorimeter 
containing  mercury.  The  construction  of  these  instruments  and  the  methods 
of  observation  involve  details  which  are  beyond  the  limits  of  this  work.* 

The  following  table  gives  the  quantities  of  heat,  expressed  in  heat-units,-}- 
evolved  in  the  combustion  of  various  elements,  and  a  few  compounds,  in 
oxygen,  referred:  (1)  to  1  gram  of  each  substance  burned;  (2)  to  1  gram 
of  oxygen  consumed ;  (3)  to  one  atom  or  molecule  (expressed  in  grams)  of 
the  various  substances :  — 

Heat  of  Combustion  of  Elementary  Substances  in  Oxygen. 


Substance. 

Product. 

Units  of  heat  evolved 

Observer. 

by  1  grm.  of 
substance. 

by  1  gram 
of  oxygen. 

by  1  at.  of 

substance. 

Hydrogen    .     .     . 

OH2 

/  33881 
\  34462 

4235 
4308 

53881 
64462 

Andrews. 
Favre  &  Silbermann. 

Carbon  : 

Wood-charcoal 

C02 

/7900 

\8080 

2962 
3030 

94800 
96960 

Andrews. 
Favre  &  Silbermann. 

Gas  retort  carbon 

it 

8047 

3018 

96564 

« 

Native  graphite 

« 

7797 

2924 

93564 

« 

Artificial  graphite 

t« 

7762 

2911 

93144 

« 

Diamond    .     .     . 

«. 

7770 

2914 

93940 

« 

Sulphur: 

Native  .... 

S02 

2220 

2220 

71040 

« 

Recently  melted  . 

« 

2260 

2260 

72320 

(i 

Flowers      .     .     . 

« 

2307 

2307 

73821 

Andrews. 

Phosphorus  : 

(Yellow)    .     .     . 

PA 

5747 

4454 

178157 

« 

Zinc         .... 

ZnO 

1330 

5390 

86450 

« 

Iron  

Fe,0, 

1582 

4153 

88592 

« 

Tin     

34 

Sn0.2 

1147 

4230 

135360 

« 

Copper    .... 

CuO 

603 

2394 

38304 

« 

*  See  filler's  Chemical  Physics,  pp.  338,  ft  sea.,  and  Watts's  Dictionary  of  Chemistry,  iii. 
28, 103. 

f  The  unit  of  heat  here  adopted,  is  the  quantity  of  heat  required  to  raise  1  gram,  of  water 
from  0°  to  1°  C. 


CHEMICAL    AFFINITY. 


243 


The  following  results  have  been  obtained  by  the  complete  combustion  of 
partially  oxidized  substances : 


Substance. 

Product. 

Units  of  heat  evolved 

Observer. 

by  1  grm. 
of  sub- 
stance. 

in  formation  of 
1  molecule  of  the 
ultimate  product. 

Carbon  monoxide,  CO 

Stannous  oxide,  SnO 
Cuprous  oxide,  Cu20 

C02 

Sn02 
CuO 

/2403 
\2431 
519 

256, 

67284 
68054 
69584 
18304 

Favre  &  Silbermann. 
Andrews. 

n 

The  last  three  substances  in  this  table  contain  exactly  half  as  much 
oxygen  as  the  completely  oxidized  products  ;  and  on  comparing  the  amount 
of  heat  evolved  in  the  formation  of  one  molecule  of  stannic  or  cupric  oxide 
from  the  corresponding  lower  oxide,  with  the  quantity  produced  when  a 
molecule  of  the  same  product  is  formed  by  the  complete  oxidation  of  the 
metal  in  one  operation,  we  find  that  the  combination  of  the  second  half  of 
the  oxygen  contained  in  these  bodies  evolves  sensibly  half  as  much  as  the 
combination  of  the  whole  quantity.  In  the  formation  of  carbon  dioxide, 
however,  the  second  half  of  the  oxygen  appears  to  develop  more  than  two 
thirds  of  the  total  amount  of  heat;  but  this  result  is  probably  due,  in  part 
at  least,  to  the  fact  that  when  carbon  is  burned  into  carbon  dioxide,  a  con- 
siderable but  unknown  quantity  of  heat  is  expended  in  converting  the  solid 
carbon  into  gas,  and  thus  escape  measurement ;  while,  in  carbon  monoxide, 
the  carbon  already  exists  in  the  gaseous  form,  and  therefore  no  portion  of 
the  heat  evolved  in  the  combustion  of  this  substance  is  similarly  expended 
in  producing  a  change  of  state. 

It  seems  probable,  also,  that  a  similar  explanation  may  be  given  of  the 
inequalities  in  the  quantities  of  heat  produced  by  the  combustion  of  differ- 
ent varieties  of  pure  carbon  and  of  sulphur  —  that  is  to  say,  that  a  portion 
of  the  heat  generated  by  the  combustion  of  diamond  and  graphite  goes  to 
assimilate  their  molecular  condition  to  that  of  wood-charcoal,  and  that  there 
is  an  analogous  expenditure  of  heat  in  the  combustion  of  native  sulphur. 

Combustions  in  Chlorine,  and  Direct  Combination  of  Chlorine,  Bromine,  and 
'Iodine  ivith  other  Elements.  —  The  folio  wing  table  gives  the  quantities  of  heat 
evolved  by  the  direct  union  of  various  elements  with  gaseous  chlorine : 


Units  of  heat  evolved 

Substance. 

Product. 

by  1  gram 

by  1  grm. 

by  1  at.  (-  35-5 

Observer. 

of  sub- 

of 

grams)  of 

stance. 

chlorine. 

chlorine. 

c  24087 

678 

24087 

Abria. 

Hydrogen    . 

HC1 

1  23783 

670 

23783 

(  Favre  & 
\  Silbermann. 

Phosphorus 
Potassium    . 

PC16  (?) 
KC1 

3422  (?) 
2655 

607 
2943 

21548 
104476 

Andrews. 

Iron    .     .     . 
Zinc    .     .     . 

Fe2Cl6 
ZnCl2 

1745 
1529 

921 
1427 

82696 

50058 

Tin      ... 

SnCl4 

1079 

897 

31722 

Arsenic    . 

AsCls 

994 

704 

24992 

Copper     .     . 
Antimony 
Mercury 

CuCl2 
SbCl3 

9(51 
707 

9 

859 
860 
822 

30494 
30491 
29181 

• 

CHEMICAL  AFFINITY. 


The  heat  evolved  by  the  direct  union  of  bromine  and  iodine  with  zinc 
and  iron  has  also  been  determined  by  Andrews :  the  results  obtained  are 
given  in  the  next  table  : 


Metal. 

Product. 

Units  of  heat  evolved 

by  1  gram 
of  metal. 

by  1  gram  of 
bromine  or 
iodine. 

by  1  atom  of  bromine 
or  iodine. 

Bromine. 


Zinc 
Iron 

ZnBr2 
Fe.2Br6 

1269 
1277 

508 
298 

40640 

23833 

Iodine. 


Zinc 
Iron            .         . 

ZnI2 
FeJ6 

819 
463 

209 
63 

26617 
8046 

Reactions  in  Presence  of  Water.  —  The  thermal  effects  which  may  result 
from  the  reaction  of  different  substances  on  one  another  in  presence  of 
water,  are  more  complicated  than  those  resulting  from  direct  combination. 
In  addition  to  the  different  specific  heats  of  the  reagents  and  products,  and 
to  the  different  quantities  of  heat  absorbed  by  them  in  dissolving,  or  given 
out  by  them  in  combining  with  water,  the  conversion  of  soluble  substances 
into  insoluble  ones,  as  a  consequence  of  the  cluemical  action,  or  the  inverse 
change  of  insoluble  into  soluble  bodies,  are  among  the  secondary  causes  to 
which  part  of  tho  calorimetric  effect  may  be  due  in  these  cases. 

When  a  gas  dissolves  in  water,  the  heat  due  to  the  chemical  action  is 
augmented  by  that  due  to  the  liquefaction  of  the  gas ;  so  also  when  a  solid 
body  is  dissolved  in  water,  the  total  thermal  effect  is  due  in  part  to  the 
chemical  action  taking  place  between  the  water  and  the  solid,  and  in  part 
to  the  liquefaction  of  the  substance  dissolved.  In  the  former  cases  the 
chemical  and  physical  parts  of  the  phenomenon  both  cause  evolution  of  heat ; 
in  the  latter  case  the  physical  change  occasions  disappearance  of  heat,  arid 
if  this  effect  is  greater  than  that  due  to  the  chemical  action,  the  ultimate 
effect  is  the  production  of  cold,  and  it  is  this  which  is  generally  observed. 

Cold  produced  by  Chemical  Decomposition.  —  It  is  highly  probable  that  the 
thermal  effect  of  the  reversal  of  a  given  chemical  action  is  in  all  cases  equal 
and  opposite  to  the  thermal  effect  of  that  action  itself.  A  direct  conse- 
quence of  this  proposition  is  that  the  separation  of  any  two  bodies  is  attended 
with  the  absorption  of  a  quantity  of  heat  equal  to  that  which  is  evolved  in  their 
combination.  The  truth  of  this  deduction  has  been  experimentally  estab- 
lished in  various  cases,  by  Wood,*  Joule,f  and  Favre  and  Silbermann,  by  com- 
paring the  heat  evolved  in  the  electrolysis  of  dilute  sulphuric  acid,  or  solu- 
tions of  metallic  salts,  with  that  which  is  developed  in  a  thin  metallic  wire 
by  a  current  of  the  same  strength ;  also  by  comparison  of  the  heat  evolved 
in  processes  of  combination  accompanied  by  simultaneous  decomposition, 
•with  that  evolved  when  the  same  combination  occurs  between  free  elements. 

By  determining  the  heat  evolved  when  different  metals  were  dissolved  in 
water  or  dilute  acid,  Wood  found  that  it  was  less  than  that  which  would  be 
produced  by  the  direct  oxidation  of  the  same  metals,  by  a  quantity  equal 
to  that  which  would  be  obtained  by  burning  the  hydrogen  set  free,  or 
which  was  expended  in  decomposing  the  water  or  acid:  and,  therefore, 
that  when  this  latter  quantity  was  added  to  the  results,  they  agreed  with 
the  numbers  given  by  experiments  of  direct  oxidation. 

*  Phil.  Mag.  [4]  ii.  368 ;  iv.  370.  *  Ibid.  iii.  481. 


CHEMISTBY    OF    THE    VOLTAIC    PILE.  245 


ELECTRO-CHEMICAL  DECOMPOSITION;  CHEMISTRY  OF  THE  VOLTAIC 

PILE. 

WHEN  a  voltaic  current  of  considerable  power  is  made  to  traverse  various 
compound  liquids,  a  separation  of  the  elements  of  these  liquids  ensues ; 
provided  that  the  liquid  be  capable  of  conducting  the  current,  its  decom- 
position almost  always  follows. 

The  elements  are  disengaged  solely  at  the  limiting  surfaces  of  the  liquid, 
where,  according  to  the  common  mode  of  speech,  the  current  enters  and 
leaves  the  latter,  all  the  intermediate  portions  appearing  perfectly  quies- 
cent. In  addition,  the  elements  are  not  separated  indifferently  and  at 
random  at  these  two  surfaces;  but,  on  the  contrary,  make  their  appear- 
ance with  perfect  uniformity  and  constancy  at  one  or  the  other,  according 
to  their  chemical  character — namely,  oxygen,  chlorine,  iodine,  acids,  &c., 
at  the  surface  connected  with  the  copper,  or  positive  end  of  the  battery ; 
hydrogen,  the  metals,  &c.,  at  the  surface  in  connection  with  the  zinc  or 
negative  extremity  of  the  arrangement. 

The  terminations  of  the  battery  itself — usually,  but  by  no  means  neces- 
sarily, of  metal  —  are  designated  poles  or  electrodes,*  as  by  their  interven- 
tion the  liquid  to  be  experimented  on  is  made  a  part  of  the  circuit.  The 
process  of  decomposition  by  the  current  is  called  cle.ctrolysis.-\  and  the 
liquids,  which,  when  thus  treated,  yield  up  their  elements,  are  denomi- 
nated electrolytes. 

When  a  pair  of  platinum  plates  are  plunged  into  a  glass  of  water  to 
which  a  few  drops  of  oil  of  vitriol  have  been  added,  and  the  plates  con- 
nected by  wires  with  the  extremities  of  an  active  battery,  oxygen  is  disen- 
gaged at  the  positive  electrode,  and  hydrogen  at  the  negative,  in  the  pro- 
portion of  one  measure  of  the  former  to  two  of  the  latter  nearly.  This 
experiment  has  before  been  described.  J 

A  solution  of  hydrochloric  acid  mixed  with  a  little  Saxon  blue  (indigo), 
and  treated  in  the  same  manner,  yields  hydrogen  on  the  negative  side  and 
chlorine  on  the  positive,  the  indigo  there  becoming  bleached. 

Potassium  iodide  dissolved  in  water  is  decomposed  in  a  similar  manner: 
the  free  iodine  at  the  positive  side  can  be  recognized  by  its  brown  color, 
or  by  the  addition  of  a  little  gelatinous  starch. 

All  liquids  are  not  electrolytes;  many  refuse  to  conduct,  and  no  decom- 
position can  then  occur ;  alcohol,  ether,  numerous  essential  oils,  and  other 
products  of  organic  chemistry,  besides  a  few  saline  inorganic  compounds, 
act  in  this  manner,  and  completely  arrest  the  current  of  a  powerful  battery. 

One  of  the  most  important  and  indispensable  conditions  of  electrolysis  is 
fluidity :  bodies  which,  when  reduced  to  the  liquid  state,  conduct  freely, 
and  as  freely  suffer  decomposition,  become  absolute  insulators  to  the  elec- 
tricity of  the  battery  when  they  become  solid.  Lead  chloride  offers  a 
good  illustration  of  this  fact:  when  fused  in  a  porcelain  crucible,  it  gives 
up  its  elements  with  the  utmost  ease,  and  a  galvanometer,  interposed 
somewhere  in  the  circuit,  is  strongly  affected.  But  when  the  source  of 
heat  is  withdrawn,  and  the  salt  suffered  to  solidify,  signs  of  decomposition 
cease,  and  at  the  same  moment  the  magnetic  needle  reassumes  its  natural 
position.  In  the  same  manner,  the  thinnest  film  of  ice  arrests  the  current 

*  From  ¥,\tKT9ov,  and  Md(,  a  way.  t  From  frttrpov,  and  Mtiv,  to  loose. 

%  Pago  143. 

21  * 


246  ELECTRO-CHEMICAL 

of  a  powerful  voltaic  apparatus ;  but  the  instant  the  ice  is  liquefied  at  any 
one  point,  so  that  water  communication  is  restored  between  the  electrodes, 
the  current  again  passes,  and  decomposition  occurs.  Fusion  by  heat,  and 
solution  in  aqueous  liquids,  answer  the  purpose  equally  well. 

Generally  speaking,  compound  liquids  cannot  conduct  the  electric  cur- 
rent without  being  decomposed;  but  still  there  are  a  few  exceptions  to 
this  statement,  which  perhaps  are  more  apparent  than  real.  Thus  Hittorf 
has  shown,  that  fused  silver  sulphide,  which  was  formerly  regarded  as  one 
of  the  exceptions,  cannot  be  considered  to  be  so,  and  Bectz  has  since  proved 
the  same  to  be  the  case  as  regards  mercuric  iodide  and  lead  fluoride. 

The  quantity  of  any  given  compound  liquid  which  can  be  decomposed 
by  any  given  electric  battery  depends  on  the  resistance  of  the  liquid:  the 
more  resistance  the  less  decomposition.  Distilled  water  has  only  a  small 
power  of  conduction,  and  is  therefore  only  slightly  decomposed  by  a  bat- 
tery of  30  to  40  pairs ;  whilst  diluted  sulphuric  acid  is  one  of  the  best  of 
fluid  conductors,  and  undergoes  rapid  decomposition  by  a  small  battery. 

When  a  liquid  which  can  be  decomposed,  and  a  galvanometer,  are  in- 
cluded in  the  circuit  of  an  electric  current,  if  the  needle  of  the  galvano- 
meter be  deflected,  it  may  be  always  assumed  as  certain  that  a  portion  of 
liquid,  bearing  a  proportion  to  the  strength  of  the  current,  is  decomposed, 
although  it  may  be  impossible  in  many  cases,  without  special  contrivances, 
to  detect  the  products  of  the  decomposition,  on  account  of  their  minute- 
ness. 

The  metallic  terminations  of  the  battery,  the  poles  or  electrodes,  have, 
in  themselves,  nothing  in  the  shape  of  attractive  or  repulsive  power  for 
the  elements  separated  at  their  surfaces.  Finely  divided  metal  suspended 
in  water,  or  chlorine  held  in  solution  in  that  liquid,  shows  not  the  least 
symptom  of  a  tendency  to  accumulate  around  them ;  a  single  element  is 
altogether  unaifected  —  directly,  at  least;  separation  from  previous  combi- 
nation is  required,  in  order  that  this  appearance  should  be  exhibited. 

It  is  necessary  to  examine  the  process  of  electrolysis  a  little  more 
closely.  When  a  portion  of  hydrochloric  acid,  for  example,  is  subjected 
to  decomposition  in  a  glass  vessel  with  parallel  sides,  chlorine  is  disen- 
gaged at  the  positive  electrode,  and  hydrogen  at  the  negative :  the  gases 
are  perfectly  pure  and  unmixed.  If,  while  the  decomposition  is  rapidly 
proceeding,  the  intervening  liquid  be  examined  by  a  beam  of  light,  or  by 
other  means,  not  the  slightest  disturbance  or  movement  of  any  kind  will 
be  perceived ;  nothing  like  currents  in  the  liquid  or  bodily  transfer  of  gas 
from  one  part  to  another  can  be  detected  ;  and  yet  two  portions  of  hydro- 
chloric acid,  separated  perhaps  by  an  interval  of  four  or  five  inches,  may 
be  respectively  evolving  pure  chlorine  and  pure  hydrogen. 

There  is,  it  would  seem,  but  one  mode  of  explaining  this  and  all  similar 
cases  of  regular  electrolitic  decomposition:  this  is  by  assuming  that  all 
the  particles  of  hydrochloric  acid  between  the  electrodes,  and  by  which 
the  current  is  conveyed,  simultaneously  suffer  decomposition,  the  hydrogen 
travelling  in  one  direction,  and  the  chlorine  in  the  other.  The  neighboring 
elements,  thus  brought  into  close  proximity,  unite  and  reproduce  hydro- 
chloric acid,  again  destined  to  be  decomposed  by  a  repetition  of  the  same 
change.  In  this  manner,  each  particle  of  hydrogen  may  be  made  to  travel 
in  one  direction,  by  becoming  successively  united  to  each  particle  of  chlo- 
rine between  itself  and  the  negative  electrode ;  when  it  reaches  the  latter, 
finding  no  disengaged  particle  of  chlorine  for  its  reception,  it  is  rejected, 
as  it  were,  from  the  series,  and  thrown  off  in  a  separate  state.  The  same 
thing  happens  to  each  particle  of  chlorine,  which  at  the  same  time  passes 
continually  in  the  opposite  direction,  by  combining  successively  with  each 
particle  of  hydrogen  that  moment  separated,  with  which  it  meets,  until  at 
length  it  arrives  at  the  positive  plate  or  wire,  and  is  disengaged.  A  sue- 


CHEMISTRY    OF    THE    VOLTAIC    PILE.  247 

cession  of  particles  of  hydrogen  are  thus  continually  thrown  off  from  the 
decomposing  mass  at  one  extremity,  and  a  corresponding  succession  of 
particles  of  chlorine  at  the  other.  The  power  of  the  current  is  exerted 
with  equal  energy  in  every  part  of  the  liquid  conductor,  though  its  effect* 
become  manifest  only  at  the  very  extremities.  The  action  is  one  of  a 
purely  molecular  or  internal  nature,  and  the  metallic  terminations  of  the 
battery  merely  serve  the  purpose  of  completing  the  connection  between 
the  latter  and  the  liquid  to  be  decomposed.  The  figures  141  and  142  are 


©©©M®©® 


*)©©!©©©© 


Hydrochloric  acid  in  its  usual  state. 

intended  to  assist  the  imagination  of  the  reader,  who  must  at  the  same 
time  avoid  regarding  them  in  any  other  light  than  that  of  a  somewhat 
figurative  mode  of  representing  the  curious  phenomena  described.  The 
circles  are  intended  to  indicate  the  elements,  and  are  distinguished  by 
their  respective  symbols. 

Like  hydrochloric  acid,  all  electrolytes,  when  acted  on  by  electricity,  are 
split  into  two  constituents,  which  pass  in   opposite  directions.     The  one 

Fig.  142. 


Hydrochloric  acid  undergoing  electrolysis. 

class  of  substances,  like  oxygen,  chlorine,  &c.,  are  evolved  at  the  positive 
electrode ;  the  other  class,  like  hydrogen  and  the  metals,  at  the  negative 
electrode. 

'  It  is  of  importance  to  remark  that  oxygen  salts,  such  as  sulphates  and 
nitrates,  when  acted  on  by  the  current,  do  not  divide  into  acid  and  basic 
oxide,  but,  as  Daniell  and  Miller  proved,  into  metal  and  a  compound  sub- 
stance, or  group  of  elements,  which  is  transferred  in  such  a  state  of  asso- 
ciation that,  as  regards  its  electrical  behavior,  it  represents  an  element. 
Thus,  cupric  sulphate,  S04Cu,  splits,  not  into  S03  and  CuO,  but  into  me- 
tallic copper  and  sulphiom  S04.  Hydrogen  sulphate,  or  sulphuric  acid, 
S04H2,  divides  into  the  same  compound  group  and  hydrogen.  In  a  similar 
way,  also,  the  part  of  the  electrolyte  which  passes  to  the  negative  pole  may 
consist  of  a  group  of  element^.  A  solution  of  sal-ammoniac,  NH4C1,  fur- 
nishes a  beautiful  instance  of  this  fact,  since  it  is  decomposed  by  the  cur- 
rent in  such  a  manner  that  the  ammonium  NH4  goes  to  the  negative,  and 
the  chlorine  to  the  positive  pole. 

A  distinction  must  be  carefully  drawn  between  true  and  regular  e 
trolysis,  and  what  is  called  secondary  decomposition,  brought  about  by  tl 
reaction  of  the  bodies  so  eliminated  upon  the  surrounding  liquid,  or  upor 
the  substance  of  the  electrodes:  honce  the  advantage  of  platinum  to 
latter  purpose,  when  electrolytic  actions  arc  to  be  studied  in  their  pn-ati-! 


, 

simplicity,   that  metal  being  scarcely  attacked  by  any  ordinary  ajrc-nts. 
When,  for  example,  a  solution  of  lead  nitrate  or  acetate  is  decomposed  by 


24:8  ELECTRO-CHEMICAL    DECOMPOSITION; 

the  current  between  platinum  plates,  metallic  lead  is  deposited  at  the  ne- 
gative side,  and  a  brown  powder,  lead  dioxide,  at  the  positive:  the  latter 
substance  is  the  result  of  a  secondary  action;  it  proceeds,  in  fact,  from  the 
nascent  oxygen  at  the  moment  of  its  liberation  reacting  upon  the  monoxide 
of  lead  present  in  the  salt,  and  converting  it  into  dioxide,  which  is  insoluble 
in  the  dilute  acid.  When  nitric  acid  is  decomposed,  no  hydrogen  appears 
at  the  negative  electrode,  because  it  is  oxidized  at  the  expense  of  the  acid, 
which  is  reduced  to  nitrous  acid  gas.  When  potassium  sulphate,  S04K2, 
is  electrolyzed,  hydrogen  appears  at  the  negative  electrode,  together  with 
an  equivalent  quantity  of  potassium  hydrate  OKH,  because  the  potassium 
which  is  evolved  at  the  electrode  immediately  decomposes  the  water  there 
present.  At  the  same  time,  the  sulphione,  S04,  which  is  transferred  to  the 
positive  electrode,  takes  hydrogen  from  the  water  there  present,  forming 
sulphuric  acid,  S04H2,  and  liberating  oxygen.  In  like  manner  hydrogen 
sulphate,  or  sulphuric  acid  itself,  is  resolved  by  the  current  into  hydrogen 
and  sulphione,  which  latter  decomposes  the  water  at  the  positive  electrode, 
reproducing  hydrogen  sulphate,  and  liberating  oxygen,  just  as  if  the  water 
itself  were  directly  decomposed  by  the  current  into  hydrogen  and  oxygen. 
A  similar  action  takes  place  in  the  electrolytic  decomposition  of  any  other 
oxygen-salt  of  an  alkali-metal,  or  alkaline  earth-metal,  alkali  and  hydrogen 
gas  making  their  appearance  at  the  negative  electrode,  acid  and  oxygen 
gas  at  the  positive  electrode.  This  observation  explains  a  circumstance 
which  much  perplexed  the  earlier  experimenters  upon  the  chemical  action 
of  the  voltaic  battery.  In  all  experiments  in  which  water  was  decomposed, 
both  acid  and  alkali  were  liberated  at  the  electrodes,  even  though  distilled 
water  was  employed  ;  and  hence  it  was  believed  for  some  time  that  the 
voltaic  current  had  some  mysterious  power  of  generating  acid  and  alkaline 
matter.  The  true  source  of  these  compounds  was,  however,  traced  by 
Davy,*  who  showed  that  they  proceeded  from  impurities  either  in  the  water 
itself,  or  in  the  vessels  which  contained  it,  or  in  the  surrounding  atmos- 
phere. Having  proved  that  ordinary  distilled  water  always  contains  traces 
of  saline  matter,  he  redistilled  it  at  a  temperature  below  the  boiling-point, 
in  order  to  avoid  all  risk  of  carrying  over  salts  by  splashing.  He  then 
found  that  when  marble  cups  were  used  to  contain  the  water  used  for  de- 
composition, hydrochloric  acid  appeared  at  the  positive  electrode,  soda  at 
the  negative,  both  being  derived  from  sodium-chloride  present  in  the  mar- 
ble; when  agate  cups  were  used,  he  obtained  silica;  and  when  he  used 
gold  vessels,  he  obtained  nitric  acid  and  ammonia,  which  he  traced  to  at- 
mospheric air.  By  operating  in  a  vacuum,  indeed,  the  quantity  of  acid 
and  alkali  was  reduced  to  a  minimum,  but  the  decomposition  was  almost 
arrested,  although  he  operated  with  a  battery  of  fifty  pairs  of  4-inch 
plates.  Hence  it  is  manifest  that  ivater  itself  is  not  an  electrolyte,  but  that  it 
is  enabled  to  convey  the  current  if  it  contains  only  traces  of  saline  matter.f 
If  a  number  of  different  electrolytes,  such  as  dilute  sulphuric  acid,  cupric 
sulphate,  potassium  iodide,  fused  lead  chloride,  &c.,  be  arranged  in  a  series, 
and  the  same  current  be  made  to  traverse  the  whole,  all  will  suffer  decom- 
position at  the  same  time,  but  by  no  means  to  the  same  amount.  If  arrange- 
ments be  made  by  which  the  quantities  of  the  eliminated  elements  can  be 
accurately  ascertained,  it  will  be  found,  when  the  decomposition  has  pro- 
ceeded to  some  extent,  that  these  latter  have  been  disengaged  exactly  in  the 
ratio  of  their  chemical  equivalents.  The  same  current  which  decomposes  9 
parts  of  water  will  separate  into  their  elements  106  parts  of  potassium 
iodide,  139  parts  of  lead  chloride,  &c.  Hence  the  very  important  conclusion  : 
The  action  of  the  current  is  perfectly  definite  in  its  nature,  producing  a  fixed  and 
constant  amount  of  decomposition,  expressed  in  each  electrolyte  by  the  value  of  its 
chemical  equivalent. 

*  Philosophical  Transactions,  1807.  f  Miller's  Chemical  Physics,  p.  484. 


CHEMISTRY    OF    THE    VOLTAIC    PILE. 


249 


Fig.  143. 


From  a  very  extended  series  of  experiments,  based  on  this  and  other 
methods  of  research,  Faraday  was  enabled  to  draw  the  general  inference 
that  effects  of  chemical  decomposition  are  always  proportionate  to  the 
quantity  of  circulating  electricity,  and  may  be  taken  as  an  accurate  and 
trustworthy  measure  of  the  latter.  Guided  by  this  highly  important  prin- 
ciple, he  constructed  his  voltameter,  an  instrument  which  has  rendered  the 
greatest  service  to  electrical  science.  This  is 
merely  an  arrangement  by  which  dilute  sulphuric 
acid  is  decomposed  by  the  current,  the  gas 
evolved  being  collected  and  measured.  By  placing 
such  an  instrument  in  any  part  of  the  circuit, 
the  quantity  of  electric  force  necessary  to  pro- 
duce any  given  effect  can  be  at  once  estimated; 
or,  on  the  other  hand,  any  required  amount  of 
the  latter  can  be,  as  it  were,  measured  out  and 
adjusted  to  the  object  in  view.  The  voltameter 
has  received  many  different  forms:  one  of  the 
most  extensively  useful  is  that  shown  in  fig.  143, 
in  which  the  platinum  plates  are  separated  by  a 
very  small  interval,  and  the  gas  is  collected  in  a 
graduated  jar  standing  on  the  shelf  of  the  pneu- 
matic trough,  the  tube  of  the  instrument,  which 
is  filled  to  the  neck  with  dilute  sulphuric  acid,  being  passed  beneath  the  jar. 

The  decompositions  produced  by  the  voltaic  battery  can  be  effected  by 
the  electricity  of  the  common  machine,  by  that  developed  by  magnetic 
action,  and  by  that  of  animal  origin,  but  to  an  extent  incomparably  more 
minute.  This  arises  from  the  very  small  quantity  of  electricity  set  in  motion 
by  the  machine,  although  its  tension  —  that  is,  power  of  overcoming  obsta- 
cles, and  passing  through  imperfect  conductors  —  is  exceedingly  great.  A 
pair  of  small  wires  of  zinc  and  platinum,  dipping  into  a  single  drop  of 
dilute  acid,  develop  far  more  electricity,  to  judge  from  the  chemical  effects 
of  such  an  arrangement,  than  very  many  turns  of  a  large  plate  electrical 
machine  in  powerful  action.  Nevertheless,  polar  or  electrolytic  decompo- 
sition can  be  distinctly  and  satisfactorily  effected  by  the  latter,  although 
on  a  minute  scale. 

With  a  knowledge  of  the  principles  laid  down,  the  study  of  the  voltaic 
battery  may  be  resumed  and  completed.  In  the  first  place,  two  very 
different  views  have  been  held  concerning  the  source  of  the  electrical  dis- 
turbance in  that  apparatus.  Volta  himself  ascribed  it  to  mere  contact  of 
dissimilar  metals  or  other  substances  conducting  electricity,  —  to  what  was 
denominated  an  electro-motive  force,  called  into  being  by  such  contact. 
Proof  was  supposed  to  be  given  of  this  fundamental  proposition  by  an  ex- 
periment in  which  discs  of  zinc  and  copper  attached  to  insulating  handles, 
after  being  brought  into  close  contact,  were  found,  by  the  aid  of  a  very 
delicate  gold-leaf  electroscope,  to  be  in  opposite  electrical  states.  It  appears, 
however,  that  the  more  carefully  this  experiment  is  made,  the  smaller  is  the 
effect  observed;  and  hence  it  is  judged  highly  probable  that  the  whole  may 
be  due  to  accidental  causes,  against  which  it  is  almost  impossible  to  guard. 

On  the  other  hand,  the  observation  was  soon  made  that  the  power  of  the 
battery  always  bears  some  kind  of  proportion  to  the  chemical  action  upon 
the  zinc ;  that,  for  instance,  when  pure  water  is  used,  the  effect  is  extremely 
feeble;  with  a  solution  of  salt,  it  becomes  much  greater;  and,  lastly,  with 
dilute  acid,  greatest  of  all;  so  that  some  relation  evidently  exists  between 
the  chemical  effect  upon  the  metal  and  the  evolution  of  electrical  force. 

The  experiments  of  Faraday  and  Daniell  have  given  very  great  support 
to  the  chemical  theory,  by  showing  that  the  contact  of  dissimilar  metals  is 
not  necessary  in  order  to  call  into  being  powerful  electrical  currents,  and 


250  ELECTRO-CHEMICAL    DECOMPOSITION; 

that  the  development  of  electrical  force  is  not  only  in  some  way  connected 
with  the  chemical  action  of  the  liquid  of  the  battery,  but  that  it  is  always 
in  direct  proportion  to  the  latter.  One  very  beautiful  experiment,  in  which 
electrolytic  decomposition  of  potassium  iodide  is  performed  by  a  current, 
generated  without  any  contact  of  dissimilar  metals,  can  be  thus  made :  A 
plate  of  zinc  is  bent  at  a  right  angle,  and  cleaned  by  rubbing  with  sand- 
paper. A  plate  of  platinum  has  a  wire  of  the  same  metal  attached  to  it  by 
careful  riveting,  and  the  latter  bent  into  an  arch.  A  piece  of  folded  filter- 
paper  is  wetted  with  solution  of  potassium  iodide,  and  placed  upon  thn 
zinc ;  the  platinum  plate  is  arranged  opposite  to  the  latter,  with  the  end  of 
its  wire  resting  upon  the  paper;  and  then  the  pair  is  plunged  into  a  glass 
of  dilute  sulphuric,  mixed  with  a  few  drops  of  nitric  acid.  A  brown  spot 
of  iodine  becomes  in  a  moment  evident  beneath  the  ex- 
Fig.  144.  tremity  of  the  platinum  wire  —  that  is,  at  the  positive  side 
of  the  arrangement. 

A  strong  argument  in  favor  of  the  chemical  view  is 
founded  on  the  easily  proved  fact,  that  the  direction  of  the 
current  is  determined  by  the  kind  of  action  upon  the  metals, 
the  one  least  attacked  being  always  positive.  Let  two 
polished  pL-ites,  the  one  iron  and  the  other  copper,  be  con- 
nected by  wires  with  a  galvanometer,  and  then  immersed  in 
a  solution  of  an  alkaline  sulphide.  The  needle  in  a  moment 
indicates  a  powerful  current,  passing  from  the  copper 
through  the  liquid  to  the  iron,  and  back  again  through  the 
wire.  Let  the  plates  be  now  removed,  cleaned,  and  plunged 
into  dilute  acid;  the  needle  is  again  driven  round,  but  in 
the  opposite  direction,  the  current  now  passing  from  the 
iron  through  the  liquid  to  the  copper.  In  the  first  instance,  the  copper  is 
acted  upon"  and  not  the  iron;  in  (he  second,  these  conditions  are  reversed, 
and  with  them  the  direction  of  the  current. 

The  metals  employed  in  the  practical  construction  of  voltaic  batteries 
are  zinc  for  the  active  metal,  and  copper,  silver,  or,  still  better,  platinum, 
for  the  inactive  one:  the  greater  the  difference  of  oxidability,  the  better 
the  arrangement.  The  liquid  is  either  dilute  sulphuric  acid,  sometimes 
mixed  with  a  little  nitric,  or  occasionally,  where  very  slow  and  long-con- 
tinued action  is  wanted,  salt  and  water.  To  obtain  the  maximum  effect  of 
the  apparatus  with  the  least  expenditure  of  zinc,  that  metal  must  be  em- 
ployed in  a  pure  state,  or  its  surface  must  be  covered  by  an  amalgam, 
which  in  its  electrical  relations  closely  resembles  the  pure  metal.  The  zinc 
is  easily  brought  into  this  condition  by  wetting  it  with  dilute  sulphuric  acid, 
and  then  rubbing  a  little  mercury  over  it,  by  means  of  a  piece  of  rag  tied 
to  a  stick. 

The  principle  of  the  compound  battery  is,  perhaps,  best  seen  in  the  crown 
of  cups:  by  each  alternation  of  zinc,  fluid,  and  copper,  the  current  is  urged 
forward  with  increased  energy;  its  intensity  is  augmented,  but  the  actual 
amount  of  electrical  force  thrown  into  the  current  form  is  not  increased. 
The  quantity,  estimated  by  its  decomposing  power,  is,  in  fact,  determined 
by  that  of  the  smallest  and  least  active  pair  of  plates,  the  quantity  of 
electricity  in  every  part  or  section  of  the  circuit  being  exactly  equal.  Hence 
large  and  small  plates,  batteries  strongly  and  weakly  charged,  can  never  be 
connected  without  great  loss  of  power. 

When  a  battery,  either  simple  or  compound,  constructed  with  pure  or 
with  amalgamated  zinc,  is  charged  with  dilute  sulphuric  acid,  a  number  of 
highly  interesting  phenomena  may  be  observed.  While  the  circuit  remains 
broken,  the  zinc  is  perfectly  inactive,  no  acid  is  decomposed,  no  hydrogen 
liberated ;  but  the  moment  the  connection  is  completed,  torrents  of  hydrogen 
arise,  not  from  the  zinc,  but  from  the  copper  or  platinum  surfaces  alone, 


CHEMISTRY    OF    THE    VOLTAIC    PILE.  251 

while  the  zinc  undergoes  tranquil  and  imperceptible  oxidation  and  solution. 
Thus,  exactly  the  same  effects  are  seen  to  occur  in  every  active  cell  of  ;i 
closed  circuit,  that  are  witnessed  in  a  portion  of  sulphuric  acid  undergoing 
electrolysis:  oxygen  appears  at  the  positive  side,  with  respect  to  the  cun-n.t, 
and  hydrogen  at  the  negative;  but  with  this  difference  :  that  the  oxygen, 
instead  of  being  set  free,  combines  with  the  zinc.  It  is,  in  fact,  a  real  case 
of  electrolysis,  and  electrolytes  alone  are  available  as  exciting  liquids. 

Common  zinc  is  very  readily  attacked  and  dissolved  by  dilute  sulphuric 
acid  ;  and  this  is  usually  supposed  to  arise  from  the  formation  of  a  multitude 
of  little  voltaic  circles,  by  the  aid  of  particles  of  foreign  metals  or  graphite, 
partially  imbedded  in  the  zinc.  This  gives  rise  in  the  battery  to  what  is 
called  local  action,  by  which,  in  the  common  forms  of  apparatus,  three 
fourths  or  more  of  the  metal  are  often  consumed,  without  contributing  in 
the  least  to  the  general  effect,  but,  on  the  contrary,  injuring  it  to  some  ex- 
tent. This  evil  is  got  rid  of  by  amalgamating  the  surface. 

From  experiments  very  carefully  made  with  a  "dissected"  battery  of 
peculiar  construction,  in  which  local  action  was  completely  avoided,  it  has 
been  distinctly  proved  that  the  quantity  of  electricity  set  in  motion  by  the 
battery  varies  exactly  with  the  zinc  dissolved.  Coupling  this  fact  with  that 
of  the  definite  action  of  the  current,  it  will  be  seen  that  when  a  perfect 
battery  of  this  kind  is  employed  to  decompose  hydrochloric  acid,  in  order 
to  evolve  1  grain  of  hydrogen  from  the  latter,  32-5  grains  of  zinc  must  be 
dissolved  as  chloride,  and  its  equivalent  quantity  of  hydrogen  disengaged 
in  each  active  cell  of  the  battery — that  is  to  say,  that  the  electrical  force 
generated  by  the  solution  of  an  equivalent  of  zinc  in  the  battery  is  capable 
of  effecting  the  decomposition  of  an  equivalent  of  hydrochloric  acid  or  any 
other  electrolyte  out  of  it. 

This  is  an  exceedingly  important  discovery:  it  serves  to  show,  in  the 
most  striking  manner,  the  intimate  nature  of  the  connection  between  chem- 
ical and  electrical  forces,  and  their  remarkable  quantitative  or  equivalent 
relations.  It  almost  seems,  to  use  an  expression  of  Faraday,  as  if  a  trans- 
fer of  chemical  force  took  place  through  the  substance  of  solid  metallic  conduct- 
ors; that  chemical  actions,  called  into  play  in  one  portion  of  the  circuit, 
could  be  made  at  pleasure  to  exhibit  their  eifects  without  loss  or  diminution 
in  any  other. 

There  is  an  hypothesis,  not  of  recent  date,  long  countenanced  and  sup- 
ported by  the  illustrious  Berzelius,  which  refers  all  chemical  phenomena  to 
electrical  forces  —  which  supposes  that  bodies  combine  because  they  are  in 
opposite  electrical  states;  even  the  heat  and  light  accompanying  chemical 
union  may  be,  to  a  certain  extent,  accounted  for  in  this  manner.  In  short, 
we  are  in  such  a  position,  that  either  may  be  assumed  as  cause  or  effect: 
it  may  be  that  electricity  is  merely  a  form  or  modification  of  ordinary  chem- 
ical affinity ;  or,  on  the  other  hand,  that  all  chemical  action  is  a  manifesta- 
tion of  electrical  force.  ,  . 

This  electro-chemical  theory  is  no  longer  received  as  a  true  explanation 
of  chemical  phenomena  to  the  full  extent  intended  by  its  author.  Berzelius, 
indeed,  supposed  that  the  combining  tendencies  of  elements,  and  their  func- 
tions in  compounds,  depend  altogether  on  their  electric  polarity ;  and  ac- 
cordingly he  divided  the  elements  into  two  classes,  the  electro-positive,  which, 
like  hydrogen  and  the  metals,  move  towards  the  negative  pole  of  the  bat- 
tery, as  if  they  were  attracted  by  it,  and  the  electro-negative,  which,  like 
oxygen,  chlorine,  and  bromine,  move  towards  the  positive  pole.  We  are, 
however,  acquainted  with  a  host  of  phenomena  which  show  that  the  chem- 
ical functions  of  an  element  depend  upon  its  position  with  regard  to  other 
elements  in  a  compound,  quite  as  much  as  upon  its  individual  character. 
Thus  chlorine,  the  very  type  of  an  electro-negative  element,  can  be  substi 
tuted  for  hydrogen,  one  of  the  most  positive  of  the  elements,  in  a  large 


252 


ELECTKO-CHEMICAL    DECOMPOSITION 


number  of  compounds,  yielding  new  products,  which  exhibit  the  closest 
analogy  in  composition  and  properties  to  the  compounds  from  which  they 
are  derived.  It  is  impossible,  therefore,  to  admit  that  the  chemical  func- 
tions of  bodies  are  determined  exclusively  by  their  electrical  relations. 
Still  it  is  true  in  a  general  way  that  those  elements  which  differ  most 
strongly  in  their  electrical  characters,  chlorine  and  potassium,  for  example, 
are  likewise  those  which  combine  together  with  the  greatest  energy ;  and 
the  division  of  bodies  into  electro-positive  and  electro-negative  is  therefore 
retained ;  the  former  are  also  called  acid  or  chlorous,  and  the  latter  basylous 
or  zincous. 

One  of  the  most  useful  forms  of  the  common  voltaic  battery  is  that  con- 
trived by  Dr.  Wollaston  (fig.  145).  The  copper  is  made  completely  to  en- 
circle the  zinc  plate,  except  at  the  edges,  the  two  metals  being  kept  apart 
by  pieces  of  cork  or  wood.  Each  zinc  is  soldered  to  the  preceding  copper, 
and  the  whole  screwed  to  a  bar  of  dry  mahogany,  so  that  the  plates  can  be 
lifted  into  or  out  of  the  acid,  which  is  contained  in  an  earthenware  trough, 
divided  into  separate  cells.  The  liquid  consists  of  a  mixture  of  100  parts 
water,  2£  parts  oil  of  vitriol,  and  2  parts  commercial  nitric  acid,  all  by  meas- 
ure. A  number  of  such  batteries  are  easily  connected  together  by  straps 
of  sheet  copper,  and  admit  of  being  put  into  action  with  great  ease. 

Fig.  145. 


The  great  objection  to  this  and  to  all  the  older  forms  of  the  voltaic  bat- 
tery is,  that  the  power  rapidly  decreases,  so  that,  after  a  short  time,  scarcely 
the  tenth  part  of  the  original  action  remains.  This  loss  of  power  depends, 
partly  on  the  gradual  change  of  the  sulphuric  acid  into  zinc  sulphate,  but 
still  more  on  the  coating  of  hydrogen,  and,  at  a  later  stage,  on  the  precipi- 
tation of  metallic  zinc  on  the  copper  plates.  It  is  self-evident  that  if  the 
copper  plate  in  the  liquid  became  covered  with  zinc,  it  would  act  electrically 
like  a  zinc  plate.  This  is  precisely  the  action  of  the  hydrogen,  whereby  a 
decrease  of  electrical  power  is  produced.  This  effect,  produced  by  the  sub- 
stances separated  from  the  liquid,  is  commonly  called  polarization. 

An  apparatus  of  immense  value  for  purposes  of  electro-chemical  research, 
in  which  it  is  desired  to  maintain  powerful  and  equable  currents  for  many 
successive  hours,  has  been  contrived  by  Professor  Daniell  (fig.  146).  Each 
cell  of  this  "constant"  battery  consists  of  a  copper  cylinder  3£  inches  in 
diameter,  and  of  a  height  varying  from  6  to  18  inches.  The  zinc  is  em- 
ployed in  the  form  of  a  rod  f  of  an  inch  in  diameter,  carefully  amalga- 
mated, and  suspended  in  the  centre  of  the  cylinder.  A  second  cell  of  porous 


CHEMISTRY  .OF    THE    VOLTAIC    PILE. 


253 


of  vitriol  and 
Fig.  146. 


earthenware  or  animal  membrane  intervenes  between  the  zinc  and  the  cop- 
per :  this  is  filled  with  a  mixture  of  1  part  by  measure  of  oil  of  vitriol  and 
8  of  water,  and  the  exterior  space  with  the  same  liquid, 
saturated  with  copper  sulphate.  A  sort  of  little  colan- 
der is  fitted  to  the  top  of  the  cell,  in  which  crystals  of 
the  copper  sulphate  are  placed,  so  that  the  strength  of 
the  solution  may  remain  unimpaired.  When  communi- 
cation is  made  by  a  wire  between  the  rod  and  the  cylin- 
der, a  powerful  current  is  produced,  the  power  of  which 
may  be  increased  to  any  extent  by  connecting  a  sufficient 
number  of  such  cells  into  a  series,  on  the  principle  of  the 
crown  of  cups,  the  copper  of  the  first  being  attached  to 
the  zinc  of  the  second.  Ten  such  alternations  constitute 
a  very  powerful  apparatus,  which  has  the  great  advan- 
tage of  retaining  its  energy  undiminished  for  a  long  time. 
By  this  arrangement  of  the  voltaic  battery,  the  polar- 
ization of  the  copper  plate  is  altogether  avoided ;  the  zinc 
in  the  porous  cell,  whilst  it  dissolves  in  the  sulphuric  acid, 
decomposes  it,  but  does  not  liberate  any  hydrogen;  for 
by  the  progress  of  the  decomposition  (see  p.  246)  up  to 
the  boundary  of  the  copper  solution,  the  hydrogen  takes 
the  place  of  the  copper,  and  thus  ultimately  the  copper 
is  precipitated  on  the  copper  plate.  The  copper  plate 


therefore  remains  in  its  original  state,  so  long  as  a  sufficient  quantity  of 
copper  sulphate  is  present  in  the  solution. 

By  increasing  the  generative  and  reducing  the  antagonizing  chemical 
affinities,  Mr.  Grove  succeeded  in  forming  the  constant  nitric  acid  battery 
which  bears  his  name.  This  instrument  is  capable  of  producing  a  fur 
greater  degree  of  power  than  the  battery  previously  mentioned,  and  hence 
it  has  become  one  of  the  most  important  means  of  promoting  electrical 
science  in  the  present  day.  The  zinc  dips  into  dilute  sulphuric  acid;  and 
instead  of  a  solution  of  copper,  concentrated  nitric  acid  is  used,  which 
surrounds  a  platinum  plate.  It  is  evident  that  the  electrolytic  action  which 
begins  at.  the  zinc  passes  through  the  sulphuric  acid,  and  in  a  precisely 
similar  way  through  the  contiguous  nitric  acid.  Hydrogen  would  thus  be 
liberated  on  the  platinum  plate.  This  action  is  not  rendered  visible  by 
the  evolution  of  gas,  but  only  gradually  by  the  change 
of  color  in  the  nitric  acid :  for  the  hydrogen  liberated  Fi9- 147- 

by  the  electrical  action  forms  water  at  the  expense  of 
the  oxygen  yielded  by  the  nitric  acid ;  and  by  this  means, 
so  long  as  sufficient  nitric  acid  is  present,  the  purity  of 
the  surface  of  the  platinum  plate  is  maintained. 

One  of  the  cells  in  this  battery  is  represented  in  sec- 
tion in  fig.  147.  The  zinc  plate  is  bent  wmnd,  so  as  to 
present  a  double  surface,  and  well  amalgamated :  within 
it  stands  a  thin  flat  cell  of  porous  earthenware,  filled 
with  strong  nitric  acid,  and  the  whole  is  immersed  in  a 
mixture  of  1  part  by  measure  of  oil  of  vitriol  and  6  of 
water,  contained  either  in  one  of  the  cells  of  W'ollaston's 
trough,  or  in  a  separate  cell  of  glazed  porcelain,  made 
for  the  purpose.  The  apparatus  is  completed  by  a  plate 
of  platinum  foil,  which  dips  into  the  nitric  acid,  and 
forms  the  positive  side  of  the  arrangement,  With  ten  such  pairs,  experi- 
ments of  decomposition,  ignition  of  wires,  the  light  between  charcoal 
points,  £c.,  can  be  exhibited  with  great  brilliancy,  while  the  battery  itself 
is  very  compact  and  portable,  and,  to  a  great  extent,  constant  in  its  net  ion. 
The  zinc,  as  in  the  case  of  Daniell's  battery,  is  consumed  only  while  the 
22 


A 


254 


ELECTRO-CHEMICAL    DECOMPOSITION  ; 


Fig.  148. 


current  passes,  so  that  the  apparatus  may  be  arranged  an  hour  or  two 
before  it  is  required  for  use,  which  is  often  a  matter  of  great  convenience; 
and  local  action  from  the  precipitation  of  copper  on  the  zinc  is  avoided. 

Professor  Bunsen  has  modified  the  Grove  battery  by  substituting  for  the 
platinum  dense  charcoal  or  coke,  which  is  an  excellent  conductor  of  elec- 
tricity. By  this  alteration,  at  a  very  small  expense,  a  battery  may  be 
made  nearly  as  powerful  and  useful  as  that  of  Grove.  On  account  of  its 
cheapness,  any  one  may  put  together  one  hundred  or  more  of  Bunsen's 
cells,  by  which  the  most  magnificent  phenomena  of  heat  and  light  may  be 
obtained. 

The  accompanying  figure  shows  the  form  of  the  round 
carbon  cylinder,  which  is  used  in  these  cells.  It  is  hol- 
lowed so  as  to  receive  a  porous  earthenware  cell,  in 
which  a  round  plate  of  zinc  is  placed.  The  upper  edge 
of  the  cylinder  of  carbon  is  well  saturated  with  wax, 
and  is  surrounded  by  a  copper  ring,  by  means  of  which 
it  may  be  put  in  connection  with  the  zinc  of  the  adjoin- 
ing pair. 

Bunsen's  carbon  cylinder  is  likewise  well  adapted  for 
the  use  of  dilute  sulphuric  acid  alone,  without  the  addi- 
tion of  nitric  acid.  It  is,  however,  better  to  saturate  the 
dilute  sulphuric  acid  with  potassium  bichromate.  When 
this  mixture  contains  at.  least  double  the  amount  of  sul- 
phuric acid  which  is  necessary  to  decompose  the  chromate,  a  battery  thus 
formed  surpasses  in  power  the  nitric  acid  battery,  but  does  not  furnish 
currents  of  the  same  constancy. 

Mr.  Smee  has  contrived  an  ingenious  battery,  in  which  silver,  covered 
with  a  thin  coating  of  finely  divided  metallic  platinum,  is  employed  in  as- 
sociation with  amalgamated  zinc  and  dilute  sulphuric  acid.  The  rough  sur- 
face appears  to  permit  the  ready  disengagement  of  the  bubbles  of  hydrogen. 
Within  the  last  twenty-five  years,  several  very  beautiful  and  successful 
applications  of  voltaic  electricity  have  been  made,  which  may  be  slightly 
mentioned.  Mr.  Spencer  and  Professor  Jacobi  have  employed  it  in  copy- 
ing, or  rather  in  multiplying,  engraved  plates  and  medals,  by  depositing 
upon  their  surfaces  a  thin  coating  of  metallic  copper,  which,  when  sepa- 
rated from  the  original,  exhibits,  in  reverse,  a  most  faithful  representation 
of  the  latter.  By  using  this  in  its  turn  as  a  mould  or  matrix,  an  absolutely 
perfect  fac-simile  of  the  plate  or  medal  is  obtained.  In  the  former  case, 
the  impressions  taken  on  paper  are  quite  undistinguishable  from  those 
directly  derived  from  the  work  of  the  artist;  and  as  there  is  no  limit  to 
the  number  of  electrotype  plates  which  can  be  thus  produced,  engravings 
of  the  most  beautiful  description  may  be  multiplied  indefi- 
Fig.  149.  nitely.  The  copper  is  very  tough,  and  bears  the  action  of  the 
pre^s  perfectly  well. 

The  apparatus  used  in  this  and  many  similar  processes  is 
of  the  simplest  possible  kind.  A  trough  or  cell  of  wood  is 
divided  by  a  porous  diaphragm,  made  of  a  very  thin  piece 
of  sycamore,  into  two  parts;  dilute  sulphuric  acid  is  put  on 
one  side,  and  a  saturated  solution  of  copper  sulphate,  some- 
times mixed  with  a  little  acid,  on  the  other.  A  plate  of  zinc 
is  soldered  to  a  wire  or  strip  of  copper,  the  other  end  of 
which  is  secured  by  similar  means  to  the  engraved  copper 
plate.  The  latter  is  then  immersed  in  the  solution  of  sulphate, 
and  the  zinc  in  the  acid.  To  prevent  deposition  of  copper  on 
the  back  of  the  copper  plate,  that  portion  is  covered  with 
varnish.  For  medals  and  small  works,  a  porous  earthenware 
cell,  placed  in  a  jelly-jar,  may  be  used, 


CHEMISTRY    OF    THE    VOLTAIC    PILE.  255 

Other  metals  may  be  precipitated  in  the  same  manner,  in  a  smooth  and 
compact  form,  by  the  use  of  certain  precautions  which  have  been  gath- 
ered by  experience.  Electro-gilding  and  plating  are  now  carried  on  very 
largely  and  in  great  perfection  by  Messrs.  Elkington  and  others.  F.vi-ii 
non-conducting  bodies,  as  sealing-wax  and  plaster  of  Paris,  may  be  coated 
with  metal;  it  is  only  necessary,  as  Mr.  Robert  Murray  has  shown,  to  rub 
over  them  the  thinnest  possible  film  of  plumbago.  Seals  may  thus  be  copied 
in  a  very  few  hours  with  unerring  truth. 

Becquerel,  several  years  ago,  published  an  exceedingly  interesting  ac- 
count of  certain  experiments  in  which  crystallized  metals,  oxides,  and 
other  insoluble  substances  had  been  produced  by  the  slow  and  continuous 
action  of  feeble  electrical  currents,  kept  up  for  months,  or  even  years. 
These  products  exactly  resemble  natural  minerals;  and,  indeed,  the  ex- 
periments throw  great  light  on  the  formation  of  the  latter  within  the 
earth.* 

The  common  but  very  pleasing  experiment  of  the  lead-tree  is  greatly 
dependent  on  electro-chemical  action.  When  a  piece  of  zinc  is  suspended 
in  a  solution  of  lead  acetate,  the  first  effect  is  the  decomposition  of  a  por- 
tion of  the  latter,  and  the  deposition  of  metallic  lead  upon  the  surface  of 
the  zinc;  it  is  simply  a  displacement  of  a  metal  by  a  more  oxidable  one. 
The  change  does  not,  however,  stop  here:  metallic  lead  is  still  deposited 
in  large  and  beautiful  plates  upon  that  first  thrown  down,  until  the  solution 
becomes  exhausted,  or  the  zinc  entirely  disappears.  The  first  portions  of 
lead  form  with  the  zinc  a  voltaic  arrangement  of  sufficient 
power  to  decompose  the  salt:  under  the  peculiar  circum-  JV^.150. 

stances  in  which  the  latter  is  placed,  the  metal  is  precipi- 
tated upon  the  negative  portion  —  that  is,  the  lead  —  while 
the  oxygen  and  acid  are  taken  up  by  the  zinc. 

Mr.  Grove  has  contrived  a  battery  in  which  an  electrical 
current,  of  sufficient  intensity  to  decompose  dilute  sulphuric 
acid,  is  produced  by  the  reaction  of  oxygen  upon  hydrogen. 
Each  element  of  this  interesting  apparatus  consists  of  a  pair 
of  glass  tubes  to  contain  the  gases  dipping  into  a  vessel  of 
acidulated  water.  Both  tubes  contain  platinum  plates, 
covered  with  a  rough  deposit  of  finely  divided  platinum, 
and  furnished  with  conducting  wires,  which  pass  through 
the  tops  or  sides  of  the  tubes,  and  are  hermetically  sealed 
into  the  latter.  When  the  tubes  are  charged  with  oxygen 
on  the  one  side  and  hydrogen  on  the  other,  and  the  wires  connected  with  a 
galvanoscope,  the  needle  of  the  instrument  becomes  instantly  affected ;  and 
when  ten  or  more  are  combined  in  a  series,  the  oxygen-tube  of  the  one 
with  the  hydrogen-tube  of  the  next,  &c.,  while  the  terminal  wires  dip  into 
acidulated  water,  a  rapid  stream  of  minute  bubbles  from  either  wire  in- 
dicates the  decomposition  of  the  liquid;  and  when  the  experiment  is  made 
with  a  small  voltameter,  it  is  found  that  the  oxygen  and  hydrogen  disen- 
gaged exactly  equal  in  amount  the  quantities  absorbed  by  the  act  of  com- 
bination in  each  tube  of  the  battery. 

Heat  developed  by  the  Electric  Current.  —  All  parts  of  the  electric  circuit, 
the  plates,  the  liquid  in  the  cells  of  the  battery,  the  conducting  wires.  and 
any  electrolytes  undergoing  decomposition,  all  become  heated  during  the 
passage  of  the  current.  The  rise  of  temperature  in  any  part  of  the  circuit 
depends  partly  on  the  strength  of  the  current,  partly  on  its  resistance, 
those  bodies  which  offer  the  greatest  resistance,  or  are  the  worst  conduct- 
ors, being  most  strongly  heated  by  a  current  of  given  strength.  Thus, 

*  Traite  do  I'Electricitfi  et  du  MagnStisme,  iii.  239. 


256  ELECTRO-CHEMICAL 

when  a  thick  and  a  thin  wire  of  the  same  metal  are  included  in  the  same 
circuit,  the  latter  becomes  most  strongly  heated,  and  a  platinum  wire  is 
much  more  strongly  heated  than  a  silver  or  copper  wire  of  the  same 
thickness. 

By  exact  experiments  it  has  been  found  that  both  in  metallic  wires  and 
in  liquids  traversed  by  an  electric  current,  the  evolution  of  heat  is  directly 
proportional:  1st,  to  the  resistance ;  2d,  to  the  strength  of  the  current.  Joule 
has*  also  shown  that  the  evolution  of  heat  in  each  couple  of  the  voltaic 
battery  is  subject  to  the  same  law,  which,  therefore,  holds  good  in  every 
part  of  the  circuit,  including  the  battery. 

The  strength  of  an  electric  current  is  measured  by  the  quantity  of  de- 
tonating gas  (2  vol.  H.  to  1  vol.  0.)  which  it  can  evolve  from  acidulated 
water  in  a  given  time,  and  the  unit  of  current  strength  is  the  current  which 
eliminates  one  cubic  centimetre  of  detonating  gas  at  0°  C.  and  760mm.  barometric 
pressure  in  a  minute.  Now  Lenz  has  shown  that  when  a  current  of  the  unit  of 
strength  passes  through  a  wire  whose  resistance  is  equal  to  that  of  a  copper 
wire  1  metre  long  and  1  millimetre  in  diameter,  it  develops  a  quantity  of 
heat  sufficient  to  raise  the  temperature  of  1  gram  of  water  from  0°  to  1° 
C.  in  5|  minutes;  and  assuming  as  the  unit  of  heat  the  quantity  required 
to  raise  the  temperature  of  1  gram  of  water  from  0°  to  1°  C.,  the  law  may 
be  thus  expressed: 

A  current  of  the  unit  of  strength  passing  through  a  conductor  ivhich  exerts  the 
unit  of  resistance,  develops  therein  1-057  heat-units  in  an  hour,  or  0.076  heat- 
unit  in  a  minute. 

With  a  current  of  a  given  strength,  the  sum  of  the  quantities  of  heat 
evolved  in  the  battery  and  in  the  metallic  conductor  joining  its  poles,  is 
constant,  the  heat  actually  developed  in  the  one  part  or  the  other  varying 
according  to  the  thickness  of  the  metallic  conductor.  This  was  first  shown 
by  De  la  Rive,  and  has  been  confirmed  by  Favre.f  De  la  Rive  made  use  of 
a  couple  consisting  of  platinum  and  distilled  zinc  or  cadmium,  excited  by 
pure  and  very  strong  nitric  acid,  the  two  metals  being  united  by  a  platinum 
wire,  more  or  less  thick,  which  was  plunged  into  the  same  quantity  of  strong 
nitric  acid  contained  in  a  capsule  similar  to  that  which  held  the  voltaic 
couple.  By  observing  the  temperatures  in  the  two  vessels  with  delicate 
thermometers,  the  sum  of  these  temperatures  was  found  to  be  constant,  the 
one  or  the  other  being  greater  according  to  the  thickness  of  the  connecting 
wire. 

Favre,J  by  means  of  a  calorimeter,  similar  to  that  which  he  used  in  his 
experiments  on  the  development  of  heat  by  chemical  action,  has  shown 
that  in  a  pair  of  zinc  and  platinum  plates,  excited  by  dilute  sulphuric  acid 
and  connected  by  platinum  wires  of  various  length  and  thickness,  for  every 
32-5  grams  of  zinc  dissolved,  a  quantity  of  heat  is  developed  in  the  entire 
circuit  equal  to  18,137  'heat-units,  but  variously  distributed  between  the 
battery-cell  and  the  wire,  according  to  the  thickness  of  the  latter.  Now  this 
quantity  of  heat  is  nearly  the  same  as  that  which  is  evolved  in  the  simple 
solution  of  32 -5  grams  of  zinc  in  dilute  sulphuric  acid,  without  the  formation 
of  a  voltaic  circuit,  viz.  18,444  units.  Hence  Favre  concludes  that  the  heat 
developed  by  the  resistance  of  a  metallic  or  other  conductor  connecting  the 
poles  of  the  battery  is  simply  borrowed  from  the  total  quantity  of  heat 
evolved  by  the  chemical  action  taking  place  in  the  battery,  and  is  rigorously 
complementary  to  that  which  remains  in  the  cells  of  the  battery,  the  heat 
evolved  in  the  entire  circuit  being  the  exact  equivalent  of  the  chemical 
action  which  takes  place.  If  any  external  work  is  performed  by  the  cur- 

*  Phil.  Mag.  [3]  xix.  210.  f  Ann.  Ch.  Phys.  [3J  xl.  393. 

%  Comptes  Reridus,  xlv.  56. 


CRYSTALLIZATION;    CRYSTALLINE    FORM.  257 

rent,  such  as  electrolysis,  or  mechanical  work,   or  by  MM  electro  magnetic 
engine,  the  heat  evolved  in  the  circuit  is  diminished  by  the  heat-eqaivalent 

of  the  decomposition  or  mechanical  work  done. 

CRYSTALLIZATION ;  CRYSTALLINE  FORM. 

Almost  every  substance,  simple  or  compound,  capable  of  existing  in  the 
solid  state,  assumes,  under  favorable  circumstances,  a  distinct  geometrical 
form  or  figure,  usually  bounded  by  plane  surfaces,  and  having  angles  of 
fixed  and  constant  value.  The  faculty  of  crystallization  seems  to  be  denied 
only  to  a  few  bodies,  chiefly  highly  complex  organic  principles,  which  stand, 
as  it  were,  upon  the  very  verge  of  organization,  and  which,  when  in  the 
solid  state,  are  frequently  characterized  by  a  kind  of  beady  or  globular 
appearance,  well  known  to  microscopical  observers. 

The  most  beautiful  examples  of  crystallization  are  to  be  found  among 
natural  minerals,  the  results  of  exceedingly  slow  changes  constantly  occur- 
ring within  the  earth.  It  is  invariably  found  that  artificial  crystals  of  salts, 
and  other  soluble  substances  which  have  been  slowly  and  quietly  deposited, 
surpass  in  size  and  regularity  those  of  more  rapid  formation. 

Solution  in  water  or  some  other  liquid  is  a  very  frequent  method  of 
effecting  crystallization.  If  the  substance  be  more  soluble  at  a  high  than 
at  a  low  temperature,  then  a  hot  and  saturated  solution  left  to  cool  slowly 
will  generally  be  found  to  furnish  crystals;  this  is  a  very  common  case 
with  salts  and  various  organic  principles.  If  it  be  equally  soluble,  or  nearly 
so,  at  all  temperatures,  then  slow  spontaneous  evaporation  in  the  air,  or 
over  a  surface  of  oil  of  vitriol,  often  proves  very  effective. 

Fusion  and  slow  cooling  may  be  employed  in  many  cases :  that  of  sulphur 
is  a  good  example :  the  metals,  when  thus  treated,  usually  afford  traces  of 
crystalline  figures,  which  sometimes  become  very  beautiful  and  distinct,  as 
with  bismuth.  A  third  condition  under  which  crystals  very  often  form  is 
in  passing  from  the  gaseous  to  the  solid  state,  of  which  iodine  affords  a 
good  instance.  When  by  any  of  these  means  time  is  allowed  for  the  sym- 
metrical arrangement  of  the  particles  of  matter  at  the  moment  of  solidifi- 
cation, crystals  are  produced. 

That  crystals  owe  their  figure  to  a  certain  regularity  of  internal  structure 
is  shown  both  by  their  mode  of  formation  and  also  by  the  peculiarities  at- 
tending their  fracture.  A  crystal  placed  in  a  slowly  evaporating  saturated 
solution  of  the  same  substance  grows  or  increases  by  a  continued  deposition 
of  fresh  matter  upon  its  sides,  in  such  a  manner  that  the  angles  formed  by 
the  meeting  of  the  latter  remain  unaltered. 

The  tendency  of  most  crystals  to  split  in  particular  directions,  called  by 
mineralogists  cleavage,  is  a  certain  indication  of  regular  structure,  while 
the  curious  optical  properties  of  many  among  them,  and  their  remarkable 
mode  of  expansion  by  heat,  point  to  the  same  conclusion. 

It  may  be  laid  down  as  a  general  rule  that  every  substance  has  its  own 
crystalline  form,  by  which  it  may  very  frequently  be  recognized  at  once  — 
not  that  each  substance  has  a  different  figure,  although  very  great  diversity 
in  this  respect  is  to  be  found.  Some  forms  are  much  more  common  than 
others,  as  the  cube  and  six-sided  prism,  which  are  very  frequently  assumed 
by  a  number  of  bodies  riot  in  any  way  related. 

The  same  substance  may  have,  under  different  sets  of  circumstances,  as 
high  and  low  temperatures,  two  different  crystalline  forms,  in  which  case 
it  is  said  to  be  dimorphous.  Sulphur  and  carbon  furnish,  as  already  .noticed, 
examples  of  this  curious  fact;  another  case  is  presented  by  calcium  car- 
bonate in  the  two  modifications  of  calc  spar  and  arragonite,  both  chemically 
the  same,  but  physically  different.  A  fourth  example  might  be  given  in 
mercuric  iodide,  which  also  has  two  distinct  forms,  and  oven  two  distinct 
colors,  offering  as  great  a  contrast  as  those  of  diamond  and  graphic. 
22  * 


258 


CRYSTALLINE    FORM. 


The  angles  of  crystals  are  measured  by  means  of  instruments  called  gonio- 
meters, of  which  there  are  two  kinds  in  use,  namely,  the  old  or  common 
goniometer,  and  the  reflecting  goniometer  of  Dr.  Wollaston. 

The  common  goniometer  consists  of  a  pair  of  steel  blades  moving  with 
friction  upon  a  centre,  as  shown  in  fig.  151.  The  edges  a  a  are  carefully 

Fig.  151. 


adjusted  to  the  faces  of  the  crystal  whose  inclination  to  each  other  it  is 
required  to  ascertain,  and  then  the  instrument  being  applied  to  the*  divided 
semicircle,  the  contained  angle  is  at  once  read  off.  An  approximative 
measurement,  within  one  or  two  degrees,  can  be  easily  obtained  by  this 
instrument,  provided  the  planes  of  the  crystal  are  tolerably  perfect,  and 
large  enough  for  the  purpose.  Some  practice  is  of  course  required  before 
even  this  amount  of  accuracy  can  be  attained. 

The  reflecting  goniometer  is  a  very  superior  instrument,  its  indications 
being  correct  within  a  fraction  of  a  degree :  it  is  applicable  also  to  the 
measurement  of  the  angles  of  crystals  of  very  small  size,  the  only  condition 
required  being  that  their  planes  be  smooth  and  brilliant.  The  subjoined 
sketch  (fig.  152)  will  convey,  an  idea  of  its  nature  and  mode  of  use. 

Fig.  152. 


a  is  a  divided  circle  or  disc  of  brass,  the  axis  of  which  passes  stiffly  and 
without  shake  through  the  support  b.  This  axis  is  itself  pierced  to  admit 
the  passage  of  a  round  rod  or  wire,  terminated  by  the  milled-edged  head  c, 
and  destined  to  carry  the  crystal  to  be  measured,  by  means  of  the  jointed 
arm  d.  The  crystal  at  /  can  thus  be  turned  round,  or  adjusted  in  any 


CRYSTALLINE    FORM.  259 

desired  position,  without  the  necessity  of  moving  the  disc.  A  vernier,  e, 
immovably  fixed  to  the  upright  support,  serves  to  measure  with  great  ac- 
curacy the  angular  motion  of  the  divided  circle. 

The  principle  upon  which  the  measurement  of  the  angle  rests  is  very 
simple.  If  the  two  adjacent  planes  of  a  crystal  be  successively  brought 
into  the  same  position,  the  angle  through  which  the  crystal  will  have  moved 
will  be  the  supplement  to  that  contained  between  the  two  planes  If,  for  example, 
in  a  small  crystal,  cab  (fig.  153)  be  the  angle  which  is  to  be  determined) 

Fig.  153. 


and  the  reflecting  surface  a  b  be  placed  in  such  a  position  that  the  reflection 
of  the  image  of  a  distant  point  S  seen  from  0  exactly  covers  a  point  E  lying 
in  the  line  of  the  reflected  ray,  then  the  other  side  a  c  of  the  angle  cab 
must  be  turned  through  the  angle  c  af,  in  order  to  assume  the  same  po- 
sition, and  to  give  the  same  phenomena  as  the  plane  a  b  previously  did. 
The  angle  c  a  f  is  the  supplement  of  the  angle  cab.  All  that  is  required 
to  be  done,  therefore,  is  to  measure  the  angle  c  a  /with  accuracy,  and  sub- 
tract its  value  from  180° ;  and  this  the  goniometer  effects. 

One  method  of  using  the  instrument  is  the  following :  —  The  goniometer 
is  placed  at  a  convenient  height  upon  a  steady  table  in  front  of  a  well 
illuminated  window.  Horizontally  across  the  latter,  at  the  height  of  eight 
or  nine  feet  from  the  ground,  is  stretched  a  narrow  black  ribbon,  while  a 
second  similar  ribbon,  adjusted  parallel  to  the  first,  is  fixed  beneath  the 
window,  a  foot  or  eighteen  inches  above  the  floor.  The  object  is  to  obtain 
two  easily  v'sible  black  lines,  perfectly  parallel.  The  crystal  to  be  examined 
is  •attached  to  the  arm  of  the  goniometer  at  /  by  a  little  wax,  and  adjusted 
in  such  a  manner  that  the  edge  joining  the  two  planes  whose  inclination  is 
to  be  measured  shall  nearly  coincide  with,  or  be  parallel  to.  the  axis  of  the 
instrument.  This  being  done,  the  adjustment  is  completed  in  the  following 
manner:  —  The  divided  circle  is  turned  until  the  zero  of  the  vernier  comes 
to  180° ;  the  crystal  is  then  moved  round  by  means  of  the  inner  axis  c 
(fig.  152)  until  the  eye  placed  near  it  perceives  the  image  of  the  upper 
black  line  reflected  from  the  surface  of  one  of  the  planes  in  question.  Fol- 
lowing this  image,  the  crystal  is  still  cautiously  turned  until  the  upper  black 
line  seen  by  reflection  approaches  and  overlaps  the  lower  black  line  seen 
directly  by  another  portion  of  the  pupil.  It  is  obvious,  that  if  the  plane  of 
the  crystal  be  quite  parallel  to  the  axis  of  the  instrument  (the  latter  being 
horizontal),  the  two  lines  will  coincide  completely.  If,  however,  this  should 
not  be  the  case,  the  crystal  must  be  moved  upon  the  wax  until  the  two  lines 
fall  in  one  when  superposed.  The  second  face  of  the  crystal  must  then  be 
adjusted  in  the  same  manner,  care  being  taken  not  to  derange  the  position 
of  the  first.  When  by  repeated  observation  it  is  found  that  both  have  lieen 
correctly  placed,  so  as  to  bring  the  edge  into  the  required  condition  <>f 
parallelism  with  the  axis  of  motion,  the  measurement  of  the  angle  may  be 
made. 


260  CRYSTALLINE    FORM. 

For  this  purpose  the  crystal  is  moved  as  before  by  the  inner  axis  until 
the  image  of  the  upper  line,  reflected  from  the  first  face  of  the  crystal, 
covers  the  lower  line  seen  directly.  The  great  circle,  carrying  the  whole 
with  it,  is  then  cautiously  turned  until  the  same  coincidence  of  the  upper 
with  the  lower  line  is  seen  by  means  of  the  second  face  of  the  crystal ; 
that  is,  the  second  face  is  brought  into  exactly  the  same  position  as  that 
previously  occupied  by  the  first.  Nothing  then  remains  but  to  read  off  by 
the  vernier  the  angle  through  which  the  circle  has  been  moved  in  this 
operation.  The  division  upon  the  circle  itself  is  very  often  made  bac^vard, 
so  that  the  angle  of  motion  is  not  obtained,  but  its  supplement,  or  the  angle 
of  the  crystal  required. 

It  may  be  necessary  to  remark,  that,  although  the  principle  of  the 
operation  described  is  in  the  highest  degree  simple,  its  successful  practice 
requires  considerable  skill  and  experience. 

If  a  crystal  of  tolerably  simple  form  be  attentively  considered,  it  will  be- 
come evident  that  certain  directions  can  be  pointed  out  in  which  straight 
lines  may  be  imagined  to  be  drawn,  passing  through  the  central  point  of 
the  crystal  from  side  to  side,  from  end  to  end,  or  from  one  angle  to  that 
opposed  to  it,  &c.,  about  which  lines  the  particles  of  matter  composing  the 
crystal  may  be  conceived  to  be  symmetrically  built  up.  Such  lines,  or  axes, 
are  not  always  purely  imaginary,  however,  as  may  be  inferred  from  the  re- 
markable optical  properties  of  many  crystals:  upon  their  number,  relative 
lengths,  position,  and  inclination  to  each  other,  depends  the  outward  figure 
of  the  crystal  itself. 

All  crystalline  forms  may  upon  this  plan  be  arranged  in  six  classes  or 
systems;  these  are  the  following: 

1.  The  monometric,  regular,  or  cubic  system.  —  The  crystals  of  this  division 
have  three  equal  axes,  all  placed  at  right  angles  to  each  other.  The  most 
important  forms  are  the  cube  (1),  the  regular  octahedron  (2),  and  the  rhombic 
dodecahedron  (3). 

The  letters  a — a  (fig.  154)  show  the  termination  of  the  three  axes,  placed 
as  stated. 


Very  many  substances,  both  simple  and  compound,  assume  these  forms, 
as  most  of  the  metals,  carbon  in  the  state  of  diamond,  common  salt,  po- 
tassium iodide,  the  alums,  fluor-spar,  iron  bisulphide,  garnet,  spinelle,  &c. 

2.  The  dimetric,  quadratic,  square  prismatic,  or  pyramidal  system.  —  Three 
axes  are  here  also  observed,  at  right  angles  to  each  other.  Of  these,  how- 
ever, two  only  are  of  equal  length,  the  third  being  longer  or  shorter.  The 
most  important  forms  are,  a  right  square  prism,  in  which  the  lateral  axes 
terminate  in  the  central  point  of  each  side  (1) ;  a  second  right  square  prism, 
in  which  the  axes  terminate  in  the  edges  (2) ;  a  corresponding  pair  of  right, 
square-based  ocfohedrons  (3  and  4). 

Examples  of  these  forms  are  to  be  found  in  zircon,  native  stannic  oxide, 
apophyllite,  yellow  potassium  ferrocyanide,  &c. 


CRYSTALLINE    FORM. 
Fig.  155. 


261 


I... 


a — a.  Principal  or  vertical  axes. 
6 — b.  Secondary  or  lateral  axes. 

3.  The  rhombohedral  system.  —  This  is  very  important  and  extensive ;  it  is 
characterized  by  four  axes,  three  of  which  are  equal,  in  the  same  plane, 
and  inclined  to  each  other  at  angles  of  60°,  while  the  fourth  or  principal 
axis  is  perpendicular  to  all.  The  regular  six-sided  prism  (1),  the  quartz-dode- 
cahedron (2),  the  rhombohedron  (3),  and  a  second  dodecahedron,  called  a 
scalenohedron,  whose  faces  are  scalene  triangles  (4),  belong  to  the  system  in 
question. 

Fig.  156. 
12  34 


a — a.  Principal  axis. 
b — b.   Secondary  axes. 


.  Examples  are  readily  found ;  as  in  ice,  calc  spar,  sodium  nitrate,  beryl, 
quartz  or  rock-crystal,  and  the  semi-metals,  arsenic,  antimony,  and  tel- 
lurium. 

4.    The  trimetric,  rhombic,  or  right  prismatic  system.  —  This  is  characterized 
by  three  axes  of  unequal  lengths,  placed  at  right  angles  to  each  other,  as 


Fig.  157 


Principal  axis, 
b — 6,  C— c.    Secondary  axes. 


in  the  right  rectangular  prism  (1),  the  right  rhombic  prism  ("2},  tho   right  rec- 
tangular-based octohedron  (3),  and  the  right  rhombic-based  octahedron  (4). 


262 


CRYSTALLINE  FORM. 


The  system  is  exemplified  in  sulphur  crystallized  at  a  low  temperature, 
arsenical  iron  pyrites,  potassium  nitrate  and  sulphate,  barium  sulphate,  &c. 

5.  The  monodinic  or  oblique  prismatic  system.  — Crystals  belonging  to  this 
group  have  also  three  axes,  which  may  be  all  unequal;  two  of  these  (the 
secondary)  are  placed  at  right  angles,  the  third  being  so  inclined  as  to  be 
oblique  to  one  and  perpendicular  to  the  other.  To  this  system  may  be  re- 


a — a.  Principal  axis. 

6 — b,  c — c.   Secondary  axes. 

ferredthe  four  following  forms:  The  oblique  rectangular  prism  (1),  the  oblique 
rhombic  prism  (2),  the  oblique  rectangular-based  oclohedron  (3),  the  oblique 
rhombic-based  octohedron  (4). 

Such  forms  are  taken  by  sulphur  crystallized  by  fusion  and  cooling,  real- 
gar, sulphate,  carbonate  and  phosphate  of  sodium,  borax,  green  vitriol, 
and  many  other  salts. 

6.  The  triclinic,  anorthic,  or  doubly  oblique  prismatic  system.  —  The  crys- 
talline forms  comprehended  in  this  division  are,  from  their  great  apparent 
irregularity,  exceedingly  difficult  to  study  and  understand.  In  them  are 


a — a.  Principal  axis,  as  before. 
6 — b,  c — c.  Secondary  axes. 

traced  three  axes,  which  may  be  all  unequal  in  length,  and  are  all  oblique 
to  each  other,  as  in  the  two  doubly  oblique  prisms  (1  and  2),  and  in  the  cor- 
responding doubly  oblique  octohedrons  (3  and  4). 

Copper  sulphate,  bismuth  nitrate,  and  potassium  quadroxalate  afford 
illustrations  of  these  forms. 

If  a  crystal  increase  in  magnitude  by  equal  additions  on  every  part,  it  is 
quite  clear  that  its  figure  must  remain  unaltered ;  but  if,  from  some  cause, 
this  increase  should  be  partial,  the  newly  deposited  matter  being  distributed 
unequally,  but  still  in  obedience  to  certain  definite  laws,  then  alterations 
of  form  are  produced,  giving  rise  to  figures  which  have  a  direct  geometri- 


CRYSTALLINE    FORM.  263 

cal  connection  with  that  from  which  they  are  derived.  If,  for  example,  in 
the  cube,  a  regular  omission  of  successive  rows  of  particles  of  mutter  in  a 
certain  order  be  made  at  each  solid  angle,  while  the  crystal  continues  to 
increase  elsewhere,  the  result  will  be  the  production  of  small  triangular 
planes,  which,  as  the  process  advances,  gradually  usurp  the  whole  of  the 
surface  of  the  crystal,  and  convert  the  cube  into  an  octohedron.  The  new 

Fig.  160. 


Passage  of  cube  to  octohedron. 

planes  are  called  secondary,  and  their  production  is  said  to  take  place  by 
regular  decrements  upon  the  solid  angles.  The  same  thing  may  happen  on 
the  edges  of  the  cube ;  a  new  figure,  the  rhombic  dodecahedron,  is  then 
generated.  The  modifications  which  can  thus  be  produced  of  the  original 
or  primary  figure  (all  of  which  are  subject  to  exact  geometrical  laws)  are 
very  numerous.  Several  distinct  modifications  may  be  present  at  the  same 
time,  and  thus  render  the  form  exceedingly  complex. 

Crystals  often  cleave  parallel  to  all  the  planes  of  the  primary  figure,  as  in 
calc  spar,  which  offers  a  good  illustration  of  this  perfect  cleavage.  Some- 
times one  or  two  of  these  planes  have  a  kind  of  preference  over  the  rest  in 
this  respect,  the  crystal  splitting  readily  in  these  directions  only. 

A  very  curious  modification  of  the  figure  sometimes  occurs  by  the  exces- 
sive growth  of  each  alternate  plane  of  the  crystal;  the  rest  become  at 
length  obliterated,  and  the  crystal  assumes  the  character  called  hemihedral 
or  half-sided.  This  is  well  seen  in  the  production  of  the  tetrahedron  from 
the  regular  octohedron,  and  of  the  rhombohedric  form  by  a  similar  change 
from  the  quartz-dodecahedron  already  figured. 

Fig.  161. 


Passage  of  octohedron  to  tetrahedron. 

Forms  belonging  to  the  same  crystallographic  system  are  related  to  each 
other  by  several  natural  affinities. 

1.  It  is  only  the  simple  forms  of  the  same  system  that  can  combine  into  a  com- 
plex form. —  For  in  all  fully  developed  (holohedral)  natural  crystals  it  is 
found  that  all  the  similar  parts,  if  modified  at  all,  are  modified  in  an  ex- 
actly similar  manner  (in  hemihedral  forms,  half  the^  similar  edges  and 
angles  alternately  situated  are  similarly  modified).  Now  this  can  be  the 
case  only  when  the  dominant  form  and  the  modifying  form  are  developed 
according  to  the  same  law  of  symmetry.  Thus,  if  a  cube  and  a  regular 
octohedron  are  developed  round  the  same  system  of  axes,  each  summit  of 
the  cube  is  cut  off  to  the  same  extent  by  a  face  of  the  octohedron,  or  vice 
versd.  But  a  cube  could  never  combine  in  this  planner  with  a  rhombic  octo- 


264  CRYSTALLINE    FORM;    ISOMORPHISM. 

hedron,  because  it  would  be  impossible  to  place  the  two  forms  in  such  a 
manner  that  similar  parts  of  the  one  should  throughout  replace  similar  parts 
of  the  other. 

The  crystals  of  each  system  are  thus  subject  to  a  peculiar  and  distinct  set 
of  modifications,  the  observation  of  which  very  frequently  constitutes  an 
excellent  guide  to  the  discovery  of  the  primary  form  itself. 

2.  Crystals  belonging  to  the  same  system  are  intimately  related  in  their  optical 
properties.  — Crystals  belonging  to  the  regular  system  (as  the  diamond,  alum, 
rock-salt,  &c.)  refract  light  in  the  same  manner  as  uncrystallized  bodies; 
that  is  to  say,  they  have  but  one  refractive  index,  and  a  ray  of  light  passing 
through  them  in  any  direction  is  refracted  singly.     But  all  other  crystals 
refract  doubly,  that  is  to  say,  a  ray  of  light  passing  through  them  (except 
in  certain  directions)  is  split  into  two  rays,  the  one,  called  the  ordinary  ray, 
being  refracted  as  it  would  be  by  an  amorphous  body,  the  other,  called  the 
extraordinary  ray,  being  refracted  according  to  peculiar  and  more  complex 
laws  (see  LIGHT).     Now  the  crystals  of  the  dimetric  and  hexagonal  systems 
resemble  each  other  in  this  respect,  that  in  all  of  them  there  is  one  direc- 
tion, called  the  optic  axis,  or  axis  of  double  refraction  (coinciding  with  the 
principal  crystallographic   axis),   along  which   a  ray  of  light  is  refracted 
singly,  while  in  all  other  directions  it  is  refracted  doubly;   whereas  in  crys- 
tals belonging  to  the  other  systems,  viz.,  the  trimetric  and  the  two  oblique 
systems,  there  are  always  two  directions  or  axes,  along  which  a  ray  is  singly 
refracted. 

3.  Crystals  belonging  to  the  same  system  resemble  each  other  in  their  mode  of  con- 
ducting heat. —  Amorphous  bodies  and  crystals  of  the  regular  system  con- 
duct heat  equally  in  all  directions,  so  that,  supposing  a  centre  of  heat  to 
exist  within  such  a  body,  the  isothermal  surfaces  will  be  spheres.     But 
crystals  of  the  dimetric  and  hexagonal  systems  conduct  equally  only  in 
directions  perpendicular  to  the  principal  axis,  so  that  in  such  crystals  the 
isothermal   surfaces   are   ellipsoids   of  revolution   around   that  axis ;   and 
crystals  belonging  to  either  of  the  three  other  systems  conduct  unequally 
in  all  directions,  so  that  in  them  the  isothermal  surfaces  are  ellipsoids  with 
three  unequal  axes. 

Relations  of  Form  and  Constitution ;  Isomorphism. 

Certain  substances,  to  which  a  similar  chemical  constitution  is  ascribed, 
possess  the  remarkable  property  of  exactly  replacing  each  other  in  crys- 
tallized compounds  without  alteration  of  the  characteristic  geometrical 
figure.  Such  bodies  are  said  to  be  isomorphous.* 

For  example,  magnesia,  zinc  oxide,  cupric  oxide,  ferrous  oxide,  and 
nickel  oxide  are  allied  by  isomorphic  relations  of  the  most  intimate  nature. 
The  salts  formed  by  these  substances  with  the  same  acid  and  similar  pro- 
portions of  water  of  crystallization,  are  identical  in  their  form,  and,  when 
of  the  same  color,  cannot  be  distinguished  by  the  eye:  the  sulphates  of 
magnesium  and  zinc  may  be  thus  confounded.  These  sulphates,  too,  all 
combine  with  potassium  sulphate  and  ammonium  sulphate,  giving  rise  to 
double  salts,  whose  figure  is  the  same,  but  quite  different  from  that  of  the 
simple  sulphates.  Indeed  this  connection  between  identity  of  form  and 
parallelism  of  constitution  runs  through  all  their  combinations. 

In  the  same  manner  alumina  and  iron  sesquioxide  replace  each  other 
continually  without  change  of  crystalline  figure:  the  same  remark  may  be 
made  of  the  oxides  of  potassium,  sodium,  and  ammonium,  these  bodies 
being  strictly  isomorphous.  The  alumina  in  common  alum  may  be  replaced 
by  iron  sesquioxide,  the  potash  by  ammonia  or  by  soda,  and  still  the  figure 
of  the  crystal  remains  unchanged.  These  replacements  may  be  partial 


Jvom  fffoj.  equal,  and  n6p<j>i],  shape  or  form. 


CRYSTALLINE    FORM  —  ISOMORPHISM.  265 

only:  we  may  have  an  alum  containing  both  potash  and  ammonia,  or 
alumina  and  chromium  sesquioxide.  By  artificial  management — namely, 
by  transferring  the  crystal  successively  to  different  solutions  —  we  may 
have  these  isomorphous  and  mutually  replacing  compounds  distributed  in 
different  layers  upon  the  same  crystal. 

For  these  reasons,  mixtures  of  isomorphous  salts  can  never  be  separated 
by  crystallization,  unless  their  difference  of  solubility  is  very  great.  A 
mixed  solution  of  ferrous  sulphate  and  nickel  sulphate,  isomorphous  salts, 
yields  on  evaporation  crystals  containing  both  iron  and  nickel.  But  if 
before  evaporation  the  ferrous  salt  be  converted  into  ferric  salt,  by  chlorine 
or  other  means,  then  the  crystals  obtained  are  free  from  iron,  except  that 
of  the  mother-liquor  which  wets  them.  The  ferric  salt  is  no  longer  iso- 
morphous with  the  nickel  salt,  and  easily  separates  from  the  latter. 

When  compounds  are  thus  found  to  correspond,  it  is  inferred  that  the 
elements  composing  them  are  also  sometimes  isomorphous.  Thus,  the 
metals  magnesium,  zinc,  iron,  and  copper  are  presumed  to  be  isomorphous: 
arsenic  and  phosphorus  have  not  the  same  crystalline  form;  nevertheless, 
they  are  said  to  be  isomorphous,  because  arsenic  and  phosphoric  acids  give 
rise  to  combinations  which  agree  most  completely  in  figure  and  constitution. 
The  chlorides,  iodides,  bromides,  and  fluorides  agree,  whenever  they  can 
be  observed,  in  the  most  perfect  manner :  hence  the  elements  themselves 
are  believed  to  be  also  isomorphous.  Unfortunately,  for  obvious  reasons, 
it  is  very  difficult  to  observe  the  crystalline  figure  of  most  of  the  elemen- 
tary bodies,  and  this  difficulty  is  increased  by  the  frequent  dimorphism 
they  exhibit. 

Absolute  identity  of  value  in  the  angles  of  crystals  is  not  always  ex- 
hibited by  isomorphous  substances.  In  other  words,  small  variations  often 
occur  in  the  magnitude  of  the  angles  of  crystals  of  compounds  which  in 
all  other  respects  show  the  closest  isomorphic  relations.  This  should  occa- 
sion no  surprise,  as  there  are  reasons  why  such  variations  might  be  ex- 
pected, the  chief  perhaps  being  the  unequal  effects  of  expansion  by  heat, 
by  which  the  angles  of  the  same  crystal  are  changed  by  alteration  of  tem- 
perature. A  good  example  is  found  in  the  case  of  the  carbonates  of  cal- 
cium, magnesium,  manganese,  iron,  and  zinc,  which  are  found  native  crys- 
tallized in  the  form  of  obtuse  rhombohedrons  (fig.  156),  not  distinguishable 
from  each  other  by  the  eye,  or  even  by  the  common  goniometer,  but  show- 
ing small  differences  when  examined  by  the  more  accurate  instrument  of 
Dr.  Wollaston.  These  compounds  are  isomorphous,  and  the  measurements 
of  the  obtuse  angles  of  their  rhombohedrons  are  as  follows: 

Calcium  carbonate  .         .         .  105°    5' 

Magnesium   "  ...  107°  25' 

Manganous  "  ...  107°  20' 

Ferrous          "  ...  107° 

Zinc                "  ...  107°  40' 

Anomalies  in  the  composition  of  various  earthy  minerals,  which  formerly 
threw  much  obscurity  upon  their  chemical  nature,  have  been  in  great 
measure  explained  by  these  discoveries.  Specimens  of  the  same  mineral 
from  different  localities  were  found  to  afford  very  discordant  results  on 
analysis.  But  the  proof  once  given  of  the  extent  to  which  substitution  of 
isomorphous  bodies  may  go,  without  destruction  of  what  may  be  called 
the  primitive  type  of  the  compound,  these  difficulties  vanish. 

Decision  of  a  doubtful  point  concerning  the  constitution  of  a  compound 
may  now  and  then  be  very  satisfactorily  made  by  a  reference  to  this  same 
law  of  isomorphism.  Thus,  alumina,  the  only  known  oxide  of  aluminium, 
is  judged  to  be  a  sesquioxide,  from  its  relation  to  sccquioxide  of  iron, 

23 


266 


CRYSTALLINE  FORM — ISOMORPHISM. 


which  is  certainly  so ;  the  black  oxide  of  copper  is  inferred  to  be  really 
the  monoxide,  although  it  contains  twice  as  much  oxygen  as  the  red  oxide, 
because  it  is  isomorphous  with  magnesia  and  zinc  oxide,  both  undoubted 
monoxides. 

The  subjoined  table  will  serve  to  convey  some  idea  of  the  most  important 
families  of  isomorphous  elements ;  it  is  taken,  with  slight  modification,  from 
Professor  Graham's  Elements  of  Chemistry,*  to  which  the  pupil  is  referred 
for  fuller  details  on  this  interesting  subject: 


(I-) 

Sulphur 
Selenium 
Tellurium. 


.      • 

Magnesium 

Calcium 

Manganese 

Iron 

Cobalt 

Nickel 

Zinc 

Cadmium 

Copper 

Chromium 

Aluminium 

Glucinum. 


Isomorphous  Groups. 

(3.) 

Barium 
Strontium 
Lead. 

(4.) 

Platinum 
Iridium 
Osmium. 


Titanium 

Zirconium 

Tungsten 

Molybdenum 

Tantalum 

Niobium. 


(6.) 
liun 


Sodium 

Silver 

Thallium 

Gold 

Potassium 

Ammonium. 

(70 

Chlorine 
Iodine 
Bromine 
Fluorine 
Cyanogen. 

(8.) 

Phosphorus 
Arsenic 
Antimony 
Bismuth 
Vanadium. 


A  comparison  of  this  table  with  that  on  page  236  will  show  that,  in  many 
instances,  isomorphous  elements  exhibit  equal  equivalence  or  combining 
power,  and  more  generally  that  the  isomorphous  groups  consist  either 
wholly  of  perissad  or  wholly  of  artiad  elements.  The  only  apparent  ex- 
ception to  this  rule  is  aiforded  by  tantalum  and  niobium,  which,  although 
pentads,  are  isomorphous  with  tin,  tungsten,  and  other  tetrad  and  hexad 
elements. 

*  Second  Am.  edition,  p.  149. 


CHEMISTRY  OF  THE  METALS, 

rpHE  metals  constitute  the  second  and  larger  group  of  elementary  bodies. 
JL  A  great  number  of  them  are  of  very  rare  occurrence,  being  found  only 
in  a  few  scarce  minerals ;  others  are  more  abundant,  and  some  few  almost 
universally  diffused  throughout  the  globe.  Some  of  these  bodies  are  of 
most  importance  when  in  the  metallic  state  ;  others,  when  in  combination, 
chiefly  as  oxides,  the  metals  themselves  being  almost  unknown.  Many  are 
used  in  medicine  and  in  the  arts,  and  are  essentially  connected  with  the 
progress  of  civilization. 

If  arsenic  be  included,  the  metals  amount  to  fifty  in  number. 

Physical  Properties. — One  of  the  most  remarkable  and  striking  charac- 
ters possessed  by  the  metals  is  their  peculiar  lustre :  this  is  so  character- 
istic, that  the  expression  metallic  lustre  has  passed  into  common  speech. 
This  property  is  no  doubt  connected  with  the  extraordinary  degree  of  opa- 
city which  the  metals  present  in  every  instance.  The  thinnest  leaves  or 
plates,  and  the  edges  of  crystalline  laminae,  arrest  the  passage  of  light  in 
the  most  complete  manner.  An  exception  to  the  rule  is  usually  made  in 
favor  of  gold-leaf,  which,  when  held  up  to  the  daylight,  exhibits  a  greenish, 
and  in  some  cases  a  purple  color,  as  if  it  were  really  endued  with  a  certain 
degree  of  translucency :  the  metallic  film  is,  however,  generally  so  imper- 
fect that  it  is  somewhat  difficult  to  say  whether  the  observed  effect  may  not 
be  in  some  measure  due  to  multitudes  of  little  holes,  many  of  which  are 
visible  to  the  naked  eye;  but  Faraday's  experiments  have  established  the 
translucency  of  gold  beyond  all  doubt. 

In  point  of  color,  the  metals  present  a  certain  degree  of  uniformity :  with 
two  exceptions  —  viz.,  copper,  which  is  red,  and  gold,  which  is  yellow  — 
all  these  bodies  are  included  between  the  pure  white  of  silver  and  the 
bluish-gray  tint  of  lead :  bismuth,  it  is  true,  has  a  pinkish  color,  and  cal- 
cium and  strontium  a  yellowish  tint,  but  these  tints  are  very  feeble. 

The  differences  of  specific  gravity  are  very  wide,  passing  from  lithium, 
potassium,  and  sodium,  which  are  lighter  than  water,  to  platinum,  which  is 
nearly  twenty-one  times  heavier  than  an  equal  bulk  of  that  liquid. 

Table  of  the  Specific  Gravities  of  Metals  at  15-5°  C.  (60°  F.) 

Platinum  .  .  .  .21-50 
Gold  ....  19-50 
Uranium  ....  18-4 
Tungsten  .  .  .  17-00 
Mercury  ....  13-59 
Palladium  .  .  .  11-30  to  11-8 

Lead H'45 

Silver  ....  10-50 
Bismuth  .  .  .  .9-90 
Copper  ....  8-96 

Nickel  ....  8-80 
Cadmium  .  .  .  8-70 

Molybdenum       .         .         .8-63 


268 


CHEMISTRY    OF    THE    METALS. 


Cobalt       . 

Manganese 

Iron 

Tin 

Zinc 

Antimony 

Tellurium  . 

Arsenic 

Aluminium 

Magnesium  . 

Sodium     . 

Potassium    . 

Lithium    . 


8-54 

8-00 

7-79 

7-29 

6-86  to  7-1 

6-80 

6-11 

5-88 

2-56  to  2-67 

1-75 

0-972 

0-865 

0-593 


The  property  of  malleability,  or  power  of  extension  under  the  hammer, 
or  between  the  rollers  of  the  flatting-mill,  is  possessed  by  certain  of  the 
metals  to  a  very  great  extent.  Gold-leaf  is  a  remarkable  example  of  the 
tenuity  to  which  a  malleable  metal  may  be  brought  by  suitable  means.  '  The 
gilding  on  silver  wire  used  in  the  manufacture  of  gold  lace  is  even  thinner, 
and  yet  presents  an  unbroken  surface.  Silver  may  be  beaten  out  very  thin  — 
copper  also,  but  to  an  inferior  extent ;  tin  and  platinum  are  easily  rolled 
out  into  foil ;  iron,  palladium,  lead,  nickel,  cadmium,  the  metals  of  the 
alkalies,  and  mercury  when  solidified,  are  also  malleable.  Zinc  may  be 
placed  midway  between  the  malleable  and  brittle  division ;  then  perhaps 
bismuth ;  and,  lastly,  such  metals  as  antimony  and  arsenic,  which  are  al- 
together destitute  of  malleability. 

The  specific  gravity  of  malleable  metals  is  usually  very  sensibly  increased 
by  pressure  or  blows,  and  the  metals  themselves  are  rendered  much  harder, 
with  a  tendency  to  brittleness.  This  condition  is  destroyed  and  the  former 
soft  state  restored  by  the  operation  of  annealing,  which  consists  in  heating 
the  metal  to  redness  out  of  contact  with  air  (if  it  will  bear  that  temperature 
without  fusion),  and  cooling  it  quickly  or  slowly  according  to  the  circum- 
stances of  the  case.  After  this  operation,  it  is  found  to  possess  its  original 
specific  gravity. 

Ductility  is  a  property  distinct  from  the  last,  inasmuch  as  it  involves  the 
principle  of  tenacity,  or  power  of  resisting  tension.  The 
Fig.  162.  art  of  wire-drawing  is  one  of  great  antiquity  :  it  consists  in 
drawing  rods  of  metal  through  a  succession  of  trumpet- 
shaped  holes  in  a  steel  plate,  each  being  a  little  smaller  than 
its  predecessor,  until  the  requisite  degree  of  fineness  is  at- 
tained. The  metal  often  becomes  very  hard  and  rigid  in 
this  process,  and  is  then  liable  to  break :  this  is  remedied  by 
annealing.  The  order  of  tenacity  among  the  metals  suscep- 
tible of  being  easily  drawn  into  wire  is  the  following:  it  is 
determined  by  observing  the  weights  required  to  break 
asunder  wires  drawn  through  the  same  orifice  of  the  plate : 


\J 


Iron 
Copper 
Platinum 
Silver 


Gold 
Zinc 
Tin 
Lead. 


Metals  differ  as  much  in  fusibility  as  in  density.  The  following  table  will 
give  an  idea  of  their  relations  to  heat.  The  melting-points  of  the  metals 
which  fuse  only  at  a  temperature  above  ignition,  and  that  of  zinc,  are  on 
the  authority  of  the  late  Professor  Daniell,  having  been  observed  by  the 
help  of  his  pyrometer  before  described: 


CHEMISTRY   OF    THE    METALS. 


269 


"  Mercury 

Melting  points. 
F.           C. 

Rubidium 
Potassium 
Sodium 
Lithium 
Tin    , 

101-3     38-5 
144-5     62-5 
207-7     97-6 
356      180 
442      2°7-8 

Fusible  below 
a  red  heat. 

Cadmium 
Bismuth    . 
Thallium 
Lead 

(about)  442      228 
497      258 
561      294 
617      325 

Tellurium  —  rather  less  fusible  than  lead. 
Arsenic  —  unknown. 

Zinc 773 

Antimony — just  below  redness. 


412 


Melting  points. 

F.                C. 

f  Silver    

1873°       1023° 

1996         1091 

Gold      

2016         1102 

2786         1530 

v 

Pure  iron 

Nickel 

Cobalt 

•  Highest  heat  of  forge 

. 

Manganese 

Palladium 

Infusible  below 

Molybdenum 

a  red  heat. 

Uranium 

Agglomerate,  but  do  not  melt  in  the 

Tungsten 

forge. 

Chromium 

Titanium 

Cerium 

Osmium 
Iridium 
Rhodium 

Infusible  in  ordinary  blast-furnaces  ; 
fusible  by  oxy-hydrogen  blowpipe. 

Platinum 

Tantalum 

Some  metals  acquire  a  pasty  or  adhesive  state  before  becoming  fluid: 
this  is  the  case  with  iron  and  platinum,  and  also  with  the  metals  of  the 
alkalies.  It  is  this  peculiarity  which  confers  the  very  valuable  property  of 
welding,  by  which  pieces  of  iron  and  steel  are  united  without  solder,  and 
the  finely  divided  metallic  sponge  of  platinum  is  converted  into  a  solid  and 
compact  bar. 

Volatility  is  possessed  by  certain  members  of  this  class,  and  perhaps  by 
all,  could  temperatures  sufficiently  elevated  be  obtained.  Mercury  boils 
and  distils  below  a  red  heat;  potassium,  sodium,  zinc,  magnesium,  and 
cadmium  rise  in  vapor  when  heated  to  bright  redness ;  arsenic  and  tellu- 
rium are  volatile. 
23* 


270  CHEMISTRY    OF    THE    METALS. 


CHEMICAL  RELATIONS  OF  THE  METALS. 

Metallic  combinations  are  of  two  kinds  —  namely,  those  formed  by  the 
union  of  metals  among  themselves,  which  are  called  alloys,  or,  where  mer- 
cury is  concerned,  amalgams;  and  those  generated  by  combination  with 
the  non-metallic  elements,  as  oxides,  chlorides,  sulphides,  &c.  In  this 
latter  case,  the  metallic  characters  are  almost  invariably  lost. 

Alloys.  —  Most  metals  are  probably,  to  some  extent,  capable  of  existing 
in  a  state  of  combination  with  each  other  in  definite  proportions;  but  it 
is  difficult  to  obtain  these  compounds  in  a  separate  condition,  since  they 
dissolve  in  all  proportions  in  the  melted  metals,  and  do  not  generally  differ 
so  widely  in  their  melting  points  from  the  metals  they  may  be  mixed  with, 
as  to  be  separated  by  crystallization  in  a  definite  condition.  Exceptions 
to  this  rule  are  met  with  in  the  cooling  of  argentiferous  lead,  the  crystal- 
lization of  brass,  and  of  gun-metal. 

The  chemical  force  capable  of  being  exerted  between  different  metals  is 
for  the  most  part  very  feeble,  and  the  consequent  state  of  combination  is 
therefore  very  easily  disturbed  by  the  influence  of  other  forces.  The 
stability  of  such  metallic  compounds  is,  however,  greater  in  proportion  to 
the  general  chemical  dissimilarity  of  the  metals  they  contain.  But  in  all 
cases  of  combination  between  metals,  the  alteration  of  physical  characters, 
which  is  the  distinctive  feature  of  chemical  combination,  does  not  take 
place  to  any  great  extent.  The  most  unquestionable  compounds  of  metals 
with  metals  are  still  metallic  in  their  general  physical  characters,  and  there 
is  no  such  transmutation  of  the  individuality  of  their  constituents  as  takes 
place  in  the  combination  of  a  metal  with  oxygen,  or  sulphur,  chlorine,  &c. 
The  alteration  of  characters  in  alloys  is  generally  limited  to  the  color,  de- 
gree of  hardness,  tenacity,  &c.,  and  it  is  only  when  the  constituent  metals 
are  capable  of  assuming  opposite  chemical  relations  that  these  compounds 
are  distinguished  by  great  brittleness. 

The  formation  of  actual  chemical  compounds,  in  some  cases,  when  two 
metals  are  melted  together,  is  indicated  by  several  phenomena,  viz.,  the 
evolution  of  heat,  as  in  the  case  of  platinum  and  tin,  copper  and  zinc,  &c. 
The  density  of  alloys  differs  from  that  of  mere  mixtures  of  the  metals. 
In  the  solidification  of  alloys,  the  temperature  does  not  always  fall  uni- 
formly, but  often  remains  stationary  at  particular  degrees,  which  may  be 
regarded  as  the  solidifying  points  of  the  compounds  then  crystallizing. 
Tin  and  lead  melted  together  in  any  proportions  always  form  a  compound 
which  solidifies  at  187°  C.  The  melting-point  of  an  alloy  is  often  very 
different  from  the  point  of  solidification,  and  it  is  generally  lower  than 
the  mean  melting  point  of  the  constituent  metals. 

But  though  metals  may  combine  when  melted  together,  it  is  doubtful 
whether  they  remain  combined  after  the  solidification  of  the  mass,  and  the 
wide  differences  between  the  melting  and  solidifying  points  of  certain  alloys 
appear  to  indicate  that  the  existence  of  these  compounds  is  limited  to  a 
certain  range  of  temperature.  Matthiessen*  regards  it  as  probable  that 
the  condition  of  an  alloy  of  two  metals  in  the  liquid  state  may  be  either 
that  of — 1.  A  solution  of  one  metal  in  another;  2.  Chemical  combination ; 
3.  Mechanical  mixture ;  or,  4.  A  solution  or  mixture  of  two  or  all  of  the 
above;  and  that  similar  differences  may  obtain  as  to  its  condition  in  the 
solid  state. 

The  chemical  action  of  reagents  upon  alloys  is  sometimes  very  different 
from  their  action  upon  metals  in  the  separate  state  :  thus,  platinum  alloyed 

*  British  Association  Reports,  1863,  p.  97. 


CLASSIFICATION    OF    METALS.  271 

with  silver  is  readily  dissolved  by  nitric  acid,  but  is  not  affected  by  that 
acid  when  unalloyed.  On  the  contrary,  silver,  which  in  the  separate  sun- 
is  readily  dissolved  by  nitric  acid,  is  not  dissolved  by  it  when  alloyed  with 
gold  in  proportions  much  less  than  one  fourth  of  the  alloy  by  weight. 

COMPOUNDS  OF  METALS  WITH  METALLOIDS.  — CLASSIFICATION  OF  METALS. 

A  classification  of  the  metals  according  to  their  equivalence  or  atomicity 
is  given  in  the  table  on  p.  236,  each  of  the  classes  thus  formed  being  divided 
into  groups,  the  individual  members  of  which  possess  certain  physical  or 
chemical  characters  in  common. 

CLASS  I.  —  Monad  Metals. — 1.  Among  these  metals  potassium,  sodium, 
csesium,  rubidium,  and  lithium  are  called  alkali-metals.  They  are  soft,  easily 
fusible,  volatile  at  higher  temperatures;  combine  very  energetically  with 
oxygen;  decompose  water  at  all  temperatures;  and  form  strongly  basic 
oxides,  which  are  very  soluble  in  water,  yielding  powerfully  caustic  and 
alkaline  hydrates,  from  which  the  water  cannot  be  expelled  by  heat.  Their 
carbonates  are  soluble  in  water,  arid  each  metal  forms  only  one  chloride. 
The  hypothetical  metal  ammonium,  NH4  (p.  348),  is  usually  added  to  the  list 
of  alkali-metals,  on  account  of  the  general  similarity  of  its  compounds  to 
those  of  potassium  and  sodium. 

2.  Silver  differs  greatly  from  the  alkali-metals  in  its  physical  and  most  of 
its  chemical  properties,  but  it  is  related  to  them  by  the  isomorphism  of 
some  of  its  compounds  with  the  corresponding  compounds  of  those  metuls; 
thus  it  forms  an  alum,  similar  in  form  and  composition  to  ordinary  potash 
alum. 

CLASS  II.  —  Dyad  Metals. — 1.  The  three  metals,  barium,  strontium,  and 
calcium,  form  oxides  called  alkaline  earths,  less  soluble  in  water  than  the  true 
alkalies,  but  exhibiting  similar  taste,  causticity,  and  action  on  vegetable 
colors.  The  metals  of  this  group  form  but  one  chloride,  e.g.  BaCl2;  their 
carbonates  are  insoluble  in  water,  and  barium  sulphate  is  also  insoluble ; 
strontium  and  calcium  sulphates  slightly  soluble. 

2.  The  metals  of  the  next  group,  viz.  glucinum,  thorinum,  yttrium,  erbium, 
lanthanum,  and  didymium,  form  oxides  called  earths,  which  are  insoluble  in 
water,  and  cannot  be  reduced  to  the  metallic  state  by  hydrogen  or  carbon ; 
their  carbonates  are   insoluble  in  water,  their  sulphates  soluble.     These 
metals  also  form  but  one  chloride,  viz.  a  dichloride.    They  are  all  very  rare. 

3.  Magnesium,  zinc,  and  cadmium  resemble  one  another  in  being  volatile  at 
high  temperatures,  and  burning  when  heated  in  the  air ;  they  decompose 
water  at  high  temperatures,  eliminate  hydrogen  from  dilute  acids,  and  form 
only  one  oxide  and  one  chloride,  e.g.  ZnO  and  ZnCl2.     Magnesium  was  for- 
merly classed  as  an  earth-metal,  but  it  bears  a  much  closer  analogy  to  zinc. 

4.  Mercury  and  copper  each  form  two  chlorides  and  two  oxides  :   mercury, 
for  example,  forms  the  two  chlorides,  HgCl2  and  II<r2Cla,  and  the  two  oxides, 
HgO  and  Hg20.     Mercurous  chloride  (calomel)  is  represented  by  the  for- 

Hg-Cl  .  Hg 

mula  ,  and  the  corresponding  oxide  by    |  >0.      The  copper  com- 

Hg-Cl  Hg 

pounds  are  similarly  constituted.  These  metals  do  not  decompose  water  at 
any  temperature  ;  they  are  oxidized  by  nitric  and  by  strong  sulphuric  acid. 
The  oxides  of  mercury  are  reduced  to  the  metallic  state  by  heat  alone ; 
those  of  copper,  by  ignition  with  hydrogen  or  charcoal. 

CLASS  III. — Triad  Metals. — The  only  two  metals  belonging  to  this  class 
are  thallium  and  gold.  Each  of  them  forms  a  monochloridc  and  a  trichlo- 
ride, also  corresponding  oxides,  e.g.  gold  chlorides,  AuCl  and  AuCl3;  oxides, 


272  CLASSIFICATION    OF    METALS. 

Au20  and  Au203.  The  mono-compounds  of  thallium  are  much  more  stable 
than  the  tri-compounds,  and  in  respect  of  these  compounds  thallium  exhibits 
very  close  analogies  with  the  alkali-metals,  forming,  for  example,  an  alum 
isomorphous  with  common  potash  alum,  and  phosphates  analogous  in  com- 
position to  the  phosphates  of  sodium. 

CLASS  IV.  —  Tetrad  Metals.  —  1.  Platinum,  palladium,  iridium,  rhodium, 
ruthenium,  and  osmium  form  a  natural  group  of  metals,  occurring  together 
in  the  metallic  state,  and  resembling  each  other  in  many  of  their  proper- 
ties. Platinum  and  palladium  form  dichlorides  and  tetrachlorides,  with 
corresponding  oxides,  as,  e.g.,  PtCl2,  PtCl4,  PtO,  Pt02.  Iridium  forms  a 
dichloride,  a  tetrachloride,  and  an  intermediate  chloride,  lr2C!6,  which  may 
be  regarded  as  a  compound  of  the  other  two,  or  as  constituted  according  to 

IrCl3 
the  formula  |        .     Ruthenium  and  osmium  form  chlorides  similar  in  con- 

IrCl3 

stitution  to  those  of  iridium  ;  rhodium  only  a  dichloride,  RhCl2,  and  a  tri- 
chloride, Rli2Cl6.  All  these  metals  form  oxides  analogous  in  composition 
to  their  chlorides,  e.  g.  IrO,  Ir203,  Ir02  and  likeAvise  higher  oxides,  iridium 
and  rhodium  forming  trioxides,  Ir03  and  Rh03,  and  osmium  and  ruthenium 
forming  tetroxides,  Os04  and  Ru04:  whence  it  might  be  inferred  that 
iridium  and  rhodium  are  hexad,  osmium  and  ruthenium  octads ;  but  there 
are  no  Chlorides  corresponding  to  these  oxides,  and,  as  already  observed 
(p.  355),  the  atomicity  of  an  element  cannot  be  inferred  from  the  composi- 
tion of  its  oxides.  The  metals  of  the  platinum  group  are  not  acted  upon  by 
nitric  acid,  but  only  by  chlorine  or  nitromuriatic  acid.  With  the  exception 
of  osmium,  they  do  not  oxidize  in  the  air  at  any  temperature,  and  their 
oxides  are  all  reducible  by  heat  alone.  These  metals,  together  with  gold, 
silver,  and  mercury,  which  likewise  exhibit  the  last-mentioned  character, 
are  sometimes  called  noble  metals. 

2.  Tin  and  titanium  are  closely  related  to  silicium,  each  forming  a  volatile 
tetrachloride ;  namely,  stannic  chloride,  SnCl4,  and  titanic  chloride,  TiCl4, 
together  with  the  corresponding  oxides.     Tin  likewise  forms  the  stannous 
compounds,  in  which  it  is  bivalent,  e.g.,  SnCl2,  SnO;  and  titanium  forms 
the  titanous  compounds,  in  which  it  is   apparently  trivalent,  but  really 
quadrivalent,  like  aluminium. 

3.  Lead  stands  by  itself.     Its  quadrivalence  is  inferred  from  the  compo- 
sition of  plumbo-tetrethide,  Pb(C2H5)4;    but  in  most  of  its  compounds  it  is 
bivalent,    forming   only  one    chloride,   PbCl2,   with  corresponding  iodide, 
bromide,  and  fluoride.    It  forms  also  the  corresponding  oxide,  PbO,  together 
with  a  lower  oxide,  Pb20,  and  three  higher  oxides,  Pb304.  Pb405,  and  Pb02. 
Lead  is  allied  to  barium  and  strontium  by  isomorphism  of  its  sulphate  with 
the  sulphates  of  barium  and  strontium,  and  to  silver,  thallium,  and  mercury 
by  the  sparing  solubility  of  its  chloride,  which  is  precipitated  by  hydro- 
chloric acid  from  solutions  of  lead  salts. 

4.  Zirconium  forms  a  tetrachloride,  ZrCl4,  and  a  dioxide,  Zr02.    Aluminium 
is  inferred  to  be  tetradic  from  its  analogy  to  iron  in  the  ferric  compounds, 
but  it  forms  only  one  class  of  salts  in  which  it  is  apparently  trivalent,  the 

A1C13  0=A1 

chloride  being  A12C16  —  I        ,  and  the  oxide  I  >0.      Aluminium  and 

A1C13  0  =A1 

zirconium  belong  to  the  class  of  earth-metals,  and  will  be  described  in  con- 
nection with  them. 

5.  The  Iron  group  comprises  iron,  manganese,  cobalt,  nickel,  uranium,  cerium, 
and  indium.     The  atomicity  of  these  metals  has  already  been  discussed. 
Manganese  forms  a  chloride  of  somewhat  doubtful  composition,  in  which  it 
is  apparently  septivalent ;  but  the  rest  do  not  form  any  compounds  with 


CLASSIFICATION    OF    METALS.  273 

monad  elements  in  which  they  exhibit  an  equivalent  value  greater  than  4. 
All  these  metals  decompose  water  at  high  temperatures.  N\ckel  and  cobalt 
are  magnetic,  like  iron,  and  their  salts  are  isomorphous  with  the  cor- 
responding iron  compounds.  Indium  is  a-very  rare  metal,  which  has  been 
but  imperfectly  examined,  but  it  probably  belongs  to  the  same  group. 

CLASS  V. — Pentad  Metals.  —  1.  Arsenic  and  antimony  form  trichlorides  and 
pentachlorides  analogous  to  those  of  phosphorus,  also  the  corresponding 
oxides.  Bismuth  forms  a  volatile  trichloride,  and  a  dichloride,  BLCL. 

BiCl2 
or       |        .      Vanadium  was  formerly  supposed  to  belong  to  the  tungsten 

BiCl2 

group,  but  it  has  lately  been  shown  to  be  a  pentad.  Its  chlorides  are  not 
known,  but  it  forms  an  oxychloride,  VOC13,  analogous  to  phosphorus  oxy- 
chloride  ;  also  the  oxides,  V203  and  V./)5,  analogous  to  those  of  phosphorus 
and  arsenic,  the  latter  yielding  a  series  of  salts,  the  vanadates,  isomorphous 
with  the  phosphates  and  arsenates  of  corresponding  composition. 

2.  Tantalum  and  niobium,  formerly  regarded  as  tetrads,  have  lately  been 
shown  by  Marignac  to  form  pentachlorides  and  pentoxides.  The  oxides  of 
the  pentad  metals  are,  for  the  most  part,  of  acid  character. 

CLASS  VI. — Hexad  Metals.  —  1.  Chromium  forms  a  hexfluoride,  CrF6,  and 
a  corresponding  oxide,  Cr03.  It  likewise  forms  two  series  of  compounds, 
in  which  it  exhibits  lower  degrees  of  equivalence,  viz.,  the  chromic  com- 
pounds analogous  to  the  ferric  compounds,  in  which  it  is  apparently  tri- 

Offff  C18 
valent,  but  really  quadrivalent:   e.g.,  chromic  chloride,  Cr.,Cl6  or    I 

Cr"'  n3 

and  the  chromous  compounds,  analogous  to  the  ferrous  compounds,  in  which 
it  is  bivalent,  e.g.,  Cr"Cl2,  Cr"0. 

2.  Tungsten  forms  a  hexchloride,  WC16,  and  the  corresponding  oxide, 
W03.  Molybdenum  is  not  known  to  form  a  chloride  higher  than  MoCl4,  but 
its  trioxide,  Mo03,  is  known;  and  from  the  general  similarity  of  the  tung- 
sten and  molybdenum  compounds,  the  latter  metal  is  inferred  to  the  hexadic. 

The  metals  of  the  alkalies  and  alkaline  earths,  on  account  of  their  inferior 
specific  gravity,  are  often  called  light  metals  ;  the  others,  heavy  metals. 


Metallic  Chlorides.  —  All  metals  combine  with  chlorine,  and  most  of  them 
in  several  proportions,  as  above  indicated,  forming  compounds  which  niuy 
be  regarded  as  derived  from  one  or  more  molecules  of  hydrochloric  acid, 
by  substitution  of  a  metal  for  an  equivalent  quantity  of  hydrogen ;  thus  : 

From  HC1     are  derived  monochlorides  like  KC1 
«      H.C12          "  dichlorides          "     Ba"Cla 

"      H,CL          "  trichlorides        "     AuC13 

"      H^Cl^          "  tetrachlorides    "     SnifCl4,  &c.  &c. 

Hydrochloric  acid  may,  in  fact,  be  regarded  as  the  type  of  chlorides  in 
general. 

Several  chlorides  occur  as  natural  products.  Sodium  chloride,  or  com- 
mon salt,  occurs  in  enormous  quantities,  both  in  the  solid  state  as  rock-salt, 
and  dissolved  in  sea-water,  and  in  the  water  of  rivers  and  springs.  Po- 
tassium chloride  occurs  in  the  same  forms,  but  in  smaller  quantity  ;  Uie 
chlorides  of  lithium,  csesium,  rubidium,  and  thallium  also  occur  in  small 


274  CHEMISTRY    OF    THE    METALS. 

quantities  in  certain  spring  waters.     Mercurous  chloride,  Hg2Cl2,  and  silver 
chloride,  AgCl,  occur  as  natural  minerals. 

1.  Chlorides  are  generally  prepared  by  one  or  other  of  the  following 
processes:   1.  By  acting  upon  the  metal  with  chlorine  gas.     Antimony  pen- 
tachloride  and  copper  dichloride  are  examples  of  chlorides  sometimes  pro- 
duced in  this  manner.     The  chlorides  of  gold  and  platinum  are  usually  pre- 
pared by  acting  upon  the  metals  with  nascent  chlorine,  developed  by  hydro- 
chloric and  nitric  acids.     Sometimes,  on  the  other  hand,  the  metal  is  in  a 
nascent  state,  as  when  titanic  chloride  is  formed  by  passing  a  current  of 
chlorine  over  a  heated  mixture  of  charcoal  and  titanic  oxide.     The  chlo- 
rides of  aluminium  and  chromium  may  be  obtained  by  similar  processes. 

2.  Chlorine  gas,  by  its  action  upon  metallic  oxides,  drives  out  the  oxygen, 
and  unites  with  the  respective  metals  to  form  chlorides.     This  reaction 
sometimes  takes  place  at  ordinary  temperatures,  as  is  the  case  with  silver 
oxide  ;   sometimes  only  at  a  red  heat,  as  is  the  case  with  the  oxides  of  the 
alkalies  and  alkaline  earth-metals.      The  hydrates  and  carbonates  of  these 
last  metals,  when  dissolved  or  suspended  in  hot  water  and  treated  with  ex- 
cess of  chlorine,  are  converted,  chiefly  into  chlorides,  partly  into  chlorates. 

3.  Many  metallic  chlorides  are  prepared  by  acting  upon  the  metals  with 
hydrochloric  acid.     Zinc,   cadmium,   iron,  nickel,  cobalt,  and  tin  dissolve 
readily  in  hydrochloric  acid,  with  liberation  of  hydrogen  ;  copper  only  in 
the  strong  boiling  acid;   silver,  mercury,   palladium,  platinum,  and  gold, 
not  at  all.     Sometimes  the  metal  is  substituted,  not  for  hydrogen,  but  for 
some  other  metal.     Stannous  chloride,  for  instance,  is  frequently  made  by 
distilling  metallic  tin  with  mercuric  chloride;  thus:  2HgCl«  -f-  Sn2  =  2Snd, 


4.  By  dissolving  a  metallic  oxide,  hydrate,  or  carbonate  in  hydrochloric 
acid. 

All  monochlorides  and  dichlorides  are  soluble  in  water,  excepting  silver 
chloride,  AgCl,  and  mercurous  chloride,  Hg2Cl2  ;  lead  chloride,  PbCl2,  is 
sparingly  soluble  ;  these  three  chlorides  are  easily  formed  by  precipitation. 
Many  metallic  chlorides  dissolve  also  in  alcohol  and  in  ether. 

Most  monochlorides,  dichlorides,  and  trichlorides  volatilize  at  high  tem- 
peratures without  decomposition  :  the  higher  chlorides,  when  heated,  give 
off  part  of  their  chlorine.  Some  chlorides  which  resist  the  action  of  heat 
alone  are  decomposed  by  ignition  in  the  air,  yielding  metallic  oxides  and 
free  chlorine  :  this  is  the  case  with  the  dichlorides  of  iron  and  manganese  ; 
but  most  dichlorides  remain  undecomposed,  even  in  this  case.  All  metallic 
chlorides,  excepting  those  of  the  alkali-metals  and  earth-metals,  are  de- 
composed at  a  red  heat  by  hydrogen  gas,  with  formation  of  hydrochloric 
acid  :  in  this  way,  metallic  iron  may  be  obtained  in  fine  cubical  crystals. 
Silver  chloride  placed  in  contact  with  metallic  zinc  or  iron,  under  dilute  sul- 
phuric or  hydrochloric  acid,  is  reduced  to  the  metallic  state  by  the  nascent 
hydrogen. 

Sulphuric,  phosphoric,  boric,  and  arsenic  acids  decompose  most  metallic 
chlorides,  sometimes  at  ordinary,  sometimes  at  higher  temperatures.  All 
metallic  chlorides,  heated  with  lead  dioxide  or  manganese  dioxide  and  sul- 
phuric acid,  give  off  chlorine,  e.  g,  : 

2NaCl  -f    Mn02   -f   2S04H2  =   S04Na2   -f   S04Mn   -j-  20H2  -f  C12. 

Sodium        Manganese        Sulphuric  Sodium  Mauganous 

chloride.         dioxide.  acid.  sulphate.  sulphate. 

Chlorides  distilled  with  sulphuric  acid  and  potassium  chromate,  yield  a 
dark  bluish-red  distillate  of  chromic  oxychloride.  Some  metallic  chlorides 
are  decomposed  by  water,  forming  hydrochloric  acid  and  an  oxychloride, 
e.  g.  :  BiCL,  -f  OH2  =  2HC1  -f-  BiClO.  The  chlorides  of  antimony  and 


CHLORIDES;  BROMIDES.  275 

stannous  chloride  are  decomposed  in  a  similar  manner.  All  soluble  chlo- 
rides give  with  solution  of  silver  nitrate,  a  white  precipitate  of  silver  chlo- 
ride, easily  soluble  in  ammonia,  insoluble  in  nitric  acid.  With  nt> mtrons 
nitrate,  they  yield  a  white  curdy  precipitate  of  mercurous  chloride,  black- 
ened by  ammonia;  and  with  lead-salts,  not  too  dilute,  a  white  crystalline 
precipitate  of  lead  chloride,  soluble  in  excess  of  water. 

Metallic  chlorides  unite  with  each  other  and  with  the  chlorides  of  the 
non-metallic  elements,  forming  such  compounds  as  potassium  chloromcrcu- 
rate,  2KCl.HgCl2,  sodium  chloroplatinate,  2NaCl.PtCl4,  r>otassium  chlorio- 
date,  KC1,IC13,  &c  Metallic  chlorides  combine  in  definite  proportions  with 
ammonia  and  organic  bases;  the  chlorides  of  platinum  form  with  ammonia 
the  compounds  2NH3.PtCl2,  4NH3.PtCl2,  2NHs.PtCl4,  and  4NH3.PtCl4;  mer- 
curic chloride  forms  with  aniline  the  compound  2C6H7N.HgCl2,  &c. 

Chlorides  also  unite  with  oxides  and  sulphides,  forming  oxy chlorides  and 
oxy sulphides,  which  may  be  regarded  as  chlorides  having  part  of  their  chlo- 
rine replaced  by  an  equivalent  quantity  of  oxygen  or  sulphur  (C12  by  0  or  S). 
Bismuth,  for  example,  forms  an  oxychloride  having  the  composition  Bi/x/C10 
or  BiCls.Bi208. 

Bromides.  —  Bromine  unites  directly  with  most  metals,  forming  com- 
pounds analogous  in  composition  to  the  chlorides,  and  resembling  them  in 
most  of  their  properties.  The  bromides  of  the  alkali-metals  occur  in  sea- 
water  and  in  many  saline  springs ;  silver  bromide  occurs  as  a  natural 
mineral.  Nearly  all  bromides  are  soluble  in  water,  and  may  be  formed  by 
treating  an  oxide,  hydrate,  or  carbonate,  with  hydrobromic  acid,  the  solu- 
tions when  evaporated  giving  oif  water  for  the  most  part,  and  leaving  a 
solid  metallic  bromide ;  some  of  them,  however,  namely,  the  bromides  of 
magnesium,  aluminium,  and  the  other  earth-metals,  are  more  or  less 
decomposed  by  evaporation,  giving  off  hydrobromic  acid,  and  leaving  a 
mixture  of  metallic  bromide  and  oxide.  Silver  bromide  and  mercurous 
bromide  are  insoluble  in  water,  and  lead  bromide  is  very  sparingly  soluble ; 
these  are  obtained  by  precipitation. 

Metallic  bromides  are  solid  at  ordinary  temperatures ;  most  of  them  fuse 
at  a  moderate  heat,  and  volatilize  at  higher  temperatures.  The  bromides 
of  gold  and  platinum  are  decomposed  by  mere  exposure  to  heat;  many 
others  give  up  their  bromine  when  heated  in  contact  with  the  air.  Chlo- 
rine, with  the  aid  of  heat,  drives  out  the  bromine  and  converts  them  into 
chlorides.  Hydrochloric  acid  also  decomposes  them  at  a  red  heat,  giving  off 
hydrobromic  acid.  Strong  sulphuric  or  nitric  acid  decomposes  them,  with 
evolution  of  hydrobromic  acid,  which,  if  the  sulphuric  or  nitric  acid  is  con- 
centrated and  in  excess,  is  partly  decomposed,  with  separation  of  bromine 
and  formation  of  sulphurous  oxide  or  nitrogen  dioxide.  Bromides  heated 
with  sulphuric  acid  and  manganese  dioxide  or  potassium  chromate,  give  off  free 
bromine. 

Bromides  in  solution  are  easily  decomposed  by  chlorine,  either  in  the 
form  of  gas  or  dissolved  in  water,  the  liquid  acquiring  a  red  or  reddish- 
yellow  color,  according  to  the  quantity  of  bromine  present;  and  on  agitat- 
ing the  liquid  with  ether,  that  liquid  dissolves  the  bromine,  forming  a  red 
solution,  which  rises  to  the  surface. 

Soluble  bromides  give  with  silver  nitrate  a  white  precipitate  of  silver 
bromide,  greatly  resembling  the  chloride,  but  much  less  soluble  in  am- 
monia, insoluble  in  hot  nitric  acid.  Mercurous  nitrate  produces  a  yellowisl 
white  precipitate ;  and  lead  acetate,  a  white  precipitate  much  less  soluble 
in  water  than  the  chloride.  Palladium  nitrate  produces  in  solutions  of 
bromides  not  containing* chlorine,  a  black  precipitate  of  bromide.  Pal- 
ladium chloride  produces  no  precipitate;  neither  does  the  nitrate,  il 
soluble  chlorides  are  present. 


276  CHEMISTRY    OF    THE    METALS. 

Bromides  unite  with  each  other  in  the  same  manner  as  chlorides;  also 
with  oxides,  sulphides,  and  ammonia. 

Iodides.  —  These  compounds  are  obtained  by  processes  similar  to  those 
which  vield  the  chlorides  and  bromides.  Many  metals  unite  directly  with 
iodine.  Potassium  and  sodium  iodides  exist  in  sea-water  and  in  many  salt 
springs;  silver  iodide  occurs  as  a  natural  mineral. 

Metallic  iodides  are  analogous  to  the  bromides  and  chlorides  in  compo- 
sition and  properties.  But  few  of  them  are  decomposed  by  heat  alone ; 
the  iodides  of  gold,  silver,  platinum,  and  palladium,  however,  give  up  their 
iodine  when  heated. 

Most  metallic  iodides  are  perfectly  soluble  in  water;  but  lead  iodide  is 
very  slightly  soluble,  and  the  iodides  of  mercury  and  silver  are  quite  in- 
soluble. 

Solutions  of  iodides  evaporated  out  of  contact  of  air,  generally  leave 
anhydrous  metallic  iodides,  which  partly  separate  in  the  crystalline  form 
before  the  water  is  wholly  driven  off.  The  iodides  of  the  earth-metals, 
however,  are  resolved,  on  evaporation,  into  the  earthy  oxides  and  hydri- 
odic  acid,  which  escapes.  A  very  small  quantity  of  chlorine  colors  the 
solution  yellow  or  brown,  by  partial  decomposition;  and  a  somewhat 
larger  quantity  takes  up  the  whole  of  the  metal,  forming  a  chloride,  and 
separates  the  iodine,  which  then  gives  a  blue  color  with  starch ;  a  still 
larger  quantity  of  chlorine  gives  the  liquid  a  paler  color,  and  converts  the 
separated  iodine  into  trichloride  of  iodine,  which  does  not  give  a  blue 
color  with  starch,  and  frequently  enters  into  combination  with  the  metallic 
chloride  produced.  Strong  sulphuric  acid  and  somewhat  concentrated  nitric 
acid  color  the  solution  yellow  or  brown ;  and  if  the  quantity  of  the  iodide 
is  large,  and  the  solution  much  concentrated  or  heated,  they  liberate  iodine, 
which  partly  escapes  in  violet  vapors.  Starch  mixed  with  the  solution, 
even  if  it  be  very  dilute,  is  turned  blue  —  permanently,  when  the  decom- 
position is  effected  by  sulphuric  acid ;  for  a  time  only  when  it  is  effected 
by  nitric  acid,  especially  if  that  acid  be  added  in  large  quantity. 

The  aqueous  solution  of  an  iodide  gives  a  brown  precipitate  with  salts 
of  bismuth;  orange-yellow  with  lead-salts;  dirty-white  with  cuprous  salts, 
and  also  with  cupric  salts,  especially  on  the  addition  of  sulphurous  acid ; 
greenish-yellow  with  mercurous  salts ;  scarlet  with  mercuric  salts ;  yellowish- 
white  with  silver  salts;  lemon-yellow  with  gold  salts;  brown  with  platinic 
salts  —  first,  however,  turning  the  liquid  dark  brown-red;  and  black  with 
salts  of  palladium,  even  when  extremely  dilute.  All  these  precipitates 
consist  of  metallic  iodides,  many  of  them  soluble  in  excess  of  the  soluble 
iodide :  the  silver  precipitate  is  insoluble  in  nitric  acid  and  very  little  sol- 
uble in  ammonia. 

Metallic  iodides  unite  with  one  another,  forming  double  iodides,  analogous 
to  the  double  chlorides;  they  also  absorb  ammonia  gas  in  definite  propor- 
tions. Some  of  them,  as  those  of  antimony  and  tellurium,  unite  with  the 
oxides  of  the  corresponding  metals,  forming  oxyiodides. 

Fluorides. — These  compounds  are  formed:  1.  By  heating  hydrofluoric 
acid  with  certain  metals. — 2.  By  the  action  of  that  acid  on  metallic  ox- 
ides.—  3.  By  heating  electro-negative  metals  —  antimony,  for  example  — 
with  fluoride  of  lead  or  fluoride  of  mercury.  —  4.  Volatile  metallic  fluorides 
may  be  prepared  by  heating  fluor-spar  with  sulphuric  acid  and  the  oxide 
of  the  metal. 

Fluorides  have  no  metallic  lustre ;  most  of  them  are  easily  fusible,  and 
for  the  most  part  resemble  the  chlorides.  They  are  not  decomposed  by 
ignition,  either  alone  or  when  mixed  with  charcoal.  When  ignited  in  contact 
with  the  air,  in  a  flame  which  contains  aqueous  vapor,  many  of  them  are 
converted  into  oxides,  while  the  flugrine  is  criven  off  as  hydrofluoric  acid. 


FLUORIDES  ;    CYANIDES.  277 

All  fluorides  are  decomposed  by  chlorine  and  converted  into  chlorides. 
They  are  not  decomposed  by  phosphoric  oxide,  unless  silica  is  present.  They 
are  decomposed  at  a  gentle  heat  by  strong  sulphuric  acid,  with  formation  of 
a  metallic  sulphate  and  evolution  of  hydrofluoric  acid. 

The  fluorides  of  tin  and  silver  are  easily  soluble  in  water;  those  of  po- 
tassium, sodium,  and  iron  are  sparingly  soluble;  those  of  strontium  and 
cadmium  very  slightly  soluble,  and  the  rest  insoluble.  The  solutions  of 
ammonium,  potassium,  and  sodium  fluoride  have  an  alkaline  reaction.  The 
aqueous  solutions  of  fluorides  corrode  glass  vessels  in  which  they  are  kept 
or  evaporated.  They  form  with  soluble  calcium-salts  a  precipitate  of  cal- 
cium fluoride,  in  the  form  of  a  transparent  jelly,  which  is  scarcely  visible, 
because  its  refractive  power  is  nearly  the  same  as  that  of  the  liquid ;  the 
addition  of  ammonia  makes  it  plainer.  This  precipitate,  if  it  does  not 
contain  silica,  dissolves  with  difficulty  in  hydrochloric  or  nitric  acid,  and 
is  re-precipitated  by  ammonia.  The  aqueous  fluorides  give  a  pulverulent 
precipitate  with  lead  acetate. 

The  fluorides  of  antimony,  arsenic,  chromium,  mercury,  niobium,  os- 
mium, tantalum,  tin,  titanium,  tungsten,  and  zinc,  are  volatile  without 
decomposition. 

Fluorine  has  a  great  tendency  to  form  double  salts,  consisting  of  a  fluo- 
ride of  a  basic  or  positive  metal  united  with  the  fluoride  of  hydrogen, 
boron,  silicon,  tin,  titanium,  zirconium,  &c.,  e.g.: 

Potassium  hydrofluoride  .         .         .    KHF2     =  KF.HF. 
Potassium  borofluoride     .         .         .         KBF4     =  KF.BF3. 

Potassium  silicofluoride  .         .         .    K2SiF6  =  2KF.SiF4. 
Potassium  titanofluoride  .         .         .         K.2TiF6  =  2KF.TiF4. 

Potassium  stannofluoride  .         .         .    K2SnFa  =  2KF.SnF4. 
Potassium  zircofluoride    .         .         .         K2ZrF,  =  2KF.ZrF4. 

The  four  classes  of  compounds  just  described,  the  chlorides,  bromides, 
iodides,  and  fluorides,  form  a  group  often  designated  as  haloid  compounds  or 
haloid*  salts,  from  their  analogy  to  sodium  chloride  or  sea-salt,  which  may 
be  regarded  as  a  type  of  them  all.  The  elements,  chlorine,  bromine,  iodine, 
and  fluorine,  are  called  halogens. 

Cyanides.  — Closely  related  to  these  haloi'd  compounds  are  the  cyanides, 
formed  by  the  union  of  metals  with  the  group  CN,  cyanogen,  which  is  a 
monatomic  radical  derived  from  the  saturated  molecule,  CivNx//H  (hydrocy- 
anic acid),  by  abstraction  of  H. ;  in  short,  the  cyanides  may  be  regarded  as 
chlorides  having  the  element  Cl  replaced  by  the  compound  radical  CN. 

Some  metals  —  potassium  among  the  number  —  are  converted  into  cyanides 
by  heating  them  in  cyanogen  gas  or  vapor  of  hydrocyanic  acid.  The  cya- 
nides of  the  alkali-metals  are  also  formed  (together  with  cyanates)  by  pass- 
ing cyanogen  gas  over  the  heated  hydrates  or  carbonates  of  the  same  metals; 
potassium  cyanide  also,  by  passing  nitrogen  gas  over  a  mixture  of  charcoal 
and  hydrate  or  carbonate  of  potassium  at  a  bright-red  heat.  Cyanides  are 
formed  abundantly  when  nitrogenous  organic  compounds  are  heated  with 
fixed  alkali.  Other  modes  of  formation  will  be  mentioned  hereafter. 

The  cyanides  of  the  alkali-metals  and  of  barium,  strontium,  calcium,  mag- 
nesium, and  mercury,  are  soluble  in  water,  and  may  be  produced  by  t not- 
ing the  corresponding  oxides  or  hydrates  with  hydrocyanic  acid.  Nearly 
all  other  metallic  cyanides  are  insoluble,  and  are  obtained  by  precipitation 
from  the  soluble  cyanides. 

The  cyanides  of  the  alkali-metals  sustain  a  red  heat  without  decomposi- 
tion, provided  air  and  moisture  be  excluded.  The  cyanides  of  many  of  the 

*  From  uA>,  the  sea. 

24 


278  CHEMISTRY    OF    THE    METALS. 

heavy  metals,  as  lead,  iron,  cobalt,  nickel,  and  copper,  under  these  circum- 
stances, give  off  all  their  nitrogen  as  gas,  and  leave  a  metallic  carbonate; 
mercuric  cyanide  is  resolved  into  mercury  and  cyanogen  gtis;  silver  cyanide 
gives  off  half  its  cyanogen  as  gas.  Most  cyanides,  when  heated  with  dilute 
acids,  give  off  their  cyanogen  as  hydrocyanic  acid. 

Cyanides  have  a  strong  tendency  to  unite  with  one  another,  forming 
double  cyanides.  The  most  important  of  these  are  the  double  cyanides  of 
iron  and  potassium,  namely,  potassio-ferrous  cyanide  Fe/xK4(CN)6,  commonly 
called  yellow  prussiate  of  potash;  and potassio-ferric  cyanide,  Fe/x/K3(CN  }6, 
commonly  called  red  prussiate  of  potash.  Both  these  are  splendidly  crys- 
talline salts,  which  dissolve  easily  in  water,  and  form  highly  characteristic 
precipitates  with  many  metallic  salts.  These  salts,  with  the  other  cyanides, 
will  be  more  fully  described  under  "Organic  Chemistry;"  but  they  are 
mentioned  here,  on  account  of  their  frequent  use  in  the  qualitative  analysis 
of  metallic  solutions. 

Oxides.  —  All  metals  combine  with  oxygen,  and  most  of  them  in  several 
proportions.  In  almost  all  cases  oxides  are  formed  corresponding  in  com- 
position to  the  chlorides,  one  atom  of  oxygen  taking  the  place  of  two  atoms 
of  chlorine.  Many  metals  also  form  oxides  to  which  no  chlorine  analogues 
are  known ;  thus,  lead,  which  forms  only  one  chloride,  PbCl2,  forms,  in 
addition  to  the  monoxide,  PbO,  a  dioxide,  Pb02,  besides  oxides  of  interme- 
diate composition ;  osmium  also,  the  highest  chloride  of  which  is  OsCl4, 
forms,  in  addition  to  the  dioxide,  a  trioxide  and  a  tetroxide.  This  arises 
from  the  fact  that  any  number  of  atoms  of  oxygen  or  other  dyad  element 
may  enter  into  a  compound  without  disturbing  the  balance  of  equivalency 
(p.  235). 

Just  as  chlorides  are  derived  by  substitution  from  hydrochloric  acid,  HC1 
(p.  304),  so  likewise  may  oxides  be  derived  from  one  or  more  molecules  of 
water,  H20  ;  but  as  the  molecule  of  water  contains  two  hydrogen-atoms,  the 
replacement  of  the  hydrogen  may,  as  already  explained  (p.  223),  be  either 
total  or  partial,  the  product  in  the  first  case  being  an  anhydrous  metallic 
oxide,  and  in  the  second  a  hydrated  oxide  or  hydrate,  in  which  the  oxygen 
is  associated  both  with  hydrogen  and  with  metal ;  in  this  manner  the  fol- 
lowing hydrates  and  anhydrous  oxides  may  be  constituted : 

Type.  Hydrates.  Oxides. 

H20    .         .         .     KHO  .     K20 

Ba"0 
H40.        .         .         Ba"H202.         .         .         SnK>2 

Bi'"H02 
H603  .         .         .     AsvH03          .         .      •  .     Sb'"20» 

Sn*vH203   .         .         .         W™03 
H804        .         .         ZrivH404        .         .         .     Osviii04 

H1005 Sbv206. 

It  may  be  observed  that  the  hydrates  of  artiad  metals  contain  the  ele- 
ments of  a  molecule  of  the  corresponding  anhydrous  oxide,  and  of  one  or 
more  molecules  of  water;  thus; 

Barium  hydrate        ,  Ba//H202  ~  Ba"O.H20 

Stannic  hydrate  .....     SnivH203  =  Snlv02.H2O 
Zirconium  hydrate  ,  ZrivH404  —  Zriv02.2H2O. 

But  the  hydrate  of  a  perissad  metal  contains  in  its  molecule  only  half  the 
number  of  atoms  required  to  make  up  a  molecule  of  oxide  together  with  a 
molecule  of  water ;  thus ; 

Potassium  hydrate          .         .         .     KHO          =  £  (K2O.H2Oj 
Bismuth  hydrate         ,         .         .         Bi///H02  =  J  (Bi"'2O3.H20) 
Arsenic  hydrate     ....     As^H03     ==  |  (Asv206.H20). 


OXIDES.  279 

These  perissad  hydrates  cannot,  therefore,  be  correctly  regarded  as  com- 
pounds of  anhydrous  oxide  and  water. 

Many  metallic  oxides  occur  as  natural  minerals,  and  some,  especially 
those  of  iron,  tin,  and  copper,  in  large  quantities,  forming  ores  from  which 
the  metals  are  extracted. 

All  metals,  except  gold,  platinum,  iridium,  rhodium,  and  ruthenium,  are 
capable  of  uniting  directly  with  oxygen.  Some,  as  potassium,  sodium,  and 
barium,  oxidize  rapidly  on  exposure  to  the  air  at  ordinary  temperatures, 
and  decompose  water  with  energy.  Most  metals,  however,  when  in  the 
massive  state,  remain  perfectly  bright  and  unacted  on  in  dry  air  or  oxygen 
gas,  but  oxidize  slowly  when  moisture  is  present;  such  is  the  case  with 
iron,  zinc,  and  lead.  Some  of  the  ordinarily  permanent  metals,  when  in  a 
very  finely  divided  state,  as  lead  when  obtained  by  ignition  of  its  tartrate, 
and  iron  reduced  from  its  oxide  by  ignition  iu  hydrogen  gas,  take  fire  and 
oxidize  spontaneously  as  soon  as  they  come  in  contact  with  the  air.  Lead, 
iron,  copper,  and  the  volatile  metals,  arsenic,  antimony,  zinc,  cadmium, 
and  mercury,  are  converted  into  oxides  when  heated  in  air  or  oxygen. 
Many  metals,  especially  at  a  red  heat,  are  readily  oxidized  by  water  or 
steam.  A  very  general  method  of  preparing  metallic  oxides  is  to  subject 
the  corresponding  hydrates,  carbonates,  nitrates,  sulphates,  or  any  oxygen- 
salts  containing  volatile  acids,  to  the  action  of  heat. 

Oxides  are  for  the  most  part  opaque  earthy  bodies,  destitute  of  metallic 
lustre.  The  majority  of  them  are  fusible;  those  of  lead  and  bismuth  at  a 
low  red  heat;  those  of  copper  and  iron  at  a  white  heat;  those  of  barium 
and  aluminium  before  the  oxy-hydrogen  blowpipe ;  while  calcium  oxide 
(lime)  does  not  fuse  at  any  temperature  to  which  it  has  yet  been  subjected. 
Oxides  are,  for  the  most  part,  much  less  fusible  than  the  uncombined 
metals.  Osmium  tetroxide,  and  the  trioxides  of  arsenic  and  antimony, 
are  readily  volatile. 

A  greater  or  less  degree  of  heat  effects  the  decomposition  of  many  me- 
tallic oxides.  Those  of  gold,  platinum,  silver,  and  mercury  are  reduced 
to  the  metallic  or  reguline  state  by  an  incipient  red  heat.  At  a  somewhat 
higher  temperature,  the  higher  oxides  of  barium,  cobalt,  nickel,  and  lead 
are  reduced  to  the  state  of  monoxides ;  while  the  tri-metallic  tetroxides  of 
manganese  and  iron,  Mn904  and  Fe304,  are  produced  by  exposing  manga- 
nese dioxide,  Mn02,  and  iron  sesquioxide,  Fe203,  respectively  to  a  still 
Stronger  heat.  By  gentle  ignition,  arsenic  pentoxide  is  reduced  to  the 
state  of  trioxide,  and  chromium  trioxide  to  sesquioxide. 

The  superior  oxides  of  the  metals  are  easily  reduced  to  a  lower  state  of 
oxidation  by  treatment  with  a  current  of  hydrogen  gas  at  a  more  or  less 
elevated  temperature.  At  a  higher  degree  of  heat,  hydrogen  gas  will  trans- 
form to  the  reguline  state  all  metallic  oxides  except  the  sesquioxides  of 
aluminium  and  chromium,  and  the  monoxides  of  manganese,  magnesium, 
barium,  strontium,  calcium,  lithium,  sodium,  and  potassium.  The  temper- 
ature necessary  to  enable  hydrogen  to  effect  the  decomposition  of  some 
oxides  is  comparatively  low.  Thus  even  metallic  iron  may  be  reduced 
from  its  oxides  by  hydrogen  gas  at  a  heat  considerably  below  redness,  so 
as  to  form  an  iron  pyrophorus.  Carbon,  at  a  red  or  white  heat,  is  a  still 
more  powerful  deoxidating  agent  than  hydrogen,  and  seems  to  be  capable 
of  completely  reducing  all  metallic  oxides  whatsoever.  The  oxidizable 
metals  in  general  act  as  reducing  agents. 

Chlorine  decomposes  all  metallic  oxides,  except  those  of  the  earth-metals, 
converting  them  into  chlorides,  and  expelling  the  oxygen.  With  silver 
oxide  this  reaction  takes  place  at  ordinary  temperatures;  with  the  alkalies 
and  alkaline  earths,  at  a  full  red  heat,  Sulphur,  at  high  temperatures,  can 
decompose  most  metallic  oxides.  With  many  oxides,  those  of  silver,  mer- 
cury, lead,  and  copper,  for  instance,  metallic  sulphides  and  sulphur  diox- 


280  CHEMISTRY    OF    THE    METALS. 

ide  are  produced.  With  the  highly  basylous  oxides,  the  products  are  me- 
tallic sulphate  and  sulphide.  There  are  some  oxides  upon  which  sulphur 
exerts  no  action.  Of  these  the  principal  are  magnesia,  alumina,  chromic, 
stannic,  and  titanic  oxides.  By  boiling  sulphur  with  soluble  hydrates, 
mixtures  of  polysulphide  and  hyposulphite  are  produced.  "With  the  ex- 
ception of  magnesia,  alumina,  and  chromic  oxide,  most  metallic  oxides  can 
absorb  sulphuretted  hydrogen,  to  form  metallic  sulphide  or  sulph-hydrate, 
and  water. 

Oxygen-salts,  or  Oxysalts.  —  It  has  been  already  explained  in  the  .chapter 
on  Oxygen  (p.  133),  that  oxides  may  be  divided  into  three  classes,  acid,  neu- 
tral, and  basic;  the  first  and  third  being  capable  of  uniting  with  one  another 
in  definite  proportions,  and  forming  compounds  called  salts.  The  most 
characteristic  of  the  acid  oxides  are  those  of  certain  metalloids,  as  nitrogen, 
sulphur,  and  phosphorus,  which  unite  readily  with  water  or  the  elements 
of  water,  forming  compounds  called  oxygen-acids,  distinguished  by  sour 
taste,  solubility  in  water,  and  the  power  of  reddening  certain  vegetable 
blue  colors.  The  most  characteristic  of  the  basic  oxides,  on  the  other 
hand,  are  those  of  the  alkali-metals  and  alkaline  earth-metals  (p.  271), 
which  likewise  dissolve  in  water,  but  form  alkaline  solutions,  possessing  in 
an  eminent  degree  the  power  of  neutralizing  acids  and  forming  salts  with 
them.  The  same  power  is  exhibited  more  or  less  by  the  monoxides  of  most 
other  metals,  as  zinc,  iron,  copper,  manganese,  &c.,  and  by  the  sesquioxides 
of  aluminium,  iron,  chromium,  and  others.  The  higher  oxides  of  several 
of  these  metals  —  the  trioxide  of  chromium,  for  example  —  exhibit  acid 
characters,  being  capable  of  forming  salts  with  the  more  basic  oxides ;  and 
some  metals,  as  arsenic,  antimony,  niobium,  and  tantalum,  form  only  acid 
oxides. 

In  some  cases  salts  are  formed  by  the  direct  combination  of  an  acid  and 
a  basic  oxide.  Thus,  when  vapor  of  sulphuric  oxide,  S03,  is  passed  over 
red-hot  barium  oxide,  BaO,  the  two  combine  together  and  form  barium- 
sulphate,  S03.BaO  or  S04Ba.  Silicic  oxide,  Si02,  phosphoric  oxide,  P205, 
arsenic  oxide,  As205,  boric  oxide,  B203,  and  other  acid  oxides  capable  of 
withstanding  a  high  temperature  without  decomposing  or  volatilizing,  like- 
wise unite  with  basic  oxides  when  heated  with  them,  and  form  salts. 

But  in  the  majority  of  cases  metallic  salts  are  formed  by  substitution  or 
interchange  of  a  metal  for  hydrogen,  or  of  one  metal  for  another.  It  is 
clear,  indeed,  that  any  metallic  salt  (zinc-sulphate,  S03.ZnO,  for  example) 
may  be  derived  from  the  corresponding  acid  or  hydrogen-salt  (S03.H.,0) 
by  substitution  of  a  metal  for  an  equivalent  quantity  of  hydrogen.  Ac- 
cordingly, metallic  salts  are  frequently  produced  by  the  action  of  an  acid 
on  a  metal,  or  a  metallic  oxide  or  hydrate,  thus : 

(1)  S04H2         +         Zn"        =        S04Zn"         +         H2. 

Hydrogen  sulphate.  Zinc  sulphate. 

(2)  2N03H        -f        OAg2       =        2N03Ag         +        OH2 

Hydrogen  nitrate.  Silver  oxide.  Silver  nitrate.  Water. 

(3)  N03H        4-         OKH       =  N03K          -f         OH2 
Hydrogen  nitrate.      Potassium  hydrate.      Potassium  nitrate.  Water. 

In  the  instances  represented  by  these  equations,  the  metallic  salts  formed 
are  soluble  in  water.  Insoluble  salts  are  frequently  prepared  by  inter- 
change of  the  metals  between  two  soluble  salts  ;  thus  : 

(4)  (N08)8Ba"      -f       S04Na2     =       S04Ba"       +      2N03N& 
Barium  nitrate.  Sodium  sulphate.    Barium  sulphate.         Sodium  nitrate. 

In  this  case  the  barium  sulphate,  being  insoluble,  is  precipiated,  while  the 
sodium  nitrate  remains  in  solution. 


OXYGEN-SALTS.  281 

In  all  these  reactions,  hydrochloric  acid,  or  a  metallic  chloride,  might  be 
substituted  for  the  oxygen-acid  or  oxygen-salt  without  the  slightest  altera- 
tion in  the  mode  of  action,  the  product  formed  in  each  case  being  a  chloride 
instead  of  a  nitrate  or  sulpate  ;  thus  : 

(1)'  2HC1  -f  Zn"  =  ZnCL  4-  H 

2)'  2HCI  +  OAg,  «,  2AR('l  +  oil, 

3)'           HC1  -f  OKH  ==  KH  4-  OH 

4)'          N03Ag  -f  NaCl  =  AgCl  N03Na. 

From  all  these  considerations  it  appears  that  oxygen-salts  may  be  re- 
garded, either  as  compounds  of  acid  oxides  with  basic  oxides,  or  as  ana- 
logous in  composition  to  chlorides, — that  is  to  say,  as  compounds  of  a 
motal  with  a  radical  or  group  of  elements,  such  as  N03  (nitrionc)  in  the  ni- 
trates, S04  (sulphione]  in  the  sulphates,  discharging  functions  similar  to 
those  of  chlorine,  and  capable,  like  that  element,  of  passing  unchanged 
from  one  compound  to  another. 

For  many  years,  indeed,  it  was  a  subject  of  discussion  among  chemists 
whether  the  former  or  the  latter  of  these  views  should  be  regarded  as  re- 
presenting the  actual  constitution  of  oxygen-salts.  Bcrzelius  divided  salts 
into  two  classes:  (1).  Haloid  salts,  comprising,  as  already  mentioned,  the 
chlorides,  bromides,  iodides,  and  fluorides,  which  are  compounds  of  a  metal 
with  a  monad  metallic  element.  (2).  Amp  hid  salts,  consisting  of  an  acid  or 
electro-negative  oxide,  sulphide,  selenide,  or  tclluride,  with  a  basic  or 
electro-positive  compound  of  the  same  kind;  such  as  potassium  arscnate, 
P  05.30K2;  potassium  sulpharsenate,  P2S5.3SK2;  potassium  seleniophosphatc 
P2Se5.2SeK2,  &c. 

Davy,  on  the  other  hand,  observing  the  close  analogy  between  the  reac- 
tions of  chlorides,  on  the  one  hand,  and  of  oxygen-salts,  such  as  sulphates, 
nitrates,  &c.,  on  the  other,  suggested  that  the  latter  might  be  regarded, 
like  the  former,  as  compounds  of  metals  with  acid  or  electro-negative  radi- 
cals, the  only  difference  being,  that  in  the  former  the  acid-radical  is  an 
elementary  body,  Cl,  Br,  &c.,  whereas  in  the  former  it  is  a  compound,  as 
S04,  N03.  P04,  &c.  This  was  called  the  binary  theory  of  salts ;  it  was  sup- 
ported by  many  ingenious  arguments  by  its  proposer  and  several  contem- 
porary chemists ;  in  later  years  also  by  Liebig,  and  by  Daniell  and  Miller, 
who  observed  that  the  mode  of  decomposition  of  salts  by  the  electric 
current  is  more  easily  represented  by  this  theory  than  by  the  older  one 
(p.  247). 

At  the  present  day,  the  relative  merits  of  these  two  theories  are  not  re- 
garded as  a  point  of  very  great  Importance.  Chemists,  in  fact,  no  longer 
attempt  to  construct  formula  which  shall  represent  the  actual  arrangements 
of  atoms  in  a  compound,  the  formuloa  now  in  use  being  rather  intended  to 
exhibit,  first,  the  balance  or  neutralization  of  the  units  of  equivalency  or 
atomicity  of  the  several  elements  contained  in  a  compound  (p.  231);  and, 
secondly,  the  manner  in  which  any  compound  or  group  of  atoms  splits  up 
into  subordinate  groups  under  the  influence  of  different  reagents.  Accord- 
ing to  the  latter  view,  a  compound  containing  three  or  more  elementary 
atoms  may  be  represented  by  different  formulae  corresponding  to  the 
several  ways  in  which  it  decomposes.  Thus  hydrogen  sulphate  or  sul- 
phuric acid,  S04H2,  may  be  represented  by  either  of  the  following  formu- 
la: — 

(1.)  S04.H2,  which  represents  the  separation  of  hydrogen  and  formation 
of  a  metallic  sulphate  by  the  action  of  zinc,  &c. :  this  is  the  formula  cor- 
responding to  the  binary  theory  of  salts. 

(2.)    SOS.OH2.     This  formula  represents  the  formation  of  the  acid   by 
direct  hydration  of  sulphuric  oxide  ;  the  separation  of  water  and  formation 
24* 


282  CHEMISTRY  OF  THE  METALS. 

of  a  metallic  sulphate  by  the  action  of  magnesia  and  other  anhydrous 
oxides  ;  and  the  separation  of  sulphuric  oxide  and  formation  of  phosphoric 
acid  by  the  action  of  phosphoric  oxide  : 

S03.OH2   -|-   MgO   =   S03.MgO   -f   OH2 

S08OH2     -f     P2°5      =     P2°5-OH2     +     S°3- 

(3.)  S02.02H2,  or  S02(OH)2.  This  formula  represents  such  reactions  as 
the  elimination  of  hydrogen  dioxide  by  the  action  of  barium  dioxide,  Ba02. 

(4.)  SH2  04.  This  formula  represents  the  formation  of  sulphuric  acid  by 
direct  oxidation  of  hydrogen  sulphide  SH2,  and  the  elimination  of  the  latter 
by  the  action  of  ferrous  sulphide  : 

SH2.04   -f-    FeS   =   S04Fe    -f    SH2. 

Formulae  of  the  third  of  these  types,  like  S02(OH)2,  which  represent 
oxygen-acids  as  compounds  of  hydroxyl  with  certain  acid  radicals,  as  SO./7 
(sulphuryl),  CO"  (carbonyl),  POX//  (phosphoryl),  &c.,  correspond  to  a 
great  variety  of  reactions,  and  are  of  very  frequent  use.  They  exhibit  in 
particular  the  relation  of  the  oxygen-acids  (hydroxylates)  to  the  corres- 
ponding chlorides,  e.  a.  : 

(S02)"(OH)2  (S02)"C12 

Sulphuric  acid.  Sulphuric  chloride. 

(PO)'"(OH)8  (PO)'"C18 

Phosphoric  acid.  Phosphoric  chloride. 

Basicity  of  Acids.  Normal,  Acid  and  Double  Salts. — Acids  are  monobasic, 
bibasic,  tribasic,  &c.,  according  as  they  contain  one  or  more  atoms  of  hydro- 
gen replaceable  by  metals ;  thus  nitric  acid,  N03H,  and  hydrochloric  acid, 
C1H,  are  monobasic ;  sulphuric  acid,  S04H2,  is  bibasic ;  phosphoric  acid, 
P04H3,  is  tribasic. 

Monobasic  acids  form  but  one  class  of  salts  by  substitution,  the  metal 
taking  the  place  of  the  hydrogen  in  one,  two,  or  three  molecules  of  the 
acid,  according  to  its  equivalent  value  or  atomicity;  thus  the  action  of 
hydrochloric  acid  on  sodium,  zinc,  and  aluminum  is  represented  by  the  equa- 
tions : 

C1H  -f  Na  =  CINa  -f  H, 
2C1H  -f-  Zn"  =  Cl2Zn"  4-  H2 
3C1H  4-  Al'"  =  C18A1'"  4-  H3, 

and  that  of  nitric  acid  on  the  hydrates  of  the  same  metals  by  the  equations  : 

N03H  -f  Na  (HO)  =  N03Na  4-  H(HO) 
2N03r!  +  Ba"(HO)2  =  (N03)2Ba"  4-  2H(HO) 
3i\03H  -f  A1'"(HO)8  =  (N03)8A1'"  4-  3H(HO). 

Bibasic  acids,  on  the  other  hand,  form  two  classes  of  salts,  viz.  mono- 
metallic or  acid  salts,  in  which  half  the  hydrogen  is  replaced  by  a  metal; 
and  bimetallic  salts,  in  which  the  whole  of  the  hydrogen  is  thus  replaced, 
the  salt  being  called  normal  or  neutral  if  it  contains  one  metal,  and  double  if 
it  contains  two  metals ;  thus: 


From     S04H2  is  derived  S04KH  {  ^  °*  acid  Potassium 


Jbipotassic  or  normal  potassium 
42  \      sulphate. 

"  "        S04Bax/  barium  sulphate. 

2S04H2  "       (S04)2K3Na  sodio-tripotassic  sulphate. 

"  "       (S04)2A1///K          potassio-aluminic  sulphate. 

3S04H2  "       (S04)3Al///2  normal  aluminium  sulphate. 


BASICITY    OP   ACIDS.  283 

Tribasic  acids  in  like  manner  form  two  classes  of  acid  salts,  mono-metallic 
or  bimetallic,  according  as  one  third  or  two  thirds  of  the  hydrogen  is  replaced 
by  a  metal;  also  normal  and  double  or  triple  sails,  in  which  the  hydrogen  is 
wholly  replaced  by  one  or  more  metals  ;  in  quadribasic  acids  the  variety  ia 
of  course  still  greater. 

The  use  of  the  terminations  ous  and  ic,  as  applied  to  salts,  has  already 
been  explained.  We  have  only  further  to  observe  in  this  place  that  when 
a  metal  forms  but  one  class  of  salts,  it  is  for  the  most  part  better  to  desig- 
nate those  salts  by  the  name  of  the  metal  itself  than  by  an  adjective  ending 
in  ic  ;  thus  potassium  nitrate,  and  lead  sulphate  are  mostly  to  be  preferred  to 
potassic  nitrate  and  plumbic  sulphate  But  in  naming  double  salts,  and  in 
many  cases  where  a  numeral  prefix  is  required,  the  names  ending  in  ic  are 
more  euphonious  ;  thus  triplumbic  phosphate  sounds  better  than  trilead  phos- 
phate, and  hydrodisodic  phosphate  is  certainly  better  than  hydrogen  and  diso- 
dium  phosphate;  but  there  is  no  occasion  for  a  rigid  adherence  to  either 
system. 

All  oxygen-salts  may  also  be  represented  as  compounds  of  an  acid  oxide 
with  one  or  more  molecules  of  the  same  or  different  basic  oxides,  including 
water,  e.  g.  : 

Hydro-potassic  sulphate  2S04KH        =  2S03.K2O.H20 

Sodio-tripotassic  sulphate        2(S04)2KH     =  4S03  3K2O.Nn20 
Potassio-aluminic  sulphate  2(S04)2Al/"K  =  4S03.A1/"203.K20 
Hydrodisodic  phosphate  2PO4Na2H     ==  P205.2Na2O.H20. 

When  a  normal  oxygen-salt  is  thus  formulated,  it  is  easy  to  see  that  the 
number  of  molecules  of  acid  oxide  contained  in  its  molecule  is  equal  to  the 
number  of  oxygen-atoms  in  the  base;  thus: 

Normal  potassium  sulphate     S04K2  =    S03  K20 

"       barium  sulphate          S04Ba  —    S03.BaO 

"       stannic  sulphate        (S04)2Sn"  =  2S03.Sn02 

"       aluminium  sulphate  (S04)3Al'"a  =  3S03  A12O3. 

When  the  proportion  of  acid  oxide  is  less  than  this,  the  salt,  is  called 
basic;  such  salts  may  be  regarded  as  compounds  of  a  normal  salt  with  one 
or  more  molecules  of  basic  oxide,  or  as  derived  from  normal  salts  by  sub- 
stitution of  oxygen  for  an  equivalent  quantity  of  the  acid  radical;  thus: 

Tribasic  lead  nitrate     .     N20s-3pb"°       =  (N03)2Pb".2Pb"0 

=  Pb"3(N03)20"2 


=  (S04),Al"'r8Al'"A 
=  A1"'8(S04)",0",. 

The  last  mode  of  formulation  exhibits  the  analogy  of  these  basic  oxysalts 
to  the  oxychlorides,  oxyodides,  &.c.  ;  thus  the  basic  lead  nitrate,  Pb,(NO$)2Or 
just  mentioned,  is  analogous  to  the  oxychloride  of  that  metal,  Pl>3»'l,<>r 
which  occurs  native  as  mendipite. 

The  term  basic  and  acid  are  sometimes  applied  to  salts  with  reference  to 
their  action  on  vegetable  colors.  The  normal  salts  formed  by  the  union  of 
the  stronger  acids  with  the  alkalies  and  alkaline  earths,  such  as  potassium  sul- 
phate, S04K2,  barium  nitrate,  (N05)2Ba",  &c.,  are  perfectly  neutral  to  vege- 
table colors,  but  most  other  normal  salts  exhibit  either  an  acid  or  an  alka- 
line reaction  ;  thus  ferrous  sulphate,  cupric  sulphate,  silver  nitrate,  and 
many  others  redden  litmus,  while  the  normal  carbonates  and  phosphates  of 
the  alkali-metals  exhibit  a  decided  alkaline  reaction.  It  is  clear  then  that 
the  action  of  a  salt  on  vegetable  colors  bears  no  definite  relation  to  its  composi- 
tion: hence  the  term  normal,  as  applied  to  salts  in  which  the  basic  hydro- 


284 


CHEMISTRY    OF    METALS. 


gen  of  the  acid  is  wholly  replaced,  is  preferable  to  neutral,  and  the  terms 
basic  and  acid,  as  applied  to  salts,  are  best  used  iii  the  manner  above  explained 
with  reference  to  their  composition. 

When  a  normal  salt  containing  a  monoxide  passes  by  oxidation  to  a  salt 
containing  a  sesquioxide,  dioxide,  or  trioxide,  the  quantity  of  acid  present 
is  no  longer  sufficient  to  saturate  the  base.  Thus  when  a  solution  of  fer- 
rous sulphate,  S04Fe,  or  S03.FeO  (common  green  vitriol),  is  exposed  to 
the  air,  it  absorbs  oxygen,  and  an  insoluble  ferric  salt  is  produced  contain- 
ing an  excess  of  base,  while  normal  ferric  sulphate  remains  in  solution : 

4(S03.FeO)    -f-     02    =     3S03.Fe203     -f     S03.Fe203 


Ferrous  sulphate. 


Jformal  ferric 
sulphate. 


Basic  ferric 
sulphate. 


These  basic  salts  are  very  often  insoluble  in  water. 

Salts  containing  a  proportion  of  acid  oxide  larger  than  is  sufficient  to 
form  a  neutral  compound,  are  called  anhydro-salts  (sometimes,  though  im- 
properly, acid  salts)  ;  they  may  evidently  be  regarded  as  compounds  of  a 
normal  salt  with  excess  of  acid  oxide  ;  e.  g.  : 


The  following  is  a  list  of  the  most  important  inorganic  acids  arranged 
according  to  their  basicity  : 

Monobasic  Acids. 

.  Sb03H 
C10H 

.  C102H 
CIO.H 

.  C104H 
Br03H 

.  I03H 
I04H 


Hydochloric 
Hydrobromic  . 
Hydriodic    . 
Hydrofluoric    . 
Nitrous 
Nitric 
Hypophosphorous 
Metaphosphoric 
Boric  . 

.       C1H 
BrH 

m 

FH 
.    N02H 
N03rl 
(PH202)H 
PO,H 
.    BOJI 

Antimonic  . 
Hypochlorous 
Chlorous     . 
Chloric  . 
Perchloric 
Bromic  . 
lodic  . 
Periodic 

Bibasic  Acids. 


Hydric  (water)  . 

Sulph-hydric 

Selenhydric 

Tellurhydric  . 

Sulphurous 

Sulphuric 

Hyposulphurous 

Dithionic 

Trithionic  . 

Tetrathionic  . 

Pentathionic 


Orthophosphoric 
Pyrophosphoric 


OH2 

Selenious 

SH2 

Selenic 

SeH2 

Tellurous 

TeH2 

Telluric 

S03H2 

Manganic 

S04H2 

Permanganic 

S203H2 

Chromic   . 

S206H2 

Stannic 

S306H2 

Metasilicic 

S406H2 

Carbonic 

S506H2 

Phosphorous 

Tribasic  Acids. 
P04H3     |     Arsenic     . 

Tetrabasic  Acids. 
P207H4     |     Orthosilicic 


Se03H2 
Se04H2 


Mn208H2 

.      Cr04H2 

Sn03H2 

.      Si03H2 

C03H2 

(PH03)H2 


.    As04Hs 
Si04H4 


'HOSPHAT] 

The  general  characters  of  most  of  the  non-metallic  acids  and  their  salts 
have  been  already  considered;  but  the  phosphates  require  further  notice. 

PHOSPHATES.  —  There  are  three  modifications  of  phosphoric  acid:  one 
>eirig  monobasic,  the  second  tribasic,  and  the  third  tetrabasic,  as  indicated 
in  the  preceding  table. 

Hydrogen  phosphide,  PII3,  burnt  in  air  or  oxygen  gas,  takes  up  four 
atoms  of  oxygen,  and  forms  trihydric  phosphate  or  tribasic  phosphoric  acii!' 
P04H3.  The  same  acid  is  produced  by  the  oxidation  of  hypophosphorous 
or  phosphorous  acid;  by  oxidizing  phosphorus  with  nitric  acid  (p.  214); 
by  the  decomposition  of  native  calcium  phosphate  (apatite)  and  other  na- 
tive phosphates;  and  by  the  action  of  boiling  water  on  phosphorus  pent- 
oxide,  P205.  This  acid  forms  three  distinct  classes  of  metallic  salts.  With 
sodium,  for  example,  it  forms  the  three  salts,  P04NaH2,  P04Na2H,  and 
PO4Na3,  the  first  two  of  which,  still  containing  replaceable  hydrogen,  are 
acid  salts,  while  the  third  is  the  normal  or  neutral  salt. 

If  now  the  monosodic  phosphate,  P04NaH2,  be  heated  to  redness,  it  gives 
off  one  molecule  of  water,  arid  leaves  an  anhydrous  monosodic  phosphate, 
P03Na,  the  aqueous  solution  of  which,  when  treated  with  lead  nitrate, 
yields  a  lead-salt  of  corresponding  composition;  thus: 

2P03Na  -f  (N03)2Pb"  =  (P(V2Pb"  +  2N03Na; 

and  this  lead-salt  decomposed  by  sulph-hydric  acid,  yields  a  monohydric 
acid  having  the  composition  P03H,  possessing  properties  quite  distinct 
from  those  of  the  trihydric  acid  above  mentioned: 

(P03)2Pb"  +  SH2  =  2P03H  -f  Pb"S. 

The  trihydric  acid  which  is  produced  by  the  oxidation  of  phosphorus, 
and  by  the  decomposition  of  the  ordinary  native  phosphates,  is  called 
orthophosphoric  acid  or  ordinary  phosphoric  acid;  the  monohydric  acid  is 
called  metaphosphoric  acid.  The  former  may  be  regarded  as  a  trihydrate,  the 
latter  as  a  monohydrate  of  phosphoric  oxide : 

2P04IT3  =  P203.30H2,  orthophosphoric  acid, 
2P08H   =  P206.OH2,  metaphosphoric  acid. 

Both  are  soluble  in  water,  and  the  former  may  be  produced  by  the  action 
of  boiling  water,  the  latter  by  that  of  cold  water  on  phosphoric  oxide. 
They  are  easily  distinguished  from  one  another  by  their  reactions  with  al- 
bumin and  with  silver  nitrate.  Metaphosphoric  acid  coagulates  albumin, 
and  gives  a  white  precipitate  with  silver  nitrate;  whereas  orthophosphoric 
acid  does  not  coagulate  albumin,  and  gives  no  precipitate,  or  a  very  slight 
one,  with  silver  nitrate,  till  it  is  neutralized  with  an  alkali,  in  which  case 
a  yellow  precipitate  is  formed. 

Metaphosphoric  acid  and  its  salts  differ  from  orthophosphoric  acid  and 
the  orthophosphates  by  the  want  of  one  or  two  atoms  of  water  or  base ; 
thus: 

Metaphosphates.  Orthophosphates. 

P08H  =     P041I3  OH2 

PO.Na  ==     P04N.-iTI,          —      OH2 

(P08)2Ba"      =    (P04)2Ba"H4    - 

(POS8)2Pb"        ~=    (P04j2P8b"8          •    20Pb". 

Accordingly,  we  find  that  metaphosphates  and  orthophosphates  are  con- 
vertible one  into  the  other  by  the  loss  or  gain  of  one  or  two  atoms  of  water 
or  metallic  base ;  thus : 


286  CHEMISTRY   OF    THE    METALS. 

a.  A  solution  of  metaphosplioric  acid  is  converted,  slowly  at  ordinary 
temperatures,  quickly  at  the  boiling  heat,  into  orthophosphoric  acid,  and 
the  metaphosphates  of  sodium  and  barium  are  converted  by  boiling  with 
water  into  the  corresponding  monometallic  orthophosphates  (see  the  first 
three  equations  above). — /?.  The  metaphosphate  of  a  heavy  metal,  silver 
or  lead,  for  example,  is  converted  by  boiling  with  water  into  a  trimetallic 
phosphate  and  orthophosphoric  acid: 

3P03Ag  +   30H2  =  P04Ag3  -f  2P04H3. 

y.  When  any  metaphosphate  is  fused  with  an  oxide,  hydrate  or  carbonate, 
it  becomes  a  trimetallic  orthophosphate,  e.  g.  • 

P03Na  +  C03Na2  =  P04Na3  -f  C02. 

On  the  other  hand  (6),  when  orthophosphoric  acid  is  heated  to  redness, 
it  loses  water  and  becomes  metaphosplioric  acid ;  and  when  a  monometallic 
orthophosphate  is  heated  to  redness,  it  also  loses  water  and  is  transformed 
into  a  metaphosphate. 

Intermediate  between  orthopTiosphates  and  metaphosphates,  there  are 
at  least  three  distinct  classes  of  salts,  the  most  important  of  which  are  the 
pyrophosphates  or  paraphosphates,  which  may  be  derived  from  the  tetrahydric 
or  quadribasic  acid,  P207H4,  the  normal  sodium  salt,  for  example,  being 
P207Na4,  the  normal  lead  salt,  P^Pb''^,  &c.  These  salts  may  be  viewed 
as  compounds  of  orthophosphate  and  metaphosphate,  e.  g. : 

P207Na4  =  P04Na3  -f  P03Na. 

Sodium  pyrophosphate  is  produced  by  heating  disodic  orthophosphate  to 
redness,  a  molecule  of  water  being  then  given  off: 

2P04Na2H  =,  OH2  -f  P207Na4. 

The  aqueous  solution  of  this  salt  yields  insoluble  pyrophosphates  with 
lead  and  silver  salts;  thus  with  lead  nitrate: 


and  lead  pyrophosphate  decomposed  by  hydrogen  sulphide  yields  hydrogen 
pyrophosphate  or  pyrophosphoric  acid : 

P207Pb"2  -f  2SH2  =  2Pb"S  -f-  P207H4. 

Pyrophosphoric  acid  is  distinguished  from  metaphosphoric  acid  by  not 
coagulating  albumin  and  not  precipitating  neutral  solutions  of  barium  or 
silver  salts,  and  from  orthophosphoric  acid  by  producing  a  white  instead 
of  a  yellow  precipitate  with  silver  nitrate. 

Pyrophosphates  are  easily  converted  into  metaphosphates  and  ortho- 
phosphates,  and  vice  versQ,,  by  addition  or  subtraction  of  water  or  a  metallic 
base. 

a.  The  production  of  a  pyrophosphate  from  an  orthophosphate  by  loss 
of  water  has  been  already  mentioned. — /?.  Conversely,  when  a  pyrophos- 
phate is  heated  with  water  or  a  base,  it  becomes  an  orthophosphate,  e.  g.  : 

P207Na4-f-    H20      =2P04Nn2H 
P207Na4  -|-  20NaH  =  2P04Na3     -f  OH2. 

In  like  manner  orthophosphoric  acid  heated  to  215°  is  almost  entirely  con- 
verted into  pyrophosphoric  acid :  2P04H3  —  OH2  =.  P207H4;  and  conversely, 
when  pyrophosphoric  acid  is  boiled  with  water,  it  is  transformed  into 
orthophosphoric  acid. 

y.  Pyrophosphoric  acid  heated  to  dull  redness  is  converted  into  meta- 
phosphoric acid:  P207H4 — OH2  =2P03H.  The  converse  reaction  is  not 


PHOSPHATES.  287 

sily  effected,  inasmuch  as  motaphosphoric  acid  by  absorbing  water  gener- 
ally passes  directly  to  the  state  of  orthophosphoric  acid.  Peligot,  h<>. \r\rv. 
observed  the  formation  of  pyrophosphoric  from  metaphosphoric  acid  by 
very  slow  absorption  of  water. — f>.  When  a  metallic  rnctaphosph:it<«  is 
treated  with  a  proper  proportion  of  a  hydrate,  oxide,  or  carbonate,  it  is 
converted  into  a  pyrophosphate  ;  thus  : 

2P03Na     -f     C03Na2    =    P20-Na4      4.  C02 

Metaphosphate.         Carbonate.          Pyrophosphate.        Carbon  dioxide. 

Fleitmann  and  Henneberg,*  by  fusing  together  a  molecule  of  sodium  py- 
rophosphate, P04Na3.P03Na,  with  two  molecules  of  metaphosphate,  P()3Na, 
obtained  a  salt  having  the  composition  P04Na3.3P03Na  =  lY),3N.-)6,  which 
is  soluble  without  decomposition  in  a  small  quantity  of  hot  water,  and 
crystallizes  from  its  solution  by  evaporation  over  oil  of  vitriol.  An  excess 
of  hot  water  decomposes  it,  but  its  cold  aqueous  solution  is  moderately  per- 
manent. Insoluble  phosphates  of  similar  composition  may  be  obtained 
from  the  sodium-salt  by  double  decomposition.  Fleitmann  and  Henneberg 
obtained  another  crystallizable  but  very  insoluble  salt,  having  the  compo- 
sition P04Na3.9P03Na  =  Pj003,Na12,  by  fusing  together  one  molecule  of 
sodium-pyrophosphate  with  eight  molecules  of  the  metaphosphate  ;  and  in- 
soluble phosphates  of  similar  constitution  were  obtained  from  it  by  double 
decomposition. 

The  comparative  composition  of  these  different  phosphates  is  best  shown 
by  representing  them  as  compounds  of  phosphoric  oxide  with  metallic  oxide, 
and  assigning  to  them  all,  the  quantity  of  base  contained  in  the  most  com- 
plex member  of  the  series  ;  thus  (for  the  sodium  salts) : 

Orthophosphate 2P205  .  6Na20  =  4P04Na 

Pyrophosphate 3P205  .  6Na20  ==  3P207Na4 

Fleitmann  and  Henneberg's  phosphate  (a)  4P2O5 .  6Na2O  =  2P40,3Na6 

(b)  6P205.6Na,0  =  rio031Xal8 

Metaphosphate 6P206 .  6Na20  =  lliPO3Xa. 

Metallic  Sulphides.  — These  compounds  correspond,  for  the  most  part,  to 
the  oxides  in  composition:  thus  there  are  two  sulphides  of  arsenic,  As.,S3 
and  As2S5,  corresponding  to  the  oxides,  As203  and  As205;  also  two  sulphides 
of  mercury,  Hg2S  and  HgS,  analogous  to  the  oxides,  Hg20  and  HgO.  Oc- 
casionally, however,  we  meet  with  oxides  to  which  there  are  no  correspond- 
ing sulphides  (manganese  dioxide,  for  example),  and  more  frequently  sul- 
phides to  which  there  are  no  corresponding  oxides,  the  most  remarkable  of 
which  are  perhaps  the  alkaline  polysulphides.  Potassium,  for  example, 
forms  the  series  of  sulphides  K2S,  K2S2,  K2S3,  K2S4,  and  K2S5,  the  third  and 
fifth  of  which  have  no  analogues  in  the  oxygen  series. 

There  are  also  sulph-hydrates  analogous  to  the  hydrates,  and  containing 
the  elements  of  a  metallic  sulphide  and  hydrogen  sulphide,  or  sulph-hydric 
acid;  e.  g.  potassium  sulph-hydrate  K2S.H2S  =  2KHS ;  lead  sulph-hydrate 
Pb/xS.H2S  =  Pbx/H2S2.  Sulph-hydrates  and  sulphides  may  be  derived  from 
sulph-hydric  acid  by  partial  or  total  replacement  of  the  hydrogen  by  metals, 
just  as  metallic  hydrates  and  oxides  are  derived  from  water : 

SHH                         SKH  SKK 

Sulph-hydric  Sulph-hydrate  Sulphide, 
acid 

OHH                         OKH  OKK 

Water                      Hydrate  Oxide, 

*  Ann.  Ch.  Pharm.  Ixv.  304. 


288  CHEMISTRY  OF  THE  METALS. 

Many  metallic  sulphides  occur  as  natural  minerals,  especially  the  sulphides 
of  lead,  copper,  and  mercury,  which  afford  valuable  ores  for  the  extraction 
of  the  metals,  and  iron  bisulphide  or  iron  pyrites,  FeS2,  which  is  largely 
used  as  a  source  of  sulphur,  and  for  the  preparation  of  ferrous  sulphate. 

Sulphides  are  formed  artificially  by  heating  metals  with  sulphur  ;  by  the 
action  of  metals  on  gaseous  hydrogen  sulphide ;  by  the  reduction  of  sul- 
phates with  hydrogen  or  charcoal ;  by  heating  metallic  oxides  in  contact 
with  gaseous  hydrogen  sulphide,  or  vapor  of  carbon  bisulphide ;  and  by 
precipitation  of  metallic  solutions  with  hydrogen-  sulphide  or  a  sulphide  of 
alkali-metal.  Some  metals,  as  copper,  lead,  silver,  bismuth,  mercury,  and 
cadmium,  are  precipitated  from  their  acid  solutions  by  hydrogen  sulphide, 
passed  into  them  as  gas  or  added  in  aqueous  solution,  the  sulphides  of  these 
metals  being  insoluble  in  dilute  acids ;  others,  as  iron,  cobalt,  nickel,  man- 
ganese, zinc,  and  uranium,  form  sulphides  which  are  soluble  in  acids,  and 
these  are  precipitated  by  hydrogen  sulphide  only  from  alkaline  solutions, 
or  by  ammonium  or  potassium  sulphide  from  neutral  solutions.  Many  of 
these  sulphides  exhibit  very  characteristic  colors,  which  serve  as  indications 
of  the  presence  of  the  respective  metals  in  solution  (p.  201). 

Metallic  sulphides  are  al^o  formed  by  the  reduction  of  sulphates  with 
organic  substances  ;  many  native  sulphides  have  doubtless  been  formed  in 
this  way. 

The  physical  characters  of  some  metallic  sulphides  closely  resemble  those 
of  the  metals  in  certain  particulars,  such  as  the  peculiar  opacity,  lustre, 
and  density,  especially  when  they  are  in  a  crystalline  condition.  They  are 
generally  crystallizable,  brittle,  and  of  a  gray,  pale  yellow,  or  dark  brown 
color.  The  sulphides  of  the  alkali-metals  are  soluble  in  water,  most  of 
the  others  are  insoluble.  They  are  frequently  more  fusible  than  the  cor- 
responding oxides,  and  some  are  volatilizable,  as  mercury  sulphide  and  ar- 
senic sulphide. 

Many  sulphides,  when  heated  out  of  contact  with  atmospheric  air,  do  not 
undergo  any  decomposition;  this  is  the  case  chiefly  with  those  containing 
the  smallest  proportions  of  sulphur,  such  as  the  monosulphides  of  iron  and 
zinc.  Sulphides  containing  larger  proportions  of  sulphur  are  partially  de- 
composed by  heat,  losing  part  of  their  sulphur,  and  being  converted  into 
lower  sulphides  ;  as  in  the  case  of  iron  bisulphide.  The  sulphides  of  gold 
and  platinum  are  completely  reduced  by  heat. 

By  the  simultaneous  action  of  heat  and  of  substances  capable  of  combin- 
ing with  sulphur,  some  sulphides  may  be  decomposed.  Thus,  for  instance, 
silver,  copper,  bismuth,  tin,  and  antimony  sulphides  are  reduced  by  hydro- 
gen ;  copper,  lead,  mercury,  and  antimony  sulphides  are  reduced  by  heat- 
ing with  iron. 

Sulphides  which  are  not  reduced  by  heat  alone,  are  always  decomposed 
when  heated  in  contact  with  oxygen  or  atmospheric  air.  Those  of  the 
alkali-metals  and  earth-metals  are  converted  into  sulphates  by  this  means. 
Zinc,  iron,  manganese,  copper,  lead,  and  bismuth  sulphides  are  converted 
into  oxides,  and  sulphurous  oxide  is  produced  ;  but  when  the  temperature 
is  not  above  dull  redness,  some  sulphate  is  formed  by  direct  oxidation. 
Mercury  and  silver  sulphides  are  completely  reduced  to  the  metallic  state. 
Some  native  sulphides  gradually  undergo  alteration  by  mere  exposure  to 
the  atmosphere;  but  it  is  then  generally  limited  to  the  production  of  sul- 
phates, unless  the  oxidation  takes  place  so  rapidly  that  the  heat  generated 
is  sufficient  to  decompose  the  sulphate  first  produced.  In  the  production 
of  some  metals  for  use  in  the  arts,  the  separation  of  sulphur  from  the  na- 
tive minerals  is  effected  chiefly  by  means  of  this  action  in  the  operation  of 
roasting. 

Metallic  sulphides  are  decomposed  in  like  manner  when  heated  with 
metallic  oxides  in  suitable  proportions,  yielding  sulphurous  oxide  and  the 


SELENIDES   AND    TELLURIDES.  289 

metal  of  both  the  sulphide  and  oxide.     Lead  is  reduced  from  the  native 
sulphide  in  this  manner. 

Many  metallic  sulphides  are  decomposed  by  acids  in  the  presence  of 
water,  sulphuretted  hydrogen  being  evolved  while  the  metal  enters  into 
combination  with  the  acid  or  chlorous  radical  of  the  acid.  Nitric  acid  when 
concentrated  decomposes  most  sulphides,  with  formation  of  metallic  oxide, 
sulphuric  acid,  sulphur,  and  a  lower  oxide  of  nitrogen.  Nitromuriatic  acid 
acts  in  a  similar  manner,  but  still  more  energetically. 

SULPHUR-SALTS. — The  sulphides  of  the  more  basylous  metals  unite  with 
those  of  the  more  chlorous  or  electro-negative  metals,  and  of  the  metalloids, 
forming  sulphur-salts,  analogous  in  composition  to  the  oxygen-salts,  e.g.: 

Carbonate  C03K2  —  C02.K20 

Sulphocarbonate  CS3K2  =  CS2.K2S 

Arsenate  2As04K3  =  As205.3K20 

Sulpharsenate  2AsS4K3  =  As2S5.3K2S 

Selenides  and  Tellurides.  —  These  compounds  are  analogous  in  composi- 
tion, and  in  many  of  their  properties,  to  the  sulphides,  and  likewise  unite 
one  with  the  other,  forming  selenium-salts  and  tellurium  salts  analogous  to 
the  oxygen  and  sulphur  salts. 

Metals  also  form  definite  compounds  with  nitrogen,  phosphorus,  silicon, 
boron,  and  carbon ;  but  these  compounds  are  comparatively  unimportant, 
excepting  the  carbonides  of  iron,  which  form  cast  iron  and  steel. 
25 


CLASS  L  —  MONAD  METALS. 
GROUP  L  — METALS  OF    THE   ALKALIES. 

POTASSIUM. 

Atomic  weight,  39-1.     Symbol,  K  (Kalium). 

T)OTASSIUM  was  discovered  in  1807  by  Sir  H.  Davy,  who  obtained  it  in 
very  small  quantity  by  exposing  a  piece  of  moistened  potassium  hydrate 
to  the  action  of  a  powerful  voltaic  battery,  the  alkali  being  placed  between 
a  pair  of  platinum  plates  connected  with  the  apparatus.  Processes  have 
since  been  devised  for  obtaining  this  metal  in  almost  any  quantity  that  can 
be  desired. 

An  intimate  mixture  of  potassium  carbonate  and  charcoal  is  prepared  by 
calcining,  in  a  covered  iron  pot,  the  crude  tartar  of  commerce ;  when  cold 
it  is  rubbed  to  powder,  mixed  with  one  tenth  part  of  charcoal  in  small 
lumps,  and  quickly  transferred  to  a  retort  of  stout  hammered  iron  :  the  lat- 
ter may  be  one  of  the  iron  bottles  in  which  mercury  is  imported.  The  retort 
is  introduced  into  a  furnace  a  (fig.  162),  and  placed  horizontally  on  supports 
of  fire-brick, /", /*.  A  wrought-iron  tube  d,  four  inches  long,  serves  to  con- 
vey the  vapors  of  potassium  into  a  receiver  e,  formed  of  two  pieces  of 
wrought-iron,  a,  b  (fig.  163),  which  are  fitted  closely  to  each  other  so  as  to 
form  a  shallow  box  only  a  quarter  of  an  inch  deep,  and  are  kept  together 
by  clamp-screws.  The  iron  plate  should  be  one  sixth  of  an  inch  thick, 
twelve  inches  long,  and  five  inches  wide.  The  receiver  is  open  at  both 
ends,  the  socket  fitting  upon  the  neck  of  the  iron  bottle.  The  object  of 
giving  the  receiver  this  flattened  form  is  to  ensure  the  rapid  cooling  of  the 
potassium,  and  thus  to  withdraw  it  from  the  action  of  the  carbon  monoxide, 
which  is  disengaged  during  the  entire  process,  and  has  a  strong  tendency 
to  unite  with  the  potassium,  forming  a  dangerously  explosive  compound. 
Before  connecting  the  receiver  with  the  tube  d,  the  fire  is  slowly  raised  till  the 
iron  bottle  attains  a  dull  red  heat.  Powdered  vitrefied  borax  is  then  sprin- 
kled upon  it,  which  melts  and  forms  a  coating,  serving  to  protect  the  iron 
from  oxidation.  The  heat  is  then  to  be  urged  until  it  is  very  intense,  care 
being  taken  to  raise  it  as  equally  as  possible  throughout  every  part  of  the 
furnace.  When  a  full  reddish-white  heat  is  attained,  vapors  of  potassium 
begin  to  appear  and  burn  with  a  bright  flame.  The  receiver  is  then  adjusted 
to  the  end  of  the  tube,  which  must  not  project  more  than  a  quarter  of  an 
inch  through  the  iron  plate  forming  the  front  wall  of  the  furnace;  other- 
wise the  tube  is  liable  to  be  obstructed  by  the  accumulation  of  solid  potas- 
sium, or  of  the  explosive  compound  above  mentioned.  Should  any  obstruc- 
tion occur,  it  must  be  removed  by  thrusting  in  an  iron  bar,  and  if  this  fail, 
the  fire  must  be  immediately  withdrawn  by  removing  the  bars  from  the  fur- 
nace, with  the  exception  of  two  which  support,  the  iron  bottle.  The  receiver 
is  kept  cool  by  the  application  of  a  wet  cloth  to  its  outside.  When  the  oper- 
ation is  complete,  the  receiver  with  the  potassium  is  removed  and  immedi- 

290 


POTASSIUM. 


291 


ately  plunged  into  a  vessel  of  rectified  Persian  naphtha  provided  with  a 
cover,  and  kept  cool  by  immersion  in  water.  When  the  apparatus  is  suffi- 
ciently cooled,  the  potassium  is  detached  and  preserved  under  naphtha. 


If  the  potassium  be  wanted  absolutely  pure,  it  must  be  afterwards  re- 
distilled in  an  iron  retort,  into  which  some  naphtha  has  been  put,  that  its 
vapor  may  expel  the  air,  and  prevent  oxidation  of  the  metal. 

Potassium  is  a  brilliant  white  metal,  with  a  high  degree  of  lustre ;  at  the 
common  temperature  of  the  air  it  is  soft,  and  may  be  easily  cut  with  a 
knife,  but  at  0°  it  is  brittle  and  crystalline.  It  melts  completely  at  (5li-o°, 
and  distils  at  a  low  red  heat.  It  floats  on  water,  its  specific  gravity  being 
only  0-865. 

Exposed  to  the  air,  potassium  oxidizes  instantly,  a  tarnish  covering  the 
surface  of  the  metal,  which  quickly  thickens  to  a  crust  of  caustic  potash. 
Thrown  upon  water,  it  takes  fire  spontaneously,  and  burns  with  a  beautiful 
purple  flame,  yielding  an  alkaline  solution.  When  it  is  brought  into  con- 
tact with  a  little  water  in  a  jar  standing  over  mercury,  the  liquid  is  decom- 
posed with  great  energy,  and  hydrogen  liberated.  Potassium  is  always 
preserved  under  the  surface  of  naphtha. 

POTASSIUM  CHLORIDE,  KC1.  —  This  salt  is  obtained  in  large  quantity  in 
the  manufacture  of  the  chlorate :  it  is  easily  purified  from  any  portions  of 
the  latter  by  exposure  to  a  dull  red  heat.  Within  the  last  few  years  large 
quantities  of  this  salt  have  been  obtained  from  sea-water,  by  a  peculiar 
process  suggested  by  M.  Balard.*  It  is  also  contained  in  kelp,  and  is  sep- 
arated for  the  use  of  the  alum-maker.  Considerable  quantities  of  it  are 
now  obtained  from  the  salt-beds  of  Strassfurt,  near  Magdeburg,  in  Prussia. 

Potassium  chloride  closely  resembles  common  salt  in  appearance,  assum- 
ing, like  that  substance,  the  cubic  form  of  crystallization.  The  crys- 
tals dissolve  in  three  parts  of  cold,  and  in  a  much  smaller  quantity  of  boil- 
ing water:  they  are  anhydrous,  have  a  simple  saline  taste,  with  slight  bit- 
terness, and  fuse  when  exposed  to  a  red  heat.  Potassium  chloride  is 
volatilized  by  a  very  high  temperature. 

POTASSIUM  IODIDE,  KI.  —  There  are  three  different  methods  of  preparing 
this  important  medicinal  compound. 

(1.)  When  iodine  is  added  to  a  strong  solution  of  caustic  potash  free  from 
carbonate,  it  is  dissolved  in  large  quantity,  forming  a  colorless  solution 
containing  potassium  iodide  and  iodate ;  the  reaction  is  the  same  as  in  the 

*  Reports  by  the  Juries  of  the  International  Exhibition  of  1862,  Claas  n. 


292  MONAD    METALS. 

analogous  case  with  chlorine.  When  the  solution  begins  to  be  permanently 
colored  by  the  iodine,  it  is  evaporated  to  dryness,  and  cautiously  heated  to 
redness,  by  which  the  iodate  is  entirely  converted  into  potassium  iodide. 
The  mass  is  then  dissolved  in  water,  and,  after  nitration,  made  to  crys- 
tallize. 

(2.)  Iodine,  water,  and  iron  filings  or  scraps  of  zinc,  are  placed  in  a 
warm  situation  until  the  combination  is  complete,  and  the  solution  colorless. 
The  resulting  iodide  of  iron  or  zinc  is  then  filtered,  and  exactly  decomposed 
with  solution  of  pure  potassium  carbonate,  great  care  being  taken  to  avoid 
excess  of  the  latter.  Potassium  iodide  and  ferrous  carbonate,  or  zinc  car- 
bonate, are  thus  obtained:  the  former  is  separated  by  filtration,  and  evap- 
orated until  the  solution  is  sufficiently  concentrated  to  crystallize  on  cooling, 
the  washings  of  the  filter  being  added  to  avoid  loss: 

FeI2     -f     C03K2     =     2KI     +'   C03Fe". 

(3.)  A  very  simple  method  for  the  preparation  of  potassium  iodide  has 
recently  been  proposed  by  Liebig.  One  part  of  amorphous  phosphorus  is 
added  to  40  parts  of  warm  water ;  20  parts  of  dry  iodine  are  then  gradu- 
ally added  and  intimately  mixed  with  the  phosphorus  by  trituration.  The 
dark-brown  liquid  thus  obtained  is  now  heated  on  the  water-bath  until  it 
becomes  colorless;  it  is  then  poured  off  from  the  undissolved  phosphorus 
and  neutralized,  first  with  barium  carbonate  and  then  with  baryta  water, 
until  it  becomes  slightly  alkaline.  The  insoluble  barium  phosphate  is  fil- 
tered off  and  washed ;  the  filtrate  now  contains  nothing  but  barium  iodide, 
which,  when  treated  with  potassium  sulphate,  yields  insoluble  barium  sul- 
phate and  potassium  iodide  in  solution.  Lime  answers  nearly  as  well  as 
baryta. 

Potassium  iodide  crystallizes  in  cubes,  which  are  often,  from  some  unex- 
plained cause,  milk-white  and  opaque :  they  are  anhydrous,  and  fuse  rea- 
dily when  heated.  The  salt  is  very  soluble  in  water,  but  not  deliquescent, 
when  pure,  in  a  moderately  dry  atmosphere:  it  is  dissolved  by  alcohol. 

Solution  of  potassium  iodide,  like  those  of  all  the  soluble  iodides,  dis- 
solves a  large  quantity  of  free  iodine,  forming  a  deep-brown  liquid,  not 
decomposed  by  water. 

POTASSIUM  BROMIDE,  KBr. — This  compound  maybe  obtained  by  pro- 
cesses exactly  similar  to  those  just  described,  substituting  bromine  for  the 
iodine.  It  is  a  colorless  and  very  soluble  salt,  quite  undistinguishable  in 
appearance  and  general  characters  from  the  iodide. 

POTASSIUM  OXIDES.  — Potassium  combines  with  oxygen  in  three  propor- 
tions, forming  a  monoxide,  OK2,  a  dioxide,  02K2,  and  a  tetroxide,  04K2, 
besides  a  hydrate,  OKH,  corresponding  to  the  monoxide. 

Potassium  monoxide,  OK2,  also  called  anhydrous  potash,  or  potassa,  is  formed 
when  potassium  in  thin  slices  is  exposed  at  ordinary  temperatures  to  dry 
air  free  from  carbon  dioxide ;  also  when  the  hydrate  is  heated  with  an 
equivalent  quantity  of  metallic  potassium: 

20KH     -f     K2    =     20K2     +     H2. 

It  is  white,  very  deliquescent  and  caustic,  combines  energetically  with 
water,  forming  potassium  hydrate,  and  becoming  incandescent  when  moist- 
ened with  it ;  melts  at  a  red  heat,  and  volatilizes  at  very  high  temperatures. 

OK 
The  dioxide  02K2  or    I     is  formed  at  a  certain  stage   in  the  preparation 

OK 

of  the  tetroxide,  but  has  not  been  obtained  quite  pure.  By  carefully  reg- 
ulating the  heat  and  supply  of  air,  nearly  the  whole  of*  the  potassium 


POTASSIUM.  293 

may  be  converted  into  a  white  oxide,  having  nearly  the  composition  of  tin- 
dioxide.  An  aqueous  solution  of  this  oxide  is  formed  by  the  action  of 

0— 0— K 
water  on  the  tetroxide.     The  tetroxide,  04K2,  or   I  ,  is  produced  when 

0— 0— K 

potassium  is  burnt  in  excess  of  dry  air  or  oxygen  gas.  It  is  a  chrome- 
yellow  powder,  which  cakes  together  at  about  280°.  It  absorbs  moisture 
rapidly,  and  is  decomposed  by  water,  giving  off  oxygen  and  forming  a 
solution  of  the  dioxide.  When  gently  heated  in  a  stream  of  carbon  mon- 
oxide, it  yields  potassium  carbonate  and  two  atoms  of  oxygen : 

04K2     +     CO     ==     C03K2     +     02: 

with  carbon  dioxide  it  acts  in  a  similar  manner,  giving  off  three  atoms  of 
oxygen.* 

POTASSIUM  HYDRATE,  OKH,  commonly  called  caustic  potash,  or  potassa,  is 
a  very  important  substance,  and  one  of  great  practical  utility.  It  is  al- 
ways prepared  for  use  by  decomposing  the  carbonate  with  calcium  hydrate 
(slaked  lime),  as  in  the  following  process,  which  is  very  convenient:  10 
parts  of  potassium  carbonate  are  dissolved  in  100  parts  of  water,  and 
heated  to  ebullition  in  a  clean  untinned  iron,  or,  still  better,  silver  vessel; 
8  parts  of  good  quicklime  are  meanwhile  slaked  in  a  covered  basin,  and 
the  resulting  calcium  hydrate  added,  little  by  little,  to  the  boiling  solution 
of  carbonate,  with  frequent  stirring.  When  all  the  lime  has  been  intro- 
duced, the  mixture  is  suffered  to  boil  for  a  few  minutes,  and  then  removed 
from  the  fire  and  covered  up.  In  the  course  of  a  very  short  time,  the  so- 
lution will  have  become  quite  clear,  and  fit  for  decantation,  the  calcium 
carbonate,  with  the  excess  of  hydrate,  settling  down  as  a  heavy,  sandy 
precipitate.  The  solution  should  not  effervesce  with  acids. 

It  is  essential  in  this  process  that  the  solution  of  potassium  carbonate  be 
dilute,  otherwise  the  decomposition  becomes  imperfect.  The  proportion  of 
lime  recommended  is  much  greater  than  that  required  by  theory,  but  it  is 
always  proper  to  have  an  excess. 

The  solution  of  potassium  hydrate  may  be  concentrated  by  quick  evap- 
oration in  the  iron  or  silver  vessel  to  any  desired  extent;  when  heated 
until  vapor  of  water  ceases  to  be  disengaged,  and  then  suffered  to  cool,  it 
furnishes  the  solid  hydrate,  OKH,  or  OK.2.OHr 

Pure  potassium  hydrate  is  also  easily  obtained  by  heating  to  redness  for 
half  an  hour  in  a  covered  copper  vessel,  one  part  of  pure  powdered  nitre 
with  two  or  three  parts  of  finely  divided  copper  foil.  The  mass,  when 
cold,  is  treated  with  water. 

Potassium  hydrate  is  a  white  solid  substance,  very  deliquescent  and  sol- 
uble in  water ;  alcohol  also  dissolves  it  freely,  which  is  the  case  with  com- 
paratively few  potassium  compounds :  the  solid  hydrate  of  commerce,  which 
is  very  impure,  may  thus  be  purified.  The  solution  of  this  substance  pos- 
sesses, in  the  very  highest  degree,  the  properties  termed  alkaline :  it  re- 
stores the  blue  color  to  litmus  which  has  been  reddened  by  an  acid;  neu- 
tralizes completely  the  most  powerful  acids;  has  a  nauseous  and  peculiar 
taste;  and  dissolves  the  skin,  and  many  other  organic  matters,  when  the 
latter  are  subjected  to  its  action.  It  is  frequently  used  by  surgeons  as  a 
cautery,  being  moulded  into  little  sticks  for  that  purpose. 

Potassium  hydrate,  both  in  the  solid  state  and  in  solution,  rapidly  absorbs 
carbonic  acid  from  the  air ;  hence  it  must  be  kept  in  closely  stopped  bot- 
tles. When  imperfectly  prepared,  or  partially  altered  by  exposure,  it 
effervesces  with  an  acid. 

*  Ilarcourt,  Clicni  Soc.  Journ.  xiv.  267. 


294 


MONAD    METALS. 


This  compound  is  not  decomposed  by  heat,  but  volatilizes  undecomposed 
at  a  very  high  temperature. 

The  following  table  of  the  densities  and  value  in  anhydrous  potassium 
oxide,  OK2,  of  different  solutions  of  potassium  hydrate,  is  given  on  the 
authority  of  Dalton: 


Density. 
1-68 
1-60 
1-52 
1-47 
1-44 
1-42 
1-39 
1-36 


Percentage  of 

OK2. 
.  51-2 

46-7 
.  42-9 

39-6 
.  36-8 

34-4 
.  32-4 

29-4 


Density. 
•33 
•28 
•23 
•19 
•15 
•11 
1-06 


Percentage  of 
OK2. 

.    2G-3 

23-4 
.  19-5 

16-2 

.    13-0 

9-5 

.      4-7 


POTASSIUM  NITRATE;  NITRE;  SALTPETRE,  N03K  —  N02(OK).  —  This  im- 
portant compound  is  a  natural  product,  being  disengaged  by  a  kind  of 
efflorescence  from  the  surface  of  the  soil  in  certain  dry  and  hot  countries. 
It  may  also  be  produced  by  artificial  means — namely,  by  the  oxidation  of 
ammonia  in  presence  of  a  powerful  base. 

In  France,  large  quantities  of  artificial  nitre  are  prepared  by  mixing 
animal  refuse  of  all  kinds  with  old  mortar  or  calcium  hydrate  and  earth. 
and  placing  the  mixture  in  heaps,  protected  from  the  rain  by  a  roof,  but 
freely  exposed  to  the  air.  From  time  to  time  the  heaps  are  watered  with 
putrid  urine,  and  the  mass  turned  over,  to  expose  fresh  surfaces  to  the  air. 
"When  much  salt  has  been  formed,  the  mixture  is  lixiviated,  and  the  solution, 
which  contains  calcium  nitrate,  is  mixed  with  potassium  carbonate  ;  calcium 
carbonate  is  formed,  and  the  nitric  acid  transferred  to  the  alkali.  The  fil- 
tered solution  is  then  made  to  crystallize,  and  the  crystals  are  purified  by 
re-solution  and  crystallization,  the  liquid  being  stirred  to  prevent  the  for- 
mation of  large  crystals. 

The  greater  part  of  the  nitre  used  in  this  country  comes  from  the  East 
Indies:  it  is  dissolved  in  water,  a  little  potassium  carbonate  added  to  pre- 
cipitate lime,  and  then  the  salt  purified  as  above. 

Considerable  quantities  of  nitre  are  now  manufactured  by  decomposing 
native  sodium  nitrate  (Chile  saltpetre),  with  carbonate  or  chloride  of  po- 
tassium. In  Belgium  the  potassium  carbonate  obtained  from  the  ashes  of 
the  beetroot  sugar  manufactories  is  largely  used  for  this  purpose;  the  po- 
tassium nitrate  thus  prepared  is  very  pure,  and  is  produced  at  a  low  price. 

Potassium  nitrate  crystallizes  in  anhydrous  six-sided  prisms,  with  di- 
hedral summits,  belonging  to  the  rhombic  or  trimetric  system:  it  is  soluble 
in  7  parts  of  water  at  15-5°,  and  in  its  own  weight  of  boiling  water.  Its 
taste  is  saline  and  cooling,  and  it  is  without  action  on  vegetable  colors.  At 
a  temperature  below  redness  it  melts,  and  by  a  strong  heat  is  completely 
decomposed. 

When  it  is  thrown  on  the  surface  of  many  metals  in  a  state  of  fusion,  or 
when  mixed  with  combustible  matter  and  heated,  rapid  oxidation  ensues, 
at  the  expense  of  the  oxygen  of  the  nitric  acid.  Examples  of  such  mixtures 
are  found  in  common  gunpowder,  and  in  nearly  all  pyrotechnic  compositions, 
which  burn  in  this  manner  independently  of  the  oxygen  of  the  air,  and 
even  under  water.  Gunpowder  is  made  by  very  intimately  mixing  together 
potassium  nitrate,  charcoal,  and  sulphur,  in  proportions  which  approach 
2  molecules  of  nitre,  3  atoms  of  carbon,  and  1  atom  of  sulphur. 

These  quantities  give,  reckoned  to  100  parts,  and  compared  with  the 
proportions  used  in  the  manufacture  of  the  English  Government  powder,* 
the  following  results : 

*  Dr.  M'Culloch,  Encyclopedia  Britaunica. 


POTASSIUM.  295 

Theory.  Proportions 

in  practice. 

Potassium  nitrate          .         74-8        .         75 
Charcoal  .         .         .     13  3     .         .15 

Sulphur        .         .         .         11-9        .         10 

100-0  100 

The  nitre  is  rendered  very  pure  by  the  means  already  mentioned,  freed 
from  water  by  fusion,  and  ground  to  fine  powder;  the  sulphur  and  char- 
coal, the  latter  being  made  from  light  wood,  as  dogwood  or  alder,  are  also 
finely  ground,  after  which  the  materials  are  weighed  out,  moistened  with 
water,  and  thoroughly  mixed  by  grinding  under  an  edge-mill.  The  mass 
is  then  subjected  to  great  pressure,  and  the  rnillcake  thus  produced  broken 
in  pieces,  and  placed  in  sieves  made  of  perforated  vellum,  moved  by 
machinery,  each  containing,  in  addition,  a  round  piece  of  heavy  wood. 
The  grains  of  powder  broken  off  by  attrition  fall  through  the  holes  in  the 
skin,  and  are  easily  separated  from  the  dust  by  sifting.  The  powder  is, 
lastly,  dried  by  exposure  to  steam-heat,  and  sometimes  glazed  or  polished 
by  agitation  in  a  kind  of  cask  mounted  on  an  axis. 

It  was  formerly  supposed  that  when  gunpowder  is  fired,  the  whole  of  the 
oxygen  of  the  potassium  nitrate  was  transferred  to  the  carbon,  forming 
carbon  dioxide,  the  sulphur  combining  with  the  potassium,  and  the  nitrogen 
being  set  free.  There  is  no  doubt  that  this  reaction  docs  take  place  to  a 
considerable  extent,  and  that  the  large  volume  of  gas  thus  produced,  and 
still  further  expanded  by  the  very  exalted  temperature,  sufficiently  accounts 
for  the  explosive  effects.  But  recent  investigations  by  Bunsen,  Karolyi, 
and  others,  have  shown  that  the  actual  products  of  the  combustion  of  gun- 
powder are  much  more  complicated  than  this  theory  would  indicate,  a  very 
large  number  of  products  being  formed,  and  a  considerable  portion  of  the 
oxygen  being  transferred  to  the  potassium  sulphide,  converting  it  into  sul- 
phate, which,  in  fact,  constitutes  the  chief  portion  of  the  solid  residue  and 
of  the  smoke  formed  by  the  explosion.* 

POTASSIUM  CHLORATE,  C103K  =  C102(OK).  —  The  theory  of  the  produc- 
tion of  chloric  acid,  by  the  action  of  chlorine  gas  on  a  solution  of  caustic 
potassa,  has  been  already  explained  (p.  187). 

Chlorine  gas  is  conducted  by  a  wide  tube  into  a  strong  and  warm  solu- 
tion of  potassium  carbonate,  until  absorption  of  the  gas  ceases;  and  the 
liquid  is,  if  necessary,  evaporated,  and  then  allowed  to  cool,  in  order  that 
the  slightly  soluble  chlorate  may  crystallize  out.  The  mother-liquor  affords 
a  second  crop  of  crystals,  but  they  are  much  more  contaminated  by  potas- 
sium chlorido.  It  may  be  purified  by  one  or  two  re-crystalli/ations. 

Potassium  chlorate  is  soluble  in  about.  20  parts  of  cold  and  2  of  boiling 
water:  the  crystals  are  anhydrous,  flat,  and  tabular;  in  taste  it  somewhat 
resembles  nitre.  When  heated,  it  gives  off  the  whole  of  its  oxygen  jras 
and  leaves  potassium  chloride.  By  arresting  the  decomposition  when  the 
evolution  of  gas  begins  to  slacken,  and  redissolving  the  salt,  potassium  per- 
chlorate  and  chloride  may  be  obtained. 

This  salt  deflagrates  violently  with  combustible  matter,  explosion  often 
occurring  by  friction  or  blows.  When  about,  one  grain-weight  of  chlorate 
and  an  equal  quantity  of  sulphur  are  rubbed  in  a  mortar,  the  mixture  ex- 
plodes with  a  loud  report:  hence  it  cannot  be  used  in  the  preparation  of 
gunpowder  instead  of  the  nitrate.  Potassium  chlorate  is  now  a  large  article 
of  commerce,  being  employed,  together  with  phosphorus,  in  making  instan- 
taneous-light matches. 

POTASSIUM  PERCHLOBATB,  C104K  =  C103(OK).— This  salt  has  been  already 

*  See  Watts's  Dictionary  of  Chemistry,  vol.  ii.  p.  958. 


296  MONAD    METALS. 

policed  under  the  head  of  perchloric  acid.  It  is  best  prepared  by  project- 
ing powdered  potassium  chlorate  into  warm  nitric  acid,  when  the  chlo- 
ric acid  is  resolved  into  perchloric  acid,  chlorine  and  oxygen  gases.  The 
salt  is  separated  by  crystallization  from  the  nitrate.  Potassium  perchlorate 
is  a  very  slightly  soluble  salt :  it  requires  55  parts  of  cold  water,  but  is 
more  freely  taken  up  at  a  boiling  heat.  The  crystals  are  small,  and  have 
the  figure  of  an  octohedron  with  square  base.  It  is  decomposed  by  heat,  in 
the  same  manner  as  the  chlorate. 

POTASSIUM  CARBONATES. — Potassium  forms  two  well-defined  carbonates, 
namely,  a  normal  or  neutral  carbonate,  C03K2,  and  an  acid  salt  containing 
C03KH. 

Normal  potassium  carbonate,  or  dipotassic  carbonate  =  CO(OK)2  =  C02.OK2. 
Potassium-salts  of  vegetable  acids  are  of  constant  occurrence  in  plants, 
where  they  perform  important,  but  not  yet  perfectly  iinderstood  functions 
in  the  economy  of  those  beings.  The  potassium  is  derived  from  the  soil, 
which,  when  capable  of  supporting  vegetable  life,  always  contains  that  sub- 
stance. When  plants  are  burned,  the  organic  acids  are  destroyed,  and  the 
potassium  is  left  in  the  state  of  carbonate. 

It  is  by  these  indirect  means  that  the  carbonate,  and,  in  fact,  nearly  all 
the  salts  of  potassium,  are  obtained.  The  great  natural  depository  of  the 
alkali  is  the  felspar  of  granitic  and  other  unstratified  rocks,  where  it  is 
combined  with  silica,  and  in  an  insoluble  state.  The  extraction  thence  is 
attended  with  great  difficulties,  and  many  attempts  at  manufacturing  it  on 
a  large  scale  from  this  source  have  failed ;  but  experiments  quite  recently 
made  by  Mr.  T.  0.  Ward  appear  to  indicate  that  the  object  may  be  accom- 
plished by  fusing  potassic  rocks  with  a  mixture  of  calcium  carbonate  and 
fluoride.  There  are,  however,  natural  processes  at  work,  by  which  the 
potash  is  constantly  being  eliminated  from  these  rocks.  Under  the  influ- 
ence of  atmospheric  agencies,  these  rocks  disintegrate  into  soils,  and  as  the 
alkali  acquires  solubility,  it  is  gradually  taken  up  by  plants,  and  accumu- 
lates in  their  substance  in  a  condition  highly  favorable  to  its  subsequent 
applications. 

Potassium-salts  are  always  most  abundant  in  the  green  and  tender  parts 
of  plants,  as  may  be  expected,  since  from  these,  evaporation  of  nearly  pure 
water  takes  place  to  a  large  extent :  the  solid  timber  of  forest-trees  contains 
comparatively  little. 

In  preparing  the  salt  on  an  extensive  scale,  the  ashes  are  subjected  to  a 
process  called  lixiviation:  they  are  put  into  a  large  cask  or  tun,  having  an 
aperture  near  the  bottom,  stopped  by  a  plug,  and  a  quantity  of  water  is 
added.  After  some  hours  the  liquor  is  drawn  off",  and  more  water  added, 
that  the  whole  of  the  soluble  matter  may  be  removed.  The  weakest  solu- 
tions are  poured  upon  fresh  quantities  of  ash,  in  place  of  water.  The  solu- 
tions are  then  evaporated  to  dryness,  and  the  residue  calcined,  to  remove  a 
little  brown  organic  matter :  the  product  is  the  crude  potash  or  pearlash 
of  commerce,  of  which  very  large  quantities  are  obtained  from  Russia  and 
America.  This  salt  is  very  impure  :  it  contains  potassium  silicate,  sulphate, 
chloride,  &c. 

The  purified  potassium  carbonate  of  pharmacy  is  prepared  from  the  crude 
article  by  adding  an  equal  weight  of  cold  water,  agitating  and  filtering  : 
most  of  the  foreign  salts  are,  from  their  inferior  degree  of  solubility,  left 
behind.  The  solution  is  then  boiled  down  to  a  very  small  bulk,  and  suffered 
to  cool,  when  the  carbonate  separates  in  small  crystals  contniinnc:  2  mole- 
cules of  water,  C03K2.20H2;  these  are  drained  from  the  mother-liquor,  and 
then  dried  in  a  stove. 

A  still  purer  salt  may  be  obtained  by  exposing  to  a  red-heat  purified  cream 
of  tartar  (acid  potassium  tartrate),  and  separating  the  carbonate  by  solu- 
tion in  water  and  crystallization,  or  evaporation  to  dryness. 


POTASSIUM. 

Potassium  carbonate  is  extremely  deliquescent,  and  soluble  in  less  than 
its  own  weight  of  water:  the  solution  is  highly  alkaline  to  test-j>aj.i-r.  It 
is  insoluble  in  alcohol.  By  heat  the  water  of  crystallization  is  driven  «,n; 
and  by  a  temperature  of  full  ignition  the  salt  is  fused,  but  not  otherwise 
changed.  This  substance  is  largely  used  in  the  arts,  and  is  a  compound  of 
great  importance. 

Acid  potassium  carbonate,  Hydrogen  potassium  carbonate,  or  Mono-polassic 
carbonate,  CO3KH  =  C02(KHO) ;  commonly  called  bicarbonate  of  potash. — 
When  a  stream  of  carbonic  acid  gas  is  passed  through  a  cold  solution  of 
potassium  carbonate,  the  gas  is  rapidly  absorbed,  and  a  white,  crystalline, 
and  less  soluble  substance  separated,  which  is  the  acid  salt.  It  is  collected, 
pressed,  re-dissolved  in  warm  water,  and  the  solution  left  to  crystallize. 

Acid  potassium  carbonate  is  much  less  soluble  than  the  normal  carbon- 
ate:  it  requires  for  that  purpose  4  parts  of  cold  water.  The  solution  is 
nearly  neutral  to  test-paper,  and  has  a  much  milder  taste  than  the  normal 
salt.  When  boiled  it  gives  off  carbon  dioxide.  The  crystals,  which  are 
large  and  beautiful,  derive  their  form  from  a  monoclinic  prism:  they  are 
decomposed  by  heat,  water  and  carbon  dioxide  being  evolved,  and  normal 
carbonate  left  behind : 

2C03KH    =     C03K2     -f     OH2    -f     C02. 

POTASSIUM  SULPHATES.  — Potassium  forms  a  normal  or  neutral  sulphate, 
two  acid  sulphates,  and  an  anhydrouulphate. 

Normal  potassium  sulphate,  or  JJipo/assic  sulphate,  S04K2  =•  S02(OK)2  --— 
S03.OK2,  is  obtained  by  neutralizing  the  acid  residue  left  in  the  retort  when 
nitric  acid  is  prepared,  with  crude  potassium  carbonate.  The  solution 
yields,  on  cooling,  hard  transparent  crystals  of  the  neutral  sulphate,  which 
may  be  re-dissolved  in  boiling  water,  and  re-crystallized. 

Potassium  sulphate  is  soluble  in  about  10  parts  of  cold,  and  in  a  much 
smaller  quantity  of  boiling  water:  it  has  a  bitter  taste,  and  is  neutral  to 
test-paper.  The  crystals  are  combinations  of  rhombic  pyramids  and  prisms, 
much  resembling  those  of  quartz  in  figure  and  appearance:  they  arc  anhy- 
drous, and  decrepitate  when  suddenly  heated,  which  is  often  the  case  with 
salts  containing  no  water  of  crystallization.  They  are  quite  insoluble  in 
alcohol. 

Acid  potassium  sulphate,  Hydrogen  and  potassium,  sulphate,  or  Monopotassic 
sulphate,  S04KH  =  S02(OK)(OH)  =  S03.OKH,  commonly  called  bmilphate 
of  potash.  —  To  obtain  this  salt,  the  neutral  sulphate  in  powder  is  mixed 
with  half  its  weight  of  oil  of  vitriol,  and  the  whole  evaporated  quite  to 
dryness  in  a  platinum  vessel,  placed  under  a  chimney:  the  fused  salt  is 
dissolved  in  hot  water,  and  left  to  crystallize.  The  crystals  have  the  figure 
of  flattened  rhombic  prisms,  and  are  much  more  soluble  than  the  neutral 
salt,  requiring  only  twice  their  weight  of  water  at  15-5°,  and  less  than  half 
that  quantity  at  100°.  The  solution  has  a  sour  taste  and  strongly  acid 
reaction. 

Another  acid  sulphate,  containing  (S04)3K4H2  or  2S04K2.S04H2,  crystal- 
lizing in  fine  needles  resembling  asbestos,  was  obtained  by  Phillips  from  the 
nitric  acid  residue.  Jacquelain  was  unsuccessful  in  his  attempts  to  repro- 
duce this  compound. 

The  anhydrosulphate,  S04K2.S03  =  2S03.OK2,  commonly  called  MAgfdhMM 
l>ixnlphate  of  potash,  is  obtained  by  dissolving  equal  weights  of  the  normal 
sulphate  and  oil  of  vitriol  in  a  small  quantity  of  warm  distilled  water,  and 
hviving  the  solution  to  cool.  The  anhydrous  sulphate  crystalli/.es  out  in 
long  delicate  needles,  which  if  left  for  several  days  in  the  mother-liquor, 
disappear,  and  give  place  to  crystals  of  the  ordinary  acid  sulphate  above 
described.  This  salt  is  decomposed  by  a  large  quantity  of  water.* 

*  Jacquelain,  Ann.  Chim.  Phys.  [3],  vol.  vii.  p.  311. 


298  MONAD    METALS. 

POTASSIUM  SULPHIDES.  — Potassium  heated  in  sulphur  vapor  burns  with 
great  brilliancy.  It  unites  with  sulphur  in  five  diU'ercnt  proportions, 
forming  the  compounds  SK2,  S,K2,  S3K2,  S4K2,  S5K2;  also  a  sulph-hydrate, 
SKII. 

Monosulphide,  SK2.  —  It  is  doubtful  whether  this  compound  has  been  ob- 
tained in  the  pure  state.  It  is  commonly  said  to  be  produced  by  heating 
potassium  sulphate  in  a  current  of  dry  hydrogen,  or  by  igniting  the  same 
salt  in  a  covered  vessel  with  finely  divided  charcoal;  but,  according  to 
Bauer,  one  of  the  higher  sulphides  is  always  formed  at  the  same  time,  to- 
gether with  oxide  of  potassium.  The  product  has  a  reddish-yellow  color, 
is  deliquescent,  and  acts  as  a  caustic  on  the  skin.  When  potassium  sulphate 
is  heated  in  a  covered  crucible  with  excess  of  lamp-black,  a  mixture  of  potas- 
sium sulphide  and  finely  divided  carbon  is  obtained,  which  takes  fire  spontane- 
ously on  coming  in  contact  with  the  air.  The  monosulphide  might  perhaps 
be  obtained  pure  by  heating  1  molecule  of  potassium  sulph-hydrate,  KHS, 
with  1  atom  of  the  metal. 

When  sulph-hydric  acid  gas  is  passed  to  saturation  into  a  solution  of 
caustic  potash,  a  solution  of  the  sulph-hydrate  is  obtained,  which  is  color- 
less at  first,  but  if  exposed  to  the  air,  quickly  absorbs  oxygen,  and  turns 
yellow,  in  consequence  of  the  formation  of  bisulphide : 

2SKH    -f     0     =     S2K2     -f     OH2. 

If  a  solution  of  potash  be  divided  into  two  equal  parts,  and  one  half 
saturated  with  hydrogen  sulphide,  and  then  mixed  with  the  other,  a  solu- 
tion is  formed  which  may  contain  potassium  monosulphide : 

SKH     4-     OKH    =     SK2     4-     OH2. 

But  it  is  also  possible  that  the  hydrate  and  the  sulph-hydrate  may  mix 
without  mutual  decomposition.  The  solution,  when  mixed  with  one  of  the 
stronger  acids,  gives  oft'  hydrogen  sulphide  without  deposition  of  sulphur, 
a  reaction  which  is  consistent  with  either  view  of  its  constitution. 

The  bisulphide,  S2K2,  is  formed,  as  already  observed,  on  exposing  a  solu- 
tion of  the  sulph-hydrate  to  the  air  till  it  begins  to  show  turbidity.  By 
evaporation  in  a  vacuum,  it  is  obtained  as  an  orange-colored,  easily  fusible 
substance. 

The  trisulphide,  S3K2,  is  obtained  by  passing  the  vapor  of  carbon  bisul- 
phide over  ignited  potassium  carbonate,  as  long  as  gas  continues  to  escape : 

2C03K2    +     3CS2    =r     2S3K2    -f     4CO     +     C02. 

Also,  together  with  potassium  sulphate,  forming  one  of  the  mixtures  called 
liver  of  sulphur,  by  melting  552  parts  (4  molecules)  of  potassium  carbonate 
with  320  parts  (10  atoms)  of  sulphur: 

4C03K2     -f     S10    ==     S04K2     +     3S3K2     +     4C02. 

The  tetrasulphide,  S4K2,  is  formed  by  reducing  potassium  sulphate  with 
the  vapor  of  carbon  bisulphide. 

The  pentasulphide,  S5K2,  is  formed  by  boiling  a  solution  of  any  of  the 
preceding  sulphides  with  excess  of  sulphur  till  it  is  saturated,  or  by  fusing 
either  of  them  in  the  dry  state  with  sulphur.  The  excess  of  sulphur  then 
separates  and  floats  above  the  dark-brown  pentasulphide. 

Liver  of  sulphur,  or  hepar  sulphuris,  is  a  name  given  to  a  brownish  sub- 
stance, sometimes  used  in  medicine,  made  by  fusing  together  different 
proportions  of  potassium  carbonate  and  sulphur.  It  is  a  variable  mix- 
ture of  the  two  higher  sulphides  with  hyposulphite  and  sulphate  of  po- 
tassium. 

When  equal  parts  of  sulphur  and  dry  potassium  carbonate  are  melted 
together  at  a  temperature  not  exceeding  250°  C.  (482°  F.),  the  decomposi- 


SODIUM.  299 

lion  of  the  salt  is  quite  complete,  and  all  the  carbon  dioxide  is  expelled. 
The  fused  mass  dissolves  in  water,  with  the  exception  of  a  little  mei-han- 
ically  mixed  sulphur,  with  dark-brown  color,  and  the  solution  is  foun<l  to 
contain  nothing  besides  pentasulphide  and  hyposulphite  of  potassium: 

30K2     +     S12    =    2S6K2    +     S^K,. 

When  the  mixture  has  been  exposed  to  a  temperature  approaching  that 
of  ignition,  it  is  found,  on  the  contrary,  to  contain  potassium  sulphate, 
arising  from  the  decomposition  of  the  hyposulphite  which  then  occurs: 

E4S203K2     =     S6K2     4.     3S04K2. 
From  both  these  mixtures  the  potassium  pentasulphide  may  be  extracted 
by  alcohol,  in  which  it  dissolves. 

When  the  carbonate  is  fused  with  half  its  weight  of  sulphur  only,  the 
trisulphide  is  produced,  as  above  indicated,  instead  of  the  pentasulphide. 

The  effects  described  happen  in  the  same  manner  when  potassium 
hydrate  is  substituted  for  the  carbonate ;  also,  when  a  solution  of  the  hy- 
drate is  boiled  with  sulphur,  a  mixture  i>{  sulphide  and  hyposulphite  al- 
ways results. 

Potassium-salts  are  colorless,  when  not  associated  with  a  colored  metallic 
oxide  or  acid.  They  are  all  more  or  less  soluble  in  water,  and  may  be 
distinguished  by  the  following  characters : 

(1.)  Solution  of  tartaric  acid,  added  in  excess  to  a  moderately  strong  solu- 
tion of  potassium-salt,  gives,  after  some  time,  a  white  crystalline  precipi- 
tate of  cream  of  tartar ;  the  effect  is  greatly  promoted  by  strong  agitation. 

(2.)  Solution  of  platinic  chloride  with  a  little  hydrochloric  acid,  if  neces- 
sary, gives,  under  similar  circumstances,  a  crystalline  yellow  precipitate, 
which  is  a  double  salt  of  platinum  tetrachloride  and  potassium  chloride. 
Both  this  compound  and  cream  of  tartar  are,  however,  soluble  in  about  60 
parts  of  cold  water.  An  addition  of  alcohol  increases  the  delicacy  of  both 
tests. 

(3.)  Perchloric  acid,  and  silicojluoric  acid,  give  rise  to  slightly  soluble  white 
prcipitates  when  added  to  a  potassium-salt. 

(4.)  Potassium-salts  usually  color  the  outer  blowpipe-flame  purple  or 
violet :  this  reaction  is  clearly  perceptible  only  when  the  potassium-salts 
are  pure. 

(5.)  The  spectral  phenomena  exhibited  by  potassium  compounds  are  men- 
tioned at  p.  88. 


SODIUM. 

Atomic  weight,  23.     Symbol,  Na.  (Natrium). 

SODIUM  is  a  very  abundant  element,  and  very  widely  diffused.  It  occurs 
in  large  quantities  as  chloride,  in  rock-salt,  sea-water,  salt-springs,  and 
many  other  mineral  waters ;  more  rarely  as  carbonate,  borate,  and  sul- 
phate, in  solution  or  in  the  solid  state,  and  as  silicate  in  many  minerals. 

Metallic  sodium  was  obtained  by  Davy  soon  after  the  discovery  of  po- 
tassium, and  by  similar  means.  Gay-Lussac  and  Thenanl  afterwards  pre- 
pared it  by  decomposing  sodium  hydrate  with  metallic  iron  at  a  white  heat; 
and  Brunner  showed  that  it  may  be  prepared  with  much  greater  facility 
by  distilling  a  mixture  of  sodium  carbonate  and  charcoal. 

The  preparation  of  sodium  by  this  last-mentioned  process  is  much  easier 
than  that  of  potassium,  not  being  complicated,  or  only  to  a  slight  extent, 


300 


MONAD  METALS. 


by  the  formation  of  secondary  products.  Within  the  last  few  years  it  has 
been  considerably  improved  by  Deville  and  others,  and  carried  out  on  the 
manufacturing  scale,  sodium  being  now  employed  in  considerable  quantity 
as  a  reducing  agent,  especially  in  the  manufacture  of  aluminium  and  mag- 
nesium, and  in  the  silver  amalgamation  process. 

The  sodium  carbonate  used  for  the  preparation  is  prepared  by  calcining 
the  crystallized  neutral  carbonate.  It  must  be  thoroughly  dried,  then 
pounded  and  mixed  with  a  slight  excess  of  pounded  charcoal  or  coal.  An 
inactive  substance,  viz.  pounded  chalk,  is  also  added  to  keep  the  mixture 
pasty  condition  during  the  operation,  and  prevent  the  fused  sodium 


carbonate  from  separating  from  the  charcoal, 
portions  recommended  by  Deville  : 


The  following  are  the  pro- 


For  Laboratory  Operations. 
Dry  sodium  carbonate,       717  parts 

Charcoal 175      " 

Chalk 108      " 


For  Manufacturing  Operations. 
Dry  sodium  carbonate,      30  kilogr. 

Coal 13      « 

Chalk  .     .  3      " 


These  materials  must  be  very  intimately  mixed  by  pounding  and  sifting, 
and  it  is  advantageous  to  calcine  the  mixture  before  introducing  it  into  the 
distilling  apparatus,  provided  the  calcination  can  be  effected  by  the  waste 
heat  of  a  furnace ;  the  mixture  is  thereby  rendered  more  compact,  so  that 
a  much  larger  quantity  can  be  introduced  into  a  vessel  of  given  size. 

The  distillation  is  performed,  on  the  laboratory  scale,  in  a  mercury  bottle 
heated  exactly  in  the  manner  described  for  the  preparation  of  potassium. 
For  manufacturing  operations,  the  mixture  is  introduced  into  iron  cylin- 
ders, which  are  heated  in  a  reverberatory  furnace,  and  so  arranged  that, 
at  the  end  of  the  distillation,  the  exhausted  charge  may  be  withdrawn  and 
a  fresh  charge  introduced,  without  displacing  the  cylinders  or  putting  out 
the  fire.  The  receivers  used  in  either  case  are  the  same  in  form  and  di- 
mensions as  those  employed  in  the  preparation  of  potassium  (p.  291). 

When  the  process  goes  on  well,  the  sodium  collected  in  the  receivers  is 
nearly  pure;  it  may  be  completely  purified  by  melting  it  under  a  thin  layer 
of  naphtha.  This  liquid  is  decanted  as  soon  as  the  sodium  becomes  per- 
fectly fluid,  and  the  metal  is  run  into  moulds  like  those  used  for  casting 
lead  or  zinc. 

SODIUM  CHLORIDE  ;  COMMON  SALT,  NaCl.  —  This  very  important  substance 
is  found  in  many  parts  of  the  world  in  solid  beds  or  irregular  strata  of  im- 
mense thickness,  as  in  Cheshire,  Spain,  Galicia,  and  many  other  localities. 
An  inexhaustible  supply  exists  also  in  the  waters  of  the  ocean,  and  large 
quantities  are  obtained  from  saline  springs. 

Hock-salt  is  almost  always  too  impure  for  use.  If  no  natural  brine-spring 
exists,  an  artificial  one  is  formed  by  sinking  a  shaft  into  the  rock-salt,  and, 
if  necessary,  introducing  water.  This  when  saturated  is  pumped  up,  and 
evaporated  more  or  less  rapidly  in  large  iron  pans.  As  the  salt  separates, 
it  is  removed  from  the  bottom  of  the  vessel  by  means  of  a  scoop,  pressed 
while  still  moist  into  moulds,  arid  then  transferred  to  the  drying-stove. 
When  large  crystals  are  required,  as  for  the  coarse-grained  bay-saH  used  in 
curing  provisions,  the  evaporation  is  slowly  conducted.  Common  salt  is 
apt  to  be  contaminated  with  magnesium  chloride. 

Sodium  chloride,  when  pure,  is  not  deliquescent  in  moderately  dry  air. 
It  crystallizes  in  anhydrous  cubes,  which  are  often  -grouped  together  into 
pyramids,  or  steps.  It  requires  about  1\  parts  of  water  at  1-5-5°  C.  (60° 
F.)  for  solution,  and  its  solubility  is  not  sensibly  increased  by  heat;  it  dis- 
solves to  some  extent  in  spirit  of  wine,  but  is  nearly  insoluble  in  absolute 
alcohol.  It  melts  at  a  red  heat,  and  is  volatile  at  a  still  higher  temperature. 
The  economical  uses  of  common  salt  are  well  known. 


SODIUM. 


301 


The  iodide  and  bromide  of  sodium  much  resemble  the  corresponding  potas- 
um-compoumls:   they  crystallize  in  cubes  which  are  anhydrous,  and  very 


sium 

soluble  in  water. 


SODIUM  OXIDES.  — Sodium  forms  a  monoxide  and  a  dioxide  ;  also 
drate  corresponding  to  the  former. 


hy- 


Sodium  Monoxide,  or  Anhydrous  Soda,  ONa2,  is  produced,  together  with 
the  dioxide,  when  sodium  burns  in  the  air,  and  may  be  obtained  pure  by 
exposing  the  dioxide  to  a  very  high  temperature;  or  by  heating  sodium 
hydrate  with  an  equivalent  quantity  of  sodium :  20NaH  -(-  Na2  =  20Na 
-f-  H2.  It  is  a  gray  mass,  which  melts  at  a  red  heat,  and  volatilizes  with 
difficulty. 

Sodium  Hydrate,  or  Caustic  Soda,  ONaH  or  ONa2,  OH2.  —  This  substance 
is  prepared  by  decomposing  a  somewhat  dilute  solution  of  sodium  carbonate 
with  calcium  hydrate:  the  description  of  the  process  employed  in  the  case 
of  potassium  hydrate,  and  the  precautions  necessary,  apply  word  for  word 
to  that  of  sodium  hydrate. 

The  solid  hydrate  is  a  white,  fusible  substance,  very  similar  in  properties 
to  potassium  hydrate.  It  is  deliquescent,  but  dries  up  again  after  a  time 
in  consequence  of  the  absorption  of  carbonic  acid.  The  solution  is  highly 
alkaline,  and  a  powerful  solvent  for  animal  matter:  it  is  used  in  large 
quantity  for  making  soap. 

The  strength  of  a  solution  of  caustic  soda  may  be  roughly  determined 
from  a  knowledge  of  its  density,  by  the  aid  of  the  following  table  drawn 
up  by  Dalton: 

TABLE    OF    PERCENTAGE    OP    ANHYDROUS    SODA,    ONa2,    IN    SOLUTIONS    OF 
DIFFERENT    DENSITY. 


Density. 
2-00 
1-85 
1-72 
1-63 
1-55 
1-50 
1-47 
1-44 


Percentage  of 
anhydrous  soda. 

Density. 

.    77-8 

•40 

63-6 

•36 

.    53-8 

•32 

46-6 

•29 

.    41-2 

•23 

36-8 

•18 

.    34-0 

•12 

31-0 

•06 

Percentage  of 

anhydrous  soda. 

.    29-0 

26-0 

.    23-0 

19-0 

.    16-0 

13-0 

.      9-0 

4-7 


Sodium  Dioxide,  02Na2.  — Sodium,  when  heated  to  about  200°  in  a  current 
of  dry  air,  absorbs  oxygen,  and  is  converted  into  dioxide :  this  substance  is 
white,  but  becomes  yellow  when  heated,  which  tint  it  again  loses  on  cool- 
ing. It  is  soluble  in  water  without  decomposition:  the  solution  maybe 
evaporated  under  the  receiver  of  the  air-pump,  and,  when  sufficiently  con- 
centrated, deposits  crystalline  plates  having  the  composition  02Na2.80Ha. 
These  crystals  left  to  effloresce  over  oil  of  vitriol  for  nine  days  lose  three 
fourths  of  their  water,  and  yield  another  hydrate  containing  02Na2.20H3 
(Ilarcourt).  The  aqueous  solution  of  sodium  dioxide  when  heated  on  the 
water-bath,  is  decomposed  into  oxygen  and  the  monoxide. 

SODIUM  CARBONATES.  —  The  Neutral  or  Disodic  Carbonate,  C03Na2.100Hr 
was  once  exclusively  obtained  from  the  ashes  of  sea-weeds,  and  of  plants, 
such  as  the  Salsola  soda,  which  grow  by  the  sea-side,  or,  being  cultivated 
in  suitable  localities  for  the  purpose,  are  afterwards  subjected  to  incinera- 
tion. The  barilla,  still  employed  to  a  small  extent  in  soap-making,  is  thus 
produced  in  several  places  on  the  coast  of  Spain,  as  Alicante,  Carthagena, 

.     That  made  in  Brittany  is  called  varec. 
26 


302  MONAD    METALS. 

Sodium  carbonate  is  now  manufactured  on  a  stupendous  scale  from  com- 
mon salt  by  a  series  of  processes  which  may  be  divided  into  two  stages :  — 

(1.)  Manufacture  of  sodium  sulphate,  or  salt-cake,  from  sodium  chloride 
(common  salt);  this  is  called  the  salt-cake  process. 

(2.)  Manufacture  of  sodium  carbonate,  or  soda-ash;  called  the  soda-ash 
process. 

(1.)  Salt-cake  process. — This  process  consists  in  the  decomposition  of 
common  salt  by  sulphuric  acid,  and  is  effected  in  a  furnace  called  the  Salt- 
cake  furnace,  of  which  fig.  164  represents  a  section.  It  consists  of  a  large 

Fig.  164. 


covered  iron  pan,  placed  in  the  centre,  and  heated  by  a  fire  underneath ; 
and  two  roasters,  or  reverberatory  furnaces,  placed  one  at  each  end,  and  on 
the  hearths  of  which  the  salt  is  completely  decomposed.  The  charge  of 
half  a  ton  of  salt  is  first  placed  in  the  iron  pan,  and  then  the  requisite 
quantity  of  sulphuric  acid  is  allowed  to  pass  in  upon  it.  Hydrochloric  acid 
is  evolved,  and  escapes  through  a  flue,  with  the  products  of  combustion, 
into  towers  or  scrubbers,  filled  with  coke  and  bricks  moistened  with  a  stream 
of  water;  the  whole  of  the  acid  vapors  are  thus  condensed,  and  the  smoke 
and  heated  air  pass  up  the  chimney.  After  the  mixture  of  salt  and  acid 
has  been  heated  in  the  iron  pan,  it  becomes  converted  into  a  solid  mass  of 
acid  sodium  sulphate  and  undecomposed  sodium  chloride : 

2NaCl    -f     S04H2    =    NaCl     -f     S04NaH     +     HC1. 

It  is  then  raked  on  to  the  hearths  of  the  furnaces  at  each  side  of  the  decom- 
posing pan,  where  the  flame  and  heated  air  of  the  fire  complete  the  decom- 
position into  neutral  sodium  sulphate  and  muriatic  acid : 

NaCl     +     S04NaH     =     S04Na2     -f     HC1. 

(2.)  Soda-ash  process.  —  The  sulphate  is  next  reduced  to  powder,  and 
mixed  with  an  equal  weight  of  chalk  or  limestone,  and  half  as  much  small 
coal,  both  ground  or  crushed.  The  mixture  is  thrown  into  a  reverberatory 
furnace,  and  heated  to  fusion,  with  constant  stirring,  2  cwts.  are  about  the 
quantity  operated  on  at  once.  When  the  decomposition  is  judged  complete, 
the  melted  matter  is  raked  from  the  furnace  into  an  iron  trough,  where  it 
is  allowed  to  cool.  This  crude  product,  called  black  ash  or  ball-soda,  is 
broken  up  into  little  pieces,  when  cold,  and  lixiviated  with  cold  or  tepid 
water.  The  solution  is  evaporated  to  dryness,  and  the  salt  calcined  with  a 
little  sawdust  in  a  suitable  furnace.  The  product  is  the  soda-ash,  or  British 
alkali  of  commerce,  which,  when  of  good  quality,  contains  from  48  to  52 
per  cent,  of  anhydrous  soda,  ONn2,  partly  in  the  state  of  carbonate,  and 
partly  as  hydrate,  the  remainder  being  chiefly  sodium  sulphate  and  common 
salt,  with  occasional  traces  of  sulphite  or  hyposulphite,  and  also  cyanide 
of  sodium.  By  dissolving  soda-ash  in  hot  water,  filtering  the  solution,  and 
then  allowing  it  to  cool  slowly,  the  carbonate  is  deposited  in  large  trans- 
parent crystals. 

The  reaction  which  takes  place  in  the  calcination  of  the  sulphate  with 
chalk  and  coal-dust  seems  to  consist,  first,  in  the  conversion  of  the  sodium 
sulphate  into  sulphide  by  the  aid  of  the  combustible  matter,  and,  secondly, 


SODIUM. 

in  the  interchange  of  elements  between  that  substance  and  the  calcium  car- 
bonate : 

SNa2       -f        C03Ca       =       SCa       +       C03Na2 
Sodium  Calcium  Calcium  Sodium 

sulphide.  carbonate.  sulphide.          carbonate. 

Other  processes  have  been  proposed,  and  even  carried  into  execution; 
but  the  above,  which  was  originally  proposed  by  Leblanc,  is  found  most 
advantageous. 

The  ordinary  crystals  of  sodium  carbonate  contain  ten  molecules  of 
water ;  but  by  particular  management  the  same  salt  may  be  obtained  with 
fifteen,  nine,  seven,  molecules,  or  sometimes  with  only  one.  The  common 
form  of  the  crystals  is  derived  from  an  oblique  rhombic  prism;  they 
effloresce  in  dry  air.  and  crumble  to  a  white  powder.  Heated,  they  fuse  in 
their  water  of  crystallization;  when  the  latter  has  been  expelled,  and  the 
dry  salt  exposed  to  a  full  red  heat,  it  melts  without  undergoing  change.  The 
common  crystals  dissolve  in  two  parts  of  cold,  and  in  less  than  their  own 
weight  of  boiling  water :  the  solution  has  a  strong,  disagreeable,  alkaline 
taste,  and  a  powerfully  alkaline  reaction. 

Hydrogen  and  Sodium  Carbonate,  Hydrosodic  Carbonate,  Monosodic  Car- 
bonate, Acid  Sodium  Carbonate,  C03NaH,  or  C05Na2.C03H2,  commonly  called 
Bicarbonate  of  soda.  —  This  salt  is  prepared  by  passing  carbonic  acid  gas 
into  a  cold  solution  of  the  neutral  carbonate,  or  by  placing  the  crystals  in 
an  atmosphere  of  the  gas,  which  is  rapidly  absorbed,  while  the  crystals 
lose  the  greater  part  of  their  water,  and  pass  into  the  new  compound. 

Monosodic  carbonate,  prepared  by  either  process,  is  a  crystalline  wl;ite 
powder,  which  cannot  be  re-dissolved  in  warm  water  without  partial  de- 
composition. It  requires  10  parts  of  water  at  15-5°  for  solution :  the  liquid 
is  feebly  alkaline  to  test-paper,  and  has  a  much  milder  taste  than  that  of 
the  simple  carbonate.  It  does  not  precipitate  a  solution  of  magnesia.  By 
exposure  to  heat,  the  salt  is  converted  into  neutral  carbonate. 

Dihydro-tetrasodic  Carbonate,  (C03)3Na4H2 .  20H2. —  This  salt,  commonly 
called  sesquicarbonate  of  soda,  may  be  regarded  as  a  compound  of  the  neutral 
and  acid  salts  just  described  (C03Na2.2C03NaH).  It  occurs  native  on  the 
banks  of  the  soda  lakes  of  Sokenna,  near  Fezzan,  in  Africa,  where  it  is  called 
trona;  also  as  urao,  at  the  bottom  of  a  lake  in  Maracaibo,  South  America. 
It  is  produced  artificially,  though  with  some  difficulty,  by  mixing  the  mo- 
nosodic  and  disodic  carbonates  in  the  proportions  above  indicated,  melting 
them  together,  drying  and  exposing  the  dried  mass  in  a  cellar  for  some 
weeks;  it  then  absorbs  water,  becomes  crystalline,  and  contains  spaces 
filled  with  the  tetrasodic  carbonate. 

Sodium  and  Potassium  Carbonate,  C03NaK .  60H2,  separates  in  monoclinic 
crystals  from  a  solution  containing  the  two  carbonates  in  equivalent  pro- 
portions. 

A  mixture  of  these  two  carbonates  in  equivalent  proportions  melts  at  a 
much  lower  heat  than  either  of  the  salts  separately;  such  a  mixture  is 
very  useful  in  the  fusion  of  silicates,  &c- 

Alkalimetry.  —  Analysis  of  Alkaline  Hydrates  and  Carbonates. 

The  amount  of  alkali  or  alkaline  carbonate  in  commercial  potash,  flpda, 
or  ammonia,  is  estimated  by  determining  the  quantity  of  an  acid  of  gm-n 
strength  required  to  neutralize  a  given  weight  of  the  sample.  The  estim.-i- 
tion  depends  upon  the  facts  that  the  alkaline  salts  of  strong  acids  (sul- 
phuric, oxalic,  &c.)  are  neutral  to  litmus;  and  that  the  violet  solution  of 
litmus  is  colored  blue  by  caustic  alkalies  or  alkaline  carbonates,  wine-red 
by  carbonic  acid,  and  light  red  by  strong  acids. 


304  MONAD    METALS. 

The  first  step  is  the  preparation  of  the  standard  acid.  It  is  best  to  make 
this  liquid  of  such  strength  that  1000  cubic  centimetres  (1  litre)  shall 
contain  exactly  one  J  gram-molecule  (i.  e.,  1  molecule  expressed  in  J  grams) 
of  the  acid. 

About  70  grams  of  concentrated  sulphuric  acid  are  diluted  with  about 
600  grams  of  water ;  when  the  mixture  is  cool,  the  volume  of  it  necessary 
to  saturate  5-3  grams  (one  J-decigram-moleculc)  of  pure  anhydrous  sodium 
carbonate,  C03Na2,  is  determined.*  For  this  purpose  5-3  grams  of  freshly 
ignited  sodium  carbonate  are  dissolved  in  hot  water,  the  solution  colored 
blue  with  a  few  drops  of  litmus,  and  the  acid  added  from  a  burette  or  al- 
kalimeter  (p.  305),  at  last  drop  by  drop,  till  the  color  just  passes  from 
wine-red  to  light  red,  and  till  strips  of  litmus-paper,  moistened  with  the 
solution  begin  to  retain  the  color  when  dry.  The  volume  of  acid  employed 
is  then  noted,  and  the  whole  diluted  so  as  to  approximate  to  the  required 
strength.  Suppose,  for  instance,  37  cubic  centimetres  of  acid  have  been 
used  ;  water  is  then  added  till  every  100  volumes  is  diluted  to  250  volumes, 
and  another  determination  is  made.  If  90  cubic  centimetres  are  now  re- 
quired to  saturate  the  J-decigram  alkaline  solution,  every  90  volumes  of  the 
acid  must  be  diluted  to  100,  and  the  result  controlled  by  a  fresh  determina- 
tion; 100  cubic  centimetres  of  this  acid  should  exactly  saturate  5-3  grams 
of  sodium  carbonate,  and  will  contain  1  half-dccigram-rnolecule  of  acid; 
2  cubic  centimetres  will  therefore  contain  1  milligram-molecule  (0-098 
gram)f  and  will  saturate  2  milligram-molecules  of  an  alkali  (OKH  or 
ONaH),  or  1  milligram-molecule  of  an  alkaline  carbonate  (C03K2  or  C03Na2). 

To  estimate  the  proportion  of  alkali  in  a  commercial  sample,  a  weighed 
portion  of  the  substance  is  dissolved  in  water  (if  a  solid),  a  few  drops  of 
litmus  added,  and  the  standard  acid  added  from  a  burette,  until  the  first 
permanent  appearance  of  a  light  red  color ;  and  the  volume  of  acid  em- 
ployed is  read  off.  Each  cubic  centimetre  of  acid  corresponds  to  1  milli- 
gram-molecule of  alkali,  or  1  half  milligram-molecule  of  alkaline  carbonate ; 
i.  e.,  to  0-053  gram  sodium  carbonate,  C03Na2,  0-069  gram  potassium  carbo- 
nate, C03K2,  0.040  gram  caustic  soda  ONaH,  0-056  gram  caustic  potash  OKH, 
and  0-017  gram  ammonia  NH3;  and  a  simple  proportion  gives  the  amount 
of  alkali  or  alkaline  carbonate  present  (e.  g.  100  :  6-9  :  :  number  of  cubic 
centimetres  employed:  potassium  carbonate  present).  By  operating  on 
100  times  the  ^-milligram-molecule  (e.  g.  6-9  grams  in  the  case  of  potassium 
carbonate,  5-3  grams  in  the  case  of  sodium  carbonate),  all  calculation  is 
saved :  for  as  this  amount,  if  present,  would  require  100  cubic  centimetres 
of  acid  for  its  saturation,  the  number  of  cubic  centimetres  actually  required 
at  once  indicates  the  percentage  of  alkaline  carbonate.  The  burettes 
commonly  used  contain  50  cubic  centimetres,  and  are  graduated  into  half 
cubic  centimeters;  so  that  by  operating  on  50  times  the  ^-milligram-mole- 
cule, the  number  of  divisions  employed  indicates  the  percentage. 

Sometimes,  instead  of  exactly  neutralizing  the  alkali  with  the  standard 
acid,  it  is  better  to  add  the  acid  till  the  litmus  assumes  a  distinct  light-red 
color,  then  heat  the  solution  to  boiling,  and  add  a  small  excess  (5  to  10 
cubic  centimetres)  of  acid.  The  hot  solution  is  freed  from  carbonic  acid  by 
agitation  and  by  drawing  air  through  it  with  a  glass  tube  ;  and  then  neu- 
tralized with  a  standard  solution  of  caustic  soda  (100  cubic  centimetres  of 
which  exactly  saturate  100  cubic  centimetres  of  the  standard  acid)  till  the 
color  just  changes  from  red  to  blue.  Since  the  acid  and  alkaline  solutions 
neutralize  each  other  volume  for  volume,  it  is  only  necessary  to  deduct  the 
number  of  cubic  centimetres  employed  of  the  latter  from  that  of  the  former, 
and  calculate  the  amount  of  alkali  from  the  residue.  This  method,  called 
the  indirect  or  residual  method,  is  preferable  to  the  direct  method  previously 

*  The  molecule  of  sodium  carbonate  CO?Na2  weighs  12  -f  48  -f  46  :r  106. 
f  The  molecular  weight  of  sulphuric  acid  S04IL.  is  98  =  32  +  64  -f-  2. 


SODIUM. 


305 


described,  for  the  analysis  of  carbonates,  since  the  change  from  blue  to 
red  is  more  distinctly  marked  than  that  from  one  shade  of  red  to  another. 

The  standard  solution  of  caustic  soda  must  be  kept  in  a  flask,  into  the 
cork  of  which  is  inserted  a  calcium  chloride  tube  tilled  with  a  mixture  of 
sodium  sulphate  and  quicklime,  which  eifectually  prevents  the  absorption 
of  carbonic  acid.  If  the  burette  be  closed  with  a  similar  tube,  the  soda  so- 
lution may  remain  in  it  for  days. 

The  "  alkalimeter "  or  "burette"  is  a  glass  tube  (fig.  165)  Fig- 165. 
closed  at  one  end,  and  moulded  into  a  spout  or  lip  at  the  other, 
and  marked  with  any  convenient  scale  of  equal  parts,  generally, 
as  above  mentioned,  into  100  half  cubic  centimetres.*  A  strip  of 
paper  is  pasted  on  the  tube  and  suifered  to  dry,  after  which  the 
instrument  is  graduated  by  counterpoising  it  in  a  nearly  upright 
position  in  the  pan  of  a  balance  of  moderate  delicacy  and  weigh- 
ing into  it,  in  succession,  5,  10,  15,  20,  &c.,  grams  of  distilled 
water  at  4°  C.  (39-2  F.)  until  the  whole  quantity,  amounting  to  50 
grams  (50  cubic  centimetres),  has  been  introduced,  the  level  of  the 
water  in  the  tube  being,  after  each  addition,  carefully  marked 
with  a  pen  upon  the  strip  of  paper,  while  the  tube  is  held  quite 
upright,  and  the  mark  made  between  the  top  and  bottom  of  the 
curve  formed  by  the  surface  of  the  water.  The  smaller  divisions 
of  the  scale,  of  a  half  cubic  centimetre  each,  may  then  be  made 
by  dividing  with  compasses  each  of  the  spaces  into  10  equal 
parts.  When  the  graduation  is  complete,  and  the  operator  is 
satisfied  with  its  accuracy,  the  marks  may  be  transferred  to  the 
tube  itself  by  a  sharp  file,  and  the  paper  removed  by  a  little 
warm  water.  The  numbers  are  scratched  on  the  glass  with  the 
hard  end  of  the  same  file,  or  with  a  diamond.  Or  the  glass  is 
covered  with  etching  wax,  the  scale  traced  upon  it  with  a  fine 
needle  point,  and  the  marks  etched  by  exposing  the  tube  to  the  vapor  of 
hydrofluoric  acid. 

fig.  166.  Fig.  167.  Fig- 168. 


n 

> 

0 

1 

3 

* 

1 

0 

• 

10 
20 

T 

E 

4° 

-| 

20 

30 

| 

•§ 

30 

430 

-5 

40 

50 

Ir 

i 

BO 

In 

5O 

70 

->sc 

^ 

CO 

80 

f 

1 

^ 
§ 

TO 

80 

\ 

90 

no 

gf* 

c 

3 
_=- 

1 

90                                           QP 

" 

Ni> 

J 

100 

*  It  mav  also  be  divided  into  1000  grain-mcasim-H.  th«  grain-measure  being  the  capacity  of  a 
•ain  of  distilled  water  at  60°  *V,  70,000  siu-h  measure*  go  to  an  imperial  gallon,  and  8,7^0  to 

a  pint. 

26* 


306  MONAD  METALS. 

The  alkalimeter,  represented  in  fig.  165,  is  the  simplest  form  of  this  in- 
strument. The  pouring  out  of  minute  quantities  is,  however,  greatly  facil- 
itated by  providing  the  measure  with  a  narrow  dropping  tube,  fig,  166, 
the  lower  extremity  of  which  is  soldered  into  the  measure,  while  the  upper 
one  is  bent  outward  and  sharply  cut  off.  This  kind  of  burette,  which  is 
known  as  Gay-Lussac's,  is  chiefly  used  in  France.  The  liquid  may  be  very 
conveniently  poured  from  it ;  but  it  is  rather  easily  broken,  so  that  its 
manipulation  requires  a  good  deal  of  care.  This  defect  is  greatly  obviated 
in  the  burette,  fig.  167,  in  which  the  graduated  tube  is  provided  with 
a  spout  at  the  top,  there  being  at  the  same  time  an  orifice  for  pouring  in 
the  liquid. 

A  very  elegant  instrument  has  been  contrived  by  Dr.  Mohr  of  Coblentz. 
It  is  a  graduated  tube,  drawn  out  at  one  end  to  a  paint,  to  which  is  at- 
tached, by  means  of  a  narrow  vulcanized  caoutchouc  tube,  a  short  glass 
tube,  likewise  drawn  out  to  a  point  (fig.  108).  There  is  a  small  space 
(about  £  inch)  between  the  two  tubes,  upon  which  is  fixed  a  metallic  clamp, 
a,  represented  in  its  actual  dimensions  in  fig.  169.  This  clamp  shuts  off 
the  connection  between  the  graduated  cylinder  and  the  small  glass  tube. 
But  by  pressing  with  the  fingers  upon  the  ends,  b  6,  of  this  clamp,  it  opens, 
and  allows  the  liquid  to  flow  out  of  the  lower  tube.  It  is  evident  that  by 
this  arrangement  the  amount  of  liquid  may  be  regulated  with  the  greatest 
nicety. 

It  is  often  desirable,  in  the  analysis  of  carbonates,  to  determine  directly 
the  proportion  of  carbonic  acid:  the  following  methods  leave  nothing  to 
be  desired  in  point  of  precision: 

A  small  light  glass  flask  of  three  or  four  ounces  capacity,  with  lipped 
edge,  is  chosen,  and  a  cork  fitted  to  it.  A  piece  of  tube  about  three  inches 
long  is  drawn  out  at  one  extremity,  and  fitted,  by  means  of  a  small  cork 
and  a  bit  of  bent  tube,  to  the  cork  of  the  flask.  This  tube  is  filled  with 
fragments  of  calcium  chloride,  prevented  from  escaping  by  a  little  cotton 
at  either  end:  the  joints  are  secured  by  sealing-wax.  A  short  tube,  closed 
at  one  extremity,  and  small  enough  to  go  into  the  flask,  is  also  provided, 
and  the  apparatus  is  complete.  Fifty  grains  of  the  carbonate  to  be  exam- 

Fig.  169.  Fig.  170.  Fig.  171. 


€t> 


ined  are  carefully  weighed  out  and  introduced  into  the  flask,  together  with 
a  little  water;  the  small  tube  is  then  filled  with  oil  of  vitriol,  and  placed 
in  the  flask  in  a  nearly  upright  position,  and  leaning  against  its  side  in 
such  a  manner  that  the  acid  does  not  escape.  The  cork  and  calcium  chlor- 
ide tube  are  then  adjusted,  and  the  whole  apparatus  accurately  counter- 
poised on  the  balance  This  done,  the  flask  is  slightly  inclined,  so  that  th*e 
oil  of  vitriol  may  slowly  mix  with  the  other  substances  and  decompose  the 
carbonate,  the  gas  from  which  escapes  in  a  dry  state  from  the  extremity 


SODIUM.  307 


of  the  tube.  When  the  action  has  entirely  ceased,  the  liquid  is 
until  it  boils,  and  the  steam  begins  to  condense  in  the  drying-tube;  it  is 
then  left  to  cool,  and  weighed,  when  the  loss  indicates  the  quantity  of 
carbon  dioxide.  The  acid  must  be  in  excess  after  the  experiment.  When 
calcium  carbonate  is  thus  analyzed,  hydrochloric  acid  must  be  substituted 
for  the  sulphuric  acid. 

Instead  of  the  above  apparatus,  a  neat  arrangement  may  be  used,  which 
was  first  suggested  by  Will  and  Fresenius.  It  consists  of  -two  small  plass 
flasks,  A  and  B,  the  latter  being  somewhat  smaller  than  the  former.  Kadi 
of  the  flasks  is  provided  with  a  doubly  perforated  cork.  A  tube,  open  at 
both  ends,  but  closed  at  the  upper  extremity  by  means  of  a  small  quantity 
of  wax,  passes  through  the  cork  of  A  to  the  very  bottom  of  the  Husk, 
whilst  a  second  tube,  reaching  to  the  bottom  of  B,  establishes  a  communi- 
cation between  the  two  flasks.  The  cork  of  B  is  provided,  moreover,  with 
a  short  tube  d.  In  order  to  analyze  a  carbonate,  a  suitable  quantity  (fifty 
grains)  is  put  into  A,  together  with  some  water.  B  is  half  filled  with  con- 
centrated sulphuric  acid,  the  apparatus  tightly  fitted  and  weighed.  A 
small  quantity  of  air  is  now  sucked  out  of  flask  B  by  means  of  the  tube  rf, 
whereby  the  air  in  A  is  likewise  rarefied.  On  allowing  the  air  to  return, 
a  quantity  of  the  sulphuric  acid  ascends  to  the  tube  c,  and  flows  over  into  flask 
A,  causing  a  disengagement  of  carbon  dioxide,  which  escapes  at  d,  after 
having  been  perfectly  dried  by  passing  through  the  bottle  B.  This  opera- 
tion is  repeated  until  the  whole  of  the  carbonate  is  decomposed,  and  the 
process  terminated  by  opening  the  wax  stopper,  and  drawing  a  quantity  of 
air  through  the  apparatus.  The  apparatus  is  now  re-weighed.  The  dif- 
ference of  the  two  weighings  expresses  the  quantity  of  carbon  dioxide  in 
the  compound  analyzed. 

SODIUM  SULPHATE,  S04Na2.100H2,  commonly  called  Glauber1  s  salt,  is  a 
by-product  in  several  chemical  operations  and  an  intermediate  product  in 
the  manufacture  of  the  carbonate  as  above  described :  it  may  of  course  be 
prepared  directly,  if  wanted  pure,  by  adding  dilute  sulphuric  acid,  to  sat- 
uration, to  a  solution  of  sodium  carbonate.  It  crystallizes  in  forms  de- 
rived from  an  oblique  rhombic  prism:  the  crystals  contain  10  molecules  of 
water,  are  efflorescent,  and  undergo  watery  fusion  when  heated,  like  those 
of  the  carbonate:  they  are  soluble  in  twice  their  weight  of  cold  water, 
and  rapidly  increase  in  solubility  as  the  temperature  of  the  liquid  rises 
to- 33°  C.  (91-5°  F  ),  when  a  maximum  is  reached,  100  parts  of  water  dis- 
solving 117-9  parts  of  the  salt,  corresponding  to  52  parts  anhydrous  sodium 
sulphate.  When  the  salt  is  heated  beyond  this  point,  the  solubility  dimin- 
ishes, and  a  portion  of  sulphate  is  deposited.  A  warm  saturated  solution, 
evaporated  at  a  high  temperature,  deposits  opaque  prismatic  crystals, 
which  are  anhydrous.  The  salt  has  a  slightly  bitter  taste,  and  is  purga- 
tive. Mineral  springs  sometimes  contain  it,  as  that  at  Cheltenham. 

Sodium  and  Hi/droycn  Sulphate,  or  Acid  Sodium  Sulphate,  2S04NaH  30H2, 
or  S04Na2  S04H2.30H2,  commonly  called  bisulphate  of  soda,  is  prepared  by 
adding  to  10  parts  of  the  anhydrous  neutral  sulphate,  7  of  oil  of  vitriol, 
evaporating  the  whole  to  dryness,  and  gently  igniting.  The  acid  sulphate 
is  very  soluble  in  water,  and  has  an  acid  reaction.  It  is  not  deliquescent. 
When  very  strongly  heated,  the  fused  salt  gives  up  anhydrous  sulphuric 
acid,  and  becomes  neutral  sulphate;  a  change  which  necessarily  supposes 
the  previous  formation  of  an  anhydro-bisulphate,  S04Na.,.SO3. 

SODIUM  HYPOSULPHITE,  R.,03Xa2. — There  are  several  modes  of  procur- 
ing-this  salt,  which  is  now  used  in  considerable  quantity  for  photographic 
purposes  and  as  antichlore.  One  of  the  best  is  to  form  nputr.-il  -v, ,/;,///,  sul- 
phite, by  passing  a  stream  of  well- washed  sulphurous  oxide  gas  inm  a 


308  MONAD    METALS. 

strong  solution  of  sodium  carbonate,  and  then  digest  the  solution  with 
sulphur  at  a  gentle  heat  during  several  days.  By  careful  evaporation  at  a 
moderate  temperature,  the  salt  is  obtained  in  large  and  regular  crystals, 
which  are  very  soluble  in  water. 

SODIUM  NITRATE,  N03Na.  —  This  salt,  sometimes  called  Cubic  Nitre,  or 
Chile  Saltpetre,  occurs  native,  and  in  enormous  quantity,  at  Tarapaca  in 
Northern  Peru,  where  it  forms  a  regular  bed,  of  great  extent,  along  with 
gypsum,  common  salt,  and  remains  of  recent  shells.  The  pure  salt  com- 
monly crystallizes  in  rhombohedrons,  resembling  those  of  calcareous  spar. 
It  is  deliquescent,  and  very  soluble  in  water.  Sodium  nitrate  is  employed 
for  making  nitric  acid,  but  cannot  be  used  for  gunpowder,  as  the  mixture 
burns  too  slowly,  and  becomes  damp  in  the  air.  It  has  been  lately  used 
with  some  success  in  agriculture  as  a  superficial  manure  or  top-dressing ; 
also  for  preparing  potassium  nitrate  (p.  294). 

SODIUM  PHOSPHATES.  —  The  composition  and  chemical  relations  of 
these  salts  have  already  been  explained  in  speaking  of  the  basicity  of 
acids  (p.  285). 

Disodiohydric  Phosphate,  or  Disodic  Orthophosphate  ;  Common  Tribasic  Phos- 
phate, P04Na2H.120H2. —  This  salt  is  prepared  by  precipitating  the  acid 
calcium  phosphate  obtained  in  decomposing  bone-ash  by  sulphuric  acid, 
with  a  slight  excess  of  sodium  carbonate,  and  evaporating  the  clear  liquid. 
It  crystallizes  in  oblique  rhombic  prisms,  which  are  efflorescent.  The 
crystals  dissolve  in  4  parts  of  cold  water,  and  undergo  the  aqueous  fusion 
when  heated.  The  salt  is  bitter  and  purgative;  its  solution  is  alkaline  to 
test-paper.  Crystals  containing  7  molecules  of  water,  and  having  a  form 
different  from  that  above  mentioned,  have  been  obtained. 

A  trisodic,  orthophosphate,  sometimes  called  subphosphate,  P04Na3  120H2,  is 
obtained  by  adding  a  solution  of  caustic  soda  to  the  preceding  salt.  The 
crystals  are  slender  six-sided  prisms,  soluble  in  5  parts  of  cold  water.  It 
is  decomposed  by  acids,  even  carbonic,  but  suffers  no  change  by  heat,  ex- 
cept the  loss  of  its  water  of  crystallization.  Its  solution  is  strongly  alka- 
line. A  third  tribasic  phosphate,  often  called  superphosphate  or  biphos- 
phate,  P04NaH2.OH2,  may  be  obtained  by  adding  phosphoric  acid  to  the 
ordinary  phosphate,  until  it  ceases  to  precipitate  barium  chloride,  and 
exposing  the  concentrated  solution  to  cold.  The  crystals  are  prismatic, 
very  soluble,  and  have  an  acid  reaction.  When  strongly  heated,  the  salt 
becomes  changed  into  monobasic  sodium  phosphate,  or  metaphosphate. 

Sodium,  Ammonium,  and  Hydrogen  Phosphate;  Phosphorous  Salt;  Micro- 
cosmic  Salt,  P04Na(NH4)H.40H2. — Six  parts  of  common  sodium  phosphate 
are  heated  with  two  of  water,  until  the  whole  is  liquefied,  and  1  part  of 
powdered  sal-ammoniac  is  added;  common  salt  then  separates,  and  may  be 
removed  by  a  filter,  and  from  the  solution,  duly  concentrated,  the  micro- 
cosmic  salt  is  deposited  in  prismatic  crystals,  which  may  be  purified  by 
one  or  two  re-crystallizations.  Microcosmic  salt  is  very  soluble.  When 
gently  heated,  it  parts  with  its  4  molecules  of  crystallization  water,  and,  at 
a  higher  temperature,  the  basic  hydrogen  is  likewise  expelled  as  water, 
together  with  ammonia,  and  a  very  fusible  compound,  sodium  metaphos- 
phate, remains,  which  is  valuable  as  a  flux  in  blow-pipe  experiments. 
Microcosmic  salt  occurs  in  decomposed  urine. 

Tetrasodic  Phosphate  or  Sodium  Pyrophosphate,  P207Na4  100H2,  is  prepared 
by  strongly  heating  common  disodic  01  thophosphate,  dissolving  the  residue 
in  water,  and  re-crystallizing.  The  crystals  are  very  brilliant,  permanent 
in  the  air,  and  less  soluble  than  the  original  phosphate :  their  solution  is 
alkaline.  A  sodiohydric  pyrophosphate  has  been  obtained ;  but  it  does  not 
crystallize. 


SODIUM.  309 

Monosodic  Phosphate,  or  Sodium  Mctaphosphate,  P03Na,  is  obtained  by  heat- 
ing either  the  acid  tribasic  phosphate,  or  microcosmic  salt.  It  is  a  trans- 
parent glassy  substance,  fusible  at  a  dull  red  heat,  deliquescent,  and  very 
soluble  in  water.  It  refuses  to  crystallize,  but  dries  up  into  a  gum-like 
mass. 

If  this  glassy  phosphate  be  cooled  very  slowly,  it  separates  as  a  beauti- 
fully crystalline  mass.  It  may  be  purified  by  means  of  boiling  water  from 
the  vitreous  metaphosphate,  which  will  not  crystallize.  Another  metaphos- 
phate  has  been  obtained  by  adding  sodium  sulphate  to  an  excess  of  phos- 
phoric acid,  evaporating  and  heating  to  upwards  of  315°  (600°  F.).  Possibly 
these  several  metaphosphates  may  be  represented  by  the  formulae  P03Na, 
P206Na2,  and  P309Na3.  (Graham.) 

The  tribasic  phosphates  or  orthophosphates  give  a  bright-yellow  precipi- 
tate with  solution  of  silver  nitrate  ;  the  bibasic  and  monobasic  phosphates 
aft'ord  white  precipitates  with  the  same  substance.  The  salts  of  the  two 
latter  classes,  fused  with  excess  of  sodium  carbonate,  yield  orthophosphoric 
acid. 

Respecting  the  phosphates  intermediate  in  composition  between  the  meta- 
phosphate and  pyrophosphate  of  sodium,  discovered  by  Fleitmann  and 
Henneberg,  see  page  287. 

SODIUM  EQUATES.  —  The  neutral  borate  or  metaborate,  B02Na,  or  B203.ONa2, 
is  formed  by  fusing  common  borax  and  sodium  carbonate  in  equivalent 
proportions,  and  dissolving  the  mass  in  water.  It  forms  large  crystals 
containing  B02Na.30H2. 

The  Anhydroborate,  Biborate,  or  Borax,  2B02Na.B203.100H2  =  2B203.ONa2. 
100 H2,  occurs  in  the  waters  of  certain  lakes  in  Thibet  and  Persia:  it  is  im- 
ported in  a  crude  state  from  the  East  Indies  under  the  name  of  tim-al. 
When  purified  it  constitutes  the  borax  of  commerce.  Much  borax  is  now, 
however,  manufactured  from  the  native  boric  acid  of  Tuscany,  and  also 
from  a  native  calcium  borate  called  hayesine,  which  occurs  in  southern  Peru. 
Borax  crystallizes  in  six-sided  prisms,  which  effloresce  in  dry  air,  and  require 
20  parts  of  cold,  and  6  of  boiling  water  for  solution.  Exposed  to  heat,  the  10 
molecules  of  water  of  crystallization  are  expelled,  and  at  a  higher  tempera- 
ture the  salt  fuses,  and  assumes  a  glassy  appearance  on  cooling :  in  this 
state  it  is  much  used  for  blowpipe  experiments,  the  metallic  oxides  dissolv- 
ing in  it  to  transparent  beads,  many  of  which  are  distinguished  by  charac- 
teristic colors.  By  particular  management,  crystals  of  borax  can  be  ob- 
tained with  5  molecules  of  water:  they  are  very  hard,  and  permanent  in 
the  air.  Although  by  constitution  an  acid  salt,  borax  has  an  alkaline 
reaction  to  test-paper,  it  is  used  in  the  arts  for  soldering  metals,  its 
action  consisting  in  rendering  the  surfaces  to  be  joined  metallic,  by  dis- 
solving the  oxides,  and  it  sometimes  enters  into  the  composition  of  the 
glaze  with  which  stoneware  is  covered. 

SODIUM  SULPHIDE,  SNa2. — Prepared  in  the  same  manner  as  potassium 
monosiilphide :  it  separates  from  a  concentrated  solution  in  octohedral 
crystals,  which  are  rapidly  decomposed  by  contact  with  the  air  into  a  mix- 
ture of  sodium  hydrate  and  hyposulphite.  It  forms  double  sulphur-salts 
with  hydrogen  sulphide,  carbon  bisulphide,  and  other  sulphur-acids. 

Sodium  sulphide  is  supposed  to  enter  into  the  composition  of  the  beauti- 
ful pigment  ultramarine,  which  is  prepared  from  the  lapis  lazuli,  and  is  now 
imitated  by  artificial  means.  An  intimate  mixture  of  37  kaolin,  15  sodium 
sulphate,  22  sodium  carbonate,  18  sulphur,  and  8  charcoal,  is  heated  from 
twenty-four  to  thirty  hours  in  large  crucibles.  The  product  thus  obtained 
is  again  heated  in  cast-iron  boxes  at  a  moderate  temperature  till  the  re- 
quired tint  is  obtained.  After  being  finely  pulverized,  washed  and  dried, 


310 


MONAD    METALS. 


it  constitutes  commercial  ultramarine.       The    composition  of  this   color 
varies,  and  its  true  constitution  is  not  known. 


There  is  no  good  precipitant  for  sodium,  all  its  salts  being  very  soluble, 
with  the  exception  of  the  metantimonate,  which  is  precipitated  on  mixing  a 
solution  of  a  sodium  salt  with  a  solution  of  potassium  metantimonate;  the 
use  of  this  reagent  is,  however,  attended  with  some  difficulties.  The  pres- 
ence of  sodium  is  often  determined  by  negative  evidence.  The  yellow 
color  imparted  by  sodium  salts  to  the  outer  flame  of  the  blowpipe,  and  to 
combustible  matter,  is  a  character  of  considerable  importance.  The  spec- 
tral phenomena  exhibited  by  sodium  compounds  are  mentioned  on  page  88. 


AMMONIUM. 

The  ammonia  salts  are  most  conveniently  studied  in  this  place,  on  account 
of  their  close  analogy  to  those  of  potassium  and  sodium.  These  salts  are 
formed  by  the  direct  union  of  ammonia  NH3  with  acids,  and  as  already 
pointed  out  (p.  163),  they  may  be  regarded  as  compounds  of  acid  radicals, 
Cl,  N03,  S04,  &c.,  with  a  basylous  radical  NH4,  called  ammonium,  which 
plays  in  these  salts  the  same  part  as  potassium  and  sodium  in  their  respec- 
tive compounds ;  thus: 


NH3 

Ammonia. 

NH3 

NH3 

2NH, 


-f  HC1 

Hydrochloric 
acid. 

-f  HN03 

Nitric 
acid. 

+          H2S04 

Sulphuric 
acid. 


NH4.C1 

Ammonium 
chloride. 

NH4.N03 

Ammonium 
nitrate. 


NH4.H.S04 

Acid  ammoniuD 


onium 
sulphate. 


H2S04  (NH4)2.S04 

Neutral  ammonii 


.en  <uiimonium 
sulphate. 


The  radical  NH4  is  not  capable  of  existing  in  the  free  state,  inasmuch  as 
it  contains  an  uneven  number  of  monad  atoms :  it  is  simply  the  residue 
which  is  left  on  removing  the  atom  of  chlorine  from  the  saturated  molecule 

NH4 
NVH4C1.     Whether  the  double  molecule  N2H8,  or  |      ,  has  a  separate  exist- 

NH4 

ence,  is  a  different  question.  Ammonium  appears,  indeed,  to  be  capable 
of  forming  an  amalgam  with  mercury ;  but  even  in  this  state  it  is  quickly 
resolved  into  ammonia  and  free  hydrogen. 

When  a  globule  of  mercury  is  placed  on  a  piece  of  moistened  potassium 
hydrate,  and  connected  with  the  negative  side  of  a  voltaic  battery  of  very 
moderate  power,  the  circuit  being  completed  through  the  platinum  plate 
upon  which  the  alkali  rests,  decomposition  of  the  latter  takes  place,  and 
an  amalgam  of  potassium  is  rapidly  formed.  If  this  experiment  be  now 
repeated  with  a  piece  of  sal-ammoniac  instead  of  potassium  hydrate,  a 
soft,  solid,  metalline  mass  is  also  produced,  which  has  been  called  the 
ammoniacal  amalgam,  and  considered  to  contain  ammonium  in  combination 
with  mercury.  A  simpler  method  of  preparing  this  compound  is  the  follow- 
ing: A  little  mercury  is  put  into  a  test-tube  with  a  grain  or  two  of  potas- 
sium or  sodium,  and  gentle  heat  applied ;  combination  ensues,  attended  by 


AMMONIUM.  oil 

beat  and  light.  When  cold,  the  fluid  amalgam  is  put  into  a  capsule,  and 
covered  with  a  strong  solution  of  sal-ammoniac.  The  production  of  an 
ammoniacal  amalgam  instantly  commences,  the  mercury  increasing  pro- 
digiously in  volume,  and  becoming  quite  pasty.  The  increase  of  weight  is, 
however,  quite  trifling:  it  varies  from  yJ^  to  T^  part.  Left  to  itself, 
the  amalgam  quickly  decomposes  into  fluid  mercury,  ammonia,  and  hydro- 
gen ;  it  is  quite  possible,  indeed,  that  the  so-called  amalgam  may  he  nothing 
more  than  mercury  which  has  absorbed  a  certain  quantity  of  these  gases. 
just  as  silver,  when  heated  to  a  very  high  temperature,  is  capable  of  taking 
up  about  twenty  times  its  volume  of  oxygen  gas,  which  it  gives  up  again 
on  cooling. 

The  following  experiments  lately  made  by  Weyl«  afford  somewhat  stronger 
evidence  in  favor  of  the  separate  existence  of  ammonium.  When  lumps  of 
pure  bright  sodium  are  placed  at  one  end  of  a  bent  tube,  a  quantity  of 
silver  chloride  previously  saturated  with  ammonia-gas  at  the  other,  the 
tube  then  sealed,  the  end  containing  the  silver-chloride  heated  in  a  bath  of 
calcium  chloride,  and  the  other  end  immersed  in  cold  water,  the  sodium 
swells  up,  and  is  converted  into  a  liquid,  which  is  copper-red  by  perpen- 
dicularly reflected,  greenish-yellow  by  obliquely  reflected  light,  blue  in 
thin  films  by  transmitted  light.  This  liquid  is  sodammonium  N2H6Na2,  that 
is,  ammonium  N2H8  having  two  of  its  hydrogen  atoms  replaced  by  sodium. 
As  the  silver-chloride  cools,  and  the  ammonia-gas  is  reabsorbed,  the  sodam- 
monium decomposes  and  pure  sodium  remains  behind,  having  a  dull  surface 
and  spongy  texture.  By  again  heating  the  silver-chloride,  the  compound 
may  be  reproduced  any  number  of  times. 

Potassammonium,  N2H6K2?,  is  prepared  like  sodammonium,  and  exhibits 
similar  properties. 

Other  metallammoniums  may  be  produced  by  the  decomposition  of  so- 
dium- or  potass-ammonium.  Thus  when  a  mixture  of  a  metallic  chloride  or 
oxide  with  an  equivalent  quantity  of  sodium  is  exposed  in  the  manner 
above  described  to  the  action  of  ammonia-gas,  the  gas  is  first  absorbed  by 
the  metallic  chloride  (or  oxide)  and  afterwards  by  the  sodium,  the  sodam- 
monium thus  formed  flowing  over  the  metallic  salt,  and  reacting  upon  it 
without  much  rise  of  temperature.  With  a  mixture  of  barium-chloride 
and  sodium  the  reaction  appears  to  be : 

N2H6Na2    -f     2NH3    -f     Ba"Cl2     =     N2H6Ba"    -f     2NH,NaCl. 

'   Sodaramonium.  Baraimaonium.  Chloride  of 

Sodammonium. 

Barammonium  forms  a  deep  blue  liquid  having  a  metallic  lustre. —  Cop- 
per-, Mercury-,  and  Silver- ammonium  are  obtained  in  like  manner  from  the 
respective  chlorides,  and  Zinc- ammonium  from  the  oxide.  These  compounds 
are  likewise  very  unstable,  being  resolved,  even  in  the  sealed  tube,  into 
metal  (which  appears  gray,  dull,  and  destitute  of  coherence)  and  ammonia. 
If  in  the  arrangement  just  described  the  metallic  chloride  be  replaced  1>\- 
an  ammonium-salt,  e.g.,  NH4C1  or  (NH4)2S04,  similar  reactions  take  place, 
and  the  tube  becomes  filled  with  a  blue  liquid  mixed  with  excess  of  am- 
monia. This  blue  liquid,  which  is  also  formed  by  the  action  of  potassium 
hydrate  on  potassammonium,  appears  to  consist  of  ammonium  itself.  N?IU 
It  is  even  more  unstable  than  the  metallammoniums,  being  resolved  into 
ammonia  and  hydrogen,  partly  even  before  the  reaction  between  the  am- 
monium-salt and  the  sodammonium  is  completed. 

But  whether  ammonium  has  any  separate  existence  or  not,  it  is  quite 
certain  that  many  ammoniacal  salts  are  isornorphous  with  those  of  potas- 
sium; and  if  from  any  two  of  the  corresponding  salts,  as  the  nitrates, 

*  Pogg.  Ann.  cxxi.  697. 


312  MONAD    METALS. 

KN03  and  NH4N03,  we  subtract  the  radical  N03  common  to  the  two,  there 
remain  the  metal  K  and  the  group  NH4,  which  are,  therefore,  supposed  to 
be  isomorphous. 

AMMONIUM  CHLORIDE,  SAL-AMMONIAC,  NH4C1.  —  Sal-ammoniac  was  for- 
merly obtained  from  Egypt,  being  extracted  by  sublimation  from  the  soot 
of  camels'  dung:  it  is  now  largely  manufactured  from  the  ammoniacal 
liquid  of  the  gas-works,  and  from  the  condensed  products  of  the  distillation 
of  bones,  and  other  animal  refuse,  in  the  preparation  of  animal  charcoal. 

These  impure  and  highly  offensive  solutions  are  treated  with  a  slight  ex- 
cess of  hydrochloric  acid,  by  which  the  free  alkali  is  neutralized,  and  the 
carbonate  and  sulphide  are  decomposed,  with  evolution  of  carbonic  acid 
and  sulphuretted  hydrogen  gases.  The  liquid  is  evaporated  to  dryness, 
and  the  salt  carefully  heated,  to  expel  or  decompose  the  tarry  matter;  it 
is  then  purified  by  sublimation  in  large  iron  vessels  lined  with  clay,  sur- 
mounted with  domes  of  lead. 

Sublimed  sal-ammoniac  has  a  fibrous  texture ;  it  is  tough,  and  difficult 
to  powder. 

When  crystallized  from  water  it  separates,  under  favorable  circumstances, 
in  distinct  cubes  or  octohedrons  ;  but  the  crystals  are  usually  small,  and  ag- 
gregated together  in  rays.  It  has  a  sharp  saline  taste,  and  is  soluble  in  2| 
parts  of  cold,  and  in  a  much  smaller  quantity  of  hot  water.  By  heat,  it  is 
sublimed  without  decomposition.  The  crystals  are  anhydrous.  Ammonium 
chloride  forms  double  salts  with  the  chlorides  of  magnesium,  nickel,  cobalt, 
iron,  manganese,  zinc,  and  copper. 

AMMONIUM  NITRATE,  N03(NH4),  is  easily  prepared  by  adding  ammonium 
carbonate  to  slightly  diluted  nitric  acid  until  neutralization  has  been  reached. 
By  slow  evaporation  at  a  moderate  temperature  it  crystallizes  in  six-sided 
prisms,  like  those  of  potassium  nitrate ;  but,  as  usually  prepared  for  making 
nitrogen  monoxide,  by  quick  boiling  until  a  portion  solidifies  completely  on 
cooling,  it  forms  a  fibrous  and  indistinct  crystalline  mass. 

Ammonium  nitrate  dissolves  in  two  parts  of  cold  water,  producing  con- 
siderable depression  of  temperature ;  it  is  but  feebly  deliquescent,  and 
deflagrates  like  nitre  on  contact  with  heated  combustible  matter.  Its  decom- 
position by  heat  has  been  already  explained  (p.  159). 

AMMONIUM  SULPHATE,  S04(NH4)2. — Prepared  by  neutralizing  ammonium 
carbonate  with  sulphuric  acid,  or  on  a  large  scale,  by  adding  sulphuric  acid 
in  excess  to  the  coal-gas  liquor  just  mentioned,  and  purifying  the  product 
by  suitable  means.  It  is  soluble  in  2  parts  of  cold  water,  and  crystallizes 
in  long,  flattened,  six-sided  prisms.  It  is  entirely  decomposed,  and  driven 
off  by  ignition,  and,  even  to  a  certain  extent,  by  long  boiling  with  water, 
ammonia  being  expelled  and  the  liquid  rendered  acid. 

AMMONIUM  CARBONATES.  —  H.  Rose  admits  the  existence  of  a  considerable 
number  of  these  salts,  to  which  he  assigns  very  complicated  formulas;  but, 
according  to  H.  Sainte  Claire-Deville,*  there  exist  only  two  ammonium 
carbonates  of  definite  composition,  namely  : 

(a  )  Ammonium  and  Hydrogen  Carbonate,  or  Mono-ammonic  Carbonate, 
C03(NH4)H,  commonly  called  Bicarbonate,  or  Acid  carbonate  of  ammonia. — 
This  salt  is  obtained  by  saturating  an  aqueous  solution  of  ammonia,  or  of 
the  sesquicarbonate,  with  carbonic  acid  gas ;  or  by  treating  the  finely  pounded 
sesquicarbonate  with  strong  alcohol,  which  dissolves  out  normal  or  diam- 
monic  carbonate,  leaving  a  residue  of  the  mono-amtnonic  salt.  Cold  water 
may  be  used  instead  of  alcohol  for  this  purpose ;  but  it  dissolves  a  larger 

*  Ann.  Chim.  Phys.  [3]  xl.  87. 


AMMONIUM. 

quantity  of  the  mono-ammonic  carbonate.  All  ammonium-carbonates  when 
left  to  themselves  are  gradually  converted  into  mono-amrnonic  csirbnnnti-. 
This  salt  forms  large  crystals  belonging  to  the  trimetric  system.  According 
to  Deville  it  is  dimorphous,  but  never  isomorphous  with  monopotassic  car- 
bonate;  when  exposed  to  the  air,  it  volatilizes  slowly,  ami  gives  off  a  faint 
ammoniacal  odor.  It  dissolves  in  8  parts  of  cold  water,  the  solution  decom- 
posing gradually  at  ordinary  temperatures,  quickly  when  heated  above  30° 
C.  (86°  F.)  with  evolution  of  ammonia.  It  is  insoluble  in  alcohol,  but  when 
exposed  to  the  air,  under  alcohol,  it  dissolves  as  normal  carbonate,  evolving 
carbon  dioxide. 

It  has  been  found  native  in  considerable  quantity  in  the  deposits  of  guano, 
on  the  western  coast  of  Patagonia,  in  white  crystalline  masses,  having  a 
strong  ammoniacal  odor. 

(6.)  Tetrammonio-dihydric  Carbonate,  C309N4H,8  =  (C03)3(NH4)4H2.  —  This 
salt,  commonly  called  sesqui-carbonate  of  ammonia,  contains  the  elements  of  1 
molecule  of  diammonic  and  2  molecules  of  mono-ammonic  carbonate,  into 
which  it  is,  in  fact,  resolved  by  treatment  with  water  or  alcohol : 

(C03)3(NH4)4H2    =     C03(NH4)2    +     2[(CO,(NH4)H]. 

It,  is  obtained  by  dissolving  the  commercial  carbonate  in  strong  aqueous 
ammonia,  at  about  30°  C.  (86°  F.)  and  crystallizing  the  solution.  It  forms 
large  transparent  rectangular  prisms,  having  their  summits  truncated  by 
octohedral  faces.  These  crystals  decompose  very  rapidly  in  the  air,  giving 
off  water  and  ammonia,  and  being  converted  into  mono-ammonic  carbonate. 
The  normal  or  diammonic  carbonate,  C03(NH4)2,  has  not  been  obtained  in 
the  solid  state.  Commercial  carbonate  of  ammonia  (sal  volatile,  salt  of  harts- 
horn) consists  of  sesqui-carbonate  more  or  less  pure.  It  is  prepared  on  the 
large  scale  by  the  dry  distillation  of  bones,  hartshorn,  and  other  animal  mat- 
ter, and  is  purified  from  adhering  empyreumatic  oil  by  subliming  it  once  or 
twice  with  animal  charcoal  in  cast-iron  vessels,  over  which  glass  receivers 
are  inverted.  Another  method  consists  in  heating  to  redness  a  mixture  of 
1  part  ammonium  chloride  or  sulphate,  and  2  parts  calcium  carbonate 
(chalk),  or  potassium  carbonate,  in  a  retort,  to  which  a  receiver  is  luted.* 

AMMONIUM  SULPHIDES.  —  Several  of  these  compounds  exist,  and  may  be 
formed  by  distilling  with  sal-ammoniac  the  corresponding  sulphides  of 
potassium  or  sodium. 

Ammonium  and  Hydrogen  Sulphide,  or  Ammonium  Sulph-hydrate,  S(NH4)H, 
is  a  compound  of  great  practical  utility ;  it  is  obtained  by  saturating  a  solu- 
tion of  ammonia  with  well-washed  sulphuretted  hydrogen  gas,  until  no 
more  of  the  latter  is  absorbed.  The  solution  is  nearly  colorless  at  first,  but 
becomes  yellow  after  a  time,  without,  however,  suffering  material  injury, 
unless  it  has  been  exposed  to  the  air.  It  gives  precipitates  with  most  metal 
lie  solutions,  which  are  very  often  characteristic,  and  is  of  great  service 
in  analytical  chemistry. 

Ammoniacal  salts  are  easily  recognized  ;  they  are  all  decomposed  or  vola- 
tilized at  a  high  temperature;  and  when  heated  with  calcium  hydrate  or 
solution  of  alkaline  carbonate,  they  give  off  ammonia,  which  may  be  recog- 

[*  Diammnnio-hydric  Phosphate;  Ommon  Tribasic  Phosphate,  P04,  2(NH4)II.OII2.— This  salt 
is  prepared  by  precipitating  the  acid  calcium  phosphate,  with  an  excess  of  the  COmBCVOlal  am- 
monium carbonate  and  evaporating  at  a  moderate  temperature.  It  crystalli/es  in  rix-OdM 
tables  derived  from  oblique  quadrangular  prisms  The  crystals  dissolve  in  4  parts  of  water  and 
in  alcohol.  They  are  efflorescent,  have  a  saline,  alkaline  last-  and  alkaline  reaction.  The  acid 
tribasin  phosphate  P04.NH4.Ho.40H  is  forme.]  when  a  solution  of  the  common  is  boiled  as  long 
as  ammonia  is  given  off.  It  crystallizes  in  4-sided  prisms,  which  are  permanent  s,,l,,M.-  in  five 
parts  of  water  and  have  an  acid' taste  and  reaction.  When  ammonia  in  excess  is  added  (,,  either 
of  these  salts,  the  triammouic  phosphate  P043(NH4)  is  deposited  as  a  granular  precipitate  — U.  B.J 
21 


314  MONAD    METALS. 

nized  by  its  odor  and  alkaline  reaction.  The  salts  are  all  more  or  less 
soluble  ;  the  acid  tartrate  and  the  platinochloride  being,  however,  among 
the  least  soluble ;  hence  ammonium  salts  cannot  be  distinguished  from 
potassium  salts  by  the  tests  of  tartaric  acid  and  platinum  solution.  When 
a  solution  containing  an  ammoniacal  salt,  or  free  ammonia,  is  mixed  with 
patash,  and  a  solution  of  mercuric  iodide  in  potassium  iodide  is  added,  a  brown 
precipitate  or  coloration  is  immediately  produced,  consisting  of  dimercur- 
ammonium  iodide,  NHg2/xI : 

NH3  -\-  2Hg"I2  =  NHg"2I  +  SHI. 

This  is  called  Nessler's  test ;  it  is  by  far  the  most  delicate  test  for  ammonia 
that  is  known. 

Amic  Acids  and  Amides. 

SULPHAMIC  ACID.  — When  dry  ammonia  gas  is  passed  over  a  thin  layer 
of  sulphuric  oxide  S03,  the  gas  is  absorbed,  and  a  white  crystalline  powder 
is  formed,  having  the  composition  N2H6S03,  that  is,  of  ammonium  sulphate 
minus  one  molecule  of  water : 

N2H6S03  ==  S04  (NH4)2  —  OH2. 

It  is  not,  however,  a  salt  of  sulphuric  acid :  for  its  aqueous  solution  does 
not  give  any  precipitate  Avith  baryta-water  or  soluble  barium  salts.  It  is, 
in  fact,  the  ammonium  salt  of  sulphamic  acid,  an  acid  derived  from  sulphuric 
acid,  S04H2  or  S02(HO)2,  by  substitution  of  the  univalent  radical  NH2*  for 
one  atom  of  hydroxyl,  HO.  The  formula  of  this  acid  is  S03(NH2)H,  and 
that  of  its  ammonium  salt,  S03(NH2)NH4,  or  S03N2H6.  Ammonium  sul- 
phamate  is  permanent  in  the  air,  and  dissolves  without  decomposition  in 
water.  Its  solution,  evaporated  in  a  vacuum,  over  oil  of  vitriol,  yields  the 
salt  in  transparent  colorless  crystals. 

The  solution  of  the  ammonium  salt,  mixed  with  baryta-water,  gives  off 
ammonia,  and  yields  a  solution  of  barium  sulphamate,  (S03NH2)2Ba//,  which 
may  be  obtained  by  evaporation  in  well  defined  crystals ;  and  the  solution 
of  this  salt,  decomposed  with  potassium  sulphate,  yields  pataseium  sul- 
phamate, S03NH2K. 

CARBAMIC  ACID.  — When  dry  ammonia  gas  is  mixed  with  carbon  dioxide, 
the  mixture  being  kept  cool,  the  gases  combine  in  the  proportion  of  2 
volumes  of  the  former  to  1  volume  of  the  latter,  forming  a  pungent,  very 
volatile  substance,  which  condenses  in  white  flocks.  This  substance  has 
the  composition  C02N2H6,  that  is,  of  normal  ammonium  carbonate,  C03 
(NH4)2,  minus  one  molecule  of  water.  It  was  formerly  called  anhydrous  car- 
bonate of  ammonia;  but,  like  the  preceding  salt,  is  not  really  a  carbonate, 
but  the  ammonium  salt  of  carbamic  acid,  C02(NH2)H,  derived  from  carbonic 
ncid,  C03H2  or  CO(OH)2,  by  substitution  of  amidogen  NH2  for  1  atom  of 
hydroxyl.  Ammonium  carbamate  dissolves  readily  in  water,  and  quickly 
takes  up  one  molecule  of  that  compound,  whereby  it  is  converted  into  am- 
monium carbonate,  When  treated  with  sulphuric  oxide,  it  is  converted  into 
ammonium  sulphamate. 

CARBAMIDE,  CON2H4.  —  When  ammonia  gas  is  mixed  with  carbon  oxy- 
chloride  or  phosgene  gas,  COC12,  a  white  crystalline  powder  is  formed, 
having  th.is,  composition : 

COC12  -f  2NHa  =  2HC1  -f  CON2H4. 

This  compound,  which  is  likewise  formed  in  other  reactions  to  be  after- 
wards considered,  is  4eriyed  from  carbonic  acid,  CO(OH)2,  by  substitution 

*  See  page  237. 


AMMONIUM.  315 

of  2  atoms  of  amidogen  for  2  atoms  of  hydroxyl.  It  differs  from  carbamic 
acid  in  being  a  neutral  substance,  not  containing  any  hydrogen  easily  re- 
placeable by  metals. 

Other  bibasic  acids  likewise  yield  an  amic  acid  and  a  neutral  amide  by 
substitution  of  1  or  2  atoms  of  amidogen  for  hydroxyl.  Tribasic  acids 
yield  in  like  manner  two  amic  acids  and  one  neutral  amide,  and  tetrabasic 
acids  may  yield  three  arnic  acids  and  a  neutral  amide  ;  thus,  from  pyro- 

fhosphoric  acid,  P.207H4  =  P.O.(HO4),  are  obtained  the  three  amic  acids 
'206(NH2)H3,  P205(NH2)2H2,  and  P204(NH2)H. 

Monobasic  acids,  which  contain  but  one  atom  of  hydroxyl,  yield  by  this 
mode  of  substitution  only  neutral  amides,  no  amic  acids:  thus,  from  acetic 
acid,  C2H402  =  C2H302.HO,  is  obtained  acetamide,  C?H30(NH2). 

The  neutral  amides  may  also  be  regarded  as  derived  from  one  or  more 
molecules  of  ammonia,  by  substitution  of  univalent  or  multivalent  acid 
radicals,  for  hydrogen;  thus,  acetamide  =  N///H.(C.H30) ;  carbamide 
NX//H  (CO)",  &c. 

By  similar  substitution  of  metals,  or  basylous  compound  radicals  for  the 
hydrogen  of  ammonia,  basic  compounds,  called  amines,  are  formed.  Thus, 
when  potassium  is  gently  heated  in  ammonia  gas,  monopotassamine,  NH2K, 
is  formed.  It  is  an  olive-green  substance,  which  is  decomposed  by  water 
into  ammonia  and  potassium  hydrate: 

NH2K  4-  OH2  =  NH3  +  OKH. 

It  melts  at  a  little  below  100°,  and  when  heated  in  a  close  vessel,  is  resolved 
into  ammonia  and  tripotassamine : 

3NH2K  =  2NH3  -f  NK3. 

The  latter  effervesces  violently  with  water,  yielding  ammonia  and  potas- 
sium hydrate : 

NK3  +  30H2  =  NH3  4-  30KH. 

The  formation  and  properties  of  amides  and  amines  will  be  further  con- 
sidered under  Organic  Chemistry. 

METALLAMMONIUMS. — We  have  already  spoken  of  the  formation  of  com- 
pounds which  may  be  regarded  as  derived  from  ammonium,  N2H8,  by  sub- 
stitution of  metals  for  hydrogen:  e.g.  sodammonium,  N2H6Na2.  Salts  of 
such  radicals  are  also  formed  in  several  ways.  Ammonia  gas  is  absorbed 
by  various  metallic  salts  in  different  proportions,  forming  compounds,  some 
of  which  may  be  formulated  as  salts  of  inetallammoniums.  Thus,  platinum 
dichloride,  Ptd2,  absorbs  two  molecules  of  ammonia,  forming  platosammo- 
nium  chloride,  N2H6Pt//.Cl2;  and  platinum  tetrachloride,  PtlTCl4,  absorbs 
four  molecules  of  ammonia,  forming  platinammonium  chloride,  N4H|2PtiT.Cl4 
In  like  manner,  cupric  chloride  and  sulphate  form  the  chloride  and  sulphate 
of  cuprammonium,  ILl^Ca''.^  and  N^Cu^-SO,,. 

Similar  compounds  are  formed  in  many  cases  by  precipitating  metallic 
salts  with  ammonia  or  ammoniacal  salts:  thus,  ammonia  added  to  a  solution 
of  mercuric  chloride,  HgCl2,  forms  a  white  precipitate,  consisting  of  diinrr- 
curammonium  chloride,  N2H4Hg//2.Cl2;  and  by  dropping  a  solution  of  mer- 
curic chloride  into  a  boiling  solution  of  sal-ammoniac  mixed  with  free  am- 
monia, crystals  are  obtained,  consisting  of  mer -cur -ammonium  chloride,  N2H4 
Hg//.Cl2.  Some  of  these  compounds  will  be  further  considered  in  con- 
nection with  the  several  metals. 


316  MONAD    METALS. 


LITHIUM. 

Atomic  weight,  7.     Symbol,  Li. 

Lithium  is  found  in  petalite,  spocUimene,  lepidolite,  triphylline,  and  a 
few  other  minerals,  and  sometimes  occurs  in  minute  quantities  in  mineral 
springs. 

The  metal  is  obtained  by  fusing  pure  lithium  chloride  in  a  small  thick 
porcelain  crucible,  and  decomposing  the  fused  chloride  by  electricity.  It 
is  a  white  metal  like  sodium,  and  very  oxidizable.  Lithium  fuses  at  180° 
C.  (356°  F.);  its  specific  gravity  is  0-59:  it  is,  therefore,  the  lightest  solid 
known. 

A  lithium  salt  may  be  obtained  from  petalite  on  the  small  scale,  by  the 
following  process:  The  mineral  is  reduced  to  an  exceedingly  fine  powder, 
mixed  with  five  or  six  times  its  weight  of  pure  calcium  carbonate,  and  the 
mixture  heated  to  whiteness,  in  a  platinum  crucible  placed  within  a  well 
covered  earthen  one,  for  twenty  minutes  or  half  an  hour.  The  shrunken 
coherent  mass  is  digested  in  dilute  hydrochloric  acid,  the  whole  evaporated 
to  dryness,  acidulated  water  added,  and  the  silica  separated  by  a  filter. 
The  solution  is  then  mixed  with  ammonium  carbonate  in  excess,  boiled, 
and  filtered;  the  clear  liquid  is  evaporated  to  dryness,  and  gently  heated 
in  a  platinum  crucible,  to  expel  the  sal-ammoniac ;  and  the  residue  is 
wetted  with  oil  of  vitriol,  gently  evaporated  once  more  to  dryness,  and 
ignited :  pure  fused  lithium  sulphate  then  remains. 

This  process  will  serve  to  give  a  good  idea  of  the  general  nature  of  the 
operation  by  which  alkalies  are  extracted  in  mineral  analysis,  and  their 
quantities  determined. 

Lithium  hydrate,  LiHO,  is  much  less  soluble  in  water  than  the  hydrates 
of  potassium  and  sodium ;  the  carbonate  and  phosphate  are  also  sparingly 
soluble  salts.  The  chloride  crystallizes  in  anhydrous  cubes  which  are  deli- 
quescent. Lithium  sulphate  is  a  very  beautiful  salt ;  it  crystallizes  in  length- 
ened prisms  containing  one  molecule  of  water.  It  gives  no  double  salt 
with  aluminium  sulphate. 

The  salts  of  lithium  color  the  outer  flame  of  the  blowpipe  carmine-red. 
The  spectral  phenomena  exhibited  by  lithium  compounds  are  mentioned 
on  page  89. 


CESIUM  AND  RUBIDIUM. 
Cs  =  133.  —  Rb  =  85-4. 

The  two  metals  designated  by  these  names  were  discovered  by  Bunsen 
and  Kirchhoff  by  means  of  their  spectrum  apparatus  mentioned  on  page 
88:  the  former  in  1860  and  the  latter  in  1861.  These  metals,  it  appears, 
are  widely  diffused  in  nature,  but  always  occur  in  very  small  quantities  ; 
they  have  been  detected  in  many  mineral  waters,  as  well  as  in  some  min- 
erals, namely,  lithia-mica  or  lepidolite,  and  petalite;  lately  also  in  fel- 
spar; they  have  also  been  found  in  the  alkaline  ashes  of  the  beet-root. 
The  brine  of  Diirkheim  has  up  to  the  present  moment  been  the  richest 
source  of  caesium.  The  best  material  for  the  preparation  of  rubidium,  is 
lepidolite,  which  has  been  found  to  contain  as  much  as  0-2  per  cent,  of 
that  metal.  Both  metals  are  closely  analogous  to  potassium"  in  their  de- 
portment, and  cannot  be  distinguished  from  that  metal  or  from  one  another, 
either  by  reagents  or  before  the  blowpipe. 


SILVER.  317 

Rubidium  and  cesium,  like  potassium,  form  double  salts  with  tetra- 
chloride  of  platinum,  which  arc,  however,  much  more  insoluble  than  tho 
corresponding  potassium  salts:  it  is  on  this  property  that  the  separation 
of  these  metals  from  potassium  is  based.  The  mixture  of  platinochlorides 
is  repeatedly  extracted  with  boiling  water,  when  a  difficultly  soluble  re- 
sidue, consisting  chiefly  of  the  platinochlorides  of  caesium  and  rubidium, 
remains. 

The  hydrates  of  these  new  metals  are  powerful  bases,  which  attract  car- 
bonic acid  from  the  air,  passing,  first  into  normal  carbonate  and  then  into 
acid  carbonate.  Caesium  carbonate  is  soluble  in  absolute  alcohol;  rubi- 
dium carbonate  is  nearly  insoluble  in  that  liquid:  this  property  is  made 
use  of  for  the -separation  of  these  two  metals.  The  chloride  crystallizes 
in  cubes,  and  is  somewhat  more  soluble  in  water  than  chloride  of  potas- 
sium. 

Rubidium  chloride,  when  in  a  state  of  fusion,  is  easily  decomposed  by 
the  electric  current ;  the  metal  produced  rises  to  the  surface  and  burns 
with  a  reddish  light.  If  this  experiment  be  performed  in  an  atmosphere 
of  hydrogen,  to  prevent  oxidation,  the  separated  metal  is  nevertheless  lost, 
dissolving  as  it  does  in  the  fused  chloride,  which  is  transformed  into  a 
subchloride  having  the  blue  color  of  smalt.  Rubidium,  when  separated 
under  mercury  by  the  electric  current,  forms  a  crystalline  amalgam  of  sil- 
very lustre,  which  is  rapidly  oxidized  by  the  air,  and  decomposes  water  in 
the  cold.  Caesium  chloride,  under  the  influence  of  the  electric  current, 
exhibits  exactly  the  same  deportment  as  rubidium  choride.  Rubidium  is 
electro-positive  towards  potassium,  caesium  is  electro-positive  towards  ru- 
bidium and  potassium,  and  thus  constitutes  the  most  electro-positive  member 
of  the  elements. 


SILVER. 

Atomic  weight,  108.     Symbol,  Ag  (Argentum). 

Silver  is  found  in  the  metallic  state,  as  sulphide,  in  union  with  sulphide 
of  antimony  and  sulphide  of  arsenic,  also  as  chloride,  iodide,  and  bromide. 
Among  the  principal  silver  mines  may  be  mentioned  those  of  the  Hartz 
mpuntains  in  Germany,  of  Kongsberg  in  Norway,  and,  more  particularly, 
of  the  Andes,  in  both  North  and  South  America. 

The  greater  part  of  the  silver  of  commerce  is  extracted  from  ores  so  poor 
as  to  render  any  process  of  smelting  or  fusion  inapplicable,  even  where  fuel 
could  be  obtained,  and  this  is  often  difficult  to  be  procured.  Recourse, 
therefore,  is  had  to  another  method  —  that  of  amalgamation  —  founded  on 
the  easy  solubility  of  silver  and  many  other  metals  in  metallic  mercury. 

The  amalgamation  process  adopted  in  Germany — which  differs  somewhat 
from  that  in  use  in  America  —  is  as  follows:  The  ore  is  crushed  to  powder, 
mixed  with  a  quantity  of  common  salt,  and  roasted  at  a  low  red  heat  in  a 
suitable  furnace,  by  which  treatment  any  sulphide  of  silver  it  may  contain 
is  converted  into  chloride.  The  mixture  of  earthy  matter,  oxides  of  iron, 
copper,  soluble  salts,  silver  chloride,  and  metallic  silver,  is  sifted  and  put 
into  large  barrels  made  to  revolve  on  axes,  with  a  quantity  of  water  and 
scraps  of  iron,  and  the  whole  is  agitated  together  for  some  time,  during 
which  the  iron  reduces  the  silver  chloride  to  the  state  of  metal.  A  certain 
proportion  of  mercury  is  then  introduced,  and  the  agitation  repeated:  the 
mercury  dissolves  out  the  silver,  together  with  gold,  if  there  be  any.  metnl- 
lic  copper,  and  other  substances,  forming  a  fluid  anial-rain  easily  separable! 
from  the  thin  mud  of  earthy  matter  by  subsidence  and  washing.  This 
amalgam  is  strained  through  a  strong  linen  cloth,  and  the  solid  portion 
27* 


318  MONAD    METALS. 

exposed  to  heat  in  a  kind  of  retort,  by  which  the  remaining  mercury  is 
distilled  off  and  the  silver  left  behind  in  an  impure  state. 

Considerable  loss  often  occurs  in  the  amalgamation  process  from  the  com- 
bination of  a  portion  of  the  mercury  with  sulphur,  oxygen,  &c.,  whereby 
it  is  brought  into  a  pulverulent  condition,  known  as  "flouring,"  and  is  then 
liable  to  be  washed  away,  together  with  the  silver  it  has  taken  up.  This 
inconvenience  may  be  prevented,  as  suggested  by  Mr.  Crookes,  by  amalga- 
mating the  mercury  with  1  or  2  per  cent,  of  sodium,  which  by  its  superior 
affinity  for  sulphur  and  oxygen,  prevents  the  mercury  from  becoming 
floured. 

A  considerable  quantity  of  silver  is  obtained  from  argentiferous  galena : 
in  fact,  almost  every  specimen  of  native  lead  sulphide  is  found  to  contain 
traces  of  this  metal.  When  the  proportion  rises  to  a  certain  amount,  it 
becomes  worth  extracting.  The  ore  is  reduced  in  the  usual  manner,  the 
whole  of  the  silver  remaining  with  the  lead  ;  the  latter  is  then  re-melted  in 
a  large  vessel,  and  allowed  to  cool  slowly  until  solidification  commences. 
The  portion  which  first  crystallizes  is  nearly  pure  lead,  the  alloy  with  silver 
being  more  fusible  than  lead  itself:  by  particular  management  this  is  drained 
away,  and  is  found  to  contain  nearly  the  whole  of  the  silver  [Pattinson's 
process].  This  rich  mass  is  next  exposed  to  a  red  heat  on  the  shallow 
hearth  of  a  furnace,  while  a  stream  of  air  is  allowed  to  impinge  upon  its 
surface ;  oxidation  takes  place  with  great  rapidity,  the  fused  oxide  or  lith- 
arge being  constantly  swept  from  the  metal  by  the  blast.  When  the  greater 
part  of  the  lead  has  been  thus  removed,  the  residue  is  transferred  to  a  cupel 
or  shallow  dish  made  of  bone-ashes,  and  again  heated:  the  last  portion  of 
the  lead  is  now  oxidized,  and  the  oxide  sinks  in  a  melted  state  into  the 
porous  vessel,  while  the  silver,  almost  chemically  pure,  and  exhibiting  a 
brilliant  surface,  remains  behind. 

Pure  silver  may  be  easily  obtained.  The  metal  is  dissolved  in  nitric  acid : 
if  it  contains  copper,  the  solution  will  have  a  blue  tint;  gold  will  remain 
undissolved  as  a  black  powder.  The  solution  is  mixed  with  hydrochloric 
acid  or  with  common  salt,  and  the  white,  insoluble,  curdy  precipitate  of  sil- 
ver chloride  is  washed  and  dried.  This  is  then  mixed  with  about  twice  its 
weight  of  anhydrous  sodium  carbonate,  and  the  mixture,  placed  in  an 
earthen  crucible,  is  gradually  raised  to  a  temperature  approaching  white- 
nes,  during  which  the  sodium  carbonate  and  the  silver  chloride  react  upon 
each  other ;  carbon  dioxide  and  oxygen  escape,  while  metallic  silver  and 
soda  chloride  result:  the  former  melts  into  a  button  at  the  bottom  of  the 
crucible,  and  is  easily  detached.  The  following  is  perhaps  the  most  simple 
method  for  the  reduction  of  silver  chloride.  The  silver-salt  is  covered  with 
water,  to  which  a  few  drops  of  sulphuric  acid  are  added ;  a  plate  of  zinc  is 
then  introduced.  The  silver  chloride  soon  begins  to  decompose,  and  is, 
after  a  short  time,  entirely  converted  into  metallic  silver ;  the  silver  thus 
obtained  is  gray  and  spongy;  it  is  ultimately  purified  by  washing  with 
slightly  acidulated  water. 

Pure  silver  has  a  most  perfect  white  color  and  a  high  degree  of  lustre : 
it  is  exceedingly  malleable  and  ductile,  and  is  probably  the  best  conductor 
both  of  heat  and  electricity  known.  Its  specific  gravity  is  10-5.  In  'hard- 
ness it  lies  between  gold  and  copper.  It  melts  at  a  bright  red  heat,  about 
1023°  C,  (1873°  F.),  according  to  the  observation  of  Mr.  Daniell.  Silver  is 
unalterable  by  air  and  moisture :  it  refuses  to  oxidize  at  any  temperature, 
but  possesses  the  extraordinary  faculty  already  noticed  of  absorbing  many 
times  its  volume  of  oxygen  when  strongly  heated  in  an  atmosphere  of  that 
gas,  or  in  common  air.  The  oxygen  is  again  disengaged  at  the  moment  of 
solidification,  and  gives  rise  to  the  peculiar  arborescent  appearance  often 
remarked  on  the  surface  of  masses  or  buttons  of  pure  silver.  The  addition 
of  2  per  cent,  of  copper  is  sufficient  to  prevent  the  absorption  of  oxygen. 


SILVER.  319 

Silver  oxidizes  when  heated  with  fusible  siliceous  matter,  as  glass,  which  it 
stains  yellow  or  orange,  from  the  formation  of  a  silicate.  It  is  little  attacked 
by  hydrochloric  acid;  boiling  oil  of  vitriol  converts  it  into  sulphate,  with 
evolution  of  sulphurous  oxide;  nitric  acid,  even  dilute  and  in  the  cold,  dis- 
solves it  readily.  The  tarnishing  of  surfaces  of  silver  exposed  to  the  air  is 
due  to  hydrogen  sulphide,  the  metal  having  a  strong  attraction  for  sulphur. 

SILVER  CHLORIDES. — Two  of  these  compounds  are  known  containing  re- 
spectively 1  and  2  atoms  of  silver  to  1  atom  of  chlorine;  the  second,  how- 
ever, is  a  very  unstable  compound.* 

The  Monochloride  or  Argentic  Chloride,  Ag  Cl,  is  almost  invariably  pro- 
duced when  a  soluble  silver  salt  and  a  soluble  chloride  are  mixed.  It  falls 
as  a  white  curdy  precipitate,  quite  insoluble  in  water  and  nitric  acid;  but 
one  part  of  silver  chloride  is  soluble  in  200  parts  of  hydrochloric  acid  when 
concentrated,  and  in  about  600  parts  when  diluted  with  double  its  weight 
of  water.  When  heated  it  melts,  and  on  cooling  becomes  a  grayish  crys- 
talline mass,  which  cuts  like  horn :  it  is  found  native  in  this  condition, 
constituting  the  horn-silver  of  the  mineralogist.  Silver  chloride  is  decom- 
posed by  light,  both  in  the  dry  ;ind  in  the  wet  state,  very  slowly  if  pure, 
and  quickly  if  organic  matter  b"e"~]5resent. :  it  is  reduced  also  when  put  into 
water  with  metallic  zinc  or  iron.  It  dissolves  with  great  ease  in  ammonia 
and  in  a  solution  of  potassium  cyanide.  In  practical  analysis  the  propor- 
tion of  chlorine  or  hydrochloric  acid  in  a  compound  is  always  estimated 
by  precipitation  with  silver  solution.  The  liquid  is  acidulated  with  nitric 
acid,  and  an  excess  of  silver  nitrate  added;  the  chloride  is  collected  on  a 
filter,  or  better  by  subsidence,  washed,  dried,  and  fused ;  100  parts  corre- 
spond to  24-7  of  chlorine,  or  25-43  of  hydrochloric  acid. 

Argentous  Chloride,  Ag4Cl2,  is  obtained  by  treating  the  corresponding  oxide 
with  hydrochloric  acid  or  by  precipitating  an  argentous  salt,  the  citrate, 
for  example,  with  common  salt.  It  is  easily  resolved  by  heat  or  by  am- 
monia into  argentic  chloride  and  metallic  silver. 

SILVER  FLUORIDE,  AgF,  is  produced  by  dissolving  argentic  oxide  or  car- 
bonate in  aqueous  hydrofluoric  acid,  and  separates  on  evaporation  in  trans- 
parent quadratic  octohedrons,  which  contain  AgF.OH2,  and  give  off  their 
water  when  fused.  Their  solution  gives,  with  hydrochloric  acid,  a  precip- 
itate of  argentic  chloride.  When  chlorine  gas  is  passed  over  fused  silver 
fluoride,  silver  chloride  is  formed  and  fluorine  is  set  free  (p.  192). 

SILVER  IODIDE,  Agl,  is  a  pale-yellow  insoluble  precipitate,  produced  by 
adding  silver  nitrate  to  potassium  iodide ;  it  is  insoluble,  or  nearly  so,  in 
ammonia,  and  in  this  respect  forms  an  exception  to  the  silver-salts  in  gen- 
eral. Deville  has  obtained  a  crystalline  silver  iodide  by  the  action  of  con- 
centrated hydriodic  acid  upon  metallic  silver,  which  it  dissolves  with  dis- 
engagement of  hydrogen.  Hydriodic  acid  converts  silver  chloride  into 
iodide.  The  bromide  of  silver  very  closely  resembles  the  chloride. 

SILVER  OXIDES.  —  There  are  three  oxides  of  silver,  only  one  of  which 
can,  however,  be  regarded  as  a  well-defined  compound,  namely  : 

The  Monoxide  or  Argentic  Oxide,    OAg2.  —  This  oxide  is  a  powerful  base, 

*  The  existence  of  two  silver  chlorides  is  utterly  incoinpatihle  with  the  hyp<>the-i-  t! 
silver  iiml  chlorine  are  monad  ele.nents.     The  composition  of  the  uranttptU  Compound* 
perhaps  very  well  established;  but  supposing  the  chloride  to  contain  CI2Ag4,  H8  u-ually  st:  NO, 

its  constitution  maybe  represented  by  the  formula  T     "",  in  which  the  chlorine  play,  the 

ClAga 
part  of  a  triad. 


320  MONAD    METALS. 

yielding  salts  isomorphous  with  those  of  the  alkali-metals.  It  is  obtained 
as  a  pale-brown  precipitate  on  adding  caustic  potash  to  a  solution  of  silver 
nitrate  : 

2N03Ag      +      OKH      =      OAg2      +      N03K      -f     N03H 
Silver  Potassium  Silver  Potassium  Hydrogen 

nitrate.  hydrate.  oxide.  nitrate.  nitrate. 

It  is  very  soluble  in  ammonia,  and  is  dissolved  also  to  a  small  extent  by 
pure  water;  the  solution  is  alkaline.  Recently  precipitated  silver  chloride, 
boiled  with  a  solution  of  caustic  potash  of  specific  gravity  1-25,  is  con- 
verted, according  to  Gregory,  although  with  difficulty,  into  argentic  oxide, 
which  in  this  case  is  black  and  very  dense.  Argentic  oxide  neutralizes  acids 
completely,  and  forms,  for  the  most  part,  colorless  salts.  It  is  decomposed 
by  a  red-heat,  with  evolution  of  oxygen,  spongy  metallic  silver  being  left ; 
the  sun's  rays  also  effect  its  decomposition  to  a  small  extent. 

Argentous  Oxide,  OAg4.*  —  When  dry  argentic  citrate  is  heated  to  100°  in 
a  stream  of  hydrogen  gas,  it  loses  oxygen  and  becomes  dark-brown.  The 
product,  dissolved  in  water,  gives  a  dark-colored  solution  containing  free 
citric  acid  and  argentous  citrate,  which  .udien  mixed  with  potash  yields  a 
precipitate  of  argentous  oxide.  This  oxide  is  a  black  powder,  very  easily 
decomposed,  and  soluble  in  ammonia.  The  solution  of  argentous  citrate  is 
rendered  colorless  by  heat,  being  resolved  into  argentic  citrate  and  metallic 
silver.  According  to  Wohler,  argentous  oxide  is  also  formed  by  boiling  ar- 
gentic arsenite  with  caustic  alkalies.  In  this  case  it  is  mixed  with  metallic 
silver. 

OAg 

Silver  Dioxide,  02Ag2  or    I      .  —  This  is  a  black  crystalline   substance 

OAg 

which  forms  upon  the  positive  electrode  of  a  voltaic  arrangement  employed 
to  decompose  a  solution  of  silver  nitrate.  It  is  reduced  by  heat,  evolves 
chlorine  when  acted  upon  by  hydrochloric  acid,  explodes  when  mixed  with 
phosphorus  and  struck,  and  decomposes  solution  of  ammonia,  with  great 
energy  and  rapid  disengagement  of  nitrogen  gas. 

SILVER  NITRATE  or  ARGENTIC  NITRATE,  N03Ag.  —  This  salt  is  prepared 
by  dissolving  silver  in  nitric  acid,  and  evaporating  the  solution  to  dryness, 
or  until  it  is  strong  enough  to  crystallize  on  cooling.  The  crystals  are 
colorless,  transparent,  anhydrous  tables,  soluble  in  an  equal  weight  of  cold, 
and  in  half  that  quantity  of  boiling  water;  they  also  dissolve  in  alcohol. 
They  fuse  when  heated,  like  those  of  nitre,  and  at  a  high  temperature  suffer 
decomposition:  the  lunar  caustic  of  the  surgeon  is  silver  nitrate  which  has 
been  melted  and  poured  into  a  cylindrical  mould.  The  salt  blackens  when 
exposed  to  light,  more  particularly  if  organic  matters  of  any  kind  are 
present,  and  is  frequently  employed  to  communicate  a  dark  stain  to  the 
hair;  it  enters  into  the  composition  of  the  "indelible"  ink  used  for  mark- 
ing linen.  The  black  stain  has  been  thought  to  be  metallic  silver;  it  may 
possibly  be  argentous  oxide.  Pure  silver  nitrate  may  be  prepared  from  the 
metal  alloyed  with  copper:  the  alloy  is  dissolved  in  nitric  acid,  the  solution 
evaporated  to  dryness,  and  the  mixed  nitrates  cautiously  heated  to  fusion. 
A  small  portion  of  the  melted  mass  is  removed  from  time  to  time  for  exami- 
nation ;  it  is  dissolved  in  water,  filtered,  and  ammonia  added  to  it  in  excess. 
While  any  copper-salt  remains  undecomposed,  the  liquid  will  be  blue,  but 
when  that  no  longer  happens,  the  nitrate  maybe  suffered  to  cool,  dissolved 
in  water,  and  filtered  from  the  insoluble  black  oxide  of  copper. 

*  If  this  formula  be  correct,  oxygen  must  be  a  tretrad. 


SILVER.  321 

SILVER  SULPHATE,  S04Ag2.  —  The  sulphate  may  be  prepared  by  boiling 
together  oil  of  vitriol  and  metallic  silver,  or  by  precipitating  a  concentrated 
solution  of  silver  nitrate  with  an  alkaline  sulphate.  It  dissolves  in  88 
parts  of  boiling  water,  and  separates  in  great  measure  in  the  crystalline 
form  on  cooling,  having  but  a  feeble  degree  of  solubility  at  a  low  temper- 
ature. It  forms  with  ammonia  a  crystallizable  compound  which  is  freely 
soluble  in  water,  contains  S04Ag2.  2NH3,  and  may  therefore  be  regarded  as 
argentammonium  sulphate,  S04(NH3Ag)2. 

Silver  hyposulphate,  S206Ag2.OH2,  is  a  soluble  crystallizable  salt,  perma- 
nent in  the  air.  The  hyposulphite  is  insoluble,  white,  and  very  prone  to 
decomposition:  it  combines  with  the  alkaline  hyposulphites,  forming  sol- 
uble compounds  distinguished  by  an  intensely  sweet  taste.  The  alkaline 
hyposulphites  dissolve  both  oxide  and  chloride  of  silver,  and  give  rise  to 
similar  salts,  an  oxide  or  chloride  of  the  alkaline  metal  being  at  the  same 
time  formed:  hence  the  use  of  alkaline  hyposulphites  in  fixing  photographic 
pictures  (p.  97).  Silver  carbonate  is  a  white  insoluble  substance  .obtained 
by  mixing  solutions  of  silver  nitrate  and  sodium  carbonate.  It  is  black- 
ened and  decomposed  by  boiling. 

SILVER  SULPHIDE,  SAg2.  —  This  is  a  soft,  gray,  and  somewhat  malleable 
substance,  found  native  in  the  crystallized  state,  and  easily  produced  by 
melting  together  its  constituents,  or  by  precipitating  a  solution  of  silver 
with  hydrogen  sulphide.  It  is  a  strong  sulphur-base,  and  combines  with 
the  sulphides  of  antimony  and  arsenic :  examples  of  such  compounds  are 
found  in  the  beautiful  minerals,  dark  and  light-red  silver  ore. 

AMMONIA-COMPOUND  OF  SILVER  ;  BERTHOLLET'S  FULMINATING  SILVER. — 
When  precipitated,  argentic  oxide  is  digested  in  ammonia,  a  black  substance 
is  produced,  possessing  extremely  dangerous  explosive  properties.  While 
moist,  it  explodes  when  rubbed  with  a  hard  body,  but  when  dry  the  touch 
of  a  feather  is  sufficient.  The  ammonia  retains  some  of  this  substance  in 
solution,  and  deposits  it  in  small  crystals  by  spontaneous  evaporation.  A 
similar  compound  exists  containing  oxide  of  gold.  It  is  easy  to  understand 
the  reason  why  these  bodies  are  subject  to  such  violent  and  sudden  decom- 
position by  the  slightest  cause,  on  the  supposition  that  they  contain  an 
oxide  of  an  easily  reducible  metal  and  ammonia:  the  attraction  between 
the  two  constituents  of  the  substance  is  very  feeble,  while  that  between 
the  oxygen  of  the  one  and  the  hydrogen  of  the  other  is  very  powerful. 
The  explosion  is  caused  by  the  sudden  evolution  of  nitrogen  gas  and 
aqueous  vapor,  the  metal  being  set  free. 


Soluble  silver  salts  are  perfectly  characterized  by  the  white  curdy  pre- 
cipitate of  silver  chloride,  darkening  by  exposure  to  light,  and  insoluble 
in  hot  nitric  acid,  which  is  produced  by  the  addition  of  any  soluble  chlor- 
ide. Lead  and  mercury  are  the  only  metals  which  can  be  confounded  with 
silver  in  this  respect;  but  lead  chloride  is  soluble  to  a  great  extent  in 
boiling  water,  and  is  deposited  in  brilliant  acicular  crystals  when  the  solu- 
tion cools ;  and  mercurous  chloride  is  instantly  blackened  by  ammonia, 
whereas  silver  chloride  is  dissolved  thereby. 

Solutions  of  silver  are  reduced  to  the  metallic  state  by  iron,  c»/>/>rr,  mrr- 
cury,  and  other  metals.  They  give  with  hydrogen  sulphide  a  black  precipi- 
tate of  argentic  sulphide  insoluble  in  ammonium  sulphide:  with  nmstir. 
alkalies,  a  brown  precipitate  of  argentic  oxide;  and  with  n/fcalinr  carbonate*, 
a  white  precipitate  of  argentic  carbonate,  both  precipitates  being  easily 
soluble  in  ammonia.  Ordinary  sodium  phosphate  forms  a  yellow  precipitate 


322  MONAD    METALS. 

of  argentic  orthophosphate ;  potassium  chromate  or  bichromate,  a  red-brown 
precipitate  of  argentic  chromate. 


The  economical  uses  of  silver  are  many:  it  is  admirably  adapted  for 
culinary  and  other  similar  purposes,  not  being  attacked  in  the  slightest 
degree  by  any  of  the  substances  used  for  food.  It  is  necessary,  however, 
in  these  cases,  to  diminish  the  softness  of  the  metal  by  a  small  addition 
of  copper.  The  standard  silver  of  England  contains  222  parts  of  silver 
and  18  parts  of  copper. 


CLASS  II.— DYAD  METALS. 

GROUP  I.  — METALS  OF  THE  ALKALINE  EARTHS. 


BARIUM.* 
Atomic  weight,  137.     Symbol,  Ba. 

nnHIS  metal  occurs  abundantly  as  sulphate  and  carbonate,  forming  the 
u  veinstone  in  many  lead  mines.  Davy  obtained  it  in  the  metallic  state 
by  means  similar  to  those  described  in  the  case  of  lithium.  Bunsen  sub- 
jects barium  chloride  mixed  up  to  a  paste  with  water  and  a  little  hydro- 
chloric acid,  at  a  temperature  of  100°,  to  the  action  of  the  electric  current, 
using  an  amalgamated  platinum  wire  as  the  negative  pole.  In  this  manner 
the  metal  is  obtained  as  a  solid,  highly  crystalline  amalgam,  which,  when 
heated  in  a  stream  of  hydrogen,  yields  barium  in  the  form  of  a  tumefied 
mass,  tarnished  on  the  surface,  but  often  exhibiting  a  silver-white  lustre 
in  the  cavities.  Barium  may  also  be  obtained,  though  impure,  by  passing 
vapor  of  potassium  over  the  red-hot  chloride  or  oxide  of  barium.  It  is 
malleable,  melts  below  a  red  heat,  decomposes  water,  and  gradually  oxi- 
dizes in  the  air. 

BARIUM  CHLORIDE,  BaCl2 .  OH2.  — This  valuable  salt  is  prepared  by  dis- 
solving the  native  carbonate  in  hydrochloric  acid,  filtering  the  solution, 
and  evaporating  until  a  pellicle  begins  to  form  at  the  surface:  the  solution 
on  cooling  deposits  crystals.  When  native  carbonate  cannot  be  procured, 
the  native  sulphate  may  be  employed  in  the  following  manner:  —  The  sul- 
phate is  reduced  to  fine  powder,  and  intimately  mixed  with  one  third  of 
its'  weight  of  powdered  coal ;  the  mixture  is  pressed  into  an  earthen  cru- 
cible to  which  a  cover  is  fitted,  and  exposed  for  an  hour  or  more  to  a  high 
red  heat,  by  which  the  sulphate  is  converted  into  sulphide  at  the  expense 
of  the  combustible  matter  of  the  coal;  the  black  mass  thus  obtained  is 
powdered  and  boiled  in  water,  by  which  the  sulphide  is  dissolved;  and  the 
solution,  filtered  hot,  is  mixed  with  a  slight  excess  of  hydrochloric  acid. 
Barium  chloride  and  hydrogen  sulphide  are  then  produced,  the  latter  es- 
caping with  effervescence.  Lastly,  the  solution  is  filtered  to  separate  any 
little  insoluble  matter,  and  evaporated  to  the  crystallizing  point. 

The  crystals  of  barium  chloride  are  flat  four-sided  tables,  colorless  and 
transparent.  They  contain  two  molecules  of  water,  easily  driven  off  by 
heat.  100  parts  of  water  dissolve  43-5  parts  at  15-5°,  and  78  parts  at 
104  5°,  which  is  the  boiling-point  of  the  saturated  solution. 

BARIUM  MONOXIDE,  BARYTA,  BaO. — The  best  method  of  preparing  this 
jompound  is  to  decompose  the  crystallized  nitrate  by  heat  in  a  capacious 
porcelain  crucible  until  red  vapors  are  no  longer  disengaged:  the  nitric 

*  From  /JaptJf,  heavy,  in  allusion  to  the  great  specific  gravity  of  the  native  carbonate  and 
sulphate. 

323 


324  DYAD    METALS. 

acid  is  resolved  into  nitrous  acid  and  oxygen,  and  the  baryta  remains  be- 
hind in  the  form  of  a  grayish  spongy  mass,  fusible  at  a  high  degree  of 
heat.  When  moistened  with  water,  it  combines  into  a  hydrate,  with  great 
elevation  of  temperature. 

BARIUM  HYDRATE,  BaH202  =  BaO .  H20.  — This  compound  is  prepared  on 
a  large  scale  by  decomposing  a  hot  concentrated  solution  of  barium  chlor- 
ide with  a  solution  of  caustic  soda;  on  cooling,  crystals  of  barium  hydrate 
are  deposited,  which  may  be  purified  by  re-crystallization.  In  the  labora- 
tory the  barium  hydrate  is  often  prepared  by  decomposing  the  sulphide 
with  black  oxide  of  copper.  (See  barium  sulphide.)  The  crystals  of 
barium  hydrate  contain  BaH202 .  8  aq. ;  *  they  fuse  easily,  and  lose  their 
water  of  crystallization  when  strongly  heated. 

The  hydrate  is  a  white,  soft  powder,  having  a  great  attraction  for  car- 
bonic acid,  and  soluble  in  20  parts  of  cold  and  2  parts  of  boiling  water. 
Solution  of  barium  hydrate  is  a  valuable  reagent:  it  is  highly  alkaline 
to  test-paper,  and  instantly  rendered  turbid  by  the  smallest  trace  of  car- 
bonic acid. 

BARIUM  DIOXIDE,  Ba02.  —  This  oxide  maybe  formed,  as  already  men- 
tioned, by  exposing  baryta,  heated  to  full  redness  in  a  porcelain  tube,  to 
a  current  of  pure  oxygen  gas.  The  dioxide  is  gray,  and  forms  with  water 
a  white  hydrate,  which  is  not  decomposed  by  that  liquid  in  the  cold,  but 
dissolves  in  small  quantity.  Barium  hydrate,  when  heated  to  redness  in 
a  current  of  dry  atmospheric  air,  loses  its  water,  and  is  converted,  by  ab- 
sorption of  oxygen,  into  barium  dioxide,  from  which  the  second  atom  of 
oxygen  may  be  expelled  at  a  higher  temperature.  Boussingault  has  pro- 
posed to  utilize  these  reactions  for  the  preparation  of  oxygen  upon  a  large 
scale.  The  dioxide  may  also  be  made  by  heating  pure  baryta  to  redness 
in  a  platinum  crucible,  and  then  gradually  adding  an  equal  weight  of  po- 
tassium chlorate,  whereby  barium  dioxide  and  potassium  chloride  are  pro- 
duced. The  latter  may  be  extracted  by  cold  water,  and  the  dioxide  left 
in  the  state  of  hydrate.  It  is  interesting  chiefly  in  its  relation  to  hydrogen 
dioxide.  When  dissolved  in  dilute  acid,  it  is  decomposed  by  potassium 
bichromate,  and  by  the  oxide,  chloride,  sulphate,  and  carbonate  of  silver. 

BARIUM  NITRATE,  (N03)2Ba. —  The  nitrate  is  prepared  by  methods  ex- 
actly similar  to  those  adopted  for  preparing  the  chloride,  nitric  acid  being 
substituted  for  hydrochloric.  It  crystallizes  in  transparent  colorless  octo- 
hedrons,  which  are  anhydrous.  They  require  for  solution  8  parts  of  cold, 
and  3  parts  of  boiling  water.  This  salt  is  much  less  soluble  in  dilute 
nitric  acid  than  in  pure  water:  errors  sometimes  arise  from  such  a  preci- 
pitate of  crystalline  barium  nitrate  being  mistaken  for  sulphate.  It  dis- 
appears on  heating,  or  by  large  affusion  of  water. 

BARIUM  SULPHATE,  S04Ba.  —  Found  native  as  heavy  spar  or  barytes,  often 
beautifully  crystallized:  its  specific  gravity  is  as  high  as  4-4  to  4-8.  This 
compound  is  always  produced  when  sulphuric  acid  or  a  soluble  sulphate  is 
mixed  with  a  solution  of  a  barium  salt.  It  is  not  sensibly  soluble  in  water 
or  in  dilute  acids:  even  in  nitric  it  is  almost  insoluble:  hot  oil  of  vitriol 
dissolves  a  little,  but  the  greater  part  separates  again  on  cooling.  Barium 
sulphate  is  now  produced  artificially  on  a  large  scale ;  it  is  used  as  a  sub- 
stitute for  white  lead  in  the  manufacture  of  oil-paints.  The  sulphate  to 
be  used  for  this  purpose  is  precipitated  from  very  dilute  solutions :  it  is 
known  in  commerce  as  blancfixe.  Powdered  native  barium  sulphate,  being 

*  The  symbol  aq.  (abbreviation  of  aqua)  is  often  used  to  denote  water  of  crystallization. 


STRONTIUM.  325 

rather  crystalline,  has  not  sufficient  body.  For  the  production  of  sulphate, 
the  chloride  of  barium  is  first  prepared,  which  is  dissolved  in  a  large 
quantity  of  water,  and  then  precipitated  by  dilute  sulphuric  acid. 

BARIUM  CARBONATE,  C03Ba.  — The  natural  carbonate  is  called  wiiherite: 
the  artificial  is  formed  by  precipitating  the  chloride  or  nitrate  with  an  al- 
kaline carbonate,  or  carbonate  of  ammonia.  It  is  a  heavy,  white  powder, 
very  sparingly  soluble  in  water,  and  chiefly  useful  in  the  preparation  of 
the  rarer  barium  salts. 

BARIUM  SULPHIDES.  —  The  monosulphide,  BaS,  is  obtained  in  the  manner 
already  described;  the  higher  sulphides  may  be  formed  by  boiling  it  with 
sulphur.  Barium  monosulphide  crystallizes  from  a  hot  solution  in  thin, 
nearly  colorless  plates,  which  contain  water,  and  are  not  very  soluble : 
they  are  rapidly  altered  by  the  air.  A  strong  solution  of  this  sulphide  may 
be  employed  in  the  preparation  of  barium  hydrate,  by  boiling  it  with  small 
successive  portions  of  black  oxide  of  copper,  until  a  drop  of  the  liquid 
ceases  to  form  a  black  precipitate  with  lead  salts ;  the  filtered  liquid  on 
cooling  yields  crystals  of  the  hydrate.  In  this  reaction,  besides  hydrate 
of  barium,  the  hyposulphate  of  that  base,  and  sulphide  of  copper,  are  pro- 
duced ;  the  latter  is  insoluble,  and  is  removed  by  the  filter,  while  most  of 
the  hyposulphate  remains  in  the  mother-liquor. 


Solutions  of  barium  hydrate,  nitrate,  and  chloride,  are  constantly  kept 
in  the  laboratory  as  chemical  tests,  the  first  being  employed  to  effect  the 
separation  of  carbonic  acid  from  certain  gaseous  mixtures,  and  the  two 
latter  to  precipitate  sulphuric  acid  from  solution. 

Soluble  barium  salts  are  poisonous,  which  is  not  the  case  with  those  of 
the  base  next  to  be  described.  For  their  reactions,  see  p.  332. 


STRONTIUM. 

Atomic  weight,  87-5.     Symbol,  Sr. 

The  metal  strontium  may  be  obtained  from  its  oxide  by  means  similar  to 
those  described  in  the  case  of  barium:  it  is  usually  described  as  a  white 
metal,  heavy,  oxidizable  in  the  air,  and  capable  of  decomposing  water  at 
common  temperatures.  Matthiessen  states,  however,  that  it  has  a  dark- 
yellow  color,  and  specific  gravity  2-54.  He  prepares  it  by  filling  a  small 
crucible  having  a  porous  cell  with  anhydrous  strontium  chloride  mixed  with 
some  ammonium  chloride,  so  that  the  level  of  the  fused  chloride  in  the  cell 
is  much  higher  than  in  the  crucible.  The  negative  pole  placed  in  the  cell 
consists  of  a  very  fine  iron  wire.  The  positive  pole  is  an  iron  cylinder 
placed  in  the  crucible  round  the  cell.  The  heat  is  regulated  so  that  a  crust 
forms  in  the  cell,  and  the  metal  collects  under  this  crust. 

STRONTIUM  MONOXIDE;  STRONTIA;  SrO.  —  This  compound  is  best  pre- 
pared by  decomposing  the  nitrate  with  aid  of  heat:  it  resembles  in  almost 
every  particular  the  earth  baryta,  forming,  like  that  substance,  a  white 
hydrate,  soluble  in  water.  A  hot  saturated  solution  deposits  crystals  on 
cooling,  which  contain  SrH202.  8  aq. :  heated  to  dull  redness  they  lose  the 
whole  of  their  water,  anhydrous  strontia  being  left.  The  hydrate  has  a 
great  attraction  for  carbonic  acid. 

STRONTIUM  DIOXIDE,  Sr02  — Prepared  in  the  same  manner  as  barium 
dioxide :  it  may  be  substituted  for  the  latter  in  making  hydrogen  dioxide. 

28 


326  DYAD  METALS. 

The  native  carbonate  and  sulphate  of  strontium  serve  for  the  prepara- 
tion of  the  various  salts  by  means  exactly  similar  to  those  already  described 
in  the  case  of  barium  salts :  they  have  a  very  feeble  degree  of  solubility  in 
water. 

STRONTIUM  CHLORIDE,  SrCl2.  —  The  chloride  crystallizes  in  colorless 
needles  or  prisms,  which  are  slightly  deliquescent,  and  soluble  in  2  parts 
of  cold  and  a  still  smaller  quantity  of  boiling  water:  they  are  also  soluble 
in  alcohol,  and  the  solution,  when  kindled,  burns  with  a  crimson  flame. 
The  crystals  contain  6  molecules  of  water,  which  they  lose  by  heat:  at  a 
higher  temperature  the  chloride  fuses. 

STRONTIUM  NITRATE,  (N03)2Sr. — This  salt  crystallizes  in  anhydrous  octo- 
hedrons,  which  require  for  solution  5  parts  of  cold,  and  about  half  their 
weight  of  boiling  water.  It  is  principally  of  value  to  the  pyrotechnist,  who 
employs  it  in  the  composition  of  the  well-known  "red-fire."* 

The  spectral  phenomena  exhibited  by  strontium  compounds  are  mentioned 
on  page  89. 


CALCIUM. 

Atomic  weight,  40.     Symbol,  Ca. 

Calcium  is  one  of  the  most  abundant  and  widely  diffused  of  the  metals, 
though  it  is  never  found  in  the  free  state.  As  carbonate,  it  occurs  in  a  great 
variety  of  forms,  constituting,  as  limestone,  entire  mountain-ranges.  Cal- 
cium was  obtained  in  an  impure  state  by  Davy,  by  means  similar  to  those 
adopted  for  the  preparation  of  barium.  Matthiessen  prepares  the  pure 
metal  by  fusing  a  mixture  of  two  molecules  of  calcium  chloride  and  one  of 
strontium  chloride  with  some  chloride  of  ammonium  in  a  small  porcelain 
crucible,  in  which  an  iron  cylinder  is  placed  as  positive  pole,  and  a  pointed 
iron  wire  or  a  little  rod  of  carbon  connected  with  the  zinc  of  the  battery  is 
made  to  touch  the  surface  of  the  liquid.  The  reduced  metal  fuses  and  drops 
off  from  the  point  of  the  iron  wire,  and  the  bead  is  removed  from  the  liquid 
by  a  small  iron  spatula.  Lies-Bodart  and  Gobin-f-  prepare  calcium  by  ig- 
niting the  iodide  with  an  equivalent  quantity  of  sodium  in  an  iron  crucible 
having  its  lid  screwed  down. 

Calcium  is  a  light  yellow  metal  of  sp.  gr.  1-5778.  It  is  about  as  hard  as 
gold,  very  ductile,  and  may  be  cut,  filed,  or  hammered  out  into  plates  as  thin 
as  the  finest  paper.  It  tarnishes  slowly  in  dry,  more  quickly  in  damp  air, 
decomposes  water  quickly,  and  is  still  more  rapidly  acted  upon  by  dilute 
acids.  Heated  on  platinum  foil  over  a  spirit-lamp,  it  burns  with  a  bright 
flash ;  with  a  brilliant  light  also  when  heated  in  oxygen  or  chlorine  gas,  or 
in  vapor  of  bromine,  iodine,  or  sulphur. 

CALCIUM  CHLORIDE,  CaCl2,  is  usually  prepared  by  dissolving  marble  in 
hydrochloric  acid  ;  also  a  by-product  in  several  chemical  manufactures. 


*  RED  FIRE:  Grains. 

Dry  strontium  nitrate  .    800 
Sulphur        ...        225 

Potassium  chlorate  .    200 
Lampblack  ...          50 


GREEX  FIRE  :  Grains. 

Dry  barium  nitrate  .  .  450 
Sulphur  .  .  .  .150 
Potassium  chlorate  .  .  100 
Lampblack  ....  25 


The  strontium  or  barium-salt,  the  sulphur  and  the  lampblack,  must  be  finely  powdered  and 
intimately  mixed,  after  which  the  potassium  chlorate  should  be  added  in  rather  coarse 
powder,  and  mixed,  without  much  rubbing,  with  the  other  ingredients.  The  red  fire  compo- 
sition has  been  known  to  ignite  spontaneously. 

t  Comptes  Rendus,  xlvii.  23. 


CALCIUM.  327 

The  salt  separates  from  a  strong  solution  in  colorless,  prismatic,  and  exceed- 
ingly deliquescent  crystals,  which  contain  6  molecules  of  \v:itrr.  I'.v  ln-at 
this  water  is  expelled,  and  by  a  temperature  of  strong  ignition  the  Mil  is 
fused.  The  crystals  reduced  to  powder  are  employed  in  the  production  of 
artificial  cold  by  being  mixed  with  snow  or  powdered  ice  ;  and  the  chloride, 
strongly  dried  or  in  the  fused  state,  is  of  great  practical  use  in  desiccating 
•rases,  for  which  purpose  the  latter  are  slowly  transmitted  through  tubes 
tilled  with  fragments  of  the  salt.  Calcium  chloride  is  also  freely  soluble  in 
alcohol,  which,  when  anhydrous,  forms  with  it  a  definite  crystallizable  com- 
pound. 

CALCIUM  FLUORIDE;  FLUOR-SPAR;  CaF2. — This  substance  is  important 
as  the  most  abundant  natural  source  of  hydrofluoric  acid  and  the  other 
fluorides.  It  occurs  beautifully  crystallized,  of  various  colors,  in  lead-veins, 
the  crystals  having  commonly  the  cubic,  but  sometimes  the  octohedral  form, 
parallel  to  the  faces  of  which  latter  figure  they  always  cleave.  Some  varie- 
ties, when  heated,  emit  a  greenish,  and  some  a  purple  phosphorescent  light. 
The  fluoride  is  quite  insoluble  in  water,  and  is  decomposed  by  oil  of  vitriol 
in  the  manner  already  mentioned  (p.  192). 

CALCIUM  MONOXIDE  ;  LIME;  CaO.  —  This  extremely  important  compound 
may  be  obtained  in  a  state  of  considerable  purity  by  heating  to  full  redness 
for  some  time  fragments  of  the  black  bituminous  marble  of  Derbyshire  or 
Kilkenny.  If  required  absolutely  pure,  it  must  be  made  by  igniting  to 
whiteness,  in  a  platinum  crucible,  an  artificial  calcium  carbonate,  prepared 
by  precipitating  the  nitrate  with  ammonia  carbonate.  Lime  in  an  impure 
state  is  prepared  for  building  and  agricultural  purposes  by  calcining,  in  a 
kiln  of  suitable  construction,  the  ordinary  limestones  which  abound  in  many 
districts ;  a  red  heat,  continued  for  some  hours,  is  sufficient  to  disengage 
the  whole  of  the  carbonic  acid.  In  the  best  contrived  lime-kilns  the  process 
is  carried  on  continuously,  broken  limestone  and  fuel  being  constantly 
thrown  in  at  the  top,  and  the  burned  lime  raked  out  at  intervals  from 
beneath.  Sometimes,  when  the  limestone  contains  silica,  and  the  heat  has 
been  very  high,  the  lime  refuses  to  slake,  and  is  said  to  be  over-burned;  in 
this  case  a  portion  of  silicate  has  been  formed. 

Pure  lime  is  white,  and  often  of  considerable  hardness ;  it  is  quite  infus- 
ible, and  phosphoresces,  or  emits  a  pale  light  at  a  high  temperature.  When 
moistened  with  water,  it  slakes  with  great  violence,  evolving  heat,  and 
crumbling  to  a  soft,  white,  bulky  powder,  which  is  a  hydrate  containing  a 
single  molecule  of  water:  the  latter  can  be  again  expelled  by  red-heat. 
This  hydrate,  CaH202  or  CaO .  OH2,  is  soluble  in  water,  but  far  less  so  than 
either  the  hydrate  of  barium  or  of  strontium,  and,  what  is  very  remark- 
able, the  colder  the  water,  the  larger  is  the  quantity  of  the  compound  that  is 
taken  up.  A  pint  of  water  at  15-5°  C.  (60°  F.)  dissolves  about  11  grains, 
while  at  100°  C.  ((212°  F.)  only  7  grains  are  retained  in  solution.  The  hy- 
drate has  been  obtained  in  thin  delicate  crystals  by  slow  evaporation  under 
the  air-pump.  Lime-water  is  always  prepared  for  chemical  and  pharma- 
ceutical purposes  by  agitating  cold  water  with  excess  of  calcium  hydrate  in 
a  closely  stopped  vessel,  and  then,  after  subsidence,  pouring  off  the  clear 
liquid,  and  adding  a  fresh  quantity  of  water,  for  another  operation:  there 
is  not  the  least  occasion  for  filtering  the  solution.  Lime-water  has  a  strong 
alkaline  reaction,  a  nauseous  taste,  and  when  exposed  to  the  air  becomes 
almost  instantly  covered  with  a  pellicle  of  carbonate,  by  absorption  of  car- 
bonic acid.  It  is  used,  like  baryta-water,  as  a  test  for  carbonic  acid,  and 
also  in  medicine.  Lime-water  prepared  from  some  varieties  of  limestone 
may  contain  potash. 

The  hardening  of  mortars  and  cements  is  in  a  great  measure  due  to  the 


328  DYAD    METALS. 

gradual  absorption  of  carbonic  acid ;  but  even  after  a  very  great  length  of 
time,  this  conversion  into  carbonate  is  not  complete.  Mortar  is  known, 
under  favorable  circumstances,  to  acquire  extreme  hardness  with  age. 
Lime-cements  which  resist  the  action  of  water  contain  iron  oxides,  silica, 
arid  alumina  :  they  require  to  be  carefully  prepared,  and  the  stone  not  over- 
heated. When  they  are  ground  to  powder  and  mixed  with  water,  solidifi- 
cation speedily  ensues,  from  causes  not  yet  thoroughly  understood,  and  the 
cement,  once  in  this  condition,  is  unaffected  by  wet.  Parker's  or  Roman 
cement  is  made  in  this  manner  from  the  nodular  masses  of  calcareo-argil- 
laceous  ironstone  found  in  the  London  clay.  Lime  is  of  great  importance 
in  agriculture  :  it  is  found  more  or  less  in  every  fertile  soil,  and  is  often 
very  advantageously  added  by  the  cultivator.  The  decay  of  vegetable  fibre 
in  the  soil  is  thereby  promoted,  and  other  important  objects,  as  the  destruc- 
tion of  certain  hurtful  compounds  of  iron  in  marsh  and  peat-land,  are  often 
attained.  The  addition  of  lime  probably  serves  likewise  to  liberate  potas- 
sium from  the  insoluble  silicate  of  that  base  contained  in  the  soil. 

CALCIUM  DIOXIDE,  Ca02.  —  This  compound  is  stated  to  resemble  barium 
dioxide,  and  to  be  obtainable  by  treating  lime  with  hydrogen  dioxide. 

CALCIUM  SULPHATE  ;  S04Ca.  —  Crystalline  native  calcium  sulphate,  con- 
taining two  molecules  of  water,  is  found  in  considerable  abundance  in  some 
localities  as  gypsum :  it  is  often  associated  with  rock-salt.  When  regularly 
crystallized,  it  is  termed  selenite.  Anhydrous  calcium  sulphate  is  also  occa- 
sionally met  with.  The  salt  is  formed  by  precipitation,  when  a  moderately 
concentrated  solution  of  calcium  chloride  is  mixed  with  sulphuric  acid. 
Calcium  sulphate  is  soluble  in  about  500  parts  of  cold  water,  and  its  solu- 
bility is  a  little  increased  by  heat.  It  is  more  soluble  in  water  containing 
ammonium  chloride  or  potassium  nitrate.  The  solution  is  precipitated  by 
alcohol.  Gypsum,  or  native  hydrated  calcium  sulphate,  is  largely  employed 
for  the  purpose  of  making  casts  of  statues  and  medals,  and  also  for  moulds 
in  the  porcelain  and  earthenware  manufactures,  and  for  other  applications. 
It  is  exposed  to  heat  in  an  oven  where  the  temperature  does  not  exceed 
127°  C.  (260°  F.),  by  which  the  water  of  crystallization  is  expelled,  and  it 
is  afterwards  reduced  to  a  fine  powder.  When  mixed  with  water,  it  solidi- 
fies after  a  short  time,  from  the  re-formation  of  the  same  hydrate  ;  but  this 
effect  does  not  happen  if  the  gypsum  has  been  over-heated.  It  is  often  called 
Plaster  of  Paris.  Artificial  colored  marbles,  or  scagliola,  are  frequently 
prepared  by  inserting  pieces  of  natural  stone  in  a  soft  stucco  containing 
this  substance,  and  polishing  the  surface  when  cement  has  become  hard. 
Calcium  sulphate  is  one  of  the  most  common  impurities  of  spring  water. 

The  peculiar  property  water  acquires  by  the  presence  of  calcium  salts  is 
termed  hardness.  It  manifests  itself  by  the  effect  such  waters  have  upon 
the  palate,  and  particularly  by  its  peculiar  behavior  with  soap.  Hard 
water  yields  a  lather  with  soap  only  after  the  whole  of  the  calcium  salts 
have  been  thrown  down  from  the  water  in  the  form  of  an  insoluble  lime- 
soap.  Upon  this  principle  Prof.  Clark's  soap-test  for  the  hardness  of  water 
is  based.*  The  hardness  produced  by  calcium  sulphate  is  called  permanent 
hardness,  since  it  cannot  be  remedied. 

CALCIUM  CARBONATE  ;  CHALK;  LIMESTONE;  MARBLE;  C03Ca. — Calcium 
carbonate,  often  more  or  less  contaminated  with  iron  oxide,  clay,  and  or- 
ganic matter,  forms  rocky  beds,  of  immense  extent  and  thickness,  in  almost 
every  part  of  the  world.  These  present  the  greatest  diversities  of  texture 
and  appearance,  arising,  in  a  great  measure,  from  changes  to  which  they 
have  been  subjected  since  their  deposition.  The  most  ancient  and  highly 

*  Journal  of  the  Pharmaceutical  Society,  vol.  vi.  p.  526. 


CALCIUM.  329 

crystalline  limestones  are  destitute  of  visible  organic  remains,  while  those 
of  more  recent  origin  are  often  entirely  made  up  of  the  shelly  exuviae  of 
once-living  beings.  Sometimes  these  latter  are  of  such  a  nature  as  to 
show  that  the  animals  inhabited  fresh  water;  marine  species  and  corals  are, 
however,  most  abundant.  Cavities  in  limestone  and  other  rocks  are  very 
often  lined  with  magnificent  crystals  of  calcium  carbonate  or  calcareous 
spar,  which  have  evidently  been  slowly  deposited  from  a  watery  solution. 
Calcium  carbonate  is  always  precipitated  when  an  alkaline  carbonate  is 
mixed  with  a  solution  of  that  base. 

Although  this  substance  is  not  sensibly  soluble  in  pure  water,  it  is  freely 
taken  up  when  carbonic  acid  happens  at  the  same  time  to  be  present.  If 
a  little  lime-water  be  poured  into  a  vessel  of  that  gas,  the  turbidity  first 
produced  disappears  on  agitation,  and  a  transparent  solution  of  calcium 
carbonate  in  excess  of  carbonic  acid  is  obtained.  This  solution  is  decom- 
posed completely  by  boiling,  the  carbonic  acid  being  expelled,  and  the  car- 
bonate precipitated.  Since  all  natural  waters  contain  dissolved  carbonic 
acid,  it  is  to  be  expected  that  calcium  in  this  state  should  be  of  very  com- 
mon occurrence ;  and  such  is  really  found  to  be  the  fact,  river,  and  more 
especially  spring  water,  almost  invariably  containing  calcium  carbonate 
thus  dissolved.  In  limestone  districts,  this  is  often  the  case  to  a  great  ex- 
tent. The  hardness  of  water,  which  is  owing  to  the  presence  of  calcium 
carbonate,  is  called  temporary,  since  it  is  diminished  to  a  very  considerable 
extent  by  boiling,  and  may  be  nearly  removed  by  mixing  the  hard  water 
with  lime-water,  when  both  the  dissolved  carbonate  and  the  dissolved  lime, 
which  thus  becomes  carbonated,  are  precipitated.  Upon  this  principle 
Prof.  Clark's  process  of  softening  water  is  based.  This  process  is  of  con- 
siderable importance,  since  a  supply  of  hard  water  to  towns  is  in  many  re- 
spects a  source  of  great  inconvenience.  As  already  mentioned,  the  use  of 
such  water,  for  the  purposes  of  washing,  is  attended  with  a  great  loss  of 
soap.  Boilers,  in  which  such  water  is  heated,  speedily  become  lined  with 
a  thick  stony  incrustation.*  The  beautiful  stalactitic  incrustations  of  lime- 
stone caverns,  and  the  deposit  of  calc-sinter  or  travertin  upon  various  ob- 
jects, and  upon  the  ground,  in  many  places,  are  thus  explained  by  the 
solubility  of  calcium  carbonate  in  water  containing  carbonic  acid. 

Crystallized  calcium  carbonate  is  dimorphous ;  calc-spar  and  ar-ragonite, 
although  possessing  exactly  the  same  chemical  composition,  have  different 
crystalline  forms,  different  densities,  and  different  optical  properties.  Rose 
has  observed  that  calcium  carbonate  appears  in  the  form  of  calc-spar  when 
deposited  from  its  solution  in  water  containing  carbonic  acid  at  the  ordi- 
nary temperature.  At  90°  C.  (194°  F.),  and  on  ebullition,  however,  it  is 
chiefly  deposited  in  the  form  of  arragonite ;  at  lower  temperatures  the 
formation  of  arragonite  decreases,  whilst  that  of  calc-spar  increases,  the 
limit  for  the  formation  of  the  former  variety  being  between  30°  and  50°  C. 
(86°— 122°  F.). 

Calc-spar  occurs  very  abundantly  in  crystals  derived  from  an  obtuse 
rhombohedron,  whose  angles  measure  105°  5'  and  74°55/:  its  density 
varies  from  2-5  to  28.  The  rarer  variety,  or  arragonite,  is  found  in  crys- 
tals whose  primary  form  is  a  right  rhombic  prism,  a  figure  having  no  geo- 
metrical relation  to  the  preceding:  it  is,  besides,  heavier  and  harder. 

CALCIUM  PHOSPHATES. — A  number  of  distinct  calcium  salts  of  phos- 
phoric acid  are  known.  The  tribasic  phosphates,  or  orlhophosphates,  (P04)2 

*  Many  proposals  have  boon  made  to  prevent  the  formation  of  boiler  deposits.  The  m<»t 
efficient  appears  to  be  the  method  of  Dr.  Kitterband,  which  consists  it.  throwing  Into  the  boiler 
a  small  quantity  of  sal-ammoniac,  when  carbonate  of  ammonia  is  formed,  which  is  volatilized 
with  the  steam,  calcium  chloride  remainm-  in  solution.  It  need  scarcely  be  mentioned  that 
thid  plan  is  inapplicable  in  the  case  of  permanently  hard  waters. 
28* 


330  DYAD    METALS. 

Cax/3  and  (P04)Ca//H,  are  produced  when  the  corresponding  sodium  salts 
are  added  in  solution  to  calcium  chloride;  the  first  is  slightly  crystalline, 
and  the  second  gelatinous.  When  the  first  phosphate  is  digested  with  am- 
monia, or  dissolved  in  acid  and  re-precipitated  by  that  alkali,  it  is  converted 
into  the  second.  The  earth  of  bones  consists  principally  of  what  appears 
to  be  a  combination  of  these  two  salts.  Another  orthophosphate,  (PO^)., 
Ca/7H4,  is  formed  by  dissolving  either  of  the  preceding  in  phosphoric,  hy- 
drochloric, or  nitric  acid,  and  evaporating  until  the  salt  separates  on  cool- 
ing in  small  platy  crystals.  It  is  the  substance  which  yields  phosphorus 
when  heated  with  charcoal,  in  the  ordinary  process  of  manufacture  before 
described.  Pyrophosphates  and  Metaphosphatcs  of  calcium  also  exist.  These 
phosphates,  although  insoluble  in  water,  dissolve  readily  in  dilute  acids, 
even  in  acetic  acid.  The  mineral  apatite  is  chiefly  calcium  phosphate. 

CHLORIDE  OF  LIME  ;  BLEACHING  POWDER.  —  When  calcium  hydrate,  very 
slightly  moist,  is  exposed  to  chlorine  gas,  the  latter  is  eagerly  absorbed, 
and  a  compound  produced  which  has  attracted  a  great  deal  of  attention: 
this  is  the  bleaching  powder  of  commerce,  now  manufactured  on  an  im- 
mense scale,  for  bleaching  linen  and  cotton  goods.  It  is  requisite,  in 
preparing  this  substance,  to  avoid  with  the  greatest  care  all  elevation  of 
temperature,  which  may  be  easily  done  by  supplying  the  chlorine  slowly 
in  the  first  instance.  The  product,  when  freshly  and  well  prepared,  is  a 
soft,  white  powder,  which  attracts  moisture  from  the  air,  and  exhales  an 
odor  sensibly  different  from  that  of  chlorine.  It  is  soluble  in  about  10 
parts  of  water,  the  unaltered  hydrate  being  left  behind :  the  solution  is 
highly  alkaline,  and  bleaches  feebly.  When  calcium  hydrate  is  suspended 
in  cold  water,  and  chlorine  gas  transmitted  through  the  mixture,  the  lime 
is  gradually  dissolved,  and  the  same  peculiar  bleaching  compound  pro- 
duced :  the  alkalies  also,  either  caustic  or  carbonated,  may  by  similar 
means  be  made  to  absorb  a  large  quantity  of  chlorine,  and  give  rise  to  cor- 
responding compounds;  such  are  the  "disinfecting  solutions"  of  Labar- 
raque. 

The  most  consistent,  view  of  the  constitution  of  these  compounds  is  that 
which  supposes  them  to  contain  salts  of  hypochlorous  acid,  HC10,  a  sub- 
stance as  remarkable  for  bleaching  powers  as  chlorine  itself;  and  this 
opinion  seems  borne  out  by  a  careful  comparison  of  the  properties  of  the 
bleaching  salts  with  those  of  the  true  hypochlorites.  Hypochlorous  acid 
can  be  actually  obtained  from  good  bleaching-powder,  by  distilling  it  with 
dilute  sulphuric  or  nitric  acid,  in  quantity  insufficient  to  decompose  the 
whole :  when  the  acid  is  used  in  excess,  chlorine  is  disengaged.* 

If  this  view  be  correct,  chloride  of  calcium  must  be  formed  simultane- 
ously with  the  hypochlorite,  as  shown  by  the  following  equation : 

2CaO  -j-  C14  =  CaCl2  -f  CaCl202 

Lime.  Calcium        Calcium 

chloride,    hypochlorite. 

When  the  temperature  of  the  calcium  hydrate  has  risen  during  the  absorp- 
tion of  the  chlorine,  or  when  the  compound  has  been  subsequently  exposed 
to  heat,  its  bleaching  properties  are  impaired  or  altogether  destroyed:  it 
then  contains  chlorate  and  chloride  of  calcium ;  oxygen,  in  variable  quan- 
tity, is  usually  set  free.  The  same  change  seems  to  ensue  by  long  keeping, 
even  at  the  common  temperature  of  the  air.  In  an  open  vessel  it  is 
speedily  destroyed  by  the  carbonic  acid  of  the  air.  Commercial  bleaching- 
powder  thus  constantly  varies  in  value  with  its  age,  and  with  the  care  ori- 
ginally bestowed  upon  its  preparation :  the  best  may  contain  about  30  per 

*  Gay-Lussac,  Ann.  Chim.  Phys.,  3d  series,  v.  296. 


CALCIUM.  331 

cent,  of  available  chlorine,  easily  liberated  by  an  acid,  which  is,  however, 
far  short  of  the  theoretical  quantity. 

The  general  method  in  which  this  substance  is  employed  for  bleaching  is 
the  following:  The  goods  are  first  immersed  in  a  dilute  solution  of  chloride 
of  lime  and  then  transferred  to  a  vat  containing  dilute  sulphuric  acid. 
Decomposition  ensues;  the  calcium  both  of  the  hypochlorite  and  of  the 
chloride  is  converted  into  sulphate,  while  the  free  hypochlorous  and  hydro- 
chloric acids  yield  water  and  free  chlorine : 

CaCl102  -(-  CaCl2  +  2S04H2  =  2S04Ca  +  2HC10  -f  2HC1 ; 
and:  HC10  +  HC1  =  OH2  -f  C12. 

The  chlorine  thus  disengaged  in  contact  with  the  cloth  causes  the  destruc- 
tion of  the  coloring  mutter.  This  process  is  often  repeated,  it  being  unsufe 
to  use  strong  solutions.  White  patterns  are  on  this  principle  imprinted 
upon  colored  cloth,  the  figures  being  stamped  with  tartaric  acid  thickened 
with  gum-water,  and  Chen  the  stuff  immersed  in  the  chloride  bath,  when 
the  parts  to  which  no  acid  has  been  applied  remain  unaltered,  while  the 
printed  portions  are  bleached. 

For  purifying  an  offensive  or  infectious  atmosphere,  as  an  aid  to  proper 
ventilation,  the  bleaching  powder  is  very  convenient.  The  solution  is  ex- 
posed in  shallow  vessels,  or  cloths  steeped  in  it  are  suspended  in  the  apart- 
ment, when  the  carbonic  acid  of  the  air  slowly  decomposes  it  in  the  manner 
above  described.  An  addition  of  a  strong  acid  causes  rapid  disengagement 
of  chlorine. 

The  value  of  any  sample  of  bleaching  powder  may  be  easily  determined 
by  the  following  method,  in  which  the  feebly  combined  chlorine  is  esti- 
mated by  its  effect  in  oxidizing  a  ferrous  salt  to  ferric  salt,  2  molecules  of 
ferrous  oxide,  FeO,  requiring  for  this  purpose  2  atoms  of  chlorine:  the 
latter  acts  by  decomposing  water  and  liberating  a  corresponding  quantity 
of  oxygen.  78  (more  correctly  78-16)  grains  of  green  ferrous  sulphate 
are  dissolved  in  about  two  ounces  of  water,  and  acidulated  by  a  few  drops 
of  sulphuric  or  hydrochloric  acid :  this  quantity  will  require  for  oxidation 
10  grains  of  chlorine.  Fifty  grains  of  the  chloride  of  lime  to  be  examined 
are  next  rubbed  up  with  a  little  tepid  water,  and  the  whole  transferred  to 
the  burette  *  before  described,  which  is  then  filled  up  to  0  with  water,  after 
which  the  contents  are  well  mixed  by  agitation.  The  liquid  is  next  grad- 
ually poured  into  the  solution  of  iron,  with  constant  stirring,  until  all  the 
iron  is  brought  to  the  state  of  ferric  salt,  which  may  be  known  by  a  drop 
ceasing  to  give  a  deep-blue  precipitate  with  potassium  ferricyanide.  The 
number  of  grain-measures  of  the  chloride  solution  employed  may  then  be 
read  off:  since  these  must  contain  10  grains  of  serviceable  chlorine,  the 
quantity  of  the  latter  in  the  50  grains  may  be  easily  reckoned.  Thus, 
suppose  72  such  measures  have  been  taken;  then 

Measures.       Grs.  Chlorine.  Measures.          Grs.  Chlorine. 

72         :         10        =         100         :         13-89 

The  bleaching-powder  contains  therefore  27-78  per  cent.f 

CALCIUM  SULPHIDES. — The  monosulphide,  CaS,  is  obtained  by  reducing 
the  sulphate  at  a  high  temperature  with  charcoal  or  hydrogen :  it  is  nearly 
colorless,  and  but  little  soluble  in  water.  By  boiling  together  calcium 
hydrate,  water,  and  flowers  of  sulphur,  a  red  solution  is  obtained,  which, 
on  cooling,  deposits  crystals  of  the  bisulphide,  CaS2,  containing  water. 

*  See  p.  306. 

f  (Jrjihiiiifs  Elements,  vol.  i.  p.  593.  For  other  methods,  see  Watts's  Dictionary  of  Chemis- 
try, i.  p.  904. 


832  DYAD    METALS. 

When  the  sulphur  is  in  excess,  and  the  boiling  long  continued,  a  penta- 
sulphide  is  generated :  hyposulphurous  acid  is  formed  as  usual  during 
these  reactions. 

CALCIUM  PHOSPHIDE. — When  vapor  of  phosphorus  is  passed  over  frag- 
ments of  lime  heated  to  redness  in  a  porcelain  crucible,  a  chocolate-brown 
compound,  the  so-called  phosphuret  of  lime,  is  produced.  This  substance  is 
probably  a  mixture  of  calcium  phosphide  and  phosphate.  When  thrown 
into  water  it  yields  spontaneously  inflammable  hydrogen  phosphide.  Ac- 
cording to  Paul  Thenard,  the  calcium  phosphide  in  this  compound  has  the 
composition  P2Ca2.  In  contact  with  water  it  yields  liquid  hydrogen  phos- 
phide, P2H4  (p.  216) : 

P2Ca2  -f  20H2  =  2CaO  +  P2H4: 

and  the  greater  portion  of  this  liquid  phosphide  is  immediately  decomposed 
into  solid  and  gaseous  hydrogen  phosphide: 

5P2H4    =     P4H2     +     6PH3 
Liquid.  Solid.  Gaseous. 


Reactions  of  the  Alkaline  Earth-metals  in  solution.  —  Barium,  strontium,  and 
calcium  are  thus  distinguished  from  all  other  substances,  and  from  each 
other. 

Caustic  potash,  when  free  from  carbonate,  and  caustic  ammonia,  occasion 
no  precipitates  in  dilute  solutions  of  the  alkaline  earths,  especially  of  the 
first  two,  the  hydrates  being  soluble  in  water. 

Alkaline  carbonates,  and  carbonate  of  ammonia,  give  white  precipitates,  in- 
soluble in  excess  of  the  precipitant,  with  all  three. 

Sulphuric  acid,  or  a  sulphate,  added  to  very  dilute  solutions  of  the  salts 
of  these  metals,  gives  an  immediate  white  precipitate  with  barium  salts ; 
a  similar  precipitate  after  a  short  interval  with  strontium  salts ;  and  occa- 
sions no  change  with  calcium  salts.  The  precipitates  with  barium  and 
strontium  salts  are  insoluble  in  nitric  acid. 

Solution  of  calcium  sulphate  gives  an  instantaneous  cloud  with  barium 
salts,  and  one  with  strontium  salts  after  a  little  time.  Strontium  sulphate  is 
itself  sufficiently  soluble  to  occasion  turbidity  when  mixed  with  barium 
chloride. 

Lastly,  the  soluble  oxalates  give  a  white  precipitate  in  the  most  dilute 
solutions  of  calcium  salts,  which  is  not  dissolved  by  a  drop  or  two  of  hy- 
drochloric, or  by  an  excess  of  acetic  acid.  This  is  an  exceedingly  charac- 
teristic test. 

The  chlorides  of  strontium  and  calcium  dissolved  in  alcohol  color  the  flame 
of  the  latter  red  or  purple :  barium  salts  communicate  to  the  flame  a  pale 
green  tint. 

Silicofluoric  acid  gives  a  white  precipitate  with  barium  salts,  none  with 
salts  of  strontium  or  calcium. 


GROUP  II.  — METALS  OF  THE  EARTHS. 

The  dyad  earth-metals  are  beryllium,  thorinum,  yttrium,  erbium,  lan- 
thanum, and  didymium.  With  these  it  will  be  convenient  to  describe  the 
tetradic  metals,  aluminium,  zirconum,  and  cerium ;  the  first  two  because 
their  oxides  are  of  decidedly  earthy  character:  in  fact,  alumina  may  be 
looked  upon  as  the  type  of  an  earthy  oxide ;  and  the  third  on  account  of 
its  constant  association  with  lanthanum  and  didymium. 


" 


ALUMINIUM.  333 


ALUMINIUM. 
Atomic  weight,  27-4.     Symbol,  Al. 

This  metal  occurs  very  abundantly  in  nature  in  the  state  of  silicate,  as 
in  felspar  and  its  associated  minerals  ;  also  in  the  various  modifications  of 
clay  thence  derived.  It  was  first  isolated  by  Wohler,  who  obtained  it  as  a 
gray  powder  by  decomposing  aluminium  chloride  with  potassium;  and  H. 
Sainte-Claire  Deville,  by  an  improved  process  founded  on  the  same  prin- 
ciple, hns  succeeded  in  obtaining  it  in  the  compact  form  and  on  the  manu- 
facturing scale.  The  process  consists  in  decomposing  the  double  chloride 
of  aluminium  and  sodium,  A12C16.  2NaCl,  by  heating  it  with  metallic  sodium, 
fluor-spar  or  cryolite  being  added  as  a  flux.  The  reduction  is  effected 
in  crucibles,  or  on  the  large  scales  on  the  hearth  of  a  reverberatory  furnace. 
Sodium  is  used  as  the  reducing  agent  in  preference  to  potassium  :  first, 
because  it  is  more  easily  prepared;  and,  secondly,  because  it  has  a  lower 
atomic  weight,  and,  consequently,  a  smaller  quantity  of  it  suffices  to  do  the 
same  amount  of  chemical  work. 

Aluminium  is  also  prepared  directly  from  cryolite  by  reduction  with 
sodium,  but  the  metal  thus  obtained  is  said  to  be  more  contaminated  with 
iron  and  silicium  than  that  prepared  by  Deville's  process, 

Aluminium  is  remarkable  for  its  low  specific  gravity,  which  is  2-6  :  it  is 
nearly  as  white  as  silver,  and  is  capable  of  assuming  a  high  polish.  It  is 
employed  in  the  manufacture  of  delicate  apparatus  and  ornamental  articles. 
Some  of  the  alloys  of  aluminium  promise  to  become  more  generally  appli- 
cable, more  especially  the  alloy  with  copper,  which  is  remarkable  for  being 
similar  in  appearance  to  gold  :  this  alloy  is  found  already  in  commerce 
under  the  name  of  aluminium  bronze. 

Aluminium  forms  only  one  class  of  compounds,  in  all  of  which  it  appears 
to  be  trivalent,  one  atom  of  the  metal  being  equivalent  to  three  atoms  of 
hydrogen  ;  thus  the  chloride  is  A1///2C16.  the  oxide  Al'^Og,  &c.  Each  of 
these  compounds,  however,  contains  two  atoms  of  aluminium,  and  it  may 
therefore  be  supposed  that  the  aluminium  is  really  tetradic,  one  unit  of 
equivalency  in  each  atom  being  neutralized  by  one  unit  in  the  other;  thus, 

A1C13 
the  chloride  is    I        .     That  such  is  the  case  is  inferred  from  the  resem- 


blance  of  the  aluminium  compounds  to  the  ferric  and  chromic  compounds 
(p.  272). 

ALUMINIUM  CHLORIDE,  A12C16.  —  This  compound  is  obtained  in  solution  by 
dissolving  alumina  or  aluminium  hydrate  in  hydrochloric  acid  ;  but  the  so- 
lution, when  evaporated,  gives  otF  hydrochloric  acid  and  leaves  alumina. 
The  anhydrous  chloride  may  be  prepared  by  heating  a  mixture  of  alumina 
and  finely  divided  carbon  in  chlorine  gas.  , 

Pure  precipitated  alumina  is  dried  and  mixed  with  oil  and  lampblack,  and 
the  mixture,  after  being  strongly  calcined  in  a  covered  crucible,  is  intro- 
duced into  a  porcelain  tube  or  tubulated  earthen  retort  placed  in  a  furnace, 
and  connected  at  one  end  with  an  apparatus  for  evolving  chlorine,  and  at 
the  other  with  a  dry  receiver.  On  raising  the  heat  to  bright  redness,  and 
passing  chlorine  through  the  apparatus,  aluminium  chlorido  distils  over, 
together  with  carbon  monoxide,  and  condenses  as  a  solid  mass  in  the  re- 
ceiver. 

A1203     -f     C3     +     C16     =    A12C16     +     3CO. 

Aluminium  chloride  is  a  transparent  waxy  substance,  having  a  crystal- 


334  EARTH-METALS. 

line  structure,  colorless  when  pure,  but  generally  exhibiting  a  yellow  color, 
due  perhaps  to  the  presence  of  iron.  It  boils  at  about  180°,  fumes  in  the 
air,  and  smells  of  hydrochloric  acid.  It  is  very  deliquescent,  and  dissolves 
readily  in  water ;  the  solution  when  left  to  evaporate  yields  the  hydrated 
chloride,  A12C16.120H2,  in  six-sided  prisms,  which  when  heated  are  resolved 
into  alumina  and  hydrochloric  acid. 

Aluminium  and  Sodium  Chloride,  A12C16  2NaCl,  is  obtained  by  melting  to- 
gether the  component  chlorides  in  proper  proportions,  or  by  adding  the 
requisite  quantity  of  sodium  chloride  to  the  mixture  of  alumina  and  char- 
coal used  for  the  preparation  of  aluminium  chloride,  igniting  the  mass  in 
chlorine  or  hydrochloric  acid,  and  condensing  the  vapor  in  a  receiver.  It 
is  a  crystalline  mass,  less  deliquescent  than  aluminium  chloride,  and,  there- 
fore, more  convenient  for  the  preparation  of  aluminium. 

ALUMINIUM  FLUORIDE,  A12F6,  is  produced  by  the  action  of  gaseous  silicium 
fluoride  on  aluminium,  and  forms  cubic  crystals,  volatilizing  at  a  red  heat, 
insoluble  in  water,  and  resisting  the  action  of  all  acids. 

Aluminium  and  Sodium  Fluoride,  Al2F6.6NaF,  occurs  abundantly,  as  cryolite, 
at  Evigtok  in  Greenland,  and  is  prepared  artificially  by  pouring  hydro- 
fluoric acid  in  excess  on  a  mixture  of  calcined  alumina  and  sodium  car- 
bonate. Cryolite  forms  quadratic  crystals,  colorless,  transparent,  softer 
than  felspar,  and  of  specific  gravity  2-96.  It  is  used,  as  already  mentioned, 
for  the  preparation  of  aluminium,  and  in  Germany  for  the  manufacture  of 
soda  for  the  use  of  soap-boilers. 

ALUMINIUM  OXIDE.  ALUMINA,  A1203. — This  substance  is  inferred  to  be 
a  sesquioxide  from  its  isomorphism  with  ferric  oxide.  It  is  prepared  by 
mixing  a  solution  of  alum  with  excess  of  ammonia,  by  which  an  extremely 
bulky,  white,  gelatinous  precipitate  of  aluminium  hydrate  is  thrown  down. 
This  is  washed,  dried,  and  ignited  to  whiteness.  Thus  obtained,  alumina 
constitutes  a  white,  tasteless,  coherent  mass,  very  little  acted  upon  by  acids. 
It  is  fusible  before  the  oxy-hydrogen  blowpipe.  The  mineral  called  corun- 
dum, of  which  the  ruby  and  sapphire  are  transparent  varieties,  consists  of 
nearly  pure  alumina  in  a  crystallized  state,  with  a  little  coloring  oxide: 
emery,  used  for  polishing  glass  and  metals,  is  a  coarse  variety  of  corundum. 
Alumina  is  a  very  feeble  base,  and  its  salts  have  often  an  acid  reaction. 

ALUMINIUM  HYDRATES. — Aluminium  forms  three  hydrates;  namely: 

Monohydrate     .         .     A1H02      orA!203.OH2 
Dihydrate      .         .          A12H405   orA!203.20H2 
Trihidrate          .         .     A12H606   or  A1203 .  30H2. 

The  monohydrate  is  found  native,  as  diaspore,  in  translucent  masses  which 
crumble  to  powder  when  heated,  and  give  off  the  whole  of  their  water  at 
360°. 

The  trihydrate  is  the  ordinary  gelatinous  precipitate  obtained  by  treating 
solutions  of  aluminium-salts  —  alum,  for  example  —  with  ammonia  or  al- 
kaline carbonates.  When  dried  at  a  moderate  heat,  it  forms  a  soft  friable 
mass,  which  adheres  to  the  tongue  and  forms  a  stiff  paste  with  water,  but 
does  not  dissolve  in  that  liquid.  At  a  strong  red  heat,  it  parts  with  its 
water,  and  undergoes  a  very  great  contraction  of  volume.  It  dissolves 
with  great  facility  in  acids,  and  in  the  fixed  caustic  alkalies.  When  a  solu- 
tion of  alumina  in  caustic  potash  is  exposed  to  the  air,  the  potash  absorbs 
carbonic  acid,  and  the  aluminium  trihydrate  is  then  deposited  in  white 
crystals,  which  are  but  sparingly  soluble  in  acids. 

Aluminium  trihydrate  has  a  very  powerful  attraction  for  organic  matter, 
and  when  digested  in  solutions  of  vegetable  coloring-matter,  combines  with 


ALUMINIUM.  335 


and  carries  down  the  coloring  matter,  which  is  thus  removed  entirely  from 
the  liquid  if  the  alumina  is  in  sufficient  quantity.  The  pigments  called 
lakes  are  compounds  of  this  nature.  The  fibre  of  cotton  impregnated  with 
alumina  acquires  the  same  power  of  retaining  coloring  matters :  hence  the 
great  use  of  aluminous  salts  as  mordants  to  produce  fast  colors. 

Aluminium  trihydrate  occurs  native  as  Gibbsite,  a  stalactitic,  translucent, 
fibrous  mineral,  easily  dissolved  by  acids. 

Dihydrate.  —  When  a  dilute  solution  of  aluminium  diacetate  is  exposed 
for  several  days  to  a  temperature  of  100°  in  a  close  vessel,  the  acetic  acid 
appears  to  be  set  free,  although  no  precipitation  of  alumina  takes  place. 
The  liquid  acquires  the  taste  of  acetic  aci.d,  and  if  afterwards  boiled  in  an 
open  vessel,  gives  off  nearly  the  whole  of  its  acetic  acid,  the  alumina  never- 
theless remaining  in  solution.  This  solution  is  coagulated  by  mineral  acids 
and  by  most  vegetable  acids,  by  alkalies,  and  by  decoctions  of  dye-woods. 
The  alumina  contained  in  it  is,  however,  no  longer  capable  of  acting  as  a 
mordant.  Its  coagulum  with  dye-woods  has  the  color  of  the  infusion,  but 
is  translucent  and  totally  different  from  the  dense  opaque  lakes  which 
ordinary  alumina  forms  with  the  same  coloring  matters.  On  evaporating 
the  solution  to  dryness  at  100°,  the  alumina  remains  in  the  form  of  dihy- 
drate,  retaining  only  a  trace  of  acetic  acid.  In  this  state  it  is  insoluble  in 
the  stronger  acids,  but  soluble  in  acetic  acid,  provided  it  has  not  been  pre- 
viously coagulated  in  the  manner  just  mentioned.  Boiling  potash  converts 
it  into  the  trihydrate.* 

Aluminates.  — The  hydrogen  in  aluminium  trihydrate  may  be  replaced  by 
an  equivalent  quantity  of  various  metals;  such  compounds  are  called 
acuminates.  According  to  Fremy,  a  solution  of  alumina  in  potash  slowly 
evaporated,  out  of  contact  with  the  air,  deposits  granular  crystals  of  po- 
tassium aluminate,  A1X//K02,  or  A1203.OK2.  Similar  compounds  occur  na- 
tive ;  thus  Spinell  is  an  aluminate  of  magnesium,  Al///2Mg//04 ;  Gahnite,  an 
aluminate  of  zinc,  Al///2Zn//04. 

ALUMINIUM  SULPHIDE,  A12S3.  —  When  the  vapor  of  carbon  bisulphide  is 
passed  over  alumina,  at  a  bright  red-heat,  a  glassy  melted  mass  remains, 
which  is  instantly  decomposed  by  water,  with  evolution  of  sulphuretted 
hydrogen. 

ALUMINIUM  SULPHATE,  (S04)SA1"'?.  180H2,  or  A1203.  3S03.180H2.— 
Prepared  by  saturating  dilute  sulphuric  acid  with  aluminium  hydrate,  and 
evaporating;  or,  on  the  large  scale,  by  heating  clay  with  sulphuric  acid. 
It  crystallizes  in  thin  pearly  plates,  soluble  in  2  parts  of  water ;  it  has  a 
sweet  and  astringent  taste,  and  an  acid  reaction.  Heated  to  redness,  it  is 
decomposed,  leaving  pure  alumina.  Two  other  aluminium  sulphates,  with 
excess  of  base,  are  also  described,  one  of  which  is  insoluble  in  water. 

Aluminium  sulphate  combines  with  the  sulphates  of  potassium,  sodium, 
and  ammonium,  and  the  other  alkali-metals,  forming  double  salts  of  great 
interest,  the  alums.  Common  alum,  the  source  of  all  the  preparations  of 
alumina,  contains  (S04)2A1///K.120H2.  It  is  manufactured  on  a  very  large 
scale  from  a  kind  of  slaty  clay,  loaded  with  iron  bisulphide,  which  abounds 
in  certain  localities.  This  is  gently  roasted,  and  then  exposed  to  the  air  in 
a  moistened  state ;  oxygen  is  absorbed  ;  the  sulphur  becomes  acidified ;  fer- 
rous sulphate  and  aluminium  sulphate  are  produced,  and  afterwards  sepa- 
rated by  lixiviation  with  water.  The  solution  is  next  concentrated,  and 
mixed  with  a  quantity  of  potassium  chloride,  which  decomposes  the  iron- 
salt,  forming  ferrous  chloride  and  potassium  sulphate:  the  latter  combines 
with  the  aluminium  sulphate  to  form  alum.  By  crystallization  the  alum  is 

*  Walter  Crum,  Chem.  Soc.  Journ.  vi.  225, 


336  EARTH-METALS. 

separated  from  the  highly  soluble  iron  chloride,  and  afterwards  easily  pu- 
rified by  a  repetition  of  the  process.  Other  methods  of  alum-making 
exist,  and  are  sometimes  employed.  Potassium-alum  crystallizes  in  colorless, 
transparent  octohedrons  which  often  exhibit  the  faces  of  the  cube.  It  has 
a  sweetish  and  astringent  taste,  reddens  litmus-paper,  and  dissolves  in  18 
parts  of  water  at  15-5°,  and  in  its  own  weight  of  boiling  water.  Exposed 
to  heat,  it  is  easily  rendered  anhydrous,  and  by  a  very  high  temperature  it 
is  decomposed.  The  crystals  have  little  tendency  to  change  in  the  air. 
Alum  is  largely  used  in  the  arts,  in  preparing  skins,  dyeing,  &c. :  it  is  oc- 
casionally contaminated  with  iron  oxide,  which  interferes  with  some  of  its 
applications.  The  celebrated  Roman  alum,  made  from  alum-stone,  a  fel- 
spathick  rock  altered  by  sulphurous  vapors,  was  once  much  prized  on  ac- 
count of  its  freedom  from  this  impurity.  A  mixture  of  dried  alum  and 
sugar,  carbonized  in  an  open  pan,  and  then  heated  to  redness  in  a  glass 
flask,  contact  with  air  being  avoided,  furnishes  the  pyrophorus  of  Homberg, 
which  ignites  spontaneously  on  exposure  to  the  atmosphere.  The  essential 
ingredient  is,  in  all  probability,  finely  divided  potassium  sulphide. 

Sodium-alum,  in  which  sulphate  of  sodium  replaces  sulphate  of  potassium, 
has  a  form  and  constitution  similar  to  that  of  the  salt  described:  it  is, 
however,  much  more  soluble,  and  difficult  to  crystallize. 

Ammonium- alum,  containing  NH4  instead  of  K,  very  closely  resembles 
common  potassium-alum,  having  the  same  figure,  appearance,  and  consti- 
tution, and  nearly  the  same  degree  of  solubility  as  that  substance.  It  is 
manufactured  for  commercial  use.  As  the  value  of  potassium  salts  is  con- 
tinually increasing,  ammonium-alum,  which  may  be  used  in  dyeing  with 
the  same  advantage  as  the  corresponding  potassium  salt,  has  almost  en- 
tirely replaced  the  potassium-alum.  When  heated  to  redness,  ammonium- 
alum  yields  pure  alumina. 

Cesium-alum,  (S04)2Al///Cs.l20H2,  and  Rubidium-alum,  (S04)2Al///Rb. 
120 H2,  resemble  potassium  alum.  K  silver  alum,  (S04)2Al///Ag.l20H2,  is 
formed  by  heating  equivalent  quantities  of  argentic  and  aluminium  sul- 
phates till  the  former  is  dissolved.  It  crystallizes  in  regular  octohedrons, 
and  is  resolved  by  water  into  its  component  salts.  There  is  also  a  thallium 
alum,  (S04)2A1///T1.120H2,  which  crystallizes  in  regular  octohedrons. 

Lastly,  there  are  alums  isomorphous  with  those  just  described,  in  which 
the  trivalent  aluminium  is  replaced  by  trivalent  iron,  chromium,  and  man- 
ganese: for  example,  potassio-ferric  sulphate  or  potassium  iron  alum,  (S04)2 
Fe'"K.120H2;  ammonio -chromic  sulphate,  (S04)2Cr'"NH4.120H2.  These 
will  be  described  further  on. 

Few  other  aluminium  salts  present  especial  interest,  except  the  silicates ; 
but  these  latter  are  of  great  importance.  Silicates  of  aluminium  enter 
into  the  composition  of  a  number  of  crystallized  minerals,  among  which 
felspar,  by  reason  of  its  abundant  occurrence,  occupies  a  prominent  place. 
Granite,  porphyry,  trachyte,  and  other  ancient  unstratified  rocks,  consist 
in  great  part  of  this  mineral,  which,  under  peculiar  circumstances  by  no 
means  well  understood,  and  particularly  by  the  action  of  the  carbonic  acid 
of  the  air,  suffer  complete  decomposition,  becoming  converted  into  a  soft, 
friable  mass  of  earthy  matter.  This  is  the  origin  of  clay ;  the  change  it- 
self is  seen  in  great  perfection  in  certain  districts  in  Devonshire  and  Corn- 
wall, the  felspar  of  the  fine  white  granite  of  those  localities  being  often 
disintegrated  to  an  extraordinary  depth,  and  the  rock  altered  to  a  substance 
resembling  soft  mortar.  By  washing,  this  finely  divided  matter  is  sepa- 
rated from  the  quartz  and  mica;  and  the  milk-like  liquid,  being  collected 
in  tanks  and  suffered  to  stand,  deposits  the  suspended  clay,  which  is  after- 
wards dried,  first  in  the  air,  and  afterwards  in  a  stove,  and  employed  in 
the  manufacture  of  porcelain.  The  composition  assigned  to  unaltered  fel- 
spar is  Si?OgAlK,  or  Si04AlK.2Si02,  or  6Si02.Al203.K20.  The  exact  nature 


BERYLLIUM,    Oii    GLUCINUM.  337 

of  the  change  by  which  felspar  passes  into  porcelain  clay  is  unknown,  al- 
though it  evidently  consists  in  the  abstraction  of  silica  arid  alkali. 

When  the  decomposing  rock  contains  iron  oxide,  the  clay  produced  is 
colored.  The  different  varieties  of  shale  and  slate  result  from  the  altera- 
tion of  ancient  clay-beds,  apparently  in  many  instances  by  the  infiltration 
of  water  holding  silica  in  solution:  the  dark  appearance  of  some  of  these 
deposits  is  due  to  bituminous  matter. 

It  is  a  common  mistake  to  confound  clay  with  alumina:  all  clays  are 
essentially  silicates  of  that  base;  they  often  vary  a  good  deal  in  composi- 
tion. Dilute  acids  exert  little  action  on  these  compounds;  but  by  boiling 
with  oil  of  vitriol,  alumina  is  dissolved  out,  and  finely  divided  silica  left 
behind.  Clays  containing  an  admixture  of  calcium  carbouate  are  termed 
marls,  and  are  recognized  by  effervescing  with  acids. 

A  basic  aluminium  silicate,  Al203.Si02,  is  found  crystallized,  constituting 
the  beautiful  mineral  called  cyanite.  The  compounds  formed  by  the  union 
of  the  aluminium  silicates  with  other  silicates  are  almost  innumerable.  A 
sodium  felspar,  albite,  containing  that  metal  in  place  of  potassium,  is  known, 
and  there  are  two  somewhat  similar  lithium-compounds,  spodumene  and  pe- 
talite.  The  zeolites  belong  to  this  class ;  analcime,  nepheline.  mesotype,  &c., 
are  double  silicates  of  sodium  and  aluminium,  with  water  of  crystallization. 
Stilbite,  heulandite,  laumontite,  prehnite,  &c.,  consist  of  calcium  silicate  com- 
bined with  silicate  of  aluminium.  The  garnets,  axinite,  mica,  &c.,  have  a 
similar  composition,  but  are  anhydrous.  Iron  sesquioxide  is  very  oftea 
substituted  for  alumina  in  these  minerals. 


Salts  of  aluminium,  when  moistened  with  cobalt  nitrate  and  heated  before 
the  blowpipe,  assume  a  characteristic  blue  color. 

Alumina,  when  in  solution,  is  distinguished  without  difficulty.  Caustic 
potash  and  soda  occasion  white  gelatinous  precipitates  of  aluminium  hy- 
drate, freely  soluble  in  excess  of  the  alkali.  Ammonia  produces  a  similar 
precipitate,  insoluble  in  excess  of  the  reagent.  The  alkaline  carbonates  and 
carbonate  of  ammonia  precipitate  the  hydrate,  with  escape  of  carbonic  acid. 
The  precipitates  are  insoluble  in  excess. 

Ammonium  sulphide  also  produces  a  white  precipitate  of  aluminium 
hydrate. 


BERYLLIUM,  or  GLUCINUM. 
Atomic  weight,  9-4.     Symbol,  Be. 

This  somewhat  rare  metal  occurs  as  a  silicate,  either  alone,  as  in  phena- 
cite,  or  associated  with  other  silicates,  as  beryl,  euclase,  leucophane,  hel- 
vite,  and  several  varieties  of  gadolinite ;  also  as  an  aluminate  in  chrysoberyl 
or  cymophane. 

Metallic  beryllium  is  obtained  by  passing  the  vapor  of  the  chloride  over 
melted  sodium.  It  is  a  white  metal  of  specific  gravity  2-1;  it  may  be 
forged  and  rolled  into  sheets  like  gold;  its  melting  point  is  below  that  of 
silver.  It  does  not  decompose  water  at  the  boiling  heat.  Sulphuric  and 
hydrochloric  acids  dissolve  it.  with  evolution  of  hydrogen. 

Beryllium  forms  but  one  class  of  compounds,  and  there  is  considerable 
doubt  as  to  its  atomic  weight  and  equivalent  value.  On  the  one  hand  it  is 
regarded  as  a  dyad,  like  calcium  and  magnesium,  with  the  atomic  weight 
9-4,  its  chloride  being  BeCl2,  its  oxide  BcO;  on  the  other  hand,  as  a  tetrad, 
like  aluminium,  with  apparent  tri-equivalojit  value,  on  which  supposition 
its  chlor'de  would  be  BeaC16,  its  oxide  Be.,O3,  and  its  atomic  weight  14;  but 


338  EARTH-METALS. 

the  former  view  appears,  on  the  whole,  to  be  most  in  accordance  with  ob- 
served facts. 

BERYLLIUM  CHLORIDE,  BeCl2,  is  formed  by  heating  the  metal  in  chlorine 
or  hydrochloric  acid  gas,  or  by  the  action  of  aqueous  hydrochloric  acid  on 
the  metal  or  its  oxide. 

The  anhydrous  chloride  is  prepared  by  passing  chlorine  over  an  ignited 
mixture  of  beryllia  and  charcoal.  It  is  less  volatile  than  aluminium  chlo- 
ride, very  deliquescent,  and  easily  soluble  in  water. 

BERYLLIUM  OXIDE.  BERYLLIA,  BeO.  —  This  earth  may  be  prepared  from 
beryl,  or  either  of  the  other  beryllium  silicates,  by  fusing  the  finely  pounded 
mineral  with  potassium  carbonate  or  quicklime;  treating  the  fused  mass 
with  hydrochloric  acid;  evaporating  to  dryness;  then  moistening  the  resi- 
due with  hydrochloric  acid,  and  treating  it  with  water,  whereby  every- 
thing is  dissolved  except  the  silica.  The  filtered  liquid  is  then  mixed  with 
excess  of  ammonia  solution,  which  throws  down  a  bulky  precipitate  con- 
taining both  alumina  and  beryllia;  this  precipitate  is  well  washed,  and  the 
beryllia  is  dissolved  out  from  the  alumina  by  digestion  in  a  cold  strong  so- 
lution of  ammonium  carbonate.  The  liquid  is  again  filtered,  and  on  boiling 
it,  beryllium  carbonate  is  deposited  as  a  white  powder,  which,  when  ignited, 
leaves  pure  beryllia. 

Beryllia  is  very  much  like  alumina  in  physical  characters,  and  further 
resembles  that  substance  in  being  readily  dissolved  by  caustic  potash  or 
soda;  but  it  is  distinguished  from  alumina  by  its  solubility,  when  recently 
precipitated,  in  a  cold  solution  of  ammonium  carbonate. 

Beryllium  salts  have  a  sweet  taste,  whence  the  former  name  of  the  metal, 
glucinum  (from  yAvKuj).  They  are  colorless,  and  are  distinguished  from  those 
of  aluminium  by  not  yielding  an  alum  with  potassium  sulphate,  nor  a  blue 
color  when  heated  before  the  blowpipe  with  cobalt  nitrate;  also  by  their 
reaction  with  ammonium  carbonate. 


ZIKCONIUM. 

Atomic  weight,  89-6.     Symbol,  Zr. 

This  is  a  tetrad  metal,  intermediate  in  many  of  its  properties  between 
aluminium  and  silicium.  Its  oxide,  zirconia,  was  first  obtained  by  Klap- 
roth,  in  1789,  from  zircon,  which  is  a  silicate  of  zirconium.  It  has  since 
been  found  in  ferguscnite,  eudialyte,  and  two  or  three  other  rare  minerals. 

Zirconium,  like  silicium,  is  capable  of  existing  in  three  different  states, 
amorphous,  crystalline,  and  graphitoi'dal.  The  amorphous  and  crystalline 
varieties  are  obtained  by  processes  similar  to  those  described  for  preparing 
the  corresponding  modifications  of  silicium;  graphitoi'dal  zirconium  was 
obtained,  by  Troost,  in  attempting  to  decompose  sodium  zirconate  with 
iron,  in  light  scales  of  a  steel-gray  color.  Amorphous  zirconium  when 
heated  in  the  air  takes  fire  at.  a  heat  somewhat  below  redness,  and  burns 
with  a  bright  light,  forming  zirconia.  Crystalline  zirconium  forms  very 
hard  brittle  scales  resembling  antimony  in  color  and  lustre;  it  burns  in  the 
air  only  at  the  heat  of  the  oxy-hydrogen  blowpipe,  but  takes  fire  at  n  red 
heat  in  chlorine  gas.  Zirconium  is  but  little  attacked  by  the  ordinary 
acids;  but  hydrofluoric  aoid  dissolves  it  readily,  with  evolution  of  hydrogen, 

ZIRCONIUM  OXIDE,  or  ZIROONIA,  Zr02,  is  prepared  by  strongly  igniting 
zircon  (zirconium  silicate)  with  four  times  its  weight  of  dry  sodium  carbon- 
ate and  a  small  quantity  qf  sodium  hydrate.  The  silica  is  separated  from 


•     ZIRCONIUM;  THORINUM,  OR  THORIUM.          339 

the  fused  mass  by  hydrochloric  acid,  as  described  in  the  case  of  beryllia ; 
the  resulting  solution  is  treated  with  ammonia,  which  throws  down  zirconia 
generally  mixed  with  ferric  oxide;  the  precipitate  is  redissolved  in  hydro- 
chloric acid;  and  the  solution  is  boiled  with  excess  of  sodium  hyposulphite 
as  long  as  sulphurous  acid  continues  to  escape,  whereby  pure  zirconia  is 
precipitated,  the  whole  of  the  iron  remaining  in  the  solution.  Zirconia 
thus  obtained  forms  a  white  powder  or  hard  lumps  of  specific  gravity  4-35 
to  4-9.  By  fusing  it  with  borax  in  a  pottery  furnace  and  dissolving  out 
the  soluble  salts  with  hydrochloric  acid,  zirconia  is  obtained  in  small  quad- 
ratic prisms,  isomorphous  with  the  native  oxides  of  tin  and  titanium. 

Zirconium  hydrates  are  obtained  by  precipitating  the  solution  of  a  zir- 
conium salt  with  ammonia;  the  precipitate  contains  ZrH203  =  Zr02.OH2, 
or  ZrH404  =  Zr02.20H2,  according  to  the  temperature  at  which  it  is  dried. 

Zirconia  acts  both  as  a  base  and  as  an  acid.  After  ignition  it  is  insoluble 
in  all  acids  except  hydrofluoric  and  very  strong  sulphuric  acid;  but  the 
hydrate  dissolves  easily  in  acids,  forming  the  zirconium  salts ;  the  normal 
sulphate  has  the  composition  (S04)2ZrlT,  or  S03.Zr02. 

Compounds  of  zirconia  with  the  stronger  bases,  called  zirconates,  are  ob- 
tained by  precipitating  a  zirconium  salt  with  potash  or  soda,  or  by  igniting 
zirconia  with  an  alkaline  hydrate.  Potassium  zirconate  dissolves  completely 
in  water.  Three  sodium  zirconates  have  been  formed,  containing  Zr03Na2  = 
Zr02.ONa2 ;  Zr04Na4  =  Zr02.20Na2 ;  and  Zr8017Na2  =  8Zr02  ONa2. 

ZIRCONIUM  FLUORIDE,  ZrF4. — This  compound  is  obtained  by  dissolving 
zirconia,  or  the  hydrate,  in  hydrofluoric  acid  ;  or  in  the  anhydrous  state, 
by  igniting  zirconia  with  ammonium  and  hydrogen  fluoride  (p.  270)  till  all 
the  ammonium  fluoride  is  driven  off.  It  unites  with  other  metallic  fluorides, 
forming  double  salts,  called  zircofluorides  or  fluozirconales,  which  are  isomor- 
phous with  the  corresponding  silicofluorides,  stannofluorides,  and  titano- 
fluorides,  and  are  mostly  represented  by  the  formulae 

4MF.ZrF4;     3MF.ZrF4;     2MF.ZrF4;     MF.ZrF4, 

in  which  M  denotes  a  monad  metal.     The  sodium  salt,  however,  has  the 
composition  5NaF.3ZrF4. 


THORINUM,  or  THORIUM. 
Atomic  weight,  115-75.     Symbol,  Th. 

This  very  rare  metal  was  discovered  in  1828  by  Berzelius,  in  thorite,  a 
mineral  from  the  Norwegian  island  Lovon,  in  which  it  exists  as  a  silicate. 
It  has  since  been  found  in  euxenite,  pyrochlore,  and  a  few  other  minerals, 
all  very  scarce. 

Metallic  thorinum  is  obtained  by  reducing  the  chloride  with  potassium 
or  sodium,  as  a  gray  powder,  which  acquires  metallic  lustre  by  pressure, 
and  has  a  density  of  7-66  to  7-9.  It  is  not  oxidized  by  water,  dissolves  easily 
in  nitric,  slowly  in  hydrochloric  acid,  and  is  not  attacked  by  caustic  alkalies. 

Thorinum  forms  but  one  class  of  compounds,  in  all  of  which  it  is  bivalent. 

THORINUM  OXIDE,  or  THORINA,  ThO,  is  prepared  by  decomposing  thorite 
with  hydrochloric  acid,  separating  the  silica  in  the  usual  way,  treating  the 
filtered  solution  with  hydrogen  sulphide  to  separate  lead  and  tin,  and  pre- 
cipitating the  thorina  by  ammonia,  together  with  small  quantities  of  the 
oxides  of  iron,  manganese,  and  uranium.  To  get  rid  of  these,  the  precipi- 
tate is  redissolved  in  hydrochloric  acid,  and  the  hot  saturated  solution  is 
boiled  with  a  solution  of  neutral  potassium  sulphate.  The  thorinum  is 


340  EARTH-METALS. 

thereby  precipitated  as  thorinum  and  potassium  sulphate ;  and  from  the 
solution  of  this  salt  in  hot  water,  the  thorinum  is  precipitated  as  a  hydrate, 
which,  on  ignition,  yields  pure  thorina. 

Thorina  is  white,  and  very  heavy,  its  specific  gravity  being  9.402.  After 
ignition  it  is  insoluble  in  nitric  and  hydrochloric  acids,  and  dissolves  in 
strong  sulphuric  acid  only  after  prolonged  heating.  The  hydrate  precipi- 
tated from  thorinum  salts  by  alkalies  dissolves  easily  in  acids. 

THORINUM  CHLORIDE,  ThCl2,  prepared  by  igniting  an  intimate  mixture  of 
thorina  and  charcoal  in  chlorine  gas,  sublimes  in  white  shining  crystals. 
It  forms  double  salts  Avith  the  chlorides  of  the  alkali-metals. 

THORINUM  SULPHATE,  S04Thx/,  crystallizes  with  various  quantities  of 
water,  according  to  the  temperature  at  which  its  solution  is  evaporated. 
Thorinum  and  potassium  sulphate,  (SO4)2Th//K2.  OH2,  separates  as  a  crystalline 
powder  when  a  crust  of  potassium  sulphate  is  suspended  in  a  solution  of 
thorinum  sulphate.  It  is  easily  soluble  in  water,  but  insoluble  in  alcohol 
and  in  solution  of  potassium  sulphate. 


CERIUM.  —  LANTHANUM.  —  DIDYMITIM. 

Ce  ==  92.  —  La  =  92-8.—  Di  =  96. 

These  three  metals  occur  together  as  silicates  in  the  Swedish  mineral 
cerite,  also  in  allanite,  orthite,  and  a  few  others  ;  and  as  phosphates  in 
monazite,  edwardsite,  and  crypt  olite,  a  mineral  occurring  disseminated 
through  apatite  and  through  certain  cobalt  ores. 

Cerium  was  discovered  in  1803  by  Klaproth,  and  by  Hisinger  and  Ber- 
zelius,  who  obtained  it  in  the  form  of  oxide  from  cerite.  This  mineral  is 
completely  decomposed  by  boiling  with  strong  hydrochloric  acid,  silica 
being  separated,  and  the  cerium,  together  with  iron  and  other  metals,  dis- 
solving as  chloride.  On  treating  the  acid  solution  thus  obtained  with  oxalic 
acid,  cerium  oxalate  is  precipitated  as  a  white  crystalline  powder,  which, 
when  ignited,  leaves  a  brown  oxide.  The  product  thus  obtained  was  for 
some  time  regarded  as  the  oxide  of  a  single  metal,  cerium;  but  in  1839  and 
1841,  Mosander*  showed  that  it  contained  the  oxides  of  two  other  metals, 
which  he  designated  as  lanthanum^  and  didymium.\ 

Cerium  oxide  may  be  separated  from  the  oxides  of  lanthanum  and  didy- 
mium  by  treating  the  crude  brown  oxide  above  mentioned,  first  with  dilute 
and  then  with  strong  nitric  acid,  which  gradually  removes  the  whole  of  the 
lanthanum  and  didymium  oxides. 

The  separation  of  these  two  oxides  one  from  the  other  is  much  more  diffi- 
cult, and  can  be  effected  only  by  successive  crystallization  of  their  sul- 
phates. If  the  lanthanum  salt  is  in  excess,  in  which  case  the  solution  of 
the  mixed  sulphates  has  only  a  faint  amethyst  tinge,  the  liquid  is  evaporated 
to  dryness,  and  the  residue  heated  to  a  temperature  just  below  redness,  to 
render  the  sulphates  anhydrous.  The  residue  thus  obtained  is  then  to  be 
added  by  small  portions  to  ice-cold  water,  in  which  it  dissolves  easily,  and 
the  resulting  solution  heated  in  a  water-bath  to  about  40°.  Lanthanum  sul- 
phate then  crystallizes  out,  containing  only  a  small  quantity  of  didymium, 
and  may  be  further  purified  by  repeating  the  whole  process.  If,  on  the 
other  hand,  the  didymium  salt  is  in  excess,  in  which  case  the  liquid  has  a 


*  Poggendorff's  Annalen,  xlvi.  648;  xlvii.  207;  Ivi.  504.  %  From  titvuot,  twins. 

f  From  Xavddvetv,  to  lie  hid. 


CERIUM;  LANTHAMUM;  DIDYMIUM.  341 

decided  rose  color,  separation  may  be  effected  by  leaving  the  acid  solution 
in  a  warm  place  for  a  clay  or  two.  Didymium  sulphate  then  separates  in 
large  rhombohedral  crystals. 

Metallic  cerium,  lanthanum,  and  didymium  are  obtained  by  reducing 
the  chlorides  with  sodium,  in  the  form  of  gray  powders,  which  decompose 
water  at  ordinary  temperatures,  and  dissolve  rapidly  in  dilute  acids  with 
evolution  of  hydrogen. 

Cerium  forms  three  series  of  compounds :  the  cerous  compounds,  in  which  it 
is  bivalent,  e.  g.,  CeCl2,  CeO,  CeS04;  the  eerie  compounds,  in  which  it  is  ap- 
parently trivalent,  but  really  quadrivalent,  like  the  ferric  salt,  e.  g.,  eerie 

CeF3 
fluoride,   Ce2F6  =    |         ;  and  the   ceroso-ceric  compounds,   of  intermediate 

CeF3 

composition,  and,  perhaps,  consisting  of  compounds  of  the  other  two,  e.  ff., 
ceroso-ceric  oxide,  Ce3O4  =  CeO.Ce203. 

Cerous  oxide,  CeO,  is  obtained  by  igniting  the  carbonate  or  oxalate  in  a 
current  of  hydrogen,  as  a  grayish-blue  powder,  quickly  converted  into 
ceroso-ceric  oxide  on  exposure  to  the  air.  Its  salts  are  colorless.  The 
sulphate,  S04Ce,  crystallizes  with  various  quantities  of  water,  according  to 
the  temperature  at  which  it  is  deposited.  Cerium  and  potassium  sulphate, 
(S04)2CeK2,  separates  as  a  white  powder  on  immersing  solid  potassium  sul- 
phate in  a  solution  of  a  cerous  salt.  It  is  slightly  soluble  in  pure  water, 
but  insoluble  in  a  saturated  solution  of  potassium  sulphate.  The  forma- 
tion of  this  salt  affords  the  means  of  separating  cerium  from  most  other 
metals. 

The  only  eerie  compounds  actually  known  are  the  fluoride,  Ce2F6,  already 
mentioned,  which  may  be  obtained  as  a  yellow  precipitate,  and  likewise 
occurs  native  as  fluocerite,  and  an  oxy fluoride,  Ce4F603,  occurring  as  fluo- 
cerine  at  Finnbo,  in  Sweden. 


Ceroso-ceric  oxide,*  Ce3  04,  or          Ce        ,    analogous   in   composition    to 

I   >0 
0  =  Ce 

ferrosoferric  or  magnetic  iron  oxide,  is  produced  when  cerous  hydrate, 
carbonate,  or  nitrate  is  ignited  in  an  open  vessel.  It  is  yellowish-white, 
acquires  a  deep  orange-red  color  when  heated,  but  recovers  its  original 
tint  on  cooling.  It  is  not  converted  into  a  higher  order  by  ignition  in 
hydrogen.  Ceroso-ceric  hydrate,  Ce304.  30H2,  obtained  by  passing  chlorine 
into  aqueous  potash  in  which  cerous  hydrate  is  suspended,  is  a  bright- 
yellow  precipitate,  which  dissolves  readily  in  sulphuric  and  nitric  acids, 
forming  yellow  solutions  of  ceroso-ceric  salts;  and  in  hydrochloric  acid, 
with  evolution  of  chlorine,  forming  colorless  cerous  chloride. 

The  solution  of  the  sulphate  yields  by  spontaneous  evaporation,  first, 
brown-red  crystals  of  the  salt,  (S04)6Ce5.  18  aq.,  or  SSC^Ce".  (S04)3Ce///2. 
18  aq.,  and  afterwards  a  yellow  indistinctly  crystalline  salt,  containing 
S04Ce".  (S04)sCe'"2. 18  aq.f 

All  ceroso-ceric  compounds,  when  heated  with  hydrochloric  acid,  give 
off  chlorine,  and  are  reduced  to  the  corresponding  cerous  compounds;  thus: 

Ce304        +       8HC1       =       3CeCl2       +       4°H2     +     Clr 
Ceroso-ceric  oxide.  Cerous  chloride. 

*  A  sesquioxide,  C^Og,  is  commonly  said  to  exist,  and  is  designated  as  eerie  oxide,  but  there 
is  no  proof  of  its  existence;  neither  are  any  salts  of  analogous  composition  known  with  cer- 
tainty. 

t  The  symbol  aq.  (abbreviation  of  aqua)  is  often  used  to  denote  water  of  crystallization. 

29* 


342  EARTH-METALS. 

Lanthanum  is  bivalent,  forming  only  one  set  of  compounds,  viz.  g, 

LaO,  LaS04.  There  is,  however,  a  higher  oxide,  the  composition  of  which 
is  not  exactly  known.  Lanthanum  salts  are  colorless ;  their  solutions  yield, 
with  alkalies,  a  precipitate  of  lanthanum  hydrate,  LaH202,  or  LaO .  OH2, 
which,  when  ignited,  leaves  the  white  anhydrous  monoxide.  Both  the  hy- 
drate and  the  anhydrous  oxide  dissolve  easily  in  acids.  Lanthanum  sulphate 
forms  small  prismatic  crystals,  containing  S04La .  30H2.  Lanthanum  and 
potassium  sulphate,  (S04)2LaK2,  is  formed,  on  mixing  the  solution  of  a  lan- 
thanum salt  with  potassium  sulphate,  as  a  white  crystalline  precipitate, 
resembling  the  corresponding  cerium  salt. 

Didymium  is  also  bivalent ;  its  salts  are  rose-colored,  and  their  solutions 
give,  with  alkalies,  a  pale  rose-colored  precipitate  of  the  hydrate,  DiH202, 
which,  when  ignited  in  a  covered  crucible,  leaves  the  anhydrous  monoxide, 
DiO,  in  white,  hard  lumps.  When,  however,  the  hydrate,  nitrate,  carbon- 
ate, or  oxalate  of  didymium  is  heated  in  contact  with  the  air,  and  not 
very  strongly,  a  dark-brown  peroxide  is  left,  containing  from  0-8  to  0-9  per 
cent,  oxygen  more  than  the  monoxide.  This,  when  treated  with  acids, 
dissolves  readily,  giving  off  oxygen  and  yielding  a  salt  of  the  monoxide. 

Didymium  sulphate  separates  from  an  acid  solution,  by  spontaneous 
evaporation,  in  well-defined  rhombohedral  crystals,  exhibiting  numerous 
secondary  faces,  and  containing  3S04Di .  8  aq. :  they  are  isomorphous  with 
the  similarly  constituted  sulphates  of  yttrium,  erbium,  and  cadmium.  The 
sulphate  is  more  soluble  in  cold  than  in  hot  water,  and  a  solution  saturated 
in  the  cold  deposits,  when  heated  to  the  boiling-point,  a  crystalline  powder 
containing  S04Di  •  2  aq. 

Didymium  and  potassium  sulphate,  (S04)2DiK2,  resembles  the  lanthanum 
salt. 

Solutions  of  didymium  salts  exhibit  a  well-marked  absorption  spectrum,* 
containing  two  black  lines  inclosing  a  very  bright  space.  One  of  these 
black  lines  is  in  the  yellow,  immediately  following  Fraunhofer's  line  D; 
the  other  is  situated  between  E  and  b.  These  characters  can  be  distinctly 
recognized  in  a  solution  half  an  inch  deep,  containing  only  O'Ol  per  cent, 
of  didymium  salt.  Lanthanum  salts  do  not  exhibit  an  absorption  spectrum 
(Gladstone). 


YTTRIUM  AND  ERBIUM. 

Y  =  61-7.     Eb  =  112-6. 

These  metals  exist  as  silicates  in  the  gadolinite  or  ytterbite  of  Ytterby  in 
Sweden,  and  in  a  few  other  rare  minerals.  A  third  metal,  called  terbium, 
has  also  been  supposed  to  be  associated  with  them ;  but  recent  experiments, 
especially  those  of  Bahr  and  Bunsen,f  have  thrown  very  great  doubt  upon 
its  existence. 

To  obtain  the  earths,  yttria  and  erbia,  in  the  separate  state,  gadolinite 
is  digested  with  hydrochloric  acid,  and  the  solution  separated  from  the 
silica  is  treated  with  oxalic  acid,  which  throws  down  the  oxalates  of  erbium 
and  yttrium,  together  with  those  of  calcium,  cerium,  lanthanum,  and  didy- 
mium. These  oxalates  are  converted  into  nitrates;  the  solution  is  treated 
with  excess  of  solid  potassium  sulphate,  to  separate  the  cerium  metals; 
the  erbium  and  yttrium,  which  still  remain  in  solution,  are  again  precipi- 
tated by  oxalic  acid;  and  the  same  treatment  is  repeated,  till  the  solution 
of  t,he  mixed  earths,  when  examined  by  the  spectral  apparatus,  no  longer 
exhibits  the  absorption  bands  characteristic  of  didymium.  To  separate 

*  See  LIGHT,  p.  90.  f  Ann.  Ch.  Pharm.  cxxxvii.  1. 


EARTH-METALS.  343 

the  erbia  and  yttria,  they  are  again  precipitated  by  oxalic  acid.  The  oxa- 
lates  are  converted  into  nitrates,  and  the  nitrates  of  erbium  and  yttrium 
are  separated  by  a  series  of  fractional  crystallizations,  the  erbium  salt 
being  the  less  soluble  of  the  two,  and  crystallizing  out  first;  but  the  pro- 
cess requires  attention  to  a  number  of  details,  which  cannot  be  here  de- 
scribed.* 

Metallic  erbium  has  not  been  isolated.  Yttrium  (containing  erbium) 
was  obtained  by  Berzelius,  as  a  blackish-gray  powder,  by  igniting  yttrium 
chloride  with  potassium. 

Erbia,  Eb/X0,  obtained  by  ignition  of  erbium  nitrate  or  oxalate,  has  a 
faint  rose  color.  It  does  not  melt  at  the  strongest  white  heat,  but  aggre- 
gates to  a  spongy  mass,  glowing  with  an  intense  green  light,  which,  when 
examined  by  the  spectroscope,  exhibits  a  continuous  spectrum  intersected 
by  a  number  of  bright  bands.  Solutions  of  erbium-salts,  on  the  other 
hand,  give  an  absorption-spectrum  exhibiting  dark  bands,  and  the  points 
of  maximum  intensity  of  the  light  bands  in  the  emission- spectrum  of  glowing  erbia 
coincide  exactly  in  position  with  the  points  of  greatest  darkness  in  the  absorption- 
spectrum.  The  position  of  these  bands  is  totally  different  from  those  in  the 
emission  and  absorption-spectra  of  didymium. •)• 

Erbium  salts  have  a  rose-red  color,  deeper  in  the  hydrated  than  in  the 
anhydrous  state ;  they  have  an  acid  reaction  and  sweet  astringent  taste. 
The  sulphate,  3S04Eb/x  .  8aq.,  forms  light  rose-colored  crystals,  isomorphous 
with  the  sulphates  of  yttrium  and  didymium. 

Yttria,  Yx/0,  is  a  soft,  nearly  white  powder,  which  when  ignited  glows 
with  a  pure  white  light,  and  yields  a  spectrum  not  containing  any  bright 
bands,  like  that  of  erbia.  It  does  not  unite  directly  with  water,  but  is 
precipitated  as  a  hydrate  by  alkalies,  from  solutions  of  yttrium-salts.  It 
dissolves  slowly  but  completely  in  hydrochloric,  nitric,  and  sulphuric  acids, 
forming  colorless  solutions,  which  do  not  exhibit  an  absorption-spectrum. 

Yttrium  sulphate,  3S04Y/X.  8aq.,  forms  small  colorless  crystals. 


Reactions  of  the  Earth-Metals. 

1.  All  these  metals  are  precipitated  from  their  solutions  by  ammonium 
sulphide,   as  hydrates,  not  as  sulphides.     They  are  not  precipitated  by 
hydrogen  sulphide. 

2.  The  hydrates  of  aluminium  and  beryllium  are  soluble  in  caustic  pot- 
ash; those  of  the  other  earth-metals  are  insoluble. 

3.  Beryllium  hydrate  dissolves  in  a  cold  saturated  solution  of  ammonium 
carbonate,  and  is  precipitated,  as  carbonate,  on  boiling.    Aluminium  hydrate 
is  insoluble  in  ammonium  carbonate  (see  further,  p.  337). 

4.  Of  the  earth-metals  whose  hydrates  are  insoluble  in  potash,  —  namely, 
zirconium,  thorinum,  cerium,  lanthanum,  didymium,  erbium,  and  yttrium, 
—  zirconium  and  thorinum  may  be  precipitated  as  hyposulphites  by  boiling 
the  solution  with  sodium  hi/posulphite,  the  other  metals  remaining  in  solution. 
The  precipitate  when  ignited  leaves  pure  z-irconia  or  thorina,  or  a  mixture 
of  the  two. 

5.  Zirconium  and  thorinum  may  be  separated   one  from  the  other  by 
means  of  ammonium  oxalate,  which,  when  added  in  excess,  precipitates  the 
thorinum  as  oxalate,  and  leaves  the  zirconium  in  solution. 

6.  Cerium,  lanthanum,  and  didymium  are  separated  from  yttrium  and 
erbium  by  adding  an  excess  of  potassium  sulphate,  which  throws  down  the 

*  See  Watts'*  Dictionary  of  Chemistry,  vol  v.  p.  721. 

f  The  paper  by  Tiahr  and  Bnusen.  above  referred  to,  is  accompanied  by  exact  diagrams  of  the 
erbium  and  didymitun  sport ra. 


344:  EARTH-METALS. 

cerium  metals,  leaving  yttrium  and  erbium  in  solution ;  to  insure  complete 
precipitation,  the  solution  must  be  left  in  contact  for  some  time  with  a 
piece  of  solid  potassium  sulphate 

Cerium  may  be  separated  from  lanthanum  and  didymium,  as  already 
observed,  by  treating  the  mixed  oxides  several  times  with  nitric  acid  (p. 
340).  Another  method  is  to  boil  the  mixed  oxides  (the  cerium  being  in 
the  state  of  ceroso-ceric  oxide)  with  solution  of  sal-ammoniac.  The  lantha- 
num and  didymium  then  gradually  dissolve,  as  chlorides,  while  the  cerium 
remains  as  ceroso-ceric  oxide.  A  third  method  is  to  precipitate  the  solu- 
tion of  the  three  metals  with  excess  of  potash,  and  pass  chlorine  in  excess 
through  the  solution  and  precipitate ;  the  cerium  is  then  separated  as 
bright-yellow  ceroso-ceric  hydrate,  while  the  lanthanum  and  didymium 
redissolve  as  chlorides.  This  reaction  serves  to  detect  very  small  quanti- 
ties of  cerium  mixed  with  the  other  two  metals.  Cerium  is  further  distin- 
guished by  the  light-yellow  color  of  anhydrous  ceroso-ceric  oxide,  and  by 
the  reaction  of  its  compounds  when  fused  before  the  blow-pipe  with  borax 
or  phosphorus  salt,  the  glass  thus  formed  being  deep-red  while  hot,  and 
becoming  colorless  on  cooling.  Didymium  is  distinguished  by  the  dark- 
brown  color  of  its  higher  oxide;  by  the  pale  rose-color  which  its  salts 
impart  to  a  bead  of  borax  or  phosphorus  salt;  and  by  the  peculiar  character 
of  its  absorption  spectrum  (p.  342). 

The  methods  of  separating  lanthanum  from  didymium,  and  yttrium  from 
erbium  —  imperfect  at  the  best — have  been  already  noticed. 

MANUFACTURE  OF  GLASS,  PORCELAIN,  AND  EARTHENWARE. 

Glass.  —  Glass  is  a  mixture  of  various  insoluble  silicates  with  excess  of 
silica,  altogether  destitute  of  crystalline  structure ;  the  simple  silicates, 
formed  by  fusing  the  bases  with  silicic  acid  in  equivalent  proportions,  very 
often  crystallize,  which  happens  also  with  the  greater  number  of  the  natural 
silicates  included  among  the  earthy  minerals.  Compounds  identical  with 
some  of  these  are  also  occasionally  formed  in  artificial  processes,  where 
large  masses  of  melted  glassy  matter  are  suffered  to  cool  slowly.  The 
alkaline  silicates,  when  in  a  state  of  fusion,  have  the  power  of  dissolving 
a  large  quantity  of  silica. 

Two  principal  varieties  of  glass  are  met  with  in  commerce — namely, 
glass  composed  of  silica,  alkali,  and  lime,  and  glass  containing  a  large 
proportion  of  lead  silicate  ;  crown  and  plate  glass  belong  to  the  former  di- 
vision ;  flint  glass,  and  the  material  of  artificial  gems,  to  the  latter.  The 
lead  promotes  fusibility,  and  confers  also  density  and  lustre.  Common 
green  bottle-glass  contains  no  lead,  but  much  silicate  of  iron,  derived  from 
the  impure  materials.  The  principle  of  the  glass  manufacture  is  very  sim- 
ple. Silica,  in  the  shape  of  sand,  is  heated  with  potassium  or  sodium  car- 
bonate, and  slaked  lime  or  lead  oxide ;  at  a  high  temperature,  fusion  and 
combination  occur,  and  the  carbonic  acid  is  expelled.  Glauber's  salt  mixed 
with  charcoal  is  sometimes  substituted  for  soda.  When  the  melted  mass 
has  become  perfectly  clear  and  free  from  air-bubbles,  it  is  left  to  cool  until 
it  assumes  the  peculiar  tenacious  condition  proper  for  working. 

The  operation  of  fusion  is  conducted  in  large  crucibles  of  refractory 
fire-clay,  which  in  the  case  of  lead-glass  are  covered  by  a  dome  at  the  top, 
and  have  an  opening  at  the  side,  by  which  the  materials  are  introduced, 
and  the  melted  glass  withdrawn.  Great  care  is  exercised  in  the  choice  of 
the  sand,  which  must  be  quite  white  and  free  from  iron  oxide.  Red  lead, 
one  of  the  higher  oxides,  is  preferred  to  litharge,  although  immediately 
reduced  to  monoxide  by  the  heat,  the  liberated  oxygen  serving  to  destroy 
any  combustible  matter  that  might  accidentally  find  its  way  into  the  crucible, 
and  stain  the  glass  by  reducing  a  portion  of  the  lead.  Potash  gives  a  better 


MANUFACTURE    OF    GLASS.  345 

glass  than  soda,  although  the  latter  is  very  generally  employed,  from  its 
lower  price.  A  certain  proportion  of  broken  and  waste  glass  of  the  same 
kind  is  always  added  to  the  other  materials. 

Articles  of  blown  glass  are  thus  made  :  The  workman  begins  by  collecting 
a  proper  quantity  of  soft  pasty  glass  at  the  end  of  his  blowpipe,  an  iron 
tube  five  or  six  feet  in  length,  terminated  by  a  mouthpiece  of  wood ;  he 
then  begins  blowing,  by  which  the  lump  is  expanded  into  a  kind  of  flask, 
susceptible  of  having  its  form  modified  by  the  position  in  which  it  is  held, 
and  the  velocity  of  rotation  continually  given  to  the  iron  tube.  If  an  open- 
mouthed  vessel  is  to  be  made,  an  iron  rod,  called  a  pontil  or  puntil,  is  dipped 
into  the  glass  pot  and  applied  to  the  bottom  of  the  flask,  to  which  it  thus 
serves  as  a  handle,  the  blowpipe  being  removed  by  the  application  of  a 
cold  iron  to  the  neck.  The  vessel  is  then  re-heated  at  a  hole  left  for  the 
purpose  in  the  wall  of  the  furnace,  and  the  aperture  enlarged,  and  the 
vessel  otherwise  altered  in  figure  by  the  aid  of  a  few  simple  tools,  until 
completed.  It  is  then  detached,  and  carried  to  the  annealing  oven,  where 
it  undergoes  slow  and  gradual  cooling  during  many  hours,  the  object  of 
which  is  to  obviate  the  excessive  brittleness  always  exhibited  by  glass  which 
has  been  quickly  cooled.  The  large  circular  tables  of  crown  glass  are  made  by 
a  very  curious  process  of  this  kind :  the  globular  flask  at  first  produced, 
transferred  from  the  blowpipe  to  the  pontil,  is  suddenly  made  to  assume 
the  form  of  a  flat  disc  by  the  centrifugal  force  of  the  rapid  rotatory  move- 
ment given  to  the  rod.  Plate  glass  is  cast  upon  a  flat  metal  table,  and,  after 
very  careful  annealing,  ground  true  and  polished  by  suitable  machinery. 
Tubes  are  made  by  rapidly  drawing  out  a  hollow  cylinder ;  and  from  these 
a  great  variety  of  useful  small  apparatus  may  be  constructed  with  the  help 
of  a  lamp  and  blowpipe,  or,  still  better,  the  bellows-table  of  the  barometer- 
maker.  Small  tubes  may  be  bent  in  the  flame  of  a  spirit-lamp  or  gas  jet, 
and  cut  with  great  ease  by  a  file,  a  scratch  being  made,  and  the  two  por- 
tions pulled  or  broken  asunder  in  a  way  easily  learned  by  a  few  trials. 

Specimens  of  the  two  chief  varieties  of  glass  gave  the  following  results 
on  analysis : 


English  flint  glass.f 
Silica         .         .         .     51-93 
Potassium  oxide   .          13-77 
Lead  oxide  33-28 


Bohemian  plate  glass  (excellent).* 
Silica          .         .         .     60-0 
Potassium  oxide     .          25-0 
Lime          .        .         .     12-5 

97-5 

The  difficultly  fusible  white  Bohemian  tube,  so  valuable  in  organic  analysis, 
has  been  found  to  contain,  in  100  parts : 

Silica 72-80 

Lime,  with  trace  of  alumina        .         .         .  9-68 

Magnesia         .......  -40 

Potassium  oxide 16-80 

Traces  of  manganese,  &c.,  and  loss         .         .  *32 

Different  colors  are  often  communicated  to  glass  by  metallic  oxides. 
Thus,  oxide  of  cobalt  gives  deep  blue;  oxide  of  manganese,  amethyst; 
cuprous  oxide,  ruby-red  ;  cupric  oxide,  green ;  the  oxides  of  iron,  dull  green 
or  brown,  &c.  These  are  either  added  to  the  melted  contents  of  the  glass- 
pot,  in  which  they  dissolve,  or  applied  in  a  particular  manner  to  the  surface 
of  the  plate  or  other  object,  which  is  then  reheated,  until  fusion  of  the 
coloring  matter  occurs  :  such  is  the  practice  of  enamelling  and  glass-paint- 

*  Mitscherlich,  Lehrbuch,  ii.  187.  t  Faraday. 


346  DYAD    METALS. 

ing.     An  opaque  white  appearance  is  given  by  oxide  of  tin;  the  enamel 
of  watch-faces  is  thus  prepared. 

When  silica  is  melted  with  twice  its  weight  of  potassium  or  sodium  car- 
bonate, and  the  product  treated  with  water,  the  greater  part  dissolves,  yield- 
ing a  solution  from  which  acids  precipitate  gelatinous  silica.  This  is  the 
soluble  glass  of  Professor  Fuchs :  its  solution  has  been  used  for  rendering 
muslin  and  other  fabrics  of  cotton  or  linen  less  combustible,  for  making 
artificial  stone,  and  preserving  natural  stone  from  decay,  and  for  a  peculiar 
style  of  mural  painting  called  stereochromy.* 

Porcelain  and  Earthenware.  —  The  plasticity  of  natural  clays,  and  their 
hardening  when  exposed  to  heat,  are  properties  which  suggested  in  very 
early  times  their  application  to  the  making  of  vessels  for  the  various  pur^ 
poses  of  daily  life :  there  are  few  branches  of  industry  of  higher  antiquity 
than  that  exercised  by  the  potter. 

True  porcelain  is  distinguished  from  earthenware  by  very  obvious  char- 
acters. In  porcelain  the  body  of  the  ware  is  very  compact  and  translucent, 
and  breaks  with  a  conchoi'dal  fracture,  symptomatic  of  a  commencement  of 
fusion.  The  glaze,  too,  applied  for  giving  a  perfectly  smooth  surface,  is 
closely  adherent,  and,  in  fact,  graduates  by  insensible  degrees  into  the  sub- 
stance of  the  body.  In  earthenware,  on  the  contrary,  the  fracture  is  open 
and  earthy,  and  the  glaze  detachable  with  greater  or  less  facility.  The 
compact  and  partly  glassy  character  of  porcelain  is  the  result  of  the  admix- 
ture with  the  clay  of  a  small  portion  of  some  substance  which  is  fusible  at 
the  temperature  to  which  the  ware  is  exposed  when  baked  or  fired,  and 
being  absorbed  by  the  more  infusible  portion,  binds  the  whole  into  a  solid 
mass  on  cooling:  such  substances  are  found  in  felspar,  and  in  a  small 
admixture  of  calcic  or  alkaline  silicate.  The  clay  employed  in  porcelain- 
making  is  always  directly  derived  from  decomposed  felspar,  none  of  the 
clays  of  the  secondary  strata  being  pure  enough  for  the  purpose:  it  must 
be  white,  and  free  from  iron  oxide.  To  diminish  the  contraction  which  this 
substance  undergoes  in  the  fire,  a  quantity  of  finely  divided  silica,  carefully 
prepared  by  crushing  and  grinding  calcined  flints  or  chert,  is  added, 
together  with  a  proper  proportion  of  felspar  or  other  fusible  material,  also 
reduced  to  impalpable  powder.  The  utmost  pains  are  taken  to  effect  per- 
fect uniformity  of  mixture,  and  to  avoid  the  introduction  of  particles  of 
grit,  or  other  foreign  bodies.  The  ware  itself  is  fashioned  either  on  the 
potter's  wheel  —  a  kind  of  vertical  lathe  —  or  in  moulds  of  plaster  of  Paris, 
and  dried  first  in  the  air,  afterwards  by  artificial  heat,  and  at  length  com- 
pletely hardened  by  exposure  to  the  temperature  of  ignition.  The  porous 
biscuit  is  now  fit  to  receive  its*glaze,  which  may  be  either  ground  felspar,  or 
a  mixture  of  gypsum,  silica,  and  a  little  porcelain  clay,  diffused  through 
water.  The  piece  is  dipped  for  a  moment  into  this  mixture,  and  withdrawn  ; 
the  water  sinks  into  its  substance,  and  the  powder  remains  evenly  spread 
upon  its  surface ;  it  is  once  more  dried,  and,  lastly,  fired  at  an  exceedingly 
high  temperature. 

The  porcelain-furnace  is  a  circular  structure  of  masonry,  having  several 
fireplaces,  and  surmounted  by  a  lofty  dome.  Dry  wood  or  coal  is  con- 
sumed as  fuel,  and  its  flame  directed  into  the  interior,  and  made  to  circu- 
late around  and  among  the  earthen  cases,  or  scggars,  in  which  the  articles 
to  be  fired  are  packed.  Many  hours  are  required  for  this  operation,  which 
must  be  very  carefully  managed.  After  the  lapse  of  several  days,  when 
the  furnace  has  completely  cooled,  the  contents  are  removed  in  a  finished 
state,  so  far  as  regards  the  ware. 

The  ornamental  part,  consisting  of  gilding  and  painting  in  enamel,  has 
yet  to  be  executed ;  after  which  the  pieces  are  again  heated,  in  order  to  flux 
the  colors.  The  operation  has  sometimes  to  be  repeated  more  than  once. 

*  See  Richardson  and  Watts's  Chemical  Technology,  vol.  i.  part  iv.  pp.  69-104. 


MAGNESIUM.  347 

The  manufacture  of  porcelain  in  Em-ope  is  of  modern  origin  :  the  Chi- 
nese have  possessed  the  art  from  the  commencement  of  the  seventh  century, 
and  their  ware  is,  in  some  respects,  altogether  unequalled.  The  materials 
employed  by  them  are  known  to  be  kaolin,  or  decomposed  felspar  ;  petuntze, 
or  quai'tz  reduced  to  fine  powder ;  and  the  ashes  of  fern,  which  contain 
po'tassium  carbonate. 

Stoneware.  —  This  is  a  coarse  kind  of  porcelain,  made  from  clay  contain- 
ing oxide  of  iron  and  a  little  lime,  to  which  it  owes  its  partial  fusibility. 
The  glazing  is  performed  by  throwing  common  salt  into  the  heated  furnace: 
this  is  volatilized,  and  decomposed  by  the  joint  agency  of  the  silica  of  the 
ware  and  of  the  vapor  of  water  always  present ;  hydrochloric  acid  and  soda 
are  produced,  the  latter  forming  a  silicate,  which  fuses  over  the  surface  of 
the  ware,  and  gives  a  thin,  but  excellent  glaze. 

Earthenware.  —  The  finest  kind  of  earthenware  is  made  from  a  white  sec- 
ondary clay,  mixed  with  a  considerable  quantity  of  silica.  The  articles  are 
thoroughly  dried  and  fired ;  after  which  they  are  dipped  into  a  readily 
fusible  glaze  mixture,  of  which  lead  oxide  is  usually  an  important  ingre- 
dient, and,  when  dry,  re-heated  to  the  point  of  fusion  of  the  latter.  The 
whole  process  is  much  easier  of  execution  than  the  making  of  porcelain, 
and  demands  less  care.  The  ornamental  designs  in  blue  and  other  colors, 
so  common  upon  plates  and  household  articles,  are  printed  upon  paper  in 
enamel  pigment  mixed  with  oil,  and  transferred,  while  still  wet,  to  the 
unglazed  Avare.  When  the  ink  becomes  dry,  the  paper  is  washed  off,  and 
the  glazing  completed. 

The  coarser  kinds  of  earthenware  are  sometimes  covered  with  a  whitish 
opaque  glaze,  which  contains  the  oxides  of  lead  and  tin  ;  such  glaze  is  very 
liable  to  be  attacked  by  acids,  and  is  dangerous  for  culinary  vessels. 

Crucibles,  when  of  good  quality,  are  very  valuable  to  the  practical 
chemist.  They  are  made  of  clay  free  from  lime,  mixed  with  sand  or 
ground  ware  of  the  same  description.  The  Hessian  and  Cornish  crucibles 
are  among  the  best.  Sometimes  a  mixture  of  plumbago  and  clay  is  em- 
ployed for  the  same  purpose ;  and  powdered  coke  has  been  also  used  with 
the  earth :  such  crucibles  bear  rapid  changes  of  temperature  with  impunity. 


GROUP  III. 

MAGNESIUM. 
Atomic  weight,  24.     Symbol,  Mg. 

This  metal  was  formerly  classed  with  the  metals  of  the  alkaline  earths, 
but  it  is  much  more  nearly  related  to  zinc  by  its  properties  in  the  free 
state,  as  well  as  by  the  volatility  of  its  chloride,  the  solubility  of  its  sul- 
phate, and  the  isomorphism  of  several  of  its  compounds  with  the  analo- 
gously constituted  compounds  of  zinc. 

Magnesium  occurs  in  the  mineral  kingdom  as  hydrate,  carbonate,  borate, 
phosphate,  sulphate,  and  nitrate,  sometimes  in  the  solid  state,  sometimes 
dissolved  in  mineral  waters  :  magnesian  limestone,  or  dolomite,  which  forms 
entire  mountain  masses,  is  a  carbonate  of  magnesium  and  calcium.  Magne- 
sium also  occurs  as  silicate,  combined  with  other  silicates,  in  a  variety  of 
minerals,  as  steatite,  hornblende,  augite,  talc,  &c.  :  also  as  aluminate  in 
spinelle  and  zeilanite.  It  likewise  occurs  in  the  bodies  of  plants  and  ani- 
mals, chiefly  as  carbonate  and  phosphate,  and  in  combination  with  organic 
acids. 

Metallic  magnesium  is  prepared: 

1.  By  the  electrolysis  of  fused  magnesium  chloride,  or,  better,  of  a  mix- 


348  DYAD    METALS. 

ture  of  4  molecules  of  magnesium  chloride  and  3  molecules  of  potassium 
chloride  with  a  small  quantity  of  sal-ammoniac.  A  convenient  way  of 
effecting  the  reduction  is  to  fuse  the  mixture  in  a  common  clay  tobacco-pipe 
over  an  Argand  spirit-lamp  or  gas-burner,  the  negative  pole'being  an  iron 
wire  passed  up  the  pipe-stem,  and  the  positive  pole  a  piece  of  gas-coke, 
just  touching  the  surface  of  the  fused  chlorides.  On  passing  the  current 
of  a  battery  of  ten  Bunsen's  cells  through  the  arrangement,  the  magnesium 
collects  round  the  extremity  of  the  iron  wire  (Matthiessen). 

2.  Magnesium  may  be  prepared  in  much  larger  quantity  by  reducing 
magnesium  chloride,  or  the  double  chloride  of  magnesium  and  sodium  or 
potassium,  with  metallic  sodium.  The  double  chloride  is  prepared  by  dis- 
solving magnesium  carbonate  in  hydrochloric  acid,  adding  an  equivalent 
quantity  of  sodium  or  potassium  chloride,  evaporating  to  dryness,  and 
fusing  the  residue.  This  product,  heated  with  sodium  in  a  wrought-iron 
crucible,  yields  metallic  .magnesium,  containing  certain  impurities,  from 
which  it  may  be  freed  by  distillation.  This  process  is  now  carried  out  on 
the  manufacturing  scale,  and  the  magnesium  is  drawn  out  into  wire  or 
formed  into  riband  for  burning.* 

Magnesium  is  a  brilliant  metal,  almost  as  white  as  silver,  somewhat  more 
brittle  at  common  temperatures,  but  malleable  at  a  heat  a  little  below  red- 
ness. Its  specific  gravity  is  1-74.  It  melts  at  a  red  heat,  and  volatilizes  at 
nearly  the  same  temperature  as  zinc.  It  retains  its  lustre  in  dry  air,  but  in 
moist  air  it  becomes  covered  with  a  crust  of  magnesia. 

Magnesium  in  the  form  of  wire  or  riband  takes  fire  at  a  red  heat,  burning 
with  a  dazzling  bluish-white  light.  The  flame  of  a  candle  or  spirit-lamp 
is  sufficient  to  inflame  it,  but  to  insure  continuous  combustion  the  metal 
must  be  kept  in  contact  with  the  flame.  For  this  purpose  lamps  are  con- 
structed, provided  with  a  mechanism  which  continually  pushes  three  or 
more  magnesium  wires  into  a  small  spirit-flame. 

The  magnesium  flame  produces  a  continuous  spectrum,  containing  a  very 
large  proportion  of  the  more  refrangible  rays:  hence  it  is  well  adapted  for 
photography,  and  has,  indeed,  been  used  for  taking  photographs,  in  the 
absence  of  the  sun,  or  in  places  where  sunlight  cannot  penetrate,  as  in 
caves  or  subterranean  apartments. 

MAGNESIUM  CHLORIDE,  MgCl2. — When  magnesia,  or  its  carbonate,  is 
dissolved  in  hydrochloric  acid,  magnesium  chloride  and  water  are  produced ; 
but  when  this  solution  is  evaporated  to  dryness,  the  last  portions  of  water 
are  retained  with  such  obstinacy,  that  decomposition  of  the  water  is  brought 
about  by  the  concurring  attractions  of  magnesium  for  oxygen,  and  of  chlor- 
ine for  hydrogen;  hydrochloric  acid  is  expelled,  and  magnesia  remains. 
If,  however,  sal-ammoniac,  potassium  chloride,  or  sodium  chloride  is  present, 
a  double  salt  is  produced,  which  is  easily  rendered  anhydrous.  The  best 
mode  of  preparing  the  chloride  is  to  divide  a  quantity  of  hydrochloric  acid 
into  two  equal  portions,  to  neutralize  one  with  magnesia,  and  the  other 
with  ammonia,  or  carbonate  of  ammonia:  to  mix  these  solutions,  evaporate 
them  to  dryness,  and  then  expose  the  salt  to  a  red  heat  in  a  loosely  covered 
porcelain  crucible.  Sal-ammoniac  sublimes,  and  magnesium  chloride  in  a 
fused  state  remains;  the  latter  is  poured  out  upon  a  clean  stone,  and  when 
cold  transferred  to  a  well  stopped  bottle. 

The  chloride  so  obtained  is  white  and  crystalline.  It  is  very  deliquescent 
and  highly  soluble  in  water,  from  which  it  cannot  again  be  recovered  by 
evaporation,  for  the  reasons  just  mentioned.  When  long  exposed  to  the 
air  in  a  melted  state,  it  is  converted  into  magnesia.  It  is  soluble  in 
alcohol. 

*  For  details  of  the  manufacturing  process,  see  Richardson  and  Watts' s  Chemical  Technology, 
vol.  i.  pt.  v.  pp.  336-339. 


MAGNESIUM.  349 

MAGNESIUM  OXIDE,  or  MAGNESIA,  MgO.  —  This  oxide  is  easily  prepared 
by  exposing  the  magnesia  alba  of  pharmacy,  which  is  a  hydro-carbonate,  to 
a  full  red  heat  in  an  earthen  or  platinum  crucible.  It  forms  a  soft,  white 
powder,  which  slowly  attracts  moisture  and  carbonic  acid  from  the  air,  and 
unites  quietly  with  water  to  a  hydrate  which  possesses  a  feeble  degree  of 
solubility,  requiring  about  5000  parts  of  water  at  15.5°  and  36,000  parts  at 
100°.  The  alkalinity  of  magnesia  can  only  be  observed  by  placing  a  small 
portion  in  a  moistened  state  upon  test-paper;  it  neutralizes  acids,  however, 
in  the  most  complete  manner.  It  is  infusible. 

Magnesium  sulphide  is  formed  by  passing  vapor  of  carbon  sulphide  over 
magnesia,  in  capsules  of  coke,  at  a  strong  red  heat. 

MAGNESIUM  SULPHATE;  EPSOM  SALT;  S04Mg.70H2. — This  salt  occurs 
in  sea-water,  and  in  that  of  many  mineral  springs,  and  is  now  manufac- 
tured in  large  quantities  by  acting  on  magnesian  limestone  with  dilute  sul- 
phuric acid,  and  separating  the  magnesium  sulphate  from  the  greater  part 
of  the  slightly  soluble  calcium  sulphate  by  filtration.  The  crystals  are  de- 
rived from  a  right  rhombic  prism ;  they  are  soluble  in  an  equal  weight  of 
water  at  15-5°,  and  in  a  still  smaller  quantity  at  100°.  The  salt  has  a 
nauseous  bitter  taste,  and,  like  many  other  neutral  salts,  possesses  pur- 
gative properties.  When  it  is  exposed  to  heat,  6  molecules  of  water 
readily  pass  off,  the  seventh  being  energetically  retained.  Magnesium  sul- 
phate forms  beautiful  double  salts  with  the  sulphates  of  potassium  and 
ammonium,  which  contain  6  molecules  of  crystallization-water,  their  for- 
mula) being  (S04)2Mg"K2 .  60  H2,  and  (S04)2Mg"(NH4)a.  60H2.  These  salts 
are  isomorphous,  and  form  monoclinic  crystals. 

MAGNESIUM  CARBONATE.  —  The  neutral  carbonate,  C03Mg  or  C02.MgO,  oc- 
curs native  in  rhombohedral  crystals,  resembling  those  of  calc-spar,  im- 
bedded in  talc  slate :  a  soft  earthy  variety  is  sometimes  met  with. 

When  magnesia  alba  is  dissolved  in  aqueous  carbonic  acid,  and  the  solu- 
tion left  to  evaporate  spontaneously,  small  prismatic  crystals  are  deposited, 
consisting  of  trihydrated  magnesium  carbonate,  C05Mg.  30H2. 

The  magnesia  alba  itself,  although  often  called  carbonate  of  magnesium, 
is  not  so  iu  reality  ;  it  is  a  compound  of  carbonate  with  hydrate.  It  is 
prepared  by  mixing  hot  solutions  of  potassium  or  sodium  carbonate  and 
magnesium  sulphate,  the  latter  being  kept  in  slight  excess,  boiling  the 
whole  a  few  minutes,  during  which  time  much  carbonic  acid  is  disengaged, 
and  well  washing  the  precipitate  so  produced.  If  the  solution  be  very 
dilute,  the  magnesia  alba  is  exceedingly  light  and  bulky ;  if  otherwise,  it  is 
denser.  The  composition  of  this  precipitate  is  not  perfectly  constant.  In 
most  cases  it  contains  4C03Mg.MgH202.  60H2. 

Magnesia  alba  is  slightly  soluble  in  water,  especially  when  cold. 

MAGNESIUM  PHOSPHATE,  P04Mg/xH  .  70H2.  — This  salt  separates  in  small 
colorless  prismatic  crystals  when  solutions  of  sodium  phosphate  and  mag- 
nesium sulphate  are  mixed  and  suffered  to  stand  for  some  time.  According 
to  Graham,  it  is  soluble  in  about  1000  parts  of  cold  water.  Magnesium 
phosphate  exists  in  the  grain  of  the  cereals,  and  can  be  detected  in  con- 
siderable quantity  in  beer. 

MAGNESIUM  AND  AMMONIUM  PHOSPHATE,  P04Mg/x(NH4) .  60H2. — When 
ammonia  or  its  carbonate  is  mixed  with  a  magnesium  salt,  and  a  soluble 
phosphate  is  added,  a  crystalline  precipitate  having  the  above  composition, 
subsides,  immediately  if  the  solutions  are  concentrated,  and  after  some 
time  if  very  dilute  :  in  the  latter  case,  the  precipitation  is  promoted  by 
stirring.  This  salt  is  slightly  soluble  in  pure  water,  but  nearly  insoluble 

30 


350  DYAD    METALS. 

in  saline  and  ammoniacal  liquids.  When  heated,  it  gives  off  water  and 
ammonia,  and  is  converted  into  magnesium  pyrophosphate,  P207Mg2: 

2P04Mg(NH4)  =  P207MS2  +  OH2     +     2XH3. 

At  a  strong  red-heat  it  fuses  to  a  white  enamel-like  mass.  Magnesium  and 
ammonium  phosphate  sometimes  form  a  urinary  calculus,  and  occur  also 
in  guano. 

In  practical  analysis,  magnesium  is  often  separated  from  solutions  by 
bringing  it  into  this  state.  The  liquid,  free  from  alumina,  lime,  &c.,  is 
mixed  with  sodium  phosphate  and  excess  of  ammonia,  and  gently  heated 
for  a  short  time.  The  precipitate  is  collected  upon  a  filter  and  thoroughly 
washed  with  water  containing  a  little  ammonia,  after  which  it  is  dried,  ig- 
nited to  redness,  and  weighed.  The  proportion  of  magnesia  is  then  easily 
calculated. 


SILICATES.  —  The  following  natural  compounds  belong  to  this 
lUe,  Si04Mg2  =  Si02.2MgO,  a  crystallized  mineral,  sometimes 


MAGNESIUM 

class :    Chrysoli 

employed  for  ornamental  purposes:  a  portion  of  the  magnesia  iscommonlv 
replaced  by  ferrous  oxide,  which  communicates  a  green  color.  Meerschaum. 
liSiO3Mg.SiOa  =  3Si02.2MgO,  a  soft,  sectile  mineral,  from  which  pipe-bowls 
are  made.  Talc.  4Si03Mg.Si()2.  |  aq.  (called  steatite  when  massive),  is  a  toft, 
white  sectile,  transparent  or  translucent  mineral,  used  as  fire-stones  for 
furnaces  and  stoves,  and  in  thin  plates  for  glazing  lanterns,  &c. ;  also  in 
the  state  of  powder  for  diminishing  friction.  Soapstone,  also  called  steatite, 
is  a  silicate  of  magnesium  and  aluminium  of  somewhat  variable  composition. 
Serpentine  is  a  combination  of  silicate  and  hydrate  of  magnesium.  Jade,  an 
exceedingly  hard  stone,  brought  from  New  Zealand,  is  a  silicate  of  magne- 
sium and  aluminium:  its  green  color  is  due  to  chromium.  Augite  and  horn- 
blende are  essentially  double  salts  of  silicic  acid,  magnesia,  and  lime,  in 
which  the  magnesia  is  more  or  less  replaced  by  its  isomorphous  substitute, 
ferrous  oxide. 


Magnesium  salts  are  isomorphous  with  zinc  salts,  ferrous  salts,  cupric 
salts,  cobalt  salts,  and  nickel  salts,  &c. ;  they  are  usually  colorless,  and  are 
easily  recognized  by  the  following  characters: — A  gelatinous  white  preci- 
pitate with  caustic  alkalies,  including  ammonia,  insoluble  in  excess,  but 
soluble  in  solution  of  sal-ammoniac.  A  white  precipitate  with  potassium 
and  sodium  carbonates,  but  none  with  ammonium  carbonate  in  the  cold.  A 
white  crystalline  precipitate  with  soluble  phosphates,  on  the  addition  of  a 
little  ammonia. 


ZINC. 

Atomic  weight,  65.     Symbol,  Zn. 

Zinc  is  a  somewhat  abundant  metal:  it  is  found  in  the  state  of  carbonate, 
silicate,  and  sulphide,  associated  with  lead  ores  in  many  districts,  both  in 
Britain  and  on  the  Continent;  large  supplies  are  obtained  from  Silesia,  and 
from  the  neighborhood  of  Aachen.  The  native  carbonate,  or  calamine,  is 
the  most  valuable  of  the  zinc  ores,  and  is  preferred  for  the  extraction  of 
the  metal:  it  is  first  roasted  to  expel  water  and  carbonic  acid,  then  mixed 
with  fragments  of  coke  or  charcoal,  and  distilled  at  a  full  red  heat  in  a 
large  earthen  retort;  carbon  monoxide  escapes,  while  the  reduced  metal 
volatilizes  and  is  condensed  by  suitable  means,  generally  with  minute  quan- 
tities of  arsenic. 


ZINC.  351 

Zinc  is  a  bluish-white  metal,  which  slowly  tarnishes  in  the  air;  it  has  a 
lamellar,  crystalline  structure,  a  density  varying  from  6-8  to  7-2,  and  is, 
under  ordinary  circumstances,  brittle.  Between  120°  and  150°  C.  (248° — 
300°  F.)  it  is,  on  the  contrary,  malleable,  arid  may  be  rolled  or  hammered 
without  danger  of  fracture ;  and,  what  is  very  remarkable,  after  such 
treatment,  it  retains  its  malleability  when  cold;  the  sheet-zinc  of  commerce 
is  thus  made.  At  210°  C.  (410°  F.)  it  is  so  brittle  that  it  may  be  reduced 
to  powder.  At  412°  C.  (773°  F.)  it  melts:  at  a  bright  red  heat  it  boils 
and  volatilizes,  and,  if  air  be  admitted,  burns  with  a  splendid  greenish 
light,  generating  the  oxide.  Dilute  acids  dissolve  zinc  very  readily :  it  is 
constantly  employed  in  this  manner  for  preparing  hydrogen  gas. 

Zinc  is  a  dyad  metal,  forming* only  one  class  of  compounds. 

ZINC  CHLORIDE,  ZnCl2,  may  be  prepared  by  heating  metallic  zinc  in 
chlorine:  by  distilling  a  mixture  of  zinc  filings  and  corrosive  sublimate; 
or,  more  easily,  by  dissolving  zinc  in  hydrochloric  acid.  It  is  a  nearly 
white,  translucent,  fusible  substance,  very  soluble  in  water  and  alcohol, 
and  very  deliquescent.  A  strong  solution  of  zinc  chloride  is  sometimes 
used  as  a  bath  for  obtaining  a  graduated  heat  above  100°.  Zinc  chloride 
unites  with  sal-ammoniac  and  potassium  chloride  to  double  salts:  the 
former  of  these,  made  by  dissolving  zinc  in  hydrochloric  acid,  and  then 
adding  an  equivalent  quantity  of  sal-ammoniac,  is  very  useful  in  tinning 
and  soft-soldering  copper  and  iron. 

ZINC  OXIDE,  ZnO,  is  a  strong  base,  forming  salts  isomorphous  with  the 
magnesium  salts.  It  is  prepared  either  by  burning  zinc  in  atmospheric 
air,  or  by  heating  the  carbonate  to  redness.  Zinc  oxide  is  a  white,  taste- 
less powder,  insoluble  in  water,  but  freely  dissolved  by  acids.  When  heated 
it  is  yellow,  but  turns  white  again  on  cooling.  It  is  getting  into  use  as  a 
substitute  for  white  lead.  To  prepare  zinc-white  on  a  large  scale,  metallic 
zinc  is  volatilized  in  large  earthen  muffles,  whence  the  zinc  vapor  passes 
into  a  small  receiver  (guerite},  where  it  comes  in  contact  with  a  current  of 
air  and  is  oxidized.  The  zinc  oxide  thus  formed  passes  immediately  into 
a  condensing  chamber  divided  into  several  compartments  by  cloths  sus- 
pended within  it. 

ZINC  SULPHATE,  S04Zn.70H2,  commonly  called  white  vitriol. — This  salt 
is  hardly  to  be  distinguished  by  the  eye  from  magnesium  sulphate:  it  is 
prepared  either  by  dissolving  the  metal  in  dilute  sulphuric  acid,  or,  more 
economically,  by  roasting  the  native  sulphide,  or  blende,  which,  by  absorp- 
tion of  oxygen,  becomes  in  great  part  converted  into  sulphate.  The  altered 
mineral  is  thrown  hot  into  water,  and  the  salt  obtained  by  evaporating  the 
clear  solution.  Zinc  sulphate  has  an  astringent  metallic  taste,  and  is  used 
in  medicine  as  an  emetic.  The  crystals  dissolve  in  2£  parts  of  cold,  and  in 
a  much  smaller  quantity  of  hot  water.  Crystals  containing  6  molecules  of 
water  have  been  observed.  Zinc  sulphate  forms  double  salts  with  the  sul- 
phates of  potassium  and  ammonium,  namely,  (S04)2ZnK2.  60H2,  and  (S04)2 
Zn(NH4)2.  OOH2,  isomorphous  with  the  corresponding  magnesiujn  salts. 

ZINC  CARBONATE,  C03Zn,  is  found  native;  the  white  precipitate  obtained 
by  mixing  solutions  of  zinc  and  of  alkaline  carbonates,  is  a  combination  of 
carbonate  and  hydrate.  When  heated  to  redness,  it  yields  pure  zinc  oxide. 

ZINC  SULPHIDE,  ZnS,  occurs  native  as  blende,  in  regular  tetrahedrons, 
dodecahedrons,  and  other  monometric  forms,  and  of  various  colors,  from 
white  or  yellow  to  brown  or  black,  according  to  its  degree  of  purity :  it  is 
a  valuable  ore  of  zinc.  A  variety  called  black  jack  occurs  somewhat  abun- 
dantly in  Derbyshire,  Cumberland,  and  Cornwall.  A  hydrated  sulphide,  ZnS. 


352  DYAD    METALS. 

OH2,  is  obtained  as  a  white  precipitate  on  adding  an  alkaline  sulphide  to 
the  solution  of  a  zinc  salt. 


Zinc  salts  are  distinguished  by  the  following  characters:  —  Caustic  potash 
and  soda  give  a  white  precipitate  of  hydrate,  freely  soluble  in  excess  of 
alkali.  Ammonia  behaves  in  the  same  manner ;  an  excess  redissolves  the 
precipitate  instantly.  Potassium  and  sodium  carbonates  give  white  precipi- 
tates, insoluble  in  excess.  Ammonium  carbonate  gives  also  a  white  precipi- 
tate, which  is  redissolved  by  an  excess.  Potassium  f  err  ocyanide  gives  a  white 
precipitate.  Hydrogen  sulphide  causes  no  change  in  zinc  solutions  containing 
free  mineral  acids:  but  in  neutral  solutions,  or  with  zinc  salts  of  organic 
acids,  such  as  the  acetate,  a  white  precipitate  is  formed.  Ammonium  sul- 
phide throws  down  white  sulphide  of  zinc,  insoluble  in  caustic  alkalies. 
The  formation  of  this  precipitate  in  a  solution  containing  excess  of  caustic 
alkali,  serves  to  distinguish  zinc  from  all  other  metals. 

All  zinc  compounds,  heated  on  charcoal  with  sodium  carbonate  in  the 
inner  blowpipe  flame,  give  an  incrustation  of  zinc  oxide,  which  is  yellow 
while  hot,  but  becomes  white  in  cooling.  If  this  incrustation  be  moistened 
with  a  dilute  solution  of  cobalt  nitrate,  and  strongly  heated  in  the  outer 
flame,  a  fine  green  color  is  produced. 


The  applications  of  metallic  zinc  to  the  purposes  of  roofing,  the  con- 
struction of  water-channels,  &c.,  are  well  known;  it  is  sufficiently  durable, 
but  inferior  in  this  respect  to  copper.  It  is  much  used  also  for  protecting 
iron  and  copper  from  oxidation  when  immersed  in  saline  solutions,  such  as 
sea-water,  or  exposed  to  damp  air.  This  it  does  by  forming  an  electric 
circuit,  in  which  it  acts  as  the  positive  or  more  oxidable  metal  (p.  249). 
Galvanized  iron  consists  of  iron  having  its  surface  coated  with  zinc. 


CADMIUM. 

Atomic  weight,  112.     Symbol,  Cd. 

This  metal  was  discovered  in  1817  by  Stromeyer,  and  by  Hermann :  it 
accompanies  the  ores  of  zinc,  especially  those  occurring  in  Silesia,  and, 
being  more  volatile  than  that  substance,  rises  first  in  vapor  when  the  cala- 
mine  is  subjected  to  distillation  with  charcoal.  Cadmium  resembles  tin  in 
color,  but  is  somewhat  harder :  it  is  very  malleable,  has  a  density  of  8-7, 
melts  below  260°  C.  (500°  F.),  and  is  nearly  as  volatile  as  mercury.  It 
tarnishes  but  little  in  the  air,  but,  when  strongly  heated,  burns.  Dilute 
sulphuric  and  hydrochloric  acids  act  but  little  on  this  metal  in  the  cold  ; 
nitric  acid  is  its  best  solvent. 

The  observed  vapor-density  of  cadmium  is  3-94  compared  with  air  as 
unity,  or  56-3  compared  with  hydrogen,  which  latter  number  does  not  differ 
greatly  from  the  half  of  112,  the  atomic  weight  of  the  metal:  hence  it  ap- 
pears that  the  atom  of  cadmium  in  the  state  of  vapor  occupies  twice  the 
space  of  an  atom  of  hydrogen  (see  p.  229). 

Cadmium,  like  zinc,  is  dyadic,  and  forms  but  one  series  of  compounds. 

CADMIUM  OXIDE,  CdO. — This  oxide  may  be  prepared  by  igniting  either 
the  carbonate  or  the  nitrate :  in  the  former  case  it  has  a  pale-brown  color, 
and  in  the  latter  a  much  darker  tint,  and  forms  octohedral  microscopic 
crystals.  Cadmium  oxide  is  infusible :  it  dissolves  in  acids,  producing  a 


COPPER.  353 

series  of  colorless  salts :   it  attracts  carbonic  acid  from  the  air,  and  turns 
white. 

CADMIUM  SULPHATE,  S04Cd .  40H2,  is  easily  obtained  by  dissolving  the 
oxide  or  carbonate  in  dilute  sulphuric  acid:  it  is  very  soluble  in  water,  and 
forms  double  salts  with  the  sulphates  of  potassium  and  ammonium,  which 
contain  respectively  (S04)2CdK2.  60H2  and  (S04)2Cd(NH4) .  60H2. 

CADMIUM  CHLORIDE,  CdCl2,  is  a  very  soluble  salt,  crystallizing  in  small 
four-sided  prisms. 

CADMIUM  SULPHIDE  is  a  very  characteristic  compound,  of  a  bright-yellow 
color,  forming  microscopic  crystals,  fusible  at  a  high  temperature.  It  is 
obtained  by  passing  sulphuretted  hydrogen  gas  through  a  solution  of  the 
sulphate,  nitrate,  or  chloride.  This  compound  is  used  as  a  yellow  coloring 
matter,  of  great  beauty  and  permanence.  It  occurs  native  as  greenockite. 

The  salts  of  cadmium  are  thus  distinguished :  —  Fixed  caustic  alkalies 
give  a  white  precipitate  of  hydrated  oxide,  insoluble  in  excess.  Am- 
monia gives  a  similar  white  precipitate,  readily  soluble  in  excess.  The 
fixed  alkaline  carbonates,  and  ammonia  carbonate,  throw  down  white  cadmium 
carbonate,  insoluble  in  excess  of  either  precipitant.  Hydrogen  sulphide  and 
ammonium  sulphide  precipitate  the  yellow  sulphide  of  cadmium. 


GROUP  IV. 

COPPEE. 

Atomic  weight,  63-5.     Symbol,  Cu  (Cuprum). 

Copper  is  a  metal  of  great  value  in  the  arts;  it  sometimes  occurs  in  the 
metallic  state,  crystallized  in  octohedrons,  or  more  frequently  in  dodeca- 
hedrons, but  is  more  abundant  in  the  form  of  red  oxide,  and  in  that  of 
sulphide  combined  with  sulphide  of  iron,  as  yelloiv  copper  ore,  or  copper 
jn/rilfs.  Large  quantities  of  the  latter  substance  are  annually  obtained 
from  the  Cornish  mines,  and  taken  to  South  Wales  for  reduction,  which  is 
effected  by  a  somewhat  complex  process.  The  principle  of  this  may,  how- 
ever, be  easily  made  intelligible.  The  ore  is  roasted  in  a  reverberatory 
furnace,  by  which  much  of  the  iron  sulphide  is  converted  into  oxide,  while 
the  copper  sulphide  remains  unaltered.  The  product  of  this  operation  is 
then  strongly  heated  with  siliceous  sand;  the  latter  combines  with  the  iron 
oxide  to  a  fusible  slag,  and  separates  from  the  heavier  copper-compound. 
When  the  iron  has,  by  a  repetition  of  these  processes,  been  got  rid  of, 
the  copper  sulphide  begins  to  decompose  in  the  flame-furnace,  losing  its 
sulphur  and  absorbing  oxygen:  the  temperature  is  then  raised  sufficiently 
to  reduce  the  oxide  thus  produced,  by  the  aid  of  carbonaceous  matter. 
The  last  part  of  the  operation  consists  in  thrusting  into  the  melted  metal 
a  pole  of  birch-wood,  the  object  of  which  is  probably  to  reduce  a  little  re- 
maining oxide  by  the  combustible  gases  thus  generated.  Large  quantities 
of  extremely  valuable  ore,  chiefly  carbonate  and  red  oxide,  have  lately  been 
obtained  from  South  Australia  and  Chile. 

Copper  has  a  well-known  yellowish-red  color,  a  specific  gravity  of  8-96, 
and  is  very  malleable  and  ductile :  it  is  an  excellent  conductor  of  heat  and 
electricity  ;  it  melts  at  a  bright  rod  heat,  and  seems  to  be  slightly  volatile 
at  a  very  high  temperature  Copper  undergoes  no  change  in  dry  air;  ex- 
!•>  a,  moist  jitmosphi-re,  it  becomes  covered  with  a  strongly  adherent 
30* 


354  DYAD    METALS. 

green  crust,  consisting  in  a  great  measure  of  carbonate.  Heated  to  redness 
in  the  air,  it  is  quickly  oxidized,  becoming  covered  with  a  black  scale 
Dilute  sulphuric  and  hydrochloric  acids  scarcely  act  upon  copper;  boiling 
oil  of  vitriol  attacks  it,  with  evolution  of  sulphurous  oxide  ;  nitric  acid, 
even  dilute,  dissolves  it  readily,  with  evolution  of  nitrogen  dioxide. 

Copper  is  a  dyad  metal,  its  most  stable  compounds,  the  cupric  compounds, 
containing  1  atom  of  the  metal  combined  with  2  atoms  of  a  univalent, 
or  1  atom  of  a  bivalent  negative  radical,  e.g.,  Cu//Cl2,  Cu7/0,  Cu//(N03).2, 
Cu/xS04,  &c.  Some  of  these,  however,  are  capable  of  taking  up  another 
atom  of  copper,  and  forming  compounds,  called  cuprous  compounds,  in  which 

CuCl 
the  copper  is  apparently  univalent  ;    thus  cuprous  chloride,  Cu2Cl2  =  |        ; 

Cu^  CuCl 

cuprous  oxide,  Cu20  =  |      J^>^-    These  compounds  are  very  unstable,  be- 


ing  easily  converted  into  cupric  compounds  by  the  action  of  oxidizing  agents. 

COPPER  CHLORIDES.  —  Cupric  chloride,  CuCl2,  is  most  easily  prepared  by 
dissolving  cupric  oxide  in  hydrochloric  acid,  and  concentrating  the  green 
solution  thence  resulting.  It  forms  green  crystals,  CuCl2  .  20H2,  very 
soluble  in  water  and  in  alcohol:  it  colors  the  flame  of  the  latter  green. 
When  gently  heated,  it  parts  with  its  water  of  crystallization  and  becomes 
yellowish-brown  ;  at  a  high  temperature  it  loses  half  its  chlorine  and  be- 
comes converted  into  cuprous  chloride.  The  latter  is  a  white  fusible  sub- 
stance, but  little  soluble  in  water,  and  prone  to  oxidation  :  it  is  formed 
when  copper-filings  or  copper-leaf  are  put  into  chlorine  gas  ;  also  by  pre- 
cipitating a  solution  of  cupric  chloride  or  other  cupric  salt  with  stannous 
chloride  : 

2CuCl2         -f         SnCl2        =        Cu2Cl2         +         SnC|4 
Cupric  Stannous  Cuprous  Stannic 

chloride.  chloride.  chloride.  chloride. 

A  plate  of  copper  immersed  in  hydrochloric  acid  in  a  vessel  containing  air, 
becomes  covered  with  white  tetrahedrons  of  cuprous  chloride.  This  com- 
pound dissolves  in  hydrochloric  acid,  forming  a  colorless  solution,  which 
gradually  turns  blue  on  exposure  to  the  air. 

A  hydrated  cupric  oxychloride,  CuCl2  .  3CuH202,  occurs  native  as  atacamite. 

Both  the  chlorides  of  copper  form  double  salts  with  the  chlorides  of  the 
alkali-metals. 

CUPROUS  HYDRIDE,  Cu2EI2.  —  When  a  solution  of  cupric  sulphate  is  heated 
to  about  70°,  with  hypophosphorous  acid,  this  compound  is  deposited  as  a 
yellow  precipitate  which  soon  turns  red-brown.  It  gives  off  hydrogen  when 
heated,  takes  fire  in  chlorine  gas,  and  is  converted  by  hydrochloric  acid  into 
cuprous  chloride,  with  evolution  of  a  double  quantity  of  hydrogen,  the  acid 
giving  up  its  hydrogen  as  well  as  the  copper  hydride  : 

Cu2H2     -f     2HC1    =     Cu2Cl2    -f     2H2. 

This  reaction  affords  a  remarkable  instance  of  the  union  of  two  atoms  of 
the  same  element  to  form  a  molecule  (see  page  232). 

COPPER  OXIDES.  —  Two  oxides  of  copper  are  known,  corresponding  to  the 
chlorides  ;  and  a  very  unstable  dioxide  or  peroxide,  Cu02,  is  said  to  be 
formed,  as  a  yellowish-brown  powder,  by  the  action  of  hydrogen  dioxide 
on  cupric  hydrate. 

Copper  Monoxide,  Cupric  oxide,  or  Black  oxide  of  copper,  CuO,  is  prepared 
by  calcining  metallic  copper  at  a  red-heat,  with  full  exposure  to  air,  or 
more  conveniently,  by  heating  the  nitrate  to  redness,  which  suffers  com- 


COPPER.  355 

plcte  decomposition.  Cupric  salts  mixed  with  caustic  alkali  in  excess,  yield 
a  bulky  pale-blue  precipitate  of  hydrated  cupric  oxide,  or  cupric  hydrate, 
CtlHjO,  or  CuO.OH2,  which,  when  the  whole  is  raised  to  the  boiling-point, 
becomes  converted  into  a  heavy  dark-brown  powder:  this  also  is  anhydrous 
oxide  of  copper,  the  hydrate  suffering  decomposition,  even  in  contact  with 
water.  The  oxide  prepared  at  a  high  temperature  is  perfectly  black  and 
very  dense.  Cupric  oxide  is  soluble  in  acids,  and  forms  a  series  of  very 
important  salts,  isomorphous  with  magnesium  salts. 

Cuprous  oxide,  Cu20,  also  called  Red  oxide  and  Suboxide  of  copper. — This 
oxide  may  be  obtained  by  heating  in  a  covered  crucible  a  mixture  of  5  parts 
of  black  oxide  and  4  parts  of  fine  copper-filings;  or  by  adding  grape-sugar 
to  a  solution  of  cupric  sulphate,  and  then  putting  in  an  excess  of  caustic 
potash  ;  the  blue  solution,  heated  to  ebullition,  is  reduced  by  the  sugar,  and 
deposits  cuprous  oxide.  This  oxide  often  occurs  in  beautiful  transparent 
ruby-red  crystals,  associated  with  other  ores  of  copper,  and  can  be  obtained 
in  the  same  state  by  artificial  means.  It  communicates  to  glass  a  magnifi- 
cent red  tint,  while  that  given  by  the  cupric  oxide  is  green. 

Cuprous  oxide  dissolves  in  excess  of  hydrochloric  acid,  forming  a  solu- 
tion of  cuprous  chloride,  from  which  that  compound  is  precipitated  on  dilu- 
tion with  water.  Most  oxygen-acids,  namely,  sulphuric,  phosphoric,  acetic, 
oxalic,  tartaric,  and  citric  acids,  decompose  cuprous  oxide,  forming  cupric 
salts,  and  separating  metallic  copper;  nitric  acid  converts  it  into  cupric 
nitrate.  Hence  there  are  but  few  cuprous  oxygen-salts,  none  indeed  except- 
ing the  sulphites  and  certain  double  sulphites  formed  by  mixing  a  cupric 
solution  with  the  sulphite  of  an  alkali-metal,  e.g.,  ammonio-cuprous  sul- 
phite, SO,Cu'(NH4). 

CUPRIC  SULPHATE,  S04Cu  .  50H2. — This  beautiful  salt,  commonly  called 
blue  vitriol,  is  prepared  by  dissolving  cupric  oxide  in  sulphuric  acid,  or, 
at  less  expense,  by  oxidizing  the  sulphide.  It  forms  large  blue  crystals, 
soluble  in  four  parts  of  cold  and  two  parts  of  boiling  water;  when  heated 
to  100°  C.  (212°  F.)  it  readily  loses  four  molecules  of  crystallization-water; 
but  the  fifth  is  retained  with  great  pertinacity,  and  is  expelled  only  at  alow 
red  heat.  At  a  very  high  temperature,  cupric  sulphate  is  entirely  converted 
into  cupric  oxide,  with  evolution  of  sulphurous  oxide  and  oxygen.  Cupric 
sulphate  combines  with  the  sulphates  of  potassium  and  of  ammonium,  form- 
ing pale-blue  salts,  (S04)2CuK2.  OOH?  and  (S04)2Cu(NH4)2.  60H2,  isomor- 
phous with  the  corresponding  magnesium  salts. 

CUPRIC  NITRATE,  (N03)2Cu.  30 H2,  is  easily  made  by  dissolving  the  metal 
in  nitric  acid ;  it  forms  deep-blue  crystals,  very  soluble  and  deliquescent. 
It  is  highly  corrosive.  An  insoluble  basic  nitrate  is  known ;  it  is  green. 

CUPRIC  CARBONATES. — When  sodium  carbonate  is  added  in  excess  to  a 
solution  of  cupric  sulphate,  the  precipitate  is  at  first  pale-blue  and  floc- 
culent,  but  by  warming  it  becomes  sandy,  and  assumes  a  green  tint;  in 
this  state  it  contains  C03Cu.CuH202-f-a,q.  This  substance  is  prepared  as  a 
pigment.  The  beautiful  mineral  malachite  has  a  similar  composition,  but 
contains  no  water  of  crystallization,  its  composition  being  CO3Cu.CuH202. 
Another  natural  compound,  called  azurite,  not  yet  artificially  imitated, 
occurs  in  large  transparent  crystals  of  the  most  intense  blue:  it  contains 
2C03Cu.CuH2O2.  Verditer,  made  by  decomposing  cupric  nitrate  with  chalk, 
is  said,  however,  to  have  a  somewhat  similar  composition. 

CUPRIC  ARSENITE  is  a  bright-green  insoluble  powder,  prepared  by  mix- 
ing the  solutions  of  a  cupric  salt  with  an  alkaline  arsenite. 

COPPER  SULPHIDES. — There  are  two  well-defined  copper  sulphides,  anal- 


356  DYAD    METALS. 

ogous  in  composition  to  the  oxides,  and  four  others,  containing  larger 
proportions  of  sulphur,  but  of  less  denned  constitution;  these  latter  are 
precipitated  from  solutions  of  cupric  salts  by  potassium  pentasulphide. 

Cupric  Sulphide,  CuS,  occurs  native  as  indiyo  copper  or  covellin,  in  soft 
bluish-black  hexagonal  plates  and  spheroidal  masses,  and  is  produced  arti- 
ficially by  precipitating  cupric  salts  with  hydrogen  sulphide. 

Cuprous  Sulphide,  Cu2S,  occurs  native  as  copper-glance  or  redruthite,  in 
lead-gray  hexagonal  prisms,  belonging  to  the  rhombic  system ;  it  is  pro- 
duced artificially  by  the  combustion  of  copper-foil  in  sulphur  vapor,  by 
igniting  cupric  oxide  with  sulphur,  and  by  other  methods.  It  is  a  power- 
ful sulphur-base,  uniting  with  the  sulphides  of  antimony,  arsenic,  and  bis- 
muth, to  form  several  natural  minerals.  The  several  varieties  of  fahl-ore, 
or  tetrahedrite,  consist  of  cuprous  sulphantimonite  or  sulpharsenite,  in 
which  the  copper  is  more  or  less  replaced  by  equivalent  quantities  of  iron, 
zinc,  silver,  and  mercury.  The  important  ore,  called  copper-pyrites,  is  a 
cuproso-ferric  sulphide,  Cu/Fe///S2,  or  Cu2S.Fe2S3,  occurring  in  tetrahedral 
crystals  of  the  quadratic  system,  or  in  irregular  masses.  Another  species 
of  copper  and  iron  sulphide,  containing  various  proportions  of  the  two 
metals,  occurs  native,  as  purple  copper  or  erubescite,  in  cubes,  octohedrons, 
and  other  monometric  forms. 

AMMONIACAL  COPPER  COMPOUNDS.  —  The  chlorides,  sulphate,  nitrate,  and 
other  salts  of  copper,  unite  with  one  or  more  molecules  of  ammonia,  form- 
ing, for  the  most  part,  crystalline  compounds  of  blue  or  green  color,  some 
of  which  may  be  regarded  as  salts  of  metallammoniums  (p.  315).  Thus, 
cupric  chloride  forms  with  ammonia,  the  compounds,  2NH3.CuCl2,  4NH3. 
CuCl2,  and  6NH3.CuCl2,  the  first  of  which  may  be  formulated  as  cupro- 
diammonium  chloride,  (N2H6Cu//)Cl2.  Cupric  sulphate  forms,  in  like  manner, 
cupro-diammonium  sulphate,  (N2H6Cu//)S04,  which  is  a  deep-blue  crystalline 
salt.  Cuprous  iodide  forms  with  ammonia  the  compound,  4NH3.Cu2l2. 


The  characters  of  the  cupric  salts  are  well  marked. 

Caustic  potash  gives  a  pale-blue  precipitate  of  cupric  hydrate,  becoming 
blackish-brown  anhydrous  oxide  on  boiling. — Ammonia  also  throws  down 
the  hydrate;  but,  when  in  excess,  redissolves  it,  yielding  an  intense  pur- 
plish-blue solution.  —  Potassium  and  sodium  carbonates  give  pale-blue  preci- 
pitates of  cupric  carbonate,  insoluble  in  excess. — Ammonium  carbonate,  the 
same,  but  soluble  with  deep-blue  color.  —  Potassium  fe.rro  cyanide  gives  a  fine 
red-brown  precipitate  of  cupric  ferrocyanide  — Hydrogen  sulphide  and 
ammonium  sulphide  afford  black  cupric  sulphide,  insoluble  in  ammonium 
sulphide. 


The  alloys  of  copper  are  of  great  importance.  Brass  consists  of  copper 
alloyed  with  from  28  to  84  per  cent,  of  zinc ;  the  latter  may  be  added 
directly  to  the  melted  copper,  or  granulated  copper  may  be  heated  with 
calamine  and  charcoal-powder,  as  in  the  old  process.  Gun-metal,  a  most 
valuable  alloy,  consists  of  90  parts  copper  and  10  tin.  Bell  and  speculum 
metal  contain  a  still  larger  proportion  of  tin ;  these  are  brittle,  especially 
the  last  named.  A  good  bronze  for  statues  is  made  of  91  parts  copper,  2 

Earts  tin,  6  parts  zinc,  and  1  part  lead.     The  brass  or  bronze  of  the  ancients 
5  an  alloy  of  copper  with  tin,  often  also  containing  lead,  and  sometimes 
zinc. 


MERCURY.  357 


MERCURY. 

Atomic  weight,  200.     Symbol,  Hg.  (Hydrargyrum). 

This  very  remarkable  metal,  sometimes  called  quicksilver,  has  been  known 
from  early  times,  and  perhaps  more  than  all  others  has  excited  the  atten- 
tion and  curiosity  of  experimenters,  by  reason  of  its  peculiar  physical 
properties.  Mercury  is  of  great  importance  in  several  of  the  arts,  and 
enters  into  the  composition  of  many  valuable  medicaments. 

Metallic  mercury  is  occasionally  met  with  in  globules  disseminated 
through  the  native  sulphide,  which  is  the  ordinary  ore.  This  latter  substance, 
sometimes  called  cinnabar,  is  found  in  considerable  quantity  in  several 
localities,  of  which  the  most  celebrated  are  Almaden  in  Spain,  and  Idria 
in  Austria.  Only  recently  it  has  been  discovered  in  great  abundance,  and 
of  remarkable  purity,  in  California  and  Australia.  The  metal  is  obtained 
by  heating  the  sulphide  in  an  iron  retort  with  lime  or  scraps  of  iron,  or  by 
roasting  it  in  a  furnace,  and  conducting  the  vapors  into  a  large  chamber, 
where  the  mercury  is  condensed,  while  the  sulphurous  acid  is  allowed  to 
escape.  Mercury  is  imported  into  this  country  in  bottles  of  hammered 
iron,  containing  seventy-five  pounds  each,  and  in  a  state  of  considerable 
purity.  When  purchased  in  smaller  quantities,  it  is  sometimes  found 
adulterated  with  tin  and  lead,  which  metals  it  dissolves  to  some  extent 
without  much  loss  of  fluidity.  Such  admixture  may  be  known  by  the  foul 
surface  the  mercury  exhibits  when  shaken  in  a  bottle  containing  air,  and 
by  the  globules,  when  made  to  roll  upon  the  table,  leaving  a  train  or  tail. 

Mercury  has  a  nearly  silver-white  color,  and  a  very  high  degree  of 
lustre :  it  is  liquid  at  all  ordinary  temperatures,  and  solidifies  only  when 
cooled  to— 40°.  In  this  state  it  is  soft  and  malleable.  At  350°  C.  (662°  F.) 
it  boils,  and  yields  a  transparent,  colorless  vapor,  of  great  density.  The 
metal  volatilizes,  however,  to  a  sensible  extent  at  all  temperatures  above 
19°  or  21°  C.  (66°  or  68°  F.) ;  below  this  point  its  volatility  is  imperceptible. 
The  volatility  of  mercury  at  the  boiling  heat  is  singularly  retarded  by  the 
presence  of  minute  quantities  of  lead  or  zinc.  The  specific  gravity  of 
mercury  at  15-5°  is  13-59;  that  of  frozen  mercury  about  14,  great  contrac- 
tion taking  place  in  the  act  of  solidification. 

Pure  mercury  is  quite  unalterable  in  the  air  at  common  temperatures, 
but  when  heated  to  near  its  boiling-point,  it  slowly  absorbs  oxygen,  and 
becomes  converted  into  a  crystalline  dark-red  powder,  which  is  the  highest 
oxide.  At  a  dull  red  heat  this  oxide  is  again  decomposed  into  its  constit- 
uents. Hydrochloric  acid  has  little  or  no  action  on  mercury,  and  the  same 
may  be  said  of  sulphuric  acid  in  a  diluted  state  :  when  the  latter  is  con- 
centrated and  boiling-hot,  it  oxidizes  the  metal,  converting  it  into  mercuric 
sulphate,  with  evolution  of  sulphurous  oxide.  Nitric  acid,  even  dilute  and 
in  the  cold,  dissolves  mercury  freely,  with  evolution  of  nitrogen  dioxide. 

The  observed  vapor-density  of  mercury  referred  to  air  as  unity  is  6-7;* 
this  referred  to  hydrogen  is  nearly  100  ;f  that  is  to  say,  half  the  atomic 
weight  of  the  metal:  consequently  the  atom  of  mercury,  like  that  of  cad- 
mium, occupies  in  the  gaseous  state  twice  the  volume  of  an  atom  of  hydro- 
gen (see  page  229). 

Mercury  forms  two  series  of  compounds ;   namely,  the  mercuric  compounds, 
which  it  is  bivalent,  as  Hg//Cl2,  Hg/rO,  Hg/xS04,  &c.,  and  the  mercurous 

*  Bineau,  Comptes  Rendus,  xlix.  799.  t  ~~0'6926       =     98'3' 


358  DYAD    METALS. 

compounds,  in  which  it  is  apparently  univalent,  as  Hg2Cl2,  Hg20,  &c.  These 
compounds  are  analogous  in  constitution  to  the  cupric  and  cuprous  com- 
pounds ;  and  the  rnercurous  compounds,  like  the  latter,  are  easily  converted 
into  mercuric  compounds  by  the  action  of  oxidizing  agents,  which  remove 
one  atom  of  mercury;  but  they  are,  on  the  whole,  much  more  stable  than 
the  cuprous  compounds. 

MERCURY  CHLORIDES.  —  Mercuric  Chloride,  Hg//Cl2,  commonly  called  cor- 
rosive sublimate.  —  This  compound  may  be  obtained  by  several  different  pro- 
cesses: (1)  When  metallic  mercury  is  heated  in  chlorine  gas,  it  takes  fire 
and  burns,  producing  this  substance.  (2)  It  may  be  made  by  dissolving 
mercuric  oxide  in  hot  hydrochloric  acid,  crystals  of  corrosive  sublimate 
then  separating  on  cooling.  (3)  Or,  more  economically,  by  subliming  a 
mixture  of  equal  parts  of  mercuric  sulphate  and  dry  common  salt;  and 
this  is  the  plan  generally  followed.  The  decomposition  is  represented  by 
the  equation : 

SQ4Hg     -f     2NaCl     =     HgCl2     -f     S04Na2. 

Mercuric  Sodium  Mercuric  Sodium 

sulphate.  chloride.  chloride.  sulphate. 

Sublimed  mercuric  chloride  forms  a  white  transparent  crystalline  mass 
of  specific  gravity  543;  it  melts  at  265°  C,  (509°  F.);  boils  at  295°  C. 
(563°  F.),  and  volatilizes  somewhat  more  easily  than  calomel,  even  at 
ordinary  temperatures.  Its  observed  vapor-density,  referred  to  hydrogen 
as  unity,  is  140 :  and  the  density  calculated  from  the  formula  HgCl2,  sup- 
posing that  the  molecule  occupies  the  same  space  as  a  molecule  or  two  atoms 

200  -f  2  X  35-5 
of  hydrogen  (p.  229)  is  —      — - —    — =  135-5  ;  the  near  agreement  of  this 

number  with  the  observed  result  shows  that  the  vapor  is  in  the  normal  state 
of  condensation. 

Mercuric  chloride  dissolves  in  16  parts  of  cold  and  3  parts  of  boiling 
water,  and  crystallizes  from  a  hot  solution  in  long  white  prisms.  Alcohol 
and  ether  also  dissolve  it  with  facility ;  the  latter  even  withdraws  it  from 
a  watery  solution. 

Mercuric  chloride  combines  with  a  great  number  of  other  metallic  chlor- 
ides, forming  a  series  of  beautiful  double  salts,  of  which  the  ancient  sal 
alembroth  may  be  taken  as  a  good  example  :  it  contains  HgCl2 .  2NH4C1 .  OH2. 
Corrosive  sublimate  absorbs  ammoniacal  gas  with  great  avidity,  generating 
the  compound  HgCl2 .  NII3. 

Mercuric  chloride  forms  several  compounds  with  mercuric  oxide.  These 
are  produced  by  several  processes,  as  when  an  alkaline  carbonate  is  added 
in  varying  proportions  to  a  solution  of  mercuric  chloride.  They  differ 
greatly  in  color  and  physical  character,  and  are  mostly  decomposed  by 
water. 

Mercuric  chloride  forms  insoluble  compounds  with  many  of  the  azotized 
organic  principles,  as  albumin,  &c.  It  is  perhaps  to  this  property  that  its 
strong  antiseptic  properties  are  due.  Animal  and  vegetable  substances  are 
preserved  by  it  from  decay,  as  in  Ryan's  method  of  preserving  timber  and 
cordage.  Albumin  is  on  this  account  an  excellent  antidote  to  corrosive  subli- 
mate in  cases  of  poisoning. 

Mcrcurous  Chloride,  Hg2Cl2,  commonly  called  Calomel. — This  very  im- 
portant substance  may  be  easily  and  well  prepared  by  pouring  a  solution 
of  rnercurous  nitrate  into  a  large  excess  of  dilute  solution  of  common  salt. 
It  falls  as  a  dense  white  precipitate,  quite  insoluble  in  water ;  it  must  be 
thoroughly  washed  with  boiling  distilled  water,  and  dried.  Calomel  is, 
however,  generally  procured  by  another  and  more  complex  process.  Dry 


MERCURY.  359 

mercuric  sulphate  is  rubbed  in  a  mortar  with  as  much  metallic  mercury  as 
it  already  contains,  and  a  quantity  of  common  salt,  until  the  globules  dis- 
appear, and  a  uniform  mixture  has  been  produced.  This  is  subjected  to 
sublimation,  the  vapor  of  the  calomel  being  carried  into  an  atmosphere  of 
steam,  or  into  a  chamber  containing  air;  it  is  thus  condensed  into  a  mi- 
nutely divided  state,  and  the  laborious  process  of  pulverization  of  the  sub- 
limed mass  is  avoided.  The  reaction  is  thus  explained : 

S04Hg     -f     Hg     +     2NaCl      =     Hg2Cl2     -f     S04Na2 

Mercuric  Sodium  Mercurous  Sodium 

sulphate.  chloride.  chloride.  sulphate. 

Pure  calomel  is  a  heavy,  white,  insoluble,  tasteless  powder :  it  rises  in 
vapor  at  a  temperature  below  redness,  and  is  obtained  by  ordinary  sub- 
limation as  a  yellowish-white  crystalline  mass.  It  is  as  insoluble  in  cold 
diluted  nitric  acid  as  silver  chloride  ;  boiling-hot  strong  nitric  acid  oxidizes 
and  dissolves  it.  Calomel  is  instantly  decomposed  by  an  alkali,  or  by  lime- 
water,  with  production  of  mercurous  oxide.  It  is  sometimes  apt  to  con- 
tain a  little  mercuric  chloride,  which  would  be  a  very  dangerous  contami- 
nation in  calomel  employed  for  medical  purposes.  This  is  easily  discovered 
by  boiling  with  water,  filtering  the  liquid,  and  adding  caustic  potash.  Any 
corrosive  sublimate  is  indicated  by  a  yellow  precipitate. 

The  observed  vapor-density  of  calomel,  referred  to  hydrogen  as  unity, 
is  119-2.  Now  the  formula  Hg2Cl2,  if  it  represents  a  molecule  occupy- 
ing in  the  gaseous  state  two  volumes  (i.  e.,  twice  the  volume  of  an  atom 
of  hydrogen,  p.  229),  would  give  a  density  nearly  double  of  this  :  for 
400  -f-  2  x  35-5 

— 2 —        ~  —  235'5.     Hence  it  might  be  inferred  that  the  composition 

of  calomel  should  rather  be  represented  by  the  simpler  formula  HgCl,  which 
would  give  for  the  vapor-density  the  number  117-75.  But  this  formula 
(the  adoption  of  which  would,  of  course,  involve  that  of  similar  formulae 
for  the  other  mercurous  salts,  e,  g.,  N03Hg  for  the  nitrate)  is  objectionable 
on  account  of  its  inconsistency  with  the  law  of  even  numbers,  according  to 
which  a  dyad  element  like  mercury  can  never  unite  with  an  uneven  num- 
ber of  monad  atoms  (p.  232).  Moreover,  the  frequent  decomposition  of 
mercurous  salts  into  mercuric  salts  and  free  mercury  is  in  favor  of  the  sup- 
position that  their  molecules  contain  two  atoms  of  mercury;  and  the  anom- 
aly in  the  vapor-volume  of  calomel  may  be  explained  by  supposing  that 
the  vapor  of  this  compound,  like  that  of  many  others,  undergoes  at  high 
temperatures  the  change  known  as  dissociation  (p.  531),  the  two  volumes  of 
mercurous  chloride,  Hg2Cl,  being  resolved  into  two  volumes  of  mercuric 
chloride, HgCl2,  and  two  volumes  of  mercury,  Hg.  This  supposition  is,  to 
some  extent,  warranted  by  the  observation  that  calomel  vapor  amalgamates 
gold-leaf,  and  that  corrosive  sublimate  may  be  detected  in  resublimed  cal- 
omel. 

IODIDES. — Mercuric  Iodide,  Hg77!^  is  formed,  when  solution  of  potassium 
iodide  is  mixed  with  mercuric  chloride,  as  a  precipitate  which  is  at  first 
yellow,  but  in  a  few  moments  changes  to  a  most  brilliant  scarlet,  this  color 
being  retained  on  drying.  This  is  the  neutral  iodide :  it  may  be  made, 
although  of  rather  duller  tint,  by  triturating  equivalent  quantities  of  iodine 
and  mercury  with  a  little  alcohol.  In  preparing  it  by  precipitation,  it  is 
better  to  weigh  out  the  proper  proportions  of  the  two  salts,  as  the  iodide  is 
soluble  in  an  excess  of  either,  more  especially  in  excess  of  potassium  iodide. 
Mercuric  iodide  exhibits  a  very  remarkable  case  of  dimorphism,  attended 
with  difference  of  color,  which  is  red  or  yellow,  according  to  the  figure 
assumed.  Thus,  when  the  iodide  is  suddenly  exposed  to  a  high  tempera- 
ture, it  becomes  bright-yellow  throughout,  and  yields  ft  copious  sublimate 


360  DYAD  METALS. 

of  minute  but  brilliant  yellow  crystals.  If  in  this  state  it  be  touched  by  a 
hard  body,  it  instantly  becomes  red,  and  the  same  change  happens  spon- 
taneously after  a  certain  lapse  of  time.  On  the  other  hand,  by  a  very  slow 
and  careful  heating,  a  sublimate  of  red  crystals,  having  a  totally  different 
form,  may  be  obtained,  which  are  permanent.  The  same  kind  of  change 
happens  with  the  freshly  precipitated  iodide,  as  Mr.  Warington  has  shown, 
the  yellow  crystals  first  formed  breaking  up  in  the  course  of  a  few  seconds 
from  the  passage  of  the  salt  to  the  red  modification.* 

Mercuric  iodide  forms  double  salts  with  the  more  basic  or  positive  me- 
tallic iodides,  as  those  of  the  alkali-metals  and  alkaline  earth-metals ;  thus 
it  dissolves  in  aqueous  potassium  iodide,  and  the  hot  solution  deposits  on 
cooling,  crystals  of  potassio-mercuric  iodide,  2(KI.HgI2).30H2. 

Mercurous  Iodide,  Hg2I2,  is  formed  when  a  solution  of  potassium  iodide  is 
added  to  mercurous  nitrate :  it  then  separates  as  a  dirty  yellow,  insoluble 
precipitate,  with  a  tinge  of  green.  It  may  also  be  prepared  by  rubbing 
mercury  and  iodine  together  in  a  mortar  in  the  proportion  of  1  atom  of  the 
former  to  1  atom  of  the  latter,  the  mixture  being  moistened  from  time  to 
time  with  a  little  alcohol. 

OXIDES.  —  Monoxide,  or  Mercurous  Oxide,  HgO,  commonly  called  Red  Oxide 
of  Mercury,  or  Red  Precipitate.  —  There  are  numerous  methods  by  which  this 
compound  may  be  obtained.  The  following  may  be  cited  as  the  most  im- 
portant: (1)  By  exposing  mercury  in  a  glass  flask  with  a  long  narrow  neck, 
for  several  weeks,  to  a  temperature  approaching  315°  C.  (599°  F.).  The 
product  has  a  dark  red  color,  and  is  highly  crystalline;  it  is  the  red  precipi- 
tate of  the  old  writers.  (2)  By  cautiously  heating  any  of  the  mercuric  or 
mercurous  nitrates  to  complete  decomposition,  whereby  the  acid  is  decom- 
posed and  expelled,  oxidizing  the  metal  to  a  maximum,  if  it  happen  to  be 
in  the  state  of  mercurous  salt.  The  product  thus  obtained  is  also  crystal- 
line and  very  dense,  but  has  a  much  paler  color  than  the  preceding ;  while 
hot,  it  is  nearly  black.  It  is  by  this  method  that  the  oxide  is  generally  pre- 
pared: it  is  apt  to  contain  undecomposed  nitrate,  which  may  be  discovered 
by  strongly  heating  a  portion  in  a  test-tube :  if  red  fumes  are  produced, 
or  the  odor  of  nitrous  acid  exhaled,  the  oxide  has  been  insufficiently  heated 
in  the  process  of  manufacture.  (3)  By  adding  caustic  potash  in  excess  to 
a  solution  of  corrosive  sublimate,  by  which  a  bright  yellow  precipitate  of 
mercuric  oxide  is  thrown  down,  which  differs  from  the  foregoing  prepara- 
tions merely  in  being  destitute  of  crystalline  texture  and  much  more  mi- 
nutely divided.  It  must  be  well  washed  and  dried. 

Mercuric  oxide  is  slightly  soluble  in  water,  communicating  to  the  latter 
an  alkaline  reaction  and  metallic  taste:  it  is  highly  poisonous.  When 
strongly  heated,  it  is  decomposed,  as  before  observed,  into  metallic  mercury 
and  oxygen  gas. 

Mercurous  Oxide,  Hg20  ;  Suboxide,  or  Gray  Oxide  of  Mercury.  — This  oxide  is 
easily  prepared  by  adding  caustic  potash  to  mercurous  nitrate,  or  by  di- 
gesting calomel  in  solution  of  caustic  alkali.  It  is  a  dark  gray,  nearly 
black,  heavy  powder,  insoluble  in  water,  slowly  decomposed  by  the  action 
of  light  into  metallic  mercury  and  red  oxide.  The  preparations  known  in 
pharmacy  by  the  names  blue  pill,  gray  ointment,  mercury  with  chalk,  &c.,  often 
supposed  to  owe  their  efficacy  to  this  substance,  merely  contain  the  finely 
divided  metal. 

MERCURY  NITRATES. — Nitric  acid  varies  in  its  action  upon  mercury, 
according  to  the  temperature.  When  cold  and  somewhat  diluted,  it  forms 
only  mercurous  salts,  and  these  are  neutral  or  basic  —  i.  e.,  oxynitrates 

*  Memoirs  of  the  Chemical  Society  of  London,  i.  85. 


MEKCUliY.  361 

(p.  283)  —  as  the  acid  or  the  metal  happens  to  be  in  excess.  When,  on  the 
contrary,  the  nitric  acid  is  concentrated  and  hot,  the  mercury  is  raised  to 
its  highest  state  of  oxidation,  and  a  mercuric  salt  is  produced.  Both  classes 
of  salts  are  apt  to  be  decomposed  by  a  large  quantity  of  water,  giving  rise 
to  insoluble,  or  sparingly  soluble  basic  compounds. 

Mercuric  Nitrates.  —  By  dissolving  mercuric  oxide  in  excess  of  nitric  acid, 
and  evaporating  gently,  a  syrupy  liquid  is  obtained,  which,  enclosed  in  a 
bell-jar  over  lime  or  sulphuric  acid,  deposits  bulky  crystals  and  crystalline 
crusts,  both  having  the  composition  2(N03)2Hg//.OH2.  The  same  substance 
is  deposited  from  the  syrupy  liquid  as  a  crystalline  powder  by  dropping  it 
into  concentrated  nitric  acid.  The  syrupy  liquid  itself  appears  to  be  a  de- 
finite compound  containing  (N03)2Hg//.OH2.  By  saturating  hot  dilute  nitric 
'acid  with  mercuric  oxide,  a  salt  is  obtained  on  cooling,  which  crystallizes 
in  needles,  permanent  in  the  air,  containing  (N03)2Hg//  .  Hg//O.OH2.  The 
preceding  crystallized  salts  are  decomposed  by  water,  with  production  of 
compounds  more  and  more  basic  as  the  washing  is  prolonged  or  the  tempe- 
rature of  the  water  raised. 

Mercurous  Nitrate,  (N03)2Hg2.20H2,  forms  large  colorless  crystals  soluble 
in  a  small  quantity  of  water  without  decomposition  ;  it  is  made  by  dissolving 
mercury  in  an  excess  of  cold  dilute  nitric  acid. 

When  excess  of  mercury  has  been  employed,  a  finely  crystallized  basic 
salt  is  deposited  after  some  time,  containing  2(N08)2Hg2*Hg20.30Hr  or 
2N205.3Hg20.30H2;  this  is  also  decomposed  by  water.  The  two  salts  are 
easily  distinguished  when  rubbed  in  a  mortar  with  a  little  sodium  chloride; 
the  neutral  compound  gives  sodium  nitrate  and  calomel;  the  basic  salt, 
sodium  nitrate  and  a  black  compound  of  calomel  with  niercurous  oxide.  A 
black  substance,  called  Hahnemann 's  soluble  mercury,  is  produced  when  am- 
monia in  small  quantity  is  dropped  into  a  solution  of  mercurous  nitrate: 
it  contains  N205.3Hg20.2NH3,  or,  according  to  Kane,  N205.2Hg20.2NH3; 
the  composition  of  this  preparation  evidently  varies  according  to  the  tem- 
perature and  the  concentration  of  the  solutions. 

MERCURY  SULPHATES. — Mercuric  Sulphate,  S04Hg//,  is  readily  prepared 
by  boiling  together  oil  of  vitriol  and  metallic  mercury  until  the  latter  is 
wholly  converted  into  a  heavy  white  crystalline  powder,  which  is  the  salt 
in  question;  the  excess  of  acid  is  then  removed  by  evaporation  carried  to 
perfect  dryness.  Equal  weights  of  acid  and  metal  may  be  conveniently  em- 
ployed. Water  decomposes  the  sulphate,  dissolving  out  an  acid  salt,  and 
leaving  an  insoluble,  yellow,  basic  compound,  formerly  called  turpith  or  tur- 
beth  mineral,  containing,  according  to  Kane's  analysis,  S04Hg//.2Hg//0>  or 
S03.3Hg/xO.  Long-continued  washing  with  hot  water  entirely  removes  the 
remaining  acid,  and  leaves  pure  mercuric  oxide. 

Mercurous  Sulphate,  S04Hg2,  falls  as  a  white  crystalline  powder  when  sul- 
phuric acid  is  added  to  a  solution  of  mercurous  nitrate :  it  is  but  slightly 
soluble  in  water. 

MERCURY  SULPHIDES.  —  Mercuric  Sulphide,  HgS,  occurs  native  as  cinnabar, 
a  dull  red  mineral,  which  is  the  most  important  ore  of  mercury.  Hydrogen 
sulphide  passed  in  small  quantity  into  a  solution  of  mercuric  nitrate,  or 
chloride,  forms  a  white  precipitate,  which  is  a  compound  of  mercuric  sul- 
phide with  the  salt  itself.  An  excess  of  the  gas  converts  the  whole  into 
sulphide,  the  color  at  the  same  time  changing  to  black.  When  this  black 
sulphide  is  sublimed,  it  becomes  dark-red  and  crystalline,  but  undergoes 
no  change  of  composition:  it  is  then  cinnabar  or  vermilion.  Mercuric  sul- 
phide is  most  easily  prepared  by  subliming  an  intimate  mixture  of  6  parts 
of  mercury  and  1  part  of  sulphur,  and  reducing  the  resulting  cinnabar  to 
very  fine  powder,  the  beauty  of  the  tint  depending  much  upon  the  extent 
31 


362  DYAD  METALS. 

to  which  division  is  carried.  The  red  or  crystalline  sulphide  may  also  be 
formed  directly,  without  sublimation,  by  heating  the  black  precipitated 
substance  in  a  solution  of  potassium  pentasulphide ;  the  mercuric  sulphide 
is,  in  fact,  soluble,  to  a  certain  extent,  in  the  alkaline  sulphides,  and  forms 
with  them  crystallizable  compounds. 

When  vermilion  is  heated  in  the  air,  it  yields  metallic  mercury  and  sul- 
phurous oxide :  it  resists  the  action  both  of  caustic  alkali  in  solution,  and 
of  strong  mineral  acids,  even  nitric,  and  is  attacked  only  by  nitromuriatic 
acid. 

Mercurous  sulphide,  Hg2S,  is  obtained  by  passing  hydrogen  sulphide  into 
a  solution  of  mercurous  nitrate,  as  a  black  precipitate,  which  is  resolved 
at  a  gentle  heat  into  mercuric  sulphide  and  metallic  mercury. 

AMMONIACAL  MERCURY  COMPOUNDS.  MERCURAMMONIUM  SALTS.  —  By  the 
action  of  ammonia  and  its  salts  on  mercury  compounds,  a  variety  of  sub- 
stances are  formed  which  may  be  regarded  as  salts  of  mercurammoniums 
—  that  is,  of  ammonium-molecules  in  which  the  hydrogen  is  more  or  less 
replaced  by  mercury,  in  the  proportion  of  100  or  200  parts  of  mercury  to 
1  part  of  hydrogen,  according  as  the  compound  is  formed  from  a  mercurous 
or  a  mercuric  salt.  The  following  are  the  most  important  of  these  com- 
pounds: — 

Mercuric  Compounds. — Mercuro-diammonium  chloride,  (N2H6Hg//)Cl2,  known 
in  pharmacy  as  fusible  white  precipitate,  is  produced  by  adding  potash  to  a 
solution  of  ammonio-mercuric  chloride,  (2NH4Cl.HgCl2),  or  by  dropping  a 
solution  of  mercuric  chloride  into  a  boiling  solution  of  sal-ammoniac  con- 
taining free  ammonia,  as  long  as  the  resulting  precipitate  redissolves :  it 
then  separates  on  cooling  in  regular  dodecahedrons.  At  a  gentle  heat  it 
gives  off  ammonia,  leaving  a  chloride  of  dimercur-ammonium  and  hydrogen, 
(NH2Hg")Cl.HCl: 

N2HcHg"Cl2    =    NH3Hg"Cl2    -f    NHS. 

Mercurammonium  chloride,  (NH2Hg//)Cl.  —  This  salt,  known  in  pharmacy 
as  infusible  white  precipitate,  is  formed  by  adding  ammonia  to  a  solution  of 
mercuric  chloride.  When  first  produced,  it  is  bulky  and  white,  but  by 
contact  with  hot  water,  or  by  much  washing  with  cold  water,  it  is  converted 
into  hydrated  dimercurammonium  chloride,  NHg//2C1.0H2. 

Trimercuro-diammonium  nitrate,  (N2H2Hg//3)(NO3)2.  20H2,  is  formed  as  a 
white  precipitate,  on  mixing  a  dilute  and  very  acid  solution  of  mercuric 
nitrate  with  very  dilute  ammonia. 

Trimercuro-diamine,  N2Hg//3,  a  compound  derived  from  a  double  molecule 
of  ammonia,  N2H6,  by  substitution  of  3  atoms  of  bivalent  mercury  for  6 
atoms  of  hydrogen,  is  formed  by  passing  dry  ammonia  gas  over  dry  pre- 
cipitated mercuric  oxide : 

3Hg"0     -f-     2NHS     =     N2Hg"3    -f     30H2. 

The  excess  of  oxide  being  removed  by  nitric  acid,  the  trimercuro-diamine 
is  obtained  as  a  dark-brown  powder,  which  explodes  by  heat,  friction, 
percussion,  or  contact  with  oil  of  vitriol,  almost  as  violently  as  nitrogen 
chloride. 

Dimercurammonium  chloride,  NHg//2C1.0H2,  is  obtained,  as  already  ob- 
served, by  boiling  mercurodiammonium  chloride  (infusible  white  precipi- 
tate) with  water.  It  is  a  heavy,  granular,  yellow  powder,  which  turns 
white  again  when  treated  with  sal-ammoniac. 

Dimercurammonium  iodide,  NHg//2I .  OH2.  —  This  compound  may  be  formed 
by  digesting  the  corresponding  chloride  in  a  solution  of  potassium  iodide; 
or  by  heating  mercuric  iodide  with  excess  of  aqueous  ammonia: 


MERCURY.  363 

2HgI2  +  4NH3  +  OH2  =  NHg"2I.OH2  +  3NH4I; 
also  by  passing  ammonia  gas  over  mercuric  oxy-iodide : 

Hg//4I203     -f     2NH3     =     2(NHg"2I.OH2)     -f     OH2; 

and,  lastly,  by  adding  ammonia  to  a  solution  of  potassio-mercuric  iodide 
mixed  with  caustic  potash: 

2(2KI.  HgI2)  +  NH3  +  3KHO  =  NHg"2I.  OH2  +  7KI  -f  20H2. 

This  last  reaction  affords  an  extremely  delicate  test  for  ammonia.  A  solu- 
tion of  potassio-mercuric  iodide  is  prepared  by  adding  potassium  iodide  to 
a  solution  of  corrosive  sublimate,  till  a  portion  only  of  the  resulting  red 
precipitate  is  redissolved,  then  filtering,  and  mixing  the  filtrate  with  caustic 
potash.  The  liquid  thus  obtained  forms,  with  a  very  small  quantity  of 
ammonia,  either  free  or  in  the  form  of  an  ammoniacal  salt,  a  brown  pre- 
cipitate soluble  in  excess  of  potassium  iodide.  This  is  called  Nessler's  test 
for  ammonia.* 

Dimercurammonium  hydrate,  NHg/x  2HO.  —  This  compound  is  formed  by 
treating  precipitated  mercuric  oxide  with  aqueous  ammonia,  or  by  treating 
either  of  the  dimercurammonium  salts  with  a  caustic  alkali.  It  is  a  brown 
powder,  which  dissolves  in  acids,  yielding  salts  of  dimercurammonium. 

Dimercurammonium  sulphate,  (NHg//2)2S04  .  20H2,  formerly  called  ammoni- 
acal turpethum,  is  prepared  by  dissolving  mercuric  sulphate  in  ammonia, 
and  precipitating  the  solution  with  water.  It  is  a  heavy  white  powder, 
yellowish  when  dry,  resolved  by  heat  into  water,  nitrogen,  ammonia,  and 
mercurous  sulphate. 

Mercurous  Compounds.  —  Mercurosammonium  chloride,  NH3Hg/Cl,  is  the 
black  precipitate  formed  when  dry  calomel  is  exposed  to  the  action  of  am- 
monia gas.  When  exposed  to  the  air,  it  gives  off  ammonia  and  leaves  white 
mercurous  chloride.  —  Dimer  cur  osamm.onium  chloride,  NH2Hg/2Cl,  is  formed, 
together  with  sal-ammoniac,  by  digesting  calomel  in  aqueous  ammonia: 

Hg2Cl2    +     2NH3    =    NH2Hg2Cl     +     NH4C1. 

It  is  gray  when  dry,  and  is  not  altered  by  boiling  water.  —  Dimercurosam- 
monium  nitrate,  2(NH2Hg2)N03.OII2.  This,  according  to  Kane,  is  the  com- 
position of  the  velvet-black  precipitate  known  as  Hahnemann's  soluble 
.  mercurj',  which  is  produced  on  adding  ammonia  to  a  solution  of  mercurous 
nitrate.  According  to  C.  G.  Mitscherlich,  on  the  other  hand,  the  precipi- 
tate thus  formed  has  the  composition  2NH3.N2O5.3Hg20,  which  is  that  of 
a  hydrated  trimercurosammonium  nitrate,  2(NHHg3)N03.20H2. 

Reactions  of  Mercury  Salts.  —  All  mercury  compounds  are  volatilized  or 
decomposed  by  a  temperature  of  ignition :  those  which  fail  to  yield  the 
metal  by  simple  heating  may  in  all  cases  be  made  to  do  so  by  heating  in  a 
test-tube  with  a  little  dry  sodium  carbonate.  The  metal  is  precipitated 
from  its  soluble  combinations  by  a  plate  of  copper,  and  also  by  a  solution 
of  stannous  chloride  used  in  excess. 

Hydrogen  sulphide,  and  ammonium  sulphide,  produce  in  solutions,  both  of 
mercuric  and  of  mercurous  salts,  black  precipitates  insoluble  in  ammonium 
sulphide.  In  mercuric  salts,  however,  if  the  quantity  of  the  reagent  added 
is  not  sufficient  for  complete  decomposition,  a  white  precipitate  is  formed, 
consisting  of  a  compound  of  mercuric  sulphide  with  the  original  salt,  and 
often  colored  yellow  or  brown  by  excess  of  mercuric  sulphide.  An  excess 

*  Chemical  Gazette,  1856,  pp.  445,  463. 


364  DYAD    METALS. 

of  hydrogen  sulphide,  or  ammonium  sulphide,  instantly  turns  the  precipi- 
tate black.  This  reaction  is  quite  characteristic  of  mercuric  salts 

Mercuric  salts  are  further  distinguished  by  forming  a  yellow  precipitate 
with  caustic  potash  or  soda ;  white  with  ammonia  or  ammonium  carbonate,  in- 
soluble in  excess:  red-brown  with  potassium  or  sodium  carbonate.  With 
potassium  iodide  they  yield  a  bright  scarlet  precipitate,  soluble  in  excess, 
either  of  the  mercuric  salt  or  of  the  alkaline  iodide. 

Mercurous  salts  are  especially  characterized  by  forming  with  hydrochloric 
acid  or  soluble  chlorides,  a  white  precipitate  which  is  turned  black  by  am- 
monia. They  also  yield  black  precipitates  with  caustic  alkalies,  white  with 
alkaline  carbonates,  soon  turning  black  ;  greenish-yellow  with  potassium  iodide. 


Alloys  of  mercury  with  other  metals  are  termed  amalgams:  mercury  dis- 
solves in  this  manner  many  of  the  metals,  as  gold,  silver,  tin,  lead,  &c. 
These  combinations  sometimes  take  place  with  considerable  violence,  as  in 
the  case  of  potassium,  in  which  light  and  heat  are  produced ;  besides  this, 
many  of  the  amalgams  crystallize  after  a  while,  becoming  solid.  The 
amalgam  of  tin  used  in  silvering  looking-glasses,  and  that  of  silver  and  of 
copper,  sometimes  employed  for  stopping  hollow  teeth,  are  examples. 


CLASS  III— TRIAD  METALS. 


THALLIUM. 

Atomic  weight,  204.     Symbol,  Tl. 

rpHIS  element  was  discovered  by  Crookes,  in  1861,  in  the  seleniferous 
JL  deposit  of  a  lead-chamber  of  a  sulphuric  acid  factory  in  the  Hartz 
mountains,  where  iron  pyrites  is  used  for  the  manufacture  of  sulphuric 
acid.  The  name  is  derived  from  0aAAd,-,  "green,"  because  its  existence  was 
first  recognized  by  an  intense  green  line,  appearing  in  the  spectrum  of  a 
flame  in  which  thallium  is  volatilized.  It  was  at  first  suspected  to  be  a 
metalloid,  but  further  examination  proved  it  to  be  a  true  metal.  It  was 
first,  obtained  in  a  distinct  metallic  form  by  Crookes  towards  the  end  of  the 
year  1861,  and  soon  afterwards  by  Lamy,  who  prepared  it  from  the  deposit 
in  the  lead-chamber  of  M.  Kuhlmann,  of  Lille,  where  Belgian  pyrites  is 
employed  for  the  manufacture  of  sulphuric  acid. 

Thallium  appears  to  be  very  widely  diffused  as  a  constituent  of  iron  and 
copper  pyrites,  though  it  never  constitutes  more  than  the  4000th  part  of 
the  bulk  of  the  ores.  It  has  also  been  found  in  lepidolite  from  Moravia, 
in  mica  from  Zinnwald  in  Bohemia,  and  in  the  mother-liquors  of  the  salt 
works  at  Nauheim. 

Thallium  is  most  economically  prepared  from  the  flue-dust  of  pyrites 
burners.  This  substance  is  stirred  up  in  wooden  tubs  with  boiling  water, 
and  the  clear  liquor  siphoned  off  from  the  deposit  is  mixed  with  excess  of 
strong  hydrochloric  acid,  which  precipitates  impure  thallium  monochloride. 
To  obtain  a  pure  salt,  this  crude  chloride  is  added  by  small  portions  at  a 
^ime  to  half  its  weight  of  hot  oil  of  vitriol  in  a  porcelain  or  platinum  dish, 
the  mixture  being  constantly  stirred,  and  the  heat  continued  till  the  whole 
of  the  hydrochloric  acid  and  the  greater  portion  of  the  excess  of  sulphuric 
acid  are  driven  off.  The  fused  acid  sulphate  is  now  to  be  dissolved  in  an 
excess  of  water,  and  an  abundant  stream  of  hydrogen  sulphide  passed 
through  the  solution.  The  precipitate,  which  may  contain  arsenic,  anti- 
mony, bismuth,  lead,  mercury,  and  silver,  is  separated  by  filtration,  and 
the  filtrate  is  boiled  till  all  free  hydrogen  sulphide  is  removed.  The  liquid 
is  now  to  be  rendered  alkaline  with  ammonia,  and  boiled;  the  precipitate 
of  iron  oxide  and  alumina,  which  generally  appears  in  this  place,  is  filtered 
off:  and  the  clear  solution  evaporated  to  a  small  bulk.  Thallium  sulphate 
then  separates  on  cooling,  in  long,  clear  prismatic  crystals. 

Metallic  thallium  may  be  reduced  from  the  solution  of  the  sulphate,  either 
by  electrolysis,  or  by  the  action  of  zinc. 

Thallium  is  a  heavy  metal,  resembling  lead  in  its  physical  properties. 
When  freshly  cut,  it  exhibits  a  brilliant  metallic  lustre  and  grayish  color, 
somewhat  between  those  of  silver  and  lead,  assuming  a  slight  yellowish 
tint  by  friction  with  harder  bodies.  It  is  very  soft,  being  readily  cut  with 
a  knife,  and  making  a  streak  on  paper  like  plumbago.  It  is  very  malleable, 
is  not  easily  drawn  into  wire,  but  may  be  readily  squeezed  into  that  form 
31*  365 


366  TRIAD    METALS. 

by  the  process  technically  called  "squirting."  It  has  a  highly  crystalline 
structure,  and  crackles  like  tin  when  bent.  It  melts  at  294°. 

In  contact  with  the  air,  thallium  tarnishes  more,  rapidly  than  lead, 
becoming  coated  with  a  thin  layer  of  oxide,  which  preserves  the  rest  of 
the  metal. 

The  most  characteristic  property  of  thallium  is  the  intense  green  color 
which  the  metal  or  any  of  its  compounds  impart  to  a  colorless  flame ;  and 
this  color,  when  viewed  by  the  spectroscope,  is  seen  to  be  absolutely  mono- 
chromatic, appearing  as  one  intensely  brilliant  and  sharp  green  line. 

Thallium  dissolves  in  hydrochloric,  sulphuric,  and  nitric  acids,  the  latter 
attacking  it  very  energetically,  with  copious  evolution  of  red  vapors. 

Thallium  forms  two  classes  of  compounds  —  namely,  the  thallious  com- 
pounds, in  which  it  is  univalent ;  and  the  thallic  compounds,  in  which  it  is 
trivalent.  Thus  it  forms  two  oxides,  T120  and  T1203,  with  corresponding 
chlorides,  bromides,  iodides,  and  oxygen-salts.  In  some  of  its  chemical 
relations  it  resembles  the  alkali-metals,  forming  a  readily  soluble  and  highly 
alkaline  monoxide,  a  soluble  and  alkaline  carbonate,  an  insoluble  platino- 
chloride,  a  thallio-aluminic  sulphate,  similar  in  form  and -composition  to 
common  potash-alum,  arid  several  phosphates  exactly  analogous  in  compo- 
sition to  the  phosphates  of  sodium.  In  most  respects,  however,  it  is  more 
nearly  allied  to  the  heavy  metals,  especially  to  lead,  which  it  resembles 
closely  in  appearance,  density,  melting  point,  specific  heat,  and  electric 
conductivity. 

THALLIUM  CHLORIDES.  —  Thallium  forms  four  chlorides,  represented  by 
the  formulae  T1C1,  T14C16,  T12C14,  and  T1C13;  the  second  and  third  of  which 
may  be  regarded  as  compounds  of  the  monochloride  and  trichloride. 

The  monochloride  or  Thallious  chloride,  T1C1,  is  formed  by  direct  combina- 
tion, the  metal  burning  when  heated  in  chlorine  gas ;  or  as  a  white  curdy 
precipitate,  resembling  silver  chloride,  by  treating  the  solution  of  any 
thallious  salt  with  a  soluble  chloride.  When  boiled  with  water  it  dissolves 
like  lead  chloride,  and  separates  in  white  crystals  on  cooling.  It  forms 
double  salts  with  trichloride  of  gold  and  tetrachloride  of  platinum.  The 
platinum-salt,  2T1C1.  PtCl4.  separates  as  a  pale  yellow  very  slightly  soluble 
crystalline  powder,  on  adding  platinic  chloride  to  thallious  chloride. 

The  trichloride  or  Thallic  chloride,  T1C13,  is  obtained  by  dissolving  the  tri- 
oxide  in  hydrochloric  acid,  or  by  acting  upon  thallium,  or  one  of  the  lower 
chlorides,  with  a  large  excess  of  chlorine  at  a  gentle  heat.  It  is  soluble  in 
water,  and  separates  by  evaporation  in  a  vacuum  in  hydrated  crystals; 
melts  easily,  and  decomposes  at  a  high  temperature.  It  forms  crystalline 
double  salts  with  the  chlorides  of  the  alkali-metals. 

The  sesquichloride,  T14C16  =  T1C13.3T1C1,  is  produced  by  dissolving  thal- 
lium or  the  monochloride  in  nitromuriatic  acid,  and  separates  on  cooling 
in  yellow  crystalline  scales.  By  aqueous  ammonia,  potash,  or  even  by 
thallious  oxide,  it  is  instantly  decomposed  into  sesquioxide  and  mono- 
chloride,  according  to  the  equation: 

2T14C16  -f  3KHO  =  T1203  -f  6T1C1  -f  3KC1  +  3HC1. 

The  dichloride,  T12C14  =  T1C13.T1C1,  is  formed  by  carefully  heating  thal- 
lium, or  the  monochloride,  in  a  slow  current  of  chlorine.  It  is  a  pale-yel- 
low substance  reduced  to  sesquichloride  by  further  heating. 

The  BROMIDES  of  thallium  resemble  the  chlorides. 

IODIDES.  —  Thallious  iodide,  Til,  is  formed  by  direct  combination  of  its 
elements,  or  by  double  decomposition.  It  forms  a  beautiful  yellow  powder, 
rather  daj-ker  than  sulphur,  and  melting,  below  redness,  to  a  scarlet  liquid, 


THALLIUM.  367 

which,  as  the  mass  cools,  remains  scarlet  for  some  time  after  solidification, 
then  changes  to  bright-yellow.  The  dried  precipitate,  when  spread  on 
paper  with  a  little  gum-water,  undergoes  a  similar  but  opposite  change  to 
that  experienced  by  mercuric  iodide  when  heated,  the  yellow  surface  when 
held  over  a  flame  suddenly  becoming  scarlet,  and  frequently  remaining  so 
after  cooling  for  several  days ;  hard  friction  with  a  glass  rod,  however, 
changes  the  scarlet  color  back  to  yellow.  It  is  very  slightly  soluble  in 
water,  requiring,  according  to  Crookes,  4453  parts  of  water  at  17-2°,  and 
842-4  parts  at  100°,  to  dissolve  it. 

Thallic  iodide,  T1C13,  is  formed  by  the  action  of  thallium  on  iodine  dis- 
solved in  ether,  as  a  brown  solution  which  gradually  deposits  rhombic 
prisms.  It  forms  crystalline  compounds  with  the  iodides  of  the  alkali- 
metals. 

THALLIUM  OXIDES. — Thallium  forms  a  monoxide  and  a  trioxide. 

The  monoxide,  or  Thallious  oxide,  T120,  constitutes  the  chief  part  of  the 
crust  which  forms  on  the  surface  of  the  metal  when  exposed  to  the  air.  It 
may  be  prepared  by  allowing  granulated  thallium  to  oxidize  in  warm  moist 
air,  and  then  boiling  with  water.  The  filtered  solution  first  deposits  white 
needles  of  thallium  carbonate,  and,  on  further  cooling,  yellow  needles  of 
the  hydrate,  T1HO  or  T12O.H20,  which,  when  left  over  oil  of  vitriol  in  a 
vacuum,  yields  the  anhydrous  monoxide  as  a  reddish-black  mass  retaining 
the  shape  of  the  crystals.  It  is  partially  reduced  to  metal  by  hydrogen  at 
a  red  heat.  When  fused  with  sulphur  it  yields  thallious  sulphide.  It  dis- 
solves readily  in  water,  forming  a  colorless  strongly  alkaline  solution,  which 
re-acts  with  metallic  salts  very  much  like  caustic  potash.  This  solution 
treated  with  zinc,  or  subjected  to  electrolysis,  yields  metallic  thallium. 

The  trioxide,  or  Thallic  oxide,  is  the  chief  product  obtained  by  burning 
thallium  in  oxygen  gas.  It  is  best  prepared  by  adding  potash  to  the  solu- 
tion of  a  thallic  salt,  and  drying  the  precipitate  at  260°  C.  (500°  F.).  It 
is  also  formed  by  electrolysis  of  thallious  sulphate.  It  is  a  dark-red  pow- 
der reduced  to  thallious  oxide  at  a  red  heat;  neutral,  insoluble  in  water 
and  in  alkalies.  Thallic  hydrate,  T1//XH02,  is  obtained  by  drying  the 
above-mentioned  precipitate  at  100°. 

OXYGEN  SALTS.  — Both  the  oxides  of  thallium  dissolve  readily  in  acids, 
forming  crystalline  salts,  soluble  in  water;  there  are  also  a  few  insoluble 
•thallium  salts  formed  by  double  decomposition. 

Thallious  Carbonate,  C03T12,  is  deposited  in  crystals,  apparently  trimetric, 
when  a  solution  of  thallious  oxide  is  exposed  to  the  air.  It  is  soluble  in 
water,  and  the  solution  has  a  slightly  caustic  taste  and  alkaline  reaction. 

Sulphates.  —  Thallious  sulphate,  S04T12,  obtained  by  evaporating  the 
chloride  or  nitrate  with  sulphuric  acid,  or  by  heating  metallic  thallium 
with  that  acid,  crystallizes  in  anhydrous  rhombic  prisms,  isomorphous  with 
potassium  sulphate.  It  forms,  with  aluminium  sulphate,  the  salt  (SO4)2 
A1X//T1.  120H2,  isomorphous  with  common  alum;  and  with  the  sulphates 
of  magnesium,  nickel,  &c.,  double  salts  containing  6  molecules  of  water, 
and  isomorphous  with  magnesium  and  potassium  sulphate,  &c.  (p.  349). — 
Thallic  sulphate,  (S04)3T12///.70H2,  separates  by  evaporation  from  a  solution 
of  thallic  oxide  in  dilute  sulphuric  acid,  in  thin  colorless  lamina^  which  are 
decomposed  by  water,  even  in  the  cold,  with  separation  of  brown  thallic 
oxide. 

Phosphates.  — The  thallious  phosphates  form  a  series  nearly  as  complete 
as  those  of  the  alkali-metals,  which  they  also  resemble  in  their  behavior 
when  heated.  There  are  three  orlhophosphates  containing  respectively  P(>4 
H2T1,  P04HT12,  and  P04T13.  The  first  two  are  soluble  in  water;  the  sc-coii.t 
is  obtained  by  neutralizing  dilute  phosphoric  acid  at  boiling  heat  with  thai- 


368  TRIAD    METALS. 

lious  carbonate;  and  the  first  by  mixing  the  dithallious  salt  with  excess  of 
phosphoric  acid.  The  trithallious  salt,  P04Tlg,  is  very  sparingly  soluble, 
and  is  formed  as  a  crystalline  precipitate  on  mixing  the  saturated  solutions 
•of  ordinary  disodic  phosphate  and  thallious  sulphate;  also,  together  with 
ammonio-thallious  phosphate,  by  treating  the  monothallious  or  dithallious 
salt  with  excess  of  ammonia.  There  are  two  thallious  pyrophosphates,  P207 
H2T12  and  P207T14,  both  very  soluble  in  water :  the  first  produced  by  care- 
fully heating  monothallious  orthophosphate,  the  second  by  strongly  heating 
dithallious  orthophosphate.  Of  thallious  metaphosphate,  P03T1,  there  are 
two  modifications :  the  first  remaining  as  a  slightly  soluble  vitreous  mass 
when  monothallious  orthophosphate  is  strongly  ignited,  the  second  obtained 
as  an  easily  soluble  glass  by  igniting  ammonio-thallious  01  thophosphate. 

Thallic  orthophosphate,  P04T1/X/.  20H2,  separates  as  an  insoluble  gelatinous 
precipitate  on  diluting  a  solution  of  thallic  nitrate  mixed  with  phosphoric 
acid. 

THALLIUM  SULPHIDE,  T12S.  —  This  compound  is  precipitated  from  all  thal- 
lious salts  by  ammonium  sulphide,  and  from  the  acetate,  carbonate,  or 
oxalate,  by  hydrogen  sulphide  (incompletely  also  from  the  nitrate,  sulphate 
or  chloride),  in  dense  flocks  of  a  grayish  or  brownish-black  color.  Thallic 
salts  appear  to  be  reduced  to  thallious  salts  by  boiling  with  ammonium 
sulphide.  Thallium  sulphate  projected  into  fused  potassium  cyanide  is  re- 
duced to  sulphide,  which  then  forms  a  brittle  metallic-looking  mass,  having 
the  lustre  of  plumbago,  and  fusing  more  readily  than  metallic  thallium. 


Reactions  of  Thallium  salts.  —  The  reactions  of  thallious  salts  with  hydrogen 
sulphide  and  ammonium  sulphide  have  just  been  mentioned.  From  their 
aqueous  solutions  thallium  is  rapidly  precipitated  in  metallic  crystals  by 
zinc,  slowly  by  iron.  Soluble  chlorides  precipitate  difficultly  soluble  white 
thallious  chloride ;  soluble  bromides  throw  down  white,  nearly  insoluble 
bromide ;  soluble  iodides  precipitate  insoluble  yellow  thallious  iodide. 
Caustic  alkalies  and  alkaline  carbonates  form  no  precipitate;  sodium  phos- 
phate forms  a  white  precipitate,  insoluble  in  ammonia,  easily  soluble  in 
acids. 

Potassium  chromate  gives  a  yellow  precipitate  of  thallious  chromate,  in- 
soluble in  cold  nitric  or  sulphuric  acid,  but  turning  orange-red  on  boiling 
in  the  acid  solution.  —  Platinic  chloride  precipitates  a  very  pale-yellow  in- 
soluble double  salt. 

Thallic  sails  are  easily  distinguished  from  thallious  salts  by  their  be- 
haviour with  alkalies,  and  with  soluble  chlorides  or  bromides.  Their  solu- 
tions give  with  ammonia,  and  with  fixed  alkalies  and  their  carbonates,  a  brown 
gelatinous  precipitate  of  thallic  oxide,  containing  the  whole  of  the  thallium. 
Soluble  chlorides  or  bromides  produce  no  precipitate  in  solutions  of  pure 
thallic  salts ;  but  if  a  thallious  salt  is  likewise  present,  a  precipitate  of 
scsquichloride  or  sesquibromide  is  formed.  Oxalic  acid  forms  in  solutions 
of  thallic  salts  a  white  pulverulent  precipitate ;  phosphoric  acid  a  white 
gelatinous  precipitate;  and  arsenic  acid  a  yellow  gelatinous  precipitate. 
Thallic  nitrate  gives  with  potassium  ferrocyanide  a  green,  and  with  the  ferri- 
cyanide  a  -yellow  precipitate. 

In  examining  a  mixed  metallic  solution,  thallium  will  be  found  in  the 
precipitate  thrown  down  by  ammonium  sulphide,  together  with  iron,  nickel, 
manganese,  &c.  From  these  metals  it  may  be  easily  separated  by  precipi- 
tation with  potassium  iodide  or  platinic  chloride,  or  by  reduction  to  the 
metallic  state  with  zinc. 

Thallium  salts  are  reduced  before  the  blowpipe  with  charcoal  and  sodium 
carbonate  or  potassium  cyanide.  The  green  color  imparted  to  flame  by 
thallium,  and  the  peculiar  character  of  its  spectrum,  have  already  been 
mentioned. 


GOLD.  369 


GOLD, 

Atomic  weight,  196-7.     Symbol,  Au  (Aurum). 

Gold,  in  small  quantities,  is  a  very  widely  diffused  metal ;  traces  of  it  are 
constantly  found  in  the  iron  pyrites  of  the  more  ancient  rocks.  It  is  always 
met  with  in  the  metallic  state,  sometimes  beautifully  crystallized  in  the  cubic 
form,  associated  with  quartz,  iron  oxide,  and  other  substances,  in  regular 
mineral  veins.  The  sands  of  various  rivers  have  long  furnished  gold  derived 
from  this  source,  and  separable  by  a  simple  process  of  washing ;  such  is  the 
gold-dust  of  commerce.  When  a  veinstone  is  wrought  for  gold,  it  is  stamped 
to  powder,  and  shaken  in  a  suitable  apparatus  with  water  and  mercury ;  an 
amalgam  is  thus  formed,  which  is  afterwards  separated  from  the  mixture 
and  decomposed  by  distillation.  Formerly,  the  chief  supply  of  gold  was 
obtained  from  the  mines  of  Brazil,  Hungary,  and  the  Ural  mountains;  but 
California  and  Australia  now  yield  by  far  the  largest  quantity.  The  new 
gold-field  of  British  Columbia  is  also  very  productive. 

Native  gold  is  almost  always  alloyed  with  silver.  The  purest  specimens 
have  been  obtained  from  Schabrowski,  near  Katharinenburg,  in  the  Ural. 
A  specimen  analyzed  by  Gustav  Rose  was  found  to  contain  98-96  per  cent, 
of  gold.  The  Californian  gold  averages  from  87-5  to  88-5  per  cent.,  and 
the  Australian  from  96  to  96-6  per  cent.  In  some  specimens  of  native  gold,  as 
in  that  from  Linarowski,  in  the  Altai  mountains,  the  percentage  of  gold  is 
as  low  as  60  per  cent.,  the  remainder  being  silver.  There  is  also  an  auri- 
ferous silver  found  at  Konigsberg,  in  Hungary,  containing  28  per  cent,  of 
gold  and  72  of  silver. 

Pure  gold  is  obtained  from  its  alloys  by  solution  in  nitro-muriatic  acid 
and  precipitation  with  a  ferrous  salt,  which  reduces  the  gold,  and  is  itself 
converted  into  a  ferric  salt,  thus : 

6S04Fe  +  2AuCl3  =  2(S04)3Fe'"2  -f  Fe///2Cl6  +  Au2. 

Ferrous  Auric  Ferric  Ferric  Gold, 

sulphate.         «hloride.  sulphate.  chloride. 

The  gold  falls  as  a  brown  powder  which  acquires  the  metallic  lustre  by 
friction. 

.Gold  is  a  soft  metal,  having  a  beautiful  yellow  color.  It  surpasses  all 
other  metals  in  malleability,  the  thinnest  gold  leaf  not  exceeding,  it  is  said, 
Tfftfhnnr  °^  an  incn  m  thickness,  while  the  gilding  on  the  silver  wire  used  in 
the  manufacture  of  g old-lace  is  still  thinner.  It  may  also  be  drawn  into 
very  fine  wire.  Gold  has  a  density  of  19-5:  it  melts  at  a  temperature  a 
little  above  the  fusing  point  of  silver.  Neither  air  nor  water  affects  it  in 
the  least  at  any  temperature ;  the  ordinary  acids  fail  to  attack  it  singly.  A 
mixture  of  nitric  and  hydrochloric  acids  dissolves  gold,  however,  with  ease, 
the  active  agent  being  the  liberated  chlorine. 

Gold  forms  two  series  of  compounds :  the  aurous  compounds,  in  which  it  is 
univalent,  as  AuCl,  Au20,  &c.,  and  the  auric  compound,  in  which  it  is  triva- 
lent,  as  Au'"Cl3,  Au'"20a,  &c. 

CHLORIDES.  —  The  mono  chloride  or  Aurous  chloride,  AuCl,  is  produced  when 

ic  trichloride  is  evaporated  to  dryness,  and  exposed  to  a  heat  of  227°  C. 

(440°  F.),  until  chlorine  ceases  to  be  exhaled.     It  forms  a  yellowish-white 

lass,  insoluble  in  water.     In   contact  with  that  liquid  it  is  decomposed 

lowly  in  the  cold,  and  rapidly  by  the  aid  of  heat,  into  metallic  gold  and 

trichloride. 

The  trichloride,  or  Auric  chloride,  AuCl3,  is  the  most  important  compound 
'  gold  :  it  is  always  produced  when  gold  is  dissolved  in  nitro-muriatic  acid. 


370  TRIAD   METALS. 

The  deep-yellow  solution  thus  obtained  yields,  by  evaporation,  yellow  crys- 
tals of  the  double  chloride  of  gold  and  hydrogen :  when  this  is  cautiously 
heated,  hydrochloric  acid  is  expelled,  and  the  residue,  on  cooling,  solidifies 
to  a  red  crystalline  mass  of  auric  chloride,  very  deliquescent,  and  soluble  in 
water,  alcohol,  and  ether.  Auric  chloride  combines  with  a  number  of  me- 
tallic chlorides,  forming  a  series  of  double  salts,  called  chloro-aurates,  of 
which  the  general  formula  in  the  anhydrous  state  is  MCl.AuCl3,  M  repre- 
senting an  atom  of  a  monad  metal.  These  compounds  are  mostly  yellow 
when  in  crystals,  and  red  when  deprived  of  water.  The  ammonium  salt, 
NH4Cl.AuCl3.  OH2,  crystallizes  in  transparent  needles;  the  sodium  salt, 
NaCl.  AuCl3 .  20H2,  in  long  four-sided  prisms.  Auric  chloride  likewise  forms 
crystalline  double  salts  with  the  hydrochlorides  of  many  organic  bases. 

A  mixture  of  auric  chloride  with  excess  of  acid  potassium  or  sodium  car- 
bonate is  used  for  gilding  small  ornamental  articles  of  copper:  these  are 
cleaned  by  dilute  nitric  acid,  and  then  boiled  in  the  mixture  for  some  time, 
by  which  means  they  acquire  a  thin  but  perfect  coating  of  reduced  gold. 

OXIDES.  —  The  monoxide,  or  Aurous  oxide,  is  produced  when  caustic  potash 
in  solution  is  poured  upon  the  monochloride.  It  is  a  green  powder,  partly 
soluble  in  the  alkaline  liquid  ;  the  solution  rapidly  decomposes  into  metallic 
gold,  which  subsides,  and  auric  oxide,  which  remains  dissolved. 

Trioxide,  or  Auric  oxide,  Au03. — When  magnesia  is  added  to  auric  chlor- 
ide, and  the  sparingly  soluble  aurate  of  magnesium  well  washed  and 
digested  with  nitric  acid,  auric  oxide  is  left  as  an  insoluble  reddish-yellow 
powder,  which  when  dry  becomes  chestnut-brown.  It  is  easily  reduced  by 
heat,  and  also  by  mere  exposure  to  light;  it  is  insoluble  in  oxygen-acids, 
with  the  exception  of  strong  nitric  acid,  insoluble  in  hydrofluoric  acid, 
easily  dissolved  by  hydrochloric  and  hydrobromic  acids.  Alkalies  dissolve 
it  freely:  indeed,  the  acid  properties  of  this  substance  are  very  strongly 
marked ;  it  partially  decomposes  a  solution  of  potassium  chloride  when 
boiled  with  that  liquid,  potassium  hydrate  being  produced.  When  digested 
with  ammonia,  it  yields  fulminating  gold  consisting,  according  to  Berzelius, 
of  Au203.4NH3  OH2. 

The  compounds  of  auric  oxide  with  alkalies  are  called  auratcs.  The 
potassium  salt,  Au203.OK2 .  60H2,  or  Au02K.30H2,  is  a  crystalline  salt,  the 
solution  of  which  is  sometimes  used  as  a  bath  for  electro-gilding.  A  com- 
pound of  aurate  and  acid  sulphite  of  potassium,  or  potassium  aurosulphite, 
2(Au02K.4S03HK) .  OII2.  is  deposited  in  yellow  needles  when  potassium 
sulphite  is  added,  drop  by  drop,  to  an  alkaline  solution  of  potassium  aurate. 
-  Gold  shows  but  little  tendency  to  form  oxygen-salts.  Auric  oxide  dis- 
solves in  strong  nitric  acid,  but  the  solution  is  decomposed  by  evaporation 
or  dilution.  A  sodio-aurous  hyposulphite,  (S203)2AuNa3.20H2,  is  prepared  by 
mixing  the  concentrated  solutions  of  auric  chloride  and  sodium  hyposul- 
phite, and  precipitating  with  alcohol.  It  is  very  soluble  in  water  and 
crystallizes  in  colorless  needles.  Its  solution  is  used  for  fixing  daguerreo- 
type pictures.  With  barium  chloride,  it  yields  a  gelatinous  precipitate  of 
bario-aurous  hyposulphite,  (S203)4Au2Ba/'/3. 

SULPHIDES. — Aurous  sulphide,  Au2S,  is  formed  as  a  dark-brown,  almost 
black  precipitate  when  hydrogen  sulphide  is  passed  into  a  boiling  solution 
of  auric  chloride.  It  forms  sulphur-salts  with  the  monosulphidcs  of  potas- 
sium and  sodium.  Auric  sulphide,  Au2S3,  is  precipitated  in  yellow  flocks 
when  hydrogen  sulphide  is  passed  into  a  cold  dilute  solution  of  auric 
chloride.  Both  these  sulphides  dissolve  in  ammonium  sulphide. 


The  presence  of  gold  in  solution  may  be  detected  by  the  brown  precipi- 
tate with  ferrous  sulphate,  fusible  before  the  blowpipe  to  a  bead  of  metallic 


GOLD.  371 

gold;  also  by  the  brownish-purple  precipitate,  called  "Purple  of  Cassius," 
formed  when  stannous  chloride  is  added  to  dilute  gold  solutions.  The  com- 
position of  this  precipitate  is  not  exactly  known,  but  after  ignition  it 
doubtless  consists  of  a  mixture  of  stannic  oxide  and  metallic  gold.*  It  is 
used  in  enamel  painting. 

Oxalic  acid  slowly  reduces  gold  to  the  metallic  state:  to  insure  complete 
precipitation,  the  gold-solution  must  be  digested  with  it  for  24  hours.  For 
the  quantitative  analysis  of  a  solution  containing  gold  and  other  metals, 
oxalic  acid  is  in  most  cases  a  more  convenient  precipitant  than  ferrous  sul- 
phate; inasmuch  as,  if  the  quantities  of  the  other  metals  are  also  to  be 
determined,  the  presence  of  a  large  quantity  of  iron  salt  may  complicate 
the  analysis  considerably. 

Gold  intended  for  coin,  and  most  other  purposes,  is  always  alloyed  with 
a  certain  proportion  of  silver  or  copper,  to  increase  its  hardness  and 
durability:  the  first-named  metal  confers  a  pale  greenish  color.  English 
standard  gold  contains  ^  of  alloy,  now  always  copper.  Gold  when  alloyed 
with  copper  may  be  estimated  by  fusion  in  a  cupel  with  lead,  in  the  same 
way  as  in  the  alloy  with  silver.  If  the  alloy  be  free  from  silver,  the  weight 
of  the  globule  of  gold  left  in  the  cupel  will,  after  repeated  fusions,  accu- 
rately represent  the  quantity  of  gold  which  is  present  in  the  alloy.  But 
if  the  alloy  contains  silver,  that  metal  remains  with  the  gold  after  cupella- 
tion.  In  this  case  the  original  alloy,  consisting  of  gold,  silver,  and  copper, 
is  fused  in  the  mutfle  together  with  lead  and  silver;  the  alloy  of  gold  and 
silver  remaining  after  cupellation  is  then  boiled  with  nitric  acid,  which 
dissolves  the  silver,  the  gold  being  left  behind.  By  treatment  of  the  alloy 
of  gold  and  silver  with  nitric  acid,  an  accurate  separation  is  obtained  only 
when  the  two  metals  are  present  in  certain  proportions.  If  the  alloy  con- 
tains but  little  silver,  that  metal  is  protected  from  the  action  of  the  nitric 
acid  by  the  gold ;  again,  if  it  contains  too  much  silver,  the  gold  is  left  as  a 
powder  when  the  silver  is  dissolved  out.  Experience  has  shown  that  the 
most  favorable  proportions  are  J  gold  to  f  silver ;  the  gold  is  then  left 
pure,  retaining  the  original  shape  of  the  alloy,  and  can  be  easily  dried  and 
weighed.  The  quantity  of  silver  which  is  added  to  the  alloy  must  there- 
fore vary  with  the  amount  of  gold  which  it  contains. 

Gold-leaf  is  made  by  rolling  out  plates  of  pure  gold  as  thin  as  possible, 
and  then  beating  them  between  folds  of  membrane  with  a  heavy  hammer, 
until  the  requisite  degree  or  tenuity  has  been  reached.  The  leaf  is  made 
to  adhere  to  wood,  &c.,  by  size  or  varnish. 

Gilding  on  copper  has  very  generally  been  performed  by  dipping  the 
articles  into  a  solution  of  mercury  nitrate,  and  then  shaking  them  with 
a  small  lump  of  a  soft  amalgam  of  gold  with  that  metal,  which  thus  be- 
comes spread  over  their  surfaces:  the  articles  are  subsequently  heated  to 
expel  the  mercury,  and  then  burnished.  Gilding  on  steel  is  done  either 
by  applying  a  solution  of  auric  chloride  in  ether,  or  by  roughening  the  sur- 
face of  the  metal,  heating  it,  and  applying  gold-leaf  with  a  burnisher. 
Gilding  by  electrolysis  —  an  elegant,  and  simple  method,  now  rapidly  super- 
ceding  many  of  the  others  —  has  already  been  noticed.  The  solution  usu- 
ally employed  is  obtained  by  dissolving  oxide  or  cyanide  of  gold  in  a  solu- 
tion of  potassium  cyanide. 


*  Graham's  Elements  of  Chemistry,  Am.  edit.  p.  466, 


CLASS  IV.  — TETRAD  METALS. 

GROUP   L  — PLATINUM    METALS. 


PLATINUM. 
Atomic  weight,  197-4.     Symbol,  Pt. 

"QLATINUM,  palladium,  rhodium,  iridium,  ruthenium,  and  osmium,  form 
a  group  of  metals,  allied  in  some  cases  by  properties  in  common,  and 
still  more  closely  by  their  natural  association.  Crude  platinum,  a  native 
alloy  of  platinum,  palladium,  rhodium,  iridium,  and  a  little  iron,  occurs 
in  grains  and  rolled  masses,  sometimes  of  tolerably  large  dimensions,  mixed 
with  gravel  and  transported  materials,  on  the  slope  of  the  Ural  mountains, 
in  Russia,  in  Brazil,  and  Ceylon,  and  in  a  few  other  places.  It  has  never 
been  seen  in  the  rock,  which,  however,  is  judged  from  the  accompanying 
materials  to  have  been  serpentine.  It  is  stated  to  be  always  present  in 
small  quantities  with  native  silver. 

From  this  substance  platinum  is  prepared  by  the  following  process :  The 
crude  metal  is  acted  upon  as  far  as  possible  by  nitro-muriatic  acid,  contain- 
ing an  excess  of  hydrochloric  acid  and  slightly  diluted  with  water,  in  order 
to  dissolve  as  small  a  quantity  of  iridium  as  possible:  to  the  deep  yellow- 
ish-red and  highly  acid  solution  thus  produced,  sal-ammoniac  is  added,  by 
which  nearly  the  whole  of  the  platinum  is  thrown  down  in  the  state  of  am- 
monium platinochloride.  This  substance,  washed  with  a  little  cold  water, 
dried,  and  heated  to  redness,  leaves  metallic  platinum  in  the  spongy  state. 
This  metal  cannot  be  fused  into  a  compact  mass  by  ordinary  furnace-heat, 
but  the  same  object  may  be  accomplished  by  taking  advantage  of  its  prop- 
erty of  welding,  like  iron,  at  a  high  temperature.  The  spongy  platinum 
is  made  into  a  thin  uniform  paste  with  water,  introduced  into  a  slightly 
conical  mould  of  brass,  and  subjected  to  a  graduated  pressure,  by  which 
the  water  is  squeezed  out,  and  the  mass  rendered  at  length  sufficiently  solid 
to  bear  handling.  It  is  then  dried,  very  carefully  heated  to  whiteness,  and 
hammered,  or  subjected  to  powerful  pressure.  If  this  operation  is  properly 
conducted,  the  platinum  will  then  be  in  a  state  to  bear  forging  into  a  bar, 
which  can  afterwards  be  rolled  into  plates,  or  drawn  into  wire,  at  pleasure. 

A  method  for  refining  platinum  has  lately  been  proposed  by  MM.  Deville 
and  Debray.*  It  consists  in  submitting  the  crude  metal  to  the  action  of  an 
intensely  high  temperature  in  a  crucible  of  lime.  The  apparatus  they  em- 
ploy is  as  follows:  The  lower  part  of  the  furnace  consists  of  a  piece  of 
lime,  hollowed  out  in  the  centre  to  the  depth  of  about  a  quarter  of  an  inch  ; 
a  small  notch  is  filed  at  one  side  of  this  basin,  through  which  the  metal 
is  introduced  and  poured  out.  A  cover  made  of  another  piece  of  lime  fits 
on  the  top  of  this  basin:  it  is  also  hollowed  to  a  small  extent,  and  has  a 
conical  perforation  at  the  top,  into  which  is  inserted  the  nozzle  of  an  oxy- 
hydrogen  blowpipe.  The  whole  arrangement  is  firmly  bound  with  iron 
wire.  To  use  the  apparatus,  the  stopcock  supplying  the  hydrogen  (or  coal 
gas)  is  opened  and  the  gas  lighted  at  the  notch  in  the  crucible:  the  oxygen 

*  Ann.  Chim.  Phys.  [3]  Ivi.  385. 

372 


PLATINUM.  373 

is  then  gradually  supplied ;  and  when  the  furnace  is  sufficiently  hot,  the 
metal  is  introduced  in  small  pieces  through  the  orifice.  By  this  arrange- 
ment as  much  as  50  pounds  of  platinum  and  more  may  be  fused  at  once. 
All  the  impurities  in  the  platinum,  except  the  iridium  and  rhodium,  are 
separated  in  this  manner :  the  gold  and  palladium  are  volatilized ;  the 
sulphur,  phosphorus,  arsenic,  and  osmium,  oxidized  and  volatilized  ;  and 
the  iron  and  copper  oxidized  and  absorbed  by  the  lime  of  the  crucible. 

Platinum  is  a  little  whiter  than  iron :  it  is  exceedingly  malleable  and 
ductile,  both  hot  and  cold,  and  is  very  infusible,  melting  only  before  the 
oxy-hydrogen  blowpipe,  or  in  the  powerful  blast-furnace  just  described. 
It  is  the  heaviest  substance  known,  its  specific  gravity  being  21-5.  Neither 
air,  moisture,  nor  the  ordinary  acids  attack  platinum  in  the  slightest  degree 
at  any  temperature :  hence  its  great  value  in  the  construction  of  chemical 
vessels.  It  is  dissolved  by  nitro-muriatic  acid,  and  superficially  oxidized 
by  fused  potassium  hydrate,  which  enters  into  combination  with  the  oxide. 

The  remarkable  property  of  the  spongy  metal  to  determine  the  union  of 
oxygen  and  hydrogen  has  been  already  noticed.  There  is  a  still  more 
curious  state  in  which  platinum  can  be  obtained  —  that  of  platinum-black, 
in  which  the  division  is  carried  much  further.  It  is  easily  prepared  by 
boiling  a  solution  of  platinic  chloride,  to  which  an  excess  of  sodium  car- 
bonate and  a  quantity  of  sugar  have  been  added,  until  the  precipitate 
formed  after  a  little  time  becomes  perfectly  black,  and  the  supernatant 
liquid  colorless.  The  black  powder  is  collected  on  a  filter,  washed  and  dried 
by  gentle  heat.  This  substance  appears  to  possess  the  property  of  con- 
densing gases,  more  especially  oxygen,  into  its  pores  to  a  very  great  extent ; 
when  placed  in  contact  with  a  solution  of  formic  acid,  it  converts  the  latter, 
with  copious  effervescence,  into  carbonic  acid ;  alcohol,  dropped  upon  the 
platinum-black,  becomes  changed  by  oxidation  to  acetic  acid,  the  rise  of 
temperature  being  often  sufficiently  great  to  cause  inflammation.  When 
exposed  to  a  red-heat,  the  black  substance  shrinks  in  volume,  assumes  the 
appearance  of  common  spongy  platinum,  and  loses  these  peculiarities,  which 
are  no  doubt  the  result  of  its  excessively  comminuted  state. 

Platinum  forms  two  series  of  compounds:  the  platinous  compounds,  in 
which  it  is  bivalent,  e.g.  Ptx/Cl2,  Pt/X0,  and  the  platinic  compounds,  in  which 
it  is  quadrivalent,  e.g.,  PtivCl4,  Pt"02,  &c. 

CHLORIDES. — The  dichloride,  or  Platinous  chloride,  Pt//Cl2,  is  produced 
when  platinic  chloride,  dried  and  powdered,  is  exposed  for  some  time  to 
heat  of  about  200°,  whereby  half  the  chlorine  is  expelled ;  also,  when  sul- 
phurous acid  gas  is  passed  into  a  solution  of  the  tetrachloride  until  the 
latter  ceases  to  give  a  precipitate  with  sal-ammoniac.  It  is  a-greenish-gray 
powder,  insoluble  in  water,  but  dissolved  by  hydrochloric  acid.  The  latter 
solution,  mixed  with  sal-ammoniac  or  potassium  chloride,  deposits  a  double 
salt  in  fine  red  prismatic  crystals,  containing,  in  the  last  case,  2KCl.PtCl2. 
The  corresponding  sodium-compound  is  very  soluble  and  difficult  to  crys- 
tallize. These  double  salts  are  called  platinoso-chlorides  or  chloroplalinites. 
Platinous  chloride  is  decomposed  by  heat  into  chlorine  and  metallic  platinum. 

The  tetrachloride,  or  Platinic  chloride,  Pt"Cl4,  is  always  formed  when 
platinum  is  dissolved  in  nitro-muriatic  acid.  The  acid  solution  yields,  on 
evaporation  to  dryness,  a  red  or  brown  residue,  deliquescent,  and  very 
soluble  both  in  water  and  in  alcohol;  the  aqueous  solution  has  a  pure 
orange-yellow  tint.  Platinic  chloride  unites  with  a  great  variety  of  metal- 
lic chlorides,  forming  double  salts  called  piatwo-chloridet  or  chloro-platinates  ; 
the  most  important  of  these  compounds  are  those  containing  the  metals  of 
the  alkalies  and  ammonium.  Potassium  platinochloride,  2KCl.PtCl4,  forms  a 
bright  yellow  crystalline  precipitate,  being  produced  whenever  solutions 
of  the  chlorides  of  platinum  and  of  potassium  are  mixed,  or  a  potassium 
32 


374  TETRAD    METALS. 

salt  mixed  with  a  little  hydrochloric  acid  is  added  to  platinum  tetrachloride. 
It  is  feebly  soluble  in  water,  still  less  soluble  in  dilute  alcohol,  and  is  de- 
composed with  some  difficulty  by  heat.  It  is  easily  reduced  by  hydrogen 
at  a  high  temperature,  yielding  a  mixture  of  potassium  chloride  and  plati- 
num-black: the  latter  substance  may  thus,  indeed,  be  very  easily  prepared. 
The  sodium-salt,  2NaCl.PtCl4.60H2,  is  very  soluble,  crystallizing  in  large, 
transparent,  yellow-red  prisms  of  great  beauty.  The  ammonium-salt,  2NH4 
Cl.PtCl4.  is  undistinguishable,  in  physical  characters,  from  the  potassium- 
salt;  it  is  thrown  down  as  a  precipitate  of  small,  transparent,  yellow,  octo- 
hedral  crystals  when  sal-ammoniac  is  mixed  with  platinic  chloride ;  it  is 
but  feebly  soluble  in  water,  still  less  so  in  dilute  alcohol,  and  is  decomposed 
by  heat,  yielding  spongy  platinum,  while  sal-ammoniac,  hydrochloric  acid, 
and  nitrogen  are  driven  off.  Platinic  chloride  also  forms  crystallizable 
double  salts  with  the  hydrochlorides  of  many  organic  bases;  with  ethy la- 
mine,  for  example,  the  compound,  2[NH2(C2H5)HCl].PtCl4. 

The  bromides  and  iodides  of  platinum  are  analogous  in  composition  to  the 
chlorides,  and  likewise  form  double  salts  with  alkaline  bromides  and  iodides. 

OXIDES.  —  The  monoxide,  or  Platinous  oxide,  Pt/X0,  is  obtained  by  digesting 
the  dichloride  with  caustic  potash,  as  a  black  powder,  soluble  in  excess  of 
alkali.  It  dissolves  also  in  acids  with  brown  color,  and  the  solutions  are 
not  precipitated  by  sal-ammoniac.  When  platinum  dioxide  is  heated  with 
solution  of  oxalic  acid,  it  is  reduced  to  monoxide,  which  remains  dissolved. 
The  liquid  has  a  dark-blue  color,  and  deposits  fine  copper-red  needles  of 
platinous  oxalate. 

The  dioxide,  or  Platinic  oxide,  Pt"02,  is  best  prepared  by  adding  barium 
nitrate  to  a  solution  of  platinic  sulphate  ;  barium  sulphate  and  platinic 
nitrate  are  then  produced,  and  from  the  latter  caustic  soda  precipitates 
one  half  of  the  platinum  as  platinic  hydrate.  The  sulphate  is  itself  obtained 
by  acting  with  strong  nitric  acid  upon  platinum  bisulphide,  which  falls  as 
a  black  powder  when  a  solution  of  the  tetrachloride  is  dropped  into  potas- 
sium sulphide.  Platinic  hydrate  is  a  bulky  brown  powder,  which,  when 
gently  heated,  becomes  black  and  anhydrous.  It  may  also  be  formed  by 
boiling  platinic  chloride  with  a  great  excess  of  caustic  soda,  and  then  adding 
acetic  acid.  It  dissolves  in  acids,  and  also  combines  with  bases :  the  salts 
have  a  yellow  or  red  tint,  and  a  great  disposition  to  unite  with  salts  of  the 
alkalies  and  alkaline  earths,  giving  rise  to  a  series  of  double  compounds, 
which  are  not  precipitated  by  excess  of  alkali.  A  combination  of  platinic 
oxide  with  ammonia  exists,  which  is  explosive.  Both  oxides  of  platinum 
are  reduced  to  the  metallic  state  by  ignition. 

SULPHIDES.  —  The  compounds  Ptr/S  and  PtivS2  are  produced  by  the  action 
of  hydrogen  sulphide,  or  the  sulph-hydrate  of  an  alkali-metal,  on  the  di- 
chloride and  tetrachloride  of  platinum  respectively ;  they  are  both  black 
substances,  insoluble  in  water.  Platinic  sulphide  heated  in  a  close  vessel 
gives  off  half  its  sulphur  and  is  reduced  to  platinous  sulphide.  It  dissolves 
in  alkaline  hydrates,  carbonates,  and  sulphides,  forming  salts  called  sulpho- 
platinates,  which  are  decomposed  by  acids. 

A.mmoniacal  Platinum  Compounds. 

The  chlorides,  oxides,  sulphates,  &c.,  of  platinum  are  capable  of  taking 
up  two  or  more  molecules  of  ammonia,  and  forming  compounds  analogous 
in  many  respects  to  the  ammoniacal  mercury  compounds  already  described. 
There  are  five  series  of  these  compounds,  which  may  be  formulated  as  in 
the  following  table,  the  symbol  K-  denoting  a  univalent  chlorous  radical 
such  as  Cl,  Br,  N03,  &c. 


PLATINUM.  375 

I.  Diammonio-platinous  compounds        .  2NH3.Pt//R2. 

II.  Tetrammonio-platinous  compounds    .  4NH3.Pt//R2. 

III.  Diarnmonio-platinic  compounds  .  2NH3.  PtiTR4. 

IV.  Tetrammonio-platinic  compounds       .  4NH3.  PtiTR4. 

V.  Octarnnionio-diplatinic  compounds      .  8NH3.  Pt'T2R60//. 

Any  number  of  atoms  of  the  univalent  radical  R  may  be  replaced  in  these 
compounds  by  an  equivalent  quantity  of  another  radical,  univalent  or  multi- 
valent,  thus  giving  rise  to  oxychlorides,  nitrato-chlorides,  oxynitrates,  &c. 

The  diammonio-platinous  and  tetrammonio-platinic  compounds  (I.  and  IV.) 
may  evidently  be  derived  from  double  and  quadruple  molecules  of  am- 
monium salts,  by  the  substitution  of  Ptx/  or  Ptiv  for  an  equivalent  quantity 
of  hydrogen:  e.g.,  2NH3.Pt"Cl2=(N2H6Pt").Cl2;  and  4NH3.PtiTCl4=(N4 
H12Ptiv).Cl4.  The  composition  of  the  tetrammonio-platinous  compounds  (II.) 
will  be  understood  when  it  is  remembered  that,  nitrogen  being  a  pentad 
element,  NH3,  is  a  bivalent  radical,  and  that  any  number  of  such  radicals 
may  be  added  to  a  compound  without  disturbing  the  balance  of  equivalency 
(pp.  234,  235).  Further,  since  the  addition  of  NH3  to  any  compound  con- 
taining hydrogen  comes  to  the  same  thing  as  replacing  an  atom  of  hydrogen 
in  that  compound  by  ammonium,  NH4,  these  tetrammonio-platinous  com- 
pounds may  also  be  regarded  as  salts  of  diammoplatoso-diammonium,  that  is, 
of  a  double  ammonium  molecule,  N2E8,  in  which  two  atoms  of  hydrogen 
are  replaced  by  Pt/x,  and  two  more  by  (NH4)2.  —  In  the  diammonio-platinic 
compounds  (III.),  the  bivalent  radical  (Pt^CLj)'7  plays  the  same  part  as  Ptx/ 
in  the  diammonio-platinous  compounds. 

The  following  table  exhibits  the  constitution  of  the  several  groups  of 
compounds  according  to  these  views,  taking  the  chlorides  as  examples: 

NH3C1 
I.    2NH3.PtCl2      =  (N2H6Pt")Cla  =  Pt 

NH3C1 
NH3C1 
NH3 

II.  4NH3.Pt"Cl2  =  [N2H4(NH4)2Pt"]Cl2    =  Pt 

NH3 

NH3C1 
NH3C1 

III.  2NH3.Pt*Cl4  =  [N2H6(Pt"Cl2)"]Cl2      =  PtCl2 

NH3C1 

N2II6C12 
I! 

IV.  4NH8.PtiTCl4  =  (N4H12PtlT)Cl4 

N2H6C12. 

V.  The  octammonio-diplatinic  compounds  consist  of  double  molecules  of 
tetrammonio-platinic  compounds  having  two  or  more  molecules  of  the  uni- 


376  TETRAD    METALS. 

valent  radical  R,  replaced  by  an  equivalent  quantity  of  a  bivalent  radical : 
e.  ff.,  the  oxynitrate  =  8NH3.Pt*2(N03)6O"  =  (N8HMPt*2)  j  (^s)«. 

I.  Diammonio-platinous  Compounds.  —  These  compounds  are  formed  by  the 
action  of  heat  on  those  of  the  following  series,  half  the  ammonia  of  the 
latter  being  then  given  off.  They  are  for  the  most  part  insoluble  in  water, 
but  dissolve  in  ammonia,  reproducing  the  tetrammonio-platinous  com- 
pounds: they  detonate  when  heated. 

Chloride,  NgHgPf'Cl.j.  —  Of  this  compound  there  are  three  isomeric  mod- 
ifications:—  a.  Fellow,  obtained  by  adding  hydrochloric  acid,  or  a  soluble 
chloride,  to  a  solution  of  diamrnonio-platinous  nitrate  or  sulphate,  or  by 
boiling  the  green  modification,  y,  with  ammonium  nitrate  or  sulphate;  or, 
by  neutralizing  a  solution  of  platinous  chloride  in  hydrochloric  acid  with 
ammonium  carbonate,  heating  the  mixture  to  the  boiling  point,  and  adding 
a  quantity  of  ammonia  equal  to  that  already  contained  in  the  liquid,  filter- 
ing from  a  dingy  green  substance,  which  deposits  after  a  while,  then  leav- 
ing the  solution  to  cool,  and  decanting  the  supernatant  liquid  as  soon  as 
the  yellow  salt  is  deposited.  (3.  Red. — If,  in  the  last  mode  of  preparation, 
the  ammonium  carbonate,  instead  of  being  added  at  once  in  excess,  be 
added  drop  by  drop  to  the  hydrochloric  acid  solution  of  platinous  chloride, 
the  liquid  on  cooling  deposits  small  garnet- colored  crystals  having  the  form 
of  six-sided  tables.  This  red  modification  may  also  be  obtained  in  other 
ways.  y.  Green.  —  This  modification,  usually  denominated  the  green  salt  of 
Magnus,  was  the  first  discovered  of  the  ammoniacal  platinum  compounds. 
It  is  obtained  by  gradually  adding  an  acid  solution  of  platinous  chloride  to 
caustic  ammonia;  or  by  passing  sulphurous  acid  gas  into  a  boiling  solution 
of  platinic  chloride,  till  it  is  completely  converted  into  platinous  chloride 
(and  therefore  no  longer  gives  a  precipitate  with  sal-ammoniac),  and  neu- 
tralizing the  solution  with  ammonia;  the  compound  is  then  deposited  in 
green  needles.  The  same  modification  of  the  salt  may  also  be  obtained  by 
adding  an  acid  solution  of  platinous  chloride  to  a  solution  of  tetrammonio- 
platinous  chloride,  N4H12Pt//Cl2.  The  corresponding  iodide,  N2H6Ptx/I2,  is 
a  yellow  powder,  obtained  by  heating  the  aqueous  solution  of  the  compound, 
N4Hl2Pt//I2.  It  dissolves  in  ammonia,  reproducing  the  latter  compound. 
The  oxide,  N2H6Pt//0,  obtained  by  heating  tetrammonio-platinous  hydrate 
to  110°,  is  a  grayish  mass,  which,  when  heated  to  100°  in  a  close  vessel, 
gives  off  water,  ammonia,  and  nitrogen,  and  leaves  metallic  platinum.  The 
sulphate,  N2H6Pt//S04.OH2,  and  the  nitrate,  N2H6Pt//(N03)2,  are  obtained  by 
boiling  the  iodide  with  sulphate  and  nitrate  of  silver:  they  are  crystalline 
and  have  a  strong  acid  reaction.  The  sulphate  retains  a  molecule  of  crys- 
tallization-water, which  cannot  be  removed  without  decomposing  the  salt. 

II  Tetrammonio-platinous  Compounds.  —  The  chloride,  N4Hl2Pt//Cl2,  is  pre- 
pared by  boiling  platinous  chloride,  or  the  green  salt  of  Magnus,  with 
aqueous  ammonia  till  the  whole  is  dissolved,  and  evaporating  the  liquid  to 
the  crystallizing  point.  The  bromide  and  iodide  of  this  series  are  obtained 
by  treating  the  solution  of  the  sulphate  with  bromide  or  iodide  of  barium : 
they  crystallize  in  cubes.  The  oxide,  N4H12Pt//0,  is  obtained  as  a  crystal- 
line mass  by  decomposing  the  solution  of  the  sulphate  with  an  equivalent 
quantity  of  baryta-water,  and  evaporating  the  filtrate  in  a  vacmim.  It  is 
strongly  alkaline  and  caustic,  like  potash,  absorbs  carbonic  acid  rapidly 
from  the  air,  and  precipitates  silver  oxide  from  the  solution  of  the  nitrate. 
It  is  a  strong  base,  neutralizing  acids  completely,  and  expelling  ammonia 
from  its  salts.  It  melts  at  110°,  giving  off  water  and  ammonia,  and  leav- 
ing diammonio-platinous  oxide.  Its  aqueous  solution  does  not  give  off 
ammonia,  even  when  boiled. 

Carbonates. — The  oxide  absorbs  carbon  dioxide  rapidly  from  the  air, 
forming  first  a  neutral  carbonate,  N4H,2Pt//C03.OH2,  and  afterwards  an. 


PLATINUM.  377 

acid  salt,  N4H,2Pt"COs.C03H2.  The  sulphate,  N4H12Pt"S04,  and  the  nitrate, 
N4H,2Pt//(N03)2,  are  obtained  by  decomposing  the  chloride  with  silver  sul- 
phate or  nitrate ;  they  are  neutral,  and  crystallize  easily. 

III.  Diammonio-platinic  Compounds. — The  chloride,  N2H6Pt'TCl4,  is  obtained 
by  passing  chlorine  gas  into  boiling  water  in  which  diammoriio-platinous 
chloride  (the  yellow  modification)  is  suspended.     This  compound  is  insolu- 
ble in  cold  water,  and  very  slightly  soluble  in  boiling  water,  or  in  water 
containing  hydrochloric  acid.     It  dissolves  in  ammonia  at  a  boiling  heat, 
and  the  solution,  on  cooling,  deposits  a  yellow  precipitate,  consisting  of 
tetnimmoriiacal  platinic  chloride.     It  dissolves  in  boiling  potash  without 
evolving  ammonia. 

Nitrates.— An  oxynitrate,  N2H6PtlT(NOs)20",  is  obtained  by  boiling  the 
chloride,  N2H6PtCl4,  for  several  hours  with  a  dilute  solution  of  silver  nitrate. 
It  is  a  yellow  crystalline  powder,  sparingly  soluble  in  cold,  more  soluble  in 
boiling  water.  The  normal  nitrate,  N2II6PtiT(N03)4,  is  obtained  by  dissolving 
the  oxynitrate  in  nitric  acid:  it  is  yellowish,  insoluble  in  cold  water,  solu- 
ble in  hot  nitric  acid. 

The  oxide,  N2H6Ptiv02,  is  obtained  by  adding  ammonia  to  a  boiling  solu- 
tion of  diammonio-platinic  nitrate ;  it  is  then  precipitated  in  the  form  of  a 
heavy  yellowish,  crystalline  powder,  composed  of  small  shining  rhomboi'dal 
prisms;  it  is  nearly  insoluble  in  boiling  water,  and  resists  the  action  of 
boiling  potash.  Heated  in  a  close  vessel,  it  gives  off  water  and  ammonia, 
and  leaves  metallic  platinum.  It  dissolves  readily  in  dilute  acids,  even  in 
acetic  acid,  and  forms  a  large  number  of  crystallizable  salts,  both  neutral 
and  acid,  having  a  yellow  color,  and  sparingly  soluble  in  water.*  Another 
compound  of  platinic  oxide  with  ammonia,  called  fulminating  platinum,  whose 
composition  has  not  been  exactly  ascertained,  is  produced  by  decomposing 
ammonium  platino-chloride  with  aqueous  potash.  It  is  a  straw-colored 
powder,  which  detonates  slightly  when  suddenly  heated,  but  strongly  when 
exposed  to  a  gradually  increasing  heat. 

IV.  Tetrammonio-platinic  Compounds. — The  oxide  of  this  series  has  not  yet 
been  isolated.      The  chloride,  N4Hl2PtivCl4,  is  obtained  by  passing  chlorine 
gas  into  a  solution  of  tetrarnmonio-platinous  chloride ;  by  dissolving  diam- 
monio-platinic chloride  in  ammonia,  and  expelling  the  excess  of  ammonia 
by  evaporation ;    or  by  precipitating  a   solution  of  tetrammonio-platinic 
.oxynitrate  or  nitrato-chloride  with  hydrochloric  acid.     It  is  white,  and  dis- 
solves in  small  quantity  in  boiling  water,  from  which  solution  it  is  deposited 
in  the  form  of  transparent  regular  octohedrons,  having  a  faint  yellow  tint. 
When  a  solution  of  this  salt  is  treated  with  silver  nitrate,  one-half  of  the 
chlorine  is  very  easily  precipitated,  but  to  remove  even  a  small  portion  of 
the  remainder  requires  a  long-continued  action  of  the  silver-salt.     The 
cklorobromide,  N4Hl2PtlTBr2Cl2,  is  prepared  by  treating  tetrammonio-platinous 
chloride  with  bromine.     An  oxynitrate,  N4H,2PtiT(N03)20 ;  a  nitrato-chloride, 
NjHpPWNO^Cl,;    a  MtlphQto-chloride,  N2Hl2PtlT(S04)"Cla;  and  an  oxalo- 
chlvrtde,  ^4H12i'ti  (C204)"Cla,  have  likewise  been  obtained. 

V.  Octammonio-diplatinic  Compounds.     An  oxynitrate  or  basic  nitrate,  NgH.^ 
Ptiv2(NO3)6O//,  is  produced  by  boiling  tetrammonio-platinous  nitrate  with 
nitric  acid.     It  is  a  colorless,  crystalline,  detonating  salt,  slightly  soluble 
in   cold   water,   more   soluble  in  boiling   water,   insoluble  in  nitric   acid. 
(Gerhardt.)     A    nitrat-oxychloride,    NgH24PtlT2(N08)4p"Cl2,    discovered   by 
Kaewsky,  is  formed  when  Magnus's  green  salt  is  boiled  with  a  large  excess 
of  nitric  acid,     lied  fumes  are  then  evolved,  and  the  resulting  solution  de- 

*  Gerhardt,  Comtes  n-nclus  des  travaux  en  Chimie,  1849,  p.  273. 
32  * 


378  TETRAD    METALS. 

posits  the  nitrat-oxychloride  in  small  brilliant  needles,  which  deflagrate 
when  heated,  giving  oft'  water  and  sal-aminoniac,  and  leaving  metallic 
platinum.  The  nitric  acid  in  this  salt  may  be  replaced  by  an  equivalent 
quantity  of  carbonic  or  oxalic  acid,  yielding  the  compounds,  N8H24Pir2(C03)// 
20"C12,  and  N8H24PtiT2(C204)"20"G12>  both  of  which  are  crystallizable  and 
sparingly  soluble.  A  basic  oxalo-nitrate,  N8H24Ptiv2(C204)//2(K03)20//,  insolu- 
ble in  water,  is  obtained  by  adding  ammonium  oxalate  to  the  oxynitratet 
(Gerhardt.) 

Reactions  of  Platinum  Salts. — Platinic  chloride  or  a  platinic  oxygen-salt 
may  be  recognized  in  solution  by  the  yellow  precipitate  with  sal-ammoniac, 
decomposable  by  heat,  with  production  of  spongy  metal. 

Hydrogen  sulphide  and  ammonium  sulphide  gradually  form  a  brown  precipi- 
tate of  platinic  sulphide,  soluble  in  excess  of  ammonium  sulphide.  Zinc 
precipitates  metallic  platinum. 

Platinic  chloride  and  sodium  platinochloride  are  employed  in  analytical 
investigations  to  detect  the  presence  of  potassium,  and  separate  it  from 
sodium.  For  the  latter  purpose,  the  alkaline  salts  are  converted  into 
chlorides,  and  in  this  state  mixed  with  four  times  their  weight  of  sodium 
platinochloride  in  crystals,  the  whole  being  dissolved  in  a  little  water. 
When  the  formation  of  the  yellow  salt  appears  complete,  alcohol  is  added, 
and  the  precipitate  collected  on  a  weighed  filter,  washed  with  weak  spirit, 
carefully  dried,  and  weighed.  The  potassium  chloride  is  then  easily  reck- 
oned from  the  weight  of  the  double  salt ;  and  this,  subtracted  from  the 
weight  of  the  mixed  chlorides  employed,  gives  that  of  the  sodium  chloride 
by  difference ;  100  parts  of  potassium  platinochloride  correspond  to  30-51 
parts  of  potassium  chloride. 

Capsules  and  crucibles  of  platinum  are  of  great  value  to  the  chemist: 
the  latter  are  constantly  used  in  mineral  analysis  for  fusing  siliceous  matter 
with  alkaline  carbonates.  -They  suffer  no  injury  in  this  operation,  although 
caustic  alkali  roughens  and  corrodes  the  metal.  The  experimenter  must 
be  particularly  careful  to  avoid  introducing  any  oxide  of  an  easily  fusible 
metal,  as  that  of  lead  or  tin,  into  a  platinum  crucible.  If  reduction  should 
by  any  means  occur,  these  metals  will  at  once  alloy  themselves  with  the 
platinum,  and  the  vessel  will  be  destroyed.  A  platinum  crucible  must  never 
be  put  naked  into  a  coke  or  charcoal  fire,  but  always  placed  within  a  covered 
earthen  crucible. 


PALLADIUM. 

Atomic  weight,  106-5.     Symbol,  Pd. 

When  the  solution  of  crude  platinum,  from  which  the  greater  part  of  that 
metal  has  been  precipitated  by  sal-ammoniac,  is  neutralized  by  sodium  car- 
bonate, and  mixed  with  a  solution  of  mercuric  cyanide,  palladium  cyanide 
separates  as  a  whitish  insoluble  substance,  which,  on  being  washed,  dried, 
and  heated  to  redness,  yields  metallic  palladium  in  a  spongy  state.  The 
palladium  may  then  be  welded  into  a  mass,  in  the  same  manner  as  platinum. 

Palladium  closely  corresponds  with  platinum  in  color  and  appearance ; 
it  is  also  very  malleable  and  ductile.  Its  density  differs  very  much  from 
that  of  platinum,  being  only  11-8.  Palladium  is  more  oxidable  than  plati- 
num. When  heated  to  redness  in  the  air,  especially  in  the  state  of  sponge, 
it  acquires  a  blue  or  purple  superficial  film  of  oxide,  which  is  again  reduced 
at  a  white  heat.  This  metal  is  slowly  attacked  by  nitric  acid;  its  best 
solvent  is  nitro-muriatic  acid. 


PALLADIUM.  379 

Palladium,  like  platinum,  forms  two  classes  of  compounds ;  namely,  the 
palladious  compounds,  in  which  it  is  bivalent,  and  the  palladic  compounds,  in 
which  it  is  quadrivalent. 

CHLORIDES.  —  The  dichloride,  or  Palladious  chloride,  Pdx/Cl2,  is  obtained 
by  dissolving  the  metal  in  nitro-muriatic  acid,  and  evaporating  the  solution 
to  dryness.  It  is  a  dark-brown  mass,  which  dissolves  in  water  if  the  heat 
has  not  been  too  great,  arid  forms  double  salts  with  many  metallic  chlorides. 
The  palladio-chlorides  of  ammonium  and  potassium  are  much  more  soluble 
than  the  corresponding  platino-chlorides  :  they  have  a  brownish-yellow  tint. 

The  tetrachloride,  or  Palladic  chloride,  PdivCl4,  exists  only  in  solution  and 
in  combination  with  the  alkaline  chlorides.  It  is  formed  when  the  dichlor- 
ide is  digested  in  nitro-muriatic  acid.  The  solution  has  an  intense  brown 
color,  and  is  decomposed  by  evaporation.  Mixed  with  potassium  chloride, 
or  sal-ammoniac,  it  gives  rise  to  a  red  crystalline  precipitate,  which  is  but 
little  soluble  in  water. 

PALLADIOUS  IODIDE,  Pdx/I2,  is  precipitated  from  the  chloride  or  nitrate 
by  soluble  iodides,  as  a  black  mass,  which  gives  off  its  iodine  between  300° 
and  360°  C.  (572°  and  680°  F.)  Palladium-salts  are  employed  for  the  quan- 
titative estimation  of  iodine,  chlorine  and  bromine  not  being  precipitated 
by  them. 

OXIDES.  —  The  monoxide,  or  Palladious  oxide,  Pdx/0,  is  obtained  by  evapo- 
rating to  dryness,  and  cautiously  heating,  the  solution  of  palladium,  in  nitric 
acid.  It  is  black,  and  but  little  soluble  in  acids.  The  hydrate  falls  as  a 
dark-brown  precipitate  when  sodium  carbonate  is  added  to  the  above  solu- 
tion. It  is  decomposed  by  a  strong  heat. 

The  dioxide,  or  Palladic  oxide,  Pdiv02,  is  not  known  in  the  separate  state. 
From  a  solution  of  palladic  chloride,  alkalies  and  alkaline  carbonates  throw 
down  a  brown  precipitate  consisting  of  hydrated  palladic  oxide  combined 
with  the  alkali.  This  compound  gives  off  half  its  oxygen  at  a  moderate 
heat,  and  the  whole  at  a  higher  temperature.  From  hot  solutions,  a  black 
precipitate  is  obtained  containing  the  anhydrous  dioxide.  The  hydrate  dis- 
solves slowly  in  acids,  forming  yellow  solutions.  In  strong  hydrochloric 
acid  it  dissolves  without  decomposition,  forming potansio-palladic  chloride,  aris- 
ing from  admixed  potash ;  with  dilute  hydrochloric  acid,  on  the  contrary, 
it  gives  off  chloride. 

PALLADIOUS  SULPHIDE,  Pd/xS,  is  formed  by  fusing  the  metal  with  sulphur, 
or  by  precipitating  a  solution  of  a  palladious  salt  with  hydrogen  sulphide. 
It  is  insoluble  in  ammonium  sulphide. 

AMMONIAC AL  PALLADIUM  COMPOUNDS. — A  moderately  concentrated  solu- 
tion of  palladium  dichloride  treated  with  a  slight  excess  of  ammonia,  yields  a 
beautiful  flesh-colored  or  rose-colored  precipitate,  consisting  of  N2H6Pd//Cl2. 
This  precipitate  dissolves  in  a  larger  excess  of  ammonia ;  and  the  ammonia- 
cal  solution,  when  treated  with  acids,  yields  a  yellow  precipitate  having  the 
same  composition.  This  yellow  modification  is  likewise  obtained  by  heating 
the  red  compound  in  the  moist  state  to  100°,  or  in  the  dry  state  to  200°  C. 
(392°  F.)  The  yellow  compound  dissolves  abundantly  in  aqueous  potash, 
forming  a  yellow  solution,  but  without  giving  off  ammonia,  even  when  the 
liquid  is  heated  to  the  boiling-point;  the  red  compound  behaves  in  a  simi- 
lar manner,  but,  before  dissolving,  is  converted  into  the  yellow  modification. 
For  this  reason,  Hugo  Miiller  regards  the  red  compound  as  palladium  innnio- 
nio-chloride,  2NH3.Pd//CI2,  and  the  yellow  as  palladammomum  chloride, 
N2H6IM"C12.  The  yellow  compound,  digested  with  water  and  silver  oxide, 
yields  palladammonium  oxide,  N2H6Pd//0,  which  is  a  strong  base,  soluble  in 


380  TETRAD    METALS. 

water,  having  an  alkaline  taste  and  reaction,  and  absorbing  carbonic  acid 
from  the  air.  Palladammonium  sulphite,  N2H6Pd//.S03,  is  formed  by  the 
action  of  sulphurous  acid  on  the  oxide  or  chloride  ;  it  crystallizes  in  orange- 
yellow  octohedrons.  The  sulphite,  chloride,  iodide,  and  bromide,  have  likewise 
been  formed. 

The  compound,  4NH3.Pd//Cl2,  or  ammopalladammonium  chloride,  [N2H4Pdx/ 
(NH4)2]//C12,  separates  from  an  ammoiiiacal  solution  of  palladammonium 
chloride  in  oblique  rhombic  prisms. 

The  oxide,  N4H,2Pd//0,  obtained  by  decomposing  the  solution  of  this  chlor- 
ide with  silver  oxide,  is  also  a  strong  base  yielding  crystallizable  salts.* 

Palladious  salts  are  well  marked  by  the  pale  yellowish- white  precipitate 
with  solution  of  mercuric  cyanide.  It  consists  of  palladious  cyanide, 
Pdx/Cy2,  and  is  converted  by  heat  into  the  spongy  metal. 

Hydriodic  acid  and  potassium  iodide  throw  down  a  black  precipitate  of 
palladium  iodide,  visible  even  to  the  500,000th  degree  of  dilution. 

Palladium  is  readily  alloyed  with  other  metals,  as  copper ;  one  of  these 
compounds  —  namely,  the  alloy  with  silver  —  has  been  applied  to  useful 
purposes.  An  amalgam  of  palladium  is  now  extensively  used  by  dentists 
for  stopping  teeth. 

A  native  alloy  of  gold  with  palladium  is  found  in  Brazil. 


RHODIUM. 
Atomic  weight,  104.     Symbol,  Rh. 

The  solution  from  which  platinum  and  palladium  have  been  separated,  in 
the  manner  already  described,  is  mixed  with  hydrochloric  acid,  and  evap- 
orated to  dryness.  The  residue  is  treated  with  alcohol  of  specific  gravity 
0-8?7,  which  dissolves  everything  except  the  double  chloride  of  rhodium 
and  sodium.  This  is  well  washed  with  spirit,  dried,  heated  to  whiteness, 
and  then  boiled  with  water,  whereby  sodium  chloride  is  dissolved  out,  and 
metallic  rhodium  remains.  Thus  obtained,  rhodium  is  a  white,  coherent, 
spongy  mass,  more  infusible  and  less  capable  of  being  welded  than  plati- 
num. Its  specific  gravity  varies  from  10-6  to  11. 

Rhodium  is  very  brittle :  reduced  to  powder  and  heated  in  the  air,  it  be- 
comes oxidized,  and  the  same  alteration  happens  to  a  greater  extent  when 
it  is  fused  with  nitrate  or  bisulphate  of  potassium.  None  of  the  acids, 
singly  or  conjoined,  dissolve  this  metal,  unless  it  be  in  the  state  of  alloy, 
as  with  platinum,  in  which  state  it  is  attacked  by  nitro-muriatic  acid. 

Rhodium  forms  but  one  chloride,  containing  RhCl3:  hence  it  might  be 
supposed  to  be  a  triad;  but,  from  its  analogy  to  the  other  platinum  metals, 
it  is  generally  regarded  as  a  tetrad,  the  chloride  just  mentioned  being 

RhCl3 
represented  by  the  formula  Rh2Cl6,  or  I 

RhCl3 

This  chloride  is  prepared  by  adding  silicofluoric  acid  to  the  double 
chloride  of  rhodium  and  potassium,  evaporating  the  filtered  solution  to 
dryness,  and  dissolving  the  residue  in  water.  It  forms  a  brownish-red  deli- 
quescent mass,  soluble  in  water,  with  a  fine  red  color.  It  is  decomposed 
by  heat  into  chlorine  and  metallic  rhodium. 

Rhodium  and  Potassium  chlorides.  —  The  salt,  Rh2Cl6.6KC1.60H2,  formed  by 


*  Hugo  Milller,  Ann.  Ch.  Pharm.  Ixxxvi.  341. 


RHODIUM.  381 

mixing  a  solution  of  rhodic  oxide  in  hydrochloric  acid  with  a  strong  solu- 
tion of  potassium  chloride,  crystallizes  in  sparingly  soluble  efflorescent 
prisms.  Another  double  salt  containing  RhaCl6.4KCl.'JOH8,  is  prepared  by 
heating  in  a  stream  of  chlorine  a  mixture  of  equal  parts  ot  finely  powdered 
metallic  rhodium  and  potassium  chloride.  The  salt  has  a  fine  red  color,  is 
soluble  in  water,  and  crystallizes  in  four-sided  prisms  Rhodium  and  sodium 
chloride,  Rh2Cl6.6NaC1.240H2,  is  also  a  very  beautiful  red  salt,  prepared 
like  the  last.  The  ammonium  salt,  Bh2016.  6NH4C1.  30H2,  obtained  by  de- 
composing the  sodium  salt  with  sal-ammoniac,  crystallizes  in  fine  rhombo- 
hedral  prisms. 

RHODIUM  OXIDES. — Rhodium  forms  four  oxides,  containing  RhO,  Rh203, 
Rh02,  and  Rh03. 

The  monoxide,  RhO,  is  formed,  with  incandescence,  when  the  hydrated 
sesquioxide,  Rh203.30H2,  is  heated  in  a  platinum  crucible.  It  is  a  dark- 
gray  substance,  perfectly  indifferent  to  acids. 

The  sesquioxide  or  rhodic  oxide,  Rh203,  obtained  by  heating  the  nitrate,  is 
a  gray  porous  mass,  with  metallic  iridescence ;  insoluble  in  acids,  easily 
reduced  by  hydrogen.  It  forms  two  hydrates  :  Rh203.30H2,  or  RhH3O3, 
obtained  by  precipitating  a  solution  of  rhodium  and  sodium  chloride  with 
potash  in  presence  of  alcohol,  and  Rh203.50H2  or  RhH303.OH2,  formed  by 
precipitating  the  same  salt  with  aqueous  potash. 

The  dioxide,  Rh02,  obtained  by  fusing  pulverized  rhodium  or  the  sesqui- 
oxide with  nitre  and  potash,  and  digesting  the  fused  mass  with  nitric  acid, 
to  dissolve  off  the  potash,  is  a  dark-brown  substance,  insoluble  in  acids. 
When  chlorine  is  passed  into  a  solution  of  rhodic  pentahydrate,  Rh203.50H2, 
a  black-brown  gelatinous  precipitate  of  the  trihydrate,  Rh208.30H2,  is 
formed  at  first;  but  this  compound  gradually  loses  its  gelatinous  consistence, 
becomes  lighter  in  color,  and  is  finally  converted  into  a  green  hydrate  of 
the  dioxide,  Rh02.20H2.  The  alkaline  solution  at  the  same  time  acquires 
a  deep  violet-blue  color. 

Trioxide,  Rh03.  —  The  blue  alkaline  solution  above  mentioned,  deposits, 
after  a  while,  a  blue  powder,  becoming  green  when  dry,  and  yielding,  when 
treated  with  nitric  acid,  a  blue  flocculent  substance,  consisting  of  the  tri- 
oxide,  easily  reduced  to  the  dioxide. 

RHODIC  SULPHATE,  (S04)3Rh2.120H2,  formed  by  oxidizing  the  sulphide 
with  nitric  acid,  is  a  yellowish-white  crystalline  mass.  Potassio-rhodic  sul- 
phate, (S04)3RhK3,  is  a  reddish-yellow  crystalline  powder  formed  by  adding 
sulphuric  acid  to  a  solution  of  rhodium  and  potassium  chloride. 

AMMONIACAL  RHODIUM  COMPOUNDS. — An  ammonio-chloride,  10NH3.Rh2Cl6, 
or  [N6H,4Rh///2(NH4)4]viCl6,  is  obtained  as  a  yellow  crystalline  powder  on 
mixing  a  dilute  solution  of  rhodium  and  ammonium  chloride  with  excess  of 
ammonia,  and  leaving  the  filtered  solution  to  evaporate.  The  corresponding 
oxide,  10NH3.Rh203,  obtained  by  heating  the  chloride  with  silver  oxide,  is 
a  strong  base,  from  which  the  sulphate  and  oxalate  may  be  obtained  in 
crystalline  form. 


Rhodic  salts  are,  for  the  most  part,  rose-colored,  and  exhibit,  in  solution, 
the  following  reactions:  with  hi/dror/en  sulphide,  and  ammonium  sulphide,  a 
brown  precipitate  of  rhodic  sulphide,  insoluble  in  excess  of  ammonium 
sulphide:  with  soluble  sulphites,  a  pale-yellow  precipitate,  affording  a  char- 
acteristic reaction;  with  potash,  a  yellow  precipitate  of  rhodic  oxide,  solu- 
ble in  excess;  with  ammonia  and  with  alkaline  carbonates,  a  yellow  precipitate 
after  a  while.  No  precipitate  with  alkaline  chlorides  or  mercuric  cyanide. 
Zinc  precipitates  metallic  rhodium. 


382  TETKAD   METALS. 

An  alloy  of  steel  with  a  small  quantity  of  rhodium  is  said  to  possess  ex- 
tremely valuable  properties. 


IRIDITJM. 

Atomic  weight,  198.     Symbol,  Ir. 

When  crude  platinum  is  dissolved  in  nitromuriatic  acid,  a  small  quantity 
of  a  gray  scaly  metallic  substance  usually  remains  behind,  having  altogether 
resisted  the  action  of  the  acid :  this  is  a  native  alloy  of  iridium  and  osmium, 
called  osmiridium  or  iridosmine;  it  is  reduced  to  powder,  mixed  with  an  equal 
weight  of  dry  sodium  chloride,  and  heated  to  redness  in  a  glass  tube, 
through  which  a  stream  of  moist  chlorine  gas  is  transmitted.  The  farther 
extremity  of  the  tube  is  connected  with  a  receiver  containing  solution  of 
ammonia.  The  gas,  under  these  circumstances,  is  rapidly  absorbed,  iridium 
chloride  and  osmium  chloride  being  produced:  the  former  remains  in  com- 
bination with  the  sodium  chloride ;  the  latter,  being  a  volatile  substance,  is 
carried  forward  into  the  receiver,  where  it  is  decomposed  by  the  water  into 
osmic  and  hydrochloric  acids,  which  combine  with  the  alkali.  The  contents 
of  the  tube  when  cold  are  treated  with  water,  by  which  the  iridium  and 
sodium  chloride  is  dissolved  out:  this  is  mixed  with  an  excess  of  sodium 
carbonate  and  evaporated  to  dryness.  The  residue  is  ignited  in  a  crucible, 
boiled  with  water,  and  dried ;  it  then  consists  of  a  mixture  of  ferric  oxide 
and  a  combination  of  iridium  oxide  with  soda :  it  is  reduced  by  hydrogen 
at  a  high  temperature,  and  treated  successively  with  water  and  strong  hy- 
drochloric acid,  by  which  the  alkali  and  the  iron  are  removed,  while  me- 
tallic iridium  is  left  in  a  finely  divided  state.  By  strong  pressure  and  ex- 
posure to  a  white  heat,  a  certain  degree  of  compactness  may  be  communi- 
cated to  the  metal.* 

Iridium  is  a  white  brittle  metal,  fusible  with  great  difficulty  before  the 
oxy-hydrogen  blowpipe.  Deville  and  Debray,  by  means  of  their  powerful 
oxy-hydrogen  blast  furnace,  have  fused  it  completely  into  a  pure  white 
mass,  resembling  polished  steel,  brittle  in  the  cold,  somewhat  malleable  at 
a  red  heat,  and  having  a  density  equal  to  that  of  platinum,  viz.  21-15, 
(21 '8  Hare.)  By  moistening  the  pulverulent  metal  with  a  small  quantity 
of  water,  pressing  it  tightly,  first  between  filtering  paper,  then  very  forci- 
bly in  a  press,  and  calcining  it  at  a  white  heat  in  a  forge-fire,  it  may  be 
obtained  in  the  form  of  a  compact,  very  hard  mass,  capable  of  taking  a 
good  polish,  but  still  very  porous,  and  of  a  density  not  exceeding  16-0. 
After  strong  ignition  it  is  insoluble  in  all  acids,  but  when  reduced  by  hy- 
drogen at  low  temperatures,  it  oxidizes  slowly  at  a  red  heat,  and  dissolves 
in  nitro-muriatic  acid.  It  is  usually  rendered  soluble  by  fusing  it  with 
nitre  and  caustic  potash,  or  by  mixing  it  with  common  salt,  or  better,  with 
a  mixture  of  the  chlorides  of  potassium  and  sodium,  and  igniting  it  in  a 
current  of  chlorine,  as  above  described. 

Iridium  forms  three  series  of  compounds,  namely,  the  hypoiridious  com- 
pounds, in  which  it  is  bivalent,  as  Ir//Cl2,  IrO ;  the  iridious  compounds,  in 

IrCl3 
which  it  is  quadrivalent,  but  apparently  trivalent,  e.  g.,  Ir2Cl6  =  I         , 

IrCl3 
and  the  iridic  compounds,  in  which  it  is  also  quadrivalent,  as  in  IrCl4,  Ir02, 

*  Osmiridium,  however,  generally  contains  platinum,  ruthenium,  and  other  metals  of  the 
same  group,  which  are  not  effectually  separated  by  the  method  above  described.  The  complete 
separation  of  the  several  metals  of  the  platinum  group  has  of  late  years  formed  the  subject  of 
several  elaborate  investigations,  into  which  the  limits  of  this  work  will  not  permit  us  to  enter. 
(See  Watts's  Dictionary  of  Chemistry,  iii.  35 ;  iv.  241,  680;  v.  101, 124.) 


IRIDIUM.  383 

&c.  It  appears  to  be  incapable  of  uniting  with  more  than  four  atoms  of  a 
monad  element,  and  is  therefore  regarded  as  a  tetrad.*  It  forms  also  a 
trioxide,  Ir03,  in  which  it  is  apparently  sexvalent,  but  the  oxide  may  be 

represented  by  the  formula     Ir     ,  in  which  the  metal  appears  also  to  be 


quadrivalent. 

CHLORIDES. — Iridium  appears  to  form  three  chlorides,  but  only  two  of 
them  —  namely,  the  trichloride  and  tetrachloride  —  have  been  obtained  in 
definite  form. 

The  dichloride,  Ir//Cl2,  is  not  known  in  the  separate  state,  but  appears  to 
exist  in  certain  double  salts,  called  hypochloriridites. 

The  trichloride  or  Iridious  chloride,  Ir2Cl6,  is  prepared  by  strongly  heating 
iridium  with  nitre,  adding  water  and  enough  nitric  acid  to  saturate  the 
alkali,  warming  the  mixture,  and  then  dissolving  the  precipitated  hydrate 
of  the  sesquioxide  in  hydrochloric  acid ;  it  forms  a  dark  yellowish-brown 
solution.  This  substance  combines  with  other  metallic  chlorides,  forming 
compounds  called  irido so- chlorides  or  chloriridites,  which  may  be  prepared  by 
reducing  the  corresponding  chloriridiates  with  sulphurous  acid,  hydrogen 
sulphide,  or  potassium  ferrocyanide.  Glaus  has  obtained  the  compounds 
Ir2Cl6.6NH4Cl  60H2,  Ir2Cl6.6KC1.60H2,  and  Ir2Cl6.6NaC1.240H6.  They  are 
olive-green  pulverulent  salts,  soluble  in  water. 

The  tetrachloride,  or  Iridic  chloride,  IrCl4,  is  obtained  in  solution  by  dis- 
solving very  finely  divided  iridium,  or  one  of  its  oxides,  or  the  trichloride, 
in  nitromuriatic  acid,  and  heating  the  liquid  to  the  boiling  point.  On 
evaporating  the  solution,  it  remains  in  the  form  of  a  black,  deliquescent, 
amorphous  mass,  translucent  with  dark-red  color  at  the  edges;  soluble, 
with  reddish-yellow  color,  in  water.  It  unites  with  alkaline  chlorides, 
forming  compounds  called  iridio chlorides  or  chloriridiates,  analogous  in  com- 
position to  the  chloroplatinates.  The  ammonium  salt,  IrCl4.2NH4C1.0H2,  and 
the  potassium  salt,  IrCl4.2KCl,  are  formed,  as  dark-brown  crystalline  precip- 
itates, on  mixing  the  solutions  of  the  component  chlorides.  The  potassium 
salt  may  also  be  prepared  by  passing  chlorine  over  a  gently  ignited  and 
finely  divided  mixture  of  iridium  with  potassium  chloride.  It  is  soluble  in 
boiling  water,  and  crystallizes  in  black  octohedrons,  yielding  a  red  powder. 
The  sodium  salt,  IrCl4.2NaC1.60H2,  prepared  like  the  potassium  salt,  forms 
easily  soluble  black  tables  and  prisms,  isomorphous  with  the  corresponding 
platinum  salt. 

IODIDES.  —  Iridium  forms  three  iodides,  IrI2,  Ir2I$,  and  IrI4,  analogous 
to  the  chlorides,  and  yielding  similar  double  salts  with  the  iodides  of  the 
alkali-metals,  f 

OXIDES. — Iridium  forms  four  oxides,  IrO,  Ir203,  Ir02,  and  Ir03.  The 
monoxide,  or  hypoiridious  oxide,  IrO,  is  but  little  known.  It  is  obtained  by 
precipitating  an  alkaline  hypochloriridite  with  caustic  alkali  in  an  atmo- 
sphere of  carbon  dioxide  (p.  166) ;  but  on  exposure  to  the  air  it  is  quickly 
converted  into  a  higher  oxide. 

The  sesquioxide,  or  Iridious  oxide,  Ir203,  was  formerly  regarded  as  the 
most  easily  formed  and  most  stable  of  the  oxides  of  iridium ;  but,  according 

*  A  hexchloride,  IrC16,  was  said  by  Berzelins  to  be  obtained  in  combination  with  potassium 
chloride  by  fusing  iridosmine  with  nitre;  but  according  to  Glaus,  the  suit  thus  formed  was 
really  a  ruthenium  compound,  having  been  prepared  by  Bcrzelius  from  iridosmiuo  containing 
ruthenium. 

t  Offler,  Ueber  die  lodwrUndungen  des  Iridiums.    Qottingen,  1857, 


384:  TETRAD    METALS. 

to  Glaus,  it  has  a  great  tendency  to  take  up  oxygen  and  pass  to  the  state 
of  dioxide.  It  may  be  prepared  by  gently  igniting  a  mixture  of  potassium 
chloriridite  (Ir2Cl6.6KCl)  with  sodium  carbonate  in  an  atmosphere  of  car- 
bon dioxide;  on  treating  the  product  with  water,  the  sesquioxide  remains 
in  the  form  of  a  black  powder  insoluble  in  acids.  It  forms  two  hydrates, 
Ir203.30H2,  and  Ir203.50H2.  It  unites  with  bases,  forming  salts  which  may 
be  called  iridites.  A  solution  of  a  chloriridite  in  excess  of  lime-water  de- 
posits, after  standing  for  some  time  out  of  contact  of  air,  a  dirty  yellow 
precipitate  containing  Ir203.3CaO. 

The  dioxide,  or  Iridic  oxide,  Ir02,  is,  according  to  Glaus,  the  most  easily 
prepared  and  most  stable  of  all  the  oxides  of  iridium,  and  is  always  de- 
posited in  the  form  of  a  bulky,  indigo-colored  hydrate,  Ir02.20H2,  when  a 
solution  of  either  of  the  chlorides  of  iridium  or  their  double  salts  is  boiled 
with  an  alkali ;  but  it  always  retains  3  or  4  per  cent,  of  the  alkali.  The 
hydrate  may  also  be  obtained  by  dissolving  the  hydrated  sesquioxide  in 
potash  and  treating  the  solution  with  an  acid.  It  dissolves  in  acids,  form- 
ing solutions  which  are  dark-brown  when  concentrated,  reddish-yellow 
when  dilute. 

The  trioxide.  or  Periridic  oxide,  Ir03,  is  not  known  in  the  free  state,  but  is 
formed  in  combination  with  potash,  when  iridium  is  fused  for  some  time 
with  nitre.  The  resulting  blackish-green  mass  dissolves  in  water,  forming 
a  deep  indigo-colored  solution  of  basic  potassium  periridiate,  leaving  a 
black  crystalline  powder  consisting  of  acid  periridiate.* 

Iridium,  like  the  other  platinum  metals,  shows  but  little  tendency  to 
form  oxygen-salts.  The  oxides  dissolve  in  acids,  but  no  definite  salts  are 
obtained  in  this  way.  The  solution  of  iridic  oxide  in  sulphuric  acid  has  a 
dark-brown  color,  which  is  not  modified  by  potash  in  the  same  manner  as 
that  of  the  dichloride,  neither  does  it  yield  any  blue  precipitate  on  boiling. 

The  only  definite  oxygen-salts  of  iridium  that  have  been  obtained  are 
double  salts  containing  sulphurous  and  dithionic  acids. 

Hypo-iridoso-potassic  sulphite,  S03Ir//.3S03K2,  is  obtained  as  a  white  crys- 
talline powder,  when  the  mother-liquor  obtained  in  preparing  potassium 
chloriridite  by  passing  sulphurous  oxide  through  a  solution  of  the  chlor- 
iridiate,  is  evaporated  to  a  small  bulk. 

SULPHIDES.  —  Three  sulphides  of  iridium  are  known,  analogous  to  the 
first  three  oxides  above  described.  The  sesqvisulphide  and  disulphide  are 
obtained  as  brown-black  precipitates  by  treating  the  solutions  of  the  tri- 
chloride and  tetrachloride  respectively  with  hydrogen  sulphide.  The  mono- 
sulphide  is  a  grayish-black  substance  obtained  by  decomposing  either  of 
the  higher  sulphides  in  a  close  vessel. 

AMMONIACAL  COMPOUNDS  OF  IRIDIUM.  —  The  ammonio-chlorides,  N2H6Ir" 
C12  and  N4H,2IrCl2,  or  [N2H4Ir"(NH4)2]Cl2,  together  with  the  corresponding 
sulphates,  are  prepared  like  the  platinous  compounds  of  analogous  compo- 
sition, which  they  also  resemble  in  their  properties.  The  nitratochloride, 
[N2H4Ir//(NH4)2](N03)Cl,  analogous  to  Gros'  platinum  nitrate,  is  formed  by 
heating  the  chloride,  N2H6IrCl2,  with  strong  nitric  acid.  Tetrammonio-iridic 
chloride,  (N4H12Irlv)Cl2,  is  obtained  as  a  violet  precipitate  by  treating  the 
nitrate  just  mentioned  with  hydrochloric  acid.f 

The  compound,  10NH3.Ir2Cl6,  or  [rf8H7Ir'"(NH4)2]'"2CV  to  which  there 
is  no  analogue  in  the  platinum  series,  is  obtained  as  a  flesh-colored  crys- 
talline powder  by  prolonged  digestion  of  ammonium  chloriridite  with  warm 
aqueous  ammonia.  The  corresponding  carbonate,  nitrate,  and  sulphate 
have  also  been  prepared.  J 

*  Clans,  Ann.  Ch.  Pharm.  lix.  249. 

f  Skoblikoff.  Ann.  Ch.  Pharm.  Ixxxiv.  275. 

j  Claus,  Beitrafie  zur  C/iemie  der  Platinmetalle.    Dorpat,  1854. 


RUTHENIUM.  385 

Iridic  solutions  (containing  the  dioxide  or  tetrachloride)  are  of  a  dark 
brown-red  color;  iridious  solutions  (containing  the  sesquioxide  or  tri- 
chloride) have  an  olive-green  color.  The  characters  of  an  iridic  solution 
are  best  observed  with  sodium  chloriridiate,  all  the  other  iridic  compounds 
being  but  slightly  soluble. 

Iridic  solutions  give  with  ammonium  or  potassium  chloride  a  crystalline 
precipitate  of  ammonium  or  potassium  chloriridiate,  which  is  distinguished 
from  the  corresponding  platinum  precipitate  by  its  dark  brown-red  color, 
and  further  by  its  reduction  to  soluble  chloriridite  when  treated  with  solu- 
tion of  hydrogen  sulphide.  This  reaction  serves  for  the  separation  of 
iridium  from  platinum. 


RUTHENIUM. 

Atomic  weight,  104.     Symbol,  Ru. 

This  metal,  discovered  by  Glaus,  in  1846,  occurs  in  platinum  ore,  and 
chiefly  in  osmiridium,  of  which  there  are  two  varieties  —  one  scaly,  consist- 
ing almost  wholly  of  osmium,  iridium,  and  ruthenium,  while  the  other, 
which  is  granular,  contains  but  mere  traces  of  osmium  and  ruthenium,  but 
is  very  rich  in  iridium  and  rhodium.  To  obtain  ruthenium,  scaly  osmiri- 
dium is  heated  to  bright  redness  in  a  porcelain  tube,  through  which  a  cur- 
rent of  air  (freed  from  carbonic  acid  by  passing  through  potash,  and  from 
organic  matter  by  passing  through  oil  of  vitriol)  is  drawn  by  means  of  an 
aspirator.  The  osmium  and  ruthenium  are  thereby  oxidized,  the  former 
being  carried  forward  as  tetroxide  and  condensed  in  caustic  potash  solution, 
while  the  ruthenium  oxide  remains  behind,  together  with  iridium ;  and  by 
fusing  this  residue  with  potassium  hydrate,  treating  the  mass  with  water, 
and  leaving  the  liquid  in  a  corked  bottle  for  about  two  hours  to  clarify,  an 
orange-colored  solution  of  potassium  rutheniate  is  obtained,  which,  when 
neutralized  with  nitric  acid,  deposits  velvet-black  ruthenium  sesquioxide, 
and  this  when  washed,  dried,  and  ignited  in  hydrogen,  yields  the  metal. 

Ruthenium  thus  prepared,  forms  porous  lumps  very  much  like  iridium, 
and  is  moderately  easy  to  pulverize.  It  is  the  most  refractory  of  all  metals 
except  osmium.  Deville  and  Debray  have,  however,  fused  it  by  placing  it 
in  the  hottest  part  of  the  oxy-hydrogen  flame.  After  fusion  it  has  a  density 
of  11-4;  that  of  the  porous  metal  is  8-6. 

Ruthenium  is  scarcely  attacked  by  nitromuriatic  acid.  It  is,  however, 
more  easily  oxidized  than  platinum,  or  even  than  silver.  When  pure  it  is 
easily  oxidized  by  fusion  with  potassium  hydrate,  still  more  easily  on  addi- 
tion of  a  small  quantity  of  nitrate  or  chlorate,  producing  potassium  ruthe- 
niate, which  dissolves  in  water  with  orange -yellow  color. 

CHLORIDES. — Ruthenium  is  a  tetrad,  like  the  other  platinum  metals,  and 
forms  three  chlorides,  RuCl2,  Ru2Cl6,  and  RuCl4. 

The  dichloride,  RuCl2,  is  produced,  together  with  the  trichloride,  by 
igniting  pulverized  ruthenium  in  a  stream  of  chlorine,  the  trichloride  then 
volatilizing,  while  the  dichloride  remains  in  the  form  of  a  black  crystalline 
powder,  insoluble  in  water  and  in  all  acids,  even  nitro-muriatic  acid,  and 
only  partially  decomposed  by  alkalies.  A  soluble  dichloride  is  formed  by 
passing  sulpliydric  acid  gas  into  a  solution  of  the  trichloride,  a  brown  sul- 
phide being  then  precipitated,  and  the  solution  acquiring  a  lino  blue  color. 

The  trichloride  or  Ruthcnious  chloride,  Ru.2Cl6.  prepared  by  precipitating 
a  solution  of  potassic  rutheniate  with  an  acid,  dissolving  the  precipitated 
black  oxide  in  hydrochloric  acid,  and  evaporating,  is  a  yellow-brown,  crys- 
talline, very  deliquescent  mass,  becoming  dark-green  and  blue  at  certain 
33 


386  TETRAD    METALS. 

points  when  strongly  heated.  It  dissolves  easily  in  water  and  in  alcohol, 
leaving  a  small  quantity  of  a  yellow  insoluble  salt. 

The  concentrated  solution  of  ruthenious  chloride,  mixed  with  concen- 
trated solutions  of  the  chlorides  of  potassium  and  ammonium,  yields  the 
double  salts,  Ru2Cl6.4KCl,  and  Ru2C16.4NH4Cl,  in  the  form  of  crystalline 
precipitates,  with  violet  iridescence,  very  slightly  soluble  in  water,  insoluble 
in  alcohol. 

The  tetrachloride  or  Ruthenic  chloride,  RuCl4,  is  known  only  in  its  double 
salts.  The  potassium-salt,  RuCl4.2KCl,  is  prepared  by  mixing  a  solution  of 
ruthenic  hydrate  in  hydrochloric  acid  with  potassium  chloride,  and  evapo- 
rating to  the  crystallizing  point.  It  is  brown,  with  rose-colored  iridescence, 
very  soluble  in  water,  but  insoluble  in  alcohol.  The  ammonium  salt, 
RuCl4.2NH4Cl,  is  prepared  like  the  potassium  salt,  which  it  resembles  closely. 

OXIDES. — Ruthenium  forms  five  oxides,  viz.,  RuO,  Ru203,  Ru02,  Ru03, 
and  Ru04,  the  fourth,  however,  being  known  only  in  combination. 

The  monoxide,  RuO,  obtained  by  calcining  the  dichloride  with  sodium 
carbonate  in  a  current  of  carbon  dioxide,  and  washing  the  residue  with 
water,  has  a  dark-gray  color  and  metallic  lustre ;  is  not  acted  upon  by  acids ; 
but  is  reduced  by  hydrogen  at  ordinary  temperatures.  —  The  sesquioxide,  or 
Ruthenious  oxide,  Ru203,  is  a  bluish-black  powder,  formed  by  heating  the 
metal  in  the  air.  The  corresponding  hydrate,  Ru203.  30H,  or  RuHg03,  is 
obtained  by  precipitating  ruthenious  chloride  with  an  alkaline  carbonate, 
as  a  blackish-brown  substance  which  dissolves  with  yellow  color  in  acids. — 
The  dioxide,  or  Ruthenic  oxide,  Ru02,  is  a  black-blue  powder,  obtained  by 
roasting  the  disulphide.  Ruthenic  hydrate,  Ru02.20H2,  or  RuivH404,  is  ob- 
tained as  a  gelatinous  precipitate  by  decomposing  potassium  chlororutheniate 
with  sodium  carbonate.  —  The  trioxide,  Ru03,  commonly  called  ruthenic  acid, 
is  known  only  as  a  potassium-salt,  wjiich  is  obtained  by  igniting  ruthenium 
with  caustic  potash  and  nitre:  it  forms  an  orange-yellow  solution.  —  The 
tetroxide,  Ru04,  is  a  volatile  compound,  analogous  to  osmic  tetroxide,  ob- 
tained by  heating  ruthenium  with  potash  and  nitre,  in  a  silver  crucible,  dis- 
solving the  fused  mass  in  water,  and  passing  chlorine  through  the  solution 
in  a  tubulated  retort,  connected  by  a  condensing-tube  with  a  receiver  con- 
taining potash.  The  tetroxide  then  passes  over  and  condenses  in  the  neck 
of  the  retort,  and  in  the  tube,  as  a  golden-yellow  crystalline  crust,  which 
melts  between  50°  and  60°.  It  is  heavier  than  oil  of  vitriol,  dissolves 
slightly  in  water,  readily  in  hydrochloric  acid,  forming  a  solution  easily 
decomposed  by  alcohol,  sulphurous  acid,  and  other  reducing  agents. 

SULPHIDES.  —  Hydrogen  sulphide,  passed  into  a  solution  of  either  of  the 
chlorides  of  ruthenium,  usually  forms  a  precipitate  consisting  of  ruthenium 
sulphide  and  oxysulphide  mixed  with  free  sulphur.  The  blue  solution  of 
the  dichloride  yields  a  dark-brown  sesquisulphide,  Ru2S3.  When  hydrogen 
sulphide  is  passed  for  a  long  time  into  a  solution  of  the  trichloride,  ruthe- 
nium disulphide,  RuS2,  is  formed,  as  a  brown-yellow  precipitate,  becoming 
dark-brown  by  calcination. 

AMMONIACAL  RUTHENIUM  COMPOUNDS.  —  Tetrammonio-hyporuthcnious  chlor- 
ide, 4NH3.RuCl2.30H2,  or  [N2H4Ru//(NH4)2]Cl2  30H2,  is  formed  by  boiling 
the  solution  of  ammonium  chlororutheniate  (RuCl4.2NH4Cl),  with  ammonia. 
It  forms  golden-yellow  oblique  rhombic  crystals,  very  soluble  in  water,  in- 
soluble in  alcohol.  Treated  with  silver  oxide,  it  yields  the  corresponding 
oxide,  4NH3  RuO,  which,  however,  is  decomposed  by  evaporation  of  its 
solution,  giving  oft7  half  its  ammonia,  and  leaving  the  compound  2NH3.RuO, 
or  (N2H6Ru//)0.  The  carbonate,  nitrate,  and  sulphate,  obtained  by  treat- 
ing this  last-mentioned  oxide  with  the  corresponding  silver  salts,  form 
yellow  crystals. 


OSMIUM.  387 

The  compounds  of  ruthenium  may  readily  be  distinguished  from  those 
of  the  other  platinum-metals,  by  fusing  a  few  milligrammes  of  the  sub- 
stance in  a  platinum-spoon,  with  a  large  excess  of  nitre,  leaving  it  to  cool 
when  it  ceases  to  froth,  and  dissolving  the  cooled  mass  in  a  little  distilled 
water.  An  orange-yellow  solution  of  potassium  rutheniate  is  thus  formed, 
which  on  addition  of  a  drop  or  two  of  nitric  acid,  yields  a  bulky,  black 
precipitate ;  and  on  adding  hydrochloric  acid  to  the  liquid,  with  the  pre- 
cipitate still  in  it,  and  heating  it  in  a  porcelain  crucible,  the  oxide  dissolves, 
forming  a  solution  which  has  a  fine  orange-yellow  when  concentrated,  and 
when  treated  with  hydrogen-sulphide,  till  it  becomes  nearly  black,  yields  a 
nitrate  of  a  splendid  sky-blue  color.  Characteristic  reactions  are  also  ob- 
tained with  potassium  sulphocyanate,  which  colors  the  liquid  deep  red,  chang- 
ing to  violet  on  heating,  and  with  lead  acetate,  which  forms  a  purple-red 
precipitate. 


OSMIUM. 

Atomic  weight,  199.     Symbol,  Os. 

The  separation  of  this  metal  from  iridium,  ruthenium,  and  the  other 
metals  with  which  it  is  associated  in  native  osmiridium,  and  in  platinum 
residues,  depends  chiefly  on  its  ready  oxidation  with  nitric  or  nitromuratic 
acid,  or  by  ignition  in  air  or  oxygen,  and  the  volatility  of  the  oxide  thus 
produced. 

To  prepare  metallic  osmium,  the  solution  obtained  by  condensing  the 
vapor  of  osmium  tetroxide  in  potash  (p.  385)  is  mixed  with  excess  of  hy- 
drochloric acid,  and  digested  with  mercury  in  a  well-closed  bottle  at  40° 
C.  (104°  F.)  The  osmium  is  then  reduced  by  the  mercury,  and  an  amalgam 
is  formed,  which,  when  distilled  in  a  stream  of  hydrogen  till  all  the  mer- 
cury and  calomel  are  expelled,  leaves  metallic  osmium  in  the  form  of  a 
black  powder  (Berzelius).  The  metal  may  also  be  obtained  by  igniting 
ammonium  chloro-osmite  with  sal-ammoniac. 

The  properties  of  osmium  vary  according  to  its  mode  of  preparation.  In 
the  pulverulent  state  it  is  black,  destitute  of  metallic  lustre,  which,  how- 
ever, it  acquires  by  burnishing;  in  the  compact  state,  as  obtained  by  Ber- 
zelius's  method  above  described,  it  exhibits  metallic  lustre,  and  has  a  den- 
sity of  10.  Deville  and  Debray,  by  igniting  precipitated  osmium  sulphide 
in  a  crucible  of  gas-coke,  at  the  melting  heat  of  nickel,  obtained  it  in 
bluish-black,  easily  divisible  lumps.  When  heated  to  the  melting  point  of 
rhodium,  it  becomes  more  compact,  and  acquires  a  density  of  21-3  to  21-4. 
At  a  still  higher  temperature,  capable  of  melting  ruthenium  and  iridium, 
and  volatilizing  platinum,  osmium  likewise  volatilizes,  but  still  does  not 
melt;  in  fact,  it  is  the  most  refractory  of  all  metals. 

Osmium  in  the  finely  divided  state  is  highly  combustible,  continuing  to 
burn  when  set  on  fire,  till  it  is  all  volatilized  as  tetroxide.  In  this  state 
also  it  is  easily  oxidized  by  nitric  or  nitromuriatic  acid,  being  converted 
into  tetroxide.  But  after  exposure  to  a  red  heat,  it  becomes  less  combus- 
tible, and  is  not  oxidized  by  nitric  or  nitromiiriatic  acid.  Osmium  which 
has  been  heated  to  the  melting-point  of  rhodium,  does  not  give  off  any 
vapor  of  tetroxide -when  heated  in  the  air  to  the  melting-point  of  zinc,  but 
takes  fire  at  higher  temperatures. 

OSMIUM  CHLORIDES. — Osmium  forms  three  chlorides,  analogous  to  those 
of  iridium  and  ruthenium.  When  it  is  heated  in  dry  chlorine  g:  s,  there 
is  formed,  first  a  blue-black  sublimate  of  the  dichloride,  then  a  red  subli- 
mate of  the  tetrachloride.  The  dichloride,  or  hypo-osmious  chloride,  dissolves 


388  TETRAD    METALS. 

in  water  with  dark  violet-blue  color.  It  is  likewise  formed  by  the  action 
of  reducing  agents  on  either  of  the  higher  chlorides,  into  which,  on  the 
other  hand,  it  is  easily  converted  by  oxidation.  The  addition  of  potassium 
chloride  renders  it  more  stable,  by  forming  a  double  salt.  The  trichloride, 
Os2C16,  has  not  been  isolated,  but  is  contained  in  the  solution  obtained  by 
treating  the  sesquioxide  with  hydrochloric  acid.  It  forms  double  salts 
with  alkaline  chlorides.  The  potassium-salt,  Os2Cl6.6KC1.60H2,  is  produced 
together  with  potassium  chlorosmate,  when  a  mixture  of  pulverized  osmium 
and  potassium  chloride  is  ignited  in  chlorine  gas;  it  forms  dark  red-brown 
crystals. 

The  tetrachloride,  or  Osmic  chloride,  OsCl4,  is  the  red  compound  which  con- 
stitutes the  principal  part  of  the  product  obtained  by  igniting  osmium  in 
chlorine  gas.  It  dissolves  with  yellow  color  in  water  and  alcohol,  and  is 
decomposed  quickly  in  dilute  solution,  more  slowly  in  presence  of  hydro- 
chloric acid  or  metallic  chlorides,  yielding  a  black  precipitate  of  osmic 
oxide,  and  a  solution  of  osmium  tetroxide  in  hydrochloric  acid. 

Osmic  chloride  unites  with  the  chlorides  of  the  alkali-metals,  forming 
salts  sometimes  called  osmio chlorides,  or  chlorosmates.  From  the  solutions  of 
these  salts,  hydrogen  sulphide,  and  ammonium  sulphide,  slowly  precipitate  a 
yellow-brown  sulphide  insoluble  in  alkaline  sulphides ;  silver  nitrate  forms 
an  olive-green,  stannous  chloride  a  brown  precipitate.  Tannic  acid,  on  heat- 
ing, produces  a  blue  color,  but  no  precipitate;  potassium  ferrocyanide,  first  a 
green,  then  a  blue  color;  potassium  iodide,  a  deep  purple-red  color.  Potash 
gives  a  black,  ammonia  a  brown  precipitate,  slowly  in  the  cold,  immediately 
on  boiling.  Metallic  zinc  and  sodium  formate  throw  down  metallic  osmium. 

Sodium  osmiochloride,  OsCl4.2NaCl,  prepared  by  heating  a  mixture  of 
osmium  sulphide  and  sodium  chloride  in  a  current  of  chlorine,  crystallizes 
in  orange-colored  rhombic  prisms,  an  inch  long,  easily  soluble  in  water, 
and  in  alcohol.  The  potassium  and  ammonium  salts,  of  analogous  composi- 
tion, are  obtained  as  red-brown  crystalline  precipitates  on  adding  sal-am- 
moniac or  potassium  chloride  to  the  solution  of  the  sodium  salt. 

OXIDES. — Osmium  forms  five  oxides  analogous  to  those  of  ruthenium. 
The  monoxide  or  hypo-osmious  oxide,  OsO,  is  obtained  by  igniting  hypo-osmi- 
ous  sulphite  in  a  stream  of  carbonic  acid  gas ;  also  as  blue-black  hydrate, 
by  heating  the  same  salt  with  strong  potash  solution  in  a  closed  vessel. 
Hypo-osmious  sulphite,  S030s//  or  S02,OsO,  is  a  black-blue  salt,  produced 
by  mixing  the  aqueous  solution  of  osmium  tetroxide  with  sulphurous  acid. — 
The  sesquioxide  or  osmious  oxide,  Os203,  is  obtained  by  heating  either  of  the 
double  salts  of  the  trichloride  with  sodium  carbonate  in  a  stream  of  car- 
bonic acid  gas.  It  is  a  black  powder  insoluble  in  acids.  The  hydrate,  ob- 
tained by  precipitation,  has  a  dirty  brown-red  color,  is  soluble  in  acids,  but 
does  not  yield  pure  salts. 

The  dioxide,  or  Osmic  oxide,  OsO?,  is  obtained  as  a  black  insoluble  powder, 
by  heating  potassium  osmiochloride  with  sodium  carbonate  in  a  stream  of 
carbonic  acid  gas,  or  in  copper-red  metallic-shining  lumps,  by  heating  the 
corresponding  hydrate.  Osmic  hydrate,  OsOr20H2,  is  obtained  by  precipi- 
tating a  solution  of  potassium  osrnio-chloride  with  potash,  at  the  boiling 
heat,  or  in  greater  purity  by  mixing  a  solution  of  potassic  osmite,  Os03.K20, 
with  dilute  nitric  acid. 

The  trioxide,  Os03,  is  not  known  in  the  free  state,  but  combines  with 
alkalies,  forming  salts  called  osmitcs,  which  are  produced  by  the  action  of 
reducing  agents  on  the  tetroxide  in  presence  of  alkalies.  The  potassium  salt, 
Os03.K20.20H2,  is  a  rose-colored  crystalline  powder. 

The  tetroxide,  Os04,  commonly  called  osmic  acid,  is  the  volatile,  strong- 
smelling  compound,  formed  when  osmium  or  either  of  its  lower  oxides  is 
heated  in  the  air,  or  treated  with  nitric  or  nitromuriatic  acid.  It  may  be 


TIN.  389 

prepared  by  heating  osmium  in  a  current  of  oxygen  gas,  and  condenses  in 
the  cool  part  of  the  apparatus  in  colorless,  transparent  crystals.  It  melts 
below  100°,  and  boils  at  a  temperature  a  little  above  its  melting  point.  Its 
vapor  has  an  intolerably  pungent  odor ;  attacks  the  eyes  strongly  and  pain- 
fully, and  is  excessively  poisonous.  Osmium  tetroxide  is  dissolved  slowly, 
but  in  considerable  quantity,  by  water,  forming  an  acid  solution.  It  is  a 
powerful  oxidizing  agent,  decolorizing  indigo  solution,  separating  iodine 
from  potassium  iodide,  converting  alcohol  into  aldehyde  and  acetic  acid,  &c. 
It  dissolves  in  alkalies,  forming  yellow-red  solutions,  which  are  inodorous 
when  cold,  but  when  heated,  give  off  the  tetroxide  and  free  oxygen,  leaving 
a  residue  of  alkaline  osmite. 

SULPHIDES.  — Osmium  burns  in  sulphur-vapor.  Five  sulphides  of  osmium 
are  said  to  exist,  analogous  to  the  oxides,  the  first  four  being  produced  by 
decomposing  the  corresponding  chlorides  with  hydrogen  sulphide,  and  the 
tetrasulphide  by  passing  that  gas  into  a  solution  of  the  tetroxide.  The  last 
is  a  sulphur-acid,  perfectly  soluble  in  water,  whereas  the  others  are  sul- 
phur-bases, slightly  soluble  in  water,  and  forming  deep  yellow  solutions. 

AMMONIACAL  OSMIUM  COMPOUNDS. — A  cold  solution  of  potassium  osmite, 
mixed  with  sal-ammoniac,  yields  a  yellow  crystalline  precipitate,  consisting, 
according  to  Glaus,  of  hydra-ted  osmammonium  chloride,  (N2H6Os//)Cl2.  An 
aqueous  solution  of  the  tetroxide  treated  with  ammonia,  yields  a  brown- 
black  powder,  consisting  of  N2H8Os03,  or  [N2H6(OsO)"]O.OH2. 

OSMIAMIG  ACID,  Os2N205H2. — The  potassium-salt,  of  this  bibasic  acid, 
Os2N205K2,  is  produced  by  the  action  of  ammonia  on  a  hot  solution  of 
osmium  tetroxide  in  excess  of  potash : 

60s04  -f  8NH3  -f  60KH  ==  30s2N205K2  -f  150H2  -f  N2. 

It  separates  as  a  yellow  crystalline  powder,  and  its  solution,  treated  with  sil- 
ver nitrate,  yields  a  precipitate  of  silver  osmiamate,  Os2N205Ag2,  from  which 
the  aqueous  acid  may  be  prepared  by  decomposition  with  hydrochloric  acid. 
It  is  a  strong  acid, decomposing,  not  only  the  carbonates,  but  also  the  chlor- 
ides, of  potassium  and  sodium.  The  osmiamates  of  the  alkali-metals  and 
alkaline  earth-metals  are  soluble  in  water ;  the  lead,  mercury,  and  silver 
salts  are  insoluble. 

•  All  osmium  compounds,  when  heated  with  excess  of  nitric  acid,  give  off 
the  unpleasant  odor  of  osmium-tetroxide.  By  ignition  in  hydrogen  gas, 
they  are  reduced  to  metallic  osmium,  which,  as  well  as  the  lower  oxides, 
emits  the  same  odor  when  heated  in  contact  with  the  air.  The  reactions  of 
osmium  salts  in  solution  have  already  been  described. 


GROUP  II. 
TIN. 

Atomic  weight,  118.     Symbol,  Sn.  (Stannum.) 

This  valuable  metal  occurs  in  the  state  of  oxide,  and  more  rarely  as  sul- 
phide :  the  principal  tin  mines  are  those  of  Saxony  and  Bohemia,  Malacca, 
and  more  especially  Cornwall.  In  Cornwall  the  tin-stone  is  found  as  a  con- 
stituent of  metal-bearing  veins,  associated  with  copper  ore,  in  granite  and 
slate-rocks;  and  as  an  alluvial  deposit,  mixed  with  rounded  pebbles,  in  the 
beds  of  several  small  rivers.  The  first  variety  is  called  mine-  and  the 
33* 


390  TETRAD    METALS. 

second  stream-tin.  Tin  oxide  is  also  found  disseminated  through  the  rock 
itself  in  small  crystals. 

To  prepare  the  ore  for  reduction,  it  is  stamped  to  powder,  washed,  to 
separate  as  much  as  possible  of  the  earthy  matter,  and  roasted,  to  expel 
sulphur  and  arsenic:  it  is  then  strongly  heated  with  coal,  and  the  metal 
thus  obtained  is  cast  into  large  blocks.  Two  varieties  of  commercial  tin 
are  known,  called  grain-  and  bar-tin;  the  first  is  the  best;  it  is  prepared  from 
the  stream  ore. 

Pure  tin  has  a  white  color,  approaching  that  of  silver;  it  is  soft  and 
malleable,  and  when  bent  or  twisted  emits  a  peculiar  crackling  sound;  it 
has  a  density  of  7-3  and  melts  at  237°  C.  (457°  F.)  Tin  is  but  little  acted 
upon  by  air  and  water,  even  conjointly;  when  heated  above  its  melting 
point,  it  oxidizes  rapidly,  becoming  converted  into  a  whitish  powder,  used 
in  the  arts  for  polishing  under  the  name  of  putty-powder.  The  metal  is 
attacked  and  dissolved  by  hydrochloric  acid,  with  evolution  of  hydrogen ; 
nitric  acid  acts  with  great  energy,  converting  it  into  a  white  hydrate  of  the 
dioxide. 

Tin  is  a  tetrad  metal,  and  forms  two  well-defined  classes  of  compounds, 
namely,  the  stannous  compounds,  in  which  it  is  bivalent,  as  Sn/xCl2,  Snx/I2, 
Snx/0,  &c.,  and  the  stannic  compounds,  in  which  it  is  quadrivalent,  as  Sn'TCl4, 
SnivO.,  &c. ;  also  a  few  compounds  called  stannoso-stannic  compounds,  of  inter- 
mediate composition,  and  probably  formed  by  combination  of  stannous  and 
stannic  compounds,  e.g.,  Sn2Cl6=rSnCl2.Snd4;  Sn203— SnO.Sn02. 

CHLORIDES. — The  dichloride,  or  Stannous  chloride,  SnCl2,  is  obtained  in  the 
anhydrous  state  by  distilling  a  mixture  of  calomel  and  powdered  tin,  pre- 
pared by  agitating  the  melted  metal  in  a  wooden  box  until  it  solidifies.  It 
is  a  gray,  resinous-looking  substance,  fusible  below  redness,  and  volatile  at 
a  high  temperature. 

The  hydrated,  chloride,  commonly  called  tin-salt,  is  easily  prepared  by  dis- 
solving metallic  tin  in  hot  hydrochloric  acid.  It  crystallizes  in  needles  con- 
taining SnCl2.20H2,  which  are  freely  soluble  in  a  small  quantity  of  water, 
but  are  apt  to  be  decomposed  in  part  when  put  into  a  large  mass,  unless 
hydrochloric  acid  in  excess  be  present.  Solution  of  stannous  chloride  is 
employed  as  a  deoxidizing  agent ;  it  reduces  the  salts  of  mercury  and  other 
metals  of  the  same  class.  It  is  also  extensively  employed  as  a  mordant  in 
dyeing  and  calico-printing;  sometimes  also  as  an  antichlore. 

Stannous  chloride  unites  with  the  chlorides  of  the  alkali-metals,  forming 
crystallizable  double  salts,  SnCl2.2KCl,  &c.,  called  Stannoso-chlorides  or 
Chloroslannitcs. 

The  tetrachloridj,  or  Stannic  chloride,  SnCl4,  is  an  old  and  very  curious 
compound,  formerly  called  fuming  liquor  of  Libavius.  It  is  made  by  ex- 
posing metallic  tin  to  the  action  of  chlorine,  or,  more  conveniently,  by  dis- 
tilling a  mixture  of  1  part  of  powdered  tin  with  5  parts  of  corrosive  subli- 
mate It  is  a  thin,  colorless,  mobile  liquid,  boiling  at  120°  C.  (248°  F.),  and 
yielding  a  colorless  invisible  vapor.  It  fumes  in  the  air,  and  when  mixed 
with  a  third  part  of  water,  solidifies  to  a  soft  fusible  mass  called  butter  of  tin. 
The  solution  of  stannic  chloride  is  much  employed  by  the  dyer  for  the 
brightening  and  fixing  of  red  colors,  and  is  sometimes  designated  by  the 
old  names,  "composition,  physic,  or  tin  solution;"  it  is  commonly  prepared 
by  dissolving  metallic  tin  in  a  mixture  of  hydrochloric  and  nitric  acids, 
care  being  taken  to  avoid  too  great  elevation  ot  temperature.  The  solution 
when  evaporated  yields  a  deliquescent  crystalline  hydrate,  SnCl4,50H2. 

Stannic  chloride  forms,  with  the  chlorides  of  the  alkali -meta.ls  and  alkaline 
earth-metals,  crystalline  double  salts,  called  Slannochloridcs  or  Chloroslannates, 
e.g.,  SnCl4.2NH4Cl;  SnCl4.BaCl2,  &c.  It  also  forms  crystalline  compounds 
with  the  pentachloride  and  oxychloride  of  phosphorus,  viz.,  SnCl4.PCl5.  ;ind 
SnCl4.POCl3,  and  a  solid  compound  with  phosphine,  containing  3SnCl4  2PH3. 


TIN.  391 

The  trichloride,  or  Stannoso- stannic  chloride,  known  only  in  solution,  is 
produced  by  dissolving  the  sesquioxide  in  hydrochloric  acid.  The  solu- 
tion acts  like  a  mixture  of  the  dichloride  and  tetrachloride. 

FLUORIDES. — Stannous  fluoride,  SnF2,  obtained  by  evaporating  the  solution 
of  stannous  oxide  in  hydrofluoric  acid,  crystallizes  in  small  shining  opaque 
prisms.  Stannic  fluoride,  SnF4,  is  not  known  in  the  free  state,  but  unites 
with  other  metallic  fluorides,  forming  crystalline  compounds  called  stanno- 
ftuorides  or  jluostannatcs,  isomorphous  with  the  corresponding  silicofluor- 
ides,  titariofluorides,  and  zircofluorides.  The  potassium  salt  contains 
SnF4.2KC1.0H2,  the  barium  salt,  SnF4.BaF2,  &c. 

OXIDES. — The  monoxide,  or  Stannous  oxide,  SnO,  is  produced  by  heating 
stannous  oxalate  out  of  contact  with  the  air;  also  by  igniting  starmous  hy- 
drate. This  hydrate,  2SnO.OH2,  or  Sn2H203,  is  obtained  as  a  white  precipi- 
tate by  decomposing  stannous  chloride  with  an  alkaline  carbonate,  carbon 
dioxide  gas  being  at  the  same  time  evolved.  This  hydrate,  carefully  washed, 
dried,  and  heated  in  an  atmosphere  of  carbon  dioxide,  leaves  anhydrous 
stannous  oxide  as  a  dense  black  powder,  which  is  permanent  in  the  air,  but 
when  touched  with  a  red-hot  body,  takes  fire  and  burns  like  tinder,  pro- 
ducing the  dioxide.  The  hydrate  is  freely  soluble  in  caustic  potash;  the 
solution  decomposes  by  keeping  into  metallic  tin  and  dioxide.  It  dissolves 
also  in  sulphuric  acid,  forming  stannous  sulphate,  S04Snx/,  which  crystallizes 
in  needles. 

The  sesquioxide,  Sn203,  is  produced  by  the  action  of  hydrated  ferric  oxide 
upon  stannous  chloride:  it  is  a  grayish,  slimy  substance,  soluble  in  hydro- 
chloric acid,  and  in  ammonia.  This  oxide  has  been  but  little  examined. 

The  dioxide,  or  Stannic  oxide,  Sn02,  occurs  native  as  tin-stone  or  cassi- 
terite,  the  common  ore  of  tin,  and  is  easily  formed  by  heating  tin,  stan- 
nous oxide,  or  stannous  hydrate  in  contact  with  the  air.  As  thus  pre- 
pared, it  is  a  white  or  yellowish  amorphous  powder ;  but  by  passing  the 
vapor  of  stannic  chloride  mixed  with  aqueous  vapor  through  a  red-hot 
porcelain  tube,  it  may  be  obtained  in  crystals.  It  is  not  attacked  by  acids, 
even  in  the  concentrated  state. 

Stannic  oxide  forms  two  hydrates,  differing  from  one  another  in  compo- 
sition and  properties ;  both,  however,  being  acids,  and  capable  of  forming 
salts  by  exchanging  their  hydrogen  for  metals.  These  hydrates  or  acids 
are  stannic  acid,  Sn02.OH2,  or  Sn()3IT2,  and  metastannicacid,  Sn60I0.50H2,  orSng 
015H10,  the  former  being  capable  of  exchanging  the  whole  of  its  hydrogen  for 
metal,  and  forming  the  stannates,  containing  Sn03M2;  while  the  latter  ex- 
changes only  one  fifth  of  its  hydrogen,  forming  the  metastannates,  SnjO^IIgM^. 

Stannic  acid  is  precipitated  by  acids  from  solutions  of  alkaline  stanuates, 
also  from  solution  of  stannic  chloride,  by  calcium  or  barium  carbonate  not 
in  excess ;  alkaline  carbonates  throw  down  an  acid  stannate.  When  dried 
in  the  air  at  ordinary  temperatures,  it  has,  according  to  Weber,  the  com- 
position, Sn02.20H2;  in  a  vacuum  half  the  water  is  given  off,  leaving 
Sn02.OH2. 

Stannic  hydrate  dissolves  in  the  stronger  acids,  forming  the  stannic  salts; 
thus  with  sulphuric  acid  it  forms  stannic  sulphate  (S04)2SniT,  or  2SOs.Sn02. 
Hydrochloric  acid  converts  it  into  the  tetrachloride.  The  stannic  salts  of 
oxygen  acids  are  very  unstable. 

Stannates.  —  Stannic  hydrate  exhibits  acid  much  more  decidedly  than 
basic  properties.  It  forms  easily  soluble  salts  with  the  alkalies,  and  from 
these  the  insoluble  stannates  of  the  earth-metals  and  heavy  metals  may  be 
obtained  by  precipitation.  Sodium  stannate,  SnO3N,%.  which  is  much  used 
in  calico-printing  as  a  ''preparing  salt"  or  mordant,  is  produced  on  the 
large  scale  by  fusing  tin-stone  with  hydrate,  nitrate,  chloride,  or  sulphide 


392  TETRAD  METALS. 

of  Bodium ;  by  boiling  the  tin  ore  with  caustic  soda  solution ;  by  fusing 
metallic  tin  with  a  mixture  of  sodium  nitrate  and  carbonate  ;  or  heating  it 
with  soda  solution  mixed  with  sodium  nitrate  and  chloride.* 

Metastannic  acid  is  produced  hy  the  action  of  nitric  acid  upon  tin.  When 
dried  in  the  air  at  ordinary  temperatures,  it  contains  5Sn02. 100H2,  or  Sn6 
010H15.50H2,  but  at  100°  it  gives  off  5  molecules  of  water,  and  is  reduced 
to  Sn5015H,0.  It  is  a  white  crystalline  powder,  insoluble  in  water  and  in 
acids.  It  dissolves  slowly  in  alkalies  forming  metastannates,  but  is  grad- 
ually deposited  in  its  original  state  as  the  solution  absorbs  carbonic  acid 

from  the  air.     The  potassium  salt,  Sn5015H8K2,  or  (Sn02)6 1    QK2  ,  may  be 

precipitated  in  the  solid  state  by  adding  pieces  of  solid  potash  to  a  solution 
of  metastannic  acid  in  cold  potash.  It  is  gummy,  uncrystallizable,  and 
strongly  alkaline.  The  sodium  salt,  Sn5015HgNa2,  prepared  in  like  manner, 
is  crystallo-granular,  and  dissolves  slowly,  but  completely,  in  water.  The 
metastannates  exist  only  in  the  hydrated  state,  being  decomposed  when 
deprived  of  their  basic  water. 

TIN  SULPHIDES. — The  monomlphide,  SnS,  is  prepared  by  fusing  tin  with 
excess  of  sulphur,  and  strongly  heating  the  product.  It  is  a  lead-gray, 
brittle  substance,  fusible  at  a  red  heat,  and  soluble,  with  evolution  of  sul- 
phuretted hydrogen,  in  hot  hydrochloric  acid.  A  sesquisulphide  may  be 
formed  by  gently  heating  the  above  compound  with  a  third  of  its  weight  of 
sulphur :  it  is  yellowish-gray,  and  easily  decomposed  by  heat.  The  bisul- 
phide, SnS2,  or  Mosaic  gold,  is  prepared  by  exposing  to  a  low  red  heat,  in  a 
glass  flask,  a  mixture  of  12  parts  of  tin,  6  of  mercury,  6  of  sal-ammoniac, 
and  7  of  flowers  of  sulphur.  Sal-ammoniac,  cinnabar,  and  stannous  chlor- 
ide sublime,  while  the  bisulphide  remains  at  the  bottom  of  the  vessel  in  the 
form  of  brilliant  gold-colored  scales:  it  is  used  as  a  substitute  for  gold  pow- 
der. The  same  compound  is  obtained  as  an  amorphous  light-yellow  pow- 
der by  passing  hydrogen  sulphide  into  a  solution  of  stannic  chloride. 


Stannous  salts  give  with : 

Fixed  caustic  alkalies :  white  hydrate,  soluble  in  excess. 
Ammonia :      carbonates  "| 

of  potassium,  sodium,  V  white  hydrate,  nearly  insoluble  in  excess, 
and  ammonium    .     .  ) 

(  black-brown  precipitate  of  monosulphide,-  sol- 

Hydrogen  sulphide  .     .  J       uble  in  ammonium  sulphide  containing  excess 
Ammonium  sulphide     .  1       of  sulphur,  and  reprecipitated  by  acids  as 

yellow  bisulphide. 
Stannic  salts  give  with  : 

Fixed  caustic  alkalies:  white  hydrate,  soluble  in  excess. 
Ammonia:  white  hydrate,  slightly  soluble  in  excess. 
Alkaline  carbonates:  white  hydrate,  slightly  soluble  in  excess. 
Ammonium  carbonate:  white  hydrate,  insoluble. 
Hydrogen  sulphide :  yellow  precipitate  of  bisulphide. 
Ammonium  sulphide:  the  same,  soluble  in  excess. 

Trichloride  of  gold,  added  to  a  dilute  solution  of  stannous  chloride,  gives 
rise  to  a  brownish-purple  precipitate,  called  purple  of  Cassius  (p.  371). 

The  useful  applications  of  tin  are  very  numerous.  Tinned  plate  consists 
of  iron  superficially  alloyed  with  this  metal ;  pewter,  of  the  best  kind,  is 
chiefly  tin,  hardened  by  the  admixture  of  a  little  antimony,  &c.  Cooking- 

*  Richardson  and  Watts's  Chemical  Technology,  vol.  i.  pt.  iv.  p.  35,  and  pt.  v.  p.  342. 


TITANIUM.  393 

vessels  of  copper  are  visually  tinned  in  the  interior.     The  use  of  tin  solu- 
tions in  dyeing  and  calico-printing  has  been  already  mentioned. 


TITANIUM. 
Atomic  weight,  50.     Symbol,  Ti. 

This  is  one  of  the  rarer  metals,  and  is  never  found  in  the  metallic  state. 
The  most  important  titanium  minerals  are  rutile,  brookite,  and  anatase,  which 
are  different  forms  of  titanic  oxide,  and  the  several  varieties  of  titaniferous 
iron,  consisting  of  ferrous  titanate,  sometimes  alone,  but  more  generally 
mixed  with  ferric  or  ferroso-ferric  oxide.  Occasionally  in  the  slag  adhering 
to  the  bottom  of  blast-furnaces  in  which  iron  ore  is  reduced,  small  brilliant 
copper-colored  cubes,  hard  enough  to  scratch  glass,  and  in  the  highest 
degree  infusible,  are  found.  This  substance,  of  which  a  single  smelting 
furnace  in  the  Hartz  produced  as  much  as  80  pounds,  was  formerly  believed 
to  be  metallic  titanium.  Recent  researches  of  Wohler,  however,  have 
shown  it  to  be  a  combination  of  titanium  cyanide  with  titanium  nitride. 
When  these  crystals  are  powdered,  mixed  with  potassium  hydrate,  and 
fused,  ammonia  is  evolved,  and  potassium  titanate  is  formed.  Metallic 
titanium  in  a  finely  divided  state  may  be  obtained  by  heating  titanium  and 
potassium  fluoride  with  potassium.  This  element  is  remarkable  for  its 
affinity  for  nitrogen :  when  heated  in  the  air,  it  simultaneously  absorbs 
oxygen  and  nitrogen. 

Titanium  is  tetradic,  like  tin,  and  forms  two  classes  of  compounds :  the 
titanic  compounds,  in  which  it  is  quadrivalent,  e.g.  TiivCl4,  Tiiv02,  and  the 
titanous  compounds,  in  which  it  is  apparently  trivalent  but  really  also 
quadrivalent,  e.  g. : 

TiCL 
TiaCl6,  or  | 

TiClg. 

CHLORIDES.  —  Titanous  chloride,  T52C16,  is  produced  by  passing  the  vapor 
of  titanic  chloride  mixed  with  hydrogen  through  a  red-hot  tube;  it  forms 
dark  violet  scales  having  a  strong  lustre.  Titanic  chloride,  TiCl4,  is  prepared 
by  passing  chlorine  over  an  ignited  mixture  of  titanic  oxide  and  charcoal. 
It  is  a  colorless  volatile  fuming  liquid,  having  a  specific  gravity  of  1-7609 
at  0°,  vapor  density  =•  6-658,  and  boiling  at  135°.  It  unites  very  violently 
with  water,  and  forms  definite  compounds  with  ammonia,  ammonium  chlor- 
ide, hydrogen  cyanide,  cyanogen  chloride,  phosphine,  and  sulphur  tetra- 
chloride. 

FLUORIDES.  —  Titanous  fluoride,  Ti.2F6,  is  obtained  as  a  violet  powder  by 
igniting  potassio-titanic  fluoride  in  hydrogen  gas,  and  treating  the  resulting 
mass  with  hot  water.  Titanic  fluoride,  TiF4,  passes  over  as  a  fuming  color- 
less liquid,  when  titanic  oxide  is  distilled  with  fluor-spar  and  fuming  sul- 
phuric acid  in  a  platinum  apparatus.  It  unites  with  hydrofluoric  acid  and 
metallic  fluorides,  forming  double  salts  called  titano-fluorides  or  fluotitanmiti'*, 
isomorphous  with  the  silicofluorides,  zircofluorides,  &c.,  e.  g.,  TiF4.lMvF ; 
TiF4.CaF2. 

OXIDES.  — The  scsquioxide,  or  Titanous  oxide,  Ti203,  is  obtained  by  igniting 
the  dioxide  in  hydrogen,  as  a  black  powder,  which,  when  heated  in  the  air 
to  a  very  high  temperature,  oxidizes  to  titanic  oxide. 

The  dioxide  or  Titanic  oxide  occurs  native  in  three  different  forms,  viz.,  as 
rutile  and  anatase,  which  are  dimetric,  and  brookite,  which  is  trimetric; 
of  these,  anatase  is  the  purest,  and  rutile  the  most  abundant.  To  obtain 


394  TETRAD    METALS. 

pure  titanic  oxide,  rutile  or  titaniferous  iron  ore,  reduced  to  fine  powder, 
is  fused  with  twice  its  weight  of  potassium  carbonate,  and  the  fused  mass 
is  dissolved  in  dilute  hydrofluoric  acid,  whereupon  titano-fluoride  of  potas- 
sium soon  begins  to  separate.  From  the  hot  aqueous  solution  of  this  salt, 
ammonia  throws  down  snow-white  ammonium  titanate,  which  is  easily 
soluble  in  hydrochloric  acid,  and  when  ignited  gives  reddish-brown  lumps 
of  titanic  oxide.  This  oxide  is  insoluble  in  water,  and  in  all  acids  except 
strong  sulphuric  acid.  By  fusing  it  with  six  times  its  weight  of  acid  potas- 
sium sulphate,  a  clear  yellow  mass  is  obtained,  which  dissolves  perfectly  in 
warm  water. 

Titanic  oxide  appears  to  form  two  hydrates  or  acids,  analogous  to  stannic 
and  metastannic  acids.  One  of  these,  called  titanic  acid,  is  precipitated  by 
ammonia  from  a  solution  of  titanic  chloride,  as  a  white  powder  which  dis- 
solves easily  in  sulphuric,  nitric,  and  hydrochloric  acids,  even  when  these 
acids  are  rather  dilute ;  but  these  dilute  solutions,  when  boiled,  deposit 
metatitanic  hydrate,  as  a  soft  white  powder,  which,  like  the  anhydrous  oxide, 
is  insoluble  in  all  acids  except  strong  sulphuric  acid. 

The  tilanates  have  not  been  much  studied ;  most  of  them  may  be  repre- 
sented by  the  formulae,  Ti04M2  =  Ti02.2M20,  and  Ti03M2  =  Ti02.M20  (the 
symbol  M  denoting  a  univalent  metal).  The  titanates  of  calcium  and  iron 
occur  as  natural  minerals.  The  titanates  of  the  alkali-metals  are  formed 
by  fusing  titanic  oxide  with  alkaline  hydrates,  carbonates,  or  acid  sulphates 
—  some  of  them  also  in  the  wet  way.  When  finely  pulverized  and  levigated, 
they  dissolve  in  moderately  warm,  concentrated  hydrochloric  acid ;  but  the 
greater  part  of  the  dissolved  titanic  acid  is  precipitated  on  boiling  the 
solution  with  dilute  acids.  The  neutral  titanates  of  the  alkali-metals,  Ti03 
M2,  are  insoluble  in  water,  but  soluble  in  acids.  The  titanates  of  the 
earth-metals  and  heavy  metals  are  insoluble,  and  may  be  obtained  by  pre- 
cipitation. 

In  a  solution  of  titanic  acid  in  hydrochloric  acid,  containing  as  little  free 
acid  as  possible,  tincture  of  galls  produces  an  orange-colored  precipitate ; 
potassium  f err o cyanide,  a  dark-brown  precipitate.  Titanic  oxide  fused  with 
borax,  or  better,  with  microcosmic-salt,  in  the  inner  blowpipe  flame,  forms  a 
glass  which  is  yellow  while  hot,  but  becomes  violet  on  cooling.  The  deli- 
cacy of  the  reaction  is  much  increased  by  melting  a  little  metallic  zinc  in 
the  lead. 


GROUP  III. 
LEAD. 

Atomic  weight,  207.     Symbol,  Pb  (Plumbum). 

This  abundant  and  useful  metal  is  altogether  obtained  from  the  native 
eulphide,  or  galena,  no  other  lead-ore  being  found  in  large  quantity.  The 
reduction  is  effected  in  a  reverberatory  furnace,  into  which  the  crushed 
lead-ore  is  introduced  and  roasted  for  some  time  at  a  dull  red  heat,  by 
which  much  of  the  sulphide  becomes  changed  by  oxidation  to  sulphate. 
The  contents  of  the  furnace  are  then  thoroughly  mixed,  and  the  tempera- 
ture raised,  when  the  sulphate  and  sulphide  react  upon  each  other,  pro- 
ducing sulphurous  oxide  and  metallic  lead : 

S04Pb   +   PbS  =r  Pb2   +   2S02. 

Lead  melts  at  315-5°  C.  (000°  F.),  or  a  little  above,  and  boils  and  volatilizes 
at  a  white  heat.  By  slow  cooling  it  may  be  obtained  in  octohedral  crystals. 
In  moist  air  this  metal  becomes  coated  with  a  film  of  gray  matter,  thought 


LEAD.  395 

to  be  suboxide,  and  when  exposed  to  the  atmosphere  in  the  melted  state  it 
rapidly  absorbs  oxygen.  Dilute  acids,  with  the  exception  of  nitric  acid, 
act  but  slowly  upon  lead. 

Lead  is  a  tetrad,  as  shown  by  the  constitution  of  plumbic  ethide,  PbiT(C2 
Hs)4;  but  in  its  inorganic  combinations  it  appears  dyadic,  forming  but  one 
chloride,  Pb//Cl;2,  with  corresponding  bromide  and  iodide.  The  oxide  cor- 
responding to  these  is  Pb/X0,  and  there  are  also  higher  oxides  in  which  the 
metal  may  be  regarded  either  as  a  dyad  or  as  a  tetrad:  thus  the  dioxide 
Pb02  may  be  formulated  either  as 

=  Pb  =  0,  or  as 

LEAD  CHLORIDE,  PbCl2,  is  prepared  by  precipitating  a  solution  of  lead 
nitrate  or  acetate  with  hydrochloric  acid  or  common  salt.  It  separates  as 
a  heavy  white  crystalline  precipitate,  which  dissolves  in  about  33  parts  of 
boiling  water,  and  separates  again,  on  cooling,  in  needle-shaped  crystals. 

There  are  several  oxychlorides  of  lead,  one  of  which,  Pb3Cl202,  or  PbCl2. 
2PbO,  occurs  crystallized  in  right  rhombic  prisms  on  the  Mendip  Hills, 
thence  called  mendipite.  Another,  constituting  Pattinson's  white  oxychlor- 
ide,  Pb2Cl20  or  PbCl2.PbO,  is  prepared  for  use  as  a  pigment  by  grinding 
galena  with  strong  hydrochloric  acid,  dissolving  the  resulting  chloride  in 
hot  water,  and  precipitating  with  lime-water.  A  third  oxychloride,  PbCl2 . 
7PbO,  called  patent  yellow  or  Turner's  yellow,  is  prepared  by  heating  1  part 
of  sal-ammoniac  with  10  parts  of  litharge. 

LEAD  IODIDE,  PbI2,  is  precipitated,  on  mixing  lead  nitrate  or  acetate 
with  potassium  iodide,  as  a  bright  yellow  powder,  which  dissolves  in  boiling 
water,  and  crystallizes  therefrom  in  beautiful  yellow  iridescent  spangles. 

OXIDES.  —  The  monoxide,  PbO,  called  litharge  or  massicot,  is  the  product 
of  the  direct  oxidation  of  the  metal.  It  is  most  conveniently  prepared  by 
heating  the  carbonate  to  dull  redness;  common  litharge  is  impure  monoxide 
which  has  undergone  fusion.  Lead  oxide  has  a  delicate  straw-yellow  color, 
is  very  heavy,  and  slightly  soluble  in  water,  giving  an  alkaline  liquid.  It 
is  soluble  in  potash,  and  crystallizes  from  the  solution  in  rhombic  prisms. 
At  a  red  heat  it  melts,  and  tends  to  crystallize  on  cooling.  In  the  melted 
state  it  attacks  and  dissolves  siliceous  matter  with  astonishing  facility,  often 
penetrating  an  earthen  crucible  in  a  few  minutes.  It  is  easily  reduced 
when  heated  with  organic  substances  of  any  kind  containing  carbon  or 
hydrogen.  It  forms  a  large  class  of  salts,  often  called  plumbic  salts,  which 
are  colorless  if  the  acid  itself  is  not  colored. 

Triplumbic  tetroxide,  or  Red  lead,  is  not  of  very  constant  composition,  but 
generally  contains  Pb302  or  2PbO.Pb02.  It  is  prepared  by  exposing  the 
monoxide,  which  has  not  been  fused,  for  a  long  time  to  the  air,  at  a  very 
faint  red  heat;  it  is  .a  brilliant  red  and  extremely  heavy  powder,  decom- 
posed, with  evolution  of  oxygen,  by  a  strong  heat,  and  converted  into  a 
mixture  of  monoxide  and  dioxide  by  acids.  It  is  used  as  a  cheap  substitute 
for  vermilion. 

The  dioxide,  Pb02,  often  called  puce  or  brown  lead-oxide,  is  obtained  without 
difficulty  by  digesting  red  lead  in  dilute  nitric  acid,  whereby  lead  nitrate  is 
dissolved  out,  and  insoluble  dioxide  left  behind  in  the  form  of  a  deep-brown 
powder.  The  dioxide  is  decomposed  by  a  red  heat,  yielding  up  one  half 
of  its  oxygen.  Hydrochloric  acid  converts  it  into  lead  chloride,  with  dis- 
engagement of  chlorine ;  hot  oil  of  vitriol  forms  with  it  lead  sulphate,  and 
liberates  oxygen.  The  dioxide  is  very  useful  in  separating  sulphurous  acid 
from  certain  gaseous  mixtures,  lead  sulphate  being  then  produced :  PbO? 
+  S03  =  PbS04. 


396  TETRAD    METALS. 

Diplumbic  oxide,  or  Lead  sub  oxide,  Pb20  or  Pb — 0 — Pb,  is  formed  when  the 
monoxide  is  heated  to  dull  redness  in  a  retort;  a  gray  pulverulent  sub- 
stance is  then  left,  which  is  resolved  by  acids  into  monoxide  and  metal.  It 
absorbs  oxygen  with  great  rapidity  when  heated,  and  even  when  simply 
moistened  with  water  and  exposed  to  the  air. 

LEAD  NITRATE,  (N03)2Pb  or  N205  PbO,  may  be  obtained  by  dissolving 
lead  carbonate  in  nitric  acid,  or  by  acting  directly  upon  the  metal  by  the 
same  agent  with  the  aid  of  heat:  it  is,  as  already  noticed,  a  by-product 
in  the  preparation  of  the  dioxide.  It  crystallizes  in  anhydrous  octohedrons, 
which  are  usually  milk-white  and  opaque.  It  dissolves  in  7J  parts  of  cold 
water,  and  is  decomposed  by  heat,  yielding  nitrogen  tetroxide,  oxygen,  and 
lead  monoxide,  which  obstinately  retains  traces  of  nitrogen.  When  a 
solution  of  this  salt  is  boiled  with  an  additional  quantity  of  lead  oxide,  a 
portion  of  the  latter  is  dissolved,  and  a  basic  nitrate  is  generated,  which 
may  be  obtained  in  crystals.  Carbonic  acid  separates  this  excess  of  oxide 
in  the  form  of  a  white  compound  of  lead  carbonate  and  lead  hydrate. 

Neutral  and  basic  compounds  of  lead  oxide  with  the  trioxide  and  tetroxide 
of  nitrogen,  have  been  described.  These  last  are  probably  formed  by  the 
combination  of  a  nitrite  with  a  nitrate. 

LEAD  CARBONATE  ;  WHITE  LEAD  ;  C03Pbx/  or  C02PbO. — This  salt  is  some- 
times found  beautifully  crystallized  in  long  white  needles,  accompanying 
other  metallic  ores.  It  may  be  prepared  artificially  by  precipitating  in  the 
cold  a  solution  of  the  nitrate  or  acetate  with  an  alkaline  carbonate :  when 
the  lead  solution  is  boiling,  the  precipitate  is  a  basic  salt  containing 
2C03Pb.  PbH202 ;  it  is  also  manufactured  to  an  immense  extent  by  other 
means  for  the  use  of  the  painter.  Pure  lead  carbonate  is  a  soft,  white 
powder,  of  great  specific  gravity,  insoluble  in  water,  but  easily  dissolved 
by  dilute  nitric  or  acetic  acid. 

Of  the  many  methods  put  in  practice,  or  proposed,  for  making  white 
lead,  the  two  following  are  the  most  important  and  interesting  :  One  of 
these  consists  in  forming  a  basic  nitrate  or  acetate  of  lead  by  boiling  finely 
powdered  litharge  with  the  neutral  salt.  This  solution  is  then  brought  into 
contact  with  carbonic  acid  gas,  whereby  all  the  excess  of  oxide  previously 
taken  up  by  the  neutral  salt  is  at  once  precipitated  as  white  lead.  The 
solution  strained  or  pressed  from  the  latter  is  again  boiled  with  litharge, 
and  treated  with  carbonic  acid:  these  processes  are  susceptible  of  indefinite 
repetition,  whereby  the  little  loss  of  neutral  salt  left  in  the  precipitates  is 
compensated.  The  second,  and  by  far  the  more  ancient  method,  is  rather 
more  complex,  and  at  first  sight  not  very  intelligible.  A  great  number  of 
earthen  jars  are  prepared,  into  each  of  which  is  poured  a  few  ounces  of 
crude  vinegar ;  a  roll  of  sheet-lead  is  then  introduced  in  such  a  manner  that 
it  shall  neither  touch  the  vinegar  nor  project  above  the  top  of  the  jar.  The 
vessels  are  next  arranged  in  a  large  building,  side  by  side,  upon  a  layer  of 
stable  manure,  or,  still  better,  spent  tan,  and  closely  covered  with  boards. 
A  second  layer  of  tan  is  spread  upon  the  top  of  the  latter,  and  then  a 
second  series  of  pots ;  these  are  in  turn  covered  with  boards  and  decom- 
posing bark,  and  in  this  manner  a  pile  of  many  alternations  is  constructed. 
After  the  lapse  of  a  considerable  time,  the  pile  is  taken  down  and  the  sheets 
of  lead  are  removed  and  carefully  unrolled ;  they  are  then  found  to  be  in 
great  part  converted  into  carbonate,  which  merely  requires  washing  and 
grinding  to  be  fit  for  use.  The  nature  of  this  curious  process  is  generally 
explained  by  supposing  the  vapor  of  vinegar  raised  by  the  high  tempera- 
ture of  the  fermenting  matter,  merely  to  act  as  a  carrier  between  the  car- 
bonic acid  evolved  from  the  tan,  and  the  lead  oxide  formed  under  the  in- 
fluence of  the  acid  vapor,  a  neutral  acetate,  a  basic  acetate,  and  a  carbonate 


IROX.  397 

"being  produced  in  succession,  and  the  action  gradually  travelling  from  the 
surface  inwards.  The  quantity  of  acetic  acid  used  is,  in  relation  to  the 
lead,  quite  trilling,  and  cannot  directly  contribute  to  the  production  of  the 
carbonate.  A  preference  is  still  given  to  the  product  of  this  old  mode  of 
manufacture,  on  account  of  its  superiority  of  opacity,  or  body,  over  that 
obtained  by  precipitation.  Commercial  white  lead,  however  prepared, 
always  contains  a  certain  proportion  of  hydrate.  It  is  sometimes  adul- 
terated with  barium  sulphate. 

When  clean  metallic  lead  is  put  into  pure  water  and  exposed  to  the  air,  a 
white,  crystalline,  scaly  powder  begins  to  show  itself  in  a  few  hours,  and 
very  rapidly  increases  in  quantity.  This  substance  may  consist  of  lead 
hydrate,  formed  by  the  action  of  the  oxygen  dissolved  in  the  water  upon 
the  lead.  It  is  slightly  soluble,  and  may  be  readily  detected  in  the  water. 
In  most  cases,  however,  the  formation  of  this  deposit  is  due  to  the  action 
of  the  carbonic  acid  dissolved  in  the  water:  it  consists  of  carbonate  in 
combination  with  hydrate,  and  is  nearly  insoluble  in  water.  When  common 
river  or  spring  water  is  substituted  for  the  pure  liquid,  this  eifect  is  less 
observable,  the  little  sulphate,  almost  invariably  present,  causing  the  depo- 
sition of  a  very  thin  but  closely  adherent  film  of  lead  sulphate  upon  the 
surface  of  the  metal,  which  protects  it  from  further  action.  It  is  on  this 
account  that  leaden  cisterns  are  used  with  impunity,  at  least  in  most  cases, 
for  holding  water:  if  the  latter  were  quite  pure,  it  would  be  speedily  con- 
taminated with  lead,  and  the  cistern  would  be  soon  destroyed.  Natural 
water  highly  charged  with  carbonic  acid  cannot,  under  any  circumstances, 
be  kept  in  lead  or  passed  through  leaden  pipes  with  safety,  the  carbonate, 
though  very  insoluble  in  pure  water,  being  slightly  soluble  in  water  con- 
taining carbonic  acid. 

The  soluble  salts  of  lead  behave  with  reagents  as  follows :  — 
Caustic  potash  and  soda  precipitate  a  white  hydrate  freely  soluble  in  ex- 
cess. Ammonia  gives  a  similar  white  precipitate,  not  soluble  in  excess. 
The  carbonates  of  potassium,  sodium,  and  ammonium,  precipitate  lead  car- 
bonate, insoluble  in  excess.  Sulphuric  acid  or  a  sulphate  causes  a  white  pre- 
cipitate of  lead  sulphate  insohible  in  nitric  acid.  Hydrogen  sulphide  and 
ammonium  sulphide  throw  down  black  lead  sulphide.  Lead  is  readily  de- 
tected before  the  blowpipe  by  fusing  the  compound  under  examination  on 
charcoal  with  sodium  carbonate,  when  a  bead  of  metal  is  easily  obtained, 
which  is  recognized  by  its  chemical  as  well  as  physical  properties. 


An  alloy  of  2  parts  of  lead  and  1  of  tin  constitutes  plumbers'  solder;  these 
proportions  reversed  give  a  more  fusible  compound,  called  fine  solder.  The 
lead  employed  in  the  manufacture  of  shot  is  combined  with  a  little  arsenic. 


GROUP  IV.  — IRON  METALS. 

IKON. 

Atomic  weight,  56.     Symbol,  Fe  (Ferrum). 

This  is  the  most  important  of  all  metals:  there  are  few  substances  to 
which  it  yields  in  interest,  when  it  is  considered  how  very  intimately  the 
knowledge  of  its  properties  and  uses  is  connected  with  human  civilisation. 

Metallic  iron  is  of  exceedingly  rare  occurrence :  it  has  been  found  at  Canaan, 
in  Connecticut,*  forming  a  vein  about  two  inches  thick  in  mica-slate  ;  but  it 

*  Phillips'  Mineralogy,  4th  edit.  p.  208. 
84 


398  TETRAD    METALS. 

invariably  enters  into  the  composition  of  those  extraordinary  stones  known 
to  fall  from  the  air,  called  meteorites.  Isolated  masses  of  soft  malleable  iron 
also,  of  large  dimensions,  lie  loose  upon  the  surface  of  the  earth  in  South 
America  and  elsewhere,  and  are  presumed  to  have  had  a  similar  origin: 
these  latter,  in  common  with  the  iron  of  the  undoubted  meteorites,  contain 
nickel.  In  an  oxidized  condition,  the  presence  of  iron  may  be  said  to  be 
universal:  it  constitutes  a  great  part  of  the  common  coloring  matter  of 
rocks  and  soils;  it  is  contained  in  plants,  and  forms  an  essential  component 
of  the  blood  of  the  animal  body.  It  is  also  very  common  in  the  state  of 
bisulphide.  Pure  iron  may  be  prepared,  according  to  Mitscherlich,  by 
introducing  into  a  Hessian  crucible  4  parts  of  fine  iron  wire  cut  small,  and 
1  part  of  black  iron  oxide.  This  is  covered  with  a  mixture  of  white  sand, 
lime,  and  potassium  carbonate,  in  the  proportions  used  for  glass-making, 
and  a  cover  being  closely  applied,  the  crucible  is  exposed  to  a  very  high 
degree  of  heat.  A  button  of  pure  metal  is  thus  obtained,  the  traces  of  car- 
bon and  silicium  present  in  the  wire  having  been  removed  by  the  oxygen 
of  the  oxide. 

Pure  iron  has  a  white  color  and  perfect  lustre  :  it  is  extremely  soft  and 
tough,  and  has  a  specific  gravity  of  7-8.  Its  crystalline  form  is  probably 
the  cube,  to  judge  from  appearances  now  and  then  exhibited.  In  good  bar- 
iron  or  wire,  a  distinct  fibrous  texture  may  always  be  observed  when  the 
metal  has  been  attacked  by  rusting  or  by  the  application  of  an  acid,  and 
upon  the  perfection  of  this  fibre  much  of  its  strength  and  value  depends. 
Iron  is  the  most  tenacious  of  all  the  metals,  a  wire  ^  of  an  inch  in  diame- 
ter bearing  a  weight  of  GO  Ibs.  It  is  very  difficult  of  fusion,  and  before 
becoming  liquid  passes  through  a  soft  or  pasty  condition.  Pieces  of  iron 
pressed  or  hammered  together  in  this  state  cohere  into  a  single  mass  :  the 
operation  is  termed  welding,  and  is  usually  performed  by  sprinkling  a  little 
sand  over  the  heated  metal,  which  combines  with  the  superficial  film  of 
oxide,  forming  a  fusible  silicate,  which  is  subsequently  forced  out  from 
between  the  pieces  of  iron  by  the  pressure  applied :  clean  surfaces  of  metal 
are  thus  presented  to  each  other,  and  union  takes  place  without  difficulty. 

Iron  does  not  oxidize  in  dry  air  at  common  temperatures:  heated  to  red- 
ness, it  becomes  covered  with  a  scaly  coating  of  black  oxide,  and  at  a  high 
white  heat  burns  brilliantly,  producing  the  same  substance.  In  oxygen  gas 
the  combustion  occurs  with  still  greater  ease.  The  finely  divided  spongy 
metal  prepared  by  reducing  the  red  oxide  with  hydrogen  gas  takes  fire 
spontaneously  in  the  air.  Pure  water,  free  from  air  and  carbonic  acid,  does 
not  tarnish  a  surface  of  polished  iron,  but  the  combined  agency  of  free 
oxygen  and  moisture  speedily  leads  to  the  production  of  rust,  which  is  a 
hydrate  of  the  sesquioxide.  The  rusting  of  iron  is  wonderfully  promoted 
by  the  presence  of  a  little  acid  vapor.  At  a  red  heat,  iron  decomposes 
water,  evolving  hydrogen,  and  passing  into  the  black  oxide.  Dilute  sul- 
phuric and  hydrochloric  acids  dissolve  it  freely,  with  separation  of  hydro- 
gen. Iron  is  strongly  magnetic  up  to  a  red  heat,  when  it  loses  all  traces  of 
that  remarkable  property. 

Iron  is  a  tetrad,  forming  two  classes  of  compounds;  namely,  ike  ferrous 
compounds,  in  which  it  is  bivalent,  e.g.,  Fe^CLj,  Fex/0,  Fe/xS04,  £c.,  and 
the  ferric  compounds,  in  which  it  is  really  quadrivalent,  though  apparently 

Fe'"Cl, 

r    I  ;  Fe"'203;  Fe'^JSOA,  &c. 

Fe'"Cl3 

CHLORIDES.  —The  dicMoride,  or  Ferrous  chloride,  FeCl3,  is  formed  by  trans- 
mitting dry  hydrochloric  acid  gas  over  red-hot  metallic  iron,  or  by  dissolv- 
ing iron  in  hydrochloric  acid.  The  latter  solution  yields,  when  duly  con- 
centrated, green  crystals  of  the  hydrated  dichloride  FeC12.40H2;  they  are 
very  soluble  and  deliquescent,  and  rapidly  oxidize  in  the  air. 


IRON.  399 

The  trichloride,  or  Ferric  chloride,  Fe2Cl6,  is  usually  prepared  by  dissolving 
ferric  oxide  in  hydrochloric  acid.  The  solution,  evaporated  to  a  syrupy 
consistence,  deposits  red  hydrated  crystals,  which  are  very  soluble  in  water 
and  alcohol.  It  forms  double  salts  with  potassium  chloride  and  sal-ammo- 
niac. When  evaporated  to  dry  ness  and  strongly  heated,  much  of  the  chlor- 
ide is  decomposed,  yielding  sesquioxide  and  hydrochloric  acid  :  the  remain- 
der sublimes,  and  afterwards  condenses  in  the  form  of  small  brilliant  red 
crystals,  which  deliquesce  rapidly.  Anhydrous  ferric  chloride  is  also  pro- 
duced by  the  action  of  chlorine  upon  the  heated  metal.  The  solution  of 
ferric  chloride  is  capable  of  dissolving  a  large  excess  of  recently  precipi- 
tated ferric  hydrate,  by  which  it  acquires  a  much  darker  color. 

IODIDES.  —  Ferrous  iodide,  FeI2,  is  an  important  medicinal  preparation:  it 
is  easily  made  by  digesting  iodine  with  water  and  metallic  iron.  The  solution 
is  pale-green,  and  yields,  on  evaporation,  crystals  resembling  those  of  the 
chloride,  which  rapidly  oxidize  on  exposure  to  air.  It  is  best  preserved  in 
solution  in  contact  with  excess  of  iron.  —  Ferric  iodide,  Fe2I6,  is  yellowish- 
red  and  soluble. 

IRON  OXIDES.  —  Three  oxides  of  iron  are  known,  namely,  ferrous  oxide, 
FeO,  and  ferric  oxide,  Fe203,  analogous  to  the  chlorides,  and  an  intermi- 
diate  oxide,  usually  called  magnetic  iron  oxide,  containing  Fe304,  or  FeO. 
Fe203.  A  trioxide,  Fe03,  is  supposed  to  exist  in  a  class  of  salts  called  fer- 
rates, but  it  has  not  been  isolated. 

Monoxide  or  Ferrous  oxide,  FeO.  — This  is  a  very  powerful  base,  neutraliz- 
ing acids,  and  isomorphous  with  magnesia,  zinc  oxide,  &c.  It  is  almost 
unknown  in  the  separate  state,  from  its  extreme  proneness  to  absorb  oxy- 
gen and  pass  into  the  sesquioxide.  When  a  ferrous  salt  is  mixed  with 
caustic  alkali  or  ammonia,  a  bulky  whitish  precipitate  of  ferrous  hydrate 
falls,  which  becomes  nearly  black  when  boiled,  the  water  being  separated. 
This  hydrate  changes  very  rapidly  when  exposed  to  the  air,  becoming  green 
and  ultimately  red-brown.  The  soluble  ferrous  salts  have  commonly  a 
delicate  pale-green  color  and  a  nauseous  metallic  taste. 

Sesquioxide  or  Ferric  oxide,  Fe203.  —  A  feeble  base,  isomorphous  with  alu- 
mina. It  occurs  native,  most  beautifully  crystallized,  as  specular  iron  ore, 
in  the  Island  of  Elba,  and  elsewhere ;  also  as  red  and  brown  hsematite,  the 
latter  being  a  hydrate.  It  is  artificially  prepared  by  precipitating  a  solution 
of  ferric  sulphate  or  chloride  with  excess  of  ammonia,  and  washing,  dry- 
ing, and  igniting  the  yellowish-brown  hydrate  thus  produced ;  fixed  alkali 
must  not  be  used  in  this  operation,  as  a  portion  is  retained  by  the  oxide. 
In  fine  powder,  this  oxide  has  a  full  red  color,  and  is  used  as  a  pigment, 
being  prepared  for  the  purpose  by  calcination  of  ferrous  sulphate;  the  tint 
varies  somewhat  with  the  temperature  to  which  it  has  been  exposed.  The 
oxide  is  unaltered  in  the  fire,  although  easily  reduced  at  a  high  temperature 
by  carbon  or  hydrogen.  It  dissolves  in  acids,  with  difficulty  after  strong 
ignition,  forming  a  series  of  reddish  salts,  which  have  an  acid  reaction  and 
an  astringent  taste.  Ferric  oxide  is  not  acted  upon  by  the  magnet. 

Triferro-tetroxide,  Ferrosoferric  oxide,  Fe304  =  FeO.Fe2O3,  also  called  black 
iron  oxide,  magnetic  oxide,  and  loadstone. — A  natural  product,  one  of  the 
most  valuable  of  the  iron  ores,  often  found  in  regular  octohedral  crystals, 
which  are  magnetic.  It  may  be  prepared  by  mixing  due  proportions  of 
ferrous  and  ferric  salts,  precipitating  them  with  excess  of  alkali,  and  then 
boiling  the  mixed  hydrates ;  the  latter  then  unite  to  a  black  sandy  sub- 
stance, consisting  of  minute  crystals  of  the  magnetic  oxide.  This  oxide  is 
the  chief  product  of  the  oxidation  of  iron  at  a  high  temperature  in  the  air 
and  in  aqueous  vapor.  It  is  incapable  of  forming  definite  salts. 

FERRATES.  —  When  a  mixture  of  one  part  of  pure  ferric  oxide  and  four 


400  TETKAD   METALS. 

parts  of  dry  nitre  is  heated  to  full  redness  for  an  hour  in  a  covered  cruci- 
ble, and  the  resulting  brown,  porous,  deliquescent  mass  is  treated  when 
cold  with  ice-cold  water,  a  deep  amethystine-red  solution  of  potassium  fer- 
rate is  obtained.  The  same  salt  may  be  more  easily  prepared  by  passing 
chlorine  gas  through  a  strong  solution  of  potash  in  which  recently  precipi- 
tated ferric  hydrate  is  suspended ;  it  is  then  deposited  as  a  black  powder, 
which  may  be  drained  upon  a  tile.  It  consists  of  Fe04K2  or  Fe03.OK2. 
The  solution  of  the  salt  gradually  decomposes,  even  in  the  cold,  and  rapidly 
when  heated,  giving  off  oxygen  and  depositing  sesquioxide.  The  solution 
of  potassium  ferrate  gives  no  precipitate  with  salts  of  calcium,  magnesium, 
or  strontium,  but  when  mixed  with  a  barium  salt,  it  yields  a  deep  crimson, 
insoluble,  barium  ferrate,  Fe04Ba,  or  Fe03.BaO,  which  is  very  permanent. 
Neither  the  hydrogen  salt  nor  ferric  acid,  Fe04H2,  nor  the  corresponding 
anhydrous  oxide,  Fe03,  is  known  in  the  separate  state. 

FERROUS  SULPHATE,  S04Fe//.70H2,  S03.Fe0.70H2.  —  This  beautiful  and 
important  salt,  commonly  called  green  vitriol,  iron  vitriol,  or  copperas,  may  be 
obtained  by  dissolving  iron  in  dilute  sulphuric  acid :  it  is  generally  prepared, 
however,  and  on  a  very  large  scale,  by  contact  of  air  and  moisture 
with  common  iron  pyrites,  which,  by  absorption  of  oxygen,  readily  fur- 
nishes the  substance  in  question.  Heaps  of  this  material  are  exposed  to 
the  air  until  the  decomposition  is  sufficiently  advanced :  the  salt  produced 
is  then  dissolved  out  by  water,  and  the  solution  made  to  crystallize.  It 
forms  large  green  crystals,  of  the  composition  above  stated,  which  slowly 
effloresce  and  oxidize  in  the  air:  it  is  soluble  in  about  twice  its  weight  of 
cold  water.  Crystals  containing  4  and  also  2  molecules  of  water  have  been 
obtained.  Ferrous  sulphate  forms  double  salts  with  the  sulphates  of  potas- 
sium and  ammonium,  containing  (S04)2Fex/K2.60H2,  and  (S04)2Fe"(NH4)a. 
60H2,  isomorphous  with  the  corresponding  magnesium  salts. 

FERRIC  SULPHATE,  (S04)3Fe///2,  or  3S03.Fe203,  is  prepared  by  adding  to 
a  solution  of  the  ferrous  salt  exactly  one  half  as  much  sulphuric  acid  as  it 
already  contains,  raising  the  liquid  to  the  boiling-point,  and  then  dropping 
in  nitric  acid  until  the  solution  ceases  to  blacken  by  such  addition.  The 
red  liquid  thus  obtained  furnishes,  on  evaporation  to  dryness,  a  buff-colored 
amorphous  mass,  which  dissolves  very  slowly  when  put  into  water.  With 
the  sulphates  of  potassium  and  ammonium,  this  salt  yields  compounds  hav- 
ing the  form  and  constitution  of  alums ;  the  potassium  salt,  for  example, 
has  the  composition  (S04)2Fe/x/K.  120H2.  The  crystals  are  nearly  destitute 
of  color ;  they  are  decomposed  by  water,  and  sometimes  by  long  keeping 
in  the  dry  state.  These  salts  are  best  prepared  by  exposing  to  spontaneous 
evaporation  a  solution  of  ferric  sulphate  to  which  potassium  or  ammonium 
sulphate  has  been  added. 

FERROUS  NITRATE  (N03)2Fe//.  —  When  dilute  cold  nitric  acid  is  made  to 
act  to  saturation  upon  iron  monosulphide,  and  the  solution  is  evaporated 
in  a  vacuum,  pale-green  and  very  soluble  crystals  of  ferrous  nitrate  are 
obtained,  which  are  very  subject  to  alteration.  Ferric  nitrate  is  readily 
formed  by  pouring  nitric  acid,  slightly  diluted,  upon  iron :  it  is  a  deep-red 
liquid,  apt  to  deposit  an  insoluble  basic  salt,  and  is  used  in  dyeing. 

FERROUS  CARBONATE,  CO^Fe"  or  C02.Fe//0.  —  The  whitish  precipitate 
obtained  by  mixing  solutions  of  ferrous  salt  and  alkaline  carbonate :  it 
cannot  be  washed  and  dried  without  losing  carbonic  acid  and  absorbing 
oxygen.  This  substance  occurs  in  nature  as  spathose  iron  ore,  or  iron  spar, 
associated  with  variable  quantities  of  calcium  and  magnesium  carbonates ; 
also  in  the  common  clay  iron-stone,  from  which  nearly  all  the  British  iron 
is  made.  It  is  often  found  in  mineral  waters,  being  soluble  in  excess  of 


IRON.  401 

carbonic  acid :  such  waters  are  known  by  the  rusty  matter  they  deposit  on 
exposure  to  the  air.     No  ferric  carbonate  is  known. 
The  phosphates  of  iron  are  all  insoluble. 

IRON  SULPHIDES.  — Several  compounds  of  iron  and  sulphur  are  described: 
of  these  the  two  most  important  are  the  following.  The  monosulphide,  or 
ferrous  sulphide,  FeS,  is  a  blackish  brittle  substance,  attracted  by  the  mag- 
net, formed  by  heating  together  iron  and  sulphur.  It  is  dissolved  by  dilute 
acids,  with  evolution  of  sulphuretted  hydrogen  gas,  arid  is  constantly  em- 
ployed for  that  purpose  in  the  laboratory,  being  made  by  projecting  into  a 
red-hot  crucible  a  mixture  of  2£  parts  of  sulphur  and  4  parts  of  iron  fil- 
ings or  borings  of  cast-iron,  and  excluding  the  air  as  much  as  possible. 
The  same  substance  is  formed  when  a  bar  of  white-hot  iron  is  brought  in 
contact  with  sulphur.  The  bisulphide,  FeS2,  or  iron  pyrites,  is  a  natural 
product,  occurring  in  rocks  of  all  ages,  and  evidently  formed  in  many  cases 
by  the  gradual  deoxidation  of  ferrous  sulphate  by  organic  matter.  It  has 
a  brass-yellow  color,  is  very  hard,  not  attracted  by  the  magnet,  and  not 
acted  upon  by  dilute  acids.  When  it  is  exposed  to  heat,  sulphur  is  ex- 
pelled, and  an  intermediate  sulphide,  FesS4,  analogous  to  the  black  oxide, 
is  produced.  This  substance  also  occurs  native,  under  the  name  of  magnetic 
pyrites.  Iron  pyrites  is  the  material  now  chiefly  employed  for  the  manu- 
facture of  sulphuric  acid;  for  this  purpose  the  mineral  is  roasted  in  a  cur- 
rent of  air,  and  the  sulphurous  acid  formed  is  passed  into  the  lead  cham- 
bers ;  the  residue  consists  of  iron  oxide,  frequently  containing  a  quantity 
of  copper  large  enough  to  render  the  extraction  of  that  metal  remunerative. 

Compounds  of  iron  with  phosphorus,  carbon,  and  silicium  exist,  but  little 
is  known  respecting  them  in  a  definite  state.  The  carbonide  is  contained 
in  cast-iron  and  in  steel,  to  which  it  communicates  ready  fusibility ;  the 
silicium  compound  is  also  found  in  cast-iron.  Phosphorus  is  a  very  hurt- 
ful substance  in  bar  iron,  as  it  renders  it  brittle  or  cold-short. 

REACTIONS  OF  IRON  SALTS. — Ferrous  salts  are  thus  distinguished: 

Caustic  alkalies,  and  ammonia,  give  nearly  white  precipitates,  insoluble  in 
excess  of  the  reagent,  rapidly  becoming  green,  and  ultimately  brown,  by 
exposure  to  air.  The  carbonates  of  potassium,  sodium,  and  ammonium  throw 
down  whitish  ferrous  carbonate,  also  very  subject  to  change.  Hydrogen 
sulphide  gives  no  precipitate,  but  ammonium  sulphide  throws  down  black  fer- 
rous sulphide,  soluble  in  dilute  acids.  Potassium  ferrocyanide  gives  a  nearly 
white  precipitate,  becoming  deep-blue  on  exposure  to  air. 

Ferric  salts  are  thus  characterized : 

Caustic  fixed  alkalies  and  ammonia,  give  foxy-red  precipitates  of  ferric 
hydrate,  insoluble  in  excess. 

The  carbonates  behave  in  a  similar  manner,  the  carbonic  acid  escaping. 

Hydrogen  sulphide  gives  a  nearly  white  precipitate  of  sulphur,  and  re- 
duces the  sesquioxide  to  monoxide.  Ammonium  sulphide  gives  a  black  pre- 
cipitate, slightly  soluble  in  excess.  Potassium  ferrocyanide  yields  Prussian 
blue.  Tincture  or  infusion  of  gall-nuts  strikes  intense  bluish-black  with 
the  most  dilute  solutions  of  ferric  salts. 


Iron  Manufacture.  —  This  most  important  branch  of  industry  consists,  as 
now  conducted,  of  two  distinct  parts  —  viz.,  the  production  from  the  ore  of 
a  fusible  carbonide  of  iron,  and  the  subsequent  decomposition  of  the  car- 
bonide, and  its  conversion  into  pure  or  malleable  iron. 

The  clay-iron  ore  is  found  in  association  with  coal,  forming  thin  beds  or 
nodules  :  it  consists,  as  already  mentioned,  of  ferrous  carbonate  mixed  with 


402  TETRAD    METALS. 

clay ;  sometimes  lime  and  magnesia  are  also  present.  It  is  broken  in 
pieces,  and  exposed  to  heat  in  a  furnace  resembling  a  lime-kiln,  by  which 
the  water  and  carbonic  acid  are  expelled,  and  the  ore  rendered  dark- 
colored,  denser,  and  also  magnetic :  it  is  then  ready  for  reduction.  The 
furnace  in  which  this  operation  is  performed  is  usually  of  very  large  di- 
mensions, 50  feet  or  more  in  height,  and  constructed  of  brickwork  with 
great  solidity,  the  interior  being  lined  with  excellent  fire-bricks :  the  shape 
will  be  understood  from  the  section  shown  in  fig.  173.  The  furnace  is  close 

Fig.  173. 


at  the  bottom,  the  fire  being  maintained  by  a  powerful  artificial  blast  in- 
troduced by  two  or  tree  twyere-pipes,  as  shown  in  the  section.  The  mate- 
rials, consisting  of  due  proportions  of  coke  or  carbonized  coal,  roasted  ore, 
and  limestone,  are  constantly  supplied  from  the  top,  the  operation  proceed- 
ing continuously  night  and  day,  often  for  years,  or  until  the  furnace  is 
judged  to  require  repair.  In  the  upper  part  of  the  furnace,  where  the 
temperature  is  still  very  high,  and  where  combustible  gases  abound,  the 
iron  of  the  ore  is  probably  reduced  to  the  metallic  state,  being  disseminated 
through  the  earthy  matter  of  the  ore.  As  the  whole  sinks  down  and  attains 
a  still  higher  degree  of  heat,  the  iron  becomes  converted  into  carbonide  by 
cementation,  while  the  silica  and  alumina  unite  with  the  lime,  purposely 
added,  to  a  kind  of  glass  or  slag,  nearly  free  from  iron  oxide.  The  carbon- 
ide and  slag,  both  in  a  melted  state,  reach  at  last  the  bottom  of  the  furnace, 
where  they  arrange  themselves  in  the  order  of  their  densities :  the  slag 
flows  out  at  certain  apertures  contrived  for  the  purpose,  and  the  iron  is 
discharged  from  time  to  time,  and  sutfered  to  run  into  rude  moulds  of  sand 
by  opening  an  orifice  at  the  bottom  of  the  recipient,  previously  stopped 


IRON.  403 

with  clay.  Such  is  the  origin  of  crude  or  cast-iron,  of  which  there  are 
several  varieties,  distinguished  by  differences  of  color,  hardness,  and  com- 
position, and  known  by  the  names  of  gray,  black,  and  white  iron.  The  first 
is  for  most  purposes  the  best,  as  it  admits  of  being  filed  and  cut  with 
perfect  ease.  The  black  and  gray  kinds  probably  contain  a  mechanical 
admixture  of  graphite,  which  separates  during  solidification. 

A  great  improvement  has  been  made  in  the  above-described  process,  by 
substituting  raw  coal  for  coke,  and  blowing  hot  air  instead  of  cold  into  the 
furnace.  This  is  effected  by  causing  the  air,  on  leaving  the  blowing-machine, 
to  circulate  through  a  system  of  red-hot  iron  pipes,  until  its  temperature 
becomes  high  enough  to  melt  lead.  This  alteration  has  already  effected 
a  prodigious  saving  in  fuel,  without,  it  appears,  any  injury  to  the  quality 
of  the  product. 

The  conversion  of  cast  into  bar  iron  is  effected  chiefly  by  an  operation 
called  puddling  ;  previous  to  which,  however,  it  commonly  undergoes  a  pro- 
cess called  refining.  It  is  remelted,  in  contact  with  the  fuel,  in  small  low 
furnaces  called  refineries,  while  air  is  blown  over  its  surface  by  means  of 
twyeres.  The  effect  of  this  operation  is  to  deprive  the  iron  of  a  great  part 
of  the  carbon  and  silicium  associated  with  it.  The  metal  thus  purified  is 
run  out  into  a  trench,  and  suddenly  cooled,  by  which  it  becomes  white, 
crystalline,  and  exceedingly  hard  :  in  this  state  it  is  called  fine  metal.  The 
puddling  process  is  conducted  in  an  ordinary  reverberatory  furnace,  into 
which  the  charge  of  fine  metal  is  introduced  by  a  side  aperture.  This  is 
speedily  melted  by  the  flame,  and  its  surface  covered  with  a  crust  or  oxide. 
The  workman  then,  by  the  aid  of  an  iron  tool,  diligently  stirs  the  melted 
mass,  so  as  intimately  to  mix  the  oxide  with  the  metal:  he  now  and  then 
also  throws  in  a  little  water,  with  the  view  of  promoting  more  rapid  oxida- 
tion. Small  jets  of  blue  flame  soon  appear  upon  the  surface  of  the  iron, 
and  the  latter,  after  a  time,  begins  to  lose  its  fluidity,  and  acquires,  in 
succession,  a  pasty  and  a  granular  condition.  At  this  point  the  fire  is 
strongly  urged,  the  sandy  particles  once  more  cohere,  and  the  contents  of 
the  furnace  now  admit  of  being  formed  into  several  large  balls  or  masses, 
which  are  then  withdrawn,  and  placed  under  an  immense  hammer,  moved 
by  machinery,  by  which  each  becomes  quickly  fashioned  into  a  rude  bar. 
This  is  reheated,  and  passed  between  grooved  cast-iron  rollers,  and  drawn 
out  into  a  long  bar  or  rod.  To  make  the  best  iron,  the  bar  is  cut  into  a 
number  of  pieces,  which  are  afterwards  piled  or  bound  together,  again  raised 
to  a  welding  heat,  and  hammered  or  rolled  into  a  single  bar;  and  this  pro- 
cess of  piling  or  fagoting  is  sometimes  twice  or  thrice  repeated,  the  iron 
becoming  greatly  improved  thereby. 

The  general  nature  of  the  change  in  the  puddling  furnace  is  not  difficult 
to  explain.  Cast  iron  consists  essentially  of  iron  in  combination  with  car- 
bon and  silicium.  When  strongly  heated  with  iron  oxide,  those  compounds 
undergo  decomposition,  the  carbon  and  silicium  becoming  oxidized  at  the 
expense  of  the  oxygen  of  the  oxide.  As  this  change  takes  place,  the  metal 
gradually  loses  its  fusibility,  but  retains  a  certain  degree  of  adhesiveness, 
so  that  when  at  last  it  comes  under  the  tilt-hammer,  or  between  the  rollers, 
the  particles  of  iron  become  agglutinated  into  a  solid  mass,  while  the 
readily  fusible  silicate  of  the  oxide  is  squeezed  out  and  separated. 

All  these  processes  are,  in  Great  Britain,  performed  with  coal  or  coke ; 
but  the  iron  obtained  is,  in  many  respects,  inferior  to  that  made  in  Sweden 
and  Russia  from  the  magnetic  oxide,  by  the  use  of  wood  charcoal,  —  a  fuel 
too  dear  to  be  extensively  employed  in  England.  Plate  iron  is,  however, 
sometimes  made  with  charcoal. 

Steel.  —  A  very  remarkable  and  most  useful  substance,  prepared  by 
heating  iron  in  contact  with  charcoal.  Bars  of  Swedish  iron  are  imbedded 
in  charcoal  powder,  contained  in  a  large  rectangular  crucible  or  chest  of 


404  TETRAD    METALS. 

some  substance  capable  of  resisting  the  fire,  and  exposed  for  many  hours 
to  a  full  red  heat.  The  iron  takes  up,  under  these  circumstances,  from 
1-3  to  1-7  per  cent,  of  carbon,  becoming  harder,  and  at  the  same  time 
fusible,  with  a  certain  diminution,  however,  of  malleability.  The  active 
agent  in  this  cementation  process  is  probably  carbonic  monoxide :  the 
oxygen  of  the  air  in  the  crucible  combines  with  the  carbon  to  form  that 
substance,  which  is  afterwards  decomposed  by  the  heated  iron,  one  half  of 
its  carbon  being  abstracted  by  the  latter.  The  carbon  dioxide  thus  formed 
takes  up  an  additional  dose  of  carbon  from  the  charcoal,  and  again  becomes 
monoxide,  the  oxygen,  or  rather  the  carbon  dioxide,  acting  as  a  carrier 
between  the  charcoal  and  the  metal.  The  product  of  this  opei-ation  is 
called  blistered  steel,  from  the  blistered  and  rough  appearance  of  the  bars: 
the  texture  is  afterwards  improved  and  equalized  by  welding  a  number  of 
these  bars  together,  and  drawing  the  whole  out  under  a  light  tilt-hammer. 

Some  chemists  have  recently  asserted  that  nitrogen  is  necessary  for  the 
production  of  steel,  and  have,  in  fact,  attributed  to  its  presence  the  peculiar 
properties  of  this  material ;  others,  again,  have  disputed  this  assertion, 
and  believe  that  the  transformation  of  iron  into  steel  depends  upon  the 
assimilation  of  carbon  only ;  experimentally,  the  question  remains  un- 
decided. 

Excellent  steel  is  obtained  by  fusing  gray  cast-iron  with  tungstic  oxide ; 
the  carbon  of  the  iron  reduces  the  tungstic  oxide  to  tungsten  (p.  424), 
which  forms  with  the  iron  an  alloy  possessing  the  properties  of  steel.  The 
quantity  of  tungsten  thus  absorbed  by  the  iron  is  very  small,  and  some 
chemists  attribute  the  properties  of  the  so-called  tungsten  steel  to  the  gen- 
eral treatment  rather  than  to  the  presence  of  tungsten. 

The  most  perfect  kind  of  steel  is  that  which  has  undergone  fusion,  hav- 
ing been  cast  into  ingot-moulds,  and  afterwards  hammered:  of  this  all  fine 
cutting  instruments  are  made.  It  is  difficult  to  forge,  requiring  great  skill 
and  care  on  the  part  of  the  operator. 

Steel  may  also  be  made  directly  from  some  particular  varieties  of  cast- 
iron,  as  that  from  spathose  iron  ore  containing  a  little  manganese.  The 
metal  is  retained,  in  a  melted  state,  on  the  hearth  of  a  furnace,  while  a 
stream  of  air  plays  upon  it,  and  causes  partial  oxidation :  the  oxide  pro- 
duced reacts,  as  before  stated,  on  the  carbon  of  the  iron,  and  withdraws  a 
portion  of  that  element.  When  a  proper  degree  of  stiifness  or  pastiness 
is  observed  in  the  residual  metal,  it  is  withdrawn,  and  hammered  or  rolled 
into  bars.  The  ivootz,  or  native  steel  of  India,  is  probably  made  in  this 
manner.  Annealed  cast  iron,  sometimes  called  run-steel,  is  now  much  em- 
ployed as  a  substitute  for  the  more  costly  products  of  the  forge :  the  arti- 
cles, when  cast,  are  imbedded  in  powdered  iron  ore,  or  some  earthy  ma- 
terial, and,  after  being  exposed  to  a  moderate  red  heat  for  some  time,  are 
allowed  to  cool  slowly,  by  which  a  very  cxtraordinay  degree  of  softness  and 
malleability  is  attained.  It  is  very  possible  that  some  little  decarbonization 
may  take  place  during  this  process. 

Bessemer  steel  is  produced  by  forcing  atmospheric  air  into  melted  cast-iron. 
The  carbon  being  oxidized  more  readily  than  the  iron,  it  is  converted  into 
carbon  monoxide,  which  escapes  in  a  sufficiently  heated  state  to  take  fire 
on  coming  in  contact  with  atmospheric  air.  Considerable  heat  is  generated 
by  the  oxidation  of  the  carbon  and  iron,  so  that  the  temperature  is  kept 
above  the  melting  point  of  steel  during  the  whole  of  the  operation.  When 
the  decarburation  has  been  carried  far  enough,  the  current  of  air  is  stopped, 
and  a  small  quantity  of  white  pig-iron,  containing  a  large  amount  of  man- 
ganese, is  dropped  into  the  liquid  metal.  This  serves  to  facilitate  the  sep- 
aration of  any  gas  retained  with  the  melted  metal,  which,  after  a  few 
minutes'  rest,  is  run  into  ingot-moulds. 

The  most  remarkable  property  of  steel  is  that  of  becoming  exceedingly 


NICKEL.  405 

hard  when  quickly  cooled.  When  heated  to  redness,  and  suddenly 
quenched  in  cold  water,  steel,  in  fact,  becomes  capable  of  scratching  glass 
with  facility:  if  reheated  to  redness,  and  once  more  left  to  cool  slowly,  it 
again  becomes  nearly  as  soft  as  ordinary  iron;  and  between  these  two  con- 
ditions, any  required  degree  of  hardness  may  be  attained.  The  articles, 
forged  into  shape,  are  first  hardened  in  the  manner  described ;  they  are 
then  tempered,  or  let  down  by  exposure  to  a  proper  degree  of  annealing  heat, 
which  is  often  judged  of  by  the  color  of  the  thin  film  of  oxide  which  ap- 
pears on  the  polished  surface.  Thus,  a  temperature  of  about  221°  C. 
(430°  F.),  indicated  by  a  faint  straw  color,  gives  the  proper  temper  for 
razors:  that  for  scissors,  penknives,  &c.,  is  comprised  between  243°  C. 
(470°  F.)  and  254°  C.  (490°  F.),  and  is  indicated  by  a  full-yellow  or  brown 
tint.  Swords  and  watch-springs  require  to  be  softer  and  more  elastic,  and 
must  be  heated  to  288°  C.  (550°  F.)  or  293°  C.  (560°  F.),  or  until  the  surface 
becomes  deep  blue.  Attention  to  these  colors  has  now  become  of  less  im- 
portance, as  metal  baths  are  often  substituted  for  the  open  fire  in  this 
operation. 


NICKEL. 

Atomic  weight,  58-8.     Symbol,  Ni. 

Nickel  is  found  in  tolerable  abundance  in  some  of  the  metal-bearing 
veins  of  the  Saxon  mountains,  in  Westphalia,  Hessia,  Hungary,  and  Sweden, 
chiefly  as  arsenide,  the  kupfernickel  of  mineralogists,  so  called  from  its 
yellowish-red  color.  The  word  nickel  is  a  term  of  detraction,  having  been 
applied  by  the  old  German  miners  to  what  was  looked  upon  as  a  kind  of 
false  copper  ore. 

The  artificial,  or  perhaps  rather  merely  fused,  product,  called  speiss,  is 
nearly  the  same  substance,  and  may  be  employed  as  a  source  of  the  nickel- 
salts.  This  metal  is  found  in  meteoric  iron,  as  already  mentioned. 

Nickel  is  easily  prepared  by  exposing  the  oxalate  to  a  high  white  heat, 
in  a  crucible  lined  with  charcoal,  or  by  reducing  one  of  the  oxides  by 
means  of  hydrogen  at  a  high  temperature.  It  is  a  white,  malleable  metal, 
having  a  density  of  8-8,  a  high  melting-point,  and  a  less  degree  of  oxida- 
bility  than  iron,  since  it  is  but  little  attacked  by  dilute  acids.  Nickel  is 
strongly  magnetic,  but  loses  this  property  when  heated  to  350°. 

Nickel,  from  its  resemblance  to  iron  and  cobalt,  is  regarded  as  a  tetrad, 
although  it  forms  only  one  chloride,  in  which  it  is  bivalent,  and  no  oxygen- 
salts  analogous  to  the  ferric  salts. 

NICKEL  CHLORIDE,  Ni^Cl^ — This  compound  is  easily  prepared  by  dis- 
solving oxide  or  carbonate  of  nickel  in  hydrochloric  acid.  A  green  solu- 
tion is  obtained  which  furnishes  crystals  of  the  same  color,  containing 
water.  When  rendered  anhydrous  by  heat,  the  chloride  is  yellow,  unless 
it  contains  cobalt,  in  which  case  it  has  a  tint  of  green. 

NICKEL  OXIDES.  —  Nickel  forms  two  oxides  analogous  to  the  two  principal 
oxides  of  iron. 

The  monoxide,  Ni//0<  is  prepared  by  heating  the  nitrate  to  redness,  or  by 
precipitating  a  soluble  nickel  salt  with  caustic  potash,  and  washing,  drying, 
and  igniting  the  apple-green  hydrated  oxide  thrown  down.  It  is  an  ashy- 
gray  powder,  freely  soluble  in  acids,  which  it  completely  neutralizes,  form- 
ing salts  isomorphous  with  those  of  magnesium  and  the  other  members  of 
the  same  group.  Nickel  salts,  when  hydrated,  have  usually  a  beautiful 
emerald-green  color ;  in  the  anhydrous  state  they  are  yellow. 


406  TETRAD    METALS. 

The  sesquioxide,  Ni203,  is  a  black  insoluble  substance,  prepared  by  pass- 
ing chlorine  through  the  hydrated  monoxide  suspended  in  water ;  nickel 
chloride  is  then  formed,  and  the  oxygen  of  the  oxide  decomposed  is  trans- 
ferred to  a  second  portion.  It  is  also  produced  when  a  salt  of  nickel  is 
mixed  with  a  solution  of  bleaching-powder.  The  sesquioxide  is  decomposed 
by  heat,  and  evolves  chlorine  when  treated  with  hot  hydrochloric  acid. 

NICKEL  SULPHATE,  S04Ni.70H2. — This  is  the  most  important  of  the  nickel- 
salts.  It  forms  green  prismatic  crystals,  which  require  3  parts  of  cold  water 
for  solution.  Crystals  with  6  molecules  of  water  have  also  been  obtained. 
It  forms  with  the  sulphates  of  potassium  and  ammonium  beautiful  double 
salts,  (S04).,Ni//K.60PI2,  and  (SOJ.jNi^NHJ.GOH^  isomorphous  with  the 
corresponding  magnesium  salts. 

When  a  strong  solution  of  oxalic  acid  is  mixed  with  sulphate  of  nickel,  a 
pale  bluish-green  precipitate  of  oxalate  falls  after  some  time,  very  little 
nickel  remaining  in  solution.  The  oxalate  can  thus  be  obtained  for  pre- 
paring the  metal. 

NICKEL  CARBONATE,  C03Ni. — When  solutions  of  nickel  sulphate  or  chlor- 
ide and  of  sodium  carbonate  are  mixed,  a  pale-green  precipitate  falls,  which 
is  a  combination  of  nickel  carbonate  and  hydrate.  It  is  readily  decomposed 
by  heat. 

Pure  nickel-salts  are  conveniently  prepared  on  the  small  scale  from  crude 
speiss  or  kupfernickel  by  the  following  process :  The  mineral  is  broken  into 
small  fragments,  mixed  with  from  one  fourth  to  half  its  weight  of  iron 
filings,  and  the  whole  dissolved  in  nitromuriatic  acid.  The  solution  is 
gently  evaporated  to  dryness,  the  residue  treated  with  boiling  water,  and 
the  insoluble  iron  arsenate  removed  by  a  filter.  The  liquid  is  then  acidu- 
lated with  hydrochloric*  acid,  treated  with  hydrogen  sulphide  in  excess, 
which  precipitates  the  copper,  and,  after  filtration,  boiled  with  a  little  nitric 
acid  to  bring  back  the  iron  to  the  state  of  sesquioxide.  To  the  cold  and 
largely  diluted  liquid  solution,  acid  sodium  carbonate  is  gradually  added, 
by  which  the  ferric  oxide  may  be  completely  separated  without  loss  of 
nickel-salt.  Lastly,  the  filtered  solution,  boiled  with  sodium  carbonate  in 
excess,  yields  an  abundant  pale-green  precipitate  of  nickel  carbonate,  from 
which  all  the  other  compounds  may  be  prepared. 

The  precipitate  thus  obtained  may  still,  however,  contain  cobalt,  the 
separation  of  which  is  not  very  easy.  Several  methods  of  separating  these 
metals  have  been  proposed,  the  best  of  which  is,  perhaps,  that  of  H.  Rose. 
The  mixed  oxides  or  carbonates  being  dissolved  in  excess  of  hydrochloric 
acid,  the  solution,  largely  diluted  with  water,  is  super-saturated  with  chlor- 
ine gas,  whereby  the  cobalt  monoxide  is  converted  into  sesquioxide,  while 
the  nickel  monoxide  remains  unaltered.  The  liquid  is  next  mixed  with 
excess  of  recently  precipitated  barium  carbonate,  left  to  stand  for  twelve 
to  eighteen  hours,  and  shaken  up  from  time  to  time.  The  whole  of  the  cobalt 
is  thereby  thrown  down  as  sesquioxide,  while  the  nickel  remains  in  solu- 
tion, and  may  be  precipitated  as  hydrate  by  potash,  after  the  barium  also 
contained  in  the  solution  has  been  removed  by  precipitation  with  sulphuric 
acid.* 

Nickel-salts  are  well  characterized  by  their  behavior  with  reagents. 
Caustic  alkalies  give  a  pale  apple-green  precipitate  of  hydrate,  insoluble 
in  excess.  Ammonia  affords  a  similar  precipitate,  which  is  soluble  in  excess, 
with  deep  purplish-blue  color.  Potassium  and  sodium  carbonates  give  pale- 
green  precipitates.  Ammonium  carbonate,  a  similar  precipitate,  soluble  in 
excess,  with  blue  color.  Potassium  ferrocyanide  gives  a  greenish-white  pre- 

*  For  other  modes  of  separating  nickel  and  cobalt,  see  Gmelin's  Handbook,  vol.  v.  pp.  355-360; 
and  Watts's  Dictionary  of  Chemistry,  vol.  i.  p.  1046. 


COBALT.  407 

cipitate.  Potassium  cyanide  produces  a  green  precipitate,  which  dissolves  in 
an  excess  of  the  precipitant  to  an  amber-colored  liquid,  and  is  reprecipitated 
by  an  addition  of  hydrochloric  acid.  Hydrogen  sulphide  occasions  no  change, 
if  the  nickel  be  in  combination  with  a  strong  acid.  Ammonium  sulphide  pro- 
duces a  black  precipitate  of  nickel  sulphide,  which  dissolves  slightly  in 
excess  of  the  precipitant  with  dark-brown  color.  Nickel  sulphide  when 
once  precipitated  is  insoluble  in  dilute  hydrochloric  acid ;  it  is  soluble  in 
nitromuriatic  and  in  hot  nitric  acid. 

The  chief  use  of  nickel  in  the  arts  is  in  the  preparation  of  a  white  alloy, 
sometimes  called  German  silver,  made  by  melting  together  100  parts  of  cop- 
per, 60  of  zinc,  and  40  of  nickel.  This  alloy  is  very  malleable,  and  takes  a 
high  polish. 


COBALT. 

Atomic  weight,  58-8.     Symbol,  Co. 

This  substance  bears,  in  many  respects,  a  close  resemblance  to  nickel:  it 
is  often  associated  with  the  latter  in  nature,  and  may  be  obtained  from  its 
compounds  by  similar  means. 

A  cobalt-salt  free  from  nickel  may  be  prepared  by  Rose's  process  just 
described.  The  precipitate,  consisting  of  cobalt  sesquioxide  mixed  with 
barium  carbonate,  is  boiled  with  hydrochloric  acid  to  reduce  the  cobult 
sesquioxide  to  monoxide,  and  dissolve  it  as  a  chloride  together  with  the 
barium.  The  latter  metal  is  then  precipitated  by  sulphuric  acid,  and  from 
the  filtered  liquid  the  cobalt  may  be  precipitated  as  hydrate  by  potash. 
A  solution  of  cobalt  free  from  nickel  may  also  be  obtained  by  precipitating 
the  mixed  solution  with  oxalic  acid  ;  the  whole  of  the  nickel  is  thereby 
precipitated,  together  with  a  small  portion  of  the  cobalt,  leaving  pure 
cobalt  in  solution. 

Cobalt  is  a  white,  brittle,  very  tenacious  metal,  having  a  specific  gravity 
of  8-5,  and  a  very  high  melting-point.  It  is  unchanged  in  the  air,  and  but 
feebly  attacked  by  dilute  hydrochloric  and  sulphuric  acids.  It  is  strongly 
magnetic. 

Cobalt  forms  two  classes  of  salts,  analogous  in  composition  to  the  ferrous 
and  ferric  salts ;  but  the  cobaltic  salts,  in  which  the  metal  is  apparently 
trivalent,  are  very  unstable. 

CHLORIDES. — The  dichloride  or  Cobaltous  chloride,  Co//Cl2,  is  easily  pre- 
pared by  dissolving  the  oxide  in  hydrochloric  acid;  or  it  may  be  prepared 
directly  from  cobalt-glance,  the  native  arsenide,  by  a  process  exactly  similar 
to  that  described  in  the  case  of  nickel.  It  forms  a  deep  rose-red  solution, 
which,  when  sufficiently  strong,  deposits  hydrated  crystals  of  the  same 
color :  when  the  liquid  is  evaporated  by  heat  to  a  very  small  bulk,  it  de- 
posits anhydrous  crystals,  which  are  blue:  these  latter  by  contact  with 
water  again  dissolve  to  a  red  liquid.  A  dilute  solution  of  cobalt  chloride 
constitutes  the  well-known  blue  sympathetic  ink:  characters  written  on  paper 
with  this  liquid  are  invisible,  from  their  paleness  of  color,  until  the  salt 
has  been  rendered  anhydrous  by  exposure  to  heat,  when  the  letters  appear 
blue.  On  laying  it  aside,  moisture  is  absorbed,  and  the  writing  once  more 
disappears.  Green  sympathetic  ink  is  a  mixture  of  the  chlorides  of  cobalt 
and  nickel. 

The  trichloride,  or  Cobaltic  chloride,  Co2Cl6,  is  obtained  in  solution  by  dis- 
solving the  sesquioxide  in  hydrochloric  acid,  and  in  small  quantity  by 
saturating  a  solution  of  the  dichloride  with  chlorine  gas.  The  liquid  has 


408  TETRAD   METALS. 

a  dark -brown  color,  but  easily  decomposes,  giving  off  chlorine  and  leaving 
the  rose-colored  dichloride. 

OXIDES. — Cobalt  forms  two  oxides  analogous  to  those  of  nickel,  also  two 
or  three  of  intermediate  composition  but  not  very  well  denned.  The  mon- 
oxide, or  Cobaltous  oxide,  Cox/0,  is  a  gray  powder,  very  soluble  in  acids,  and 
is  a  strong  base,  isomorphous  with  magnesia,  affording  salts  of  a  fine  red 
tint.  It  is  prepared  by  precipitating  cobaltous  sulphate  or  chloride  with 
sodium  carbonate,  and  washing,  drying,  and  igniting  the  precipitate.  When 
the  cobalt-solution  is  mixed  with  caustic  potash,  a  beautiful  blue  precipitate 
falls,  which,  when  heated,  becomes  violet,  and  at  length  dirty  red,  from  ab- 
sorption of  oxygen  and  a  change  in  the  state  of  hydration. 

The  sesquioxide,  or  Cobaltic  oxide,  Co203,  is  a  black,  insoluble,  neutral 
powder,  obtained  by  mixing  solutions  of  cobalt  and  chloride  of  lime.  It 
dissolves  in  acids,  yielding  the  cobaltic  salts. 

Cobaltoso-cobaltic  oxide,  Co304,  analogous  to  the  magnetic  oxide  of  iron,  is 
formed  when  cobaltous  nitrate  .or  oxalate,  or  hydrated  cobaltic  oxide,  is 
heated  in  contact  with  the  air.  According  to  Fre"my,  it  is  a  salifiable  base. 

Another  oxide,  of  acid  character,  is  said  to  be  obtained  in  the  form  of  a 
potassium  salt  by  fusing  the  monoxide  or  sesquioxide  with  potassium  hy- 
drate. A  crystalline  salt  is  thus  formed  consisting,  according  to  Schwarzen- 
berg,  of  3Co305.K20.  3Aq. 

COBALTOUS  SULPHATE,  S04Co//.70H2. — This  salt  forms  red  crystals,  re- 
quiring for  solution  24  parts  of  cold  water:  they  are  identical  in  form  with 
those  of  magnesium  sulphate.  It  combines  with  the  sulphates  of  potassium 
and  ammonium,  forming  double  salts,  which  contain,  as  usual,  6  molecules 
of  water. 

A  solution  of  oxalic  acid  added  to  cobaltous  sulphate  occasions,  after  some 
time,  the  separation  of  nearly  the  whole  of  the  base  in  the  state  of  oxalate. 

COBALTOUS  CARBONATE. — The  alkaline  carbonates  produce  in  solutions 
of  cobalt  a  pale  peach-blossom-colored  precipitate  of  combined  carbonate 
and  hydrate,  containing  3  CoH302.2C03Co. 

AMMONIACAL  COBALT  COMPOUNDS. — Cobaltous  salts  treated  with  ammonia 
in  a  vessel  protected  from  the  air,  unites  with  the  ammonia,  forming  com- 
pounds which  may  be  called  ammonio-coballous  salts.  Most  of  them  contain 
6  molecules  of  ammonia  to  1  molecule  of  the  cobalt  salt ;  thus  the  chloride 
contains  CoCl2.6NH3.  Aq. ;  the  nitrate,  Co(N03)2.6NH3.  2  Aq.  They  are 
generally  crystallizable  and  of  a  rose-color,  soluble  without  decomposition 
in  ammonia,  but  decomposed  by  water,  with  formation  of  a  basic  salt.  H. 
Rose,  by  treating  dry  cobalt  chloride  with  ammonia-gas,  obtained  the  com- 
pound CoCl2.4NH3;  and  in  like  manner  an  ammonio-sulphate  has  been 
formed  containing  S04Co.6NH?. 

When  an  ammoniacal  solution  of  cobalt  is  exposed  to  the  air,  oxygen  is 
absorbed,  the  liquid  turns  brown,  and  new  salts  are  formed  containing  a 
higher  oxide  of  cobalt  (either  Co203  or  CoOA  and  therefore  designated 
generally  as  peroxidized  ammonio-cobalt  salts.  Several  of  them,  containing 
different  bases,  are  often  formed  at  the  same  time. 

Most  of  the  peroxidized  ammonio-cobalt  salts  are  composed  of  cobaltic 
salts  united  with  two  or  more  molecules  of  ammonia.  The  composition  of 
the  normal  salts  may  be  illustrated  by  the  chlorides,  as  in  the  following 
table :  — 

Tetrammonio-cobaltic  chloride        ,         .     Co2Cl6  .     4NH3 
Hexammouio-cobaltic  chloride    ,        .        Co2Cl6  .     6NH3 


COBALT.  409 

Octammonio-cobaltic  (or  fusco-cobaltic) 

chloride Co2Cl6  .  8NH3 

Decammonio-cobaltic  (roseo-  and  pur- 

pureo-cobaltic)  chloride  .  .  .  Co2Cl6  .  10NH3 

Dodecammonio-cobaltic  (or  luteo-cobal- 

tic)  chloride Co2Cl6  .  12NH3. 

The  formulae  of  the  corresponding  normal  nitrates  are  deduced  from  the 
preceding  by  substituting  N(33  for  Cl ;  those  of  the  sulphates,  oxalates,  and 
other  bibasic  salts,  by  substituting  SO4.  C204,  &c.,  for  C12.  Thus  decammonio- 
cobaltic  sulphate  =  Co2(S04)3.10NH3.  There  are  also  several  acid  and  basic 
sats  of  the  same  ammonia-molecules.  Further,  there  is  a  class  of  salts  con- 
taining the  elements  of  nitrogen  dioxide  or  nitrosyl,  NO,  in  addition  to  nm- 
monia,  e.  g.,  decammonio-nilroso-obaltic  or  xantho- cobaltic  oxy  chloride,  Co2Cl40. 
10NH3.N2O2.  Lastly,  Fre"my  has  obtained  ammoniacal  compounds  (oxy- 
cobaltic  salts)  containing  salts  of  cobalt  corresponding  to  the  dioxide.* 


Cobaltous  salts  have  the  following  characters: 

Solution  of  potash  gives  a  blue  precipitate,  changing  by  heat  to  violet  and 
red.  Ammonia  gives  a  blue  precipitate,  soluble  with  difficulty  in  excess, 
with  brownish-red  color.  Sodium  carbonate  affords  a  pink  precipitate.  Am- 
monium carbonate  a  similar  compound,  soluble  in  excess.  Potassium  ferro- 
cyanide  gives  a  grayish-green  precipitate.  Potassium  cyanide  affords  a  yel- 
lowish-brown precipitate,  which  dissolves  in  an  excess  of  the  precipitant. 
The  clear  solutions,  after  boiling,  may  be  mixed  with  hydrochloric  acid 
without  giving  a  precipitate.  Hydrogen  sulphide  produces  no  change,  if  the 
cobalt  be  in  combination  with  a  strong  acid.  Ammonium  sulphide  throws 
down  black  sulphide  of  cobalt,  insoluble  in  dilute  hydrochloric  acid. 

Cobaltic  salts,  formed  by  dissolving  cobaltic  oxide  in  acids,  give  with 
potash  a  dark-brown  precipitate  of  hydrated  cobaltic  oxide  ;  with  ammonia 
a  brownish-red  solution ;  with  the  fixed  alkaline  carbonates  a  green  solution, 
which  deposits  a  small  quantity  of  cobaltic  oxide;  with  ammonium  sulphide 
(after  saturation  of  the  free  acid  by  ammonia)  a  black  precipitate. 

Oxide  of  cobalt  is  remarkable  for  the  magnificent  blue  color  it  communi- 
cates to  glass :  indeed,  this  is  a  character  by  which  its  presence  may  be  most 
easily  detected,  a  very  small  portion  of  the  substance  to  be  examined  being 
fused  with  borax  on  a  loop  of  platinum  wire  before  the  blowpipe ;  the  pro- 
duction of  this  color  both  in  the  inner  and  in  the  outer  flame  distinguishes 
cobalt  from  all  other  metals. 

The  substance  called  smalt,  used  as  a  pigment,  consists  of  glass  colored 
by  cobalt:  it  is  thus  made:  —  The  cobalt  ore  is  roasted  until  nearly  free 
from  arsenic,  and  then  fused  with  a  mixture  of  potassium  carbonate  and 
quartz-sand,  free  from  oxide  of  iron.  Any  nickel  that  may  happen  to 
be  contained  in  the  ore  then  subsides  to  the  bottom  of  the  crucible  as  arsen- 
ide :  this  is  the  speiss  of  which  mention  has  already  been  made.  The  glass, 
when  complete,  is  removed  and  poured  into  cold  water:  it  is  afterwards 
ground  to  powder  and  elutriated.  Cobalt-ultramarine  is  a  fine  blue  color 
prepared  by  mixing  16  parts  of  freshly-precipitated  alumina  with  2  parts  of 
cobalt  phosphate  or  arsenate  :  this  mixture  is  dried  and  slowly  heated  to  red- 
ness. By  daylight  the  color  is  pure  blue,  but  by  artificial  light  it  is  violet. 
A  similar  compound,  of  a  fine  green  color,  is  formed  by  igniting  zinc  oxide 
with  cobalt-salts.  Za/er  is  the  roasted  cobalt  ore  mixed  with  siliceous  sand, 

*  For  the  preparation  and  properties  of  all  these  salts,  see  Wa^ts's  Dictionary  of  Chemistry, 
vol.  i.  p.  1051.  Their  rational  formula  are  similar  to  those  of  the  ainmoniacal  platiuum  Baits 
(p.  375). 

85 


410  TETRAD    METALS. 

and  reduced  to  fine  powder ;  it  is  used  in  enamel  painting.  A  mixture  in 
due  proportions  of  the  oxides  of  cobalt,  manganese,  and  iron  is  used  for 
giving  a  fine  black  color  to  glass. 


MANGANESE. 

Atomic  weight,  55.     Symbol,  Mn. 

MANGANESE  is  tolerably  abundant  in  nature  in  an  oxidized  state,  forming, 
or  entering  into  the  composition  of,  several  interesting  minerals.  Traces 
of  this  substance  are  very  frequently  found  in  the  ashes  of  plants. 

Metallic  manganese,  or  perhaps,  strictly,  manganese  carbonide,  may  be 
prepared  by  the  following  process:  —  The  carbonate  is  calcined  in  an  open 
vessel,  by  which  it  becomes  converted  into  a  dense  brown  powder :  this  is 
intimately  mixed  with  a  little  charcoal,  and  about  one-tenth  of  its  weight 
of  anhydrous  borax.  A  charcoal  crucible  is  next  prepared  by  filling  a 
Hessian  or  Cornish  crucible  with  moist  charcoal  powder,  introduced  a  little 
at  a  time,  and  rammed  as  hard  as  possible.  A  smooth  cavity  is  then  scooped 
in  the  centre,  into  which  the  above-mentioned  mixture  is  compressed,  and 
covered  with  charcoal  powder.  The  lid  of  the  crucible  is  then  fixed,  and 
the  whole  arranged  in  a  very  powerful  wind-furnace.  The  heat  is  slowly 
raised  until  the  crucible  becomes  red-hot,  after  which  it  is  urged  to  its 
maximum  for  an  hour  or  more.  When  cold,  the  crucible  is  broken  up,  and 
the  metallic  button  of  manganese  extracted. 

Deville  has  lately  prepared  pure  manganese  by  reducing  pure  manganese 
oxide  with  an  insufficient  quantity  of  sugar  charcoal  in  a  crucible  made  of 
caustic  lime.  Thus  prepared,  metallic  manganese  possesses  a  reddish  lustre 
like  bismuth ;  it  is  very  hard  and  brittle,  and,  when  powdered,  decomposes 
water,  even  at  the  lowest  temperature.  Dilute  sulphuric  acid  dissolves  it 
with  great  energy,  evolving  hydrogen.  Brunner  produced  metallic  man- 
ganese from  manganese  and  sodium  fluoride  by  means  of  sodium.  The 
metal  obtained  by  this  process  scratches  glass  and  hardened  steel,  and  has 
a  specific  gravity  of  7-13. 

Manganese,  from  its  general  relations  to  the  metals  of  the  iron  group,  is 
usually  regarded  as  a  tetrad,  forming  a  dichloride  and  trichloride  analogous 
to  the  iron  chlorides,  together  with  oxides  and  other  compounds  of  corre- 
sponding constitution.  It  is  also  said  to  form  a  heptachloride,  Mnadl4,  or 
MnCl7 

|        ,  according  to  which  it  should  be  regarded  as  an  octad ;  but  the  com- 
MnCl7 
position  of  this  compound  is  not  very  well  established. 

MANGANESE  CHLORIDES.  —  The  dichloride  or  Manganous  chloride  maybe 
prepared  in  a  state  of  purity  from  the  dark-brown  liquid  residue  of  the 
preparation  of  chlorine  from  manganese  dioxide  and  hydrochloric  acid, 
which  often  accumulates  in  the  laboratory  to  a  considerable  extent  in  the 
course  of  investigation :  from  the  pure  chloride,  the  carbonate  and  all 
other  salts  can  be  conveniently  obtained.  The  liquid  referred  to  consists 
chiefly  of  the  mixed  chlorides  of  manganese  and  iron  ;  it  is  filtered,  evapo- 
rated to  perfect  dryness,  and  the  residue  is  slowly  heated  to  dull  ignition  in 
an  earthen  vessel,  with  constant  stirring.  The  iron  chloride  is  thus  either 
volatilized,  or  converted  by  the  remaining  water  into  insoluble  sesquioxide, 
while  the  manganese  salt  is  unaffected.  On  treating  the  grayish-looking 
powder  thus  obtained  with  water,  the  manganese  chloride  is  dissolved  out, 
and  may  be  separated  by  filtration  from  the  iron  oxide.  Should  a  trace  of 
the  latter  yet  remain,  it  may  be  got  rid  of  by  boiling  the  liquid  for  a  few 


] 


MANGANESE.  411 

minutes  with  a  little  manganese  carbonate.  The  solution  of  the  chloride 
has  usually  a  delicate  pink  color,  which  becomes  very  manifest  when  the 
salt  is  evaporated  to  dryness.  A  strong  solution  deposits  rose-colored  ta- 
bular crystals,  which  contain  4  molecules  of  water ;  they  are  very  soluble 
and  deliquescent.  The  chloride  is  fusible  at  a  red-heat,  is  decomposed 
slightly  at  that  temperature  by  contact  with  air,  and  is  dissolved  by  alco- 
hol, with  which  it  forms  a  crystallizable  compound. 

The  trichloride,  or  Manganic  chloride,  Mn2Cl6,  is  formed  when  precipitated 
manganese  oxide  is  immersed  in  cold  dilute  hydrochloric  acid,  the  oxide 
then  dissolving  quietly  without  evolution  of  gas.  Heat  decomposes  the 
trichloride  into  the  monochloride  and  free  chlorine. 

Heptachloride,  Mn2Cll4(?). —  When  potassium  permanganate  is  dissolved 
in  strong  sulphuric  acid,  and  fused  sodium  chloride  is  added  by  small 
portions  at  a  time,  a  greenish-yellow  gas  is  given  off,  which  condenses  at  0° 
to  a  greenish-brown  liquid.  This  compound,  when  exposed  to  moist  air, 
gives  off  fumes  colored  purple  by  permanganic  acid,  and  is  instantly  de- 
composed by  water  into  permanganic  and  hydrochloric  acids.  It  is  regarded 
by  Dumas,  who  discovered  it,  as  the  heptachloride  of  manganese ;  but  H. 
Rose  regards  it  as  an  oxychloride,  MnCl202,  analogous  to  chromic  oxy- 
chloride,  a  view  which  is  corroborated  by  its  mode  of  formation. 

Fluorides  of  manganese  have  been  formed  analogous  to  each  of  these  chlor- 
ides. 

MANGANESE  OXIDES. — Manganese  forms  four  well-defined  oxides,  con- 
stituted as  follows :  — 

Monoxide,  or  Manganous  oxide          ....     MnO 
Trimangano-tetroxide,  or  Manganoso-manganic  oxide    Mn304 
Sesquioxide,  or  Manganic  oxide    ....          Mn203 
Dioxide  or  Peroxide  ......     Mn02. 

The  first  is  a  strong  base,  the  third  a  weak  base ;  the  second  and  fourth 
are  neutral ;  the  second  may  be  regarded  as  a  compound  of  the  first  and 
third,  MnO.Mn203.  There  are  also  several  oxides  intermediate  between 
the  monoxide  and  dioxide,  occurring  as  natural  minerals  or  ores  of  manga- 
nese. Manganese  likewise  forms  two  series  of  oxygen  salts,  called  manga- 
nates  and  permanganates,  the  composition  of  which  may  be  illustrated  by 
the  potassium  salts,  viz.  : 

Potassium  manganate          .         .     Mn04K2    =  Mn03,OK2 
Potassium  permanganate         .          Mn208K2  —.  Mn207.OK2. 

The  oxides,  Mn03  and  Mn207,  corresponding  to  these  salts,  are  not  known. 

Monoxide  or  Manganous  oxide,  MnO.  — When  manganese  carbonate  is  heated 
in  a  stream  of  hydrogen  gas,  or  vapor  of  water,  carbon  dioxide  is  disen- 
gaged, and  a  greenish  powder  left  behind,  which  is  the  monoxide.  Pre- 
pared at  a  dull  red  heat  only,  the  monoxide  is  so  prone  to  absorb  oxygen 
from  the  air,  that  it  cannot  be  removed  from  the  tube  without  change;  but 
when  prepared  at  a  higher  temperature,  it  appears  more  stable.  This  oxide 
is  a  very  powerful  base,  being  isomorphous  with  magnesia  and  zinc  oxide ; 
it  dissolves  quietly  in  dilute  acids,  neutralizing  them  completely  and  form- 
ing salts,  which  have  often  a  beautiful  pink  color.  When  alkalies  are  added 
to  solutions  of  these  compounds,  the  white  hydrated  oxide  first  precipitated 
speedily  becomes  brown  by  passing  into  a  higher  state  of  oxidation. 

Sesquioxide  or  Manganic  oxide,  Mn203. — This  compound  occurs  in  nature 
as  braunite,  and  in  the  state  of  hydrate  as  rnanganite :  a  very  beautiful 
crystallized  variety  is  found  at  Refold,  in  the  Hartz.  It  is  produced 
artificially,  by  exposing  the  hydrated  monoxide  to  the  air,  and  forms 
the  principal  part  of  the  residue  left  in  the  iron  retort  when  oxygen  gas  is 
prepared  by  exposing  the  native  dioxide  to  a  moderate  red-heat.  The 


412  TETRAD   METALS. 

color  of  the  sesquioxide  is  brown  or  black,  according  to  its  origin  or  mode 
of  preparation.  It  is  a  feeble  base,  isomorphous  with  alumina  :  for,  when 
gently  heated  with  diluted  sulphuric  acid,  it  dissolves  to  a  red  liquid,  which, 
on  the  addition  of  potassium  or  ammonium  sulphate,  deposits  octohedral 
crystals  having  a  constitution  similar  to  that  of  common  alum :  these  are, 
however,  decomposed  by  water.  Strong  nitric  acid  resolves  this  oxide  into 
a  mixture  of  monoxide  and  dioxide,  the  former  dissolving,  and  the  latter 
remaining  unaltered;  while  hot  oil  of  vitriol  destroys  it  by  forming  man- 
ganous  sulphate  and  liberating  oxygen  gas.  On  heating  it  with  hydro- 
chloric acid,  chlorine  is  evolved,  as  with  the  dioxide,  but  in  smaller  amount. 

Dioxide,  Mn02. — Peroxide  of  manganese.  Pyrolusite. — The  most  common 
ore  of  manganese ;  it  is  found  both  massive  and  crystallized.  It  may  be 
obtained  artificially  in  the  anhydrous  state  by  gently  calcining  the  nitrate, 
or  in  combination  with  water,  by  adding  solution  of  bleaching-powder  to  a 
salt  of  the  monoxide.  Manganese  dioxide  has  a  black  color,  is  insoluble  in 
water,  and  refuses  to  unite  with  acids.  It  is  decomposed  by  hot  hydro- 
chloric acid  and  by  oil  of  vitriol  in  the  same  manner  as  the  sesquioxide. 

As  this  substance  is  an  article  of  commerce  of  considerable  importance, 
being  used  in  very  large  quantity  for  making  chlorine,  and  as  it  is  subject 
to  great  alteration  of  value  from  admixture  of  the  sesquioxide  and  several 
impurities,  it  becomes  desirable  to  possess  means  of  assaying  different  sam- 
ples that  may  be  presented,  with  a  view  of  testing  their  fitness  for  the  pur- 
poses of  the  manufacturer.  One  of  the  best  and  most  convenient  methods 
is  the  following: — 50  grains  of  the  mineral,  reduced  to  very  fine  powder, 
are  put  into  the  little  vessel  employed  in  the  analysis  of  carbonates  (p.  306), 
together  with  about  half  an  ounce  of  cold  water,  and  100  grains  of  strong 
hydrochloric  acid ;  50  grains  of  crystallized  oxalic  acid  are  then  added,  the 
cork  carrying  the  drying  tube  is  fitted,  and  the  whole  quickly  weighed  or 
counterpoised.  The  application  of  a  gentle  heat  suffices  to  determine  the 
action ;  the  oxalic  acid  is  oxidized  into  water  and  carbon  dioxide,  which 
escapes  as  gas  while  the  manganese  remains  in  solution  as  manganous 
chloride : 

Mn02    +     C204H2     -f     2HC1     =     MnCl2     -f     20H2     -f-     2C02 

Manganese  Oxalic  Manganese  Carbon 

dioxide.  acid.  chloride.  dioxide. 

This  equation  shows  that  every  two  molecules  of  carbon  dioxide  evolved 
correspond  to  one  molecule  of  manganese  dioxide  decomposed.  Now  the 
molecular  weight  of  this  oxide,  87,  is  so  nearly  equal  to  twice  that  of  car- 
bon dioxide,  44,  that  the  loss  of  weight  suffered  by  the  apparatus  when  the 
reaction  has  become  complete,  and  the  residual  gas  has  been  driven  off  by 
momentary  ebullition,  may  be  taken  to  represent  the  quantity  of  real 
dioxide  in  the  50  grains  of  the  sample.  It  is  obvious  that  the  apparatus  of 
"Will  and  Fresenius,  described  at  page  307,  may  also  be  used  with  advantage 
in  this  process. 

Trimango-tetr oxide,  or  Red  manganese  oxide,  Mn304,  or  probably  MnO.Mn203. 
This  oxide  is  also  found  native,  as  hausmannite,  and  is  produced  artifi- 
cially by  heating  the  dioxide  or  sesquioxide  to  whiteness,  or  by  exposing 
the  monoxide  or  carbonate  to  a  red  heat  in  an  open  vessel.  It  is  a  reddish- 
brown  substance,  incapable  of  forming  salts,  and  acted  upon  by  acids  in 
the  same  manner  as  the  two  other  oxides  already  described.  Borax  arid 
glass  in  the  fused  state  dissolve  this  substance,  and  acquire  the  color  of  the 
amethyst. 

Varvicite,  Mn407.OH2  or  Mn0.3Mn02.OH2,  is  a  natural  mineral,  discovered 
by  Mr.  Phillips  among  certain  specimens  of  manganese  ore  from  Warwick- 
shire :  it  has  also  been  found  at  Ilefeld.  It  much  resembles  the  dioxide, 
but  is  harder  and 'more  brilliant.  By  a  strong  heat,  varvicite  is  converted 
into  red  oxide,  with  disengagement  of  aqueous  vapor  and  oxygen  gas. 


MANGANESE.  413 

Several  other  oxides,  intermediate  in  composition  between  the  monoxide 
and  dioxide,  also  occur  native;  they  are  probably  mere  mixtures,  and  in 
many  cases  the  monoxide  is  more  or  less  replaced  by  the  corresponding 
oxides  of  iron,  cobalt,  and  copper. 

MANGANOUS  SULPHATE,  S04Mn.70H2=S03.Mn0.70H2. — A  beautiful  rose- 
colored  and  very  soluble  salt,  isomorphous  with  magnesium  sulphate.  It 
is  prepared  on  the  large  scale  for  the  use  of  the  dyer,  by  heating  in  a  close 
vessel  manganese  dioxide  and  coal,  and  dissolving  the  impure  monoxide 
thus  obtained  in  sulphuric  acid,  with  addition  of  a  little  hydrochloric  acid 
towards  the  end  of  the  process.  The  solution  is  evaporated  to  dryness,  and 
again  exposed  to  a  red  heat,  by  which  ferric  sulphate  is  decomposed. 
Water  then  dissolves  out  the  pure  manganese  sulphate,  leaving  ferric  oxide 
behind.  The  salt  is  used  to  produce  a  permanent  brown  dye,  the  cloth 
steeped  in  the  solution  being  afterwards  passed  through  a  solution  of 
bleaching-powder,  by  which  the  monoxide  is  changed  to  insoluble  hydrate 
of  the  dioxide.  Manganese  sulphate  sometimes  crystallizes  with  5  mole- 
cules of  water.  It  forms  a  double  salt  with  potassium  sulphate,  containing 
(S04)2Mn"K2.60H2. 

MANGANESE  CARBONATE,  C03Mnx/  =  C02Mn//0.  — Prepared  by  precipi- 
tating the  dichloride  with  an  alkaline  carbonate.  It  is  an  insoluble  white 
powder,  sometimes  with  a  buff-colored  tint.  Exposed  to  heat,  it  loses  carbon 
dioxide  and  absorbs  oxygen. 

MANGANATES. — When  an  oxide  of  manganese  is  fused  with  potash,  oxygen 
is  taken  up  from  the  air,  and  a  deep  green  saline  mass  results,  which  con- 
tains potassium  manganate,  Mri04K2  or  Mn03.OK2.  The  addition  of  potas- 
sium nitrate,  or  chlorate,  facilitates  the  reaction.  Water  dissolves  this 
compound  very  readily,  and  the  solution,  concentrated  by  evaporation  in  a 
vacuum,  yields  green  crystals.  Barium  manganate,  Mn04Bax/,  is  formed  in 
a  similar  manner. 

PERMANGANATES. — When  potassium  manganate,  free  from  any  great  ex- 
cess of  alkali,  is  put  into  a  large  quantity  of  water,  it  is  resolved  into  hy- 
drated  manganese  dioxide  which  subsides,  and  potassium  permanganate, 
Mn208K2,  or  Mn207.OK2,  which  remains  in  solution,  forming  a  deep-purple 
liquid: 

3Mn04K2  -|--20H2  =  Mn02  +  40KH  -f  Mn208K2. 

This  effect  is  accelerated  by  heat.  The  changes  of  color  accompanying 
this  decomposition  are  very  remarkable,  and  have  procured  for  the  manga- 
nate the  name  mineral  chameleon;  excess  of  alkali  hinders  the  reaction  in 
some  measure,  by  conferring  greater  stability  on  the  manganate.  Potas- 
sium permanganate  is  easily  prepared  on  a  considerable  scale.  Equal 
parts  of  very  finely  powdered  manganese  dioxide  and  potassium  chlorate 
are  mixed  with  rather  more  than  one  part  of  potassium  hydrate  dissolved 
in  a  little  water,  and  the  whole  is  exposed,  after  evaporation  to  dryness,  to 
a  temperature  just  short  of  ignition.  The  mass  is  treated  with  hot  water, 
the  insoluble  oxide  separated  by  decantation,  and  the  deep-purple  liquid 
concentrated  by  heat,  until  crystals  form  upon  its  surface:  it  is  then  left  to 
cool.  The  crystals  have  a  dark-purple  color,  and  are  not  very  soluble  in 
cold  water.  The  manganates  and  permanganates  are  decomposed  by  con- 
tact with  organic  matter:  the  former  are  said  to  be  isomorphous  with  the 
sulphates,  and  the  latter  with  the  perchlorates.  The  green  and  red  disin- 
fecting agents,  known  as  Condy's  fluids,  are  alkaline  manganates  and  per- 
manganates. 

Hydrogen  permanganate,  or  Permanganic  acid,  Mn./)8H2,  is  obtained  by  dis- 

35* 


414  TETRAD    METALS. 

solving  potassium  permanganate  in  hydrogen  sulphate  (S04H2)  diluted  with 
one  molecule  of  water,  and  distilling  the  solution  at  60°-70°.  Permanganic 
acid  then  passes  over  in  violet  vapors,  and  condenses  to  a  greenish-black 
liquid,  which  has  a  metallic  lustre,  absorbs  moisture  greedily  from  the  air, 
and  acts  as  a  most  powerful  oxidizing  agent,  instantly  setting  fire  to  paper 
and  to  alcohol.* 


Manganous  salts  are  very  easily  distinguished  by  reagents.  The  fixed 
caustic  alkalies  and  ammonia  give  white  precipitates,  insoluble  in  excess, 
quickly  becoming  brown.  The  carbonates  of  the  fixed  alkalies,  and  carbonate 
of  ammonia,  give  white  precipitates,  but  little  subject  to  change,  and  insolu- 
ble in  excess  of  carbonate  of  ammonia.  Hydrogen  sulphide  gives  no  preci- 
pitate, but  ammonium  sulphide  throws  down  insoluble  flesh-colored  sulphide 
of  manganese,  which  is  very  characteristic.  Potassium  f err  ocyanide  gives  a 
white  precipitate. 

Manganese  is  also  easily  detected  by  the  blowpipe:  it  gives  with  borax 
an  amethyst-colored  bead  in  the  outer  or  oxidizing  flame,  and  a  colorless 
one  in  the  inner  flame.  Heated  upon  platinum  foil  with  sodium  carbonate, 
it  yields  a  green  mass  of  sodium  manganate. 


URANIUM. 
Atomic  weight,  120.     Symbol,  U. 

This  metal  is  found  in  a  few  minerals,  as  pitchblende,  which  is  an  oxide? 
and  uranite,  which  is  a  phosphate;  the  former  is  its  principal  ore.  The 
metal  itself  is  isolated  by  decomposing  the  chloride  with  potassium  or 
sodium,  and  is  obtained  as  a  black  coherent  powder,  or  in  fused  white 
malleable  globules,  according  to  the  manner  in  which  the  process  is  con- 
ducted. It  is  permanent  in  the  air  at  ordinary  temperatures,  and  dots  not 
decompose  water  ;  but  in  the  pulverulent  state  it  takes  fire  at  207°,  burning 
with  great  splendor  and  forming  a  dark-green  oxide.  It  unites,  also,  very 
violently  with  chlorine  and  with  sulphur. 

Uranium  forms  two  classes  of  compounds:  viz.,  the  uranous  compounds, 
in  which  it  is  bivalent,  e.g.,  U//C12,  U"0,  U"S04I,  &c.,  and  the  uranic  com- 
pounds, in  which  it  is  apparently  trivalent,  like  iron  in  the  ferric  com- 
pounds, e.  g.  : 

U'"aO"8,  TI'"aO"2Cl2f  .U"'aO"2(N08)2,  U'"20"2(S04)". 
There  are  also  two  oxides  intermediate  between  uranous  and  uranic  oxide- 
There  is  no  chloride,  bromide,  iodide,  or  fluoride  corresponding  to  uranic 
oxide,  such  as  U2C16;  neither  are  there  any  normal  uranic  oxysalts  analo- 
gous to  the  normal  ferric  salts,  such  as  U'"2(N03)6,  U'"2(S04)"8,  &c.  ;  but 
all  the  uranic  salts  contain  the  group  U202,  which  may  be  regarded  as  a 
bivalent  radical  (uranyl),  uniting  with  acids  in  the  usual  proportions  and 
forming  normal  salts  ;  thus  : 


Uranic  oxide  or  Uranyl  oxide          .  .         .     (U 
Uranic  oxychloride  or  Uranyl  chloride         .         (U202X/C12 

Uranic  nitrate  or  Uranyl  nitrate      .  .         .     (U2O2)//(N03)2 
Uranic  sulphate  or  Uranyl  sulphate    .         .         (U202)//(S04)^. 

This  view  of  the  composition  of  the  uranic  salts  is  not,  however,  essential, 
*  Terrell,  Bulletin  de  la  Societe  Chimique  de  Paris,  1862,  p.  40. 


URANIUM.  415 

since   they  may  also   be   formulated   as   basic  salts  in  the  manner  above 
illustrated. 

CHLORIDES.  —  Uranous  chloride,  U//C12,  is  formed,  with  vivid  incandescence, 
by  burning  metallic  uranium  in  chlorine  gas,  also  by  igniting  uranous  oxide 
in  hydrochloric  acid  gas.  It  crystallizes  in  dark-green  regular  octohedrons, 
and  dissolves  easily  in  water,  forming  an  emerald-green  solution,  which  is 
decomposed  when  dropped  into  boiling  water,  giving  off  hydrochloric  acid 
and  yielding  brown  precipitate  of  hydrated  uranous  oxide.  It  is  a  power- 
ful deoxidizing  agent,  reducing  gold  and  silver,  converting  ferric  salts  into 
ferrous  salts,  &c. 

Uranic  oxychloride  or  Uranyl  chloride,  U202C12,  is  formed  when  dry  chlorine 
gas  is  passed  over  red-hot  uranous  oxide,  as  an  orange-yellow  vapor,  which 
solidifies  to  a  yellow  crystalline  fusible  mass,  easily  soluble  in  water.  It 
forms  double  salts  with  the  chlorides  of  the  alkali-metals,  the  potassium 
salt,  for  example,  having  the  composition  U202C12.2KC1.20H2. 

OXIDES.  —  Uranous  oxide,  U/X0,  formerly  mistaken  for  metallic  uranium, 
is  obtained  by  heating  the  oxide,  U304,  or  uranic  oxalate,  in  a  current  of 
hydrogen.  It  is  a  brown  powder,  sometimes  highly  crystalline.  In  the 
finely  divided  state  it  is  pyrophoric.  It  dissolves  in  acids,  forming  green 
salts. 

Uranoso-uranic  oxide,  U304  =  UO.U203. — This  oxide,  analogous  to  the 
magnetic  oxide  of  iron,  forms  the  chief  constituent  of  pitchblende.  It  is 
obtained  artificially  by  igniting  the  metal  or  uranous  oxide  in  contact  with 
the  air,  or  by  gentle  ignition  of  uranic  oxide  or  uranic  nitrate.  It  forms  a 
dark-green  velvety  powder,  of  specific  gravity  7-1  to  7-3.  When  ignited  in 
hydrogen,  or  with  sodium,  charcoal,  or  sulphur,  it  is  reduced  to  uranous 
oxide.  When  ignited  alone,  it  yields  a  black  oxide,  U405,  which  is  most 
probably  a  mixture  of  uranoso-uranic  and  uranous  oxide.  Uranoso-uranic 
oxide  dissolves  in  strong  sulphuric  or  hydrochloric  acid,  yielding  a  mixture 
of  uranous  and  uranic  salt;  by  nitric  acid  it  is  oxidized  to  uranic  nitrate. 

Uranic  oxide,  or  Uranyl  oxide,  U203  =  (U202)//0.  —  Uranium  and  its  lower 
oxides  dissolve  in  nitric  acid,  forming  uranic  nitrate ;  and  when  this  salt  is 
heated  in  a  glass  tube  till  it  begins  to  decompose,  at  250°,  pure  uranic 
oxide  remains  in  the  form  of  a  chamois-yellow  powder.  Uranic  hydrate, 
Ua03.20H2,  cannot  be  prepared  by  precipitating  a  uranic  salt  with  alkalies, 
inasmuch  as  the  precipitate  always  carries  down  alkali  with  it;  but  it  may 
be  obtained  by  evaporating  a  solution  of  uranic  nitrate  in  absolute  alcohol 
at  a  moderate  heat,  till,  at  a  certain  degree  of  concentration,  nitrous  ether, 
aldehyde,  and  other  vapors  are  given  off,  and  a  spongy  yellow  mass  remains, 
which  is  the  hydrate.  In  a  vacuum  at  ordinary  temperatures,  or  at  100° 
in  the  air,  it  gives  off  half  its  water,  leaving  the  monohydrate,  U203.OH2. 
This  hydrate  cannot  be  deprived  of  all  its  water  without  exposing  it  to  a 
heat  sufficient  to  drive  off  part  of  the  oxygen,  and  reduce  it  to  uranoso- 
uranic  oxide. 

Uranic  oxide  and  its  hydrates  dissolve  in  acids,  forming  the  uranic  sails. 
Tho  nitrate,  (U202)//(N03)2.GOH2,  may  be  prepared  from  pitchblende  by  dis- 
solving the  pulverized  mineral  in  nitric  acid,  evaporating  to  dryness,  adding 
water,  and  filtering ;  the  liquid  yields,  by  due  evaporation,  crystals  of 
uranic  nitrate,  which  are  purified  by  a  repetition  of  the  process,  and,  lastly, 
dissolved  in  ether.  This  latter  solution  yields  the  pure  nitrate. 

Uranates. — Uranic  oxide  unites  with  the  more  basic  metallic  oxides.  The 
uranates  of  the  alkali-metals  are  obtained  by  precipitating  a  uranir  salt. 
with  a  caustic  alkali;  those  of  the  earth-metals  and  heavy  metals,  by  pre- 
cipitating a  mixture  of  a  uranic  salt  and  a  salt  of  the  other  metal  with  am- 
monia, or  by  igniting  a  double  carbonate  or  acetate  of  uranium  and  the 


416  TETRAD    METALS. 

other  metal  (calcio-uranic  acetate,  for  example)  in  contact  with  the  air. 
The  uranates  have,  for  the  most  part,  the  composition  2U203.M20.  They 
are  yellow,  insoluble  in  water,  soluble  in  acids.  Those  which  contain 
fixed  bases  are  not  decomposed  at  a  red  heat ;  but  at  a  white  heat,  the 
uranic  oxide  is  reduced  to  uranoso-uranic  oxide,  or  by  ignition  in  hydrogen 
to  uranous  oxide;  the  mass  obtained  by  this  last  method  easily  takes  fire 
in  contact  with  the  air.  Sodium  uranate,  2U203.Na20,  is  much  used  for  im- 
parting a  yellowish  or  greenish  color  to  glass,  and  as  a  yellow  pigment  on 
the  glazing  of  porcelain.  The  "uranium-yellow"  for  these  purposes  is 
prepared  on  the  large  scale  by  roasting  pitchblende  with  lime  in  a  rever- 
beratory  furnace;  treating  the  resulting  calcium  uranate  with  dilute  sul- 
phuric acid;  mixing  the  solution  of  uranic  sulphate  thus  obtained  with 
sodium  carbonate,  by  which  the  uranium  is  first  precipitated  together  with 
other  metals,  but  then  redissolved,  tolerably  free  from  impurity,  by  excess 
of  the  alkali;  and  treating  the  liquid  with  dilute  sulphuric  acid  which 
throws  down  hydrated  sodium  uranate,  2U203.Na20  GAq.  Ammonium 
uranate  is  but  slightly  soluble  in  pure  water,  and  quite  insoluble  in  water 
containing  sal-ammoniac;  it  may,  therefore,  be  prepared  by  precipitat- 
ing a  solution  of  sodium-uranate  with  that  salt.  It  occurs  in  commerce 
as  a  fine  deep-yellow  pigment,  also  called  "uranium  yellow."  This  salt 
when  heated  to  redness  leaves  pure  uranoso-uranic  oxide,  and  may,  there- 
fore, serve  as  the  raw  material  for  the  preparation  of  other  uranium  com- 
pounds. 


Uranous  salts  form  green  solutions,  from  which  caustic  alkalies  throw  down 
a  red-brown  gelatinous  precipitate  of  uranous  hydrate  ;  alkaline  carbonates, 
green  precipitates,  which  dissolve  in  excess,  especially  of  ammonium  car- 
bonate, forming  green  solutions.  Ammonium  sulphide  forms  a  black  preci- 
pitate of  uranous  sulphide ;  hydrogen  sulphide,  no  precipitate. 

Uranic  salts  are  yellow,  and  yield  with  caustic  alkalies  a  yellow  precipitate 
of  alkaline  uranate,  insoluble  in  excess  of  the  reagent.  Alkaline  carbonates 
form  a  yellow  precipitate  consisting  of  a  carbonate  of  uranium  and  the 
alkali-metal,  soluble  in  excess,  especially  of  acid  ammonium  or  potassium 
carbonate.  Ammonium  sulphide  forms  a  black  precipitate  of  uranic  sul- 
phide. Hydrogen  sulphide  forms  no  precipitate,  but  reduces  the  uranic  to  a 
green  uranous  salt.  Potassium  fcrrocyanide  forms  a  red-brown  precipitate. 

All  uranium  compounds,  fused  with  phosphorus  salt  or  borax  in  the  outer 
blowpipe  flame,  produce  a  clear  yellow  glass,  which  becomes  greenish  on 
cooling.  In  the  inner  flame  the  glass  assumes  a  green  color,  becoming  still 
greener  on  cooling.  The  oxides  of  uranium  are  not  reduced  to  the  metallic 
state  by  fusion  with  sodium  carbonate  on  charcoal. 

Uranium  compounds  are  used,  as  already  observed,  in  enamel  painting, 
and  for  the  staining  of  glass,  uranous  oxide  giving  a  fine  black  color,  and 
uranic  oxide  a  delicate  greenish-yellow,  highly  fluorescent  glass.  Uranium 
salts  are  also  used  in  photography. 


INDIUM. 
Atomic  weight,  74.     Symbol,  In. 

This  metal  has  been  recently  discovered  by  Reich  and  Richter,*  in  the 
zinc-blende  of  Freiberg.  Its  spectrum  is  characterized  by  two  indigo- 
colored  lines,  one  very  bright  and  more  refrangible  than  the  blue  line  of 
strontium,  the  other  fainter  but  still  more  refrangible,  approaching  the  blue 
line  of  potassium.  It  was  the  production  of  this  peculiar  spectrum  that 

*  Journal  fur  praktische  Chemie,  Ixxxix.  441. 


INDIUM.  417 

led  to  the  discovery  of  the  metal.  The  ore,  consisting  chiefly  of  blende, 
galena,  and  arsenical  pyrites,  was  roasted  to  expel  sulphur  and  arsenic, 
then  treated  with  hydrochloric  acid,  and  the  solution  was  evaporated  to 
dryness.  The  impure  zinc  chloride  thus  obtained  exhibited,  when  ex- 
amined by  the  spectroscope,  the  first  of  the  indigo  lines  above  mentioned. 
The  chloride  was  afterwards  obtained  in  a  state  of  greater  purity,  and 
from  this  the  hydrate  and  the  metal  itself  were  prepared.  The  first  line 
then  came  out  with  much  greater  brilliancy,  and  the  second  was  likewise 
observed 

Indium  has  hitherto  been  obtained  in  very  small  quantity  only,  so  that 
its  properties  have  been  but  imperfectly  studied.  It  appears,  however,  to 
belong  to  the  iron  group.  The  metal  itself  is  of  a  lead-gray  color,  soft, 
very  malleable,  and  marks  paper  like  lead.  It  dissolves  easily  in  hydro- 
chloric acid,  forming  a  deliquescent  chloride.  From  the  solution  of  this  salt, 
it  is  precipitated  by  ammonia  and  potash  as  a  hydrate,  insoluble  in  excess 
of  either  reagent.  Hydrogen  sulphide  does  not  precipitate  it  from  an  acid 
solution.  The  oxide  heated  on  charcoal  with  soda,  yields  a  metallic  globule, 
which  when  reheated  oxidizes  to  a  yellowish  powder.  The  compounds  of 
indium  impart  a  violet  tint  to  the  flame  of  a  Bunsen's  burner. 


CLASS  V.— PENTAD  METALS. 


ANTIMONY. 

Atomic  weight,  122.     Symbol,  Sb  (Stibium). 

rpHIS  important  metal  is  found  chiefly  in  the  state  of  sulphide.  The  ore 
X  is  freed  by  fusion  from  earthy  impurities,  and  is  afterwards  decomposed 
by  heating  with  metallic  iron  or  potassium  carbonate,  which  retains  the  sul- 
phur. Antimony  has  a  bluish-white  color  and  strong  lustre  ;  it  is  extremely 
brittle,  being  reduced  to  powder  with  the  utmost  ease.  Its  specific  gravity 
is  6-8;  it  melts  at  a  temperature  just  short  of  redness,  and  boils  and  vola- 
tilizes at  a  white  heat.  This  metal  has  always  a  distinct  crystalline,  platy 
structure,  but  by  particular  management  it  may  be  obtained  in  crystals, 
which  arc  rhombohedral.*  Antimony  is  not  oxidized  by  the  air  at  common 
temperatures  ;  when  strongly  heated,  it  burns  with  a  white  flame,  producing 
oxide,  which  is  often  deposited  in  beautiful  crystals.  It  is  dissolved  by  hot 
hydrochloric  acid,  with  evolution  of  hydrogen  and  production  of  chloride. 
Nitric  acid  oxidizes  it  to  antimonic  acid,  which  is  insoluble  in  that  liquid. 

Antimony  forms  two  classes  of  compounds,  the  antimonious  compounds 
in  which  it  is  trivalent,  as  Sb'^Clg,  Sb"'^,  Sb///2S3,  &c.,  and  the  antimonic 
compounds  in  which  it  is  quinquivalent,  as  SbvCl5,  SbTg06,  SbT2S6,  &c. 

CHLORIDES.  —  The  trichloride  or  Antimonious  chloride,  SbCl3,  formerly  called 
butter  of  antimony,  is  produced  when  hydrogen  sulphide  is  prepared  by  the 
action  of  strong  hydrochloric  acid  on  antimonious  sulphide.  The  impure 
and  highly  acid  solution  thus  obtained  is  put  into  a  retort,  and  distilled, 
until  each  drop  of  the  condensed  product,  on  falling  into  the  aqueous  liquid 
of  the  receiver,  produces  a  copious  white  precipitate.  The  receiver  is 
then  changed  and  the  distillation  continued.  Pure  antimonious  chloride 
then  passes  over,  and  solidifies  on  cooling  to  a  white,  highly  crystalline 
mass,  from  which  the  air  must  be  carefully  excluded.  The  same  compound 
is  formed  by  distilling  metallic  antimony  in  powder  with  2|  times  its  weight 
of  corrosive  sublimate.  Antimonious  chloride  is  very  deliquescent :  it  dis- 
solves in  strong  hydrochloric  acid  without  decomposition,  and  the  solution 
poured  into  water  gives  rise  to  a  white  bulky  precipitate,  which,  after  a 
short  time,  becomes  highly  crystalline,  and  assumes  a  pale  fawn- color. 
This  is  the  old  powder  of  Algarotli;  it  is  a  compound  of  trichloride  and  tri- 
oxide  of  antimony.  Alkaline  solutions  extract  the  chloride  and  leave  the 
oxide.  Finely  powdered  antimony  thrown  into  chlorine  gas  takes  fire. 

The  pentachloride,  or  Antimonic  chloride,  SbCl5.  is  formed  by  passing  a 
stream  of  chlorine  gas  over  gently  heated  metallic  antimony :  a  mixture  of 
the  two  chlorides  results,  which  may  be  separated  by  distillation.  The 
pentachloride  is  a  colorless  volatile  liquid,  which  forms  a  crystalline  com- 
pound with  a  small  portion  of  water,  but  is  decomposed  by  a  larger  quantity 
into  antimonic  and  hydrochloric  acids. 

*  On  olectrolyzin.e;  a  solution  of  1  part  of  tartar-emetic  in  4  parts  of  antimonions  chlorido  by 
a  small  battery  of  two  elements,  antimony  forming  the  positive,  and  metallic  cupper  tlie  nega- 
tive pole,  crusts  of  antimony  are  obtained  which  possess  the  remarkable  property  of  exploding 
aud  catching  fire  when  cracked  or  broken  (Gore,  Proceedings  of  the  Royal  Society,  ix.  70). 

418 


ANTIMONY.  419 

ANTIMONIOUS  HYDRIDE.  ANTIMOXETTED  HYDROGEN.  STIBINE,  SbH3  — 
A  compound  of  antimony  and  hydrogen  exists,  but  has  not  been  isolated: 
when  zinc  is  put  into  a  solution  of  antimonious  oxide,  and  sulphuric  acid 
added,  part  of  the  hydrogen  combines  with  the  antimony,  and  the  resulting 
gas  burns  with  a  greenish  flame,  giving  rise  to  white  fumes  of  antimonious 
oxide.  When  the  gas  is  conducted  through  a  red-hot  glass  tube  of  narrow 
dimensions,  or  burned  with  a  limited  supply  of  air,  as  when  a  cold  porcelain 
surface  is  pressed  into  the  flame,  metallic  antimony  is  deposited.  On  pass- 
ing a  current  of  antimonetted  hydrogen  through  a  solution  of  silver  nitrate, 
a  black  precipitate  is  obtained,  containing  SbAg3:  from  the  formation  of 
this  compound  it  is  inferred  that  the  gas  has  the  composition  SbII3,  analo- 
gous to  ammonia,  phosphine,  and  arsine.  There  are  also  several  analogous 
compounds  of  antimony  with  alcohol-radicals,  such  as  trimethylstibine, 
Sb(CH3)3,  triethylstibine,  Sb(C2H5)3,  &c. 

OXIDES. — Antimony  forms  two  oxides,  Sb203  and  Sb205,  analogous  to  the 
chlorides,  the  first  being  a  basic  and  the  second  an  acid  oxide,  also  an  inter- 
mediate neutral  oxide,  Sb204. 

The  trioxide,  or  Antimonious  oxide,  Sb208,  occurs  native,  though  rarely,  as 
valentinite  or  white  antimony,  in  shining  white  trimetric  crystals ;  also  as 
scnarmontite  in  regular  octohedrons :  it  is  therefore  dimorphous.  It  may  be 
prepared  by  several  methods :  as  by  burning  metallic  antimony  at  the  bot- 
tom of  a  large  red-hot  crucible,  in  which  case  it  is  obtained  in  brilliant  crys- 
tals; or  by  pouring  solution  of  antimonious  chloride  into  water,  and  digest- 
ing the  resulting  precipitate  with  a  solution  of  sodium  carbonate.  The  oxide 
thus  produced  is  anhydrous ;  it  is  a  pale  buflf-colored  powder,  fusible  at  a 
red  heat,  and  volatile  in  a  closed  vessel,  but  in  contact  with  air  at  a  high 
temperature,  it  absorbs  oxygen  and  becomes  changed  into  the  tetroxide. 
When  boiled  with  cream  of  tartar  (acid  potassium  tartrate),  it  is  dissolved, 
and  the  solution  yields  on  evaporation  crystals  of  tartar-emetic,  which  is 
almost  the  only  antimonious  salt  that  can  bear  admixture  with  water  with- 
out decomposition.  An  impure  oxide  for  this  purpose  is  sometimes  pre- 
pared by  carefully  roasting  the  powdered  sulphide  in  a  reverberatory  furnace, 
nace,  and  raising  the  heat  at  the  end  of  the  process,  so  as  to  fuse  the  product : 
it  has  long  been  known  under  the  name  of  glass  of  antimony,  or  vitrum  anti- 
monii. 

Antimonious  oxide  likewise  acts  as  a  feeble  acid,  forming  salts  called  an- 
timonites,  which  however  are  very  unstable. 

The  tetroxide,  or  Antimonoso-antimonic  oxide,  Sb203.Sb206,  occurs  native 
as  cervanlite  or  antimony  ochre,  in  acicular  crystals,  or  as  a  crust  or 
powder.  It  is  the  ultimate  product  of  the  oxidation  of  the  metal  by 
heat  and  air:  it  is  a  grayish-white  powder,  infusible,  and  non-volatile,  in- 
soluble in  water  and  acids,  except  when  recently  precipitated.  On  treat- 
ing it  with  tartaric  acid  (acid  potassium  tartrate),  antimonious  oxide  is  dis- 
solved, antimonic  acid  remaining  behind;  and  when  a  solution  of  the 
tetroxide  in  hydrochloric  acid  is  gradually  dropped  into  a  large  quantity 
of  water,  antimonious  oxide  is  precipitated,  while  antimonic  acid  remains 
dissolved.  From  these  and  similar  reactions  it  has  been  inferred  that  the 
tetroxide  is  a  compound  of  the  trioxide  and  pentoxide.  On  the  other  hand, 
it  is  sometimes  regarded  as  a  distinct  oxide,  because  it  dissolves  without 
decomposition  in  alkalies,  forming  salts  (often  called  antimonitcs},  which  may 
be  obtained  in  the  solid  state.  Two  potassium  salts,  for  example,  have  been 
formed,  containing  Sb204 .  K20  and  2Sb204  .  K20 ;  and  a  calcium  salt  2Sb./)4. 
3CaO,  occurs  as  a  natural  mineral  called  roiaeine.  These  salts  may,  how- 
ever, be  regarded  as  compounds  of  antimonates  and  antimonites  (contain- 
ing Sb203) :  thus,  2(Sb204.  K20)  =  (Sb205  .  K20)  -f  (Sb203.  K20). 

The  pentoxide,  or  Antimonic  oxide,  Sb206,  is  formed  as  an  insoluble  hydrate 


420  PENTAD  METALS. 

when  strong  nitric  acid  is  made  to  act  upon  metallic  antimony ;  and,  on  ex- 
posing this  hydrate  to  a  heat  short  of  redness,  it  yields  the  anhydrous  pen- 
toxide  as  a  pale  straw-colored  powder,  insoluble  in  water  and  acid.  It  is 
decomposed  by  a  red-heat,  yielding  the  tetroxide. 

Hydrated  antimonic  oxide  is  likewise  obtained  by  decomposing  antimony 
pentachloride  with  an  excess  of  water,  hydrochloric  acid  being  formed  at 
the  same  time.  The  hydrated  oxides,  or  acids,  produced  by  the  two  pro- 
•  cesses  mentioned,  dift'er  in  many  of  their  properties,  and  especially  in  their 
deportment  with  bases.  The  acid  produced  by  nitric  acid,  called  antimonic 
acid,  is  monobasic,  producing  normal  salts  of  the  form  Sb2Os.M20,  or 
Sb03M,  and  acid  salts  containing  2Sb205.M20,  or  Sb20B.2SbOaM.  The  other, 
called  melantimonic  acid,  is  bibasic,  forming  normal  salts  containing  Sb205. 
2M20,  or  Sb207M4,  and  acid  salts,  containing  2Sb205 .  2M20,  or  Sb,0§ .  M20, 
so  that  the  acid  metantimonates  are  isomeric  or  polymeric,  with  the  normal 
antimonates.  Among  the  metantimonates  an  acid  potassium  salt,  Sb206. 
K20 .  70H,  is  to  be  particularly  noticed  as  yielding  a  precipitate  with 
sodium  salts:  it  is,  indeed,  the  only  reagent  which  precipitates  sodium.  It 
is  obtained  by  fusing  antimonic  oxide  with  an  excess  of  potash  in  a  silver 
crucible,  dissolving  the  fused  mass  in  a  small  quantity  of  cold  water,  and 
allowing  it  to  crystallize  in  a  vacuum.  The  crystals  consist  of  normal 
potassium  metantimonate,  Sb205.  2KO,  and,  when  dissolved  in  pure  water, 
are  decomposed  into  free  potash  and  acid  metantimonate. 

SULPHIDES.  The  trisulphide  or  Anlimonious  sulphide,  Sb2S3,  occurs  native 
as  a  lead-gray,  brittle  substance,  having  a  radiated  crystalline  texture,  and 
is  easily  fusible.  It  may  be  prepared  artificially  by  melting  together  anti- 
mony and  sulphur.  When  a  solution  of  tartar-emetic  is  precipitated  by 
hydrogen  sulphide,  a  brick-red  precipitate  falls,  which  is  the  same  sub- 
stance combined  with  a  little  water.  If  the  precipitate  be  dried  and  gently 
heated,  the  water  may  be  expelled  without  other  change  of  color  than  a 
little  darkening,  but  at  a  higher  temperature  it  assumes  the  color  and 
aspect  of  the  native  sulphide.  This  remarkable  change  probably  indicates 
a  passage  from  the  amorphous  to  the  crystalline  condition. 

When  powdered  antimonious  sulphide  is  boiled  in  a  solution  of  caustic 
potash,  it  is  dissolved  antimonious  oxide,  and  potassium  sulphide  being 
produced,  the  latter  unites  with  an  additional  quantity  of  antimonious  sul- 
phide to  form  a  soluble  sulphur-salt,  in  which  the  potassium  sulphide  is  the 
sulphur  base,  and  the  antimonious  sulphide  is  the  sulphur  acid: 

3K20  +  2Sb2S3  =  Sb203  +  Sb2S8 .  3K2S. 

The  antimonious  oxide  separates  in  small  crystals  from  the  boiling  solu- 
tion when  the  latter  is  concentrated,  and  the  sulphur-salt  dissolves  an  extra 
portion  of  antimonious  sulphide,  which  it  again  deposits  on  cooling  as  a 
red  amorphous  powder,  containing  a  small  admixture  of  antimonious  oxide 
and  potassium  sulphide.  This  is  the  kcrmes  mineral  of  the  old  chemists. 
The  filtered  solution  mixed  with  an  acid  gives  a  potassium  salt,  hydrogen 
sulphide,  and  precipitated  antimonious  sulphide.  Kermes  may  also  be 
made  by  fusing  a  mixture  of  5  parts  antimonious  sulphide  and  3  of  dry 
sodium  carbonate,  boiling  the  mass  in  80  parte  of  water,  and  filtering  while 
hot:  the  compound  separates  on  cooling.  The  compounds  of  antimonious 
sulphide  with  basic  sulphides  are  called  sulph-antimonites ;  many  of  them 
occur  as  natural  minerals.  For  example :  zinkenite,  Sb2S3.PbS ;  feather  ore, 
Sb2S8.2PbS ;  boulangerite,  Sb2Ss.3PbS  ;  fahlore,  or  tetrahedrite,  Sb2S3.4Cu2S. 
the  antimony  being  more  or  less  replaced  by  arsenic,  and  the  copper  by 
silver,  iron,  zinc,  and  mercury. 

The  pentasulphide  or  Antimonic  sulphide,  Sb2S3,  formerly  called  sulphur  au- 
ratum,  is  also  a  sulphur  acid,  forming  salts  called  sulphantimonates,  most  of 


ANTIMONY.  421 

which  have  the  composition  Sb2S5.  3M2S,  or  SbS4M3,  analogous  to  the  normal 
orthophosphates  and  arsenates.  When  18  parts  finely  powdered  antimoni- 
ous  sulphide,  17  parts  dry  sodium  carbonate,  13  parts  slaked  lime,  and  3^ 
parts  sulphur,  are  boiled  for  some  hours  in  a  quantity  of  water,  calcium 
carbonate,  sodium  antimonate,  antimony  pentasulphide,  and  sodium  sulphide 
are  produced.  The  first  is  insoluble,  and  the  second  partially  so:  the  two 
last-named  bodies,  on  the  contrary,  unite  to  form  soluble  sodium  sulph- 
antirnonate,  SbS4Na3,  which  may  be  obtained  by  evaporation  in  beautiful 
crystalc.  A  solution  of  this  substance,  mixed  with  dilute  sulphuric  acid, 
furnishes  sodium  sulphate,  hydrogen  sulphide,  and  antimony  pentasulphide, 
which  falls  as  a  golden-yellow  flocculent  precipitate. 

The  sulphantimonates  of  the  alkali-metals  and  alkaline  earth-metals  are 
very  soluble  in  water,  and  crystallize  for  the  most  part  with  several  mole- 
cules of  water.  Those  of  the  heavy  metals  are  insoluble,  and  are  obtained 
by  precipitation. 

The  few  salts  of  antimony  soluble  in  water  are  distinctly  characterized 
by  the  orange  or  brick-red  precipitate  with  hydrogen  sulphide,  which  is  solu- 
ble in  a  solution  of  ammonium  sulphide,  and  again  precipitated  by  an  acid. 

Antimoriious  chloride,  as  already  observed,  is  decomposed  by  water, 
yielding  a  precipitate  of  oxychloride.  The  precipitate  dissolves  in  hy- 
drochloric acid,  and  the  resulting  solution  gives,  with  potash,  a  white  pre- 
cipitate of  trioxide,  soluble  in  a  large  excess  of  the  reagent ;  with  ammonia 
the  same,  insoluble  in  excess ;  with  potassium  or  sodium  carbonate,  also  a  pre- 
cipitate of  trioxide,  which  dissolves  in  excess,  especially  of  the  potassium 
salt,  but  reappears  after  a  while.  If,  however,  the  solution  contains  tartaric 
acid,  the  precipitate  formed  by  potash  dissolves  easily  in  excess  of  the  alkali ; 
ammonia  forms  but  a  slight  precipitate,  and  the  precipitates  formed  by  al- 
kaline carbonates  are  insoluble  in  excess.  The  last-mentioned  characters 
are  likewise  exhibited  by  a  solution  of  tartar-emetic  (potassio-antimonious 
tartrate).  Zinc  and  iron  precipitate  antimony  from  its  solutions  as  a  black 
powder.  Copper  precipitates  it  as  a  shining  metallic  film,  which  may  be 
dissolved  off  by  potassium  permanganate,  yielding  a  solution  which  will 
give  the  characteristic  red  precipitate  with  hydrogen  sulphide. 

Solid  antimony  compounds  fused  upon  charcoal  with  sodium  carbonate  or 
potassium  cyanide,  yield  a  brittle  globule  of  antimony,  a  thick  white  fume 
being  at  the  same  time  given  off,  and  the  charcoal  covered  to  some  distance 
around  with  a  white  deposit  of  oxide. 


Besides  its  application  to  medicine,  antimony  is  of  great  importance  in 
the  arts,  inasmuch  as,  in  combination  with  lead,  it  forms  type-metal.  This 
alloy  expands  at  the  moment  of  solidifying,  and  takes  an  exceedingly  sharp 
impression  of  the  mould.  It  is  remarkable  that  both  its  constituents  shrink 
under  similar  circumstances,  and  make  very  bad  castings. 

Britannia  metal  is  an  alloy  of  9  parts  tin  and  1  part  antimony,  frequently 
also  containing  small  quantities  of  copper,  zinc,  or  bismuth.  An  alloy  of 
2  parts  tin,  1  part  antimony,  and  a  small  quantity  of  copper,  forms  a 
superior  kind  of  pewter.  Alloys  of  antimony  with  tin,  or  tin  and  lead,  are 
now  much  used  for  machinery-bearings  in  place  of  gun-metal.  Alloys  of 
antimony  with  nickel  and  with  silver  occur  as  natural  minerals. 

Antimony  trisulphide  enters  into  the  composition  of  the  blue  signal-lights 
used  at  sea.* 

Blue  or  Bengal  light : 

Dry  potassium  nitrate        ...  6  parts 

Sulphur 2      " 

Antimony  trisulphide 1  part. 

All  in  fine  powder,  and  intimately  mixed. 
36 


422  PENTAD  METALS. 

ARSENIC. 

Atomic  weight,  75.     Symbol,  As. 

ARSENIC  is  sometimes  found  native:  it  occurs  in  considerable  quantity  as 
a  constituent  of  many  minerals,  combined  with  metals,  sulphur  and  oxygen. 
In  the  oxidized  state  it  has  been  found  in  very  minute  quantity  in  a  great 
many  mineral  waters.  The  largest  proportion  is  derived  from  the  roasting 
of  natural  arsenides  of  iron,  nickel,  and  cobalt.  The  operation  is  con- 
ducted in  a  reverberatory  furnace,  and  the  volatile  products  are  condensed 
in  a  long  and  nearly  horizontal  chimney,  or  in  a  kind  of  tower  of  brick- 
work, divided  into  numerous  chambers.  The  crude  arsenious  oxide  thus 
produced  is  purified  by  sublimation,  and  then  heated  with  charcoal  in  a 
retort;  the  metal  is  reduced,  and  readily  sublimes. 

Arsenic  has  a  steel-gray  color,  and  high  metallic  lustre:  it  is  crystalline 
and  very  brittle;  it  tarnishes  in  the  air,  but  may  be  preserved  unchanged 
in  pure  water.  Its  density,  in  the  solid  state,  is  5-7  to  59.  When  heated, 
it  volatilizes  without  fusion,  and  if  air  be  present,  oxidizes  to  arsenious 
oxide.  Its  vapor  density,  compared  with  that  of  hydrogen,  is  150,  which 
is  twice  its  atomic  weight,  so  that  its  molecule  in  the  gaseous  state,  like 
that  of  phosphorus,  occupies  only  half  the  volume  of  a  molecule  of  hy- 
drogen (p.  228).  The  vapor  has  the  odor  of  garlic. 

Arsenic  combines  with  metals  in  the  same  manner  as  sulphur  and  phos- 
phorus, which  it  resembles,  especially  the  latter,  in  many  respects:  indeed, 
it  is  often  regarded  as  a  metalloid. 

Arsenic,  like  nitrogen,  behaves  in  most  respects  as  a  triad  element,  not 
being  capable  of  uniting  with  more  than  three  atoms  of  any  one  monad 
element.  Thus,  it  forms  the  compounds  AsH3,  AsCl3,  AsBr3,  &c.,  but  no 
compound  analogous  to  the  pentachloride  of  phosphorus  or  antimony.  But 
just  as  ammonia,  NHg,  can  take  up  the  elements  of  hydrochloric  acid  to 
form  sal-ammoniac,  NH4C1,  in  which  nitrogen  appears  quinquivalent,  so 
likewise  can  arsenetted  hydrogen  or  arsine,  As//xH3,  unite  with  the  chlorides, 
bromides,  &c.  of  the  radicals,  methyl,  ethyl,  &c.,  to  form  salts  in  which 
the  arsenic  appears  to  be  quinquivalent,  e.  y.  : 

Arsenethylium  bromide    .     .     .     AsvII3(C2H5)Br.,  &c. 
Arsenmethylium  chloride  .     .     .  AsvH3(CH3)Cl. 

In  like  manner,  arsentrim ethyl,  As///(CH3)3,  unites  writh  the  chlorides 
of  methyl  and  ethyl,  forming  the  compounds  Asv(CH3)4Cl  and  AsT(CH3)3 
(C2H6)C1. 

Arsenic  likewise  forms  two  oxides,  viz.,  arsenious  oxide,  Asx//203,  and 
arsenic  oxide,  AsT205,  with  corresponding  acids  and  salts,  analogous  to  phos- 
phorous and  phosphoric  compounds;  the  arsenates,  in  particular,  are  iso- 
morphous  with  the  other  phosphates,  and  resemble  them  closely  in  many 
other  respects. 

ARSENIOUS  CHLORIDE,  AsCl3.  —  This,  the  only  known  chloride  of  arsenic, 
is  produced,  with  emission  of  heat  and  light,  when  powdered  arsenic  is 
thrown  into  chlorine  gas.  It  is  prepared  by  distilling  a  mixture  of  1  part 
of  metallic  arsenic  and  6  parts  of  corrosive  sublimate,  and  by  distil- 
ling arsenious  oxide  with  strong  hydrochloric  acid,  or  with  a  mixture  of 
common  salt  and  sulphuric  acid.  It  is  a  colorless,  volatile,  highly  poisonous 
liquid,  decomposed  by  water  into  arsenious  and  hydrochloric  acids.  Arse- 
nious iodtde,  AsI3,  is  formed  by  heating  metallic  arsenic  with  iodine  :  it  is  a 
•deep-red  crystalline  substance,  capable  of  sublimation.  The  corresponding 
bromide  arid  fluoride  are  both  liquid, 


ARSENIC.  423 

HYDRIDES.  —  Arsenic  forms  two  hydrides,  containing  2  and  3  atoms  of 
hydrogen  combined  with  1  atom  of  arsenic. 

The  trihydride,  Arsenious  hydride,  Arsenetted  hydrogen  or  Arsine,  AsH~, 
analogous  in  composition  to  ammonia,  phosphine,  and  stibine,  is  obtained 
pure  by  the  action  of  strong  hydrochloric  acid  on  an  alloy  of  equal  parts  of 
zinc  and  arsenic,  and  is  produced  in  greater  or  less  proportion  whenever 
hydrogen  is  set  free  in  contact  with  arsenious  acid.  Arsenetted  hydrogen 
is  a  colorless  gas,  of  specific  gravity  2-G95,  slightly  soluble  in  water,  and 
having  the  smell  of  garlic.  It  burns,  when  kindled,  with  a  blue  flame, 
generating  arsenious  .acid.  It  is  also  decomposed  by  transmission  through 
a  red-hot  tube.  Many  metallic  solutions  are  precipitated  by  this  substance. 
When  inhaled,  it  is  exceedingly  poisonous,  even  in  very  minute  quantity. 

AsH2 

The  dihydride,  AsH2,  or  rather  As2H4  —  |         ,  is  produced  by  passing  an 

AsH2 

electric  current  through  water,  the  negative  pole  being  formed  of  metallic 
arsenic :  also  when  potassium  or  sodium  arsenide  is  dissolved  in  water. 
It  is  a  brown  powder,  which  gives  oft'  hydrogen  when  heated  in  a  close 
vessel,  and  burns  when  heated  in  the  air.  It  is  analogous  in  composition 
to  arsendimethyl  or  cacodyl,  As2(CH3)4. 

ARSENIOUS  OXIDE,  ACID,  AND  SALTS.  —  Arsenious  oxide,  As203,  also  called 
white  oxide  of  arsenic,  is  produced  in  the  manner  already  mentioned.  It  is 
commonly  met  with  in  the  form  of  a  heavy,  white,  glassy-looking  substance, 
with  smooth  conchoi'dal  fracture,  which  has  evidently  undergone  fusion. 
When  freshly  prepared  it  is  often  transparent,  but  by  keeping  becomes 
opaque,  at  the  same  time  slightly  diminishing  in  density,  and  acquiring  a 
greater  degree  of  solubility  in  water.  100  parts  of  that  liquid  dissolve  at 
100°  about  11-5  parts  of  the  opaque  variety:  the  largest  portion  separates, 
however,  on  cooling,  leaving  about  3  parts  dissolved:  the  solution,  which 
contains  arsenious  acid,  feebly  reddens  litmus.  Cold  water,  agitated  with 
powdered  arsenious  oxide,  takes  up  a  still  smaller  quantity.  Alkalies  dis- 
solve this  substance  freely,  forming  arsenites;  compounds  with  ammonia, 
baryta,  strontia,  lime,  magnesia,  and  manganous  oxide  also  have  been 
formed:  the  silver  salt  is  a  beautiful  lemon-yellow  precipitate.  The  ar- 
senites are,  however,  very  unstable,  and  have  been  but  little  examined. 
Those  which  have  the  composition  As02M,  or  As203.  M20,  are  generally  re- 
garded as  normal  salts;  there  are  also  arsenites  containing  As205M4.  or 
As203 .  2M20,  and  As03M3,  or  As203  3M20,  besides  acid  salts.  Arsenious 
oxide  is  easily  soluble  in  hot  hydrochloric  acid.  Its  vapor  is  colorless  and 
inodorous,  and  it  crystallizes  on  solidifying  in  brilliant  transparent  octo- 
hedrons.  The  oxide  or  acid  itself  has  a  feeble  sweetish  and  astringent 
taste,  and  is  a  most  fearful  poison. 

ARSENIC  OXIDE,  ACID,  AND  SALTS. — When  powdered  arsenious  oxide  is 
dissolved  in  hot  hydrochloric  acid,  and  oxidized  by  the  addition  of  nitric 
acid,  the  latter  being  added  as  long  as  red  vapors  are  produced,  the  whole 
then  cautiously  evaporated  to  complete  dryncss,  and  the  residue  heated  to 
low  redness,  arsenic  oxide,  As205,  remains  in  the  form  of  a  white  anhydrous 
mass  which  has  no  action  upon  litmus.  When  strongly  heated,  it  is  resolved 
into  arsenious  oxide  and  free  oxygen.  In  water  it  dissolves  slowly  but  com- 
pletely, giving  a  highly  acid  solution,  which,  on  being  evaporated  to  a 
syrupy  consistence,  deposits,  after  a  time,  hydrated  crystals  of  arsenic  acid, 
containing  2AsO4IT3 .  6lI2,  or  As206.30H2  -f  Aq.  These  crystals,  wlu-n 
heated  to  100°,  give  off  their  water  of  crystallization  and  leave  trikydrated 
arsenic  acid,  As04H3,  or  As20g.  3OII2;  at  140°— 100°  the  dihydrale,  As,(>7II4, 
or  As206.  20H2,  is  left ;  and  at  260°  the  monohydrate,  AsOsII,  or  As206.  OIIa. 


424  PENTAD    METALS. 

The  aqueous  solutions  of  the  three  hydrates  and  of  the  anhydrous  oxide 
exhibit  exactly  the  same  characters,  and  all  contain  the  trihydrate,  the 
other  hydrates  being  immediately  converted  into  that  compound  when  dis- 
solved in  water ;  in  this  respect  the  hydrates  of  arsenic  acid  differ  essen- 
tially from  those  of -phosphoric  acid  (p.  285). 

Arsenic  acid  is  a  very  powerful  acid,  forming  salts  isomorphous  with  the 
corresponding  phosphates  :  it  is  also  tribasic.  A  sodium  arsenate,  As04HNa,2. 
120H2,  undistinguishable  in  appearance  from  common  sodium  phosphate, 
may  be  prepared  by  adding  the  carbonate  to  a  solution  of  arsenic  acid,  until 
an  alkaline  reaction  is  apparent,  and  then  evaporating.  This  salt  also 
crystallizes  with  7  molecules  of  water.  Another  arsenate,  As04Na3. 120H2, 
is  produced  when  sodium  carbonate  in  excess  is  fused  with  arsenic  acid,  or 
when  the  preceding  salt  is  mixed  with  caustic  soda.  A  third,  As04H2Na. 
OH2,  is  made  by  substituting  an  excess  of  arsenic  acid  for  the  solution  of 
alkali.  The  alkaline  arsenates  which  contain  basic  water  lose  the  latter  at 
a  red  heat,  but,  unlike  the  phosphates,  recover  it  when  again  dissolved. 
The  arsenates  of  the  alkalies  are  soluble  in  water:  those  of  the  earths  and 
other  metallic  oxides  are  insoluble,  but  are  dissolved  by  acid.  The  precip- 
itate with  silver  nitrate  is  highly  characteristic  of  arsenic  acid:  it  is  red- 
dish-brown. 

SULPHIDES.  —  Two  sulphides  of  arsenic  are  known.  The  disulphide,  As2S2, 
occurs  native  as  Realgar.  It  is  formed  artificially  by  heating  arsenic  acid 
with  the  proper  proportion  of  sulphur.  It  is  an  orange-red,  fusible,  and 
volatile  substance,  employed  in  painting,  and  by  the  pyrotechnist  in  making 
white  fire.  The  trisulphide  or  arsenious  sulphide,  AsS3,  also  occurs  native  as 
Orpiment,  and  is  prepared  artificially  by  fusing  arsenic  with  the  appropriate 
quantity  of  sulphur,  or  by  precipitating  a  solution  of  arsenious  acid  with 
hydrogen  sulphide.  It  is  a  golden-yellow,  crystalline  substance,  fusible, 
and  volatile  by  heat.  A  cold  solution  of  arsenic  acid  is  not  immediately 
precipitated  by  hydrogen  sulphide,  but  after  some  hours  the  solution,  satu- 
rated with  hydrogen  sulphide,  yields  a  light-yellow  deposit  of  sulphur,  the 
arsenic  acid  being  reduced  to  arsenious  acid,  which  is  then  gradually  con- 
verted into  lemon-yellow  arsenious  sulphide.  In  boiling  solutions  the  pre- 
cipitation takes  place  immediately.  The  mixture  of  sulphur  and  trisulphide, 
thus  produced,  was  formerly  regarded  as  a  pentasulphide,  corresponding 
to  arsenic  acid. 

The  disulphide  and  trisulphide  of  arsenic  are  sulphur-acids,  uniting  with 
other  metallic  sulphides  to  form  sulphur-salts.  Those  of  the  disulphide  are 
called  hyposulpharsemtes ;  they  are  but  little  known.  The  salts  of  arsenious 
sulphide  are  called  sulpharsenites.  Their  composition  may  be  represented 
by  that  of  the  potassium  salts,  viz.,  As2S2K,  or  AsS3.K2S;  As2S5K4,  or 
As2S3.  2K2S,  and  AsS3K3,  or  As2S3.  3K2S.  Of  these  the  bibasic  salts  are  the 
most  common.  The  sulpharsenites  of  the  alkali-metals  and  alkaline  earth- 
metals  are  soluble  in  water,  and  may  be  prepared  by  digesting  arsenious 
sulphide  in  the  solutions  of  the  corresponding  hydrates  or  sulph-hydrates ; 
the  rest  are  insoluble  and  are  obtained  by  precipitation.  Sulphur-salts, 
called  sulpharsenates,  corresponding  in  composition  to  the  arsenates,  are  pro- 
duced, in  like  manner,  by  digesting  the  mixture  of  sulphur  and  arsenious 
sulphide,  precipitated,  as  above  mentioned,  from  arsenic  acid,  in  solutions 
of  alkaline  hydrates  or  sulph-hydrates ;  also  by  passing  gaseous  hydrogen 
sulphide  through  solutions  of  arsenates.  There  are  three  sulph-arsenates 
of  potassium,  containing  AsS3K,  or  As2S5.K2S;  As2S7K4,  or  As2S5.2K2S; 
and  AsS4K?,  or  As2S5.  3K2S.  The  sulph-arsenates  of  the  alkali-metals  and 
alkaline  earth-metals  are  soluble  in  water ;  the  rest  are  insoluble  and  are 
obtained  by  precipitation. 


ARSENIC. 


425 


Fig.  174. 


Arsenious  acid  is  distinguished  by  characters  which  cannot  be  misun- 
derstood. 

Silver  nitrate,  mixed  with  a  solution  of  arsenious  acid  in  water,  occasions 
no  precipitate,  or  merely  a  faint  cloud :  but  if  a  little  alkali,  or  a  drop  of 
ammonia,  be  added,  a  yellow  precipitate  of  silver  arscnite  immediately  falls. 
The  precipitate  is  exceedingly  soluble  in  excess  of  ammonia ;  that  sub- 
stance must,  therefore,  be  added  with  great  caution ;  it  is  likewise  very 
soluble  in  nitric  acid. 

Cupric  sulphate  gives  no  precipitate  with  solution  of  arsenious  acid,  until 
the  addition  has  been  made  of  a  little  alkali,  when  a  brilliant  yellow-green 
precipitate  (Scheele's  green)  falls,  which  also  is  very  soluble  in  excess  of 
ammonia. 

llijdrogcn  sulphide  passed  into  a  solution  of  arsenious  acid,  to  which  a  few 
drops  of  hydrochloric  or  sulphuric  acid  have  been  added,  occasions  the  pro- 
duction of  a  copious  bright-yellow  precipitate  of  orpimcnt,  which  is  dis- 
solved with  facility  by  ammonia,  and  reprecipitated  by  acids. 

Solid  arsenious  oxide,  heated  by  the  blowpipe  in  a  narrow  glass  tube  with 
small  fragments  of  dry  charcoal,  affords  a  sublimate  of  metallic  arsenic  in 
the  shape  of  a  brilliant  steel-gray  metallic  ring.  A  portion  of  this,  detached 
by  the  point  of  a  knife,  and  heated  in  a  second  glass  tube,  with  access  of 
air,  yields,  in  its  turn,  a  sublimate  of  colorless,  transparent,  octohedral 
crystals  of  arsenious  oxide. 

All  these  experiments,  which  jointly  give  demonstrative  proof  of  the 
presence  of  the  substance  in  question,  may  be  performed  with  perfect  pre- 
cision and  certainty  upon  exceedingly  small  quantities  of  material. 

The  detection  of  arsenious  acid  in  complex  mixtures,  con- 
taining organic  matter  and  common  salt,  as  beer,  gruel,  soup, 
&c.,  or  the  fluid  contents  of  the  stomach  in  cases  of  poison 
ing,  is  a  very  far  more  difficult  problem,  but  one  which  is, 
unfortunately,  often  required  to  be  solved.  These  organic 
matters  interfere  completely  with  the  liquid  tests,  and  render 
their  indications  worthless.  Sometimes  the  difficulty  may  be 
eluded  by  a  diligent  search  in  the  suspected  liquid,  and  in  the 
vessel  containing  it,  for  fragments  or  powder  of  solid  arseni- 
ous oxide,  which,  from  its  small  degree  of  solubility,  often 
escape  solution,  and  from  the  high  density  of  the  substance, 
may  be  found  at  the  bottom  of  the  vessels  in  which  the  fluids 
are  contained.  If  anything  of  the  kind  be  found,  it  may  be 
washed  by  decantation  with  a  little  cold  water,  dried,  and  then 
reduced  with  charcoal.  For  the  latter  purpose,  a  small  glass 
tube  is  taken,  having  the  figure  represented  in  the  margin ; 
white  German  glass,  free  from  lead,  is  to  be  preferred.  The 
arsenious  oxide,  or  what  is  suspected  to  be  such,  is  dropped 
to  the  bottom,  and  covered  with  splinters  or  little  fragments  of 
charcoal,  the  tube  being  filled  to  the  shoulder.  The  whole  is 
gently  heated,  to  expel  any  moisture  that  may  be  present  in  the  charcoal, 
and  the  deposited  water  wiped  from  the  interior  of  the  tube  with  bibulous 
paper.  The  narrow  part  of  the  tube  containing  the  charcoal,  from  a  to  b, 
is  now  heated  by  the  blowpipe  flame  ;  when  red-hot,  the  tube  is  inclined,  so 
that  the  bottom  also  may  become  heated.  The  arsenious  oxide,  if  present, 
is  vaporized,  and  reduced  by  the  charcoal,  and  a  ring  of  metallic  arsenic 
deposited  on  the  cool  part  of  the  tube.  To  complete  the  experiment, 
the  tube  may  be  melted  at  a  by  the  point  of  the  flame,  drawn  off,  and 
closed,  and  the  arsenic  oxidized  to  arsenious  oxide,  by  chasing  it  up 
and  down  by  the  boat  of  a  small  spirit-lamp.  A  little  water  may  after- 
wards be  introduced,  and  boiled  in  the  tube,  by  which  the  arsenious 
oxide  will  be  dissolved,  and  to  this  solution  the  tests  of  silver  nitrate 
30* 


426  PENTAD    METALS. 

and  ammonia,  copper  sulphate  and  ammonia,  and  hydrogen  sulphide,  may 
be  applied. 

When  the  search  for  solid  arsenious  oxide  fails,  the  liquid  itself  must  be 
examined;  a  tolerably  limpid  solution  must  be  obtained,  from  which  the 
arsenic  may  be  precipitated  by  hydrogen  sulphide,  and  the  orpiment  col- 
lected, and  reduced  to  the  metallic  state.  It  is  in  the  first  part  of  this 
operation  that  the  chief  difficulty  is  found:  such  organic  mixtures  refuse  to 
filter,  or  filter  so  slowly  as  to  render  some  method  of  acceleration  indispen- 
sable.* Boiling  with  a  little  caustic  potash  or  acetic  acid  will  sometimes 
effect  this  object.  The  following  is  an  outline  of  a  plan  which  has  been 
found  successful  in  a  variety  of  cases  in  which  a  very  small  quantity  of 
arsenious  acid  had  been  purposely  added  to  an  organic  mixture:  —  Oil  of 
vitriol,  itself  perfectly  free  from  arsenic,  is  mixed  with  the  suspected 
liquid,  in  the  proportion  of  about  a  measured  ounce  to  a  pint,  having  been 
previously  diluted  with  a.  little  water,  and  the  whole  is  boiled  in  a  flask  for 
half  an  hour,  or  until  a  complete  separation  of  solid  and  liquid  matter 
becomes  manifest.  The  acid  converts  any  starch  that  may  be  present  into 
dextrin  and  sugar:  it  completely  coagulates  albuminous  substances,  and 
casein,  in  the  case  of  milk,  and  brings  the  whole  in  a  very  short  time  into 
a  state  in  which  filtration  is  both  easy  and  rapid.  Through  the  filtered 
solution,  when  cold,  a  current  of  hydrogen  sulphide  is  transmitted,  and  the 
liquid  is  warmed,  to  facilitate  the  deposition  of  the  arsenious  sulphide, 
which  falls  in  combination  with  a  large  quantity  of  organic  matter,  which 
often  communicates  to  it  a  dirty  color.  This  is  collected  upon  a  small  filter, 
and  washed.  It  is  next  transferred  to  a  capsule,  and  heated  with  a  mix- 
ture of  nitric  and  hydrochloric  acids,  by  which  the  organic  impurities  are 
in  great  measure  destroyed,  and  the  arsenic  oxidized  to  arsenic  acid.  The 
solution  is  evaporated  to  dryness,  the  soluble  part  taken  up  by  dilute  hy- 
drochloric acid,  and  then  the  solution  saturated  with  sulphurous  acid, 
whereby  the  arsenic  acid  is  reduced  to  the  state  of  arsenious  acid,  the  sul- 
phurous being  oxidized  to  sulphuric  acid.  The  solution  of  arsenious  acid 
may  now  be  precipitated  by  hydrogen  sulphide  without  any  difficulty.  The 
liquid  is  warmed,  and  the  precipitate  washed  by  decantation,  and  dried. 
It  is  then  mixed  with  black  flux,  and  heated  in  a  small  glass  tube,  similar  to 
that  already  described,  with  similar  precautions;  a  ring  of  reduced  arsenic 
is  obtained,  which  may  be  oxidized  to  arsenious  oxide,  and  further  ex- 
amined. The  black  flux  is  a  mixture  of  potassium  carbonate  and  charcoal, 
obtained  by  calcining  cream  of  tartar  in  a  close  crucible ;  the  alkali  trans- 
forms the  sulphide  into  arsenious  acid,  the  charcoal  subsequently  effecting 
the  deoxidation.  A  mixture  of  anhydrous  sodium  carbonate  and  charcoal 
may  be  substituted  with  advantage  for  the  common  black  flux,  as  it  is  less 
hygroscopic. 

Other  methods  of  proceeding,  different  in  principle  from  the  foregoing, 
have  been  proposed,  as  that  of  the  late  Mr.  Marsh,  which  is  exceedingly 
delicate.  The  suspected  liquid  is  acidulated  with  sulphuric  acid,  and 
placed  in  contact  with  metallic  zinc;  the  hydrogen  reduces  the  arsenious 
acid  and  combines  with  the  arsenic,  if  any  be  present.  The  gas  is  burned 
at  a  jet,  and  a  piece  of  glass  or  porcelain  held  in  the  flame,  when  any  ad- 
mixture of  arsenetted  hydrogen  is  at  once  known  by  the  production  of  a 
brilliant  black  metallic  spot  of  reduced  arsenic  on  the  porcelain;  or  the 
gas  is  passed  through  a  glass  tube  heated  at  one  or  two  places  to  redness, 
whereby  the  arsenetted  hydrogen  is  decomposed,  a  ring  of  metallic  arsenic 
appearing  behind  the  heated  portion  of  the  tube. 

It  has  been  observed  (page  419)  that  antimonetted  hydrogen  gives  a 
similar  result.  In  order  to  distinguish  the  two  substances,  the  gas  may  be 
passed  into  a  solution  of  silver  nitrate.  Both  gases  give  rise  to  a  black 

*  Respecting  the  separation  of  the  arsenious  acid  by  dialysis,  see  pago  149. 


BISMUTH. 


427 


precipitate,  which,  in  the  case  of  antimonetted  hydrogen,  consists  of  silver 
antimonide,  Ag3Sb,  whilst  in  the  case  of  arsenettcd  hydrogen,  it  is  pure 
silver,  the  arsenic  being  then  converted  into  arsenious  acid,  which  com- 
bines with  a  portion  of  silver  oxide.  The  silver  arsenite  remains  dissolved 
in  the  nitric  acid  which  is  liberated  by  the  precipitation  of  the  silver,  and 


Fig.  175. 


may  be  thrown  down  with  its  characteristic  yellow 
color  by  adding  ammonia  to  the  liquid  filtered  off  from 
the  black  precipitate.  The  black  silver  antimonide, 
when  carefully  washed,  and  subsequently  boiled  with 
a  solution  of  tartaric  acid,  yields  a  solution  containing 
antimony  only,  from  which  hydrogen  sulphide  sepa- 
rates the  characteristic  orange-yellow  precipitate  of  an- 
timonious  sulphide. 

A  convenient  form  of  Marsh's  instrument  is  that 
shown  in  fig.  175:  it  consists  of  a  bent  tube,  having  two 
bulbs  blown  upon  it,  fitted  with  a  stop-cock  and  nar- 
row jet.  Slips  of  zinc  are  put  into  the  lower  bulb, 
which  is  afterwards  filled  with  the  liquid  to  be  ex- 
amined. On  replacing  the  stop-cock,  closed,  the  gas 
collects  and  forces  tfre  liquid  into  the  upper  bulb, 
which  then  acts  by  its  hydrostatic  pressure,  and  ex- 
pels the  gas  through  the  jet  so  soon  as  the  stop-cock  is 
opened.  It  must  be  borne  in  mind  that  both  common 
zinc  and  sulphuric  acid  often  contain  traces  of  arsenic. 
Mr.  Bloxam*  has  proposed  an  important  modification 
of  Marsh's  process  for  the  detection  of  arsenic  and  antimony  in  organic 
substances,  which  is  based  on  the  behavior  of  solutions  of  these  metals 
under  the  influence  of  the  electric  current.  Antimony  is  deposited  in  the 
metallic  state,  without  any  disengagement  of  antimonetted  hydrogen,  while 
arsenic  is  evolved  as  arsenetted  hydrogen,  which  may  be  recognized  by  the 
characters  already  indicated. 

A  slip  of  copper-foil  boiled  in  the  poisoned  liquid,  previously  acidulated 
with  hydrochloric  acid,  withdraws  the  arsenic,  and  becomes  covered  with 
a  white  alloy.  By  heating  the  metal  in  a  glass  tube,  the  arsenic  is  expelled, 
and  oxidized  to  arsenious  acid.  This  is  called  Reinsch's  test. 


BISMUTH. 

Atomic  weight,  210.     Symbol,  Bi. 

BISMUTH  is  found  chiefly  in  the  metallic  state,  disseminated  through 
various  rocks,  from  which  it  is  separated  by  simple  exposure  to  heat.  The 
metal  is  highly  crystalline  and  very  brittle :  it  has  a  reddish-white  color, 
and  a  density  of  9-9.  Crystals  of  great  beauty  may  be  obtained  by  slowly 
cooling  a  considerable  mass  of  this  substance  until  solidification  has  com- 
menced, then  piercing  the  crust,  and  pouring  out  the  fluid  resi ''.'.::•.  J>i.s- 
muth  melts  at  about  2t)0°  C.  (500°  F.),  and  volatilizes  at  a  high  temperature. 
It  is  remarkable  as  being  the  most  diamagnetic  of  all  known  bodies.  It  is 
little  oxidized  by  the  air,  but  burns  when  strongly  heated  with  a  bluish 
flame.  Nitric  acid,  somewhat  diluted,  dissolves  it  freely. 

Bismuth  forms  three  classes  of  compounds,  in  which  it  is  bi-,  tri-,  and 
quinquivalent  respectively.  The  tri-compounds  are  the  most  stable  and 
the  most  numerous.  The  only  known  compounds  in  which  bismuth  is  quin- 
quivalent are  indeed  the  pentoxide,  l>i.,(),,  together  with  the  corresponding 
acid  and  metallic  salts.  Nevertheless,  bismuth  is  regarded  as  a  pentad,  ou 

*  Journal  Cbcin.  Soc.,  xiii.  338. 


428  PENTAD    METALS. 

account  of  the  analogy  of  its  compound  with  those  of  antimony.  Several 
bismuth  compounds  are  known  in  which  the  metal  is  apparently  bivalent, 
but  really  trivalent,  as  : 

Bi"Cla  Bi"0 

Bi2Cl4,  or    I          ;     Bi202,  or     I        ,  &c. 

Bi"Cl2  Bi"0 

CHLORIDES.  —  The  trichloride  or  Bismuthous  chloride  is  formed  when  bis- 
muth is  heated  in  a  current  of  chlorine  gas,  and  passes  over  as  a  white, 
easily  fusible  substance,  which  readily  attracts  moisture  from  the  air,  and 
is  converted  into  a  crystallized  hydrate.  The  same  substance  is  produced 
when  bismuth  is  dissolved  in  nitromuriatic  acid,  and  the  solution  evapo- 
rated. Bismuthous  chloride  dissolves  in  water  containing  hydrochloric 
acid,  but  is  decomposed  by  pure  water,  yielding  a  white  precipitate  of  oxy- 
chloride : 

BiCl3  +  OH2  =  BiCIO  +  2HC1. 

The  dichloride,  Bi2Cl4,  produced  by  heating  the  trichloride  with  metallic 
bismuth,  is  a  brown,  crystalline,  easily  fusible  mass,  readily  decomposed 
by  water.  At  a  high  temperature  it  is  resolved  into  the  trichloride  and 
metallic  bismuth. 

OXIDES.  —  The  trioxide,  or  Bismuthous  oxide,  is  a  straw-yellow  powder,  ob- 
tained by  gently  igniting  the  neutral  or  basic  nitrate.  It  is  fusible  at  a 
high  temperature,  and  in  that  state  acts  towards  siliceous  matter  as  a 
powerful  flux. 

The  hydrate,  Bi///H02,  or  Bi203 .  OH2,  is  obtained  as  a  white  precipitate 
when  a  solution  of  the  nitrate  is  decomposed  by  an  alkali.  Both  the  hy- 
drate and  the  anhydrous  oxide  dissolve  in  the  stronger  acids,  forming  the 
bismuthous  salts,  which  have  the  composition  Bix//R3,  where  R  denotes  an 
acid  radical,  e.  .9.,  Bi"'Cl8,  Bi///(N03)3,  Bi'"2(S04)8.  Many  of  these  salts 
crystallize  well,  but  cannot  exist  in  solution  unless  an  excess  of  acid  is 
present.  On  diluting  the  solutions  with  water,  a  basic  salt  is  precipitated, 
and  an  acid  salt  remains  in  solution. 

The  normal  nitrate,  Bi'"(N03)3 .  50H2,  or  Bi203 .  3N205 . 100H2,  forme  large 
transparent  colorless  crystals,  which  are  decomposed  by  water  in  the  man- 
ner just  mentioned,  yielding  an  acid  solution  containing  a  little  bismuth, 
and  a  brilliant  white  crystalline  powder,  which  varies  to  a  certain  extent 
in  composition  according  to  the  temperature  and  the  quantity  of  water  em- 
ployed, but  frequently  consists  of  a  basic  nitrate,  Bi203.  N205.  20H2,  or 
Bi///(N03)3 .  Bi./)3 .  30H2.  A  solution  of  bismuth  nitrate,  free  from  any 
great  excess  of  acid,  poured  into  a  large  quantity  of  cold  water,  yields  an 
insoluble  basic  nitrate,  very  similar  in  appearance  to  the  above,  but  con- 
taining rather  a  large  proportion  of  bismuth  oxide.  This  basic  nitrate  was 
once  extensively  employed  as  a  cosmetic,  but  it  is  said  to  injure  the  skin, 
rendering  it  yellow  and  leather-like.  It  is  used  in  medicine. 

Bismuth  pentoxide,  or  Bismuthic  oxide. — When  bismuth  trioxide  is  sus- 
pended in  a  strong  solution  of  potash,  and  chlorine  passed  through 
the  liquid,  decomposition  of  water  ensues,  hydrochloric  acid  being  formed, 
and  the  trioxide  being  converted  into  the  pentoxide.  To  separate  any 
trioxide  that  may  have  escaped  oxidation,  the  powder  is  treated  with 
dilute  nitric  acid,  when  the  bismuthic  oxide  is  left  as  a  reddish  powder, 
which  is  insoluble  in  water.  This  substance  combines  with  bases,  but  the 
compounds  are  not  very  well  known.  According  to  Arppe,  there  is  an  acid 

potassium  bismuthate  containing  Bi2KH06,  or  2Bi205.  j  ^2Q.    The  pentoxide 

when  heated  loses   oxygen,   an   intermediate  oxide,   Bi204,  being  formed, 
which  may  be  considered  as  bismuthous  bismuthate,  2Bi204  =  Bi203 .  Bi205. 


VANADIUM.  429 

Bismuth  is  sufficiently  characterized  by  the  decomposition  of  the  nitrate 
and  chloride  and  by  water,  and  by  the  black  precipitate  of  bismuth  sulphide, 
insoluble  in  ammonium-sulphide,  which  its  solutions  yield  when  exposed  to 
the  action  of  hydrogen  sulphide. 

A  mixture  of  8  parts  of  bismuth,  5  parts  of  lead,  and  3  of  tin,  is  known 
under  the  name  of  fusible  metal,  and  is  employed  in  taking  impressions  from 
dies  and  for  other  purposes  :  it  melts  below  100°C. 

Bismuth  is  used,  in  conjunction  with  antimony,  in  the  construction  of 
thermo-electric  piles,  these  two  metals  forming  the  opposite  extremes  of  the 
thermo-electric  series. 


VANADIUM. 
Atomic  weight,  51-2.     Symbol,  V. 

VANADIUM  is  found,  in  small  quantity,  in  some  iron  ores,  and  also  as  vana- 
date  of  lead.  It  has  also  been  discovered  in  the  iron  slag  of  Statfordshire, 
{tnd  recently,  by  Roscoe,*  in  larger  quantity  in  the  copper-bearing  beds  at 
Alderley  Edge  and  Mottram  St.  Andrews,  in  Cheshire.  Metallic  vanadium 
remains  when  vanadium  nitride  is  heated  to  whiteness  in  ammonia  gas,  but 
it  does  not  appear  to  have  been  obtained  pure.  It  is  described  as  a  white, 
brittle  substance,  having  a  strong  lustre,  and  very  refractory  in  the  fire. 

Vanadium  was,  till  lately,  regarded  as  a  hexad  metal,  analogous  to  tang- 
sten  and  molybdenum;  but  Roscoe  has  shown  that  it  is  a  pentad,  belonging 
to  the  phosphorus  and  arsenic  group.  This  conclusion  is  based  upon  the 
composition  of  the  oxides  and  oxychlorides;  and  on  the  isomorphism  of  the 
vanadates  with  the  phosphates.  The  chlorides,  and  other  compounds  of 
vanadium  with  monad  chlorous  elements,  have  not  yet  been  obtained. 

VANADIUM  OXIDES. — Vanadium  forms  four  oxides,  represented  by  the 
formulae,  V202,  V203,  V204,  V205,  analogous  therefore  to  the  oxides  of  nitro- 
gen, excepting  that  the  vanadium  oxide  analogous  to  nitrogen  monoxide  is 
not  yet  known. 

The  dioxide,  V202,  which  was  regarded  by  Berzelius  as  metallic  vanadium, 
is  obtained  by  reducing  either  of  the  higher  oxides  with  potassium,  or  by 
passing  the  vapor  of  vanadium-oxytrichloride,  (VOC13),  mixed  with  excess 
6f  hydrogen,  through  a  combustion-tube  containing  red-hot  charcoal.  As 
obtained  by  the  second  process,  it  forms  a  light-gray  glittering  powder,  or 
a  metallically  lustrous  crystalline  crust,  having  a  specific  gravity  of  3-64, 
brittle,  very  difficult  to  fuse,  and  a  conductor  of  electricity.  When  heated 
to  redness  in  the  air,  it  takes  fire  and  burns  to  black  oxide..  It  is  insoluble 
in  sulphuric,  hydrochloric,  and  hydrofluoric  acid,  but  dissolves  easily  in 
nitromuriatic  acid,  forming  a  dark-blue  liquid. 

The  dioxide  may  be  prepared  in  solution  by  the  action  of  nascent  hydro- 
gen (evolved  by  metallic  zinc,  cadmium,  or  sodium-amalgam),  on  a  solution 
of  vanadic  acid  in  sulphuric  acid.  After  passing  through  all  shades  of  blue 
and  green,  the  liquid  acquires  a  permanent  lavender  tint,  and  then  contains 
the  vanadium  in  solution  as  dioxide,  or  as  hi/po-vanadious  salt.  This  com- 
pound absorbs  oxygen  more  rapidly  than  any  other  known  agent,  and 
bleaches  indigo  and  other  vegetable  colors  as  quickly  as  chlorine. 

Vanadium  dioxide  may  be  regarded  as  entering  into  many  vanadium 
compounds,  as  a  bivalent  radical  (just  like  uranyl  in  the  uranic  compounds), 
and  may  therefore  be  called  nimnl/il. 

Vanadium  trioxide,  V203,  or  Vanadyl  monoxide,   (V202)//0,  is  obtained  by 

*  Proceedings  of  the  Royal  Society,  xvi.  223. 


430  PENTAD    METALS. 

igniting  the  pentoxide  in  hydrogen  gas,  or  in  a  crucible  lined  with  char- 
coal. It  is  a  black  powder,  with  an  almost  metallic  lustre,  and  infusible; 
by  pressure  it  may  be  united  into  a  coherent  mass  which  conducts  elec- 
tricity. When  exposed  warm  to  the  air,  it  glows,  absorbs  oxygen,  and  is 
converted  into  pentoxide.  At  ordinary  temperatures,  it  slowly  absorbs 
oxygen,  and  is  converted  into  tetroxide.  By  ignition  in  chlorine  gas  it  is 
converted  into  vanadyl-trichloride  and  vanadium-pentoxide.  It  is  insoluble 
in  acids,  but  may  be  obtained  in  solution  by  the  reducing  action  of  nascent 
hydrogen  (evolved  from  metallic  magnesium)  on  a  solution  of  vanadic  acid 
in  sulphuric  acid. 

Vanadious  oxide,  Vanadium  tetroxide,  or  Vanadyl  dioxide,  ~V204=  (V20?)0?. — 
This  oxide  is  produced,  either  by  the  oxidation  of  the  dioxide  or  trioxide, 
or  by  the  partial  reduction  of  the  pentoxide.  By  allowing  the  trioxide  to 
absorb  oxygen  at  ordinary  temperatures,  the  tetroxide  is  obtained  in  blue 
shining  crystals.  It  dissolves  in  acids,  the  more  easily  in  proportion  as  it 
has  been  less  strongly  ignited,  forming  solutions  of  vanadious  salts,  which 
have  a  bright  blue  color.  The  same  solutions  are  produced  by  the  action 
of  moderate  reducing  agents,  such  as  sulphurous,  sulph-hydric,  or  oxalic 
acid,  upon  vanadic  acid  in  solution  ;  also  by  passing  air  through  acid  solu- 
tions of  the  dioxide  till  a  permanent  blue  color  is  attained.  With  the  hydrates 
and  normal  carbonates  of  the  fixed  alkalies,  they  form  a  grayish-white  precipi- 
tate of  hydrated  vanadious  oxide,  which  dissolves  in  a  moderate  excess  of 
the  reagent,  but  is  reprecipitated  by  a  large  excess  in  the  form  of  a  vanadite 
of  the  alkali-metal. 

Ammonia  in  excess  produces  a  brown  precipitate,  soluble  in  pure  water, 
but  insoluble  in  water  containing  ammonia. — Ammonium  sulphide  forms  & 
black-brown  precipitate,  soluble  in  excess.  —  Tincture  of  galls  forms  a  finely 
divided  black  precipitate,  which  gives  to  the  liquid  the  appearance  of  ink. 

Vanadium-tetroxide  also  unites  with  the  more  basic  metallic  oxides,  form- 
ing salts  called  vanadites,  all  of  which  are  insoluble,  except  those  of  the 
alkali-metals.  The  solutions  of  the  alkaline  vanadites  are  brown,  but  when 
treated  with  hydrogen  sulphide,  they  acquire  a  splendid  red-purple  color, 
arising  from  the  formation  of  a  sulphur-salt. — Acids  color  them  blue,  by 
forming  a  double  vanadious  salt ;  tincture  of  galls  colors  them  blackish-blue. 
The  insoluble  vanadites,  when  moistened  or  covered  with  water,  become 
green,  and  are  converted  into  vanadates. 

Vanadium  pentoxide,  Vanadic  oxide,  or  Vanadyl  trioxide,  V2^5  —  (^2^2)^3- 
This  is  the  highest  oxide  of  vanadium.  It  may  be  prepared  from  native 
lead  vanadate.  This  mineral  is  dissolved  in  nitric  acid,  and  the  lead  and 
arsenic  are  precipitated  by  hydrogen  sulphide,  which  at  the  same  time  re- 
duces the  vanadium  pentoxide  to  tetroxide.  The  blue  filtered  solution  is 
then  evaporated  to  dryness,  and  the  residue  digested  in  ammonia,  which 
dissolves  out  the  vanadic  oxide  reproduced  during  evaporation.  In  this 
solution  a  lump  of  sal-ammoniac  is  put;  as  that  salt  dissolves,  ammonium 
vanadate  subsides  as  a  white  powder,  being  scarcely  soluble  in  a  saturated 
solution  of  ammonium  chloride.  By  exposure  to  a  temperature  below  red- 
ness in  an  open  crucible,  the  ammonia  is  expelled,  and  vanadic  oxide  left. 
By  a  similar  process,  Rosco  has  prepared  vanadic  oxide  from  a  lime  precip- 
itate containing  2  per  cent,  of  vanadium,  obtained  in  working  up  a  poor 
cobalt  ore  from  Mottram  in  Cheshire. 

Vanadium  pentoxide  has  a  reddish-yellow  color,  and  dissolves  in  1000 
parts  of  water,  forming  a  light  yellow  solution.  It  dissolves  also  in  the 
stronger  acids,  forming  red  or  yellow  solutions,  some  of  which  yield  crys- 
talline compounds  (vanadic  salts)  by  spontaneous  evaporation.  It  unites, 
however,  with  bases  more  readily  than  with  acids,  forming  salts  called  vana- 
dates. When  fused  with  alkaline  carbonates,  it  eliminates  3  molecules  of  car- 
bon dioxide,  forming  orthovanadates  analogous  to  the  orthop'tosphates ;  thus : 


VANADIUM.  431 

3(C02  .  Na20)       -f       V205       =      V205  .  3Na20      -f      3C02. 
Sodium  car-  Vanadic  Sodium  ortho-  Carbon 

bonate.  oxide.  vanadate.  dioxide. 

It  also  forms  mefavanadates  analogous  to  the  metaphosphates,  and  two 
series  of  acid  vanadates  or  anhydrovanadates,  viz. : 

Lead  orthovanadate     .     (V04)2Pbx/3  or    V205 .  3Pb/xO 

Strontium  metavanadate  (V03)2Sr//  or    V205  .    Sr//0 

Strontium  divanadate        (V03)2Sr//  .    V205  or  2V205  .     Sr7/0 
Strontium  trivanadate       (V08)aSrV,.  2V206  or  3V205  .    Sr"0. 

Lead  metavanadate  occurs  native  as  dechcnite;  the  orthovanadate  also, 
combined  with  lead  chloride,  as  vanadinite  or  vanadite,  PbCl2.  3(V04)2Pb3, 
the  mineral  in  which  vanadium  was  first  discovered.  Descloizite  is  a  di- 
plumbic  vanadate,  V207Pbx/2  or  V205 .  2PbO,  analogous  in  composition  to  a 
pyrophosphate. 

The  metavanadates  are  mostly  yellow  ;  some  of  them,  however,  especially 
those  of  the  alkaline  earth-metals,  and  of  zinc,  cadmium,  and  lead,  are  con- 
verted by  warming  —  either  in  the  solid  state,  or  under  water,  or  in  aque- 
ous solution,  especially  in  presence  of  a  free  alkali  or  alkaline  carbonate  — 
into  isomeric  colorless  salts.  The  same  transformation  takes  place  also, 
though  more  slowly,  at  ordinary  temperatures.  The  metavanadates  of  al- 
kali-metal are  colorless.  The  acid  vanadates  are  yellow,  or  yellowish-red, 
both  in  the  solid  state  and  in  solution:  hence  the  solution  of  a  neutral  vana- 
date becomes  yellowish-red  on  addition  of  an  acid.  The  metavanadates  of 
ammonium,  the  alkali-metals,  barium,  and  lead,  are  but  sparingly  soluble 
in  water;  the  other  metavanadates  are  more  soluble.  The  alkaline  vana- 
dates are  more  soluble  in  pure  water  than  in  water  containing  free  alkali 
or  salt:  hence  they  are  precipitated  from  their  solutions  by  addition  of 
alkali  in  excess,  or  of  salts.  The  vanadates  are  insoluble  in  alcohol.  The 
aqueous  solutions  of  vanadates  form  yellow  precipitates  with  antimony,  cop- 
per, lead,  and  mercury  salts:  with  tincture  of  galls,  they  form  a  deep  black 
liquid,  which  has  been  proposed  for  use  as  vanadium  ink. 

Hydrogen  sulphide  reduces  them  to  vanadites,  changing  the  color  from  red 
or  yellow  to  blue,  and  forming  a  precipitate  of  sulphur.  Ammonium  sulphide 
colors  the  solutions  brown-red,  and,  on  adding  an  acid,  a  light-brown  pre- 
cipitate is  formed  consisting  of  vanadic  sulphide  mixed  with  sulphur,  the 
.  liquid  at  the  same  time  turning  blue.  Hydrochloric  acid  decomposes  the 
vanadates,  with  evolution  of  chlorine  and  formation  of  vanadium  tetroxide. 

VANADIUM  OXYCHLORIDES,  or  VANADYL  CHLORIDES. — Four  of  these  com- 
pounds are  known,  viz.,  VOC18,  VOC12,  VOC1,  and  V202C1. 

The  oxy trichloride,  VO//C13  (formerly  regarded  as  vanadium  trichloride), 
is  prepared : 

(1)  By  the  action  of  chlorine  on  the  trioxide: 

3V203         +         C112        =         V206        -f         4VOC13. 

(2)  By  burning  the  dioxide  in  chlorine  gas,  or  by  passing  that  gas  over  an 
ignited  mixture  of  the  trioxide,  tetroxide,  or  pentoxide,  and  condensing  the 
vapors  in  a  cooled  U-tube. 

Vanadium  oxy  trichloride,  or  vanadyl  trichloride,  is  a  golden-yellow  liquid, 
of  specific  gravity  1-841  at,  14-5°  C.  (58°  F.).  Boiling  point,  127°  C.  (260° 
F.).  Vapor-density,  by  experiment,  G-108;  by  calculation,  6-1 10.  AVhen 
exposed  to  the  air,  it  emits  cinnabar-colored  vapors,  being  resolved  by  the 
moisture  of  the  air  into  hydrochloric  and  vanadic  acids.  It  oxidizes  mag- 
nesium and  sodium.  Its  vapor,  passed  over  perfectly  pure  carbon  at  a  red 
heat,  yields  carbon  dioxide;  and  when  passed,  together  with  hydrogen, 


432  PENTAD  METALS. 

through  a  red-hot  tube,  yields  vanadium  trioxide.     These  reactions  show 
that  the  compound  contains  oxygen. 

The  other  oxychlorides  of  vanadium  are  solid  bodies  obtained  by  partial 
reduction  of  the  oxytrichloride  with  zinc  or  hydrogen. 

VANADIUM  SULPHIDES.  —  Two  of  these  compounds  are  known,  analogous 
to  the  tetroxide  and  pentoxide  ;  both  are  sulphur  acids.  The  telrasulphide, 
or  Vanadious  sulphide,  V2S4,  is  a  black  substance  formed  by  heating  the 
tetroxide  to  redness  in  a  stream  of  hydrogen  sulphide ;  also  as  a  hydrate 
by  dissolving  a  vanadious  salt  in  excess  of  an  alkaline  monosulphide,  and 
precipitating  with  hydrochloric  acid.  The  penta sulphide,  or  Vanadic  sul- 
phide, V2S5,  is  formed  in  like  manner  by  precipitation  from  an  alkaline 
vanadate. 

VANADIUM  NITRIDES. — The  mononitride,  VN,  is  formed  by  heating  the 
compound  of  vanadium  oxytrichloride  with  ammonium  chloride  to  white- 
ness in  a  current  of  ammonia  gas.  It  is  a  greenish-white  powder  unalter- 
able in  the  air.  The  dinitride,  VN2,  or  V2N4,  is  obtained  by  exposing  the 
same  double  salt  in  ammonia  gas  to  a  moderate  heat.  It  is  a  black  powder 
strongly  acted  upon  by  nitric  acid.  These  compounds  are  of  importance, 
as  they  promise  to  yield  metallic  vanadium,  and  thence  also  the  chlorides, 
bromides,  &c.,  of  that  metal. 

All  vanadium  compounds  heated  with  borax  or  phosphorus-salt  in  the 
outer  blow-pipe  flame  produce  a  clear  bead,  which  is  colorless  if  the 
quantity  of  vanadium  is  small,  yellow  when  it  is  large ;  in  the  inner  flame 
the  bead  acquires  a  beautiful  green  color. 

Vanadic  and  chromic  acids  are  the  only  acids  whose  solutions  are  red: 
they  are  distinguished  from  one  another  by  the  vanadic  acid  becoming  blue, 
and  the  chromic  acid  green,  by  deoxidation. 

When  a  solution  of  vanadic  acid,  or  an  acidulated  solution  of  an  alkaline 
vanadate,  is  shaken  up  with  ether  containing  hydrogen  dioxide,  the  aqueous 
solution  acquires  a  red  color,  like  that  of  ferric  acetate,  while  the  ether 
remains  colorless.  This  reaction  will  serve  to  detect  the  presence  of  1  part 
of  vanadic  acid  in  40,000  parts  of  liquid.  The  other  reactions  of  vanadium 
in  solution  have  already  been  described. 


TANTALUM. 

Atomic  weight.  182.     Symbol,  Ta. 

THIS  metal  was  discovered,  in  1803,  by  Ekeberg,  in  two  Swedish  minerals, 
tantalite  and  yttrotantalite.  A  very  similar  metal,  columbium,  had  been 
discovered  in  the  preceding  year  by  Hatchett,  in  columbite  from  Massachu- 
setts; and  Wollaston,  in  1807,  on  comparing  the  compounds  of  these  metals, 
concluded  that  they  were  identical,  an  opinion  which  was  for  many  years 
received  as  correct;  but  their  separate  identity  has  been  completely  estab- 
lished by  the  researches  of  H.  Rose  (commenced  in  1846),  who  gave  to  the 
metal  from  the  American  and  Bavarian  columbites,  the  name  Niobium,  by 
which  it  is  now  universally  known.  More  recently,  Marignac  has  shown 
that  nearly  all  tantalites  and  columbites  contain  both  tantalum  and  niobium 
(or  columbium),  some  tantalates,  from  Kimito,  in  Finland,  being,  how- 
ever, free  from  niobium,  and  some  of  the  Greenland  columbites  containing 
only  the  latter  metal  unmixed  with  tantalum.  In  all  these  minerals  tan- 
talum exists  as  a  tantalate  of  iron  and  manganese ;  yttrotantalite  is  essen- 


TANTALUM.  433 

tially  a  tantalate  of  yttrium,  containing  also  uranium,  calcium,  iron,  and 
other  metals.  Tantalum  is  also  contained  in  some  varieties  of  wolfram. 

Metallic  tantalum  is  obtained  by  heating  the  fluotantalate  of  potassium 
or  sodium  with  metallic  sodium  in  a  well-covered  iron  crucible,  and 
washing  out  the  soluble  salts  with  water.  It  is  a  black  powder,  which, 
when  heated  in  the  air,  burns  with  a  bright  light,  and  is  converted,  though 
with  difficulty,  into  tantalic  oxide.  It  is  not  attacked  by  sulphuric,  hydro- 
chloric, nitric,  or  even  nitromuriatic  acid.  It  dissolves  slowly  in  warm 
aqueous  hydrofluoric  acid,  with  evolution  of  hydrogen,  and  very  rapidly 
iu  a  mixture  of  hydrofluoric  and  nitric  acids. 

Tantalum,  in  its  principal  compounds,  is  quinquivalent,  the  formula  of 
tantalic  chloride  being  TaCl5,  that  of  tantalic  fluoride,  TaF5,  and  that  of 
tantalic  oxide  (which,  in  combination  with  bases,  forms  the  tantalates), 
Ta./)5.  There  is  also  a  tantalous  oxide,  said  to  have  the  composition  Ta02' 
and  a  corresponding  sulphide,  TaS2. 

TANTALIC  CHLORIDE. — TaCI5  is  obtained,  as  a  yellow  sublimate,  by  ignit- 
ing an  intimate  mixture  of  tantalic  oxide  and  charcoal  in  a  stream  of 
chlorine  gas.  It  begins  to  volatilize  at  144°  C.  (291°  F.)  and  melts  to  a 
yellow  liquid  at  221°  C.  (430°  F.)  The  vapor-density  between  350°  and 
440°  (662°  and  824°  F.)  has  been  found  by  Deville  and  Troost  to  be  12-42 
referred  to  air,  or  178-9  referred  to  hydrogen:  by  calculation,  for  the 
normal  condensation  to  two  volumes,  it  is  179-75.  Tantalic  chloride  is  de- 
composed by  water,  yielding  hydrochloric  and  tantalic  acids;  but  the  de- 
composition is  not  complete  even  at  the  boiling-heat. 

TANTALIC  FLUORIDE,  TaF5,  is  obtained  in  solution  by  treating  tantalic  hy- 
drate with  aqueous  hydrofluoric  acid.  The  solution,  mixed  with  alkaline 
fluorides,  forms  soluble  crystallizable  salts,  called  tantalofluorides  or  fluotan- 
talates.  The  potassium  salt,  TaK2F7  or  TaF5.2KF,  crystallizes  in  monoclinic 
prisms,  isomorphous  with  the  corresponding  fluoniobate. 

TANTALIC  OXIDE,  Ta205,  is  produced  when  tantalum  burns  in  the  air,  also  by 
the  action  of  water  on  tantalic  chloride,  and  may  be  separated  as  a  hydrate 
from  the  tantalates  by  the  action  of  acids.  It  may  be  prepared  from  tan- 
talite,  which  is  a  tantalate  of  iron  and  manganese,  by  fusing  the  finely  pul- 
verized mineral  with  twice  its  weight  of  potassium  hydrate,  digesting  the 
fused  mass  in  hot  water,  and  supersaturating  the  filtered  solution  with  hy- 
drochloric or  nitric  acid :  hydrated  tantalic  oxide  is  then  precipitated  in 
white  flocks,  which  may  be  purified  by  washing  with  water.* 

Anhydrous  tantalic  oxide,  obtained  by  igniting  the  hydrate  or  sulphate, 
is  a  white  powder,  varying  in  density  from  7-022  to  8-264,  according  to  the 
temperature  to  which  it  has  been  exposed.  Heated  in  ammonia  gas  it 
yields  tantalum  nitride:  heated  with  carbon  bisulphide,  it  is  converted  into 
tantalum  bisulphide.  It  is  insoluble  in  all  acids,  and  can  be  rendered  solu- 
ble only  by  fusion  with  potassium  hydrate  or  carbonate. 

Hydrated  Tantalic  Oxide,  or  Tantalic  acid,  obtained  by  precipitating  an 
aqueous  solution  of  potassium  tantalate  with  hydrochloric  acid,  is  a  snow- 
white  bulky  powder,  which  dissolves  in  hydrochloric  and  hydrofluoric  acids; 
when  strongly  heated,  it  glows  and  gives  off  water. 

Tantalic  oxide  unites  with  basic  metallic  oxides,  forming  the  tantalates, 
which  are  represented  by  the  formulae,  Ta2O6  .  M20  and  3Ta,05 .  4M20,  the 
first  including  the  native  tantalates,  such  as  ferrous  tantalate,  and  the 
second  certain  easily  crystallizable  tantalates  of  the  alkali-metals.  The 
tantalates  of  the  alkali-metals  are  soluble  in  water,  and  are  formed  by 
fusing  tantalic  oxide  with  caustic  alkalies:  those  of  the  earth-metals  and 
heavy  metals  are  insoluble,  and  are  formed  by  precipitation. 

*  For  more  complete  methods  of  preparation,  see  Wntts's  Dictionary  of  Chemistry,  v<  1.  v.  p.  C68. 

37 


434  PENTAD  METALS. 

Tantalum  dioxide,  or   Tantalous  oxide,  Ta02,  may  be  represented  by  the 

TaivQ2 
formula  |          ,  in  which  the  metal  is  still  quinquivalent.     It  is  produced 

Ta"02 

by  exposing  tantalic  oxide  to  an  intense  heat  in  a  crucible  lined  with  char- 
coal. It  is  a  hard  dark-gray  substance,  which,  when  heated  in  the  air,  is 
converted  into  tantalic  oxide. 


Hydrochloric,  or  sulphuric  add,  added  in  excess  to  a  solution  of  alkaline 
tantalate,  forms  a  precipitate  of  tantalic  acid,  which  redissolves  in  excess  of 
the  hydrochloric,  but  not  of  the  sulphuric  acid.  Potassium  ferrocyanide, 
added  to  a  very  slightly  acidulated  solution  of  an  alkaline  tantalate,  forms 
a  yellow  precipitate;  the  ferricyanide,  a  white  precipitate.  Infusion  of  galls 
forms  a  light-yellow  precipitate,  soluble  in  alkalies.  When  tantalic  chloride 
is  dissolved  in  strong  sulphuric  acid,  and  then  water  and  metallic  zinc  are 
added,  a  fine  blue  color  is  produced,  which  does  not  turn  brown,  but  soon 
disappears. 

Tantalic  oxide  fused  with  microcosmic  salt  in  either  blowpipe  flame  forms 
a  clear,  colorless  glass,  which  does  not  turn  red  on  addition  of  a  ferrous 
salt.  With  borax  it  also  forms  a  transparent  glass,  which  may  be  rendered 
opaque  by  interrupted  blowing,  or  flaming. 


NIOBIUM,  or  COLUMBIUM. 

Atomic  weight,  94.     Symbol,  Nb. 

This  metal,  discovered  in  1801  by  Hatchett,  in  American  columbite,  exists 
likewise,  associated  with  tantalum,  in  columbites  from  other  sources,  and 
in  most  tantalites ;  also,  associated  with  yttrium,  uranium,  iron,  and  small 
quantities  of  other  metals,  in  Siberian  Samarskite,  urano-tantalite,  or 
yttroilmenite ;  also  in  pyrochlore,  euxenite,  and  a  variety  of  pitchblende 
from  Satersdalen  in  Norway. 

The  metal,  obtained  in  the  same  manner  as  tantalum,  is  a  black  powder, 
which  oxidizes  with  incandescence  when  heated  in  the  air.  It  dissolves  in 
hot  hydrofluoric  acid,  with  evolution  of  hydrogen,  and,  at  ordinary  tem- 
peratures, in  a  mixture  of  hydrofluoric  and  nitric  acid ;  slowly,  also,  when 
heated  with  strong  sulphuric  acid.  It  is  oxidized  by  fusion  with  acid  potas- 
sium sulphate,  and  gradually  converted  into  potassium  niobate  by  fusion 
with  potassium  hydrate  or  carbonate. 

Niobium  is  quinquivalent,  and  forms  only  one  class  of  compounds,  namely, 
a  chloride,  NbCl6;  oxide,  Nb206;  oxychloride,  NbOCl3,  &c. 

NIOBIC  OXIDE,  Nb206,  is  formed  when  the  metal  burns  in  the  air.  It  is 
prepared  from  columbite,  &c.,  by  fusing  the  levigated  mineral  in  a  platinum 
crucible  with  6  or  8  parts  of  acid  potassium  sulphate,  removing  soluble  salts 
by  boiling  the  fused  mass  with  water,  digesting  the  residue  with  ammonium 
sulphide  to  dissolve  tin  and  tungsten,  boiling  with  strong  hydrochloric  acid 
to  remove  iron,  uranium,  and  other  metals,  and  finally  washing  with  water. 
Niobic  oxide  is  thus  obtained  generally  mixed  with  tantalic  oxide,  from 
which  it  is  separated  by  means  of  hydrogen  and  potassium  fluoride,  HF .  KF, 
which  converts  the  tantalum  into  sparingly  soluble  potassium  tantofluoride, 
2KF .  TaF2,  and  the  niobium  into  easily  soluble  potassium  nioboxyfluoride, 
2KF.  NbOF3.  Aq. 

Niobic  oxide  is  also  produced  by  decomposing  niobic  chloride,  or  oxy- 
chloride, with  water :  when  pure  it  has  a  specific  gravity  of  4-4  to  4-5.  It 


485 

is  an  acid  oxide,  uniting  with  basic  oxides,  and  forming  salts  called  niobates, 
some  of  which  occur  as  natural  minerals  :  columbite,  for  example,  being  a 
ferro-manganous  niobate.  The  potassium  niobates  crystallize  readily,  and 


3Nb205 .  5aq.  as  a  pulverulent  precipitate,  by  boiling  a  solution  of  potassium 
nioboxy-fluoride  with  potassium  carbonate.  The  sodium  niobates  are  crys- 
talline powders  which  decompose  during  washing.  There  is  also  a  sodium 
and  potassium  niobate,  containing  Na20  .  3K20  .  3Nb205.  9aq. 

NIOBIC  CHLORIDE,  NbCl5,  is  obtained,  together  with  the  oxychloride,  by 
heating  an  intimate  mixture  of  niobic  oxide  and  charcoal  in  a  stream  of 
chlorine  gas.  It  is  yellow,  volatile,  and  easily  fusible.  Its  observed  vapor- 
density,  according  to  Deville  and  Troost,  is  9-6  referred  to  air,  or  138-6 
referred  to  hydrogen  as  unity :  by  calculation  for  a  two-volume  condensa- 

Q4-    I     r-\    3'V^ 

tion,  it  is—  _==  135-75.     The  oxychloride,  NbOCl3,  is  white,  vola- 

tile, but  not  fusible :  its  specific  gravity,  referred  to  hydrogen,  is,  by  obser- 
vation, 114-06;  by  calculation,  94  +  ^  +  3.  35-5^  m.2^  Both  thege 
compounds  are  converted  by  water  into  niobic  oxide. 

NIOBIC  OXYFLUORIDE,  NbOF3,  is  formed  by  dissolving  niobic  oxide  in 
hydrofluoric  acid.  It  unites  with  the  fluorides  of  the  more  basic  metals, 
forming  salts  isomorphous  with  the  titanofluorides,  stannofluorides,  and 
tungstofluorides,  1  atom  of  oxygen  in  these  salts  taking  the  place  of  2  atoms 
of  fluorine.  Marignac  has  obtained  five  potassium  nioboxyfluorides,  all 
perfectly  crystallized,  namely: 

2KF.NbOF3.  aq.,  crystallizing  in  monoclinic  plates; 

"  cuboid  forms  (systems  undetermined), 

monoclinic  needles, 

5KF.3NbOF3.aq.  "  hexagonal  prisms, 

4KF.3NbOF3.2aq.         «  triclinic  prisms. 

Potassium  niobofluoride,  3KF.NbF5,  separates  in  shining  monoclinic  nee- 
dles from  a  solution  of  the  first  of  the  nioboxyfluorides  above  mentioned 
in  hydrofluoric  acid.  Nioboxyfluorides  of  ammonium,  sodium,  zinc,  and 
copper  have  also  been  obtained. 

The  isomorphism  of  these  salts  with  the  stannofluorides,  titanofluorides, 
and  tungstofluorides,  shows  clearly  that  the  existence  of  isomorphism  be- 
tween the  corresponding  compounds  of  any  two  elements,  must  not  be 
taken  as  a  decided  proof  that  those  elements  are  of  equal  atomicity :  for 
in  the  case  now  under  consideration,  we  have  isomorphous  salts  formed  by 
tin  and  titanium,  which  are  tetrads,  niobium,  which  is  a  pentad,  and  tung- 
sten, which  is  a  hexad. 


The  compounds  of  niobium  cannot  easily  be  mistaken  for  those  of  any 
other  metal  except  tantalum.  The  most  characteristic  reactions  of  niobates 
and  tantalates  with  liquid  reagents  are  the  following :  — 


436 


PENTAD    METALS. 


Hydrochloric  acid 
Ammonium  chloride  . 


Potassium  ferrocyanide 
"          ferricyanide 

Infusion  of  galls   .     . 


Niobates. 

White  precipitate,  insol- 
uble in  excess. 

Precipitation  slow  and 
incomplete. 

Red  precipitate. 
Bright   yellow    precipi- 
tate. 
Orange-red  precipitate. 


Tantalates. 

White  precipitate,  solu- 
ble in  excess. 

Complete  precipitation 
as  acid  ammonium 
tantalate. 

Yellow  precipitate. 

White  precipitate. 

Light  yellow  precipi- 
tate. 


Niobic  oxide,  heated  with  borax  in  the  outer  blow-pipe  flame,  forms  a 
colorless  bead,  which,  if  the  oxide  is  in  sufficient  quantity,  becomes 
opaque  by  interrupted  blowing  or  naming.  In  microcosmic  salt  it  dissolves 
abundantly,  forming  a  colorless  bead  in  the  outer  flame,  and  in  the  inner 
a  violet-colored,  or  if  the  bead  is  saturated  with  the  oxide,  a  beautiful 
blue  bead,  the  color  disappearing  in  the  outer  flame 


CLASS  VI.— HEX  AD  METALS. 


CHROMIUM. 
Atomic  weight,  52-5.     Symbol,  Cr. 

/CHROMIUM  is  found  in  the  state  of  oxide,  in  combination  with  iron 
\J  oxide,  in  some  abundance  in  the  Shetland  Islands,  and  elsewhere:  as 
lead  chromatc  it  constitutes  a  very  beautiful  mineral,  from  which  it  was 
first  obtained.  The  metal  itself  is  prepared  in  a  half-fused  condition  by 
mixing  the  oxide  with  half  its  weight  of  charcoal-powder,  enclosing  the 
mixture  in  a  crucible  lined  with  charcoal,  and  then  subjecting  it  to  the 
very  highest  heat  of  a  powerful  furnace. 

Deville  has  prepared  metallic  chromium  by  reducing  pure  chromium 
sesquioxide,  by  means  of  an  insufficient  quantity  of  charcoal,  in  a  lime 
crucible.  Thus  prepared,  metallic  chromium  is  less  fusible  than  platinum, 
and  as  hard  as  corundum.  It  is  readily  acted  upon  by  dilute  hydrochloric 
acid,  less  so  by  dilute  sulphuric  acid,  and  not  at  all  by  concentrated 
nitric  acid.  Fre'my  obtained  chromium  in  small  cubic  crystals,  by  the 
action  of  sodium  vapor  on  chromium  trichloride  at  a  red  heat.  The  crys- 
talline chromium  resists  the  action  of  concentrated  acids,  even  of  nitromu- 
riatic  acid. 

Chromium  forms  a  hexfluoride,  Cr^Fg,  and  a  corresponding  oxide, 
Cr^Oj,  analogous  to  sulphuric  oxide  ;  also,  an  acid,  Cr04H2,  analogous  to  sul- 
phuric acid,  with  corresponding  salts,  the  chromates,  which  are  isomorphous 
with  the  sulphates.  In  its  other  compounds,  chromium  resembles  iron,  form- 
ing the  chromic  compounds  Cr2Cl6,  Cr203,  £c.,  in  which  it  is  apparently  triva- 
lent  but  really  quadrivalent,  and  the  chromous  compounds,  CrCl2,  CrO,  &c., 
in  which  it  is  bivalent. 

CHLORIDES.  —  The  dichloride  or  Chromous  chloride,  CrCl2,  is  prepared  by 
heating  the  violet-colored  trichloride,  contained  in  a  porcelain  or  glass 
tube,  to  redness  in  a  current  of  perfectly  dry  and  pure  hydrogen  gas  :  hy- 
drochloric acid  is  then  disengaged,  and  a  white  foliated  mass  is  obtained, 
which  dissolves  in  water  with  great  elevation  of  temperature,  yielding  a 
blue  solution,  which,  on  exposure  to  the  air,  absorbs  oxygen  with  extraor- 
dinary energy,  acquiring  a  deep  green  color,  and  passing  into  the  state 
of  chromic  oxychloride,  Cr2Cl6.Cr203.  Chromous  chloride  is  one  of  the 
most  powerful  reducing  or  deoxidizing  agents  known,  precipitating  calo- 
mel from  a  solution  of  mercuric  chloride,  instantly  converting  tungstic  acid 
into  blue  tungsten  oxide,  and  precipitating  gold  from  a  solution  of  auric 
chloride.  It  forms,  with  ammonia,  a  sky-blue  precipitate  which  turns 
green  on  exposure  to  the  air;  with  ammonia  and  sal-ammoniac,  a  blue 
solution  turning  red  on  exposure  to  the  air  ;  and  with  ammonium  sulphide, 
a  black  precipitate  of  chromous  sulphide. 

The  trichloride  or   Chromic  chloride,  Cr2Cl6.  is  obtained  in  the  anhydrous 
state  by  heating  to  redness  in  a  porcelain  tube  a  mixture  of  chromium  M-S- 
quioxide  and    charcoal,    and   passing  dry  chlorine  gas  ovor   it.      The   tri- 
chloride sublimes,  and  is  deposited  in  the  cool  part  uf  the  tube,  in  the  form 
37  *  437 


438  HEXAD    METALS. 

of  beautiful  crystalline  plates  of  a  pale  violet  color.  It  is  totally  insoluble 
in  water  under  ordinary  circumstances,  even  at  the  boiling-heat.  It  dis- 
solves, however,  and  assumes  the  deep-green  hydrated  state  in  water  con- 
taining an  exceedingly  minute  quantity  of  the  dichloride  in  solution.  The 
hydration  is  marked  by  the  evolution  of  much  heat.  This  remarkable 
effect  must  probably  be  referred  to  the  class  of  actions  known  at  present 
under  the  name  of  catalysis. 

The  green  hydrated  chromic  chloride  is  easily  formed  by  dissolving 
chromic  hydrate  in  hydrochloric  acid,  or  by  boiling  lead  chromate,  or  silver 
chromate,  or  a  solution  of  chromic  acid,  with  hydrochloric  acid  and  a  re- 
ducing agent,  such  as  alcohol,  or  sulphurous  acid,  or  even  with  hydro- 
chloric acid: — 

2Cr03  -f  12HC1  =  Cr2Cl6  -f  60H2  +  C16. 

The  solution  thus  obtained  exhibits  the  same  characters  as  the  chromic 
oxygen-salts.  When  evaporated  it  leaves  a  dark-green  syrup,  which,  when 
heated  to  100°  in  a  stream  of  dry  air,  yields  a  green  mass  containing  Cr2Cl6. 
90H2.  The  same  solution  evaporated  in  a  vacuum  yields  green  granular 
crystals  containing  O2C16.OH2. 

FLUORIDES. — The  trifluoride,  or  Chromic  fluoride,  Cr2F6,  is  obtained  by 
treating  the  dried  sesquioxide  with  hydrofluoric  acid,  and  strongly  heating 
the  dried  mass,  as  a  dark-green  substance,  which  melts  at  a  high  tempera- 
ture, and  sublimes  when  still  more  strongly  heated,  in  shining  regular  oc- 
tohedrons. 

The  hexfluoride,  CrF6,  is  formed  by  distilling  lead  chromate  with  fluorspar 
and  fuming  oil  cf  vitriol  in  a  leaden  retort,  and  condensing  the  vapors  in  a 
cooled  and  dry  leaden  receiver.  It  then  condenses  to  a  blood-red  fuming 
liquid,  which  volatilizes  when  its  temperature  rises  a  few  degrees  higher. 
The  vapor  is  red,  and,  when  inhaled,  produces  violent  coughing  and  severe 
oppression  of  the  lungs.  The  hexfluoride  is  decomposed  by  water,  yield- 
ing hydrofluoric  and  chromic  acids.  A  fluoride,  intermediate  in  composi- 
tion between  the  two  just  described,  is  obtained  in  solution  by  decomposing 
the  brown  dioxide  by  hydrofluoric  acid.  The  solution  is  red,  and  yields  by 
evaporation  a  rose-colored  salt,  which  is  redissolved  without  alteration  by 
water,  and  precipitated  brown  by  ammonia. 

OXIDES. — Chromium  forms  five  oxides,  containing  CrO,  Cr304,  Cr203, 
Cr02,  and  Cr03,  the  first  three  being  analogous  in  composition  to  the  three 
oxides  of  iron. 

The  monoxide,  or  Chromous  oxide,  Cr//0,  is  formed  on  adding  potash  to  a 
solution  of  chromous  chloride,  as  a  brown  precipitate,  which  speedily  passes 
to  deep  foxy-red,  with  disengagement  of  hydrogen,  being  converted  into  a 
higher  oxide.  Chromous  oxide  is  a  powerful  base,  forming  pale-blue  salts, 
which  absorb  oxygen  with  extreme  avidity.  Potassio-chromous  sulphate 
contains  (S04)2>Cr//K2,  like  the  other  members  of  the  same  group. 

Trichromic  tetroxide,  Cr304  =  CrO.Cr203,  is  the  above  mentioned  brownish- 
red  precipitate  produced  by  the  action  of  water  upon  the  monoxide.  The 
decomposition  is  not  complete  without  boiling.  This  oxide  corresponds  with 
the  magnetic  oxide  of  iron,  and  is  not  salifiable. 

Sesquioxide,  or  Chromic  oxide,  Cr203. — When  mercurous  chromate,  pre- 
pared by  mixing  solutions  of  mercurous  nitrate  and  potassium  chromate,  or 
bichromate,  is  exposed  to  a  red  heat,  it  is  decomposed,  pure  chromium  ses- 
quioxide, having  a  fine  green  color,  remaining.  In  this  state  the  oxide  is, 
like  alumina  after  ignition,  insoluble  in  acids.  The  anhydrous  sesquioxide 
may  be  prepared  in  a  beautifully  crystalline  form  by  heating  potassium  bi- 
chromate, K20.2Cr03,  to  full  redness  in  an  earthen  crucible.  One-half  of 


CHROMIUM.  439 

the  chromium  trioxide  contained  in  that  salt  then  suffers  decomposition, 
oxygen  being  disengaged  and  sesquioxide  left.  The  melted  mass  is  then 
treated  with  water,  which  dissolves  out  neutral  potassium  chromate,  and 
the  oxide  is,  lastly,  washed  and  dried.  Chromium  sesquioxide  communicates 
a  fine  green  tint  to  glass,  and  is  used  in  enamel  painting.  The  crystalline 
sesquioxide  is  employed  in  the  manufacture  of  razor-strops.  From  a  solu- 
tion of  chromium  sesquioxide  in  potash,  or  soda,  green  gelatinous  hydrated 
sesquioxide  of  chromium  is  separated  on  standing.  When  finely  powdered 
arid  dried  over  sulphuric  acid,  it  consists  of  Cr.203.60H2.  A  hydrate  may 
also  be  prepared  by  boiling  a  somewhat  dilute  solution  of  potassium  bichro- 
mate strongly  acidulated  with  hydrochloric  acid,  with  small  successive  por- 
tions of  sugar  or  alcohol.  In  the  former  case  carbon  dioxide  escapes:  in  the 
latter,  aldehyde  and  also  acetic  acid  are  formed,  substances  with  which  we 
shall  become  acquainted  in  organic  chemistry ;  and  the  chromic  acid  of  the 
salt  becomes  converted  into  chromium  trichloride,  the  color  of  the  liquid 
changing  from  red  to  deep  green.  The  reduction  may  also  be  effected,  as 
already  observed,  by  hydrochloric  acid  alone.  A  slight  excess  of  ammonia 
precipitates  the  hydrate  from  this  solution.  It  has  a  pale  purplish-green 
color,  which  becomes  full  green  on  ignition ;  an  extraordinary  shrinking  of 
volume  and  sudden  incandescence  are  observed  when  the  hydrate  is  decom- 
posed by  heat. 

Chromium  sesquioxide  is  a  feeble  base,  resembling,  and  isomorphous 
with,  iron  sesquioxide  and  alumina;  its  salts  (chromic  salts)  have  a  green  or 
purple  color,  and  are  said  to  be  poisonous. 

Chromic  sulphate,  (S04)3Cr2,  is  prepared  by  dissolving  the  hydrated  oxide 
in  dilute  sulphuric  acid.  It  unites  with  the  sulphates  of  potassium  and 
ammonium,  giving  rise  to  magnificient  double  salts,  which  crystallize  in 
regular  octohedrons  of  a  deep  claret-color,  and  possess  a  constitution  re- 
sembling that  of  common  alum,  the  aluminium  being  replaced  by  chromium. 
The  ammonium-salt,  for  example,  has  the  composition  (S04)2Cr///(NH4).12 
aq.  The  finest  crystals  are  obtained  by  spontaneous  evaporation,  the  solu- 
tion being  apt  to  be  decomposed  by  heat. 

The  dioxide,  Cr02,  which  is,  perhaps,  a  chromic  chromate,  Cr03 .  Cr203, 
is  a  brown  substance  obtained  by  digesting  chromic  oxide  with  excess  of 
chromic  acid,  or  by  partial  reduction  of  chromic  acid  with  alcohol,  sulphur- 
ous acid,  &c. 

CHROMIUM  TRIOXIDE,  Cr03 ;  in  combination  with  water,  forming  Chromic 
atid,  Cr03.  OH2  =  Cr04H2  =  (Cr02)//(OH)2.  Whenever  chromium  sesqui- 
oxide is  strongly  heated  with  an  alkali,  in  contact,  with  air,  oxygen  is  ab- 
sorbed and  the  trioxide  generated.  Chromium  trioxide  may  be  obtained 
nearly  pure,  and  in  a  state  of  great  beauty,  by  mixing  100  measures  of  a 
cold  saturated  solution  of  potassium  bichromate  with  150  measures  of  oil  of 
vitriol,  and  leaving  the  whole  to  cool.  It  crystallizes  in  brilliant  crimson- 
red  prisms:  the  mother-liquor  is  poured  off,  and  the  crystals  are  placed 
upon  a  tile  to  drain,  being  closely  covered  by  a  glass  or  bell-jar.*  It  is  also 
formed  by  decomposing  the  hexfluoride  with  a  small  quantity  of  water. 
Chromium  trioxide  is  very  deliquescent  and  soluble  in  water :  the  solution 
is  instantly  reduced  by  contact  with  organic  matter. 

Chromic  acid  is  bibasic  and  analogous  in  composition  to  sulphuric  acid ; 
its  salts  are  isomorphous  with  the  corresponding  sulphates. 

Potassium  chromate,  Cr04K2,  or  (Cr02)//(OK)2.  —  This  salt  is  made  directly 
from  the  native  chrome-iron-ore,  which  is  a  compound  of  chromium  sesqui- 
oxide and  ferrous  oxide,  analogous  to  magnetic  iron  ore,  by  calcination  with 
nitre  or  with  potassium  carbonate,  or  with  caustic  lime,  the  ore  being  re- 
duced to  powder  and  heated  for  a  long  time  with  the  alkali  in  a  reverbera- 

* 

*  Warington,  Memoirs  of  the  Chemical  Society,  i.  18. 


440  HEXAD   METALS. 

tory  furnace.  The  product,  when  treated  with  water,  yields  a  yellow  solu- 
tion, which,  by  evaporation,  deposits  anhydrous  crystals  of  the  same  color, 
isomorphous  with  potassium  sulphate.  Potassium  chromate  has  a  cool, 
bitter,  and  disagreeable  taste,  and  dissolves  in  2  parts  of  water  at  15-5°. 

Potassium  bichromate,  or  anhydrochr ornate,  2Cr03.  K.20,  or  Cr04K2  .  Cr03.  — 
When  sulphuric  acid  is  added  to  the  preceding  salt  in  moderate  quantity, 
one  half  of  the  base  is  removed,  and  the  neutral  chromate  converted  into 
bichromate.  The  new  salt,  of  which  immense  quantities  are  manufactured 
for  use  in  the  arts,  crystallizes  by  slow  evaporation  in  beautiful  red  tabular 
crystals,  derived  from  a  prism.  It  melts  when  heated,  and  is  soluble  in  10 
parts  of  water;  the  solution  has  an  acid  reaction. 

Potassium  trichromate,3Cr03.~K.<iO,  or  Cr04K2 .  2Cr03,  maybe  obtained  in 
crystals  by  dissolving  the  bichromate  in  an  aqueous  solution  of  chromic  acid, 
and  allowing  it  to  evaporate  over  sulphuric  acid. 

Lead  chromate,  Cr04Pb//.  —  On  mixing  solutions  of  potassium  chromate  or 
bichromate  with  lead  nitrate  or  acetate,  a  brilliant  yellow  precipitate  falls, 
which  is  the  compound  in  question  ;  it  is  the  chrome-yelloiv  of  the  painter. 
Then  this  compound  is  boiled  with  lime-water,  one  half  of  the  acid  is  with- 
drawn, and  a  basic  lead  chromate  of  an  orange-red  color  left.  The  basic 
chromate  is  also  formed  by  adding  lead  chromate  to  fused  nitre,  and  after- 
wards dissolving  out  the  soluble  salts  by  water:  the  product  is  crystalline, 
and  rivals  vermilion  in  beauty  of  tint.  The  yellow  and  orange  chrome- 
colors  are  fixed  upon  cloth  by  the  alternate  application  of  the  two  solutions, 
and  in  the  latter  case  by  passing  the  dyed  stuff  through  a  bath  of  boiling 
lime-water. 

Silver  chromate,  Cr04Ag2.  — This  salt  precipitates  as  a  reddish-brown  pow- 
der when  solutions  of  potassium  chromate  and  silver  nitrate  are  mixed. 
It  dissolves  in  hot  dilute  nitric  acid,  and  separates,  on  cooling,  in  small 
ruby-red  platy  crystals.  The  chrornates  of  barium,  zinc,  and  mercury  are 
insoluble ;  the  first  two  are  yellow,  the  last  is  brick-red. 

CHROMIUM  DIOXYDICHLORIDE,  Cr02Cl2,  commonly  called  Chlorochromic 
acid.  —  When  3  parts  of  potassium  bichromate  and  3£  parts  of  common  salt 
are  intimately  mixed  and  introduced  into  a  small  glass  retort,  9  parts  of  oil 
of  vitriol  then  added,  and  heat  applied  as  long  as  dense  red  vapors  arise, 
this  compound  passes  over  as  a  heavy  deep-red  liquid  resembling  bromine: 
it  is  decomposed  by  water,  with  production  of  chromic  and  hydrochloric 
acids  It  is  analogous  to  the  so-called  chloromolybdic,  chlorotungstic,  and 
chlorosulphuric  acids  in  composition,  and  in  the  products  which  it  yields 
when  decomposed.  It  may  be  regarded  as  formed  from  the  trioxide  by 
substitution  of  C12  for  0,  or  from  chromic  acid,  (Cr02)//(OH)2,  by  substitu- 
tion of  C12  for  (OH)2;  also  as  a  compound  of  chromium  hexchloride  (not 
known  in  the  separate  state),  with  chromium  trioxide:  CrC]6.2Cr03  — 
3002C12. 

PERCHROMIC  ACID  is  obtained,  according  to  Barreswil,  by  mixing  chromic 
acid  with  dilute  hydrogen  oxide,  or  potassium  bichromate  with  a  dilute  but 
very  acid  solution  of  barium  dioxide  in  hydrochloric  acid;  a  liquid  is  then 
formed  of  a  blue  color,  which  is  removed  from  the  aqueous  solution  by 
ether.  This  very  unstable  compound  has  perhaps  the  composition  Cr208H2 
or  Cr207.  OH2,  analogous  to  that  of  permanganic  acid. 


Reactions  of  Chromium  compounds.  —  A  solution  of  chromic  chloride  or  a 
chromic  oxygen  salt  is  not  precipitated  or  changed  in  any  way  by  hydrogen 
sulphide.  Ammonium  sulphide  throws  down  a  grayish-green  precipitate  of 
chromic  hydrate.  Caustic  fixed  alkalies  also  precipitate  the  hydrated  oxide, 
and  dissolve  it  easily  when  added  in  excess.  Ammonia,  the  same,  but  nearly 


TUNGSTEN",    OR    WOLFRAM. 

insoluble.  The  carbonates'  of  potassium,  sodium,  and  ammonium  also  throw 
down  a  green  precipitate  of  hydrate,  slightly  soluble  in  a  large  excess. 

Chromous  salts  are  but  rarely  meth  with ;  for  their  reactions,  see  Chro- 
mium dichloride,  p.  437. 

Chromic  acid  and  its  salts  are  easily  recognized  in  solution  by  forming  a 
pale  yellow  precipitate  with  barium  salts,  bright  yellow  with  lead  salts,  brick- 
red  with  mcrcurous  salts,  and  crimson  with  silver  salts  ;  also  by  their  capa- 
bility of  yielding  the  green  sesquioxide  by  reduction. 

All  chromium  compounds,  ignited  with  a  mixture  of  nitre  and  an  alka- 
line carbonate,  yield  an  alkaline  chromate,  which  may  be  dissolved  out  by 
water,  and  on  being  neutralized  with  acetic  acid,  will  give  the  reactions 
just  mentioned. 

The  oxides  of  chromium  and  their  salts,  fused  with  borax  in  either  blow- 
pipe flame,  yield  an  emerald-green  glass.  The  same  character  is  exhibited 
by  those  salts  of  chromic  acid  whose  bases  do  not  of  themselves  impart  a 
decided  color  to  the  bead.  The  production  of  the  green  color  in  both 
flames  distinguishes  chromium  from  uranium  and  vanadium,  which  give 
green  beads  in  the  inner  flame  only. 


TUNGSTEN,  or  WOLFRAM. 
Atomic  weight,  184.     Symbol,  W. 

TUNGSTEX  is  found,  as  ferrous  tungstate,  in  the  mineral  wolfram,  tolerably 
abundant  in  Cornwall ;  occasionally  also  as  calcium  tungstate  (scheelite  or 
tungsten),  and  as  lead  tungstate  (scheeletine).  Metallic  tungsten  is  obtained 
in  the  state  of  a  dark-gray  powder,  by  strongly  heating  tungstic  oxide  in 
a  stream  of  hydrogen,  but  requires  for  fusion  an  exceedingly  high  tem- 
perature. It  is  a  white  metal,  very  hard  and  brittle :  it  has  a  density  of 
17-4.  Heated  to  redness  in  the  air,  it  takes  fire  and  reproduces  tung- 
stic oxide. 

Tungsten  forms  two  classes  of  compourids,  in  which  it  is  quadrivalent 
and  sexvalent  respectively,  and  a  third  class,  of  intermediate  composition, 
in  which  it  is  apparently  quinquivalent. 

CHLORIDES.  —  These  compounds  are  formed  by  heating  metallic  tungsten 
in.  chlorine  gas.  The  he.cchloride  or  tungstic  chloride,  WC16,  is  also  produced, 
together  with  oxy chloride,  by  the  action  of  chlorine  on  an  ignited  mixture 
of  tungstic  oxide  and  charcoal.  The  oxychlorides,  being  more  volatile 
than  the  hexchloride,  may  be  separated  from  it  by  sublimation.  The  hex- 
chloride  forms  dark  violet  scales  or  fused  crusts  having  a  bluish-black  me- 
tallic iridescence.  By  contact  with  water  or  moist  air,  it  is  converted  into 
hydrochloric  and  tungstic  acids.  The  tetrachloride,  WC14,  is  formed,  accord- 
ing to  some  authorities,  as  a  dark -red  compound,  when  tungsten  is  heated 
in  chlorine  gas  ;  but  according  to  others,  this  red  compound  is  a  pcnta- 
chloride,  W2C1JO,  or  WC14.WC16,  the  tetrachloride  not  being  known  in  the 
separate  state. 

The  bromides  of  tungsten  are  analogous  to  the  chlorides.  — The  hcxfl>t<>ri<1r, 
WF6,  is  obtained  by  evaporating  a  solution  of  tungstic  acid  in  hydrofluoric 
acid. 

OXIDES.  —Tungsten  forms  three  oxides,  W02,  W03,  and  W205,  neither  of 
which  exhibits  basic  properties,  so  that  there  are  no  tungsten  salts  in  which 
the  metal  replaces  the  hydrogen  of  an  acid,  or  takes  the  electro-positive 
part.  The  trioxide  exhibits  decided  acid  tendencies,  uniting  with  basic 
metallic  oxides,  and  forming  crystallizable  salts  called  tungstates.  The 
pentoxide  may  be  regarded  as  a  compound  of  the  other  two. 


, 

cipitate  of  tungstic,  monohydrate  or  tungstic  acid,  W04H2,  3  .        2. 

dilute  solutions,  on  the  other  hand,  yield  with   acids  a 


442  HEXAD    METALS. 

The  dioxide,  or  Tungstous  oxide,  W03,  is  most  easily  prepared  by  exposing 
tungstic  oxide  to  hydrogen,  at  a  temperature  not  exceeding  dull  redness. 
It  is  a  brown  powder,  sometimes  assuming  a  crystalline  appearance  and  an 
imperfect  metallic  lustre.  It  takes  fire  when  heated  in  the  air,  and  burns, 
like  the  metal  itself,  to  tungstic  oxide.  It  forms  a  definite  compound  with 
soda. 

The  trioxide,  or  Tungstic  oxide,  WO3,  is  most  easily  prepared  from  native 
calcium  tungstate  by  digestion  in  nitric  or  hydrochloric  acid,  the  soluble 
calcium-salt  thereby  produced  being  washed  out  with  water,  and  the  re- 
maining tungstic  acid  ignited.  From  wolfram  it  may  be  prepared  by 
repeatedly  digesting  the  mineral  in  strong  hydrochloric  acid,  ultimately 
with  addition  of  a  little  nitric  acid,  to  dissolve  out  the  iron  and  manga- 
nese ;  dissolving  the  remaining  tungstic  acid  in  aqueous  ammonia  ;  evapo- 
rating to  dryness  ;  and  heating  the  residual  ammonium  tungstate  in  con- 
tact with  the  air.  Tungstic  oxide  is  a  yellow  powder  insoluble  in  water, 
and  in  most  acids,  but  soluble  in  alkalies.  The  hot  solutions  of  the  result- 
ing alkaline  tungstate,  when  neutralized  with  an  acid,  yield  a  yellow  pre- 

ungstic acid,  W04H2,  or  W03  .  OH2.  Cold 
yield  with   acids  a  white  precipitate, 
hydrated  tungstic    acid,    W03  .  20H2,    or 
W04H2  .  OH2.     Tungstic  acid  reddens  litmus  and  dissolves  easily  in  alkalis. 

Tungstates.  —  Tungstic  acid  unites  with  bases  in  various,  and  often  in 
very  unusual  proportions.  It  is  capable  of  existing  also  in  two  isomeric 
modifications,  viz  :  1.  Ordinary  tungstic  acid,  which  is  insoluble  in  water, 
and  forms  insoluble  salts  with  all  metals,  except  the  alkali-metals  and  mag- 
nesium ;  2.  Metatungstic  acid,  which  is  soluble  in  water,  and  forms  soluble 
salts  with  nearly  all  metals.  Ordinary  tungstic  acid  forms  normal  salts 
containing  W04M2  orW03.M20,  and  acid  salts  containing  7WO3.3M20, 
which  may  perhaps  be  regarded  as  double  salts  composed  of  diacid  and 
triacid  tungstates,  that  is,  as  2(2W03  .  M20)  -f-  3W03.  M20.  The  tung- 
stat.es  of  potassium  and  sodium,  especially  the  latter,  are  sometimes  used 
as  mordants  in  dyeing,  in  place  of  stannates  ;  also  for  rendering  muslin 
and  other  light  fabrics  uninflammable.  Tungstous  tungstate,  WO3.  WO2, 
which  has  the  composition  of  tungsten  pentoxide,  W205,  is  a  blue  sub- 
stance produced  by  reducing  tungstic  oxide  or  tungstic  acid  with  zinc 
and  hydrochloric  acid  ;  also  by  heating  ammonium  tungstate  to  redness  in 
a  retort. 

Metatung  'states.  —  These  salts,  which  have  the  composition  of  quadacid 
tungstates,  4W03  .  M20,  are  formed  from  ordinary  tungstates  by  addition 
of  tungstic  acid,  or  by  removing  part  of  the  base  by  means  of  an  acid. 
They  are  for  the  most  part  soluble  and  crystallizable.  By  decomposing 
barium  metatungstate  with  dilute  sulphuric  acid,  and  evaporating  the 
filtrate  in  a  vacuum,  hydrated  metatungstic  acid  is  obtained  in  quadratic 
octohedrons  apparently  containing  4W03.  OH2  -f-  31  aq.  ;  it  is  very  soluble 
in  water. 

Silicotung  states.*  —  By  boiling  gelatinous  silica  with  acid  potassium  tungs- 
tate, a  crystalline  salt  is  obtained,  having  the  composition  of  a  diacid  potas- 
sium tungstate,  6(2W03.  K?0),  or  12W03.K206,  in  which  one  third  of  the 
potassium  is  replaced  by  silicium,  viz.,  12W03.  K8Siiv06,  so  that  the  silicium 
here  enters  as  a  basylous  element.  The  resulting  solution  yields  with  mer- 
curous  nitrate  a  precipitate  of  mercurous  silicotung  state  ;  this,  when  decom- 
posed by  an  equivalent  quantity  of  hydrochloric  acid,  yields  a  solution  of 
hydrogen  silicotung  state  or  silicotung  stic  acid;  and  the  other  silicotungstates, 
which  are  all  soluble,  are  obtained  by  treating  the  acid  with  carbonates. 

Silicodecitungstic  acid,  10W03  .  H8Siiv06,  is  obtained  as  an  ammonium-salt 

*  Marignac,  Ann.  Chim.  Phys.  [4]  iii.  5  ;  Watts's  Dictionary  of  Chemistry,  v.  913. 


TUNGSTEN,    OR   WOLFRAM.  443 

by  boiling  gelatinous  silica  with  solution  of  acid  ammonium  tungstate  ;  and 
from  this,  the  acid  and  its  other  salts  may  be  obtained  in  the  same  manner 
as  the  preceding.  The  silicodecitungstates  are  very  unstable,  and  the  acid 
is  decomposed  by  mere  evaporation,  depositing  silica,  and  being  converted 
into  tungsto- silicic  acid,  which  is  isomeric  with  silicotungstic  acid,  and  like- 
wise decomposes  carbonates.  All  three  of  these  acids  are  capable  of  ex- 
changing either  one-half  or  the  whole  of  their  basic  hydrogen  for  metals, 
thereby  forming  acid  and  neutral  salts;  silicotungstic  acid  also  forms  an 
acid  sodium-salt  in  which  only  one-fourth  of  the  hydrogen  is  replaced  by 
sodium. 

TUNGSTEN  SULPHIDES.  —  The  disulphide,  or  Tungstous  sulphide,  WS2,  is  ob- 
tained in  soft  black  needle-shaped  crystals  by  igniting  tungsten,  or  one  of 
its  oxides,  with  sulphur. 

The  trisulphide,  or  Tungstic  sulphide,  WS3,  is  formed  by  dissolving  tungstic 
acid  in  ammonium  sulphide,  and  precipitating  with  an  acid,  or  by  adding 
hydrochloric  acid  to  the  solution  of  an  alkaline  tungstate  saturated  with 
hydrogen  sulphide.  It  is  a  light-brown  precipitate,  turning  black  when  dry. 
It  unites  easily  with  basic  metallic  sulphides,  forming  the  sulphotung states, 
WS4M2,  analogous  to  the  normal  tungstates. 


Reactions  of  Tungsten  compounds.  —  Soluble  tungstates,  or  metatungstates, 
supersaturated  with  sulphuric,  hydrochloric,  phosphoric,  oxalic,  or  acetic 
acid,  yield,  on  the  introduction  of  a  piece  of  zinc,  a  beautiful  blue  color, 
arising  from  the  formation  of  blue  tungsten  oxide.  A  soluble  tungstate, 
mixed  with  ammonium  sulphide,  and  then  with  excess  of  acid,  yields  a  light- 
brown  precipitate  of  tungstic  sulphide,  soluble  in  ammonium  sulphide. 
Hydrogen  sulphide  does  not  precipitate  the  acidulated  solution  of  a  tungstate, 
but  turns  it  blue,  owing  to  the  formation  of  the  blue  oxide.  Ordinary  tung- 
states give  with  potassium  ferrocyanide,  after  addition  of  hydrochloric  acid, 
a  brown  flocculent  precipitate,  soluble  in  pure  water  free  from  acid ;  meta- 
tungstates give  no  precipitate.  Acids  added  to  solutions  of  ordinary  tung- 
states, throw  down  a  white  or  yellow  precipitate  of  tungstic  acid ;  with 
metatungstates  no  precipitate  is  obtained. 

All  tungsten  compounds  form  colorless  beads  with  borax  and  phos- 
phorus salt,  in  the  outer  blowpipe  flame.  With  borax,  in  the  inner  flame, 
tliey  fofm  a  yellow  glass,  if  the  quantity  of  tungsten  is  somewhat  consider- 
able, but  colorless  with  a  smaller  quantity.  With  phosphorus  salt  in  the 
inner  flame  they  forma  glass  of  a  pure  blue  color,  unless  metallic  oxides  are 
present,  which  modify  it ;  in  presence  of  iron  the  glass  is  blood-red,  but 
the  addition  of  metallic  tin  renders  it  blue. 


Steel,  alloyed  with  a  small  quantity  of  tungsten,  acquires  extraordinary 
hardness.  Wootz,  or  Indian  steel,  contains  tungsten.  Tungsten  has  also  a 
remarkable  effect  on  steel  in  increasing  its  power  of  retaining  magnetism 
when  hardened.  A  horse-shoe  magnet  of  ordinary  steel  weighing  two 
pounds  is  considered  of  good  quality  when  it,  bears  seven  times  its  own 
weight;  but,  according  to  Siemens,  a  similar  magnet  made  with  steel  con- 
taining tungsten  may  be  made  to  carry  twenty  times  its  weight  suspended 
from  the  armature.* 

*  Journal  of  the  Chemical  Society,  July,  1868.    2d  Series,  vol.  vi.  p.  284. 


444  HEXAD    METALS. 


MOLYBDENUM. 

Atomic  weight,  92.     Symbol,  Mo. 

This  metal  occurs  in  small  quantity  as  sulphide  and  as  lead  molybdate. 
Metallic  molybdenum  is  obtained  by  exposing  molybdic  oxide  in  a  charcoal- 
lined  crucible  to  the  most  intense  heat  that  can  be  obtained.  It  is  a  white, 
brittle,  and  exceedingly  infusible  metal,  having  a  density  of  8-6,  and  oxid- 
izing, when  heated  in  the  air,  to  molybdic  oxide. 

CHLORIDES.  —  Molybdenum  forms  three  chlorides,  containing  MoCl2,  Mo2 
C16,  and  MoCl4.  The  tetrachloride,  or  molybdic  chloride,  is  obtained  in  dark 
metallically  lustrous  crystals  by  passing  chlorine  in  excess  over  gently  heated 
molybdenum ;  when  heated  in  a  stream  of  hydrogen,  it  is  reduced  to  the 

MoCl3 
dark  copper-colored  trichloride,    I         .    The  dichloride,  or  molybdous  chloride, 

MoCl3 

is  obtained,  though  not  in  the  pure  state,  by  exposing  the  trichloride  to  a 
moderate  heat  in  an  atmosphere  of  carbon  dioxide,  or  by  heating  metallic 
molybdenum  with  calomel.  In  solution  it  is  obtained  by  saturating  hydro- 
chloric acid  with  molybdous  hydrate. 

The  bromides  of  molybdenum  correspond  in  composition  to  the  chlorides  ; 
there  is  also  an  oxybromide  containing  MoT'Br202. 

FLUORIDES.  —  Molybdenum  forms  three  fluorides,  MoF2,  MoF4,  MoF6, 
which  are  obtained  by  dissolving  the  corresponding  oxides  in  hydrofluoric 
acid.  The  hexfluoride  is  not  known  in  the  free  state,  but  only  in  combina- 
tion with  basic  metallic  fluorides  and  molybdates;  thus  there  is  a  po- 
tassium salt  containing  Mo04K2.  MoF8K2. 

OXIDES. —  Molybdenum  forms  the  three  oxides,  Mo/X0,  MoiT02,  and 
Movi03,  besides  several  oxides  intermediate  between  the  last  two,  which 
may  be  regarded  as  molybdic  molybdates. 

The  monoxide,  or  Molybdous  oxide,  MoO,  is  produced  by  bringing  the  di- 
oxide or  trioxide,  in  presence  of  one  of  the  stronger  acids,  in  contact  with 
any  of  the  metals  which  decompose  water.  Thus,  when  zinc  is  immersed  in 
a  concentrated  solution  of  an  alkaline  molybdate  mixed  with  a  quantity  of 
hydrochloric  acid  sufficient  to  redissolve  the  precipitate  first  thrown  down, 
zinc  chloride  and  molybdous  chloride  are  formed.  The  dark-colored  solu- 
tion thus  obtained  is  mixed  with  a  large  quantity  of  caustic  potash,  which 
precipitates  a  black  hydrated  molybdous  oxide,  and  retains  the  zinc  oxide 
in  solution.  The  freshly  precipitated  hydrate  is  soluble  in  acids  and  am- 
monium carbonate;  when  heated  in  the  air  it  burns  to  dioxide,  but  when 
dried  in  a  vacuum  it  leaves  the  black  anhydrous  monoxide. 

The  dioxide,  or  Molybdic  oxide,  Mo02,  is  obtained  in  the  anhydrous  state  by 
heating  sodium  molybdate  with  sal-ammoniac,  the  molybdic  trioxide  being 
reduced  to  dioxide  by  the  hydrogen  of  the  ammoniacal  salt ;  or,  in  the  hy- 
drated state,  by  digesting  metallic  copper  in  a  solution  of  molybdic  acid  in 
hydrochloric  acid,  until  the  liquid  assumes  a  red  color,  and  then  adding  a 
large  excess  of  ammonia.  The  anhydrous  dioxide  is  deep  brown,  and  in- 
soluble in  acids ;  the  hydrate  resembles  ferric  hydrate,  and  dissolves  in 
acids,  yielding  red  solutions.  It  is  converted  into  molybdic  acid  by  strong 
nitric  acid. 

Trioxide,  Mo03.  —  To  obtain  this  oxide  (commonly  called  Molybdic  acid), 
native  molybdenum  sulphide  is  roasted,  at  a  red  heat,  in  an  open  vessel, 
and  the  impure  molybdic  trioxide  thence  resulting  is  dissolved  in  ammonia. 
The  filtered  solution  is  evaporated  to  dryness,  and  the  salt  is  taken  up  by 


MOLYBDENUM.  445 

water,  and  purified  by  crystallization.  It  is,  lastly,  decomposed  by  heat, 
and  the  ammonia  expelled.  The  trioxide  may  also  be  prepared  by  decom- 
posing native  lead  molybdate  with  sulphuric  acid.  It  is  a  white  crystalline 
powder,  fusible  at  a  red  heat,  and  slightly  soluble  in  water.  The  solution 
contains  molybdic  acid;  but  this  acid,  or  hydrate,  is  not  known  in  the  solid 
state.  The  trioxide  is  easily  dissolved  by  alkalies,  and  forms  two  series  of 
salts,  viz.,  normal  or  neutral  molybdates,  Mo04R2,  or  Mo03.  R20,  and  anltydro- 
molybdates  or  bimolybdates,  Mo04R2.  Mo03,  or  2Mo03.  R2O,  the  symbol  R  de- 
noting a  univalent  metal.  The  neutral  molybdates  of  the  alkali-metals  are 
easily  soluble  in  water,  and  their  solutions  yield,  with  the  stronger  acids,  a 
precipitate  either  of  a  less  soluble  bimolybdate,  or  of  the  anhydrous  tri- 
oxide. The  other  molybdates  are  insoluble,  and  are  obtained  by  precipita- 
tion. Lead  molybdate,  Mo4Pb,  occurs  native  in  yellow  quadratic  plates  and 
octohedrons. 

SULPHIDES.  —  Molybdenum  forms  three  sulphides,  MoS2,  MoS3,  and  MoS4, 
the  last  two  of  which  are  acid  sulphides,  forming  sulphur-salts.  The  di- 
sulphide,  or  Molybdic  sulphide,  MoS2,  occurs  native,  as  molybdenite,  in  crystallo- 
laminar  masses,  or  tabular  crystals,  having  a  strong  metallic  lustre  and 
lead-gray  color,  and  forming  a  gray  streak  on  paper  like  plumbago.  The 
same  compound  is  produced  artificially  by  heating  either  of  the  higher 
sulphides,  or  by  igniting  the  trioxide  with  sulphur.  When  roasted  in  con- 
tact with  the  air,  it  is  converted  into  trioxide. 

The  trisulphide,  MoS3,  commonly  called  sulphomolybdic  add,  is  obtained  by 
passing  hydrogen  sulphide  into  a  concentrated  solution  of  an  alkaline  mo- 
lybdate, and  precipitating  with  an  acid.  It  is  a  black-brown  powder, 
which  is  dissolved  slowly  by  alkalies,  more  easily  by  alkaline  sulphides  and 
sulph-hydrates,  forming  sulphur-salts  called  sulphomolybdates.  Most  of 
these  salts  have  the  composition  MoS4R2,  or  MoS3.R2S,  analogous  to  that 
of  the  molybdates.  The  sulpho-molybdates  of  the  alkali-metals,  alkaline 
earth-metals,  and  magnesium,  are  soluble  in  water,  forming  solutions  of  a 
fine  red  color ;  the  rest  are  insoluble. 

Tetrasidphide,  MoS4.  —  This  is  also  an  acid  sulphide,  forming  salts  called 
persulphomolybdates,  the  general  formula  of  which  is  MoS.Rr  or  MoS4 .  R2S. 
The  potassium-salt  is  obtained  by  boiling  the  sulpho-molybdate  with  molyb- 
denum trisulphide,  washing  the  resulting  precipitate  till  the  wash-water 
gives  a  red  fiocculent  precipitate  with  hydrochloric  acid,  and  then  digest- 
ing the  residue  with  cold  ivater,  which  dissolves  out  potassium  persulpho- 
molybdate,  and  leaves  the  disulphide.  The  solution  of  this  potassium  salt, 
treated  with  hydrochloric  acid,  yields  a  dark-red  precipitate  of  molybdenum 
tetrasulphide,  which  dissolves  in  alkalies. 


Molybdenum  in  solution  is  characterized  as  follows: 

Molybdous  salts,  obtained  by  dissolving  molybdous  oxide  in  acids,  are 
opaque  and  almost  black.  They  yield,  with  hydrogen  sulphide,  a  brown- 
black  precipitate  soluble  in  ammonium  sulphide  ;  with  alkalies  and  alkaCne. 
carbonates,  a  brownish-black  precipitate  of  molybdous  hydrate,  easily  soluble 
in  acid  potassium  carbonate,  or  in  ammonium  carbonate  ;  with  potassium 
ferrocyanide,  a  dark-brown  precipitate;  with  sodium  phosphate,  a  white  pre- 
cipitate. 

Solutions  of  molybdic  salts  have  a  reddish-brown  color.  When  heated  in 
the  air,  they  have  a  tendency  to  become  blue  by  oxidation.  In  contact 
with  metallic  zinc,  they  first  blacken  and  then  yield  a  black  precipitate  of 
molybdous  hydrate.  Their  reactions  with  <ilk(tli<-*,  hydrogen  sulphide,  £c., 
are  similar  to  those  of  molybdous  salts;  but  the  precipitates  are  lighter  iu 
color. 

38 


446  HEXAD   METALS. 

Molybdates  are  colorless  unless  they  contain  a  colored  base.  Solutions  of 
the  alkaline  molybdates  yield  with  acids  a  precipitate  of  molybdic  trioxide, 
soluble  in  excess  of  the  precipitant.  They  are  colored  yellow  by  hydrogen 
sulphide,  from  formation  of  a  sulphomolybdate  of  the  alkali-metal,  and  then 
yield  with  acids  a  brown  precipitate  of  molybdenum  trisulphide.  This  is 
an  extremely  delicate  test  for  molybdic  acid.  They  form  white  precipitates 
with  the  salts  of  the  earth-metals,  and  precipitates  of  various  colors  with 
salts  of  the  heavy  metals;  e.g.,  white  with  lead  and  silver  salts;  yellow 
with  ferric  salts;  and  yellowish-white  with  mercurous  salts.  When  ortho- 
phosphoric  acid,  or  a  liquid  containing  it,  is  added  to  the  solution  of  ammo- 
nium molybdate,  together  with  an  excess  of  hydrochloric  acid,  the  liquid 
turns  yellow,  and  after  a  while  deposits  a  yellow  precipitate  of  molybdic 
trioxide,  combined  with  small  quantities  of  phosphoric  acid  and  ammonia. 
This  precipitate  is  soluble  in  ammonia  and  likewise  in  excess  of  the  phos- 
phate. The  reaction  is  therefore  especially  adapted  for  the  detection  of 
small  quantities  of  phosphoric  acid.  The  pyrophosphates  and  metaphos- 
phates  do  not  produce  the  yellow  precipitate.  Arsenic  acid  gives  a  similar 
reaction. 

All  the  oxides  of  molybdenum  form,  with  borax,  in  the  outer  blowpipe 
flame,  a  bead  which  is  yellow  while  hot,  and  colorless  on  cooling;  in  the 
inner  flame,  a  dark  brown  bead,  which  is  opaque  if  excess  of  molybdenum 
is  present.  By  long-continued  heating,  the  molybdic  oxide  may  be  sepa- 
rated in  dark  brown  flakes,  floating  in  the  clear  yellow  glass.  With  phos- 
phorus salt  in  the  outer  flame,  all  oxides  of  molybdenum  give  a  bead  which 
is  greenish  while  hot,  and  colorless  on  cooling ;  in  the  inner  flame  a  clear 
green  bead,  from  which  molybdic  oxide  cannot  be  separated  by  continued 
heating. 


PART   III. 

ORGANIC  CHEMISTRY. 


INTRODUCTION. 

THE  term  "  Organic  Chemistry "  originally  denoted  the  chemistry  of 
compounds  formed  in  the  bodies  of  plants  and  animals.  The  peculiar 
characters  of  the  compounds  thus  formed,  and  the  failure  of  the  earlier 
attempts  to  produce  them  by  artificial  means,  led  to  the  erroneous  idea  that 
their  formation  was  due  to  a  mysterious  power  called  "vital  force,"  sup- 
posed to  reside  in  the  living  organism,  and  to  govern  all  the  changes  and 
processes  taking  place  within  it.  In  accordance  with  this  idea,  the  chem- 
istry of  organic  compounds,  including  those  which  were  formed  by  artificial 
processes  from  the  products  of  vegetable  and  animal  life,  was  erected  into 
a  special  branch  of  chemical  science. 

Later  researches  have,  however,  shown  that  a  large  number  of  compounds, 
formerly  regarded  as  producible  only  under  the  influence  of  the  so-called 
vital  force,  may  be  formed  either  by  direct  combination  of  their  elements, 
or  by  chemical  transformation  of  inorganic  compounds. 

The  first  step  in  the  formation  of  organic  compounds  from  their  elements 
was  made  by  Wb'hler,  who  showed,  in  1828,  that  urea,  the  characteristic 
constituent  of  urine,  can  be  produced  by  molecular  transformation  of  am- 
monium cyanate.  This  experiment,  viewed  in  connection  with  the  fact 
established  about  twelve  years  afterwards,  that  cyanogen  (CN)  can  be 
formed  by  direct  combination  of  its  elements,  is  conclusive  of  the  pos- 
sibility of  forming  a  product  of  the  living  organism  from  inorganic  mate- 
r.ials.  More  recently  it  has  been  shown  that  ethine,  or  acetylene,  C2H2, 
can  be  produced  by  the  direct  combination  of  carbon  and  hydrogen;  that 
this  compound  can  be  made  to  take  up  two  additional  atoms  of  hydrogen 
to  form  ethene,  C2H4 ;  and  that  this  latter  compound  can  be  converted  into 
alcohol,  C2IT60.  a  body  formerly  supposed  to  be  producible  only  by  the 
fermentation  of  sugar;  and  from  this  a  large  number  of  other  compounds 
can  be  produced  by  the  action  of  various  reagents.  The  researches  of 
Berthelot,  Kolbe,  Wurtz,  and  other  distinguished  chemists  have  led  to  the 
discovery  of  a  large  number  of  other  cases  of  the  formation  of  organic 
compounds,  often  of  great  complexity,  from  substances  of  purely  mineral 
origin,  and  ultimately  from  the  elements  themselves.  The  division  of  com- 
pounds into  two  distinct  branches,  inorganic  and  organic  —  formed  accord- 
ing to  distinct  laws,  the  former  being  artificially  producible  by  direct  com- 
bination of  their  elements,  the  latter  only  under  the  influence  of  a  sup- 
posed vital  force  —  must  therefore  be  abandoned.  There  is,  indeed,  but 
one  science  of  chemistry,  of  which  the  study  of  the  compounds  called  or- 
ganic forms  a  part. 

Organic  chemistry  is  in  fact  the  chemistry  of  carbon-compounds,  ami,  in 
a  strictly  systematic  arrangement,  these  compounds  should  be  described  in 
connection  with  the  element  carbon  itself.  But  the  compounds  into  which 

447 


448  THE    ELEMENTARY    OR    ULTIMATE 

carbon  enters  are  so  numerous,  their  constitution  and  the  transformations 
which  they  undergo  under  the  influence  of  heat  and  of  chemical  reagents, 
are,  in  many  instances,  so  complicated,  that  it  is  found  best,  for  the  pur- 
poses of  instruction,  to  defer  their  consideration  till  the  other  elements 
and  their  compounds  have  been  studied. 

It  is  important,  in  this  place,  to  mark  the  distinction  between  organic 
compounds  and  organized  bodies.  Organic  bodies,  such  as  marsh  gas,  ethene, 
benzene,  alcohol,  sugar,  morphine,  &c.,  are  definite  chemical  compounds, 
many  of  which,  as  already  observed,  may  be  formed  by  artificial  methods; 
those  which  are  solid  can,  for  the  most,  part,  be  crystallized;  those  which 
are  liquid  exhibit  constant  boiling  points.  Organized  bodies,  on  the  con- 
trary, always  consist  of  mixtures  of  several  definite  compounds.  They 
never  crystallize,  but  exhibit  a  fibrous  or  cellular  structure,  and  cannot  be 
reduced  to  the  liquid  or  gaseous  state  without  complete  decomposition. 
LastlylTthey  are  organs,  or  parts  of  organs,  which  are  essentially  products 
of  vitality,  and  there  is  not  the  slightest  prospect  of  their  ever  being  pro- 
duced by  artificial  means. 

The  study  of  the  composition  and  chemical  relations  of  organized  bodies 
belongs  to  a  special  department  of  the  science  called  "  Physiological  Chem- 
istry," which  bears  the  same  relation  to  Organic  Chemistry  that  Chemical 
Geology  bears  to  Mineralogy. 


THE  ELEMENTARY  OR  ULTIMATE  ANALYSIS   OF  ORGANIC 
COMPOUNDS. 

Organic  compounds  contain,  for  the  most  part,  only  a  small  number  of 
elements.  Many  consist  only  of  carbon  and  hydrogen.  A  very  large  num- 
ber, including  most  of  those  which  occur  ready  formed  in  the  bodies  of 
plants  and  animals,  consist  of  carbon,  hydrogen,  and  oxygen ;  others  con- 
sist of  carbon,  hydrogen,  and  nitrogen.  Others,  again,  including  most  of 
the  proximate  principles  of  the  animal  organism,  consist  of  four  elements, 
carbon,  hydrogen,  oxygen,  and  nitrogen.  Some  contain  sulphur,  phos- 
phorus, chlorine,  and  metallic  elements ;  in  fact,  artificially  prepared  car- 
bon compounds  may  contain  any  elements  whatever.  Moreover,  even  those 
which  contain  only  a  small  number  of  elements  often  exhibit  great  com- 
plexity of  structure,  in  consequence  of  the  accumulation  of  a  large  num- 
ber of  carbon-atoms  in  the  same  molecule. 

Determination  of  Carbon  and  Hydrogen.  —  The  quantities  of  these  ele- 
ments are  determined  by  burning  a  known  weight  of  the  body  to  be  examined, 
in  such  a  manner  as  to  convert  the  whole  of  the  carbon  into  carbon  dioxide, 
and  the  whole  of  the  hydrogen  into  water.  These  products  are  collected 
and  their  weights  determined,  and  from  the  data  thus  obtained  the  quanti- 
ties of  carbon  and  hydrogen  present  in  the  organic  substance  are  calcu- 
lated. When  nitrogen,  sulphur,  phosphorus,  chlorine,  &c.,  are  present, 
special  and  separate  means  are  resorted  to  for  their  estimation. 

The  method  to  be  described  for  the  determination  of  the  carbon  and 
hydrogen  owes  its  convenience  and  efficiency  to  the  improvements  of  Pro- 
fessor Liebig  ;  it  has  superseded  all  other  processes,  and  is  now  invariably 
employed  in  inquiries  of  the  kind.  With  proper  care,  the  results  obtained 
are  wonderfully  correct;  and  equal,  if  not  surpass,  in  precision  those  of 
the  best  mineral  analysis.  The  principle  upon  which  the  whole  depends  is 
the  following :  When  an  organic  substance  is  heated  with  the  oxides  of 
copper,  lead,  and  several  other  metals,  it  undergoes  complete  combustion 
at  the  expense  of  the  oxygen  of  the  oxide,  the  metal  being  at  the  same 


ANALYSIS   OF    ORGANIC    COMPOUNDS.  449 

time  reduced  either  completely,  or  to  a  lower  state,  of  oxidation.  This 
effect  takes  place  with  the  greatest  ease  and  certainty  with  cupric  oxide 
(black  oxide  of  copper),  which,  although  unchanged  by  heat  alone,  gives 
up  oxygen  to  combustible  matter  with  extreme  facility.  When  nothing  but 
carbon  and  hydrogen,  or  those  bodies  together  with  oxygen,  are  present, 
one  experiment  suffices ;  the  carbon  and  hydrogen  are  determined  directly, 
and  the  oxygen  by  difference. 

It  is  of  course  indispensable  that  the  substance  to  be  analyzed  should 
possess  the  physical  characters  of  purity,  otherwise  the  inquiry  cannot 
lead  to  any  useful  result  ;  if  in  the  solid  state,  it  must  also  be  freed  with 
the  most  scrupulous  care  from  the  moisture  which  many  substances  retain 
with  great  obstinacy.  If  it  will  bear  the  application 
of  a  moderate  heat,  this  desiccation  is  very  easily  Fig.  176. 

accomplished  by  a  water  or  steam  bath  :  in  other 
cases,  exposure  at  common  temperatures  to  the  ab- 
sorbent powers  of  a  large  surface  of  oil  of  vitriol  in 
the  vacuum  of  an  air-pump  must  be  substituted. 

The  operation  of  weighing  the  dried  powder  is 
conducted  in  a  narrow  open  tube,  about  2£  or  3  inches 
long ;  the  tube  and  substance  are  weighed  together, 
and,  when  the  latter  has  been  removed,  the  tube  with 
any  little  adherent  matter  is  re-weighed.  This 
weight,  subtracted  from  the  former,  gives  the  weight 
of  the  substance  employed  in  the  experiment.  As 
only  half  a  gram  (5  or  6  grains)  is  used,  the  weighings  should  not  involve  a 
greater  error  than  a  milligram  (or  ^^  part  of  a  grain). 

The  copper  oxide  is  best  made  from  the  nitrate  by  complete  ignition  in 
an  earthen  crucible ;  it  is  reduced  to  powder  and  re-heated  just  before  use, 
to  expel  hygroscopic  moisture,  which  it  absorbs,  even  while  warm,  with 
avidity.  The  combustion  is  performed  in  a  tube  of  hard  white  Bohemian 
glass,  having  a  diameter  of  0-4  or  0-5  inch,  and  in  length  varying  from  14 
to  18  inches:  this  kind  of  glass  bears  a  moderate  red  heat  without  becom- 
ing soft  enough  to  lose  its  shape.  One  end  of  the  tube  is  drawn  out  to  a 

Fig.  177. 
Copper  oxide.  Mixture.  Copper  oxide. 


point,  as  shown  in  fig.  177,  and  closed;  the  other  is  simply  heated  to  fuse 
and  soften  the  sharp  edges  of  the  glass.  The  tube  is  now  two-thirds  filled 
with  the  yet  warm  copper  oxide,  nearly  the  whole  of  which  is  transferred  to 
a  small  porcelain  or  Wedgwood  mortar,  and  very  intimately  mixed  with  the 
organic  substance.  The  mixture  is  next  transferred  to  the  tube,  and  the 
mortar  rinsed  with  a  little  fresh  and  hot  oxide,  which  is  added  to  the  rest; 
the  tube  is,  lastly,  filled  to  within  an  inch  of  the  open  end  with  oxide  from 
the  crucible.  A  few  gentle  taps  on  the  table  suffice  to  shake  together  the 
contents,  so  as  to  leave  a  free  passage  for  the  evolved  gases  from  end  to 
end.  The  arrangement  of  the  mixture  and  oxide  in  the  tube  is  represented 
in  fig.  177. 

The  tube  is  then  ready  to  be  placed  in  the  furnace  or  chauffer:  this  is 
constructed  of  thin  sheet  iron,  and  is  furnished  with  a  series  of  supports 
of  equal  height,  which  serve  to  prevent  flexure  in  the  combustion-tube  when 
softened  by  heat.  The  chauffer  is  placed  upon  flat,  bricks  or  a  piece  of 
stone,  so  that  but  little  air  can  enter  the  grating,  unless  the  whole  be  pur- 

38* 


450 


THE    ELEMENTARY    OR    ULTIMATE 


posely  raised.  A  slight  inclination  is  also  given  towards  the  extremity 
occupied  by  the  mouth  of  the  combustion-tube,  which  passes  through  a 
hole  provided  for  that  purpose. 

Fig.  178. 


To  collect  the  water  produced  in  the  experiment,  a  small  light  tube  of  the 
form  represented  in  fig.  179,  filled  with  fragments  of  spongy  calcium 
chloride,  is  attached  by  a  perforated  cork,  thoroughly  dried,  to  the  open 
extremity  of  the  combustion-tube.  The  carbon  dioxide  is  absorbed  by  a 
solution  of  caustic  potash,  of  specific  gravity  1-27,  which  is  contained  in  a 
small  glass  apparatus  on  the  principle  of  a  Woulfe's  bottle,  shown  in  fig. 
180.  The  connection  between  the  latter  and  the  calcium-chloride  tube  is 

Fig.  180. 


Fig.  179. 


completed  by  a  little  tube  of  caoutchouc,  secured  with  silk  cord.  The 
whole  is  shown  in  fig.  181,  as  arranged  for  use.  Both  the  calcium-chloride 
tube  and  the  potash  apparatus  are  weighed  with  the  utmost  care  before  the 
experiment. 

Fig.  181. 


Drawing  of  the  whole  arrangement. 

The  tightness  of  the  junctions  may  be  ascertained  by  slightly  rarefying 
the  included  air  by  sucking  a  few  bubbles  from  the  interior  through  the 
liquid,  using  the  dry  lips,  or,  better,  a  little  bent  tube  with  a  perforated 
cork:  if  the  difference  of  level  in  the  liquid  in  the  two  limbs  of  the  potash- 
apparatus  be  preserved  for  several  minutes,  the  joints  are  perfect,  Red- 
hot  charcoal  is  now  placed  around  the  anterior  portion  of  the  combustion- 
tube,  containing  the  pure  oxide  of  copper ;  and  when  this  is  red-hot,  the 


ANALYSIS    OF    ORGANIC    COMPOUNDS. 


451 


fire  is  slowly  extended  towards  the  farther  extremity  by  shifting  the  mov- 
able screen  represented  in  the  drawing.  The  experiment  must  be  so  con- 
ducted that  a  uniform  stream  of  carbon  dioxide  shall  enter  the  potash 
apparatus  by  bubbles  which  may  be  easily  counted :  when  no  nitrogen  is 
present,  these  bubbles  are,  towards  the  termination  of  the  experiment,  almost 
completely  absorbed  by  the  alkaline  liquid,  the  little  residue  of  air  alone 
escaping.  In  the  case  of  an  azotized  body,  on  the  contrary,  bubbles  of 
nitrogen  gas  pass  through  the  potash-solution  during  the  whole  process. 

When  the  tube  has  become  completely  heated  from  end  to  end,  and  no 
more  gas  is  disengaged,  but,  on  the  other  hand,  absorption  begins  be  evi- 

Fig.  182. 


dent,  the  coals  are  removed  from  the  farther  extremity  of  the  combustion- 
tube,  and  the  point  of  the  latter  broken  off.  A  little  air  is  drawn  through 
the  whole  apparatus,  by  which  the  remaining  carbon  dioxide  and  watery 
vapor  are  secured.  The  parts  are,  lastly,  detached,  and  the  calcium-chlor- 
ide tube  and  potash-apparatus  re-weighed. 

Fig.  183.  Fig.  184. 


The  mode  of  heating  the  combustion-tube  with  red-hot  charcoal  is  the 
original  process,  and  still  extensively  employed,  the  construction  of  the  fur- 
nace being  most  simple,  and  charcoal  everywhere  accessible.  But  since 
the  use  of  coal-gas  has  been  universally  adopted  in  laboratories,  many  con- 
trivances have  been  suggested,  by  means  of  which  this  convenient  fuel  may 
be  employed  also  in  organic  analysis.  An  apparatus  of  this  kind*  is  the 
one  represented  in  fig.  182,  in  which  the  combust  ion-tube  is  heated  by  a 
series  of  perforated  clay-burners.  These  clay-burners  are  fixed  on  pipes 
provided  with  stopcocks,  so  that  the  gas  may  be  lighted  according  to  the 
requirements  of  the  case.  The  stopcocks  being  appropriately  adjusted,  the 

*  Hofmann,  Journal  of  Chemical  Society,  vol.  xi.  p.  30. 


452  THE    ELEMENTARY    OR    ULTIMATE 

gas  burns  on  the  surface  of  the  burners  with  a  smokeless  blue  flame,  which 
renders  them  in  a  short  time  incandescent.  The  construction  of  this  fur- 
nace is  readily  intelligible  by  a  glance  at  figures  183  and  184,  which  exhibit 
the  different  parts  of  the  apparatus  in  section,  fig.  183  representing  a  large 
furnace  with  five  rows,  and  fig.  184  a  smaller  furnace  with  three  rows  of 
clay-burners. 

The  following  account  of  a  real  experiment  will  serve  to  illustrate  the 
calculation  of  the  results  obtained  in  the  combustion  of  crystallized  sugar : 

Quantity  of  sugar  employed         ....  4-750  grains. 

Potash  apparatus  weighed  after  experiment  .     781-13 

"  «         before  experiment      .         773-82 


Carbonic  dioxide     .         .         .         .         7-31 

Calcium-chloride  tube  after  experiment       .         .         226-05 
"  before  experiment        .         .     223-30 

Water          ......  2-75 

7-31  gr.  carbon  dioxide  =  1-994  gr.  carbon  :  and  2-75  gr.  water  =  0-3056 
gr.  hydrogen;  or  in  100  parts  of  sugar,* 

Carbon  .........     41-98 

Hydrogen  ........  6-43 

Oxygen,  by  difference    .         .....     51-59 

100-00 

When  the  organic  substance  cannot  be  mixed  with  the  copper  oxide  in 
the  manner  described,  the  process  must  be  slightly  modified,  to  meet  the 
particular  case.  If,  for  example,  a  volatile  liquid  is  to  be  examined,  it 
is  enclosed  in  a  little  glass  bulb  with  a  narrow  stem,  which  is  weighed  before 
and  after  the  introduction  of  the  liquid,  the  point  being  hermetically  sealed. 
The  combustion-tube  must  have,  in  this  case,  a  much  greater  length  ;  and, 
as  the  copper  oxide  cannot  be  introduced  hot,  it  must  be  ignited  and  cooled 
out  of  contact  with  the  air,  to  prevent  absorption  of  watery  vapor.  This 
is  most  conveniently  effected  by  transferring  it,  in  a  heated  state,  to  a  large 
platinum  crucible  to  which  a  closely  fitting  cover  can  be  adapted.  When 
quite  cold,  the  cover  is  removed  and  instantly  replaced  by  a  dry  glass  funnel, 
by  the  assistance  of  which  the  oxide  may  be  directly  poured  into  the  com- 
-,.  ,85  bustion-tube  with  merely  momentary  exposure  to 

the  air.  A  little  oxide  is  put  in,  then  the  bulb, 
with  its  stem  broken  at  a,  a  file-scratch  having  been 
previously  made  ;  and,  lastly,  the  tube  is  filled  with 
the  cold  and  dry  copper  oxide.  It  is  arranged  in 
the  chauffer,  the  calcium-chloride  tube  and  potash 
apparatus  adjusted,  and  then,  some  six  or  eight 
inches  of  oxide  having  been  heated  to  redness,  the 
liquid  in  the  bulb  is,  by  the  approximation  of  a  hot 
coal,  expelled,  and  slowly  converted  into  vapor, 
which,  in  passing  over  the  hot  oxide,  is  completely 
burned.  The  experiment  is  then  terminated  in  the 
ueual  manner.  Fusible  fatty  substances,  and  vola- 
tile concrete  bodies,  as  camphor,  require  rather  different  management, 
which  need  not  be  here  described. 


The  theoretical  composition  of  sugar,  CjoHogOn,  reckoned  to  100  parts,  gives— 
Carbon        ......    42-11 

Hydrogen         .....  6-43 

Oxygen       .        .        .        .        .        .    5146 

100-00 


ANALYSIS    OF    ORGANIC    COMPOUNDS. 


453 


Copper  oxide  which  has  been  used,  may  be  easily  restored  by  moistening 
with  nitric  acid,  and  igriitmg  to  redness;  it  becomes,  in  fact,  rather  im- 
proved than  otherwise,  as,  after  frequent  employment,  its  density  is  increased 
and  its  troublesome  hygroscopic  powers  diminished.  For  substances  which 
are  very  difficult  of  combustion,  from  the  large  proportion  of  carbon  they 
contain,  and  for  compounds  into  which  chlorine  enters  as  a  constituent, 
fused  and  powdered  lead  chromate  is  very  advantageously  substituted  for 
the  copper  oxide.  Lead  chromate  freely  gives  up  oxygen  to  combustible 
matters,  and  even  evolves,  when  strongly  heated,  a  little  of  that  gas,  which 
thus  ensures  the  perfect  combustion  of  the  organic  body. 

Analysis  of  Azolized  Substances.  — The  presence  of  nitrogen  in  an  organic 
compound  is  easily  ascertained  by  heating  a  small  portion  with  solid  potas- 
sium hydrate  in  a  test-tube  :  the  nitrogen,  if  present,  is  converted  into 
ammonia,  which  may  be  recognized  by  its  odor  and  alkaline  reaction. 
There  are  several  methods  of  determining  the  proportion  of  nitrogen  in 
azotized  organic  substances,  the  experimenter  being  guided  in  his  choice 
of  means  by  the  nature  of  the  substance  and  its  comparative  richness  in 
that  element.  The  carbon  and  hydrogen  are  first  determined  in  the  usual 
manner,  a  longer  tube  than  usual  being  employed,  and  four  or  five  inches 
of  its  anterior  portion  filled  with  copper  turnings,  rendered  perfectly  me- 
tallic by  ignition  in  hydrogen :  this  serves  to  decompose  any  nitrogen  oxide 
that  may  be  formed  in  the  act  of  combustion.  During  the  experiment, 
some  idea  of  the  abundance  or  paucity  of  the  nitrogen  may  be  formed, 
from  the  number  of  bubbles  of  incondensable  gas  which  traverses  the  solu- 
tion of  potash. 

In  the  case  of  compounds  abounding  in  nitrogen,  and  readily  burned  by 

Fig.  186. 


copper  oxide,  a  method  may  be  employed,  which  is  very  easy  of  execution :  thia 
consists  in  determining  the  ratio  borne  by  the  liberated  nitrogen  to  „. 
the  carbon  dioxide  produced  in  the  combustion.  A  tube  of  hard  glass, 
of  the  usual  diameter,  and  about  15  inches  long,  is  sealed  at  one  end  ; 
a  little  of  the  organic  substance,  mixed  with  copper  oxide,  is  intro- 
duced, and  allowed  to  occupy  about  two  inches  of  the  tube;  about 
as  much  pure  oxide  is  placed  over  it,  and  then  another  portion  of 
a  similar  mixture ;  after  which  the  tube  is  filled  up  with  a  second 
and  larger  portion  of  pure  oxide,  and  a  quantity  of  spongy  me- 
tallic copper.  A  short  bent  tube,  made  movable  by  a  caoutchouc 
joint,  is  fitted  by  a  perforated  cork,  and  made  to  dip  into  a  mer- 
curial trough,  while  the  combustion-tube  itself  rests  in  the  chauf- 
fer (fig.  18(>). 

Fire  is  first  applied  to  the  anterior  part  of  the  tube  containing 
the  metal  and  unmixed  oxide,  and,  when  this  is  red-hot,  to  the 
extreme  end.  Combustion  of  the  first  portion  of  the  mixture  takes 
place,  the  gaseous  products  sweeping  before  them  nearly  the 


454:  THE    ELEMENTARY    OR    ULTIMATE 

whole  of  the  air  of  the  apparatus.  When  no  more  gas  issues,  the  tube 
is  slowly  heated  by  half  an  inch  at  a  time,  in  the  usual  manner,  and  all 
the  gas  very  carefully  collected  in  a  graduated  jar,  until  the  operation 
is  at  an  end.  The  volume  is  then  read  off,  and  some  strong  solution  of 
caustic  potash  thrown  up  into  the  jar  by  &  pipette  with  a  curved  extremity. 
When  the  absorption  is  complete,  the  residual  volume  of  nitrogen  is  ob- 
served, and  compared  with  that  of  the  mixed  gases,  proper  correction 
being  made  for  differences  of  level  in  the  mercury ;  and  from  these  data 
the  exact  proportion  borne  by  the  nitrogen  to  the  carbon  can  be  at  once 
determined.* 

If  the  proportion  of  nitrogen  be  but  small,  the  error  from  the  nitrogen  of 
the  residual  atmospheric  air  becomes  so  great  as  to  destroy  all  confidence 
in  the  result  of  the  experiment;  and  the  same  thing  happens  when  the  sub- 
stance is  incompletely  burned  by  copper  oxide:  other  means  must  then  be 
employed. 

The  absolute  method  of  determination,  also  known  by  the  name  of  Dumas' 
method,  may  be  had  recourse  to  when  the  foregoing,  or  comparative  method, 
fails  from  the  first  cause  mentioned :  it  gives  excellent  results,  and  is  ap- 
plicable to  all  azotized  substances. 

A  tube  of  good  Bohemian  glass,  28  inches  long,  is  securely  sealed  at  one 
end ;  into  this  enough  dry  acid  sodium  carbonate  is  put  to  occupy  6  inches. 
A  little  pure  copper  oxide  is  next  introduced,  and  afterwards  the  mixture 
of  oxide  and  organic  substance,  the  weight  of  the  latter,  between  4-5  and  9 
grains,  in  a  dry  state,  having  been  correctly  determined.  The  remainder 
of  the  tube,  amounting  to  nearly  one-half  of  its  length,  is  then  filled  up 
with  pure  copper  oxide  and  spongy  metal,  and  a  round  cork,  perforated  by 

Fig.  188. 


a  piece  of  narrow  tube,  is  securely  adapted  to  its  mouth.  This  tube  is 
connected  by  means  of  a  caoutchouc  joint  with  a  bent  delivery-tube,  a,  and 
the  combustion-tube  is  arranged  in  the  furnace.  A  few  coals  are  now  ap- 


*  A  molecule  of  carbon  dioxide  (C02)  containing  1  atom  of  carbon  [=  12],  occupies  the 
same  space  as  a  molecule  (or  double  atom)  of  nitrogen  (NN)  [2  .  14  =:  28].  If,  therefore,  the 
volumes  of  carbon  dioxide  and  nitrogen  in  the  gaseous  mixture  are  as  m  :  1,  it  follows  that  the 
number  of  carbon-atoms  in  the  compound  is  to  the  number  of  nitrogen-atoms  as  m  :  2 ;  and 
consequently  that  the  weight  of  the  carbon  in  the  compound  is  to  that  of  the  nitrogen  as  m 
X  12  :  2  X  14,  or  3  m  :  7,  so  that  if  the  percentage  of  carbon  (c)  has  been  previously  found, 
the  percentage  of  nitrogen  (n)  will  be  given  by  the  equation  : 

7 

n  ~ c. 

3m 

For  example,  caffeine,  which  contains  47-48  per  cent,  of  carbon,  is  found,  by  the  process  just 
described,  to  yield  carbon  dioxide  and  nitrogen  in  the  proportion  by  volume  of  4  :  1 ;  the  per- 
centage of  nitrogen  in  caffeine  is  therefore  X  49-48  =  28-89. 


ANALYSIS    OF    ORGANIC    COMPOUNDS.  455 

plied  to  the  farther  end  of  the  tube,  so  as  to  decompose  a  portion  of  the 
acid  sodium  carbonate,  the  remainder  of  the  carbonate,  as  well  as  of  the  other 
part  of  the  tube,  being  protected  from  the  beat  by  a  screen  n.  The  current 
of  carbon  dioxide  thus  produced  is  intended  to  expel  all  the  air  from  the 
apparatus.  In  -order  to  ascertain  that  this  object,  on  which  the  success  of 
the  whole  operation  depends,  is  accomplished,  the  delivery-tube  is  depressed 
under  the  level  of  a  mercurial  trough,  and  the  gas,  which  is  evolved,  col- 
lected in  a  test-tube  filled  with  concentrated  potash-solution.  If  the  gas 
be  perfectly  absorbed,  or  if,  after  the  introduction  of  a  considerable 
quantity,  only  a  minute  bubble  be  left,  the  air  may  be  considered  as  ex- 
pelled. The  next  step  is  to  fill  a  graduated  glass  jar  two-thirds  with  mer- 
cury and  one-third  with  a  strong  solution  of  potash,  and  to  invert  it  over 
the  delivery-tube,  as  represented  in  fig.  188. 

This  done,  fire  is  applied  to  the  tube,  commencing  at  the  front  end,  and 
gradually  proceeding  to  the  closed  extremity,  which  still  contains  some  un- 
decomposed  acid  sodium  carbonate.  This,  when  the  fire  at  length  reaches 
it,  yields  up  carbon  dioxide,  which  chases  forward  the  nitrogen  lingering 
in  the  tube.  The  carbon  dioxide  generated  during  the  combustion  is  wholly 
absorbed  by  the  potash  in  the  jar,  and  nothing  is  left  but  the  nitrogen. 
When  the  operation  is  at  an  end,  the  jar,  with  its  contents,  is  transferred 
to  a  vessel  of  water,  and  the  volume  of  the  nitrogen  read  off.  This  is  pro- 
perly corrected  for  temperature,  pressure,  and  aqueous  vapor,  and  its 
weight  determined  by  calculation.  When  the  operation  has  been  very  suc- 
cessful, and  all  precautions  minutely  observed,  the  result  still  leaves  an 
error  in  excess,  amounting  to  0-3  or  05  per  cent.,  due  to  the  residual  air 
of  the  apparatus,  or  that  condensed  in  the  pores  of  the  copper  oxide. 

A  most  elegant  process  for  estimating  nitrogen  in  all  organic  compounds, 
except  those  containing  the  nitrogen  in  the  form  of  nitrous  acid  or  nitrogen 
tetroxide,  and  in  some  organic  bases,  has  been  put  in  practice  by  Will  and 
Varrentrapp.  When  a  non-azotized  organic  substance  is  heated  to  redness 
with  a  large  excess  of  potassium  or  sodium  hydrate,  it  suffers  complete 
and  speedy  combustion  at  the  expense  of  the  water  of  the  hydrate,  the 
oxygen  combining  with  the  carbon  of  the  organic  matter  to  form  carbon 
dioxide,  which  is  retained  by  the  alkali,  while  its  hydrogen,  together  with 
that  of  the  substance,  is  disengaged,  sometimes  in  union  with  a  little  carbon. 
The  same  change  happens  when  nitrogen  is  present,  but  with  this  addition : 
the  whole  of  the  nitrogen  thus  abandoned  combines  with  a  portion  of  the 
liberated  hydrogen  to  form  ammonia.  It  is  evident,  therefore,  that  if  this 
experiment  be  made  on  a  weighed  quantity  of  matter,  and  circumstances 
allow  the  collection  of  the  whole  of  the  ammonia  thus  produced,  the  pro- 
portion of  nitrogen  can  be  easily  calculated. 

An  intimate  mixture  is  made  of  1  part  caustic  soda  and  2  or  3  parts 
quicklime,  by  slaking  lime  of  good  quality  with  the  proper  proportion  of 
strong  caustic  soda,  drying  the  mixture  in  an  iron  vessel,  and  then  heating 
it  to  redness  in  an  earthen  crucible.  The  ignited  mass  is  rubbed  to  powder 
in  a  warm  mortar,  and  carefully  preserved  from  the  air.  The  lime  is  useful 
in  many  ways:  it  diminishes  the  tendency  of  the  alkali  to  deliquesce, 
facilitates  mixture  with  the  organic  substance,  and  prevents  fusion  and 
liquefaction.  A  proper  quantity  of  the  substance  to  be  analyzed,  namely, 
from  5  to  10  grains,  is  dried  and  accurately  weighed  out:  this  is  mixed  in 
a  warm  porcelain  mortar  with  enough  of  the  soda-lime  to  fill  two-thirds 
of  an  ordinary  combustion-tube,  the  mortar  being  rinsed  with  a  little  more 
of  the  alkaline  mixture,  and,  lastly,  with  a  small  quantity  of  powdered 
glass,  which  completely  removes  everything  adherent  to  its  surface;  the 
tube  is  then  filled  to  within  an  inch  of  the  open  end  with  the  lime-mixture, 
and  arranged  in  the  chauffer  in  the  usual  manner.  The  ammonia  is  col- 
lected in  a  little  apparatus  of  three  bulbs  (fig.  189),  containing  moderately 
strong  hydrochloric  acid,  attached  by  a  cork  to  the  combustion-tube. 


456  THE   ELEMENTARY    OB    ULTIMATE 

Matters  being  thus  adjusted,  fire  is  applied  to  the  tube,  commencing  with 
the  anterior  extremity.     When  it  is  ignited  throughout  its  whole  length, 

and  when  no  gas  issues  from  the  ap- 

9'  paratus,  the  point  of  the  tube  is  bro- 

ken, and  a  little  air. drawn  through 
the  whole.  The  acid  liquid  is  then 
emptied  into  a  capsule,  the  bulbs 
rinsed  into  the  same,  first  with  a 
little  alcohol,  and  then  repeatedly 
with  distilled  water ;  an  excess  of 
pure  platinic  chloride  is  added,  and 
the  whole  evaporated  to  dryness  in 
a  water-bath.  The  dry  mass,  when  cold,  is  treated  with  a  mixture  of 
alcohol  and  ether,  which  dissolves  out  the  superfluous  platinum  chloride, 
but  leaves  untouched  the  yellow  crystalline  ammonium  platinochloride. 
The  latter  is  collected  upon  a  small  weighed  filter,  washed  with  the  same 
mixture  of  alcohol  and  ether,  dried  at  100°  C.  (212°  F.),  and  weighed;  100 
parts  correspond  to  6-272  parts  of  nitrogen.  Or,  the  salt  with  its  filter 
may  be  very  carefully  ignited,  the  filter  burned  in  a  platinum  crucible,  and 
the  nitrogen  reckoned  from  the  weight  of  the  spongy  metal,  100  parts  of 
that  substance  corresponding  to  14-18  parts  of  nitrogen.  The  former  plan 
is  to  be  preferred  in  most  cases. 

Bodies  very  rich  in  nitrogen,  as  urea,  must  be  mixed  with  about  an  equal 
quantity  of  pure  sugar,  to  furnish  incondensable  gas,  and  thus  diminish 
the  violence  of  the  absorption  which  otherwise  occurs  ;  and  the  same  pre- 
caution must  be  taken,  for  a  different  reason,  with  those  which  contain 
little  or  no  hydrogen. 

A  modification  of  this  process  has  been  suggested  by  Peligot,  which  is 
very  convenient  if  a  large  number  of  nitrogen-determinations  is  to  be 
made.  By  this  plan,  the  ammonia,  instead  of  being  received  in  hydro- 
chloric acid,  is  conducted  into  a  known  volume  (10  to  20  cubic  centimetres) 
of  a  standard  solution  of  sulphuric  acid,  contained  in  the  ordinary  nitro- 
gen-bulbs. After  the  combustion  is  finished,  the  acid  containing  the  am- 
monia is  poured  out  into  a  beaker,  colored  with  a  drop  of  tincture  of 
litmus,  and  then  neutralized  with  a  standard  solution  of  soda  in  water  or 
of  lime  in  sugar-water,  the  point  of  neutralization  becoming  perceptible 
by  the  sudden  appearance  of  a  blue  tint.  The  lime-solution  is  conveniently 
poured  out  from  the  graduated  glass  tube,  described  under  the  head  of 
Alkalimetry.  The  volume  of  lime-solution  necessary  to  neutralize  the 
same  amount  of  acid  that  is  used  for  condensing  the  ammonia,  having  been 
ascertained  by  a  preliminary  experiment,  it  is  evident  that  the  difference 
of  the  quantities  used  in  the  two  experiments  gives  the  ammonia  collected 
in  the  acid  during  the  combustion.  The  amount  of  nitrogen  may  thus  be 
calculated.  If,  for  instance,  an  acid  be  prepared,  containing  20  grains  of 
pure  hydrogen  sulphate  (S04H2)  in  1000  grain-measures  —  200  grain-meas- 
ures of  this  acid  —  the  quantity  introduced  into  the  bulbs  —  correspond 
to  1-38  grains  of  ammonia,  or  1-14  grains  of  nitrogen.  The  alkaline  solu- 
tion is  so  graduated  that  1000  grain-measures  will  exactly  neutralize  the 
200  grain-measures  of  the  standard  acid.  If  we  now  find  that  the  acid, 
partly  saturated  with  the  ammonia  disengaged  during  the  combustion  of  a 
nitrogenous  substance,  requires  only  700  grain-measures  of  the  alkaline 

200   X   300 

solution,  it  is  evident  that TnnT) ==   ^   grain-measures  were   satu- 
rated by  the  ammonia,  and  the  quantity  of  nitrogen  is  obtained  by  the  pro- 

1-14  X  GO 

portion  — 200  :  1-14  ;==  60  ;  x,  wherefore  x  = r>oO =  °'342  Srains  of 

nitrogen. 


ANALYSIS    OF    ORGANIC    COMPOUNDS.  457 

Estimation  of  Sulphur  in  Organic  Compounds.  —  When  bodies  of  this  class 
containing  sulphur  are  burned  with  copper  oxide,  a  small  tube  containing 
lead  dioxide  may  be  interposed  between  the  calcium-chloride  tube  and  the 
potash  apparatus,  to  retain  any  sulphurous  acid  that  may  be  formed.  It 
is  better,  however,  to  use  lead  chromate  in  such  cases.  The  proportion  of 
sulphur  is  determined  by  oxidizing  a  known  weight  of  the  substance  with 
strong  nitric  acid,  or  by  fusion  in  a  silver  vessel  with  ten  or  twelve  times 
its  weight  of  pure  potassium  hydrate  and  half  as  much  nitre.  The  sul- 
phur is  thus  converted  into  sulphuric  acid,  the  quantity  of  which  can  be 
determined  by  dissolving  the  fused  mass  in  water,  acidulating  with  nitric 
acid,  and  adding  a  barium  salt.  Phosphorus  is?  in  like  manner,  oxidized  to 
phosphoric  acid,  the  quantity  of  which  is  determined  by  precipitation  as 
ammonio-magnesian  phosphate,  or  otherwise. 

Estimation  of  Chlorine.  —  The  case  of  a  volatile  liquid  containing  chlor- 
ine is  of  very  frequent  occurrence,  and  may  be  taken  as  an  illustration 
of  the  general  plan  of  proceeding.  The  combustion  with  copper  oxide 
must  be  very  carefully  conducted,  and  two  or  three  inches  of  the  anterior 
portion  of  the  tube  kept  cool  enough  to  prevent  volatilization  of  the  copper 
chloride  into  the  calcium-chloride  tube.  Lead  chromate  is  much  better 
for  the  purpose.  The  chlorine  is  correctly  determined  by  placing  a  small 
weighed  bulb  of  liquid  in  a  combustion-tube,  which  is  afterwards  filled  with 
fragments  of  pure  quicklime.  The  lime  is  brought  to  a  red  heat,  and  the 
vapor  of  the  liquid  driven  over  it,  when  the  chlorine  displaces  oxygen  from 
the  lime,  and  gives  rise  to  calcium  chloride.  When  cold,  the  contents  of 
the  tube  are  dissolved  in  dilute  nitric  acid,  filtered,  and  the  chlorine  pre- 
cipitated by  silver  nitrate. 

Bromine  and  iodine  are  estimated  in  a  similar  manner. 


EMPIRICAL  AND  MOLECULAR  FORMULAE. 

A  chemical  formula  is  termed  empirical  when  it  merely  gives  the  simplest 
possible  expression  of  the  composition  of  the  substance  to  which  it  refers. 
A  molecular  formula,  on  the  contrary,  expresses  the  absolute  number  of  i 
atoms  of  each  of  its  elements  supposed  to  be  contained  in  the  molecule,  as 
well  as  the  mere  relations  existing  between  them.  The  empirical  formula 
is  at  once  deduced  from  the  analysis  of  the  substance,  reckoned  to  100 
parts;  but  to  determine  the  molecular  formula,  other  considerations  must 
be  taken  into  account:  namely,  the  combining  or  saturating  power  of  the 
compound,  if  it  is  acid  or  basic;  the  number  of  atoms  of  any  one  of  its 
elements  (generally  hydrogen)  which  may  be  replaced  by  other  elements; 
the  law  of  even  numbers,  which  requires  that  the  sum  of  the  numbers  of 
atoms  of  all  the  perissad  elements  (hydrogen,  nitrogen,  chlorine,  &c.)  con- 
tained in  the  compound  shall  be  divisible  by  2;  and  the  vapor-density  of 
the  compound  (if  it  be  volatile  without  decomposition)  which,  in  normally 
constituted  compounds,  is  always  half  the  molecular  weight  (p.  229). 

The  molecular  formula  may  either  coincide  with  the  empirical  formula, 
or  it  may  be  a  multiple  of  the  latter.  Thus,  the  composition  of  acetic  acid 
is  expressed  by  the  formula  CH20,  which  exhibits  the  simplest  relations  of 
the  three  elements;  but  if  we  want  to  express  the  quantities  of  these,  in 
atoms,  required  to  make  up  a  molecule  of  acetic  acid,  we  have  to  adopt  the 
formula  C2H402:  for  only  one-fourth  of  the  hydrogen  in  this  acid  is  re- 
placeable by  metals  to  form  salts,  C2H3K02,  for  example;  and  its  vapor- 
density,  compared  with  hydrogen,  is  nearly  30,  which  is  half  the  weight  of 
the  molecule,  C2H402  =  2.12-j-4.1-f-2.16.  Again,  the  empirical  formula 
of  benzene  is  CH;  but  this  contains  an  uneven  number  of  hydrogen  atoms; 
39 


458  EMPIRICAL    AND    MOLECULAR    FORMULAE. 

and,  moreover,  if  it  expressed  the  weight  of  the  molecule  of  benzene,  the 

12-1-1 

vapor-density  of  that  compound  should  be  — — — -  =  6-5,  whereas  experi- 
ment shows  that  it  is  six  times  as  great,  or  equal  to  39:  hence  the  molecular 
formula  of  benzene  is  C6H6. 

The  deduction  of  an  empirical  formula  from  the  ultimate  analysis  is  very 
easy ;  the  case  of  sugar,  already  cited,  may  be  taken  as  an  example.  This 
substance  contains,  according  to  the  analysis,  in  100  parts  — 

Carbon 41-98 

Hydrogen         ......       6-43 

Oxygen 51-59 

100-00 

If  each  of  these  quantities  be  divided  by  the  atomic  weight  of  the  corre- 
sponding element,  the  quotients  will  express  the  relations  existing  between 
the  numbers  of  atoms  of  the  three  elements:  these  are  afterwards  reduced  to 
their  simplest  expression.  This  is  the  only  part  of  the  calculation  attended 
with  any  difficulty.  If  the  numbers  were  rigidly  correct,  it  would  only  be 
necessary  to  divide  each  by  the  greatest  divisor  common  to  the  whole;  as 
they  are,  however,  only  approximative,  something  is  of  necessity  left  to  the 
judgment  of  the  experimenter. 
In  the  case  of  sugar,  we  have 

41-98  6-43  51-59 


=  3-50 ;        —-  =  6-43 ;        —  -  =  3-22, 


12  1  16 

or  350  atoms  carbon,  643  atoms  hydrogen,  and  322  atoms  oxygen.  Now  it 
is  evident,  in  the  first  place,  that  the  hydrogen  and  oxygen  are  present  in 
the  proportions  to  form  water,  or  twice  as  many  atoms  of  the  former  as  of 
the  latter.  Again,  the  atoms  of  carbon  and  hydrogen  are  nearly  in  the 
proportion  of  12  :  22,  so  that  the  formula  C,2H22On  appears  likely  to  be 
correct.  It  is  now  easy  to  see  how  far  this  is  admissible,  by  reckoning  it 
back  to  100  parts,  comparing  the  result  w'th  the  numbers  given  by  the 
actual  analysis,  and  observing  whether  the  difference  falls  fairly,  in  direction 
and  amount,  within  the  limits  of  error  of  what  may  be  termed  a  good  ex- 
periment, viz.,  two  or  three-tenths  per  cent,  deficiency  in  the  carbon,  and 
not  more  than  one-tenth  or  two-tenths  per  cent,  excess  in  the  hydrogen : 

Carbon  .  .  .  .  12  X  12  =  144 
Hydrogen  .  .  .  .  1  x  22  =  22 
Oxygen  .  .  .  .  16  x  H  =  176 

342 

342  :  144  =  100  :  42-11 
342  :  222  =  100  :  6-43 
342  :  176  =  100  :  51  46 

Organic  acids  and  salt-radicals  have  their  molecular  weights  most  fre- 
quently determined  by  an  analysis  of  their  lead  and  silver  salts,  by  burning 
these  latter  with  suitable  precautions  in  a  thin  porcelain  capsule,  and  noting 
the  weight  of  the  lead  oxide  or  metallic  silver  left  behind.  If  the  lead  oxide 
be  mixed  with  globules  of  reduced  metal,  the  quantity  of  the  latter  must  be 
ascertained  by  dissolving  away  the  oxide  with  acetic  acid.  Or  the  lead  salt 
may  be  converted  into  sulphate,  and  the  silver  compound  into  chloride,  and 
both  metals  thus  estimated.  An  organic  base,  pn  the  contrary,  has  its 


DETERMINATION  OF  THE  DENSITY  OF  VAPORS.      459 

molecular  weight  fixed  by  the  observation  of  the  quantity  of  a  mineral 
acid,  or  an  inorganic  salt-radical,  required  to  form  with  it  a  combination 
having  the  characters  of  neutrality. 

The  rational  and  constitutional  formulae  of  organic  compounds  will  be 
considered  further  on. 


Fig.  190. 


DETERMINATION  OF  THE  DENSITY  OF  VAPORS. 

The  determination  of  the  specific  gravity  of  the  vapor  of  a  volatile  sub- 
stance is  frequently  a  point  of  great  importance,  inasmuch  as  it  gives  the 
means,  in  conjunctioii  with  the  analysis,  of  representing 
the  constitution  of  the  substance  by  measure  in  a  gaseous 
state.  The  following  is  a  sketch  of  the  plan  of  operation 
usually  followed  :  —  Alight  glass  globe  about  three  inches 
in  diameter  is  taken,  and  its  neck  softened  and  drawn  out 
in  the  blowpipe-flame,  as  represented  in  fig.  190:  this  is 
accurately  weighed.  About  one  hundred  grains  of  the 
volatile  liquid  are  then  introduced,  by  gently  warming  the 
globe  and  dipping  the  point  into  the  liquid,  which  is  then 
forced  upwards  by  the  pressure  of  the  air  as  the  vessel 
cools.  The  globe  is  next  firmly  attached  by  wire  to  a  han- 
dle, in  such  a  manner  that  it  may  be  plunged  into  a  bath 
of  boiling  water  or  heated  oil,  and  steadily  held  with  the 
point  projecting  upwards.  The  bath  must  have  a  temper- 
ature considerably  above  that  of  the  boiling  point  of  the 
liquid.  The  latter  becomes  rapidly  converted  into  vapor, 
which  escapes  by  the  narrow  orifice,  chasing  before  it  the 
air  of  the  globe.  When  the  issue  of  vapor  has  wholly 
ceased,  and  the  temperature  of  the  bath,  carefully  observed,  appears  pretty 
uniform,  the  open  extremity  of  the  point  is  hermetically  sealed  by  a  small 
blowpipe-flame.  The  globe  is  removed  from  the  bath,  suffered  to  cool, 
cleansed  if  necessary,  and  weighed,  after  which  the  neck  is  broken  off  be- 
neath the  surface  of  water  which  has  been  boiled  and  cooled  out  of  contact 
of  air,  or  (better)  of  mercury.  The  liquid  enters  the  globe,  and,  if  the 
expulsion  of  the  air  by  the  vapor  has  been  complete,  fills  it;  if  otherwise, 
an  air-bubble  is  left  whose  volume  can  be  easily  ascertained  by  pouring  the 
liquid  from  the  globe  into  a  graduated  jar,  and  then  refilling  the  globe,  and 
repeating  the  same  observation.  The  capacity  of  the  vessel  is  thus  at  the 
same  time  known :  and  these  ar«  all  the  data  required.*  An  example  will 
render  the  whole  intelligible. 


Determination  of  the  Vapor- Density  of  Acetone. 


Capacity  of  globe     ....... 

Weight  of  globe  filled  with  dry  air  at  52°  F.  and 
30-24  inches  barometer  . 

Weight  of  globe  filled  with  vapor  at  212°  F.  temp,  of 
the  bath  at  the  moment  of  sealing  the  point,  and 
30*24  inches  barometer  ..... 

Residual  air,  at  45°  F.,  and  30-24  inches  barometer 


31-61  cubic  inches. 


2070-88  grains. 


2070-81  grains. 

0-60  cubic  inches. 


*  Messrs.  Playfair  and  "\Vanklyn  have  lately  described  an  important  modification  of  this 
process,  whereby  (he  densities  of  a  vapor  at  temperatures  below  the  boiling  point  of  the  liquid 
may  be.  determined.  This  object  is  attained  by  mixing  the  vapor  of  the  body  with  a  meas- 
ured volume  of  a  permanent  gas  —  hydrogen,  for  instance.  —  Journ.  of  the  C/iein.  Sue.,  vol.  xv. 
p.  143. 


460      DETERMINATION  OF  THE  DENSITY  OF  VAPORS. 

31-61  cubic  inches  of  air  at  52°  and  30-24  in.  bar. —  32 -36  cubic  inches  at 
60°  F.,  and  30  inch  bar.,  weighing-    .         .         .         .         10-035  grains. 
Hence,  weight  of  empty  globe,  2070-88  —  10-035  =  2060-845  grains. 


0-6  cubic  inch  of  air  at  45°  —  0-8  cubic  inch  at  212° ;  weight  of  do.  by  cal- 
culation— 0-1 91  grain. 

31-61  —0-8  =  30-81  cubic  inches  of  vapor  at  212°  and  30-24  in.  bar.,  which, 
on  the  supposition  that  it  would  bear  cooling  to  60°  without  liquefaction,  would, 
at  that  temperature,  and  under  a  pressure  of  30  inch,  bar.,  become  re- 
duced to  24-18  cubic  inches. 

Hence, 

Weight,  of  globe  and  vapor 2076-810  grains. 

"  residual  air 0-191 

2076-619 
Weight  of  globe 2060-845 

Weight  of  the  24-18  cubic  inches  of  vapor  .  .  .  15-774 
Consequently,  100  cubic  inches  of  such  vapor  must  weigh  65-23 
100  cubic  inches  of  air,  under  similar  circumstances,  weigh  31  -01 
65-23 

=•  2-103,  the  specific  gravity  of  the  vapor  in  question,  air  being  unity. 

31-01 

Or,  the  weight  of  100  cubic  inches  of  hydrogen  being  2-14  grains, 
65-23 

=  30-44  is  the  specific  gravity  of  acetone  vapor  referred  to  hydrogen 

2-14 

as  unity. 

In  the  foregoing  statement,  we  have,  for  the  sake  of  simplicity,  omitted 
a  correction,  which,  in  very  exact  experiments,  must  not  be  lost  sight  of, 
viz.,  the  expansion  and  change  of  capacity  of  the  glass  globe  by  the  ele- 
vated temperature  of  the  bath.  The  density  so  obtained  will  be  always  on 
this  account  a  little  too  high. 

The  error  of  the  mercurial  thermometer  at  high  temperatures  is  in  the 
opposite  direction. 

The  preceding  method,  which  is  that  of  Dumas,  is  applicable  to  the  de- 
termination of  the  vapor-densities  of  all  substances  whose  boiling  points  are 
within  the  range  of  the  mercurial  thermometer,  that  is  to  say,  not  exceed- 
ing 300°  C.  (572°  F.),  and  therefore  to  nearly  all  volatile  organic  compounds: 
indeed,  there  are  but  few  such  compounds  which  can  bear  higher  tempera- 
tures without  decomposition.  But  for  mineral  substances,  such  as  sulphur, 
iodine,  volatile  metallic  chlorides,  &c.,  it  is  often  necessary  to  employ  much 
higher  temperatures;  and  for  such  cases  a  modification  of  the  process  has 
been  devised  by  Deville  and  Troost.  It  consists  in  using  a  globe  of  porce- 
lain instead  of  glass,  heating  it  in  the  vapor  of  a  substance  whose  boiling 
point  is  known  and  constant,  and  sealing  the  globe  by  the  flame  of  the  oxy- 
hydrogen  blowpipe.  The  vapors  employed  for  this  purpose  are  those  of 
mercury,  which  boils  at  350°  C.  (662°  F.) ;  of  sulphur,  which  boils  at  440°  C. 
(824°  F. ) ;  of  cadmium,  boiling  at  860°  C.  (1580°  F. ) ;  of  zinc,  boiling  at  1040° 
C.  (1900°  F.).  The  use  of  these  liquids  of  constant  boiling  point  obviates 
the  necessity  of  determining  the  temperature  in  each  experiment,  which  at 
such  degrees  of  heat  would  be  very  difficult. 

In  the  processes  above  described,  the  density  of  a  vapor  is  determined 
"by  weighing  the  quantity  of  the  vapor  contained  in  a  vessel  of  known  ca- 


DETERMINATION  OF  THE  DENSITY  OF  VAPORS.       461 

pacity.  Another  method,  devised  by  Gay-Lussac,  consists  in  ascertaining 
the  volume  occupied  by  a  given  weight  of  substance  when  heated  up  to  a 
temperature  considerably  above  its  boiling  point. 

The  density  of  a  vapor  referred  to  air  as  unity  may  be  converted  into 
that  which  it  has  compared  with  hydrogen,  by  dividing  by  0*06926,  the 
specific  gravity  of  hydrogen  referred  to  air  as  unity. 

The  vapor-density  of  a  compound  thus  determined,  that  is  to  say,  the 
weight  of  a  unit-volume  of  its  vapor  compared  with  that  of  hydrogen,  is 
found  to  be  in  nearly  all  cases  half  its  molecular  weight;  for  example,  the 
molecular  weight  of  acetone,  C3H60,  is  36  -f-  6  -f  16  =  58,  the  half  of 
which  is  29,  or  nearly  equal  to  the  vapor-density  of  acetone  determined  by 
experiment.  Hence  the  law  already  stated  (p.  229),  that  the  molecules  of 
all  normally  constituted  compounds  in  the  state  of  vapor  occupy  twice  the 
volume  of  an  atom  of  hydrogen. 

Some  compounds,  however,  exhibit  a  departure  from  this  rule,  their  ob- 
sei'ved  specific  gravities  being  equal  to  only  one-fourth  their  molecular 
weights,  or  their  molecules  occupying  four  times  the  volume  of  an  atom  of 
hydrogen.  Such  is  the  case  with  sal-ammoniac,  NH4C1,  phosphorus  penta- 
chloride,  PC15,  sulphuric  acid,  S04H2,  ammonium-sulph-hydrate,  SH(NH4), 
and  a  few  others.  This  anomaly  is  probably  due,  in  some  cases  at  least,  to 
a  decomposition  or  "dissociation"  of  the  compound  at  the  high  tempera- 
ture to  which  it  is  subjected  for  the  determination  of  its  vapor-density ; 
KH4C1,  for  example,  splitting  up  into  NH3  and  HC1,  each  of  which  occupies 
two  volumes,  and  the  whole  therefore  four  volumes ;  and  in  like  manner 
S04H2  may  be  supposed  to  separate  into  S03  and  OH2;  PC15  into  PC13  and 
C12;  SH(NH4)  into  SH2  and  NH3,  &c. 

On  the  other  hand,  some  substances,  both  simple  and  compound,  exhibit, 
at  temperatures  not  far  above  their  boiling  points,  vapor-densities  consider- 
ably greater  than  they  should  have  according  to  the  general  law,  whereas 
when  raised  to  higher  tempei'atures  they  exhibit,  normal  vapor-densities. 
Thus  sulphur,  which  boils  at  440°  C.  (824°  F.),  exhibits  at  1000°  C.  (1832° 
F.),  like  elementary  gases  in  general,  a  vapor-density  equal  to  its  atomic 
weight,  viz.,  32  (see  p.  229) ;  but  at  500°  C.  (932°  F.)  its  vapor-density  is 
nearly  three  times  as  great.  Again,  acetic  acid,  C2H402,  whose  molecular 
weight  is  24  -j-  4  -f-  16  =  60,  has,  at  temperatures  considernbly  above  its 
boiling  point,  a  vapor-density  nearly  equal  to  30;  but  at  125°  C.  (257°  F.), 
8°  C.  (14°  F.)  above  its  boiling  point,  its  vapor-density  is  rather  more  than 
45,  or  1  j  times  as  great.  This  anomalous  increase  of  vapor-density  appears 
t'o  take  place  when  the  substance  approaches  its  liquefying  point,  at  which 
also  it  exhibits  irregularities  in  its  rate  of  expansion  and  contraction  by  varia- 
tions of  pressure  and  temperature  —  at  which,  in  short,  it  begins  to  behave 
itself  like  a  liquid ;  but  at  higher  temperatures  it  exhibits  the  physical 
characters  of  a  perfect  gas,  and  then  also  its  specific  gravity  becomes  normal. 

There  are  two  elements,  however,  namely,  phosphorus  and  arsenic,  which, 
at  all  temperatures  hitherto  attained,  exhibit  a  vapor-density  twice  as  great 
as  they  should  have  according  to  the  general  law,  that  of  phosphorus  being 
always  62,  and  that  of  arsenic  150.  This  has  been  explained  by  supposing 
that^the  molecule  of  each  of  these  elements  in  the  free  state  contains  4  atoms 
instead  of  two,  as  is  the  case  with  most  elementary  bodies ;  thus  the  mole- 
cule of  phosphorus  is  supposed  to  be  represented  by  the  formula 


LJ. 


39* 


462  DECOMPOSITIONS  AND  TRANSFORMATIONS 


DECOMPOSITIONS  AND  TRANSFORMATIONS  OF  ORGANIC 
COMPOUNDS. 

Organic  bodies  are,  generally  speaking,  distinguished  by  the  facility  with 
which  they  decompose  under  the  influence  of  heat  or  of  chemical  reagents : 
the  more  complex  the  body,  the  more  easily  does  it  undergo  decomposition 
or  transformation. 

1.  Action  of  Heat. — Organic  bodies  of  simple  constitution  and  of  some 
permanence,  but  not  capable  of  subliming  unchanged,  like  many  of  the  organic 
acids,  yield,  when  exposed  to  a  high,  but  regulated  temperature,  in  a  retort, 
new  compounds,  perfectly  definite  and  often  crystallizable,  which  partake, 
to  a  certain  extent,  of  the  properties  of  the  original  substance  :  the  numer- 
ous pyro-adds,  of  which  many  examples  will  occur  in  the  succeeding  pages, 
are  thus  produced.     Carbon  dioxide  and  water  are  often  eliminated  under 
these  circumstances.     If  the  heat  be  suddenly  raised  to  redness,  the  regu- 
larity of  the  decomposition  vanishes,  while  the  products  become  more  un- 
certain and  more  numerous;  carbon  dioxide  and  watery  vapor  are  suc- 
ceeded by  inflammable  gases,  as  carbon  monoxide  and  hydrocarbons;  oily 
matter  and  tar  distil  over,  and  increase  in  quantity  until  the  close  of  the 
operation,  when  the  retort  is  found  to  contain,  in  most  cases,  a  residue  of 
charcoal.     Such  is  dry  or  destructive  distillation. 

If  the  organic  substance  contains  nitrogen,  and  is  not  of  a  kind  capable 
of  taking  a  new  and  permanent  form, at  a  moderate  degree  of  heat,  then 
that  nitrogen  is  in  most  instances  partly  disengaged  in  the  shape  of  ammo- 
nia, or  substances  analogous  to  it,  partly  left  in  combination  with  the  car- 
bonaceous matter  in  the  distillatory  vessel.  The  products  of  dry  distillation 
thus  become  still  more  complicated. 

A  much  greater  degree  of  regularity  is  observed  in  the  effects  of  heat  on 
fixed  organic  matters,  when  these  are  previously  mixed  with  an  excess  of 
strong  alkaline  base,  as  potash  or  lime.  In  such  cases  an  acid,  the  nature 
of  which  is  chiefly  dependent  upon  the  temperature  applied,  is  produced, 
and  remains  in  union  with  the  base,  the  residual  element  or  elements  escap- 
ing in  some  volatile  form.  Thus  benzoic  acid  distilled  with  calcium  hy- 
drate, at  a  dull  red  heat,  yields  calcium  carbonate  and  benzene ;  woody 
fibre  and  caustic  potash,  heated  to  a  very  moderate  temperature,  yield  free 
hydrogen,  and  a  brown,  somewhat  indefinite  substance  called  ulmic  acid; 
with  a  higher  degree  of  heat,  oxalic  acid  appears  in  the  place  of  the  ulmic  ; 
and,  at  the  temperature  of  ignition,  carbon  dioxide,  hydrogen  being  the 
other  product. 

2.  Action  of  Oxygen. — Oxygen,  either  free   or  in  the  nascent  state,  in 
which  latter  condition  it  is  most  active,  may  act  on  organic  compounds  in 
four  different  ways: 

a.  By  simple  addition,  as 

C2H40  +  0  =  C2H402 

Aldehyde.  Acetic  acid.  * 

/?.  By  simply  removing  hydrogen: 

C2H60  -f  0  =  OH2  -f  C2H40 
Alcohol.  Aldehyde. 

y.  By  removing  hydrogen  and  taking  its  place,  2  atoms  of  hydrogen  being 
replaced  by  one  of  oxygen  ;  e.  g.  : 

C2H60  +  0,  =  OH2  +  CJT402 
Alcohol.  Acetic  acid. 


OF    ORGANIC    COMPOUNDS.  463 

t.  By  removing  both  carbon  and  hydrogen.  In  this  manner  complex 
organic  bodies  containing  large  numbers  of  carbon  and  hydrogen  atoms  are 
reduced  to  others  of  simpler  constitution,  and  ultimately  the  carbon  and 
hydrogen  are  wholly  converted  into  carbon  dioxide  and  water.  Nitrogen, 
chlorine,  bromine,  and  iodine,  if  present,  are  at  the  same  time  disengaged, 
for  the  most  part  in  the  free  state,  and  sulphur  is  oxidized. 

Moist  organic  substances,  especially  those  containing  nitrogen,  undergo, 
when  exposed  to  the  air,  a  slow  process  of  oxidation,  by  which  the  organic 
matter  is  gradually  burned  and  destroyed  without  sensible  elevation  of 
temperature;  this  process  is  called  Decay,  or  Eremacausis.  Closely  con- 
nected with  this  change  are  those  called  Fermentation  and  Putrefaction,  con- 
sisting in  a  new  arrangement  of  the  elements  of  the  compound  (often  with 
assimilation  of  the  elements  of  water),  and  the  consequent  formation  of  new 
products.  The  change  is  called  putrefaction,  when  it  is  accompanied  by  an 
offensive  odor;  fermentation,  when  no  such  odor  is  evolved,  and  especially 
if  the  change  results  in  the  formation  of  useful  products :  thus,  the  decom- 
position of  a  dead  body,  or  of  blood  or  urine,  is  putrefaction ;  that  of  grape- 
juice  or  malt-wort,  which  yields  alcohol,  is  fermentation.  Putrefaction 
and  fermentation  are  not  processes  of  oxidation  ;  nevertheless,  the  presence 
of  oxygen  appears  to  be  indispensable  to  their  commencement;  but  the 
change,  when  once  begun,  proceeds  without  the  aid  of  any  other  substance 
external  to  the  decomposing  body,  unless  it  be  water  or  its  elements.  Every 
case  of  putrefaction  thus  begins  with  decay ;  and  if  the  decay,  or  its  cause, 
namely,  the  absorption  of  oxygen,  be  prevented,  no  putrefaction  occurs. 
The  most  putrescible  substances,  as  animal  flesh  intended  for  food,  milk, 
and  highly  azotized  vegetables,  are  preserved  indefinitely,  by  enclosure  in 
metallic  cases  from  which  the  air  has  been  completely  removed  and  excluded. 

Fermentation  and  putrefaction  are  always  accompanied  by  the  develop- 
ment of  certain  living  organisms  of  the  fungous  class;  but  whether  the 
growth  of  these  is  a  cause  or  a  consequence  of  the  chemical  change  is  a 
point  not  yet  decided.  We  shall  return  to  this  subject  in  speaking  of  the 
fermentation  of  sugar. 

3.  ^Action  of  Chlorine,  Bromine,  and  Iodine. — Chlorine  and  bromine  exert 
precisely  similar  actions  on  organic  bodies ;  that  of  chlorine  is  the  more 
energetic  of  the  two.  The  reactions  consist: 

a.  In  simple  addition  of  chlorine  or  bromine  to  the  organic  molecule ;  e.  g. : 

C4H404  +  Br2  =  C4H4Br204 
Fumaric  Dibromosuccinic 

acid.  acid. 

/?.  In  removal  of  hydrogen  without  substitution : 

C2H60  -f  C12  =  2HC1  +  C2H40 
Alcohol.  Aldehyde. 

y.  In  substitution  of  chlorine  or  bromine  for  hydrogen : 

C2H402  -f  C12  =  HC1  +  C2H3C102 
Acetic  Chloracetic 

acid.  acid. 

C2H402  -f  3C12  =  3HC1  +  C2HC1302 
Acetic  Trichloracetic 

acid.  acid 

The  substitution-products  thus  formed  undergo  transformations  closely 
analogous  to  those  of  the  original  compounds,  under  the  influence  of  simi- 
lar reagents ;  but  they  are  always  more  acid,  or  less  basylous,  in  propor- 


464:         DECOMPOSITIONS   AND    TRANSFORMATIONS 

tion  to  the  quantity  of  chlorine  or  bromine  substituted  for  hydrogen.  Thus 
aniline,  C6H7N,  which  is  a  strong  base,  may  be  converted,  by  processes  to 
be  hereafter  described,  into  the  chlorinated  compounds,  C6H6C1N,  C6H5C12N, 
and  C6H4C13N,  the  first  and  second  of  which  are  less  basic  than  aniline 
itself,  while  the  third  does  not  show  any  tendency  to  form  salts  with  acids. 

6.  In  presence  of  water  they  remove  the  hydrogen  of  that  liquid,  arid  set 
free  the  oxygen:  hence,  chlorine-water  and  bromine-water  act  as  powerful 
oxidizing  agents. 

Iodine  may  also  act  in  this  manner  as  an  oxidizing  agent;  and  it  some- 
times attaches  itself  directly  to  organic  molecules ;  but  it  never  acts  directly 
by  substitution.  Iodine  substitution-products  may,  however,  be  obtained 
in  some  cases  by  treating  organic  bodies  with  chloride  of  iodine,  the  chlor- 
ine then  removing  hydrogen,  and  the  iodine  taking  its  place. 

4.  Action  of  Nitric  Acid.  —  This  acid  acts  very  powerfully  on  organic  sub- 
stances.    The  action  may  be  of  three  kinds: 

a.  Direct  combination,  as  with  organic  bases ;  e.  g. : 

C2H7N     -f     N03H    =    C2H7N.N03H 
Ethylamine.        Nitric  Ethylamine 

acid.  nitrate. 

/?.  Oxidation.  This  mode  of  action  is  most  frequently  observed  with  the 
somewhat  diluted  acid. 

y.  Substitution  of  nitryl  (N02)  for  hydrogen ;  e.  g. : 

C6H6    +     N02(OH)     =    OH2    -f-     C6H5(N02) 
Benzene.       Nitric  acid.  Nitrobenzene. 

C6H1005    +    3N02(OH)    =    30H2   -f     C6H7(N02)305 
Cellulose.          Nitric  acid.  Tritrocellulose 

(gun-cotton). 

This  action  takes  place  most  readily  with  the  strongest  nitric  acid  (pure 
hydrogen  nitrate).  The  products  (called  nitro-compounds}  are  always  easily 
combustible,  and  in  many  cases  highly  explosive. 

5.  Action  of  Alkalies. — The  hydrates  of  potassium   and  sodium  act   on 
organic  bodies  in  a  great  variety  of  ways,  the  most  important  and  general 
of  which  are  the  following:  — 

a.  By  direct  combination: 

CO          -f          OKH        =        CHK02 

Carbon  Potassium  Potassium 

monoxide.  hydrate.  formate. 

C,0H160      +          OKH        =      C10H17K02 
Camphor.  Potassium  Potassium 

hydrate.  campholate. 

/?.  By  double  decomposition  with  acids,  water  being  eliminated,  and  a 
salt  produced : 

C2H?02.H         -f        OKH       =        OH,        +        C2H302.K 
Acetic  acid.  Potassium 

acetate. 
y.  Oxidation,  with  elimination  of  hydrogen: 

C2H60    -f     OKH    =    C2H3K02    -f     2H2 
Alcohol.  Potassium 

acetate. 

i.  From  chlorinated  compounds  they  remove  a  part  or  the  whole  of  the 
chlorine : 


OF    ORGANIC    COMPOUNDS. 


465 


C2H4C12 
Ethene 
chloride. 

C6HUC1 

Amyl 

chloride. 


OKH       = 


-f       OKH      = 


C2H3C1 
Chlor- 
ethene. 


Amylene. 


KC1 


OH2 


e.  Amides  (pp.  315,  471)  are  decomposed  by  them  in  such  a  manner  that 
the  whole  of  the  nitrogen  is  given  off  as  ammonia,  and  a  potassium  or 
sodium  salt  of  the  corresponding  acid  is  produced : 

NH2.C2H50     -f     OKH     =     NH3    +     C2H3O.OK 
Acetamide.  Potassium 

acetate. 

Many  other  azotized  organic  compounds,  when  heated  with  alkaline 
hydrates,  likewise  give  up  the  whole  of  their  hydrogen  in  the  form  of 
ammonia. 

6.  Action  of  Reducing  Agents.  —  This  name  is  given  to  bodies  whose  action 
is  the  inverse  of  that  of  oxygen,  chlorine,  bromine,  and  iodine ;  such  are 
nascent  hydrogen,  obtained  by  the  action  of  sodium-amalgam  on  water,  or 
by  that  of  zinc  on  aqueous  acids  or  alkalies ;  also  hydrogen  sulphide,  am- 
monium sulphide,  sulphurous  acid,  and  metals,  especially  potassium  and 
sodium,  all  of  which  either  give  up  hydrogen,  or  abstract  oxygen,  chlor- 
ine, &c. 

Reducing  agents  may  act  in  the  following  ways:- — 

a.  By  adding  hydrogen  to  an  organic  body : 


Ethene 
oxide. 


HH    —    C2H60 
Alcohol. 


0.  By  removing  oxygen,  chlorine,  bromine,  or  iodine,  without  introducing 
anything  in  its  place  ;  thus : 


C7H602 

Benzoic 

acid. 


HH     =     OH 


Benzoic 
aldehyde. 


Y.  By  substituting  hydrogen  for  oxygen,  chlorine,  &c.  This  process  is 
called  inverse  substitution.  It  may  take  place  either  in  equivalent  quanti- 
ties; e.g.: 

C7H50  .  OH     -f     2HH    =•    OH2    -f-     C7H7  .  OH 
Benzoic  Benzylic 

acid  alcohol 

or  it  may  happen  that  the  quantity  of  hydrogen  introduced  is  only  half 
that  which  is  equivalent  to  the  oxygen  removed.  This  mode  of  substitu- 
tion takes  place  with  nitro-compounds,  which  are  thereby  reduced  to  others 
containing  amidogen,  (NH2),  in  place  of  nitryl,  (N02) ;  thus : 


3IL 


Nitrobenzene. 


20H2 


C6H5(NH2) 

Amidobenzene 

(aniline). 


A  large  number  of  organic  bases  are  formed  in  this  manner  from  nitro- 
compounds. 

7.  Action  of  Dehydrating  Agents. — Strong  sulphuric  acid,  sulphuric  oxide, 
phosphoric  oxide,  and  zinc  chloride  remove  oxygen  and  hydrogen  from 
organic  bodies  in  the  form  of  water,  the  elements  of  which  are  derived, 


466         CLASSIFICATION    OF    ORGANIC    COMPOUNDS. 

sometimes  from  a  single  molecule  of  the  organic  body,  sometimes  from  two 
molecules : 

C2H60    —     OH2     =     C2H4 
Alcohol.  Ethene. 

2C2H60    —    OH2    =    C4H100 
Alcohol.  Ether. 

Compounds  which,  like  sugar,  starch,  and  woody  fibre,  consist  of  carbon 
united  with  hydrogen  and  oxygen  in  the  proportions  to  form  water,  are 
often  reduced  by  these  dehydrating  agents  to  black  substances  consisting 
mainly  of  carbon. 

Other  reactions  of  less  generality  than  those  above  described  will  be  suffi- 
ciently illustrated  by  special  cases  in  the  sequel. 


CLASSIFICATION   OF   ORGANIC  COMPOUNDS.  —  ORGANIC   SERIES. 

The  classification  of  organic  compounds  is  based  upon  the  equivalence  or 
atomicity  of  carbon.  This  element  is  a  tetrad,  being  capable  of  uniting 
with  at  most  four  atoms  of  hydrogen  or  other  monatomic  elements.  Me- 
thane or  marsh  gas,  CH4,  is  therefore  a  saturated  hydro-carbon,  not  capa- 
ble of  uniting  directly  with  chlorine,  bromine,  or  other  monad  elements, 
but  only  of  exchanging  a  part  or  the  whole  of  its  hydrogen  for  an  equiv- 
alent quantity  of  another  monad  element.  It  may,  however,  as  already 
explained  (p.  235),  take  up  any  number  of  dyad  elements  or  radicals,  be- 
cause such  a  radical  introduced  into  any  group  of  atoms  whatever,  neutral- 
izes one  unit  of  equivalency,  and  adds  another,  leaving  therefore  the  com- 
bining power  or  equivalence  of  the  group  just  the  same  as  before.  Ac- 
cordingly, the  hydro-carbon,  CH4,  may  take  up  any  number  of  molecules 
of  the  bivalent,  radical,  CH2,  thereby  giving  rise  to  the  series  of  saturated 
hydro-carbons, 


CH4,        C2H6,         C3H8,         C4H10  .  .  .  . 

A  series  of  compounds,  the  terms  of  which  differ  from  one  another  by 
CH2,  is  called  an  homologous  series.  There  are  many  such  series  besides  that 
of  the  hydro-carbons  just  mentioned  ;  thus  methyl-chloride,  CH3C1,  gives 
by  continued  addition  of  CH2,  the  series  of  chlorides, 

CH3C1,        C2H5C1,        C3H7C1,         C4H9C1  .  .  .  C  11^+  Cl; 

and  from  methyl-alcohol,  CH40,  is  derived  in  like  manner  the  series  of 
homologous  alcohols, 

CH40,        C2H60,        C3H80,        C4H100  .  .  .  C.Hto+  0. 

The  terms  of  the  same  homologous  series  resemble  one  another  in  many 
respects,  exhibiting  similar  transformations  under  the  action  of  given  re- 
agents, and  a  regular  gradation  of  properties  from  the  lowest  to  the  high- 
est ;  thus,  of  the  hydro-carbons,  Cn  H2n+2,  the  lowest  terms  CH4,  C2H6,  and 
C3H8,  are  gaseous  at  ordinary  temperatures,  the  highest  containing  20  or 
more  carbon-atoms,  are  solid,  while  the  intermediate  compounds  are  liquids, 
becoming  more  and  more  viscid  and  less  volatile,  as  they  contain  a  greater 
number  of  carbon-atoms,  and  exhibiting  a  constant  rise  of  about  20°  C. 
(36°  F.)  in  their  boiling  points  for  each  addition  of  CH2  to  the  molecule. 

The  saturated  hydro-carbons,  Cn  H2n-j-2>  may,  under  various  circumstances, 

*  See  page  234. 


ORGANIC  SERIES.  467 

be  deprived  of  two  atoms,  or  one  molecule,  of  hydrogen,  thereby  producing 
a  new  homologous  series, 

CH2,         C2H4,        C3H6,        C4H8  .  .  .  CjjHj,, 

These  are  unsaturated  molecules,  having  two  units  of  equivalency  uncom- 
bined,  and  therefore  acting  as  bivalent  radicals,  capable  of  taking  up  2 
atoms  of  chlorine,  bromine,  or  other  univalent  radicals,  and  1  atom  of  oxy- 
gen or  other  bivalent  radical. 

The  first  term  of  this  last  series  cannot  give  up  2  atoms  of  hydrogen 
without  being  reduced  to  the  atom  of  carbon  ;  but  the  remaining  terms  may 
each  give  up  2  atoms  of  hydrogen,  and  thus  give  rise  to  the  series, 

C2H2,         C3H4,         C4H6  ....  CnH2n_2. 

each  term  of  which  is  a  quadrivalent  radical. 

And,  in  like  manner,  by  successive  abstractions  of  H2,  a  number  of  ho- 
mologous series  may  be  formed  whose  general  terms  are 

CnH2n+2>     (^H2".     CaH^.     CuH2n_4  .  .  .  .  &c. 

The  individual  series,  as  far  as  C6,  are  given  in  the  following  table,  to- 
gether with  the  names  proposed  for  them  by  Dr.  Hofmann  :  * 

CH4          CH2 

Methane  Methene 

C2H6         C2H4         C2H2 

Ethane  Ethene      Ethine 

CgHg  CgHg  CgF^  Cgllj 

Propane   Propene   Propine   Propone 

C4H10        C4H8         C4H6         C4H4        C4H2 
Quartane  Quartene  Quartine  Quart  one  Quartune 

C5H12        C5H10        C5H8         C5H6        C5H4        C6H, 
Quintane  Quintene    Quintine  Qumtone  Quintune 

C6H,4        C6H,2        C6H10        C6H8        C6H6        C6H4        C6H2. 
Sextane     Sextene   Sextine     Sextone   Sextune 

Each  vertical  column  of  this  table  forms  a  homologous  series,  in  which 
the  terms  differ  by  CH2,  and  each  horizontal  line  an  isologous  series,  in  which 
the  successive  terms  differ  by  H2.  The  bodies  of  these  last  series  are 
designated  as  the  monocarbon,  dicarbon  group,  &c. 

The  formulae  in  the  preceding  table  represent  hydrocarbons  all  of 
which  are  capable  of  existing  in  the  separate  state,  and  many  of  which 
have  been  actually  obtained.  They  are  all  derived  from  saturated  mole- 
cules, Cn  Hon+2,  by  abstraction  of  one  or  more  pairs  of  hydrogen-atoms. 

But  a  saturated  hydrocarbon,  CH4,  for  example,  may  give  up  1,  2,  3,  or 
any  number  of  hydrogen-atoms  in  exchange  for  other  elements;  thus  marsh 
gas,  CH4,  subjected  to  the  action  of  chlorine  under  various  circumstances, 
yields  the  substitution-  products, 

CH3C1,  CH2C12,  CHC13,  CC14, 

which  may  be  regarded  as  compounds  of  chlorine  with  the  radicals, 
(CH3)',  (CH2)",  (CH3)'",  C"; 

and  in  like  manner  each  hydrocarbon  of  the  series,  Cn  H^-f^,  may  yield  a 
series  of  radicals  of  the  forms, 

&c. 


each  of  which  has  an  equivalent  value,  or  combining  power,  corresponding 
*  Proceedings  of  the  Royal  Society,  xv.  57. 


468         CLASSIFICATION    OF    ORGANIC    COMPOUNDS. 

with  the  number  of  hydrogen-atoms  abstracted  from  the  original  hydro- 
carbon. Those  of  even  equivalence  contain  even  numbers  of  hydrogen- 
atoms,  and  are  identical  in  composition  with  those  in  the  table  above  given; 
but  those  of  uneven  equivalence  contain  odd  numbers  of  hydrogen-atoms, 
and  are  incapable  of  existing  in  the  separate  state,  except,  perhaps,  as 
double  molecules  (p.  238). 

These  hydrocarbon  radicals  of  uneven  equivalence  are  designated  by 
names  ending  in  yl,  those  of  the  univalent  radicals  being  formed  from  me- 
thane, ethene,  &c.,  by  changing  the  termination  ane  into  yl;  those  of  the 
trivalent  radicals  by  changing  the  final  e  in  the  names  of  the  bivalent 
radicals,  methene,  &c.,  into  yl  ;  and  similarly  for  the  rest.  The  names  of 
the  whole  series  will  therefore  be  as  follows:  — 

CH4      (CH3)'  (CH2)"'     (CH)'" 

Methane  Methyl  Methene  Methenyl 

C2H6     (C8H6)'  (C8H4)"     (C,H,)"/  (C2H2)"     (C2H)* 

Ethane      Ethyl  Ethene       Ethenyl  Ethine      Ethinyl 

C3H8     (C,HT)'  (C,Hj)"     (C,H6)'"  (C8H4)*     (C,H,)*    (C3H2)*  (C.H)* 

Propane  Propyl  Propene    Propenyl  Propine  Propinyl  Propone  Proponyl. 

&c.  &c.  &c. 

From  these  hydrocarbon  radicals,  others  of  the  same  degree  of  equiva- 
lence may  be  derived  by  partial  or  total  replacement  of  the  hydrogen  by 
other  elements,  or  compound  radicals.  Thus  from  propyl,  C3H7,  may  be 
derived  the  following  univalent  radicals  :  — 

C3H6C1            C3H3C14            C3H50            C3H2C130  C3H6(CN)' 

Chloropropyl    Tetrachloro-    Oxypropyl        Trichlor-  Cyanopropyl. 

propyl  oxy  propyl 

C3H6(N02)            C3H4(NH2)0            C3H6(CH3)  C3H5(C2H5)2 

Nitropropyl         Amidoxypropyl      Methylpropyl  Diethylpropyl. 

From  the  radicals  above  mentioned,  all  well-defined  organic  compounds 
may  be  supposed  to  be  formed  by  combination  and  substitution,  each  radical 
entering  into  combination,  just  like  an  elementary  body  of  the  same  degree 
of  equivalence. 

Organic  compounds  may  thus  be  arranged  in  the  following  classes  : 

I.  Hydrocarbons  containing  even  numbers  of  hydrogen  atoms.  —  These  are  the 
compounds  tabulated  on  page  467  ;  they  are  sometimes  regarded  as  hy- 
drides of  radicals  containing  uneven  numbers  of  hydrogen  atoms;  e.  g+: 

Methane,  CH4     =     CH3  .  H,  Methyl  hydride. 

II.  Halo'id  Ethers.  —  Compounds  of  hydrocarbons  with  halogens  ;  e.  g.  : 

CHSC1  C2H4Br2  C3H6I3 

Methyl  chloride.         Ethene  bromide.         Propenyl  iodide. 

These  compounds  are  often  formed  by  direct  substitution  of  chlorine,  bro- 
mine, &c.,  for  hydrogen  in  hydrocarbons  containing  even  numbers  of  hydro- 
gen atoms. 

III.  Alcohols.  —  Compounds  of  hydrocarbon  radicals  (hence  called  alcohol 
radicals),  with  hydroxyl  ;  e.  g.  : 


C,H6(HO)  (CAX'CHO),  (C,H6)"/(HO)S 

Ethyl  alcohol.  Ethene  alcohol  Propenyl  alcohol 

(Glycol).  (Glycerin). 

These  compounds  may  be  formed  from  the  corresponding  haloid  ethers,  by 
the  action  of  water  or  alkalies,  just  as  metallic  hydrates  are  formed  from 
the  corresponding  chlorides,  &c. 


CLASSIFICATION    OF    ORGANIC    COMPOUNDS.         469 

IV.  Oxygen  Ethers,   or  Alcoholic    Oxides.  —  Compounds   of   hydrocarbon 
radicals  with  oxygen  ;  e.  g.  : 

(C2H5)20  (C,H4)"0  (C3H6)'"203 

Ethyl  Ethene  Propenyl 

oxide.  oxide.  oxide. 

These  ethers  are  related  to  the  alcohols  in  the  same  manner  as  anhydrous 
metallic  oxides  to  the  corresponding  hydrates  or  hydrylates,  and  may  be 
formed,  in  many  instances,  by  direct  dehydration  of  the  alcohols,  as  by  the 
action  of  sulphuric  acid,  zinc  chloride,  &c. 

V.  Sulphur  and  Selenium  Alcohols  and  Ethers.  —  Compounds  analogous  in 
composition  to  the  oxygen  alcohols  and  ethers,  the  oxygen  being  replaced 
by  sulphur  or  selenium.     The  sulphur  and  selenium  alcohols  are  also  called 
mercaptans. 

VI.  Acid  Halides.  —  Compounds  of  oxygenated  radicals  (acid  radicals) 
with  chlorine,  bromine,  &c.  ;  e.  g.  : 


C2H3O.C1  (C4H40?)"Cla  (CsHsOV'Cls 

Acetyl  Succinyl  Citryl  chloride. 

chloride.  chloride. 

These  compounds  are  formed  by  the  action  of  the  chlorides,  bromides,  &c., 
of  phosphorus  on  the  compounds  of  the  next  class. 

VII.  Organic  Acids.  —  Compounds  of  oxygenated  radicals  with  hydroxyl; 

C2H30  .  HO  (C4H40,)"  .  (HO),  (C.H804)'"  .  (HO), 

Acetic  acid.  Succinic  acid.  Citric  acid. 

These  compounds  are  formed  in  a  variety  of  ways;  among  others,  by  oxi- 
dation of  alcohols,  and  by  the  action  of  water  on  the  corresponding  acid 
halides,  just  as  alcohols  are  formed  from  alcoholic  chlorides.  A  very  large 
number  of  them  exist  also  ready-formed  in  the  bodies  of  plants  and  ani- 
mals. 

The  hydrogen  in  the  radicals  of  these  acids  may  be  more  or  less  replaced 
by  chlorine,  bromine,  nitryl,  (N02),  and  other  chlorous  radicals;  thus, 
from  benzoic  acid,  C7H5.  HO,  are  derived: 

C7H4C10  .  HO        C7H5(N02)0  .  HO        C7H5(NH2)0  .  HO 
Chlorobenzoic  Nitrobenzoic  Amidobenzoic 

acid.  acid.  acid. 

VIII.  Acid  Oxides,  sometimes  called  Anhydrous  acids,  or  Anhydrides; 

(C2H30)20  (C,H40,)"0  (C2H30)(C?H50)0 

Acetic  oxide.         Succinic  oxide.       Acetobenzoic  oxide. 

These  are  related  to  the  acids  in  the  same  manner  as  the  oxygen-ethers  to 
the  alcohols,  and  are  formed  from  them  in  some  instances  by  direct  dehy- 
dration. 

IX.  Ethereal  Salts,    also  called   Compound  Ethers.  —  Compounds  formed 
from  acids  by  substitution  of  alcohol  radicals  for  hydrogen,  just  as  metallic 
salts  are  produced  by  substitution  of  metals  for  the  hydrogen  in  acids  ; 
e.g.: 

C2H302  .  H  S04  .  HII  P04  .HHH 

Acetic  Sulphuric  Phosphoric 
acid.                        acid.  acid. 

40 


470         CLASSIFICATION    OF    ORGANIC    COMPOUNDS. 

C2H302.  C2H5  S04.  (C2H5)H  P04.  (C2H5)HH 

Ethylic  Monet  hylic  Monethylic 

acetate.  sulphate.  phosphate. 

o/~v        /p   TJ   \  T>A        I '{*i  VJ   \    IT 

i^vJ4  .    (^O^lfi/Q  ±\J*.     IV^nllcJrttl 

Diethylic  Diethylic 

sulphate.  phosphate. 

P04.(C2H5)3 
Triethylic 
phosphate. 

They  are  produced  in  many  cases  by  heating  an  acid  or  the  corresponding 
chloride  with  an  alcohol. 

X.  Aldehydes.  —  These  are  compounds  intermediate  between  alcohols 
and  acids.     Thus: 

C2H60  C2H40  C2H402 

Ethyl  Acetic  Acetic 

alcohol.  aldehyde.  acid. 

They  are  produced  by  oxidation  of  alcohols,  and  are  reconverted  into  the 
latter  by  the  action  of  nascent  hydrogen.  By  further  oxidation  they  are 
converted  into  acids. 

XI.  Ketones. — These  are  bodies  derived  from  aldehydes  by  the  replace- 
ment  of  1  atom  of  hydrogen  by  an  alcohol  radical;  e.g. : 

Acetic  ketone  or  Acetone,  C3H60  =  C2H3(CH3)0. 

They  are  produced  by  the  dry  distillation  of  the  calcium  or  barium  salts 
of  monobasic  acids,  and  by  other  processes  which  will  be  mentioned  fur- 
ther on. 

XII.  Amines,   also   called  Alcohol-bases,  or    Compound  ammonias.  —  Com- 
pounds of  alcohol  radicals  with  amidogen,  (Nt^)',  imidogen,  (NH)'',  and 
trivalent  nitrogen ;  e.  g.  : 

C2H5 .  H2N  (C2H5)2 .  HN  (C2H5)3N 

Ethylamine.  Diethylamine.  Triethylamine. 


(C2H4)" .  (H2N)2         (C2H4)"2.  (HN)2  {C.H4)"tvNr 

Ethene-diamine.         Diethene-diamine.       Triethene-diamine. 

The  modes  of  formation  of  these  bodies  will  be  explained  hereafter. 
They  are  mostly  of  basic  character,  and  capable  of  forming  salts  with 
acids,  like  ammonia,  H3N,  from  which  they  may,  in  fact,  be  derived  by 
substitution  of  alcohol  radicals  for  part  or  the  whole  of  the  hydrogen. 
Those  in  which  the  hydrogen  is  wholly  thus  replaced  are  called  nitriles; 
and  among  these  special  mention  must  be  made  of  a  group  consisting  of 
nitrogen  combined  with  a  trivalent  hydrocarbon  radical,  such  as  — 

(CH)'"N  (C2H3)'"N  (CSH6)'"N 

Methenyl  Ethenyl  Propenyl 

nitrile.  nitrile.  nitrile. 

These  nitriles  have  no  basic  properties,  but  are  all  neutral,  except  the 
first,  which  is  a  monobasic  acid,  capable  of  exchanging  its  hydrogen  for 
metals,  and  in  this  character  may  be  regarded  as  a  compound  of  hydrogen 
with  the  univalent  radical  cyanogen  —  C  — N;  it  is  accordingly  named  hy- 
drogen cyanide,  or  hydrocyanic  acid,  and  the  other  nitriles  homologous  with 
it  are  the  ethers  of  this  acid ;  thus : 


CLASSIFICATION   OP    ORGANIC    COMPOUNDS.        471 

Methenyl  nitrile,  (CH)777N  =  CN.  H,  Hydrogen  cyanide, 
Ethenyl  nitrile,  (C1Hf(/'yH  =  CN.  CH3,  Methyl  cyanide, 
Propenyl  nitrile,  (C3H5)777N  =  CN.  C2H6,  Ethyl  cyanide. 

The  metallic  cyanides  have  been  already  noticed  (p.  277). 

XIII.  Alcoholic   Ammonium-compounds. — Compounds    containing   pentad 
nitrogen,  and  having  the  composition  of  ammonium  salts  in  which  the  hy- 
drogen is  more  or  less  replaced  by  alcohol  radicals  ;  e.g. : 

NT(C2H5)H3Cl  Ethylammonium  chloride, 

NT(CaH8)2H2Cl  Diethylammonium  chloride, 

Nv(C2H5)3HCl  Triethylammonium  chloride, 

N>(C8Hfti4Cl  Tetrethylammonium  chloride, 

NT(C2H5)4(HO)  Tetrethylammonium  hydrylate. 

This  last  compound  and  its  analogues,  containing  methyl,  amyl,  &c.,  are 
powerful  alkalies,  obtainable  in  the  solid  state,  by  evaporation  of  their 
aqueous  solutions,  as  white  deliquescent  crystalline  masses  resembling 
caustic  potash. 

XIV.  Phosphorus,  Arsenic,   and  Antimony   Compounds,   analogous  to  the 
nitrogen  compounds  XII.  and  XIII. ;  e.  g. : 

P'"(CH8)S  As"/(C2H5)3  Sb'"(C,HB), 

Triethyl  phos-  Tricthyl  Triethyl 

phine.  arsine.  stibine. 

P'(CH3)4C1  As*(CH,)(C,H5)sCl  SV(C,H6)4(HO) 

Tetramethyl-  Methyl-triethyl-ar-  ,      Tetrethyl-sti- 

phosphonium  sonium  chloride.  bonium  hydrate. 

chloride. 

XV.  Organo-metallic   bodies,   not   analogous   to    ammonia    or  ammonium 
salts.  —  Compounds  of  hydrocarbon  radicals  with  monad,  dyad,  and  tetrad 
metals;  e.g.: 

NaC2H6  Zn"(CH8)2  Sn*(C2H6)lr 

Sodium  ethide.  Zinc  ethide.  Stannic  ethide. 

Hg"(CH,)Cl  Sn"(C2H5)Cl3  Sn*(CH3)2I2 

Mercuric  chloro-          Stannic  chloro-  Stannic  dimethyl 

methide.  triethide.  di-iodide. 

XVI.  Amides. — Compounds  exactly  analogous  to  the  amines,  but  with 
aciu  radicals  instead  of  alcohol  radicals ;  those  which  contain  bivalent  acid 
radicals  combined  with  imidogen,  (NH)77,  are  called  imides;  e.g.: 

Acetamide  C2H3O.H2N  Succinamide       (C4H402)77.  (H2N)2 

Diacetamide       (C2H30)2.HN 
Succinimide     (C4H4O2)77 .  HN 


Citramide  (C6H604)'" .  N777. 


XVII.  Amic  acids  — Acids  consisting  of  a  bivalent  or  trivalent  acid  rad- 
ical combined  with  hydroxyl  and  with  amidogen ;  e.  g. : 

Succinamic  acid  (C4H402)".  HO.  H2N 
Citramic  acid*  (C6H5O4)777.  HO.  (HN)77. 

Each  of  the  classes  of  carbon  compounds  above  enumerated  may  be  di- 
vided into  homologous  and  isologous  groups,  though  in  most  cases  the  series 
are  far  from  being  complete. 

*  This  compound  is  not  actually  known;  but  its  derivative,  phenyl-citramic  acid,  (C6U&Ot)'". 
C6II50 .  UN,  has  been  obtained. 


472         CLASSIFICATION    OF    ORGANIC    COMPOUNDS. 

The  preceding  classes,  most  of  which  have  their  analogues  amongst  in- 
organic compounds,  include  nearly  all  artificially  prepared  organic  bodies, 
and  the  majority  of  those  produced  in  the  living  organism.  There  are  still, 
however,  many  compounds  formed  in  the  bodies  of  plants  and  animals,  the 
chemical  relations  of  which  are  not  yet  sufficiently  well  made  out  to  enable 
us  to  classify  them  with  certainty.  Such  is  the  case  with  many  vegetable 
oils  and  resins,  with  most  of  the  alkaloids  or  basic  nitrogenized  compounds 
found  in  plants,  such  as  morphine,  quinine,  strychnine,  &c.,  and  several 
definite  compounds  formed  in  the  animal  organism,  as  albumin,  fibrin, 
casein,  and  gelatin. 

Rational  Formulae  of  Organic  Compounds  —  It  must  be  distinctly  under- 
stood that  the  formulae  above  given  are  not  the  only  ones  by  which  the 
constitution  of  the  several  classes  of  organic  compounds  may  be  repre- 
sented. Rational  formulae  are  intended  to  represent  the  mode  of  formation 
and  decomposition  of  compounds,  and  the  relation  which  allied  compounds 
bear  to  one  another:  hence,  if  a  compound  can,  under  varying  circum- 
stances, split  up  into  different  atomic  groups  or  radicals,  or  if  it  can  be 
formed  in  various  ways  by  the  combination  of  such  radicals,  different  ra- 
tional formulae  must  be  assigned  to  it.  This  point  has  been  already  noticed 
in  connection  with  the  constitution  of  metallic  salts,  and  illustrated  espe- 
cially in  the  case  of  the  sulphates  (p.  281)  ;  but  organic  compounds,  which 
for  the  most  part  contain  larger  numbers  of  atoms,  and  are  therefore 
capable  of  division  into  a  greater  number  of  groups,  afford  much  more 
abundant  illustration  of  the  same  principle.  Take,  for  example,  acetic 
acid,  the  molecular  formula  of  which  is  C2H402.  This  may  be  resolved  into 
the  following  rational  formulae  : 

1.  C2H302.H.  —  This  formula,  analogous  to  that  of  hydrochloric  acid, 
Cl.  H,  indicates  that  a  molecule  of  acetic  acid  can  give  up  one  atom  of  hy- 
drogen  in   exchange  for  a  univalent  metal  or  alcohol-radical,  forming,  for 
example,  sodium  acetate,  C2H302.  Na,  ethyl  acetate,  C2H30.  C2H5,  &c.  ;  that 
two  molecules  of  the  acid  may  give  up  two  hydrogen  atoms  in  exchange  for 
a  bivalent  metal  or  alcohol-radical,  forming  barium  acetate,  (C2H302)2Ba//, 
ethene  acetate,  (C2H3O2)2.  (C3H4y/J  &c.  ;  in  other  words,  that  acetic  acid 
is  a  monobasic  acid  (p.  282). 

2.  C2H30  .  HO.  —  This  formula,  analogous  to  that  of  water,  H  .  HO,  cor- 
responds to  such  reactions  as  the  formation  of  acetic  acid  from  acetic 
chloride  by  the  action  of  water  : 

C2H3O.C1  -f  H.HO  ==  HC1  -f  C2H3O.HO. 

3.  C2HgO  .  H  .  0.  —  This  formula,  also  comparable  to  that  of  water,  HH  .  0, 
corresponds  to  the  conversion  of  acetic  acid  into  acetic  chloride,  hydro- 
chloric  acid,  and  phosphorus  oxychloride,  by  the  action  of  phosphorus 
pentachloride  : 

C2H30  .  H  .  0  +  PC13  .  C12  =  C2H30  .  Cl  +  HC1  -f-  PC130  ; 

also  to  the  formation  of  thiacetic  acid,  C2H30  .  H  .  S,  by  the  action  of  phos- 
phorus pentasulphide  on  acetic  acid  : 

5(C2H30  .  H  .  0)  +  P2S5  ==  5(C2H30  .  H  .  S)  +  P205. 

4.  (C2H8)/X/  .  HO  .  0.  —  This  represents  the  formation  of  acetic  acid  from 
ethenyl  nitrile,  (C2H3)///N,  by  heating  with  caustic  alkalies: 

H  =  NH   +    CH,>".  0.  HO. 


Ethenyl          Water. 
nitrile. 


CLASSIFICATION  OF  ORGANIC  COMPOUNDS.          473 

5.  (CH3  .  CO)  .  HO.  —  This  formula,  in  which  the  radical  acetyl,  C2H30, 
is  resolved  into  carbonyl,  (CO)",  and  methyl,  corresponds:  a.  To  the  de- 
composition of  acetic  acid  by  electrolysis,  in  which  hydrogen  is  evolved  at  the 
positive  pole,  while  carbon  dioxide  and  ethane,  C2H6,  appear  at  the  negative : 

2(CO .  CH3 .  HO)     =    H2    -f     C2H6    -f-     2C02. 

/?.  To  the  production  of  methane  (marsh  gas)  by  heating  potassium  ace- 
tate with  excess  of  potassium  hydrate  (p.  169) : 

CO .  CH3 .  KO     -f     HKO      =      CH4     +     (CO)" .  (K0)2. 
Potassium  acetate.     Potassium        Methane.  Potassium 

hydrate.  carbonate. 

y.  To  the  production  of  acetone  and  barium  carbonate  by  the  dry  distil- 
lation of  barium  acetate : 

(CO .  CH3)2 .  Ba02    =     (CO)"(CH3)2    -f     (CO)".Ba02. 
Barium  acetate.  Acetone.  Barium 

carbonate. 

Now,  on  comparing  those  several  rational  formulae,  it  will  be  seen  that 
they  are  all  included  under  the  constitutional  formula, 

H    0 

H— C— C— 0— H, 


A 


in  which  the  molecule  is  resolved  into  its  component  atoms,  and  these  atoms 
are  grouped,  as  far  as  possible,  according  to  their  different  equivalences,  or 
combining  powers.  These  constitutional  formulae  are  the  nearest  approach 
to  the  representation  of  the  true  constitution  of  a  compound  that  our  knowl- 
edge of  its  reactions  enables  us  to  give;  but  the  student  cannot  too  care- 
fully bear  in  mind  that  they  are  not  intended  to  represent  the  actual  ar- 
rangement of  the  atoms  in  space,  but  only,  as  it  were,  their  relative  mode 
of  combination,  showing  which  atoms  are  combined  together  directly,  and 
which  only  indirectly,  that  is,  through  the  medium  of  others.  Thus,  in  the 
formula  of  acetic  acid,  it  is  seen  that  three  of  the  hydrogen  atoms  are  united 
directly  with  the  carbon,  while  the  fourth  is  united  to  it  only  through  the 
medium  of  oxygen ;  that  one  of  the  two  oxygen  atoms  is  combined  with 
carbon  alone,  the  other  both  with  carbon  and  with  hydrogen ;  and  that  one 
of  the  carbon  atoms  is  combined  with  the  other  carbon  atom  and  with  hy- 
drogen ;  the  second  with  carbon  and  with  oxygen.  Abundant  illustration 
of  these  principles  will  be  afforded  by  the  special  descriptions  of  organic 
compounds  in  the  following  pages. 

ISOMERISM.  —  Two  compounds  are  said  to  be  isomeric  when  they  have  the 
same  empirical  formula  or  percentage  composition,  but  exhibit  different 
properties.  A  few  examples  of  isomerism  are  met  with  amongst  inorganic 
compounds ;  but  they  are  much  more  numerous  amongst  organic  or  carbon 
compounds. 

Isomeric  bodies  may  be  divided  into  two  principal  groups,  namely  : 

A.  —  Those  which  have  the  same  molecular  weight;  and  these  are  sub- 
divided into: 

a.  Isomeric  bodies,  strictly  so  called ;  namely,  those  which  exhibit  analogous 
decompositions  and  transformations  when  heated  or  subjected  to  the  action 
of  the  same  reagents,  and  differ  only  in  physical  properties.  Such  is  the 
case  with  the  volatile  oils  of  turpentine,  lemons,  juniper,  &c.,  all  of  which 
have  the  composition  C10H16,  resemble  each  other  closely  in  their  chemical 
reactions,  and  are  distinguished  chiefly  by  their  odor  and  their  action  on 
polarized  light. 
40* 


474:  HYDROCARBONS. 

/?.  Metameric  bodies,  which,  with  the  same  percentage  composition  and 
molecular  weight,  exhibit  dissimilar  transformations  under  similar  circum- 
stances. Thus  the  molecular  formula,  C3H602,  represents  three  different 
bodies,  all  exhibiting  different  modes  of  decomposition  under  the  influence 
of  caustic  alkalies,  viz.,  (1)  Propionic  acid,  C3H50  .OH,  which  is  converted 
by  caustic  potash,  at  ordinary  temperatures,  into  potassium  propionate, 
C3H60  .  OK.  —  (2)  Methyl  acetate,  C2H30  .  OCH3,  a  neutral  liquid  not  acted 
upon  by  potash  at  common  temperatures,  but  yielding,  when  heated  with 
it,  potassium  acetate  and  methyl  alcohol : 

C2H30  .  OCH3  -f  OKH  =  C2H30 .  OK  -f  CH3 .  OH. 

(3)  Ethyl  formate,  CHO .  OC2H5,  converted  in  like  manner,  by  heating 
with  potash,  into  potassium  formate,  CHO  .  OK,  and  ethyl  alcohol,  C2H5.OH. 

These  three  compounds  may  be  represented  by  the  following  constitu- 
tional formulae,  the  dotted  lines  indicating  the  division  into  radicals  indi- 
cated by  the  rational  formulae  above  given : 

H3C  •  H3C  •  H  •          H 

H2C-  0=C— 0— CH3,     0=C— 0  —  C— CH3. 

0=C— 0— H,  H 

Propionic  acid.        Methyl  acetate.         Ethyl  formate. 

B. — Compounds  which  have  the  same  percentage  composition,  but  differ 
in  molecular  weight;  such  bodies  are  called  polymeric.  The  most  striking 
example  of  polymerism  is  exhibited  by  the  hydro-carbons  CJi^,  all  of 
which  are  multiples  of  the  lowest,  namely,  methene,  CH2.  Another  exam- 
ple is  afforded  by  certain  natural  volatile  oils,  which  are  polymeric  with 
oil  of  turpentine,  and  have  the  formulae,  C20H32,  C30H48,  &c.  All  polymeric 
compounds  exhibit  regular  gradations  of  boiling  point,  vapor-density,  and 
other  physical  characters  from  the  lowest  to  the  highest.  Some  are  chemi- 
cally isomeric,  exhibiting  analogous  transformations  under  similar  circum- 
stances, while  others  are  metameric,  exhibiting  dissimilar  reactions  under 
given  circumstances. 


HYDROCARBONS. 

FIRST  SERIES,  CnII2n-(-2. — PARAFFINS.* 

This  series,  as  already  observed,  consists  of  saturated  hydrocarbons,  not 
capable  of  uniting  with  any  other  bodies,  simple  or  compound.  The  names 
and  formulae  of  the  first  six  are  given  in  the  table  on  page  467  ;  the  follow- 
ing terms  may  be  called,  septane,  octane,  nonane,  decane,  undecane,  dodecane,  &c. 

All  the  members  of  the  series  above  the  first,  CH4,  may  be  regarded  as 
derived  from  that  compound  by  replacement  of  one  of  the  hydrogen-atoms, 
by  a  univalent  hydrocarbon  radical  of  the  series  CnH^-f!  (p.  466) ;  thus . 

(H 

I     TT 

Methane  C<  H 
t-H 

*  From  parum  affmis.  indicating  their  chemical  indifference.  The  name  paraffin  has  long 
been  applied  to  the  solid  compounds  of  the  series,  on  account  of  this  character;  and  many  of 
the  liquid  compounds  of  the  same  series  are  known  commercially  as  paraffin  nils.  It  is  con- 
venient, therefore,  to  employ  the  term  paraffin  as  a  generic  name  for  the  whole  series. 


PARAFFINS.  475 


Ethane      C2H6  =  C  {  CJ[» 

Propane     C3H8  =  C  {  C^L  C  j  C%CH* 

Quartane  C4H10  =  C  {  C^  ==  C  {  cg«ciHs  =  C  {  CH,CH,CH8 


&c.,  &c. 

Occurrence  and  Formation.  —  Many  of  the  paraffins  occur  ready-formed  in 
American  petroleum  and  other  mineral  oils  of  similar  origin.  They  are 
formed  artificially  by  the  following  processes: 

1.  By  the  simultaneous  action  of  zinc  and  water  on  the  alcoholic  iodides 
(p.  468),  compounds  derived  from  these  same  hydrocarbons  by  the  substi- 
tution of  one  atom  of  iodine  for  hydrogen. 

This  reaction,  which  appears  to  be  applicable  to  the  formation  of  the 
whole  series  of  paraffins,  is  represented  by  the  general  equation  : 

2CnH2n+tI  -f  Zn2  +  20H2  =  ZnH202  -f  ZnI2  +  2CnH2n-f  2 
Alcoholic         Zinc.    Water.       Zinc  Zinc        Paraffin. 

iodide.  hydrate.      iodide. 

As  an  example,  we  may  take  the  formation  of  ethane  from  ethyl  iodide  : 

2C2H5I  -f  Zn2  -j-  OH2  =  ZnH202  +  ZnI2  -f  2C2H6 
Ethyl  Ethane. 

iodide. 

2.  All  the  paraffins  may  be  produced  by  heating  the  alcoholic  iodides 
with  zinc  alone.     Generally  speaking,  however,  two  of  these  hydrocarbons 
are  obtained  together,  the  first  product  of  the  reaction  being  a  paraffin 
containing  twice  as  many  carbon-atoms  as  the  alcoholic  iodide  employed; 
and  this  compound  being  then  partly  resolved  into  the  paraffin  containing 
half  this  number  of  carbon-atoms  and  the  corresponding  define,  (CnlLjn); 
thus: 

2C2H5I     -f     Zn     =      ZnI2     -f-     C4H10 
Ethyl  Quartane. 

iodide. 

and,  C4HIO  =     C2H4    +     C2H6 

Quartane.  Etheire.       Ethane. 

Generally  : 

2CnH2n+1I     -f     Zn      ==     ZnI2      -f-    CtoHto+i 
and,  C2BH8n+2  =     C.H*  -f    C*K*+r 

3.  By  the  electrolysis  of  the  fatty  acids  (Cn  H2n02).     For  example,  a  solu- 
tion of  potassium  acetate,  divided  into  two  parts  by  a  porous  diaphragm, 
yields  pure  hydrogen,  together  with  potash,  at  the  negative  electrode,  and 
at  the  positive  electrode  (if  of  platinum)  a  mixture  of  carbon  dioxide  and 
ethane  gases: 

F2C2H402     =     2C02     -f     C2H6     +     Hr 

We  may  suppose  that  the  two  molecules  of  acetic  acid  are  resolved  by  the 
rrent  into  H2  and  C4H604,  and  that  the  latter  then  splits  up  into  2C02  and 
H6.  The  general  reaction  is: 

SC.Hj.O,    =     2C02    +     C^H^     +     H2. 

4.  Some  of  the  paraffins  are  obtained  from  acids  of  the  series  CnH2nO2 


476  HYDROCARBONS. 

and  Cn  H2n_204,  by  the  action  of  alkalies,  which  abstract  carbon  dioxide  from 
those  acids,  the  hydrocarbon  thus  eliminated  containing  one  atom  of  carbon 
less  than  the  acid  from  which  it  is  produced : 

Cn+1H2n+202*  =       C02     +Cn    H2n+2, 
Cn+2H2n+204    ==    2C02    +Ca     H2n+2. 

In  this  maner  methane  (marsh  gas)  is  obtained  by  heating  potassium  acetate 
with  excess  of  potassium  hydrate  (p.  169) : 

C2H302K        +        OHK        =        C03K2        -f         CH3 
Potassium  Potassium  Potassium  Methane, 

acetate.  hydrate.  carbonate. 

Also,  sextane  and  octane,  by  similar  treatment  of  the  potassium  salts  of 
suberic  acid,  C8Hj404,  and  sebacic  acid,  C10HJ8O4: 

C8H1204K2  +        20HK        =        2C03K2        +         C6H,4 
Potassium  Sextane. 

suberate. 

•  C10H1604K2  +        20HK        =        2C03K2        +        C8H]8 
Potassium  Octane. 

sebate. 

Generally  speaking,  however,  a  further  decomposition  takes  place,  result- 
ing in  the  formation  of  hydrocarbons  containing  a  smaller  proportion  of 
hydrogen  than  the  paraffins. 

5.  The    paraffins   may    also   be   produced   from    the   olefines,   Cn  H2ll)  by 
combining  the  latter  with  bromine,  and  heating  the  resulting  compound, 
Cn  H2nBr2,  with  a  mixture  of  potassium  iodide,  water,  and  metallic  copper. 
The  bromine-compound  is  then  decomposed,  and  the  hydrocarbon,  CnHo,,, 
is  partly  reproduced  in  the  free  state,  partly  converted,  by  the  addition  of 
hydrogen,  into  a  paraffin,  Cn  H2n-}-2. 

6.  Several  of  the  paraffins  are  produced  by  the  dry  or  destructive  dis- 
tillation of  butyrates  and  acetates. 

7.  They  are  also  found  amongst  the  products  of  the  dry  distillation  of  coal, 
especially  Boghead  and  Cannel  coal,  and,  as  already  observed,  they  consti- 
tute the  principal  portion  of   many  mineral  oils,  formed  by  the  gradual 
decay  or  decomposition  of  vegetable  matter  beneath  the  earth's  surface. 

8.  Quintyl  alcohol,  or  amyl  alcohol,  C5H]20,  distilled  with  zinc  chloride, 
yields   quintane,    C5H12,    and    several    of    its   homologues,    together   with 
olefines  and  other  hydrocarbons  containing  still  smaller  proportions  of  hy- 
drogen. 

9.  Methane,  or  marsh  gas,  CH4,  the  first  term  of  the  series,  is  produced 
synthetically  by  passing  a  mixture  of  hydrogen   sulphide   and  vapor  of 
carbon  bisulphide  over  red-hot  copper.     The  copper  abstracts  the  sulphur 
from  both  compounds,  and  the  carbon  and  hydrogen  thus  liberated  unite  to 
form  marsh  gas  : — 

CS2    -f     2H2S     +     Cu4     =     4CuS     +     CH4. 

Properties  and  Reactions  of  the  Paraffins. — The  properties  of  methane  have 
been  already  described  (p.  169).  Of  the  other  paraffins,  ethane,  propane, 
and  quartane  are  gaseous  at  ordinary  temperatures ;  most  of  the  others 
are  liquids  regularly  increasing  in  specific  gravity,  viscidity,  boiling  point, 
and  vapor  density,  as  their  molecular  weight  becomes  greater :  those  con- 
taining 20  carbon  atoms  or  more  are  crystalline  solids.  The  following 
table  exhibits  the  specific  gravities  and  boiling  points  of  the  paraffins  ob- 
tained from  American  petroleum :  j- — 

*  By  substitution  of  n+ 1  for  n,  the  formula  Cn  H»nO2  becomes  C   +1IT2n+202;  and  by  sub- 
stitution of  n+2  for  n,  the  formula  Cn  H2n-->04  is  converted  into  C    +oll2n-fo04. 

f  Pelouze  and  Cahonrs,  Ann.  Ch.  Pharm.'cxxiv.  289;  cxxvii.  196;  cxxix.  87. 


PARAFFINS. 


477 


Specific  gravity 

Name. 

Formula. 

Boiling  point. 

of  liquid. 

of  vapor 
drogon  : 

liv- 
r  1. 

Ethane 

C2II6 

Gascons  at  ordinary 

_ 

15 

tempe 

•atures. 

Propane 

0~  HQ 

_ 

22 

Qiiiirtane 

CiHin 

a  little  above 

0° 

0-60 

at    0°C. 

32°  F. 

29 

Quintane 

C5H12 

30°  C. 

86°  F. 

0-628 

17°" 

63°" 

36 

Sextane 

CfiHii 

68°  " 

154°  " 

0-6G9 

16°" 

61°" 

43 

Septane 

C7H16 

92—94°    " 

198—201°  " 

0-699 

15°" 

69°" 

50 

. 

Octane 

116—118°  " 

241—245°  " 

0-726 

15°" 

59°" 

57 

Nonane 

Gallon 

136—138°  « 

277—280°  " 

0-741 

15°" 

59°" 

64 

Decane 

Cellos 

160—162°  " 

320—324°  " 

0-757 

,  15o  « 

59°" 

71 

TJndecane 

CnII2< 

180—184°  " 

356—363°  " 

0-765 

"  16°  " 

61°" 

78 

Duodecane 

196—200°  " 

384-392°  " 

0-776 

«  20°  " 

68°" 

85 

Tridecane 

cJjiiS 

216—218°" 

421—424°  " 

0792 

«,  20o  <« 

68°  « 

92 

Quatuordecane 

236—240°  " 

456—464°  " 



99 

Quindecane 

cfiaS 

255—260°  " 

491—500°  " 

— 

106 

American  petroleum  likewise  yields  a  quantity  of  liquid  boiling  above 
300°  C.  (572°  F.),  and  doubtless  containing  paraffins  of  still  higher  order. 
Some  specimens  of  the  crude  oil,  as  it  issues  from  the  ground,  contain 
ethane,  C2H6,  and  propane,  C3H8,  which  are  given  off  from  it  as  gas  at  or- 
dinary temperatures.  In  boring  for  the  oil  also,  large  quantities  of  gas 
escape,  exhibiting  the  characters  of  methane;  hence  it  is  probable  that  in 
the  great  geological  changes  which  have  given  rise  to  the  separation  of 
the  petroleum,  the  whole  series  of  paraffins  have  been  formed  from  marsh 
gas  upwards. 

Solid  paraffin  is  a  colorless  crystalline  fatty  substance,  probably  consist- 
ing of  a  mixture  of  several  of  the  higher  members  of  the  series  CnH2n-|-2. 
It  is  found  native  in  the  coal-measures,  and  other  bituminous  strata,  con- 
stituting the  minerals  known  as  fossil  wax,  ozocerite,  hatchettin,  &c.  It  exists 
also  in  the  state  of  solution  in  many  kinds  of  petroleum,  and  may  be  sepa- 
rated by  distilling  off  the  more  volatile  portions,  and  exposing  the  remain- 
der to  a  low  temperature.  In  a  similar  manner  also  may  solid  paraffin  be 
obtained  from  the  tar  of  wood,  coal,  and  bituminous  shale.  It  was  first 
prepared  by  Reichenbach  from  wood-tar.  It  is  tasteless  and  inodorous, 
insoluble  in  water,  slightly  soluble  in  alcohol,  freely  in  ether,  and  miscible 
in  all  proportions,  when  melted,  with  fixed  or  volatile  oils.  It  burns  with 
a  very  bright  flame,  and  those  varieties  of  it  which  melt  at  temperatures 
above  45°  C.  (113°  F. )  are  very  hard,  and  well  adapted  for  making  candles. 
Paraffin  is  largely  used  also  as  a  substitute  for  sulphur  for  dipping  matches; 
and  Dr.  Stenhouse  has  patented  its  application  to  woollen  cloths,  to  increase 
their  strength  and  make  them  waterproof.  More  extensive,  however,  are 
the  uses  of  the  liquid  compounds  of  the  paraffin  series,  known  in  commerce 
as  paraffin  oil,  photogcne,  solar  oil,  eupione,  &c.  These  oils  are  largely  used 
for  burning  in  lamps;  and,  when  mixed  with  fatty  oils,  such  as  rape  and 
cotton-seed  oils,  form  excellent  materials  for  lubricating  machinery.  For 
the  former  purpose  they  are  exceedingly  well  adapted,  as,  with  a  proper 
supply  of  air,  they  give  a  much  brighter  light  than  that  obtained  from 
fatty  oils  containing  oxygen,  and  are  much  cleaner  in  use. 

It  is  necessary  to  observe,  however,  that  natural  petroleum  and  the  oils 
obtained  by  the  dry  distillation  of  coal,  &c.,  at  low  temperatures,  are  mix- 
tures of  a  great  number  of  paraffins  differing  greatly  in  volatility,  und  that 
to  render  them  safe  for  burning  in  lamps  of  ordinary  construction,  they 
must  be  freed  by  distillation  from  the  more  volatile  members  of  the  series; 
otherwise  they  will  take  fire  too  easily,  and,  when  they  become  heated,  will 


478  HYDROCARBONS. 

give  off  highly  inflammable  vapors,  which,  mixing  with  the  air  in  the  body 
of  the  lamp,  may  easily  produce  dangerously  explosive  mixtures  ;  serious 
accidents  have  indeed  arisen  from  this  cause.  It  has  been  found  by  expe- 
rience that  it  is  not  safe  to  use  a  paraffin  oil  which  will  take  fire  on  the 
application  of  a  match  and  burn  continuously,  at  a  temperature  below  38° 
C.  (100°  F.). 

Substitution-products  of  the  Paraffins,  —  Paraffins  subjected  to  the  action  of 
bromine  or  chlorine,  give  up  a  part,  or  in  some  cases  the  whole  of  their  hy- 
drogen in  exchange  for  the  halogen  element.  Thus  equal  volumes  of 
chlorine  and  methane,  CH4,  exposed  to  diifused  daylight,  yield  the  com- 
pound CH3C1,  called  chlorornethane  or  methyl  chloride:  and.  by  further 
subjecting  this  product  to  the  action  of  an  excess  of  chlorine  in  direct  sun- 
shine, it  may  be  successively  converted  into  the  more  highly  chlorinated 
compounds  CH2C12,  CHC13,  and  CC14.  Ethane,  C2H6,  also  yields,  by  a  series 
of  processes  to  be  hereafter  described,  the  substitution-products  C2H5C1, 
C2H4C12,  C2H3C13,  C2H2C14,  C2HC15,  and  C2C16;  and  similarly  for  the  other 
compounds  of  the  series.  These  bodies,  which  may  be  regarded  as  com- 
pounds of  chlorine  and  other  halogen  elements  with  the  radicals  (CHg)', 
^CH2)",  (CH)///,  &c.,  are  called  halo'id  ethers;  the  more  important  of  them 
will  be  specially  described  in  connection  with  the  corresponding  alcohols. 
When  treated  with  water  or  aqueous  alkalies,  they  exchange  the  haloid 
element  for  an  equivalent  quantity  of  hydroxyl,  (HO),  thereby  producing 
alcohols  (p.  468)  ;  and,  on  the  other  hand,  they  may  be  formed  from  the 
alcohols  by  the  action  of  the  chlorides,  bromides,  and  iodides  of  hydrogen 
or  phosphorus. 

Nitric  acid  attacks  the  higher  members  of  the  paraffin  series,  forming 
nitro-compounds  ;  octane,  C8H,8,  thus  treated,  yields  the  compound,  C8H1T 
(N02).  The  lower  paraffins,  on  the  other  hand,  are  not  aft'ected  in  the 
slightest  degree  by  nitric  acid;  but  by  indirect  means  compounds  may  be 
formed,  having  the  composition  of  paraffins,  in  which  the  hydrogen  is 
more  or  less  replaced  by  nitryl  ;  for  example,  trinitromethane  or  nilroform, 
CH(N02)3. 

Isomerism  in  the  Paraffin  series.  —  It  has  already  been  mentioned  that  these 
hydrocarbons  are  sometimes  regarded  as  hydrates  of  the  univalent  alcohol 
radicals  CnH2n+,,  —  methane,  for  example,  as  methylhydride,  H  .  CH3, 
ethane  as  ethyl  hydride,  H  .  C2H5.  This  view  of  their  constitution  is  sug- 
gested by  their  formation  by  the  action  of  water  on  the  zinc  compounds  of 
the  same  radicals  ;  e.  g.  : 

Zn(CH3)2      -f      20H2      =      ZnH202      -f      2(H.CH3); 
Zinc  methyl.  Water.        Zinc  hydrate.      Methyl  hydride. 

and  by  the  facility  with  which  they  give  up  one  atom  of  hydrogen  in  ex- 
change for  chlorine  and  bromine,  whereas  the  replacement  of  the  remain- 
ing hydrogen-atoms  is  much  more  difficult.  On  the  other  hand,  all  these 
hydrocarbons,  except  methane,  may  be  regarded  as  compounds  of  two 
equivalents  or  half-molecules  of  alcohol  radicals  C^H^-f-j,  thus  : 


C2H6            =            H.C2H6            or  CH3  .  CH3, 

Ethane.                    Ethyl  hydride.  Dimethyl. 

C3H8            =            H.C3Hr            or  CH3  .  C2H5, 

Propane.                 Propyl  hydride.  Methyl-ethyl. 

C4H,0      =      H  .  C4H9      or      C2H6  .  C2H6      or      CH3  .  C3H7, 

Quartane.             Quartyl                   Diethyl.  Methyl- 

hydride  propyl. 
This  latter  view  appears  to  accord  with  their  formation  by  the  action  of 


PARAFFINS.  479 

zinc  on  the  iodides  of  the  alcohol  radicals,  which  is  similar  to  that  of  hydro- 
gen by  the  action  of  zinc  on  hydriodic  acid  ;  thus  : 

Zn          +          2HI  ZnI2          -f          HH, 

Hydrogen  Zinc  iodide.  Hydrogen. 

iodide. 

Zn         -f-         2C2H6I        =          ZnI2         +          C2H5  .  C2H5 
Ethyl  iodide.  Diethyl. 

Zn      -f-      CH3I      -f      C2H5I      =      ZnI2      -f      CH3.C2H5, 
Methyl  Ethyl  Methyl- 

iodide.  iodide.  ethyl. 

The  first  three  hydrocarbons  of  the  series,  however,  viz.,  CH4,  C2H6,  C3Hg, 
exhibit  exactly  the  same  physical  and  chemical  properties  in  whatever  way 
they  may  be  prepared;  and  indeed  the  constitutional  formulae  of  these 
bodies,  viz. 

CH3 


CH4 


CH 

CH2 


show  that  they  are  not  susceptible  of  isomeric  modification,  inasmuch  as 
there  is  but  one  way  in  which  the  carbon-atoms  in  either  of  them  can  be 
grouped  :  in  ethane  each  carbon-atom  is  directly  combined  with  three  hy- 
drogen-atoms and  the  other  carbon-atom ;  and  whether  we  regard  it  as 
CH3 

ethyl  hydride,  H — CH2,  or  as  dimethyl,  H3C — CH3,  this  arrangement  re- 
mains the  same.  In  propane,  C3H8,  each  carbon-atom  is  directly  combined 
with  at  most  two  other  carbon-atoms,  and  there  is  no  other  way  in  which 
the  atoms  can  be  arranged. 

But  if  we  look  at  the  formula  of  the  4-carbon  paraffin,  C4H10,  we  see  that 
it  may  be  written  in  either  of  the  following  forms : 

CH3  " n     nTT 


CH 

CH2  f 

I  CH5 

CH3 


in  the  first  of  which,  neither  of  the  carbon-atoms  is  directly  united  with 
more  than  two  others,  whereas  in  the  third,  one  of  the  carbon-atoms  is 
directly  combined  with  three  others.  The  first  may  be  represented,  either 
as  propyl-methane,  C  j  £H2CH2CH3  =  c  f  GH2CaH6  =  c  f  C8H7  Qr  ftg  ^_ 

I  -"3  I  "3  t  H3 

thyl,  H5C2 .  C2H6,  according  to  the  manner  in  which  we  may  suppose  it  to 
be  divided;  the  second  as  trimethyl  methane,  C  <Mjr  ,  or  isopropyl  methane, 

^    i  H  »  *^e  radical  CH(CH3)2  being  called  isopropyl,  to  distinguish 

it  from  normal  propyl,  CH2(C2H6). 

From  recent  observations  *  it  appears  that  all  hydrocarbons  of  known 
structure  may  be  divided  into  four  groups,  viz. :  1.  Those  in  which  each 
carbon-atom  is  directly  associated  with  at  most  two  other  carbon-atoms. 
2.  Those  in  which  one  carbon-atom  is  associated  with  three  carbon-atoms, 

*  Schorlemmer,  Proceedings  of  the  Royal  Society,  xvi.  34,  367. 


480 


HYDROCARBONS. 


or  which  contain  the  group  isopropyl  once.   3.  Those  which  contain  this  group 

twice,  such  as  di-isopropyl,  or  tetramethyl-ethane,  CflH14  —  C2|  u}ru3{2> 

I  "v^n8/a 

produced  by  the  action  of  zinc  on  isopropyl  iodide  ;  this  compound  may  be 
represented  by  the  constitutional  formula  : 

H      H 

-  C  — 


4.  Those  in  which  one  carbon-atom  is  associated  with  four  others,  as  in 

f  /T'H  ^ 
dimethyl-diethyl-methane,  or  carbdimethyl-diethyl,  C  j  >c  J'?  ,  a  compound 

produced  by  the  action  of  zinc-ethyl,  Zn(C2H5)2,  on  dimethyl-dichlorome- 


thane,  C 


(CH3)2 


the  transformation  being  effected  by  the  substitution  of 


2  atoms  of  ethyl  for  2  atoms  of  chlorine : 

Dimethyl-dichloro-methane.  Dimethyl-diethyl-methane. 


CH 


Cl 


H3C— C— CH3 


i 


|H 

H3C— C— CHS 


C 


Hfl 


The  paraffins  of  each  of  these  groups  exhibit  a  regular  increase  in  boil- 
ing point  as  they  ascend  in  the  series  by  successive  addition  of  CH2,  and 
the  boiling  point  of  a  paraffin  containing  a  given  number  of  carbon-atoms, 
is  found  to  be  lower  in  proportion  as  its  structure  is  more  complex.  In 
the  first  and  second  groups  the  difference  of  boiling  point,  for  each  incre- 
ment of  CH2,  is  about  31°  C.  (56°  F.),  whereas  in  the  third  it  is  only  25° 
C.  (45°  F.). 


SECOND  SERIES,  CnHjn- — OLEFINES. 

The  hydrocarbons  of  this  series  are  polymeric,  as  well  as  homologous 
with  one  another,  inasmuch  as  their  formulae  are  all  exact  multiples  of 
that  of  the  lowest  CH2.  The  lower  members  of  the  series  are  gaseous  at 
ordinary  temperatures,  the  higher  members  are  solid,  and  the  intermediate 
compounds  liquid.  The  names  and  formulae  of  the  known  members  of 
the  olefine  series  are  given  in  the  following  table,  together  with  their 
melting  and  boiling  points: 


Name. 

Formula. 

Melting  point. 

Boiling  point. 

Ethene             or 

Ethylene 

C2H4 

_ 

_ 

Propene 
Quartene            " 

Propylene 
Butylene 

~ 

—17-8°      C.      14°         F. 
+3°         "       37-4 

Quintene 

Arnylene 

C^HIO 

— 

35°         "        95 

Sextene 

llexylene 

C6II12 

— 

68-70°   "      154-158 

Septene 
Octene 

Ilcptylene 
Octylene 

C7Ul4 
P8Hl6 

— 

95°          "      203° 
115-117°  "      239-242° 

Noneno 

Nonylene 

._. 

140°          "      284° 

Decene 

Paramylene 

Plo"i20 

__ 

1CO°          "      320° 

jSexdecene 

Cetene 

CjiHoo 



275°         $'      527° 

Beptivigintine  " 
Trigintene         " 

Cerotene 
Melene 

C27!!5* 

57°  C.    135°  F. 
62°  "     144°  " 

(?)                    (?) 
375°  (?)    i      707°  (?)    " 

OLEFINES.  481 

Methene,  CII2,  the  lowest  term  of  the  series,  does  not  appear  to  be  ca- 
pable of  existing  in  the  separate  state ;  but  its  oxygen  analogue,  carbon 
monoxide  or  carbonyl,  CO,  is  a  well-known  compound,  which  has  been  al- 
reudy  described  (p.  168). 

Formation  of  the  Olefines.  —  1.  By  abstraction  of  the  elements  of  water 
from  the  alcohols  of  the  series  CnH2n  -}_2O,  homologous  with  common  alcohol, 
under  the  influence  of  powerful  dehydrating  agents,  such  as  oil  of  vitriol, 
phosphoric  oxide,  or  zinc  chloride;  thus: 

C2H60      —      OH2      =      C2H4 
Ethyl  alcohol.        Water.  Ethene. 

The  preparation  of  ethene,  or  olefiant  gas,  by  heating  common  alcohol 
with  oil  of  vitriol,  has  been  already  described  (p.  1G9).  Quintyl,  or  amyl 
alcohol,  C5H120,  distilled  with  zinc  chloride,  yields  —  besides  the  corre- 
sponding oletiiie,  quintene  or  amylene,  C6H,0  —  a  number  of  others  poly- 
meric with  it;  besides  quintane,  C5H,2,  and  its  homologues,  and  hydrocar- 
bons containing  a  smaller  proportion  of  hydrogens  than  the  olefines. 

2.  By  passing  the  vapors  of  the  haloid  compounds  of  the  monad  radicals, 
CnH2n  -j-i,  over  lime  at  a  dull  red  heat;  e.g.  : 

2C6HUC1     -f     CaO     =    CaCl2    -f     OH2    +     2C5HJO 
Quintyl  Lime.         Calcium        Water.       Quintene. 

chloride.  chloride. 

3.  By  the  decomposition  of  the  paraffins  at  the  moment  of  their  forma- 
tion by  the  action  of  zinc  or  sodium  on  the  alcoholic  iodides  of  the  monad 
alcohol-radicals  Cn  H.^  +j  (see  p.  475). 

4.  By  the  action  of  these  same  iodides  on  the  sodium  compounds  of  the 
same  radicals ;  for  example : 

C2H5I       +       C2H5Na      =      Nal       +       C2H4      +      C2H6 
Ethyl  Sodium  Sodium          Ethene.  Ethane, 

iodide.  ethyl.  iodide. 

5.  By  decomposition  of  the  hydrates  of  ammonium  bases  containing  four 
atoms  of  a  monad  alcohol-radical  (p.  471),  these  compounds  when  heated 
splitting  up  into  a  tertiary  monamine  (p.  470)  and  an  olefine;  thus: 

N(C2H5)4(HO)     =     N(C2H5)3     +      OH2     +     C2H4 
Tetrethylammo-          Triethyl-  Water.         Ethene. 

nium  hydrate.  ammine. 

6.  Olefines  are  formed  by  the  decomposition  of  acetates  and  butyrates 
at  a  red  heat,  distilling   over   together  with   several   other  products,  from 
which  they  are  separated  by  combining  them  with  bromine,  and  heating 
the  resulting  bromine-compounds,  CnH2nBr2,  to  275°  C.  (527°  F.),  with  cop- 
per, water,  and  potassium  iodide.     In  this  manner  Berthelot  has  obtained 
ethene,  propene,  quartene,  and  quintene. 

7.  Several  of  the  olefines  may  be  produced  by  direct  synthesis  from  other 
hydrocarbons  of  simpler  constitution. 

a.  Ethene  is  formed  by  the  action  of  nascent  hydrogen  upon  ethine  or 
acetylene  (p.  484) : 

C2H2    +     H2    =    C2H4 
Ethine.  Ethene. 

/?.  Propene,  C3H6,  is  formed  by  passing  a  mixture  of  methane  and  carbon 
monoxide  (oxymethene)  through  a  red-hot  tube  : 

2CH4         +         CO         =         OII2        +         C3IIfl. 

Also  by  the  action  of  methenyl  chloride  (chloroform)  on  zinc  ethide : 
41 


482  HYDROCARBONS. 

2CHC13        +  3Zn(C2H6)2  =  3ZnCl2  +  4C3H6  -f  2CH4. 

y.  Quintene,  or  amylene,  C5H,0,  or  a  compound  isomeric  with  it,  is  formed 
by  the  action  of  zinc  ethide  on  propenyl  (allyl)  iodide : 

2C3H5I         +     Zn(C2H5)2  =  Znl  +     2C5H10. 

6.  Sextene,  or  hexylene,  C6H12,  is  obtained  in  combination  with  hydriodic 
acid  by  the  action  of  that  acid  on  mannite,  which  is  a  sugar  having  the 
composition  of  a  hexatomic  alcohol: 

C6H8(HO)6  +  11HI  =  60H2  +  5I2  +  C6H12  .  HI; 

Mannite.  Sextene 

hydriodide. 

and  this  hydriodide,  heated  with  potassium  hydrate,  yields  the  hydro- 
carbon : 

C6H,2 .  HI  +        OKH      =    KI         -f     OH2  +  C6H,2. 

e.  Quartene,  or  butylene,  C4H8,  is  obtained  by  precisely  similar  reactions 
from  erythrite,  which  is  also  a  saccharine  substance  having  the  composition 
of  a  tetratomic  alcohol,  C4H6(HC)4. 

Reactions. — 1.  The  olefines  are  dyad  radicals,  uniting  with  2  atoms  of 
chlorine,  bromine,  &c.,  and  with  one  atom  of  oxygen. 

2.  The  chlorides,  bromides,  and  other  haloid  compounds  of  the  olefines, 
treated  with  an  alcoholic  solution  of  potash,  give  up  one  atom  of  hydrogen 
and  one  atom  of  the  haloid  element,  yielding  an  olefine  in  which  one  atom 
of  hydrogen  is  replaced  by  chlorine,  bromine,  &c.,  together  with  water 
and  a  haloid  salt  of  potassium  ;  thus : 

C2H4Br2  -j-  OKH  =  KBr  -f  OH2  -f  C2H3Br. 
Ethene  bromide.  Bromethene. 

The  resulting  chlorinated,  brominated,  or  iodated  compound  can,  in  its 
turn,  take  up  2  atoms  of  chlorine,  bromine,  or  iodine,  forming  a  body  which 
can  likewise  give  up  hydrochloric,  hydrobromic,  or  hydriodic  acid,  under 
the  influence  of  alcoholic  potash ;  the  body  thus  formed  can  again  take  up 
2  atoms  of  chlorine,  bromine,  or  iodine ;  then  give  up  HC1,  HBr,  or  HI ; 
and  thus,  by  a  series  of  perfectly  similar  reactions,  we  at  length  arrive  at 
bodies  consisting  of  the  primitive  olefine  with  all  its  hydrogen  replaced  by 
chlorine,  bromine,  or  iodine,  and  the  dichlorides,  dibromides,  and  di-iodides 
of  these  last-mentioned  bodies :  thus,  from  ethene  may  be  derived  the  two 
following  series  of  brominated  compounds : — 


Ethene  ....  C2H4 
Bromethene  .  .  C2H31 
Dibromethene  .  C0H0Br, 


Ethene  bromide     ....  C2H4Br2 

Bromethene  bromide 

Dibromethene  bromide  .     .  C2H2Br2  .  Br2 


Tribromethene     .  C2HBr3    I  Tribromethene  bromide      .  C2HBr3   .  Br2 
Tetrabromethene    C2Br4       |  Tetrabromethene  bromide  .   C2Br4       .  Br2 

These  compounds  will  be  more  particularly  described  in  connection  with 
the  corresponding  alcohols. 

3.  A  monochlorinated  or  monobrominated  olefine  may  give  up  the  atom 
of  chlorine  or  bromine  which  it  contains,  in  the  form  of  hydrochloric  or 
hydrobromic  acid,  whereby  it  is  reduced  to  a  hydrocarbon  of  the  following 
series,  CnH2n_2.  This  reaction  may  take  place  at  130° — 150°  C.  (266°— 
302  F.),  under  the  influence  of  alcoholic  potash,  or,  better,  of  sodium  ethyl- 
ate  (obtained  by  dissolving  sodium  in  anhydrous  alcohol);  thus: 

C2H3Br  -f  C2H5NaO  =r  NaBr  +  C2H5(HO)  -f  C2H2. 
Bromethene.     Sodium       Sodium         Ethyl          Ethine. 
§thylate.     bromide,      alcohol. 


OLEFINES.  483 

4.  Ethene  bromide  and  its  homologues,  treated  with  silver  acetate  or 
potassium  acetate,  exchange  their  bromine  for  an  equivalent  quantity  of 
the  halogenic  residue  of  the  acetate,  C2H302   (p.   472),   giving  rise  to  di- 
atomic acetic  ethers;  thus: 

(C,H4)"Brs  +  2C2H302K  ==  2KBr  +  (C2H4)"(C2H302)2; 
Ethene  Potassium  Potassium  Ethene 

bromide.'  acetate.      bromide.  diacetate. 

and  these  ethers,  distilled  with  a  caustic  alkali,  yield  diatomic  alcohols  or 
glycols;  for  example: 

(C2H4)")C2H302)2  +  20HK  =  2C2H302K  +  (C2H4)^(OH)2. 

Ethene  Potassium  Ethene 

diacetate.  acetate.  alcohol. 

5.  The  bromides,  CnH2nBr2,  heated  to  275°  C.  (527°  F.)  with  a  mixture  of 
potassium  iodide,  copper,  and  water,  give  up  their  bromine  and  reproduce 
the  original  olefine,  together  with  other  hydrocarbons  (p.  476). 

6.  Some  olefines,  when  briskly  shaken  up  with  strong  snlphuric  acid, 
unite  with  it,  forming  acid  ethers  of  sulphuric    acid,  which  contain  the 
monatomic  alcoholic  radicals  corresponding  to  the  olefines;  thus: 

C2H4         -f         S04H2         =         S04.C2H5.H; 
Ethene.  Sulphuric  acid.       Ethyl-sulphuric  acid. 

and  these  acid  ethers  distilled  with  water  reproduce  sulphuric  acid,  and 
the  monatomic  alcohol  corresponding  to  the  olefine  : 

S04.C2H5H  -f         H(OH)     =     S04H2         +         C2H5(OH). 

Ethyl-sulphuric  acid.  Water.  Ethyl  alcohol. 

With  fuming  sulphuric  acid  (which  contains  sulphuric  oxide  in  solution) 
the  olefines  yield  sulpho-acids  which  are  isomeric  with  the  preceding,  but 
are  not  decomposed  by  water,  with  formation  of  an  alcohol. 

7.  Olefines  unite  with  hydrochloric,  hydrobromic,  and  hydriodic  acids; 
and  the  resulting  compounds  treated  with  silver  oxide  in  presence  of  water, 
give  rise  to  two  different  reactions  which  go  on  simultaneously,  one  part 
of  the  compound  exchanging  its  halogen  element  for  hydroxyl,  and  thereby 
producing  an  alcohol,   while  another  portion  gives  up  hydrochloric,  hy- 
drobromic, or  hydriodic  acid,  reproducing  the  original  olefine: 

2(C6H12.HI)     +  OAg2    -f     OH2     =     2AgI     +     2C6HI40 

Hexylene  Hexyl 

hydriodide.  alcohol. 

2(C6H6.HI)      -f  OAg2     =     2AgI    +     OH,,     +      2C6H6. 

Hexyleue  hydriodide.  Hexylene. 

The  greater  number  of  the  olefines  are  not  of  sufficient  importance  to 
require  special  description  in  this  work.  Ethene  has  been  already  de- 
scribed (p.  170).  Quintene,  or  amylene,  and  a  few  others  will  be  noticed 
in  connection  with  the  corresponding  alcohols. 

Isomerism  in  the  Olefine  series. — From  theoretical  considerations,  it  might 
be  expected  that  each  member  of  the  olefine  series  would  exist  in  two 
isomeric  modifications,  the  one  being  a  dyad  radical,  and  the  other  a  satu- 
rated  hydrocarbon;  the  compound  C2H4,  for  example,  might  exhibit  the  two 
modifications  represented  below: 

— CH2  CH2 

— CH2  CH2 

Dyadic.  Saturated. 


484  HYDROCARBONS. 

But  the  dyadic  members  of  the  series  are  the  only  ones  actually  known. 
These,  however,  exhibit  in  some  of  their  compounds  a  different  kind  of 
isomerism,  which  does  not  affect  their  equivalent  value. 

a.   The  dichlorides  of  the  defines  are  isomeric  with  the  monochlorinated 
chlorides  of  the  monad  alcohol  radicals,  CnH-ja+j;  for  example: 


CH2CH  f  CH3 

I  is  isomeric  with     J    | 
CH2C1  J  (  CHC12 

Ethene  Monochlorinated 

dichloride.  ethyl  chloride. 

Both  these  compounds2  when  treated  with  alcoholic  potash,  yield  the  same 
product,  namely,  vinyl  chloride,  C2H3C1  ;  but  they  differ  in  boiling  point, 
the  first  boiling  at  85°  C.  (185°  F.),  the  second  at  64°  C.  (147°  F.) 

/?.  The  oxides  of  the  olefines  are  isomeric  with  the  corresponding  alde- 
hydes, and  with  the  alcohols  of  the  series  CnH^n^OH 

CH,  CHS  OH, 

^  CH2  COH  CHOH 

Ethene  oxide.        Acetic  aldehyde.     Vinyl  alcohol. 

The  dyad  radical,  called  ethidene,  or  ethylidene,  which  may  be  supposed  to 
exist  in  aldehyde  and  in  monochlorinated  ethyl  chloride,  has  not  been  iso- 
lated :  it  probably  differs  from  ethene  in  the  manner  shown  by  the  follow- 
ing formulae  : 


— CH2 
— CH2 


CH 


Ethene.  Ethidene. 

Similar  instances  of  isomerism  are  observed  in  the  compounds  of  tho 
other  members  of  the  olefine  series. 


THIRD  SERIES,  CaU2a_y 

Of  these  hydrocarbons  five  only  have  as  yet  been  prepared,  viz. : 

Ethine     or  Acetylene,  C2H2 

Propine  "  Allylene,  C3H4 

Quartine "  Crotonylene,  C4H6 

Quintine  "  Valerylene,  C5H8 

Sextine    "  Diallyl,  C6H,0. 

The  only  general  method  of  preparing  these  bodies  consists  in  heating 
_ie   monobrominated  derivatives  of  the 
ethylate  to  130°-150°  C.  (266°-302°  F.): 

CnH^Br    -f     C2H5NaO     =     NaBr     -f     C2H5(HO)     +     C^H^. 
Sodium  Ethyl  alcohol, 

ethylate. 

Ethine  and  propine,  which  are  gaseous  at  ordinary  temperatures,  are  sepa- 
rated from  the  alcohol  vapor  with  which  they  are  mixed,  by  passing  the 
gas  into  an  ammoniacal  solution  of  cuprous  chloride,  whereby  an  explosive 
compound  is  precipitated,  containing  copper,  carbon,  hydrogen,  and 


ETHINE,    OR    ACETYLENE.  485 

oxygen ;  and  this  precipitate,  treated  with  hydrochloric  acid,  yields  the 
hydrocarbon  in  the  pure  state. 

The  other  hydrocarbons  of  the  series,  which  are  liquid,  do  not  form  any 
precipitate  with  ammoniacal  cuprous  chloride;  but  they  may  be  separated 
from  excess  of  alcohol  by  addition  of  water,  and  further  purified  by  dis- 
tillation. 

The  hydrocarbons  of  this  series  should  exhibit  three  isomeric  modifica- 
tions :  saturated,  dyadic,  and  tetradic,  according  to  the  manner  in  which  the 
carbon  atoms  are  united;  thus,  for  the  compound  C2H2 : 

C— H  — C— H  — C— H 

C_H  — C— H  — C— H 

Saturated.  Dyadic.  Tetradic. 

The  actually  known  compounds  are,  however,  all  tetradic,  being  capable 
of  uniting  with  four  atoms  of  chlorine,  bromine,  and  other  monad  elements, 
though  they  can  also  form  half-saturated  compounds  containing  only  2 
atoms  of  a  monad  element. 

When  agitated  with  hydrobromic  or  hydriodic  acid,  they  take  up  one  or 
two  molecules  of  these  acids.  The  dihydrobromides  and  dihydriodides 
thus  produced  have  the  same  composition  as  the  dibrominated  derivatives 
of  the  olefine  series;  thus: 

Cn  Ha,—., .  2HBr     =     Cn  H^Br^ 
The  two  classes  of  bodies  are,  however,  isomeric,  not  identical. 

Ethine,  or  Acetylene,  C2H2. — This  hydrocarbon  is  one  of  the  constituents 
of  coal  gas.  It  is  produced: — 1.  By  synthesis  from  its  elements.  When 
an  electric  arc  from  a  powerful  voltaic  battery  passes  between  carbon  poles 
in  an  atmosphere  of  hydrogen,  the  carbon  and  hydrogen  unite  in  the  pro- 
portion to  form  ethine. 

2.  By  the  action  of  heat  upon  ethene,  or  the  vapor  of  alcohol,  ether,  or 
wood-spirit,  or  by  passing  induction-sparks  through  marsh-gas. 

3.  By  passing  the  vapor  of  chloroform  over  ignited  copper: 

2CHC13    -f     Cu6     =     3Cu2Cl2    -f     C2H2. 

4.  By  the  incomplete  combustion  of  bodies  containing  carbon  and  hy- 
drogen :  for  example : 

4CH4  -f  06  =  60H2  -f  2C2H2 
Methane.  Ethine. 

2C2H4  -f  0,  =  20  H2  -1-  2C2H2 
Ethene.  Ethine. 

5.  By  passing  a  mixture  of  marsh-gas  and  carbon  monoxide  through  a 
red-hot  tube: 

CH4     +     CO     =     OH2     +     C2H2. 

6.  By  the  action  of  alcohol  potash  on  monobromethene : 

C2H3Br     -f     OHK     =     KBr     -f     OH2     -f     C2H2. 

The  crude  ethine  obtained  by  either  of  these  processes  is  purified  in  the 
manner  above  mentioned. 

Ethine  is  a  colorless  gas  of  specific  gravity  0-92,  having  a  peculiar  and  un- 
pleasant odor,  moderately  soluble  in  water,  not  condensed  by  cold  or  pres- 
sure.    It  burns  with  a  very  bright  and  smoky  flame,  one  volume  of  the  gas 
41* 


486  HYDROCARBONS. 

consuming  2£  volumes  of  oxygen  and  producing  2  volumes  of  carbon 
dioxide.  When  mixed  with  chlorine,  it  detonates  almost  instantly,  even  in 
diffused  daylight,  with  separation  of  carbon. 

Ethine  passed  into  an  ammoniacal  solution  of  cuprous  chloride  forms  a  red 
precipitate  consisting  of  cuproso-vinyl  oxide,  C4Cux4H20,  or  (C2Cu/2H)20,  that 
is  to  say,  vinyl-oxide  (C2H3)20,  having  four  of  its  hydrogen-atoms  re- 
placed by  four  atoms  of  apparently  univalent  copper.*  The  constitution 
of  this  compound  may  be  understood  from  the  following  formulae : 

H     H          H     H  H          H 

c=c— o— c=c  |U^>c=c— o— c=c<T"  |U 

i       J 

Vinyl  oxide.  Cuproso-vinyl  oxide. 

Its  formation  from  cuprous  chloride  and  ethine  is  represented  by  the  equa- 
tion: 

2Cu'2Cl2     -f     2C2H2    -f-     OH2    =    4HC1     -f    C4Cu'4HaO. 

On  heating  it  with  hydrochloric  acid,  the  opposite  reaction  takes  place, 
cuprous  chloride  and  water  being  reproduced,  and  pure  ethine  evolved 
as  gas. 

When  this  copper  compound  is  heated  with  zinc  and  dilute  ammonia,  the 
nascent  hydrogen  thereby  evolved  unites  with  the  elements  of  ethine,  pro- 
ducing ethene : 

C4Cu4H20     -j-     2H2,    =    Cu4     -f-     OH2     -f     2C2H2, 
and  C2H2          -f-       H2    =.-    C2H4. 

Ethine,  briskly  agitated  with  strong  sulphuric  acid,  is  absorbed,  producing 
vinyl-sulphuric  acid,  C2H4S04 : 

C2H2     -f     S04H2    =     S04(C2H3)H; 

and  this  acid,  distilled  with  water,  is  resolved  into  sulphuric  acid  and  vinyl 
alcohol : 

S04(C2H3)H     +     OH2    =     S04H2     +     C2H3(OH) 
Vinyl-sulphuric  Vinyl 

acid.  alcohol. 

Ethine  unites  with  bromine,  forming  a  dibromide,  C2H2Br2. 

Bromethine,  or  Bromacetylene,  C2HBr,  is  produced  by  the  action  of  alcoholic 
potash  on  dibromethene  dibromide  : 

C2H2Br2.Br2    =     HBr     -f     Br2     -f     C2HBr. 

It  is  a  spontaneously  inflammable  gas,  which  liquefies  under  a  pressure 
of  three  atmospheres,  is  soluble  in  water,  and  very  soluble  in  dibromethene. 
It  unites  with  bromine,  forming  the  compound,  C2HBr .  Br2.  and  when 
passed  into  an  ammoniacal  solution  of  cuprous  chloride,  yields  a  precipi- 
tate of  cuproso-vinyl  oxide. 

Propine,  or  Allylene,  C3H4. — This  compound  is  produced  by  the  action  of 
sodium  ethylate  on  bromopropene : 

C3H5Br     +     C2H5NaO     =     NaBr    -f    C2TT5(HO)     +     C3TI4 
Bromo-  Sodium  Ethyl  alcohol        Propine 

propene  ethylate 

*  See  page  354. 


QUARTINE  —  QUINTINE  —  SEXTINE. 


487 


its  formation  being  a  particular  case  of  the  general  reaction  given  on  page 
484.  It  is  a  colorless  gas,  having  an  unpleasant  odor,  burning  with  a 
smoky  flame,  and  forming,  with  mercurous  salts,  a  gray  precipitate  ;  with 
silver  salts,  a  white  precipitate  ;  and  with  cuprous  chloride  a  yellow  pre- 
cipitate analogous  in  composition  to  that  formed  by  ethine.  With  bromine 
it  forms  the  compounds  C3H4Br2,  and  C3H4Br4. 

Quartine,  or  Crotonylene,  C4H6.  —  Produced  by  the  action  of  sodium  ethyl- 
ate  on  bromoquartene.  It  is  liquid  below  15°  C.  (5U°  F.),  but  volatilizes 
very  quickly  if  not  cooled  by  ice.  It  has  a  very  strong,  somewhat  allia- 
ceous odor,  boils  at  about  18°  C.  (64°  F.),  and  distils  between  18°  and  24° 
C.  (75°  F.).  Bromine  dropped  into  this  liquid,  cooled  by  a  freezing  mixture, 
yields  dibromoquartine,  C4H6Br2,  a  liquid  heavier  than  water,  and  distilling, 
with  partial  decomposition,  between  148°  and  158°  C.  (298°-316°  F.). 
This  dibromide,  left  in  contact  for  some  days  with  excess  of  bromine,  is 
converted  into  the  tetrabromide,  C4H6Br4,  a  crystalline  solid,  isomeric  with 
dibromo-quartene  dibromide,  C4H6Br2 .  Br2. 

Quintine,  or  Valerylene,  C5H8,  is  obtained  by  heating  quintene  bromide 
with  alcoholic  potash  (which  abstracts  hydrobromic  acid),  distilling  the 
liquid  separated  from  the  product  by  water,  and  collecting  that  which  passes 
over  between  44°  and  46°  C.  (111°-115°  F.) : 

C5H,0Br2    •   •    2HBr     =     C6H8. 

Quintine  is  a  colorless,  very  mobile  liquid,  which  floats  on  water,  and  is 
.nearly  insoluble  therein.  It  has  a  pungent  alliaceous  odor,  boils  at  44°  to 
46°,  and  has  a  vapor-density  of  2-356;  it  is  not  absorbed  by  ammoniacal 
cuprous  chloride. 

Quintine  forms  two  series  of  compounds :  tjie  one  composed  of  incomplete 
bodies  still  capable  of  fixing  two  atoms  of  chlorine,  bromine,  or  other  monad 
element,  or  one  molecule  of  hydrobromic  or  hydrochloric  acid;  the  other 
composed  of  saturated  bodies : 

Dyadic. 

Dibromide        .         .     C5H8Br2 
Monohydrobromide      C6H8.HBr 

Monohydrochloride      C5H8 .  HC1 
Monohydriodide      .     C6H8 .  Ill 

Monoacetate    .         .     C61 
Monohydrate  .         .     C5I 


Saturated. 


C5HBr4. 


HBr.Brfl 


2H302)2 


Tetrabromide 
Dibrorno-hydro- 

bromide 
Dihydrobromide 
Dihydrochloride 

Diacetate 
Dihydrate 

The  bromides,  hydrobromides,  hydrochlorides,  and  hydriodides  are 
formed  by  direct  combination ;  the  acetates  by  heating  the  dihydrobromide 
in  sealed  tubes  with  silver  acetate  suspended  in  ether;  the  hydrates  by 
treating  the  corresponding  acetates  with  solid  potash.  These  compounds 
are  all  liquid  at  ordinary  temperatures.  The  dibromide,  treated  with  pot- 
ash in  alcoholic  solution,  is  converted,  by  abstraction  of  hydrobromic  acid, 
into  quintone,  or  valylenc,  C5H6  (=  C5H8Br2 — 2IIBr). 

Sextine,  or  Diallyl,  C6H,0,  is  produced:  1.  By  decomposing  allyl  iodide, 
C3H5I,  with  an  alloy  of  tin  and  sodium.  2.  Together  with  many  other  pro- 
ducts by  heating  allyl  iodide  in  sealed  tubes  with  zinc  ethide.  It  is  a  liquid 
which  boils  at  58°  C.  (136°  F.),  and  forms  two  series  of  compounds,  one 
saturated,  the  other  dyadic,  analogous  to  those  of  quintine,  and  obtained  by 
similar  processes.* 


*  A.  Wurtz,  Ann.  Chim.  Phys.  [4],  iii.  129.  —  Jahresbericht  fur  Chemie,  1864,  p.  210. 


488  HYDROCARBONS. 


FOURTH  SERIES,  CnH2n_4. 

The  known  hydrocarbons  of  this  series  are  quintone,  or  valylene,  C6H6, 
produced  by  abstraction  of  hydrogen  from  quintine,  C5H8;  and  certain 
volatile  oils  called  terpenes,  having  the  composition  C10H16.  and  existing 
ready-formed  in  plants.  The  former  is  sexvalent  and  quadrivalent ;  the 
latter  are  quadrivalent  and  bivalent. 

Quintone,  or  Valylene,  C6H6,  is  formed,  as  already  observed,  by  the  action 
of  alcoholic  potash  on  quintine  dibromide,  C5H8Br2,  and  passes  over,  to- 
gether with  a  little  quintine,  between  45°  and  50°  C.  (113°-122°  F.).  It 
may  be  obtained  pure  by  treating  the  mixture  with  ammoniacal  cuprous 
chloride,  which  precipitates  the  quintone,  but  not  the  quintine;  and  on 
warming  the  precipitate  with  dilute  hydrochloric  acid,  the  quintine  passes 
over,  and  may  be  condensed  by  a  freezing  mixture.  It  is  a  light  liquid, 
boiling  at  about  50°  C.  (122°  F.)  With  bromine,  in  a  freezing  mixture,  it 
forms  a  crystalline  mass,  consisting  of  quintone  hexbromide,  C5H6Br6,  satu- 
rated with  a  thick  liquid,  which  is  a  mixture  of  the  compounds  C6H6Br6, 
C6H6Br4,  and  probably  C6H6Brr 

Terpenes,  Ci0H16. — These  bodies  are  volatile  oils,  existing  in  plants, 
chiefly  of  the  coniferous  and  aurantiaceous  orders;  they  have  not  yet  been 
formed  by  any  artificial  process.  The  most  important  member  of  the  group 
is  turpentine  oil,  which  is  contained  in  the  wood,  bark,  leaves,  and  other  parts 
of  pines,  firs,  and  other  coniferous  trees,  and  is  usually  prepared  by  dis-< 
tilling  crude  turpentine,  the  oleo-resinous  juice  which  exudes  from  incisions 
in  the  bark  of  the  trees,  either  alone  or  with  water.  It  was  formerly  sup- 
posed that  all  the  volatile  oils  thus  obtained,  and  having  the  composition 
C10H,6,  were  identical  in  chemical  and  physical  properties;  but  recent  in- 
vestigations, especially  those  of  Berthelot,  have  shown  that  the  turpentine 
oils  obtained  from  ditferent  sources  exhibit  considerable  diversities  in  their 
physical,  and  more  especially  in  their  optical  properties;  further,  that  most 
kinds  of  turpentine  oil  are  mixtures  of  two  or  more  isomeric  or  polymeric 
hydrocarbons,  differing  in  physical  and  sometimes  also  in  chemical  pro- 
perties. These  modifications  are  often  produced  by  the  action  of  heat  and 
of  chemical  reagents  during  the  purification  of  the  oil. 

The  several  varieties  of  turpentine  oil,  when  purified  by  repeated  rectifi- 
cation with  water,  are  colorless  mobile  liquids,  having  a  peculiar  aromatic 
but  disagreeable  odor.  They  are  insoluble  in  water,  slightly  soluble  in 
aqueous  alcohol,  miscible  in  all  proportions  with  absolute  alcohol,  ether,  and 
carbon  disulphide.  They  dissolve  iodine,  sulphur,  phosphorus,  and  many 
organic  substances  which  are  insoluble  in  water,  such  as  fixed  oils  and 
resins,  and  are  therefore  used  for  making  varnishes. 

The  principal  varieties  are,  French  turpentine  oil,  obtained  from  the 
French  or  Bordeaux  turpentine  of  Pinus  maritima,  and  English  turpentine 
oil,  from  the  turpentine  collected  in  Carolina  and  other  Southern  States  of 
the  American  Union,  from  Pinus  Aus/ralis  and  Pinus  tceda. 

French  turpentine  oil,  when  purified  by  neutralizing  it  with  an  alkaline 
carbonate,  and  then  distilling  it,  first  over  the  water-bath,  and  then  in  a 
vacuum  (by  which  treatment  all  transformation  of  the  product  by  heat  or 
by  reagents  is  avoided),  consists  mainly  of  a  hydrocarbon,  C,0H16,  called 
terebenthene.  It  has  a  specific  gravity  of  0-864,  boils  at  161°  C.  (322°  F.),  and 
turns  the  plane  of  polarization  of  a  ray  of  light  to  the  left.  English  tur- 
pentine oil,  treated  in  a  similar  manner,  yields,  as  its  chief  constituent,  a 
liquid  called  australene,  or  austratcrebenthene,  having  the  same  specific  gravity 
and  boiling  point  as  terebentheue,  but  turning  the  plane  of  polarization  to 
the  right. 


TERPENES.  489 

When  pure  turpentine  oil  (terebenthene  or  australene)  is  heated  to  200°- 
250°,  it  undergoes  a  molecular  transformation,  and  may  then  be  separated 
by  distillation  into  two  oils,  one  called  austrapyrolene,  isomeric  with  the 
original  oil,  and  boiling  at  176°  to  178°  C.  (348°-352°F.) ;  the  other,  called 
meta  terebenthene,  polymeric  with  the  original  oil,  having  the  formula  C20H32, 
and  boiling  at  a  temperature  above  360°  C.  (680°  F).  Both  are  levorota- 
tory,  the  latter  exhibiting  the  greater  amount  of  rotatory  power. 

Turpentine  oil  treated  with  boron  fluoride  or  strong  sulphuric  acid,  is  trans- 
formed into  two  hydrocarbons  having  no  action  on  polarized  light.  The 
one,  called  terebene,  has  the  formula  C,0H,6,  and  boils  at  160°  C.  (320°  F.) ; 
the  other,  called  colophene,  or  diterebenc,  consists  of  C20H32,  and  boils  at  a 
very  high  temperature. 

By  the  action  of  sodium  stearate  on  a  solid  compound  of  turpentine  oil 
and  hydrochloric  acid  to  be  presently  described,  a  crystallized  hydrocar- 
bon, CIOH,6,  called  camphene,  is  formed,  which  turns  the  plane  of  polariza- 
tion to  the  left  or  to  the  right,  according  as  it  has  been  formed  from  French 
or  from  English  turpentine  oil.  If  sodium  acetate  be  used  in  its  prepara- 
tion in  place  of  the  stearate,  the  same  hydrocarbon  is  obtained,  but  it  is 
then  optically  inactive. 

Turpentine  oil  exposed  to  the  air  absorbs  oxygen,  which  then,  as  in  all 
slow  combustions,  acquires  the  properties  of  ozone,  and  subsequently  en- 
ters into  combination  with  the  hydrocarbon,  forming  resinous  products. 
Nitric  acid,  and  other  powerful  oxidizing  agents,  convert  turpentine  oil  into 
a  number  of  acid  products  of  complex  constitution.  Strong  nitric  acid 
acts  very  violently  on  turpentine  oil,  sometimes  setting  it  on  fire. 

Chlorine  is  absorbed  by  turpentine  oil,  with  evolution  of  heat,  sometimes 
sufficient  to  produce  inflammation.  When  paper  soaked  in  rectified  tur- 
pentine oil  is  introduced  into  a  vessel  filled  with  chlorine,  the  turpentine 
takes  fire,  and  a  quantity  of  black  smoke  is  produced,  together  with  white 
fumes  of  hydrochloric  acid.  Bromine  acts  in  a  similar  manner.  Iodine  is 
dissolved  by  turpentine  oil,  forming  at  first  a  green  solution,  which  after- 
wards becomes  hot,  and  gives  off  hydriodic  acid.  When  a  considerable 
quantity  of  iodine  is  suddenly  brought  in  contact  with  turpentine  oil,  ex- 
plosion frequently  ensues.  Turpentine  oil  distilled  with  chloride  of  lime  and 
water,  yields  chloroform. 

Compounds  of  Turpentine  oil. —  Turpentine  oil  forms  several  compounds 
with  hydrochloric  acid.  The  gaseous  acid  converts  it  into  the  monohydro- 
'chloride,  C10H16.  HC1.  On  the  other  hand,  when  the  oil  is  subjected  for  sev- 
eral weeks  to  the  action  of  the  strong  aqueous  acid,  crystals  of  £  dihydro- 
chloride,  C,0HI6.2HC1,  are  obtained.  This  latter  compound  is  also  formed 
by  the  action  of  hydrochloric  acid  gas  on  lemon  oil ;  hence  it  is  called  citrene 
dihydrochloride.  By  the  action  of  hydrochloric  acid  on  terebene,  the  com- 
pound C20H32 .  HCl  is  formed,  called  diterebene  hydro  chloride.  Lastly,  when  a 
current  of  hydrochloric  acid  gas  is  passed  through  a  solution  of  turpentine 
oil  in  acetic  acid,  the  compound  C20H32.  3HC1  is  produced,  called  dipyrolene 
hydrochloride. 

Hydrobromic  and  hydriodic  acids  form,  with  oil  of  turpentine,  compounds 
analogous  in  composition  to  the  hydrochlorides ;  the  dihydriodide,  however, 
has  not  been  obtained  from  turpentine  oil  itself. 

Whatever  method  may  be  adopted  for  preparing  the  hydrochlorides,  hy- 
drobromides,  or  the  monohydriodide  of  turpentine  oil,  there  are  always 
two  isomeric  modifications  obtained  —  one- liquid,  the  other  solid  and  crys- 
talline. The  crystallized  monohydrochloride  is  sometimes,  though  inap- 
propriately, designated  as  artificial  camphor,  and  the  dihydrochloride  as 
lemon  C'tmphor. 

II f/drate.s  of  Turpentine  oil. —  The  terebenthenes  unite  with  water  in  sev- 
eral proportions,  yielding  the  following  compounds: 


490  HYDROCARBONS. 

C]0HI6 .  30H2          C10H16 .  20H2          C10H16 .  OH2          2C10H16 .  OH2 
Terpin  Terpin.  Terpintin  Terpinol. 

hydrate.  hydrate. 

Terpin  hydrate,  C,0H16.  20H2 .  Aq.  (also  called  Turpentine-camphor  and  Hy- 
drate of  Turpentine-oil"),  is  frequently  deposited  in  crystals  from  turpentine 
oil  containing  water ;  its  production  is  favored  by  the  presence  of  an  acid. 
To  prepare  it,  8  vols.  turpentine  oil  are  mixed  with  2  vols.  nitric  acid  and 
1  to  6  vols.  alcohol;  and  the  mixture  is  frequently  shaken  during  the  first 
few  days,  then  left  to  itself  in  shallow  vessels  for  several  weeks.  Brown 
crystals  are  thereby  formed,  which  must  be  pressed,  and  then  recrystal- 
lized  from  boiling  water,  with  addition  of  animal  charcoal. 

Terpin  hydrate  usually  crystallizes  in  large  rhombic  prisms;  it  dissolves 
sparingly  in  cold,  easily  in  boiling  water,  easily  also  in  alcohol  and  ether. 
At  100°  C.  (212°  F.)  it  melts,  gives  off  its  water  of  crystallization,  and  is 
converted  into  terpin.  The  same  change  takes  place  on  exposing  the  crys- 
tals to  air  dried  over  oil  of  vitriol. 

Terpin,  Ci0Hl6  .  20H2,  melts  at  103°  C.  (217°  F.),  and  solidifies  in  the  crys- 
talline state  on  cooling.  It  sublimes  at  about  150°,  in  slender  needles.  It 
is  dissolved  with  red  color  by  strong  sulphuric  acid,  and  converted  into 
turpentine  oil.  The  same  change  takes  place  on  boiling  the  terpin  Avith 
dilute  acids,  heating  it  to  100°  C.  (212°  F.)  with  zinc  chloride,  or  to  160°- 
180°  C.  (320°-356°  F.)  with  chloride  of  calcium,  strontium,  or  ammonium. 
Terpin,  or  terpin  hydrate,  subjected  to  the  action  of  gaseous  or  aqueous 
hydrochloric  acid,  or  of  the  chlorides,  bromides,  or  iodides  of  phosphorus, 
is  converted  into  the  crystallized  dihydrochloride,  dihydrobromide,  or  dihy- 
driodide ;  this  is  in  fact  the  only  way  of  obtaining  the  last-mentioned  com- 
pound. Terpin,  distilled  with  phosphoric  oxide,  yields  terebene  and  colo- 
phene  (p.  485).  Heated  with  acetic  or  butyric  acid,  or  with  benzoic  chlor- 
ide, it  yields  terebene  and  polyterebenes.  When  heated  with  acetic  oxide, 
(C2H30)20,  to  140°  C.  (284°  F  ),  for  not  too  long  a  time,  it  yields  a  com- 
pound containing  C10HI6  .  C2H402 .  OH2. 

Terpentin  hydrate,  C10Uj6  .  OH2,  is  sometimes  obtained  in  the  preparation 
of  terpin,  either  together  with  the  latter  or  alone.  It  is  a  liquid  insoluble 
in  water,  and  boiling  at  200°-220°  C.  (392°-428°  F.). 

Terpinol,  2Ci0H16  .  OH?,  is  produced  when  terpin  is  boiled  with  dilute 
hydrochloric  or  sulphuric  acid,  or  when  the  dihydrochloride  of  terebene  is 
boiled  with  water,  alcohol,  or  alcoholic  potash.  It  is  a  colorless,  strongly 
refracting  oil,  optically  inactive,  and  boiling  with,  partial  decomposition 
at  168°  C.  (334°  F.). 

The  hydrocarbon,  C]0H,6  (decone  or  terebenthene),  acts  as  a  quadrivalent 
radical,  capable  of  uniting  with  four  monad  atoms,  and  therefore  with  two 
molecules  of  the  acids  HC1,  HBr,  and  HI,  thereby  producing  the  dihydro- 
chlorides  above  mentioned  ;  but,  like  other  tetrad  radicals,  it  can  also  take 
up  only  two  monad  atoms,  producing  the  monohydrochloride,  &c.  The 
same  tetrad  radical,  by  doubling  itself,  loses  two  units  of  equivalence, — just 
as  two  atoms  of  carbon  when  united  are  satisfied  by  six,  and  not  by  eight 
atoms  of  hydrogen,  and  forms  the  hydrocarbon,  C20H32,  which  is  sexvalent, 
and  can  therefore  form  such  compounds  as  C20H32 .  3HC1.  Further,  this 
same  hexad  radical  might  form  non-saturated  compounds  containing  only 
four  or  two  monad  atoms ;  in  reality,  however,  only  those  containing  two 
monad  atoms  are  known,  such  as  C20H32 .  HC1. 

If  in  the  several  hydrochlorides  each  atom  of  chlorine  be  replaced  by 
hydroxyl,  HO,  we  obtain  the  formulae  of  the  several  hydrates  of  turpentine 
oil;  the  hydrate  corresponding  to  the  hydrochlorate,  C20H32 .  HC1,  has  not, 
however,  been  prepared. 


VOLATILE    OR   ESSENTIAL    OILS.  491 

VOLATILE  OILS  ISOMERIC  WITH  TURPENTINE  OIL. — The  following  volatile 
or  essential  oils  obtained  from  plants  exhibit,  like  oil  of  turpentine,  the 
composition  C,0H,6. 

Terpenes  from  Aurantiaceous  plants. — These  terpenes  are  distinguished  by 
their  fragrant  odor.  Lemon  oil,  obtained  from  the  rind  of  the  fruit  of  Cit- 
rus limonum,  by  pressure,  or  by  distillation  with  water,  consists  mainly  of 
citrene,  C10H,6,  a  hydrocarbon  closely  resembling  terebenthene,  having  a 
specific  gravity  of  0-85  at  15°,  boiling  at  167°  or  168°,  turning  the  plane 
of  polarization  to  the  right.  With  water  it  forms  a  crystallized  hydrate 
resembling  terpin ;  with  hydrochloric  acid,  a  dihydrochloride,  C,0H,6 .  2HC1, 
existing  in  a  solid  and  a  liquid  modification,  and  a  monohydrochloride, 
C10Hjg .  HC1,  apparently  susceptible  of  similar  modifications. 

Similar  oils  are  obtained  from  the  rind  of  the  sweet  orange  ( Citrus  auran- 
tium),  the  bergamot  (C.  bergamia],  the  bigarade  or  bitter  orange  (C.  bigara- 
dia),  the  lime  (C.  limclta},  the  sweet  lemon  (C.  lumia],  and  the  citron  (C. 
medico}.  Oil  of  neroli,  obtained  by  distilling  orange-flowers  with  water,  is 
probably  also  a  terpene  when  pure. 

Terpenes  from  other  sources. — The  volatile  oils  of  athamanta,  beech,  borneo 
(from  Dryabalanops  camphora],  caoutchouc,  caraway,  camomile,  coriander, 
elemi,  gomart,  hop,  juniper,  imperatoria,  laurel,  parsley,  pepper,  savin, 
thyme,  valerian,  and  others,  also  the  neutral  oils  of  wintergreen  (Gaul- 
theria  procumbens},  and  cloves,  are  isomeric  with  oil  of  turpentine.  The  oils 
of  copaiba  and  cubebs  are  probably  polymeric  with  it,  their  molecules  con- 
taining C.,0H32. 

Caoutchouc,  or  India-rubber,  the  thickened  milky  juice  of  several  species 
of  Ficus,  Euphorbia,  and  other  trees  growing  in  tropical  countries,  is  essen- 
tially a  mixture  of  several  hydrocarbons  isomeric  or  polymeric  with  turpen- 
tine oil.  When  pure  it  is  nearly  white,  the  dark  color  of  commercial 
caoutchouc  being  due  to  the  effects  of  smoke  and  other  impurities.  It  is 
softened  but  not  dissolved  by  boiling  water ;  it  is  also  insoluble  in  alcohol. 
In  pure  ether,  rectified  petroleum,  and  coal-tar  oil,  it  dissolves,  and  is  left 
unchanged  on  the  evaporation  of  the  solvent.  Oil  of  turpentine  also  dis- 
solves it,  forming  a  viscid,  adhesive  mass,  which  dries  very  imperfectly. 
At  a  temperature  a  little  above  the  boiling  point  of  water,  caoutchouc 
melts,  but  never  afterwards  returns  to  its  former  elastic  state.  Few  chemi- 
cal agents  affect  this  substance ;  hence  its  great  use  in  chemical  investiga- 
tions, for  connecting  apparatus,  &c.  By  destructive  distillation  it  yields  a 
lai-ge  quantity  of  a  thin,  volatile,  oily  liquid,  of  naphtha-like  odor,  called 
caoutchoucin,  which  dissolves  caoutchouc  with  facility.  This  oil,  according 
to  Mr.  Greville  Williams,  is  composed  of  two  polymeric  hydrocarbons : 
caoutchin,  C10H,fi,  boiling  at  171°  C.  (340°  F.),  and  isoprene,  C,HR,  boiling  at 
37°  C.  (99°  F.). 

Caoutchouc  combines  with  variable  proportions  of  sulphur.  The  mix- 
tures thus  obtained  are  called  vulcanized  India-rubber;  they  are  more  per- 
manently elastic  than  pure  caoutchouc. 

Vulcanite,  or  Ebonite,  is  caoutchouc  mixed  with  half  its  weight  of  sulphur, 
and  hardened  by  pressure  and  heating.  It  is  very  hard,  takes  a  high 
polish,  and  is  used  for  making  combs,  knife-handles,  buttons,  &c.  It  is 
also  especially  distinguished  by  the  large  quantity  of  electricity  which  it 
evolves  when  rubbed ;  hence  it  makes  an  excellent  material  for  the  plates 
of  electrical  machines. 

Gutta-percha,  the  hardened  milky  juice  of  Isonandra  gutta,  a  large  tree 
growing  in  Malacca  and  many  of  the  islands  of  the  Eastern  Archipelago, 
is  similar  in  composition  to  caoutchouc,  and  resembles  it  in  many  of  its 
properties,  but  is  harder  and  less  elastic.  It  is  quite  insoluble  in,  and  im- 
pervious to,  water,  and  being  also  an  excellent  electric  insulator,  is  exten- 
sively used  as  a  casing  for  submarine  telegraph  wires.  By  dry  distillation 


492  AROMATIC   HYDROCARBONS. 

it  yields  isoprene,  caoutchin,  and  a  heavy  oil  called  heveene,  probably  poly- 
meric with  these  bodies. 

VOLATILE  OR  ESSENTIAL  OILS  IN  GENERAL. — The  volatile  oils  obtained 
from  plants  mostly  consist  either  of  hydrocarbons  isomeric  or  polymeric 
with  turpentine  oil,  or  of  mixtures  of  those  hydrocarbons  with  compounds 
of  carbon,  hydrogen,  and  oxygen.  Thus  valerian  oil  contains  valeric  acid, 
C5H,002;  pelargonium  oil  contains  pelargonic  acid,  C9H1802;  rue  oil  con- 
tains capric  aldehyde,  C6H120 ;  wintergreen  oil  contains  acid  methyl  sali- 
cate,  C8H803,  the  oxygenated  compound  being  associated  in  each  case  with 
a  terpene.  Some  consist  essentially  of  aldehydes:  thus  bitter  almond  oil 
consists  of  benzoic  aldehyde,  C7H60 ;  the  oils  of  cinnamon  and  cassia  con- 
tain cinnamic  aldehyde,  C7H80 ;  and  those  of  anise,  star-anise,  fennel,  and 
tarragon,  contain  anethol,  C,0H120.  Those  volatile  oils  which  exist  ready 
formed  in  living  plants  do  not  appear  to  contain  any  elements  besides  car- 
bon, hydrogen,  and  oxygen.  Sulphur  is  found  only  in  certain  oils  result- 
ing from  a  kind  of  fermentation  process,  as  in  the  volatile  oils  of  mustard 
and  garlic;  nitrogen,  when  it  occurs,  must  be  regarded  as  an  impu- 
rity resulting  from  admixed  vegetable  tissue.  Volatile  oils  are  mostly 
procured  by  distilling  the  plant,  or  part  of  the  plant,  with  water ; 
their  points  of  ebullition  almost  always  lie  above  that  of  water ;  never- 
theless, at  100°  the  oils  emit  vapor  of  very  considerable  tension,  which 
is  carried  over  mechanically,  and  condensed  with  the  steam.  The  milky 
or  turbid  liquor  obtained  separates,  when  left  at  rest,  into  oil  and  water. 
Sometimes  the  oil  is  heavier  than  the  water,  and  sinks  to  the  bottom: 
sometimes  the  reverse  happens.  From  parts  of  plants  which  are  very  rich 
in  volatile  oil,  such  as  lemon  and  orange-peel,  the  oil  may  be  extracted  by 
pressure. 

A  few  volatile  oils  are  found  in  the  bodies  of  animals, —  oil  of  ants,  for 
example. 

Most  volatile  oils  are  colorless  when  pure ;  they  often,  however,  have  a 
yellow  color  arising  from  impurity ;  and  a  few,  the  oils  of  wormwood  and 
camomile,  for  example,  have  a  green  or  blue  color,  due  to  the  presence  of 
an  oily  compound  of  a  very  deep  blue  color,  called  cerulein.  They  have 
usually  a  powerful  odor,  and  a  pungent,  burning  taste.  "When  exposed  to 
the  air,  they  frequently  become  altered  by  slow  absorption  of  oxygen,  and 
assume  the  character  of  resins.  They  mix  in  all  proportions  with 
fat  oils,  such  as  linseed,  nut,  colza,  and  whale  oils,  and  dissolve 
freely  both  in  ether  and  alcohol :  from  the  latter  solvent  they  are 
precipitated  by  the  addition  of  water.  Volatile  oils  communicate  a 
greasy  stain  to  paper,  which  disappears  by  warming  ;  by  this  character 
any  adulteration  with  fixed  oils  can  be  at  once  detected.  Many  volatile 
oils,  when  exposed  to  cold,  separate  into  a  solid  crystalline  compound 
called  a  camphor  or  stearoptene,  and  a  liquid  oil,  which,  for  distinction,  is 
sometimes  called  an  elseoptene. 


FIFTH  SERIES,  CnH2n-6. — AROMATIC  HYDROCARBONS. 

The  hydrocarbons  of  this  series  present  peculiar  interest  on  account  of 
the  many  important  derivatives,  including  alcohols,  acids,  bases,  &c.,  to 
which  they  gave  rise.  The  whole  group  of  compounds  thus  formed  are 
usually  designated  as  aromatic  bodies,  on  account  of  the  peculiar  and  fra- 
grant odors  exhibited  by  some  of  them, —  benzoic  acid,  for  example. 


BENZENE.  493 

The  known  hydi-ocarbons  of  the  aromatic  series  are : 

Benzene C6H6 

Toluene C7H8 

Xylene C8HJO 

Cumene     .....  C9H12 

Cymene         .....  C10H14 

Amylxylene       ....  C^H^ 

They  are  all  found  (except  the  last)  in  the  lighter  part  of  the  oil  obtained 
by  the  destructive  distillation  of  coal,  and  may  be  separated  from  one 
another  by  fractional  distillation. 

These  hydrocarbons  might  be  regarded  as  derived  from  the  correspond- 
ing paraffins  by  abstraction  of  8  atoms  of  hydrogen  (e.g.,  C6H6=C6H,4  — 
H8),  or  from  the  olefines  by  abstraction  of  6  atoms  of  hydrogen,  &c. ;  and 
accordingly  they  might  be  expected  to  act  as  octovalent,  sexvalent,  quad- 
rivalent, or  bivalent  radicals ;  and,  in  fact,  cymene  can  combine  with  two 
atoms  of  chlorine,  and  benzene  forms  definite  compounds  with  6  atoms  of 
chlorine  and  of  bromine.  But  in  nearly  all  cases  the  aromatic  hydrocar- 
bons react  as  saturated  molecules,  like  the  paraffins,  yielding,  when  treated 
with  chlorine,  bromine,  or  nitric  acid,  not  additive  compounds,  but  substi- 
tution-products. 

Benzene  may  be  represented  as  a  saturated  molecule  by  the  following 
constitutional  formula,  in  which  the  carbon-atoms  are  united  together  by 
one  and  two  combining  units  alternately : 

H— C C— H 

H— C        C— H 

H— C  =  C— H 

The  other  hydrocarbons  of  the  series  may  be  derived  from  it  by  suc- 
cessive addition  of  CH2,  or  by  substitution  of  methyl,  CH3,  for  hydrogen ; 
thus: 

C7H8       =     C6H6(;CH3)      Methyl-benzene, 
C8H10      =     C6H4(CH3)2     Dimethyl-benzene, 
C9H,2      =     C6H3(CH3)3     Trimethyl-benzene, 
CIOH14    =     C6H2(CH3)4     Tetramethyl-benzene. 

Further,  a  hydrocarbon  isomeric  with  dimethyl-benzene  may  be  formed 
by  the  substitution  of  ethyl,  C2H5,  for  1  atom  of  hydrogen  in  benzene,  viz., 
ethyl-benzene,  C6H5(C2H5) ;  in  like  manner,  methyl-ethyl-benzene,  C6H4 
(CH3)(C2H5),  and  propyl-benzene,  C6H5(C3TI7),  are  isomeric  with  trimethyl- 
benzene ;  diethyl-benzene,  C6H4(C2H5).j,  with  tetramethyl-benzene,  &c.,  &c. 
It  is  easy  to  see  that,  in  this  manner,  a  large  number  of  isomeric  bodies 
may  exist  in  the  higher  terms  of  the  series. 

Benzene,  C6TT6. — This  hydrocarbon  can  be  produced  synthetically  from  its 
elements.  When  ethine,  C2H2,  which,  as  we  have  seen  (p.  485),  may  be 
formed  by  the  direct  combination  of  carbon  and  hydrogen,  is  heated  to  a 
temperature  somewhat  below  redness,  it  is  converted  into  several  polymeric 
modifications,  the  principal  of  which  is  trielhine  or  benzene,  3C2H2=C6H6. 

Benzene  is  also  formed  in  the  dry  distillation  of  many  organic  substances, 
and  is  contained  in  considerable  quantity  in  the  more  volatile  portion  of 
coal-tar  oil,  from  which  it  is  now  almost  always  prepared.  To  obtain  it,  the 
oil  is  repeatedly  washed  with  dilute  sulphuric  acid  and  with  potash,  to  re- 
move the  alkaline  and  acid  products  likewise  existing  in  it;  and  the  re- 
maining neutral  oil  is  submitted  to  repeated  fractional  distillation,  the  por- 


494  AROMATIC   HYDROCARBONS. 

tion  which  goes  over  between  80°  and  90°  C.  (176°-194°  F.)  being  collected 
apart.  On  cooling  this  distillate  to  — 12°  C.  (10°  F.),  the  benzene  crystal- 
lizes out,  and  may  be  purified  from  adhering  liquid  substances  by  pressure. 
It  is  now  prepared  in  immense  quantities  for  the  manufacture  of  aniline ; 
but  the  commercial  product  is  always  impure,  containing  also  the  higher 
members  of  the  aromatic  series. 

Pure  benzene  may  be  obtained  by  distilling  benzoic  acid  with  lime : 

C7H602    -f     CaO    =    C03Ca    +     C6H6 
Benzoic  Lime.  Calcium      Benzene, 

acid.  carbonate. 

Benzene  is  identical  with  the  so-called  bicarburet  of  hydrogen,  discovered 
many  years  ago  by  Faraday  in  the  liquid  condensed  during  the  compression 
of  oil-gas  (p.  172). 

Pure  benzene  is  a  thin,  limpid,  colorless,  strongly  refracting  liquid, 
having  a  peculiar  ethereal  odor.  It  has  a  density  of  0-885  at  15-5°  C. 
(60°  F.),  boils  at  82°  C.  (180°  F.),  and  solidifies  at  3°  C.  (37°  F.)  to  a  white 
crystalline  mass.  It  is  nearly  insoluble  in  water,  but  mixes  with  alcohol 
and  ether.  It  dissolves  iodine,  sulphur,  and  phosphorus,  and  a  large 
number  of  organic  substances,  fats  and  resins,  for  example,  which  are  in- 
soluble, or  very  sparingly  soluble  in  water  and  alcohol;  hence  its  use  in 
many  chemical  preparations,  and  for  removing  grease-spots  from  articles 
of  dress. 

Benzene,  passed  in  the  state  of  vapor  through  a  porcelain  tube  heated 
to  bright  redness,  is  partly  resolved  into  hydrogen  gas,  containing  a  small 
quantity  of  ethine,  and  the  following  liquid  products:  (1)  diphenyl,  C,2H]0 
=  2C6H6 — H2;  (2)  chrysene,  C18H,2  =  3C6H6 — H6;  (3)  benzcrythrene,  a  solid, 
resinous,  orange-colored  body  of  unknown  composition,  which  distils  over 
in  yellow  vapors  at  a  dull  red  heat;  (4)  bitumene,  a  blackish  liquid,  which 
remains  in  the  retort  at  a  dull  red  heat,  and  solidifies  on  cooling.* 

SUBSTITUTION-PRODUCTS  OF  BENZENE. —  Chlorine  and  bromine  act  readily 
on  benzene,  forming  substitution-products,  in  which  the  hydrogen-atoms 
are  successively  replaced  by  the  halogen  element;  thus  with  chlorine  the 
compounds 

C6H6C1,         C6H4C12,         C6H3C13,         C6H2C14,        C6HC16,        C6C16 

are  obtained.  The  formation  of  the  more  highly  chlorinated  products  is 
facilitated  by  the  presence  of  iodine  or  of  antimony  pentachloride. 

Monochlorobenzene,  C6H5C1,  which  may  also  be  prepared  by  the  action  of 
phosphorus  pentachloride  on  phenol,  C6H5(OH), — and  is  hence  regarded  as 
a  chloride  of  the  univalent  radical phenyl,  CeH5, — is  a  colorless  liquid,  heavier 
than  water,  and  boiling  at  about  136°.  When  treated  with  nascent  hy- 
drogen (evolved  from  water  by  sodium  or  sodium  amalgam)  it  is  reconverted 
into  benzene.  Dichlorobenzene,  C6H6C12,  is  a  crystalline  solid;  trichloro- 
benzene  is  a  liquid  which  does  not  solidify  at  0°.  The  more  highly  chlori- 
nated benzenes  are  crystalline  solids. 

Monobromobenzene,  C6H5Br,  is  a  liquid;  the  compounds  C6H4Br2,  and 
C6H3Br3,  are  solid ;  similarly  with  the  iodobenzenes. 

These  haloid  derivatives  of  benzene  are  comparatively  stable  compounds, 
which  do  not  give  off  their  chlorine,  bromine,  or  iodine  in  exchange  for  hy- 
droxyl  or  other  radicals  so  easily  as  the  corresponding  derivatives  of  the 
paraffins  (p.  478) ;  thus  monochlorobenzene  or  phenyl  chloride,  C6H5C1,  is  not 
converted  into  hydroxyl-benzene  or  phenyl  alcohol,  C6H5(OI1),  by  treat- 
ment with  water  or  alkalies. 

*  Berthelot,  Bulletin  de  la  Societe  Chimique  de  Paris,  [2]  vi.  pp.  272,  279. 


TOLUENE.  495 

Nitrobenzenes. — Benzene  dissolves  readily  in  strong  nitric  acid,  and  on 
adding  water  to  the  solution,  nitrobenzene,  C6H6(N02),  separates  out: 

C6H6    -f     N02(OH)     =     OH2    -f     C6H5N02. 

It  is  a  yellowish  liquid,  smelling  like  bitter  almonds,  and  hence  used  in 
perfumery;  it  is  known  commercially  by  the  incorrect  name  of  artificial  oil 
of  almonds.  By  reducing  agents  it  is  converted  into  amidobenzene  or  ani- 
line, C6H5(N2H),  which  will  be  described  among  organic  bases. 

Dinitrobenzene,  C6H4N204,  or  C6H4(N02)2,  produced  by  warming  benzene 
with  a  mixture  of  nitric  and  sulphuric  acids,  is  a  white  substance,  crystal- 
lizing in  needles ;  by  reducing  agents  it  is  converted  into  diamido-benzene 
or  phenylene-diainine,  C6H4(NH2)2. 

ADDITIVE-COMPOUNDS  OF  BENZENE. — Benzene,  although,  as  already  ob- 
served, it  mostly  reacts  as  a  saturated  molecule  —  exhibiting  indeed  in  its 
chemical  relations  a  very  close  resemblance  to  the  paraffins  —  can  never- 
theless, under  certain  circumstances,  take  up  6  atoms,  or  3  molecules,  of 
chlorine  or  bromine,  forming  the  compounds  C6H6C16,  and  C6H6Br6.  These 
are  crystalline  bodies,  obtained  by  exposing  benzene  to  sunshine  in  contact 
with  chlorine  or  bromine;  the  former  also  by  mixing  the  vapor  of  boiling 
benzene  with  chlorine.  Benzene  hexchloride  melts  at  132°  C.  (270°  F.), 
and  boils  at  288°  C.  (550°  F.j,  being  partly  resolved  at  the  same  time  with 
hydrochloric  acid  and  trichlorobenzene,  C6H6C16  =  3HC1  -f-  C6H3C13.  The 
same  decomposition  is  quickly  produced  by  heating  the  compound  with 
alcoholic  solution  of  potash.  Benzene  hexbromide  exhibits  a  similar  re- 
action. 

Benzene  is  also  capable  of  uniting  directly  with  three  molecules  of  hypo- 
chlorous  acid,  forming  the  compound  C6H9C1303,  or  C6H6  .  3C10H,  which  crys- 
tallizes in  thin  colorless  plates  melting  at  about  10°,  and  is  converted  by 
alkalies  into  a  saccharine  compound  called  jyhenose,  C6H1206,  isomeric  with 
glucose  or  grape-sugar : 

C6H9C1303     +     30HK    =     3KC1    +     C6H1206. 

Toluene,  C7H8,  or  Methyl  benzene,  C6H5(CH3).  —  This  hydrocarbon,  which 
may  also  be  regarded  as  a  compound  of  methyl  with  the  univalent  radical, 
phenyl,  i.  e.,  as  phenyl-methyl,  C6H5.  CH3,  is  produced :  Synthetically  (1)  by 
the  action  of  sodium  on  a  mixture  of  bromobenzene  (phenyl  bromide),  and 
methyl  iodide: 

C6H6Br  -f  CH3I  -f  Na2  =  NaBr  -f  Nal  +  C6H5.CH3. 

(2)  By  the  mutual  action  of  benzene  (phenyl  hydride),  and  methane 
(methyl  hydride),  in  the  nascent  state,  as  when  a  mixture  of  2  parts  of 
sodium  acetate  and  1  part  of  sodium  benzoate  is  subjected  to  dry  distilla- 
tion: 

C6H6     +     CH4    =     C7H8    +     H2. 

It  is  also  produced  by  distilling  toluic  acid,  C8H1002,  with  lime,  which 
abstracts  carbon  dioxide : 

C8H1002    =    C02     -f     C7H8. 

It  occurs,  together  with  benzene  and  the  other  hydrocarbons  of  the  series, 
in  light  coal-tar  oil,  and  in  the  products  of  the  distillation  of  wood,  tolu 
balsam,  dragon's-blood,  and  other  vegetable  substances;  and,  together  with 
many  other  hydrocarbons,  in  Rangoon  tar  or  Burmese  naphtha. 

Toluene  is  a  limpid  liquid,  smelling  like  benzene,  and  having  a  density 
of  0-881  at  5°C.  (41°  F.).  It  boils  at  111°  C.  (232°  F.),  and  does  not  solid- 
ify at  — 20°  C.  ( — 4°  F.).  In  respect  of  solubility  and  solvent  power,  it 
is  very  much  like  benzene,  but  dissolves  somewhat  more  readily  in  alcohol. 


496  AROMATIC    HYDROCARBONS. 

"When  treated  with  oxidizing  agents,  it  yields  benzoic  acid,  C7H602,  or  de- 
rivatives thereof;  with  potassium  chromate  and  sulphuric  acid,  it  yields 
benzoic  acid ;  and  by  prolonged  boiling  with  strong  nitric  acid,  nitroben- 
zoic  acid. 

Toluene  vapor  passed  through  a  red-hot  porcelain  tube  is  partly  resolved 
into  hydrogen  gas  (with  small  quantities  of  methane  and  ethine),  and  the 
following  liquid  products  :  (1)  Benzene  and  naphthalene  in  considerable 
quantities.  (2)  A  crystallizable  hydrocarbon  volatilizing  at  280°  C.  (58(5° 
F.),  and  probably  consisting  of  dibenzyl,  C,4HU.  (3)  A  liquid  isomeric 
with  the  last.  (4)  A  mixture,  distilling  above  360°,  of  anthracene  with  an 
oily  liquid.  (5)  Chrysene  and  the  last  decomposition-products  of  benzene. 
The  formation  of  benzene,  naphthalene,  anthracene,  and  dibenzyl  is  repre- 
sented by  the  equations: 

2C7H8  =  CUH14  +  H2;         2C7H8  =  C14H]0  +  3H2. 
Toluene.  Dibenzyl.  Toluene.  Anthracene. 

4C7H8      =       3C6H6       -f       C10H8       -f       3H2. 
Toluene.  Benzene.  Naphtha- 

lene. 

SUBSTITUTION-PRODUCTS  OF  TOLUENE.  —  The  formula  of  toluene,  C6H5 . 
CH3,  indicates  the  existence  of  two  series  of  substitution-products,  accord- 
ing as  the  replacement  of  the  hydrogen  by  other  radicals  takes  place  in 
the  phenyl  atom  or  benzene  residue,  or  in  the  methyl  atom;  thus: 

C6H4C1.  CH3  is  isomeric  with  €6H5.  CH2C1 

Monochlorotoluene.  Benzyl  chloride. 

C6H4(OH).CH3  "  C6H5.CH2(OH) 

Cresol.  Benzyl  alcohol. 

C6H4(NH2) .  CH3  "  C6H5 .  CH2(NH2) 

Toluidine.  Benzylamine. 

These  isomeric  derivatives  differ  considerably  from  one  another  in  their 
properties.  Those  on  the  left-hand  column,  formed  by  replacement  of 
hydrogen  in  the  benzene  residue,  are  comparatively  stable  and  indifferent 
compounds,  like  those  derived  in  like  manner  from  benzene  itself;  whereas 
those  on  the  right-hand  column,  formed  by  replacement  of  hydrogen  in 
the  methyl  atom,  are  more  active  bodies,  easily  exchanging  their  chlorine, 
hydroxyl,  &c.,  for  other  radicals  by  double  decomposition,  like  the  corre- 
sponding derivatives  of  the  paraffins  (p.  552).  Thus  benzyl  alcohol  treated 
with  hydrochloric  acid  yields  benzyl  chloride  (just  as  ordinary  ethyl  alcohol 
similarly  treated  yields  ethyl  chloride) ;  and  this  compound  heated  with 
ammonia  yields  benzylamine ;  the  chloride  is  also  easily  converted  into  the 
acetate,  cyanide,  &c.,  by  treatment  with  the  corresponding  potassium  salts. 
In  short,  these  last-mentioned  toluene  derivatives  exhibit  reactions  exactly 
like  those  of  the  corresponding  compounds  of  the  methyl  and  ethyl  series, 
and  may  in  like  manner  be  supposed  to  contain  an  alcohol-radical,  C»H7, 
called  benzyl,  or  tolyl,  e.g.,  benzyl  chloride  =  C7H7.  Cl;  benzyl  alcohol, 
C7H7 .  OH  ;  benzylamine  —  C7H7 .  NH2,  &c. 

Chlorotoluenes. — The  action  of  chlorine  on  toluene  gives  rise  to  a  number 
cf  substitution-products,  differing  in  constitution  according  as  the  reaction 
takes  place  at  high  or  at  low  temperatures.  Compounds  isomeric  with 
these  are  also  obtained  from  benzyl  alcohol.  Of  the  two  monochlorinated 
compounds  whose  existence  is  indicated  by  theory,  viz.,  monochlorotoluene 
and  benzyl  chloride,  the  first  is  produced  at  low,  the  second  at  compara- 
tively high  temperatures,  as  when  toluene  is  distilled  in  a  current  of  chlor- 
ine gas,  keeping  the  temperature  between  110°  and  140°  C.  (230°-284°  F.) 


XYLENE.  497 

Chlorotoluene  boils  at  157°-158°  C.  (314°-316°  F.);    benzyl  chloride  at 
176°.     The  former  treated  with  sodium  yields  toluene. 

Of  the  dichlorinated  derivatives  of  toluene,  three  isomers  may  exist,  viz.: 

C6H3C12 .  CH3  C6H4C1 .  C2HC1  C6H6  .  CHC12 

Dichloro-  Chlorobenzyl  Chlorobenzol 

toluene.  chloride.  (so  called). 

The  first  does  not  appear  to  have  been  obtained,  at  least  in  the  pure  state. 
The  second  is  formed  by  the  action  of  chlorine  on  benzyl  chloride,  or  on 
monochlorotoluene;  it  is  a  liquid  boiling  somewhat  below  200°  0.  (392°  F.). 
When  treated  with  alcoholic  potash,  it  easily  gives  up  half  its  chlorine  (that 
contained  in  the  methyl  atom,)  but  the  other  half  is  more  obstinately  re- 
tained. Chlorobenzol,  or  dichloromethy I-  benzene,  is  produced  by  the  action 
of  phosphorus  pentachloride  on  benzoic  aldehyde  or  bitter  almond  oil 
(C71I60).  It  is  a  colorless  strongly  refracting  oil,  which  boils  at  206°  C. 
(403°  F.),  and  when  heated  to  120°-130°  C.  (248°-266°  F.)  with  water  or 
aqueous  potash,  easily  gives  up  the  whole  of  its  chlorine  in  exchange  for 
oxygen,  reproducing  benzoic  aldehyde: 

C6H6.CHC12    +     OH2    =    2HC1     +    C6H5.COH 
Chlorobenzol.  Benzoic 

aldehyde. 

The  more  highly  chlorinated  toluenes,  C7H5C13  and  C7H4C14,  admit  of  a 
still  greater  number  of  isomeric  modifications ;  but  we  cannot  here  describe 
them  in  detail. 

The  bromotoluenes  are  analogous  in  composition  and  mode  of  formation  to 
the  chlorotoluenes,  and  exhibit  corresponding  isomeric  modifications. 

Nitro toluenes. — Mononitrotolucne,  CTH7(N02),  is  formed  by  treating  toluene 
in  the  cold  with  fuming  nitric  acid,  and  separates  on  addition  of  water  as  a 
red  liquid ;  but  on  redistilling  this  liquid,  collecting  the  portion  which 
passes  over  below  240°  C.  (464°  F.),  and  dissolving  it  in  alcohol,  it  is  ob- 
tained in  white  shining  crystals,  which  melt  at  54°  C.  (129°  F.),  and  distil 
without  decomposition  at  238°  C.  (460°  F.).  By  the  action  of  ammonium 
sulphide  it  is  converted  into  amido toluene,  or  toluidine,  C7H7(NH2).  Dinitro- 
toluene,  C7IIe(N02)2,  and  Trinitrotoluene,  C7H5(N02)3,  are  crystalline  bodies 
obtained  by  treating  toluene  with  hot  fuming  nitric  acid.  The  former  is 
.converted  by  ammonium  sulphide  into  nitrotoluidine,  C7H6(N02)(NH2). 

Xylene,  C8HIO,  or  Dimethyl-benzene,  C6H4(CH3)2,  or  Methyltoluene,  C7H7 
(CH3).  This  body  is  produced  synthetically  by  the  action  of  sodium  on  a 
mixture  of  bromotoluene  and  methyl  iodide : 

C6H4Br .  CH3  +  CII3t  +  Na2  =  NaBr  +  Nal  +  C6H4(CH3)2. 

It  is  contained  in  light  coal-naphtha,  and  may  be  prepared  by  subjecting 
the  least  volatile  portion  of  that  which  has  been  distilled  off  in  benzene 
manufactories  to  fractional  distillation,  to  separate  the  portion  which  boils 
at  about  141°  C.  (286°  F.);  this  portion  is  shaken  up  with  oil  of  vitriol 
containing  a  little  fuming  sulphuric  acid,  which  dissolves  the  xylene  as 
xylene-sulphuric  acid,  C8H10SOS ;  this  compound  is  decomposed  by'dry  dis- 
tillation ;  and  the  xylene  which  passes  over  is  purified  by  washing,  drying, 
and  distillation. 

Xylene  is  a  colorless  liquid  of  specific  gravity  0-86  at  19°  C.  ffiC°  F.), 
and  boiling  at  139°  C.  (282°  F.).  When  passed  in  the  state  of  vapor 
through  a  red-hot  tube,  it  is  resolved  into  a  mixture  of  several  hydrocar- 
bons, among  which  are  benzene,  toluene,  styrolene,  C8HP,  naphthalene, 
anthracene,  and  its  higlior  homologues.  The  formation  of  some  of  these 
products  is  represented  by  the  following  equations: 


498  AEOMATIC    HYDROCARBONS. 

^8^10  H2  =  CgHg 

Xylene.  Styrolene. 

3C8H10        —        3H2        =        2C7H8        +        C10H8 
Xylene.  Toluene.  Styrolene. 

2C7H8        -        3H2        =        C14H10 
Toluene.  Anthracene. 

Xylene  oxidized  with  a  mixture  of  sulphuric  acid  and  potassium  chromate 
is  converted  into  terephthalic  acid,  C8H6O4 ;  dilute  nitric  acid  converts  it 
into  the  intermediate  product,  toluic  acid,  C8H802 : 

C8H10        -f        03        =        OH2        +        C8H802 
C8HIO        +         06        =       20H2        +         C8H.04. 

Chlorine  and  bromine  act  upon  xylene  in  the  same  manner  as  upon  toluene, 
forming  substitution  derivatives,  which  are  susceptible  of  a  larger  number 
of  isomeric  modifications  than  those  of  toluene,  inasmuch  as  xylene  con- 
tains two  atoms  of  methyl,  whereas  toluene  contains  only  one ;  but  they 
have* not  been  very  minutely  examined. 

There  are  three  nitroxylenes,  containing  respectively  C8H9(N02),  C8Hg 
(N02)2,  and  C8H7(N02)3.  The  first  and  second  are  produced  by  the  action 
of  cold  fuming  nitric  acid  upon  xylene.  Mononitroxylene  is  a  heavy  oil,  con- 
verted by  reducing  agents  into  xylidine,  C8H7(NH2) ;  dinitroxylcne  is  a  solid, 
which  separates  from  dilute  alcohol  in  shining  crystals,  melting  at  93°. 
Trinitroxylene,  formed  by  treating  xylene  with  a  mixture  of  nitric  and  sul- 
phuric acids,  is  a  crystalline  body,  converted  by  reducing  agents  into  dini- 
troxylidine,  C8H(N02)2(NH2). 

Ethyl-benzene,  C6H5(C2H5),  isomeric  with  xylene,  is  produced  by  the 
action  of  sodium  on  a  mixture  of  monobromo-benzene  and  ethyl  bromide. 
It  is  a  colorless,  mobile  liquid,  very  much  like^oluene,  and  boiling  at  133° 
C.  (271°  F.).  By  oxidation  with  potassium  chromate  and  sulphuric  acid  it 
yields  benzoic  acid.  It  is  slowly  attacked  by  bromine,  forming  monobrom- 
ethylbenzene,  C8H4Br(C2H5),  which  is  a  liquid  boiling  at  200°  C.  (392°  F.); 
whereas  monobromo-xylene  boils  at  about  203°  C.  (397°  F.).  Heated  with 
bromine  to  100°,  it  yields  more  highly  brominated  compounds,  which  are 
also  liquid.  There  are  three  nitro-ethyl  benzenes,  which  are  all  liquid  at 
ordinary  temperatures. 

Isomeric  Hydrocarbons,  C9H12.  —  This  formula  includes  the  three  follow- 
ing isomeric  bodies: 

C6H3(CH3)3  C6H4(CA3)(C2H5)  C6H  (C,H7) 

Trimethyl-benzene.        Methyl-ethyl-benzene.        Propyl-benzene. 

The  first  two  have  been  prepared  synthetically. 

TRIMETHYL-BENZENE,  C6H3(CH3)3,  also  called  Coal-tar  Cumenc,  and  Pseudo- 
cumene.  —  This  hydrocarbon  is  produced  by  the  action  of  sodium  on  a  mix- 
ture of  monobromoxylene  and  methyl-iodide  : 

C6H?Br(CH3)2  -f  CH3I  +  Na2  =  NaBr  +  Nal  +  C6H3(CH3)S. 

From  coal-tar  oil  it  is  obtained  by  heating  the  portion  which  passes  over 
in  fractional  distillation  near  its  boiling-point,  with  strong  sulphuric  acid, 
decomposing  the  resulting  cumene-sulphuric  acid  by  distillation,  and  sub- 
iecting  the  product  to  fractional  distillation.  It  boils  at  166°  C.  (331C 
The  same  hydrocarbon  exists  in  Burmese  naphtha.  With  bromine  it  yields 
monobromotrimethylben/ene,  CflH,,Br,  which  crystallizes  from  alcohol  in 
large  white  laminae,  melting  at  73°  C.  (163°  F.).  The  dibrominated  com- 


CYMENE.  499 

pound  appears  to  be  liquid.     No  nitro-derivatives  of  pseudo-cumene  have 
yet  been  obtained. 

METHYL-ETHYL-BENZENE,  or  ETHYL-TOLUENE,  C6H4(CH3)(C2H5),  is  pre- 
pared by  the  action  of  sodium  on  a  mixture  of  monobromotoluene  and  ethyl 
bromide.  It  boils  at  159°  C.  (318°  F.),  and  when  oxidized  with  potassium 
chromate  and  sulphuric  acid,  yields  terephthalic  acid. 

PROPYL-BENZENE,  or  CUMENE,  C6H5(C3H7).  —  This  hydrocarbon  is  related 
to  cuminic  acid,  C,0H,202,  in  the  same  manner  as  benzene  to  benzoic  acid, 
and  is  produced  by  distilling  cuminic  acid  with  excess  of  baryta: 

C10H1202    =    C02    +     C9Hlr 

It  is  also  produced  from  phorone  (Ci0H140)  by  the  dehydrating  action  of 
phosphoric  oxide : 

C10H140    —    OH2    =     C9H12. 

Cumene  boils  at  152°-153°  C.  (305°-7°  F.).  By  treatment  with  potassium 
chromate  and  sulphuric  acid,  or  by  prolonged  boiling  with  dilute  nitric  acid, 
it  yields  benzoic  acid.  When  boiled  with  strong  nitric  acid,  it  is  converted  into 
nitro-benzoic  acid.  With  chlorine  it  yields,  according  to  Fittig,*  a  viscid,  non- 
distiliable  oil,  probably  consisting  of  C9Hi2Cl6.  Cumene  dissolves  in  fuming 
nitric  acid,  and  water  added  to  the  solution  throws  down  nitrocumene, 
C9IIn(N02),  as  a  yellow  oil,  which  by  reduction  yields  amidocumene  or 
cumidine,  C9Hn(NH2). 

MESITYLENE. — This  compound,  likewise  isomeric  with  cumene,  is  pro- 
duced in  small  quantity  by  distilling  acetone  made  up  into  a  paste  with 
sand,  with  strong  sulphuric  acid,  and  is  purified  by  repeated  fractional 
distillation,  finally  over  sodium.  It  is  a  liquid  which  boils  at  163°  C.  (325°  F.), 
and  when  oxidized  with  potassium  chromate  and  sulphuric  acid  yields  acetic 
acid,  but  no  benzoic  acid.  Hence  it  appears  to  have  a  constitution  totally 
different  from  that  of  the  aromatic  hydrocarbons.  Treated  with  cold  fum- 
ing nitric  acid,  not  in  excess,  it  yields  liquid  mtromesitylene,  C9Hn(N02) ; 
when  dropped  into  cooled  fuming  nitric  acid  it  forms  crystallizable  dini- 
tromesitylene,  C9II10(N02)2;  and  when  treated  in  like  manner  with  a  mix- 
ture of  oil  of  vitriol  and  turning  nitric  acid,  it  is  converted  into  trinitro- 
mesitylene,  C9II9(N02)3.  These  three  nitro-compounds,  subjected  to  the 
action  of  reducing  agents,  yield  the  three  amido-compounds,  amido-mesi- 
tylene,  or  mesidine,  C9H,,(NH2),  nitromesidine,  C9H,0(N02)(NH2),  and  dini- 
tromesidine,  C9H9(N02)2(NH2). 

Isomeric  Hydrocarbons,  C,0H,4. — Theory  indicates  the  existence  of  five 
bodies  of  this  group,  viz.,  tetrarnethyl-benzene,  dimethyl-cthyl-benzene, 
diethyl-benzene,  methyl-propyl-benzene,  and  quartyl-benzene.  Of  these 
the  second  only  has  been  prepared  synthetically.  Tetramethyl-benzene 
probably  occurs  amongst  the  products  of  the  destructive  distillation  of 
coal;  but  it  has  not  been  isolated.  Cymene,  a  hydrocarbon  existing  in 
various  essential  oils,  is  probably  methyl-propyl-benzene. 

DIMETHYL-ETHYL-BENZENE,  or  ETHYL-XYLENE,  C6H3(CH3)2(C2H6),  is  pre- 
pared by  treating  a  mixture  of  monobromoxylene  and  ethyl-bromide  with 
sodium.  It  boils  at  183°-184°  C.  (3Gl°-363°  F.).  With  bromine  it  forms 
heavy  oily  compounds,  and  with  a  large  excess  of  bromine  a  crystalline 
compound.  By  prolonged  warming  with  a  mixture  of  fuming  nitric  and 
sulphuric  acids,  it  yields  a  crystalline  trinitro-derivative,  melting  at  119° 
C.  (240°  F.). 

CYMENE. — This  name.is  applied  to  two  isomeric  hydrocarbons,  CIOH14, 
agreeing  in  composition,  but  differing  in  some  of  their  physical  and  chem- 
ical properties. 

*  Ann.  Ch.  Phurm.  cxii.  314. 


500  HYDROCARBONS. 

a.  Cymene. — This  hydrocarbon  exists,  together  with  cuminic  aldehyde,  in 
the  essential  oil  of  Roman  cumin  (Cuminum  cymmum),  and  may  be  obtained 
by  distilling  that  oil  with  alcoholic  solution  of  potash,  the  cuminic  aldehyde 
being  converted  into  cymene,  and  the  cymene  which  exists  ready-formed  in 
the  oil  passing  over  at  the  same  time : 

8C10H120      +       K20       =       2C10H1}K02      +       C]0H14 
Cuminic  Potassium  Potassium  Cymene. 

aldehyde.  oxide.  cuminate. 

a  cymene  is  a  colorless,  strongly  refracting  oil,  of  sp.  gr.  0-86  at  14°  C. 
(57°  F.),  boiling  at  175°-178°  C.  (347°-352°  F.).  By  prolonged  boiling  with 
dilute  nitric  acid  it  is  converted  into  toluic  acid,  C7H7(C02H) ;  with  stronger 
nitric  acid  it  yields  nitrotoluic  acid;  and  by  boiling  with  potassium  chro- 
mate  and  sulphuric  acid,  it  forms  terephthalic  acid,  C8III004— C6H4(C02)H2. 
According  to  Sieveking,  it  unites  with  chlorine  and  bromine,  forming  the 
liquid  compounds  C,0H,4C12  and  C10H,4Br.2;  according  to  Fittig  and  Ferber, 
it  forms  only  substitution-products. —  Cold  fuming  nitric  acid  converts  it 
into  liquid  nitrocymene,  C,0H13(N02),  which  is  converted  by  reducing  agents 
into  cymidine,  C,0H,3(NH2).  By  prolonged  heating  with  a  mixture  of  nitric 
and  sulphuric  acids,  it  is  converted  into  dinitrocymene,  C,0H12(N02)2,  which 
crystallizes  from  alcohol  in  long  needles  or  laminae,  melting  at  69-5°  C. 
(157°  F.);  by  still  further  treatment  (for  several  days)  with  the  mixed 
acids,  it  appears  to  yield  crystalline  trinitrocymene,  melting  at  107°  C. 

/?.    Cymene  is  obtained  by  heating  camphor  in  a  retort  with  zinc  chloride : 

GIO^IS     —     0H2     =     Ci0H]4 
Camphor.  Cymene. 

The  product  is  purified  from  lighter  hydrocarbons  by  fractional  distillation. 
0  cymene  boils  at  177°-179°  C.  (351°-350°  F.).  It  does  not  yield  tereph- 
thalic acid  by  oxidation.  With  bromine  it  easily  forms  the  crystalline  com- 
pound C10Hl2Br2.  Nitric  acid  acts  upon  it  in  the  same  manner  as  on 
a  cymene ;  but  (J  dinitrocymene  crystallizes  in  thin  plates  melting  at  90°, 
and  is  easily  converted  into  /?  trinitrocymene,  which  crystallizes  from 
alcohol  in  short  thin  prisms  melting  at  112-5°  C.  (234°  F.). 

Amyl-benzene,  CnHI6=C6H5(C5Hn). — This,  which  is  the  only  known 
aromatic  hydrocarbon  containing  11  carbon  atoms,  is  produced  by  the 
action  of  sodium  on  a  mixture  of  bromobenzene  and  amyl  bromide  diluted 
with  benzene.*  It  has  a  specific  gravity  of  0-86  at  12°  C.  (54°  F.),  and  boils 
at  195°  C.  (383°  F.).  With  chlorine  it  yields  viscid  products;  with  nitric 
acid  in  the  cold  a  liquid,  non-distillable  mononitro-derivate ;  at  higher 
temperatures,  dinitro-amyl-benzene. 


SIXTH  SERIES,  Cn  H^.g. 

The  only  known  hydrocarbons  of  this  series  are  phenylene,  C6H4,  and 
cinnamene,  or  styrolcne,  C8H8,  with  its  isomer,  metacinnamene. 

Of  phenylene  very  little  is  known.  A  liquid  having  the  composition 
C6H4,  and  boiling  at  91°  C.  (196°  F.),  was  found  by  Church f  among  the 
products  of  the  decomposition  of  monochloro-benzene  by  sodium  amalgam. 
It  is  probably  also  formed,  together  with  benzene,  when  diphenyl,  C12H10, 

*  Fitlig  and  Tollens,  Ann.  Ch.  Pharni.  cxxxi.  313. 
f  Journal  of  the  Chemical  Society,  xvi.  76. 


CINNAMENE.  501 

is  passed  through  a  red-hot  tube,  but  is  subsequently  converted  into  the 
polymeric  body,  chrysene:* 

C12HIO     =     C6H6     +     C6H4;     and     3C6H4    =     C18HI2. 
Diphenyl.     Benzene.     Phenylene.      Phenylene.     Chi-ysene. 

Cinnamene,  or  Styrolene,  C8H8,  is  produced  —  1.  Synthetically:  a.  By 
passing  a  mixture  of  benzene-vapor  and  ethine,  or  ethene,  through  a  red- 
hot  tube : 

C.TI.     +     C2H2     =     C6H8;  C8H6     +     C2H4    =     C8H8     +     H2 

Benzene.       Ethine.         Cinna-       Benzene.      Ethene.        Cinna- 
mene. mene. 

The  second  method  yields  it  in  larger  quantity  than  the  first. 

(i.  In  like  manner,  together  with  benzene,  from  diphenyl  and  ethene: 

CI2H10    +     C2H4    =    C8H8    +     C6H6. 

2.  In  the  decomposition  of  xylene  which  takes  place  when  the  vapor  of 
that  compound  is  passed  through  a  red-hot  tube :    C8Hi0  =•  C8H8  -j-  H2 
(p.  497). 

3.  By  distilling  cinnamic  acid  with  baryta,  which  removes  carbon  dioxide : 

C9H802    =    C02    +     C8H8. 

4.  Cinnamene  is  contained  in  liquid  storax,  and  may  be  separated  by  dis- 
tilling the  balsam  with  water  containing  a  little  sodium  carbonate,  to  retain 
cinnamic  acid. 

Cinnamene  is  a  very  mobile,  colorless  oil  of  specific  gravity  0-924.  It 
boils  at  145°  C.  (293°  F.),  and  does  not  solidify  at  —20°  C.  (68°  F.).  When 
heated  to  200°  C.  (392°  F.)  in  a  sealed  tube,  it  is  converted  into  a  white, 
transparent,  highly  refractive,  solid  substance,  called  metacinnamene  or 
metastyrolene.  This  substance,  when  heated  in  a  small  retort,  yields  a  dis- 
tillate of  pure  liquid  cinnamene.f 

A  mixture  of  cinnamene  vapor  and  ethene  passed  through  a  red-hot 
tube  yields  large  quantities  of  benzene  and  naphthalene.  The  first  is  pro- 
duced from  the  cinnamene  by  abstraction  of  C2H2 ;  the  second  according 
to  the  equation: 

C8H8        +        C2II4        =        C10H8        -f        2H2. 

A  mixture  of  cinnamene  and  benzene  vapors,  passed  through  a  red-hot 
porcelain  tube,  yields  anthracene,  C14H10,  together  with  small  quantities  of 
other  products: 

C8H8        +        C6H6        =        C14H10        +        2H2. 

Cinnamene  acts  with  chlorine  and  bromine  like  a  bivalent  radical,  form- 
ing the  compounds  C8H8C12  and  C8H8Br2,  which,  when  treated  with  alcoholic 
potash,  give  up  HC1  and  HBr  (like  the  corresponding  ethene-compounds), 
leaving  chloro-cinnamene,  C8H7C1,  and  bromo-cinnamene,  C8B7Br.  Accord- 
ing to  Laurent,  cinnamene  yields  with  chlorine  a  hexchloride  of  dichloro- 
cinnamcne,  C8H6C12.C16;  if  this  be  correct,  cinnamene  must  be  regarded 
as  a  sexvalent  radical. — Metacinnamene  is  also  acted  upon  by  bromine, 
but  with  considerable  difficulty.  —  Both  cinnamene  and  metacinnamene 

*  RrrthfW,  .Tahrosbericht  fllr  Chemio,  IRGfi.  p.  544. 

f  It  was  formerly  supposed  that  ciimnniene  prepared  from  cinnamic  acid  wns  not  converted 
by  heat  into  a  solid  modification,  like  styrolcne  from  storax:  hence  tho  two  were  regarded  as 
isomeric,  not  identical ;  but  later  researches  have  shown  that  pure  ciniiamene  from  ciuiiaiuic 
acid  is  likewise  couvertible  into  solid  metacinnamene. 


502  HYDROCARBONS. 

treated  with,  fuming  nitric  acid  yield  mononitrated  derivatives,  C8H7(N02): 
that  obtained  from  cinnamene  is  crystalline;  that  from  metacinnamene 
amorphous. 


SEVENTH  SERIES,  CnH2n_10. 

The  only  known  hydrocarbon  belonging  to  this  series  is  one  containing 
CjgH^,  which  is  formed  by  dehydration  of  cholesterin,  C26H440  (a  crystal- 
line compound  contained  in  bile  and  biliary  calculi).  It  has  been  but  little 
examined. 

Another  member  of  the  same  series,  Ci0H,0,  might  perhaps  be  formed  by 
heating  bromocinnamene  with  sodium  ethylate  (C8H7Br-|-C3H5NaO— NaBr 
+OH2+C10H10.) 


EIGHTH  SERIES,  CnH2n_12. 

Of  this  series,  also,  only  one  member  is  known  with  certainty,  namely, 
naphthalene,  C10Hg,  produced  in  the  distillation  of  coal.  According  to 
Chancel,  two  hydrocarbons,  isomeric  or  polymeric  with  this  body,  are 
formed  in  the  dry  distillation  of  calcium  benzoate ;  but  they  have  not  been 
much  studied. 

Naphthalene,  C10H8. — This  hydrocarbon  is  produced,  as  already  ob- 
served, in  the  decomposition  of  toluene,  xylene,  and  cumene  at  a  red  heat; 
also  by  passing  vapor  of  benzene,  cinnamene,  chrysene,  or  anthracene 
through  a  red-hot  tube.  It  is  formed  in  large  quantities  as  a  by-product 
in  the  preparation  of  coal-gas,  its  production  doubtless  arising  from  reac- 
tions similar  to  those  just  mentioned.  When  the  last  portion  of  the  volatile 
oily  product  which  passes  over  in  the  distillation  of  coal-tar,  is  collected 
apart  and  left  to  stand,  a  quantity  of  solid  crystalline  matter  separates, 
which  is  principally  naphthalene.  An  additional  quantity  may  be  obtained 
by  pushing  the  distillation  until  the  contents  of  the  vessel  begin  to  char ; 
the  naphthalene  then  condenses  in  the  solid  state,  but  dark-colored  and 
very  impure.  By  simple  sublimation,  once  or  twice  repeated,  it  is  obtained 
perfectly  white.  In  this  state  naphthalene  forms  large,  colorless,  trans- 
parent, brilliant,  crystalline  plates,  exhaling  a  faint  and  peculiar  odor, 
which  has  been  compared  to  that  of  the  narcissus.  Naphthalene  melts  at 
80°  C.  (176°  F.)  to  a  clear,  colorless  liquid,  which  crystallizes  on  cooling: 
it  boils  at  212°  C.  (414°  F.),  and  evolves  a  vapor  whose  density  is  4-528. 
When  strongly  heated  in  the  air,  it  inflames  and  burns  with  a  red  and  very 
smoky  light.  It  is  insoluble  in  cold  water,  but  soluble  to  a  slight  degree 
at  the  boiling  temperature;  alcohol  and  ether  dissolve  it  easily;  a  hot 
saturated  alcoholic  solution  deposits  fine  iridescent  crystals  on  cooling. 

Naphthalene  dissolves  in  warm  strong  sulphuric  acid,  forming  two  crys- 
talline acids:  sulphonaphthalic  acid,  C,0H8S03,  and  disulphonaphthalic 
acid,  C,0H8S206,  both  of  which  form  soluble  barium  salts. 

Naphthalene  unites  directly  with  4  atoms  of  bromine  and  chlorine,  forming 
the  compounds  Ci0H8Cl4  and  C,0II8Br4.  It  also  forms  a  great  number  of 
substitution-products  with  these  elements,  bromine  being  capable  of  replac- 
ing from  1  to  4,  and  chlorine  from  1  to  8  atoms  of  hydrogen  in  naphthalene; 
there  are  also  several  derivatives  containing  both  bromine  and  chlorine, 
e.g.,  C]0H3Br2Cl3.  Many  of  these  substitution-derivatives  are  susceptible 
of  isomeric  modifications  differing  from  one  another  in  their  physical  pro- 
perties. The  chloro-  and  bromo-naphthalenes  are  capable,  like  naphtha- 
lene itself,  of  uniting  with  4  atoms  of  bromine  or  chlorine,  and  with  2 


DIPHENYL —  DIBENZYL.  503 

molecules  of  hydrochloric  or  hydrobromic  acid,  forming  such   compounds 
as  CIOH6C12.C14,  C10H4Br2Cl2.2HCl,  &c.* 

With  strong  nitric  acid,  naphthalene  yields  the  three  substitution-products, 
C10H7(N02),  C,0H6(N02)2,  and  C]0H5(N02)3,  all  of  which  are  white  crystalline 
solids.  The  first  is  converted  by  reducing  agents  into  amidonaphthalene, 
naphthalidine,  or  naphthylamine,  C10HT(NH2). 


NINTH  SERIES,  CnH2n_14. 

Two  members  of  this  series  are  known,  viz.,  diphenyl,  C12H10,  and  diben- 
zyl,  C14H)4 ;  they  are  so  called  because  their  molecules  are  the  doubles  of 
the  hypothetical  monatomic  radicals,  phenyl,  C6H6,  and  benzyl,  C7Hr 

Diphenyl,  C,2H,0,  is  produced:  (1)  as  already  observed,  by  passing  ben- 
zene vapor  through  a  red-hot  tube:  2C6H6=Cl2H,0-f-H2.  (2)  By  the  action 
of  sodium  on  phenyl  bromide  or  nionobromobenzene : 

2C6H5Br     +     Na2    =     2NaBr     +     C12H10. 

(3)   Together  with  other  products,  by  the  action  of  alcoholic  potash  on 
nitrate  of  diazobenzene:  f 

2C6H4N2      +       C2H60      =      C12H10      +       C2H40      -f      2N2 
Diazobenzene.          Alcohol.  Diphenyl.          Aldehyde. 

Diphenyl  appears  also  to  be  one  of  the  constituents  of  crude  anthracene 
(p.  504),  and  passes  over  in  the  distillation  of  that  substance,  at  about 
260°  C.  (500°  F.) 

Diphenyl  crystallizes  from  alcohol  in  iridescent  nacreous  scales,  which 
melt  at  about  60°  C.  (140°  F.),  sublime  at  a  higher  temperature,  and  boil 
at  about  240°  C.  (464°  F. ).  'It  is  converted  by  bromine  into  dibromodiphenyl, 
C,2H8Br2,  and  by  fumkig  nitric  acid  into  dinitro-diphenyl,  C,2H8(N02)2.  The 
latter  is  converted  by  hydrogen  sulphide  into  diamido-diphenyl  or  ben- 
zidine,  C,2H8(NH2)2,  a  crystalline  base,  which,  when  treated  with  nitrous 
acid,  yields  the  nitrate  of  tetrazodiphenyl  or  diazobenzidine : 

C12H12N4    +     2NH02    =    C12H6N4    40H2. 

Duimido-  Nitrous  Tetrazo- 

diphenyl. acid.  diphenyl. 

Dibenzyl,  C14H,4,  is  produced  by  heating  benzyl  chloride,  C7H7C1,  or  ben- 
zylidene  bromide,  C7H6Br2  (a  product  of  the  action  of  phosphorus  penta- 
bromide  on  bitter-almond  oil),  with  sodium.  It  is  a  crystalline  solid,  insol- 
uble in  water,  but  soluble  in  alcohol  and  ether ;  melts  at  about  52°  C.  (126°  F.), 
and  distils  without  decomposition  at  284°  C.  (543°  F.).  When  treated  with 


also  unites  directly  with  bromine,  forming  the  crystalline  compound  C,4H.  Br  . 
Fuming  nitric  acid  converts  it  into  dinitro-dibenzyl,  CMHJ2(N02)2,  which 
crystallizes  in  needles,  and  is  converted  by  reducing  agents  into  the  corre- 
sponding amido-compound,  C,4H,2(NH2)2. 

*  See  Watts's  Dictionary  of  Chemistry,  vol.  iv.  p  6 
t  Griess,  Phil.  Trans.  1864,  part  iii.  p.  693, 


504 


HYDROCARBONS. 


TENTH  SERIES,  CnH2n_16. 

Of  this  series  only  one  member  has  hitherto  been  obtained,  viz.,  sdlbene, 
C14H12,  which  is  formed,  together  with  other  products,  by  heating  benzyl- 
idene  sulphide  : 


8C7H6S        = 
Benzylidene 


Stilbene. 


Ca8H18S       -f- 


3SH 


- 

Thionessal. 
sulphide. 

It  crystallizes  in  colorless  plates  having  a  mother-of-pearl  lustre,  melts 
above  100°,  and  boils  at  292°  C.  (558°  F.).  It  forms  substitution-products 
with  chlorine,  bromine,  and  nitric  acid,  and  unites  directly  with  chlorine, 
forming  the  compound  C14H12C12. 


ELEVENTH  SERIES,  CnH2n_,8. 

Anthracene,  or  Paranaphthalene,  C14H,0,  is  produced:  (1)  By  passing  a 
mixture  of  benzene  with  ethene  gas  or  cinnamene  vapor,  or  of  diphenyl  or 
chrysene  vapor  with  ethene  gas,  through  a  red-hot  porcelain  tube  ;  also  by 
exposing  a  mixture  of  benzene  and  naphthalene  vapor  to  a  white  heat  : 


2C.H. 

Benzene. 

C6H6 
Benzene. 

C12H10 
Diphenyl. 

C18H12 
Chrysene. 


Naphthalene. 


C2H4   =   3H2 
Ethene. 

C8H8   =   2H2 
Cinnamene. 

C2H4   =   H 
Ethene. 


Ethene. 


=     C6H6 
Benzene. 


8C6H.    = 
Benzene. 


3H 


Ct4H10 
Anthracene. 


Anthracene. 


Anthracene. 

CT4H10 
Anthracene. 


. 
Anthracene. 


Also  when  toluene,  xylene,  or  cumene  is  passed  through  a  red-hot  tube 
(pp.  496,  497). 

Anthracene  is  produced  in  the  dry  distillation  of  coal,  bituminous  shale, 
and  wood,  and  is  contained  in  the  last  heavy  and  semifluid  portions  of  the 
tar,  at  first  together  with  naphthalene,  finally  with  chrysene.  A  com- 
mercial product  of  this  kind,  used  as  a  lubricator  for  machinery,  is  yellow, 
soft,  somewhat  like  palm-oil,  and  contains  anthracene,  together  with  several 
of  its  homologues  and  other  hydrocarbons.  To  obtain  pure  anthracene, 
the  crude  commercial  product  is  distilled  from  an  iron  retort,  the  first  and 
last  portions  of  the  distillate  being  rejected,  and  the  intermediate  portion 
crystallized  either  from  alcohol  or  from  coal-oils  boiling  between  100°  and 
120°  C.  (212°-248°  F.). 

Anthracene  forms  small  colorless  micaceous  laminae,  of  sp.  gr.  1-147, 
melting  at  about  213°  C.  (415°  F.),  subliming  slowly  at  100°,  more  quickly 
at  a  stronger  heat,  and  boiling  between  220°  and  230°  C.  (428°-446°  F.).  It 
is  insoluble  in  water,  but  dissolves  easily  in  boiling  alcohol,  more  abundantly 
in  ether,  benzene,  and  volatile  oils,  especially  oil  of  turpentine.  It  forms 
substitution-products  with  bromine  and  chlorine.  Dibromanthracene  unites 
with  bromine,  forming  the  compound  C14H8Br2.  Br2,  and  chloranthracene 
forms  a  hydrochloride  containing  C,4H7C1.  HC1. 

Anthracene,  boiled  with  nitric  acid  for  some  days,  is  converted  into  oxan- 


PYRENE,  CHKYSENE,  ETC.  505 

thracene,  C)4Hg04,  or  C14H80  .  0,  and  if  fuming  nitric  acid  be  added  from 
time  to  time,  dinitroxanthracene,  C14H6(N02)202,  is  obtained. 

J'l/rene,  a  hydrocarbon  obtained  by  Laurent,  together  with  chrysene,  from 
the  least  volatile  portion  of  coal-tar,  appears  to  be  identical  with  anthra- 
cene. 

Crude  anthracene  contains  also  several  hydrocarbons  homologous  with 
anthracene,  and  less  volatile  than  anthracene  itself;  among  others,  methyl- 
anthracene,  C,5H,2,  or  C,4H9(CH3),  which  is  identical  with  the  paranaph- 
thalene  of  Dumas,  and  tetramethyl-anthracene,  or  retene,  C18H  J8.  or  C,4H6  (CHg)4. 

Retene,  which  is  polymeric  with  benzene,  likewise  occurs  in  thin  unctuous 
scales  on  fossil  pine-stems  in  beds  of  peat  and  lignite  in  Denmark  and  other 
localities.  It  is  produced  also  in  the  dry  distillation  of  very  resinous  fir 
and  pine-wood,  passing  over  together  with  the  heavy  tar-oil,  and  separating 
in  scales  like  paraffin.  It  is  soluble  in  warm  alcohol  and  ether,  and  dis- 
solves easily  in  oils  both  fixed  and  volatile  ;  sulphuric  acid  converts  it  into 
disulphoretic  add,  C18H18S206. 


TWELFTH  SERIES,  CnH2n_24. 

Chrysene,  C18H12,  is  produced,  together  with  benzene,  by  heating  diphenyl 
for  an  hour  in  a  sealed  tube  filled  with  hydrogen,  the  diphenyl  being  prob- 
ably resolved  in  the  first  instance  into  benzene  and  phenylene,  which  latter 
is  then  polymerized  into  chrysene: 

C1?H10     =     C6H6     +     C6H4;  and"  3C6H4    =     C)8H12. 
Diphenyl.     Benzene.      Phenyl-        Phenyl-       Chrysene. 

ene.  ene. 

Chrysene  is  also  found,  together  with  benzerythrene  (p.  493),  in  the 
last  product  obtained  by  the  distillation  of  crude  anthracene,  and  in  the 
residue  left  in  the  retort;  in  larger  quantity  also  in  the  last  products  of 
the  distillation  of  pitch.  Laurent  likewise  obtained  it  together  with  pyrene 
(anthracene)  by  the  dry  distillation  of  fats  and  resins.  Pure  chrysene  has 
a  line  yellow  color.  It  is  insoluble  in  alcohol,  nearly  insoluble  in  ether, 
and  is  deposited  from  boiling  oil  of  turpentine  in  yellow  crystalline  flakes. 


APPENDIX  TO  HYDROCARBONS. 

Petroleum,  Naphtha,  and  other  allied  Substances. 

Pit-coal,  lignite  or  brown  coal,  jet,  bitumen  of  various  kinds,  petroleum  or 
rock-oil,  and  naphtha,  and  a  few  other  allied  substances  more  rarely  met 
with,  are  looked  upon  as  products  of  the  decomposition  of  organic  matter, 
especially  vegetable  matter,  beneath  the  surface  of  the  earth,  in  situations 
where  the  conditions  of  contact  with  water,  and  nearly  total  exclusion  of 
atmospheric  air,  are  fulfilled.  Deposited  at  the  bottom  of  seas,  lakes,  or 
rivers,  and  subsequently  covered  up  by  accumulations  of  clay  and  sand 
hereafter  destined  to  become  shale  and  gritstone,  the  organic  tissue  under- 
goes a  kind  of  fermentation  by  which  the  bodies  in  question,  or  certain  of 
them,  are  slowly  produced.  Carbon  dioxide  and  marsh-gas  are  bye-pro- 
ducts of  the  reaction ;  hence  their  frequent  disengagement,  the  first  from 
beds  of  lignite,  and  the  second  from  the  further  advanced  and  more  per- 
fect coal. 

The  vegetable  origin  of  coal  has  been  placed  beyond  doubt  by  micro- 
scopic research ;  vegetable  structure  can  be  thus  detected  even  in  the  most 
43 


506         APPENDIX  TO  HYDROCARBONS. 

massive  and  perfect  varieties  of  coal  when  cut  into  thin  slices.  In  coal  of 
inferior  quality,  much  mixed  with  earthy  matter,  it  is  evident  to  the  eye. 
The  leaves  of  ferns,  reeds,  and  other  succulent  plants,  more  or  less  resem- 
bling those  of  the  tropics,  are  found  in  a  compressed  state  between  the 
layers  of  shale  or  slaty  clay,  preserved  in  the  most  beautiful  manner,  but 
entirely  converted  into  bituminous  coal.  The  coal-mines  of  Europe,  and 
particularly  those  of  our  own  country,  furnish  an  almost  complete  fossil 
flora  —  a  history  of  many  of  the  now  lost  species  which  once  decorated  the 
surface  of  the  earth. 

In  the  lignites  the  woody  structure  is  much  more  obvious.  Beds  of  this 
material  are  found  in  very  many  of  the  newer  strata,  above  the  true  coal, 
to  which  they  are  consequently  posterior.  As  an  article  of  fuel,  brown 
coal  is  of  comparatively  small  value :  it  resembles  peat,  giving  but  little 
flame,  and  emitting  a  disagreeable  pungent  smell. 

Jet,  used  for  making  black  ornaments,  is  a  variety  of  lignite. 

The  true  bitumens  are  destitute  of  organic  structure:  they  appear  to 
have  arisen  from  coal  or  lignite  by  the  action  of  subterranean  heat;  and 
very  closely  resemble  some  of  the  products  yielded  by  the  destructive  dis- 
tillation of  those  bodies.  They  are  very  numerous,  and  have  yet  been  but 
imperfectly  studied. 

1.  Mineral  pitch,  or  compact  bitumen,  the  asplialtum  or  Jew's  pitch  of  some 
authors. — This  substance  occurs  abundantly  in  many  parts  of  the  world — 
as  in  the  neighborhood  of  the   Dead   Sea  in  Judea;   in  Trinidad,  in   the 
famous  pitch  lake,  and  elsewhere.     It  generally  resembles  in  aspect  com- 
mon pitch,  being  a  little  heavier  than  water,  easily  melted,  very  inflam- 
mable, and  burning  with  a  red,  smoky  flame.     It  consists  principally  of  a 
substance,  called  by  Bossingault  asphaltene,  composed  of  C^H^^Og.     It  is 
worthy  of  remark,  that  Laurent  found  paranaphthalene  in  a  native  mineral 
pitch. 

2.  Mineral  tar  seems  to  be  essentially  a  solution  of  asphaltene  in  an  oily 
fluid  called  petrolene.     This  liquid  has  a  pale-yellow  color,  and  peculiar 
odor ;  it  is  lighter  than  water,  and  very  combustible,  and  has  a  high  boil- 
ing-point.    It  has  the  same  composition  as  the  oils  of  turpentine  and  lemon- 
peel — namely,  CTOH,6.     Asphaltene  contains,  consequently,  the  elements  of 
petrolene,  together  with  a  quantity  of  oxygen,  and  probably  arises  from 
the  oxidation  of  that  substance. 

3.  Elastic  bitumen ;  mineral  caoutchouc.  —  This  curious  substance  has  only 
been  found  in  three  places:   in  a  lead-mine  at  Castleton,  in  Derbyshire; 
at  Montrelais,  in  France  ;  and  in  the  State  of  Massachusetts.     In  the  two 
latter  localities  it  occurs  in  the  coal  series.     It  is  fusible,  and  in  many  re- 
spects resembles  the  other  bitumens. 

Under  the  names  petroleum  or  rock-oil  and  naphtha  are  arranged  various 
mineral  oils  which  are  observed  in  many  places  to  issue  from  the  earth, 
often  in  considerable  abundance.  There  is  every  reason  to  suppose  that 
these  owe  their  origin  to  the  action  of  internal  heat  upon  beds  of  coal,  as 
they  are  usually  found  in  connection  with  such.  The  term  naphtha  is  given 
to  the  thinner  and  purer  varieties  of  rock-oil,  which  are  sometimes  nearly 
colorless ;  the  darker  and  more  viscid  liquids  bear  the  name  of  petroleum. 

Some  of  the  most  noted  localities  of  these  substances  are  the  following: 
The  north-west  side  of  the  Caspian  Sea,  near  Baku,  where  beds  of  marl 
are  found  saturated  with  naphtha.  Wells  are  sunk  to  the  depth  of  about  30 
feet,  in  which  naphtha  and  water  collect,  and  are  easily  separated.  In  some 
parts  of  this  district  so  much  combustible  gas  or  vapor  rises  from  the 
ground,  that,  when  set  on  fire,  it  continues  burning,  and  even  affords  heat 
for  economical  purposes.  A  large  quantity  of  an  impure  variety  of  petro- 
leum comes  from  the  Birman  territory  in  the  East  Indies:  the  country  con- 
sists of  sandy  clay,  resting  on  a  series  of  alternate  strata  of  sandstone  and 


COAL,  PETROLEUM,  ETC.  507 

shale.  Beneath  these  occurs  a  bed  of  pale-blue  shale  loaded  with  petro- 
l-.Mim,  which  lies  immediately  on  coal.  A  petroleum-spring  exists  at  Cole- 
brook  Dale,  in  Shropshire,  and  immense  quantities  come  now  from  Canada, 
Pennsylvania,  and  other  parts  of  North  America.  The  sea  near  the  Cape 
de  Verd  Islands  has  been  seen  covered  with  a  film  of  rock-oil.  Fine  speci- 
mens of  naphtha  are  furnished  by  Italy,  where  it  occurs  in  several  places. 

In  proof  of  the  origin  attributed  to  these  substances,  an  old  experiment 
of  Reichenbach  may  be  cited,  who,  by  distilling  with  water  about  100  Ibs. 
of  pit-coal,  obtained  nearly  2  ounces  of  an  oily  liquid,  exactly  resembling 
the  natural  naphtha  of  Amiano,  in  Italy.  The  manufacture  of  such  pro- 
ducts (paraffin  oils)  by  distilling  Boghead  and  other  kinds  of  coal  at  a  low 
red  heat,  is  now  conducted  on  a  very  large  scale  (p.  476). 

The  variations  of  color  and  consistence  in  different  specimens  of  rock- 
oil  depend  in  great  measure  upon  the  presence  of  pitchy  and  fatty  sub- 
stances dissolved  in  the  more  fluid  oil. 

The  boiling  point  of  rock-oil  varies  from  about  80°  to  326°.  A  thermom- 
eter inserted  into  a  retort  in  which  the  oil  is  undergoing  distillation,  never 
shows  for  any  length  of  time  a  constant  temperature  :  hence  it  is  inferred 
to  be  a  mixture  of  several  different  substances.  Neither  do  the  different 
varieties  of  naphtha  give  similar  results  on  analysis:  they  are  all,  however, 
hydrocarbons,  chiefly  paraffins,  with  smaller  quantities  of  defines  and  aro- 
matic hydrocarbons.  The  use  of  these  substances  in  the  places  where  they 
abound  is  tolerably  extensive ;  they  often  serve  the  inhabitants  for  fuel, 
light,  &c.  To  the  chemist,  pure  naphtha  is  valuable,  as  offering  facilities 
for  the  preservation  of  the  more  oxidable  metals,  as  potassium  and  sodium. 

Among  the  several  naphthas,  the  Burmese  naphtha  (Rangoon  tar)  lias  been 
more  particularly  examined  by  De  la  Rue  and  Miiller.  It  consists  princi- 
pally of  liquid  homologues  of  marsh-gas,  including  solid  paraffin,  associ- 
ated with  small  quantities  of  hydrocarbons  of  the  benzene  series,  and  hy- 
drocarbons analogous  to  colophene.  American  petroleum,  which  has  a 
similar  composition,  but  contains  a  larger  proportion  of  the  homologues 
of  marsh-gas,  has  been  investigated  chiefly  by  Pelouze  and  Cahours  (p. 
47G). 

Retinite,  or  Retinasphalt,  is  a  kind  of  fossil  resin  met  with  in  brown  coal : 
it  has  a  yellow  or  reddish  color,  is  fusible  and  inflammable,  and  readily 
dissolved  in  great  part  by  alcohol.  The  soluble  portion  is  called  retinic 
acid.  Hatchetin  is  a  somewhat  similar  substance  met  with  in  mineral  coal 
at  Merthyr  Tydvil,  and  also  near  Loch  Fyne,  in  Scotland.  Idrialin  is  found 
associated  with  native  cinnabar,  and  is  extracted  from  the  ore  by  oil  of 
turpentine,  in  which  it  dissolves.  It  is  a  white,  crystalline  substance, 
scarcely  volatile  without  decomposition,  but  slightly  soluble  in  alcohol  and 
ether,  and  composed  of  C42H280 :  it  is  generally  associated  with  a  hydro- 
carbon, idryl,  which  contains  C21H,4. 

Ozocerite,  or  fossil  wax,  is  found  in  Moldavia,  in  a  layer  of  bituminous 
shale :  it  is  brownish,  and  has  a  somewhat  pearly  appearance  :  it  is  fusible 
below  100°,  and  soluble  with  difficulty  in  alcohol  and  ether,  but  easily  in 
oil  of  turpentine.  It  appears  to  contain  more  than  one  definite  principle. 

Nefte-degil,  a  substance  resembling  the  former,  occurs  in  immense  quan- 
tities in  the  vicinity  of  the  Caspian  Sea.  Another  compound  of  the  same 
kind  is  found  in  still  larger  quantities  at  Baku,  and  is  called  Kir. 


ALCOHOLS  AND  ETHERS. 

rPHE  term  alcohol,  originally  limited  to  one  substance,  viz.,  spirit  of 
wine,  is  now  applied  to  a  large  number  of  organic  compounds,  many  of 
which,  in  their  external  characters,  exhibit  but  little  resemblance  to  ordi- 
nary alcohol.  They  are  all,  however,  analogously  constituted,  having  the 
composition  of  saturated  hydrocarbons,  in  which  one  or  more  of  the  hy- 
drogen-atoms are  replaced  by  hydroxyl :  they  may,  therefore,  also  be  re- 
garded as  compounds  of  hydroxyl  with  univalent  or  multivalent  hydrocar- 
bon radicals,  hence  called  alcohol  radicals.  Thus,  from  propane,  C3H8,  are 
derived  the  three  alcohols, 

C3H7(OH)  (C3H6)"(OH)2  (C,H5)'"(OH), 

Propyl  Propene  Propenyl 

alcohol.  alcohol.  alcohol. 

Alcohols  are  accordingly  classed  as  monatomic,  diatomic,  triatomic,  &c.,  or, 
generally,  as  monatomic  and  polyatomic,  according  to  the  number  of  equi- 
valents of  hydroxyl  which  they  contain;  or  according  to  the  equivalent 
value  of  their  hydrocarbon  radicals. 

The  replacement,  partial  or  total,  of  the  hydroxyl  in  an  alcohol  by  chlor- 
ine, bromine,  iodine,  or  fluorine,  gives  rise  to  halo'id  ethers;  thus: 

From  C3H7(OH)  are  derived  C3H7C1,  C3H7Br,  &c. 
"     C3H6(OH)2          "  C3H6C10H,  C3H6C12,  &c. 

«      (C3H6)(OH)3       «  C3H5C1(OH)2,  C3H6C12(OH),  C3H6C13, 

C3H5Br2Cl3,  &c. 

These  substitutions  are  effected  by  treating  the  alcohols  with  the  chlor- 
ides, bromides,  and  iodides  of  hydrogen  or  phosphorus ;  thus : 

C2H5(OH)         +  HC1        =        H(OH)        +        C2H6C1 

Ethyl  Hydrogen  Water.  Ethyl 

alcohol.  chloride.  chloride. 

3C2H5(OH)        +  PC13       =        P(OH)3        +        3C2H5C1 

Ethyl  Phosphorous        Phosphorous  Ethyl 

alcohol.  chloride.  acid.  chloride. 

3C2H5(OH)        +  POC13      =       PO(OH)3      +        3C2H5C1 

Ethyl  Phosphorous        Phosphorous  Ethyl 

alcohol.  oxychloride.  acid.  chloride. 

Instead  of  the  bromides  and  iodides  of  phosphorus,  the  elements  phos- 
phorus and  bromine  or  iodine,  in  the  proportions  required  to  form  them, 
are  often  used  in  these  processes. 

These  haloid  ethers  are  also  formed  in  many  instances  by  direct  substi- 
tution of  chlorine,  bromine,  &c.,  for  hydrogen  in  saturated  hydrocarbons, 
as  explained  in  the  preceding  pages. 

The  treatment  of  the  haloid  ethers  with  caustic  aqueous  alkalies  gives 
rise  to  a  substitution  opposite  to  that  exhibited  in  the  above  equations, 
reconverting  the  ethers  into  alcohols,  e.g. : 

C2H6C1        +        KOH        =        KC1        +        C2H5(OH). 

The  replacement  of  the  hydroxyl  in  an  alcohol  by  the  corresponding 


ALCOHOLS    AND    ETHERS.  509 

radicals,  potassoxyl,  OK,  methoxyl,  OCH3,  ethoxyl,  OC2H6,  &c.  (p.  237), — 
or  of  the  hydrogen  in  the  hydroxyl  by  potassium,  methyl,  ethyl,  &c., — 
gives  rise  to  oxygen  ethers;  thus: 

C2H5(OH)  yields  C2H5(OK)         C2H5(OCH3)         C2H5(OC2H5) 

Ethyl  Potassium  Methyl  Ethyl 

alcohol.  ethylate.  ethylate.  ethylate. 

C2H4(OH)2      «      C2H4(OH)(OC2H5)  C2H4(OC2H5), 

Ethene  Monethylic  Diethylic 

alcohol.  ethenate.  ethenate. 

These  substitutions  may  be  effected  in  various  ways.  The  simplest  is 
to  replace  an  .atom  of  hydrogen  in  the  alcohol  by  potassium  or  sodium, 
and  act  on  the  resulting  compound  with  a  haloi'd  ether;  thus: 

2C2H4(OH)2         -f         Na2        =       2C2H4(OH)(ONa)        -f         H2, 
Ethene  Sodium 

alcohol.  ethenate. 

C2H4(OH)(ONa)     +     C2H5I     =     Nal     -f-     C2H4(OH)(OC2H5) 
Sodium  Ethyl          Sodium  Monethylic 

ethenate.  iodide.         iodide.  ethenate. 

In  the  polyatomic  alcohols,  two  equivalents  of  hydroxyl  may  also  be  re- 
placed by  one  atom  of  oxygen,  giving  rise  to  another  class  of  oxygen 
ethers;  thus,  from  ethene  alcohol,  C2H.(OH)2,  is  derived  ethene-oxide, 
C2H40. 

The  replacement  of  the  hydrogen  of  the  hydroxyl  in  an  alcohol  by  acid 
radicals  (p.  469),  produces  ethereal  salts  or  compound  ethers:  thus  from 
methyl  alcohol,  CH3(OH),  are  derived: 

H  0 

Methyl  nitrate,  CH3(ON02),  or  H— C— 0— N 

H          0 
H          OH 

Methyl  acetate,  CH3(OC2H30),  or  H— C— 0— C— C— H 

H  H 

H          0 

Acid  methyl  sulphate,  CH3(OS03H),  or  H— C— 0— S— 0— H 

H  0 


H  0          H 

Neutral  methyl  sulphate,  CH3(OS03CH3),  or   H- 


[_C 

A 


It  is  clear  that  these  ethereal  salts  may  be  derived  from  the  corresponding 
acids  by  substitution  of  alcohol-radicals  for  hydrogen,  being  in  fact  related 
to  the  alcohols  in  the  same  manner  as  metallic  salts  to  metallic  hydrates 
(p.  460).  When  distilled  with  alkalies,  they  are  resolved  into  an  acid  and 
alcohol ;  e.  g. : 
43* 


510  ALCOHOLS   AND   ETHERS. 

C2H6(OC2H30)     +     K(OH)     c=     K(OC2H30)     +     C2H5(OH) 
Ethyl  acetate.  Potassium  Potassium  Ethyl 

hydrate.  acetate.  alcohol. 

The  action  of  haloid  ethers,  or  of  certain  ethereal  salts,  on  the  sulph- 
hydrates  and  sulphides  of  the  alkali-metals,gives  rise  to  alcoholic  sulph-hydralcs 
and  sulphides,  that  is  to  say,  alcohols  and  ethers  containing  sulphur  in  place 
of  oxygen;  thus: 

C2H,C1    4-     KSH     =    KC1     +    C2H,SH 
Ethyl  Ethyl 

chloride.  sulph-hydrate. 

2C2HgOS03K    4-     KSK     =     2KOS03K     +     C2H6SC2H5 
Potassium  ethyl      Potassium      Potassium  Ethyl  sul- 

sulphate.  sulphide.         sulphate.  phide. 

The  alcoholic  sulph-hydrates,or  sulphur-alcohols,are  also  called  mercaptans, 
from  their  property  of  readily  combining  with  mercury  (corpora  mercurio 
apta).  Their  reactions  are  closely  analogous  to  those  of  the  oxygen- 
alcohols. 


MONATOMIC  ALCOHOLS  AND  ETHERS. 
I.  Containing  the  radicals  CnH2n-f,,  homologous  with  Methyl. 

The  alcohols  of  this  series  are  the  best  known  and  most  important  of  all 
this  class  of  bodies.  They  may  be  formed  from  the  corresponding  haloid 
ethers  by  the  action  of  alkalies,  and  several  of  them  are  produced  by  the 
fermentation  of  sugar.  There  are  also  synthetical  processes  by  which  these 
alcohols  may  be  built  up  in  regular  order,  from  the  lowest  upwards  ;  but 
these  will  be  better  understood  further  on. 

The  names  and  formulae  of  the  known  alcohols  of  this  series  are  as  follows  : 

Methyl  alcohol         .....  CH40 

Ethyl  alcohol      ......  C2H60 

Propyl  alcohol         .....  C3H80 

Quartyl  or  Butyl  alcohol     ....  C4H,00 

Quintyl  or  Amyl  alcohol  .         .         .  C5H120 

Sextyl  or  Hexyl  alcohol      ....  C6H140 

Septyl  or  Heptyl  alcohol          .         .         .  C7H]60 

Octyl  alcohol       ......  C8H180 

Nonyl  alcohol  ......  C»H2o° 

Sexdecyl  or  Cetyl  alcohol  ....  C,6H340 

Ceryl  alcohol  ......  C2H60 

Melissyl  alcohol  ...... 


The  first  nine  of  these  alcohols  are  liquid  at  ordinary  temperatures. 
Methyl  and  ethyl  alcohols  are  mobile,  watery  liquids;  the  others  are  more 
or  less  oily,  the  viscidity  increasing  with  the  molecular  weight  ;  cetyl  alcohol 
is  a  solid  fat;  ceryl  and  melissyl  alcohols  are  of  waxy  consistence. 

The  formula  of  methyl  alcohol  is  that  of  methane  or  marsh-gas  having 
one  atom  of  hydrogen  replaced  by  hydroxyl  ;  and  the  rest  may  be  derived 
from  it  by  replacement  of  one  or  more  of  the  other  hydrogen-atoms  by 
methyl  and  its  homologues.  If  we  replace  only  one  atom  of  hydrogen  in 
this  manner  we  obtain  the  series: 


MONATOMIC   ALCOHOLS   AND   ETHERS.  511 

Methyl           Ethyl              Propyl  Quartyl                    Quintyl 

alcohol.         alcohol.           alcohol.  alcohol.                     alcohol. 

(  CH2CH3  (  CH2CH2CH3 

r  )  H  r  )  H 

C1  H  C}  H 

OH  OH 


M  H  ul   H 

(OH  (OH 

Now,  it  is  clear  that,  so  long  as  the  type  of  an  alcohol  is  preserved  — 
that  is,  of  a  hydrocarbon  having  at  least  one  hydrogen-atom  replaced  by 
hydroxyl  —  the  first  two  alcohols  of  this  series  do  not  admit  of  any  other 
mode  of  formulation :  in  other  words,  these  two  bodies  are  not  susceptible 
of  isomeric  modifications.  But  with  regard  to  the  higher  members  of  the 
series  the  case  is  different.  Thus,  to  obtain  the  formula  of  the  three-car- 
bon alcohol,  C3H80,  instead  of  replacing  one  hydrogen-atom  in  methyl 
alcohol  by  ethyl,  we  may  replace  two  hydrogen-atoms  by  methyl,  which 

f  CH3  f  CH2CH8 

1        /~1  TT  1        TT 

will  give  for  this  alcohol  the  formula  C  -I  H  3  instead  of  C  -I  j  ;  and 

(  OH  (  OH 

in  like  manner  for  the  four-carbon  alcohol,  C4H100,  we  obtain  the  three 
modifications : 

Primary.  Secondary. 

f  CH2CH2CH3  f  CH2CH3 

)  H  c  I  CH3 

•j  H  U1  H 

(OH  (OH 

An  alcohol  is  said  to  be  primary,  secondary,  or  tertiary,  according  as  the  car- 
bon-atom which  is  in  combination  with  hydroxyl,  is  likewise  directly  combined  with 
one,  two,  or  three  other  carbon-atoms. 

The  five-carbon  alcohol,  and  those  above  it,  are  likewise  susceptible  of 
the  same  three  modifications,  and  no  more,  inasmuch  as  the  carbon-atom 
combined  with  hydroxyl  has  only  three  other  units  of  equivalency  to  dis- 
pose of. 

There  is  still,  however,  another  kind  of  modification  of  which  the  alco- 
hols of  each  of  these  three  groups  are  susceptible,  arising  from  modifica- 
tions in  the  alcohol  radicals  themselves,  already  noticed  in  connection  with 
the  paraffins  (p.  478).  The  primary  four-carbon  alcohol,  for  example,  may 
be  represented  by  either  of  the  formulas : 

(  CH2CH2CH3  /  CH(CH3)2 

r  )  H  )  H 

u  )  H  u>)  H 

(  OH  (  OH 

Each  of  these  fulfils  the  essential  condition  of  a  primary  alcohol ;  but 
the  first  contains  normal  propyl,  CH2(C2H5),  whereas  the  second  contains 
isopropyl,  CII(Cir3).2;  and  in  the  higher  alcohols  it  is  easy  to  see  that  a 
still  larger  number  of  modifications  may  exist ;  but  only  a  very  few  of  them 
have  hitherto"  been  actually  obtained.  The  methods  of  producing  secondary 
and  tertiary  alcohols,  and  the  differences  of  character  exhibited  by  the 
several  modifications,  will  be  explained  further  on. 


512  ALCOHOLS    AND    ETHERS. 

A  very  convenient  nomenclature  for  these  isomeric  alcohols  has  been 
proposed  by  Kolbe.  Methyl  alcohol,  CH3(OH),  is  called  carbinol ;  and  the 
primary  alcohols  formed  from  it  by  successive  substitution  of  methyl,  ethyl, 
&c.,  for  an  atom  of  hydrogen,  are  named  according  to  the  radicals  which 
they  contain ;  thus, 

Carbinol,  or  Methyl  alcohol  ....  C(OH)H3 

Methyl  carbinol,  or  Ethyl  alcohol  .         .  C(OH)H2CH3 

Ethyl  carbinol,  or  Propyl  alcohol  .         .  C(OH)H2C2H5 

Dimethyl  carbinol,  or  Isopropyl  alcohol         .  C(OH)H(CH3)2 

Propyl  carbinol,  or  Quartyl  alcohol       .          .  C(OH)H2(C3H7) 

Isopropyl  carbinol,  or  Isoquartyl  alcohol      .  C(OH)H2CH(CH3)2 
Methyl-ethyl  carbinol,  or  Secondary  Quartyl 

alcohol C(OH)HCH3C2H6 

Trimethyl   carbinol,  or  Tertiary  Quartyl  al- 
cohol    C(OH)(CH3)3. 


METHYL  ALCOHOL  AND  ETHERS. 

Methyl  Alcohol,  Hydroxymethane,  or  Carbinol,  CH40  or  CH3(OH).  —  Thia 
is  the  simplest  member  of  the  series.  It  is  produced:  1.  From  marsh-gas, 
by  subjecting  that  compound  to  the  action  of  chlorine  in  sunshine,  whereby 
chloromethane,  or  methyl  chloride,  CH3C1,  is  produced,  and  distilling  this 
chloride  with  potash. 

2.  From  wintergreen  oil,  which   consists   chiefly  of  acid  methyl  salicy- 
late,  C7H40  .  H .  CH3,  by  distillation  with  potash,  whereby  potassium  salicy- 
late  is  formed,  and  methyl  alcohol  distils  over : 

C7H403 .  H  .  CH3      -f       KOH       ==       C7H403 .  H  .  K      +       CH8(OH) 
Acid  methyl  Potassium  Acid  potassium 

salicylate.  hydrate.  salicylate. 

This  reaction,  which  consists  in  the  interchange  of  methyl  and  potassium, 
yields  very  pure  methyl  alcohol. 

3.  From  crude  wood-vinegar,  the  watery  liquid  obtained  by  the  destruc- 
tive distillation  of  wood :  it  was  in  this  liquid  that  methyl  alcohol  was  first 
discovered  by   P.Taylor,  in   1812:    hence   it   is  often    called   wood-spirit. 
Crude  wood-vinegar  probably  contains   about  Ti^  part  of  methyl  alcohol, 
which  is  separated  from  the  great  bulk  of  the  liquid  by  subjecting  the 
whole  to  distillation,   and  collecting  apart  the  first  portions  which  pass 
over.     The  acid  solution  thus  obtained  is  neutralized  with  slaked  lime,  and 
the  clear  liquid,  separated  from  the  oil  which  floats  on  the   surface,  and 
from  the  sediment  at  the  bottom  of  the  vessel,  is  again  distilled.     A  vola- 
tile liquid  is  thus    obtained,  which  burns  like  weak  spirit ;  this  may  be 
strengthened  by  rectification,  and  ultimately  rendered  pure  and  anhydrous 
by  careful  distillation  from  quicklime  at  the  heat  of  a  water-bath. 

Pure  methyl  alcohol  is  a  colorless,  thin  liquid,  very  similar  in  smell  and 
taste  to  ethyl  alcohol;  crude  wood-spirit,  on  the  other  hand,  which  contains 
many  impurities,  has  an  offensive  odor  and  a  nauseous,  burning  taste. 
Methyl  alcohol  boils  at  66-6°  C.  (152°  F.),  and  has  a  density  of  0-798  at 
20°  C.  (68°  F.).  Vapor-density  (referred  to  hydrogen)  =  16.  Methyl 
alcohol  when  pure  mixes  in  all  proportions  with  water :  it  dissolves  resins 
and  volatile  oils  as  freely  as  ethyl  alcohol,  and  is  often  substituted  for  ethyl 
alcohol  in  various  proce'sses  in  the  arts,  for  which  purpose  it  is  prepared 
on  a  large  scale.  It  may  be  burnt  instead  of  ordinary  spirit  in  lamps : 
the  flame  is  pale-colored,  like  that  of  ethyl  alcohol,  and  deposits  no  soot. 


METHYL   ALCOHOL   AND   ETHERS.  513 

Methyl  alcohol  dissolves  caustic  baryta:  the  solution  deposits,  by  evapora- 
tion in  a  vacuum,  acicular  crystals,  containing  Ba0.2CH40.  It  dissolves 
calcium  chloride  in  large  quantity,  and  gives  rise  to  a  crystalline  compound 
containing,  according  to  Kane,  CaCl2.2CH40. 

Potassium  and  sodium  dissolve  in  it,  with  evolution  of  hydrogen  yielding 
potassium  and  sodium  methylates  or  methyl  ethers,  CH3OK,  and  CH3ONa. 

By  oxidation,  as  by  exposure  to  the  air  in  contact  with  platinum  black, 
it  is  converted  into  formic  acid,  CH202,  or  CHO .  OH,  which  is  derived  from 
it  by  substitution  of  1  atom  of  oxygen  for  2  atoms  of  hydrogen : 

CH40         -f         02        =        OH2         +         CH202. 

Methyl  Chloride,  or  Chloromethane,  CH3C1,  is  formed,  according  to  Ber- 
thelot,  when  a  mixture  of  equal  volumes  of  methane  (marsh-gas)  and 
chlorine  is  exposed  to  reflected  sunlight.  It  is  more  easily  prepared,  how- 
ever, by  heating  a  mixture  of  2  parts  of  common  salt,  1  part  of  wood- 
spirit,  and  3  parts  of  concentrated  sulphuric  acid.  It  is  a  gaseous  body, 
which  may  be  conveniently  collected  over  water,  as  it  is  but  slightly  soluble 
in  that  liquid.  It  is  colorless ;  has  a  peculiar  odor  and  sweetish  taste,  and 
burns,  when  kindled,  with  a  pale  flame,  greenish  towards  the  edges,  like 
most  combustible  chlorine-compounds.  Its  density,  referred  to  hydrogen 
as  unity,  is  25-25;  it  is  not  liquefied  at  — 18°  C.  (0°  F.).  The  gas  is  decom- 
posed by  transmission  through  a  red-hot  tube,  with  slight  deposition  of 
cai-bon,  into  hydrochloric  acid  gas  and  a  hydrocarbon  which  has  been  but 
little  examined.  By  the  action  of  chlorine  in  sunshine  it  is  successively 
converted  into  methene  chloride,  or  dichloromethane,  CH2C12,  a  liquid  boiling 
at  30-5°  C.  (87°  F.) ;  methenyl  chloride,  trichloromethane,  or  chloroform,  CHC13; 
and  carbon  tetrachloride,  CC14. 

Methyl  Iodide,  or  lodome thane,  CH3I,  is  a  colorless  and  feebly  combustible 
liquid,  obtained  by  distilling  together  1  part  of  phosphorus,  8  of  iodine, 
and  12  or  15  of  wood-spirit.  It  is  insoluble  in  water,  has  a  density  of 
2-237,  and  boils  at  40°  C.  (111°  F.).  The  density  of  its  vapor,  referred  to 
hydrogen  as  unity,  is  71.  When  digested  in  sealed  tubes  with  zinc,  it  yields 
a  colorless  gaseous  mixture  containing  ethane,  or  dimethyl,  C2H6,  and  the 
residue  contains  zinc  iodide,  together  with  zinc  methide,  Zn(CH3)2,  a  very 
volatile  liquid,  which  takes  fire  spontaneously  in  contact  with  the  air: 

2CH3I         -f         Zn         =         ZnI2         -f         C2H6 
2CH3l  Zn2         =         ZnI2         -f         Zn(CH3)2. 

Methyl  Ether,  Methyl  Oxide,   or  Methoxyl-methane,  C2H60  =  (CH3)20 

TT 

=  C  -I  TT-  — This  compound,  which  bears  the  same  relation  to  methyl  alco- 

[OCH3 

hoi  that  anhydrous  potassium  oxide  bears  to  potassium  hydrate,  is  produced 
by  abstraction  of  the  elements  of  water  from  methyl  alcohol:  2CH40  — 
OH2=C2H60. 

To  prepare  it,  1  part  of  wood-spirit  and  4  parts  of  concentrated  sul- 
phuric acid  are  mixed  and  exposed  to  heat  in  a  flask  fitted  with  a  perfo- 
rated cork  and  bent  tube :  the  liquid  slowly  blackens,  and  emits  large  quan- 
tities of  gas,  which  may  be  passed  through  a  little  strong  solution  of  caustic 
potash,  and  collected  over  mercury.  This  is  methyl  ether,  a  permanently 
gaseous  substance,  which  does  not  liquefy  at  — 16°  C.  (3°  F.).  It  is  color- 
less, has  an  ethereal  odor,  and  burns  with  a  pale  and  feebly  luminous  flame. 
Its  specific  gravity  is  1-617  referred  to  air,  or  23  referred  to  hydrogen  as 
unity.  Cold  water  dissolves  about  33  times  its  volume  of  this  gas,  acquiring 
thereby  its  characteristic  taste  and  odor :  on  boiling  the  solution,  the  gas 


514  ALCOHOLS   AND   ETHERS. 

is  again  liberated.  Alcohol,  wood-spirit,  and  concentrated  sulphuric  acid 
dissolve  it  in  still  larger  quantity. 

0 
Methyl  Nitrate,  CH3.N03,  or  CH3.ON02,  or  H3C— 0— N.—  This  ether  is 

0 

obtained  by  distilling  50  grams  of  pounded  nitre  with  50  grams  of  wood- 
spirit  and  ]  00  grams  of  sulphuric  acid,  in  a  retort  without  external  heat- 
ing. It  is  a  colorless  liquid  of  sp.  gr.  1-182  at  20°  C.  (68°  F.) ;  boils  at  66° 
C.  (151°  F.) :  has  a  faint,  ethereal  odor.  Its  vapor  detonates  violently  when 
heated  to  150°  C.  (302°  F.).  Heated  with  alcoholic  ammonia,  it  yields  me- 
thylamine  nitrate,  CH5N.N03H.  Distilled  with  aqueous  potash,  it  yields 
methyl  ether. 

Methyl  Sulphates,  —  Sulphuric   acid  being  a   bibasic   acid,   yields   two 
methyl  ethers  —  one  acid,  the  other  neutral. 

Acid  methylsulphate,  Methyl  and  Hydrogen  sulphate,  Methylsulphuric  acid,  or 

0 

Sulphomethylic  acid,  CH3.H.S04,  or  CH3. OSOaH=H3C— 0— S— OH.—  To 

ft 

prepare  this  acid  ether,  1  part  of  wood-spirit  is  slowly  mixed  with  2  parts 
of  concentrated  sulphuric  acid,  and  the  whole  is  heated  to  ebullition,  and 
left  to  cool,  after  which  it  is  diluted  with  water,  and  neutralized  with 
barium  carbonate.  The  solution  is  filtered  from  the  insoluble  sulphate, 
and  evaporated,  first  in  a  water-bath,  and  afterwards  in  a  vacuum  to  the 
proper  degree  of  concentration.  The  salt  crystallizes  in  beautiful,  square, 
colorless  tables,  containing  (CH3)2Ba//S04. 20H2,  which  effloresce  in  dry 
air,  and  are  very  soluble  in  water.  By  exactly  precipitating  the  base  from 
this  substance  with  dilute  sulphuric  acid,  and  leaving  the  filtered  liquid  to 
evaporate  in  the  air,  methylsulphuric  acid  may  be  procured  in  the  form  of 
a  sour,  syrupy  liquid,  or  in  minute  acicular  crystals,  very  soluble  in  water 
and  alcohol.  It  is  very  instable,  being  easily  decomposed  by  heat.  Potas- 
sium methylsulphate,  CH3KS04,  crystallizes  in  small,  nacreous,  deliquescent 
rhombic  tables.  The  lead-salt  is  also  very  soluble. 

"    Neutral  Methyl  sulphate,  or  Dimethylic  sulphate,  (CH3)3S04,  or  CH3  .  OS03 
0 

CH3,  or   H3C— 0— S— 0— CH3.— This   ether  is  prepared    by   distilling   1 


part  of  wood-spirit  with  8  or  10  parts  of  strong  oil  of  vitriol;  the  dis- 
tillation may  be  carried  nearly  to  dryness.  The  oleaginous  liquid  found 
in  the  receiver  is  agitated  with  water,  and  purified  by  rectification  from 
powdered  caustic  baryta.  The  product  is  a  colorless,  oily  liquid,  of  alli- 
aceous odor,  having  a  density  of  1-324,  and  boiling  at  188°  C.  (370°  F.). 
It  is  neutral  to  test  paper,  and  insoluble  in  water,  but  decomposed  by  that 
liquid,  slowly  in  the  cold,  rapidly  and  with  violence  at  a  boiling  tempera- 
ture, into  methylsulphuric  acid  and  wood-spirit.  Anhydrous  lime  and 
baryta  have  no  action  on  this  ether :  their  hydrates,  however,  and  those 
of  potassium  and  sodium,  decompose  it  instantly,  with  production  of  a 
methylsulphate  of  the  base,  and  methyl  alcohol.  When  neutral  methyl- 
sulphate  is  heated  with  common  salt,  it  yields  sodium  sulphate  and  methyl 
chloride ;  with  mercuric  cyanide,  or  potassium  cyanide,  it  gives  a  sulphate 


ETHYL    ALCOHOL.  515 

of  the  base,  and  methyl  cyanide ;  with  dry  sodium  formate,  it  yields  sodium 
sulphate  and  methyl  formate 

Methyl  Borate,  (CH3)3B03  =  B///(OCH3)3,  is  formed  by  the  action  of 
gaseous  boron  chloride  on  anhydrous  methyl  alcohol.  It  is  a  limpid  liquid, 
of  specific  gravity  0-9551  at  0°,  boiling  at  72°  C.  (162°  F.).  Water  decom- 
poses it  into  boric  acid  and  methyl  alcohol. 

Methyl  Phosphates. — Two  methyl  phosphates  have  been  obtained,  viz., 
methylphosphoric  acid,  (PO)///(OH).,(OCH3),  and  dimethylphosphoric  acid, 
(PO)///(OH)(OCH3)2.  They  are  formed  by  the  action  of  phosphorus  oxy- 
chloride  on  methyl  alcohol  under  different  circumstances. 

Methyl  Silicate,  SiiT(OCH3)4,  is  obtained  by  acting  upon  perfectly  pure 
and  dry  methyl  alcohol  with  silicium  tetrachloride,  and  distilling  the  pro- 
duct. It  is  a  colorless  liquid,  of  pleasant,  ethereal  odor,  specific  gravity 
1-0539  at  0°,  distilling  between  121°  and  126°  C.  (250°-258°  F.).  It  dis- 
solves with  moderate  facility  in  water,  and  the  solution  does  not  become 
turbid  from  separation  of  silica  for  some  weeks.  Its  observed  vapor-den- 
sity is  5  38  referred  to  air,  or  312  referred  to  hydrogen,  the  calculated 
number  being  304. 

Hexmethijl-disilidc  ether,  (CH3)6Si20T,  or  SiiT20(OCH3)6,  is  produced,  to- 
gether with  the  compound  last  described,  when  the  methyl  alcohol  used  is 
not  quite  dry.  It  boils  at  201°  to  202-5°  C.  (294°-295°  F.),  and  has  a  density 
of  1-1441  at  0°.  In  other  respects  it  resembles  the  preceding. 

Methyl  Sulph-hydrate,  CH3SH,  also  called  Methyl  Mercaptan.— This  com- 
pound, which  has  the  composition  of  methyl  alcohol  with  the  oxygen  re- 
placed by  sulphur,  is  formed  by  distilling  in  a  water-bath,  with  efficient 
condensation,  a  mixture  of  calcium  methylsulphate  and  potassium  sulph- 
hydrate: 

(S04)2(CH3)2Ca//  -f  2KSH  =  S04K2  +  S04Ca  +  2CH3SH. 

It  is  a  liquid  lighter  than  water,  and  having  an  extremely  offensive  odor. 
It  forms  wic.h  lead-acetate  a  yellow  precipitate,  and  with  mercuric  oxide  a 
white  compound,  (CH3)2S2Hg//,  which  crystallizes  from  alcohol  in  shining 
laminae. 

Methyl  Sulphide,  S(CH3)2,  or  H3CSCH3,  is  obtained  by  passing  gaseous 
methyl  chloride  into  a  solution  of  potassium  monosulphide  in  wood-spirit. 
It  is  a  colorless,  mobile,  fetid  liquid,  of  specific  gravity  0-845  at  21°  C. 
(7(5°  F.),  boiling  at  41°  C.  (106°  F.).  It  forms  several  substitution-pro- 
ducts with  chlorine. 

Methyl  Bisulphide,  (CH3)2S2,  is  prepared  by  passing  gaseous  methyl  chlor- 
ide through  an  alcoholic  solution  of  potassium  bisulphide.  It  is  a  limpid, 
strongly  refracting  liquid,  having  a  specific  gravity  of  1-046  at  18°,  and  an 
intolerable  odor  of  onions;  boils  between  116°  and  118°.  It  forms  substi- 
tution-products with  bromine  and  chlorine. 

By  substituting  pentasulphide  for  bisulphide  of  potassium  in  the  preced- 
ing preparation,  a  trisulphide  of  methyl,  (CH3)2S3,  is  obtained,  boiling  at 
about  200°, 


ETHYL  ALCOHOL  AND  ETHERS. 

Ethyl  Alcohol,  Hydroxyl-ethane,  or  Methyl  Carbinol, 

CH3 
C2TT60  =  C2H5(OH)     =       | 

CH2(OH) 


516  ALCOHOLS   AND   ETHERS. 

This  important  compound,  the  oldest  and  best  known  of  the  whole  group 
of  alcohols,  and  generally  designated  by  the  simple  name  "alcohol,"  is 
produced : 

1.  From  ethene,   C2H4,   by  addition  of  the  elements  of  water.     When 
ethene  gas  and  strong  sulphuric  acid  are  violently  agitated  together  for  a 
long  time,  the  gas  is  absorbed,  and  ethylsulphuric   acid,  C2H6S04,  is  pro- 
duced ;  and  this  compound,  distilled  with  water,  yields  sulphuric  acid  and 
ethyl  alcohol: 

C2H6S04      +       OH2      =      S04H2      +       C2H60. 

Now  we  have  seen  that  ethene  can  be  formed  by  addition  of  hydrogen 
to  ethine,  C2H2,  which  is  itself  formed  by  direct  combination  of  carbon  and 
hydrogen.  It  follows,  therefore,  that  alcohol  can  be  produced  syntheti- 
cally from  its  elements. 

2.  By  the  fermentation  of  certain  kinds  of  sugar.     When  a  moderately 
warm  solution  of  cane-sugar  or  grape-sugar   (glucose)  is  mixed  with  cer- 
tain albuminous  matters,  as  blood,  white  of  egg,  flour-paste,  and  especially 
beer-yeast,  in  a  state  of  decomposition,  a  peculiar  process,  called  fermenta- 
tion, is  set  up,  by  which  the  sugar  is  resolved  into  ethyl  alcohol  and  carbon 
dioxide.     In  the  case  of  glucose,  these  products  result  from  a  simple  split- 
ting up  of  the  molecule  : 

C6HW0,        =         2C02        +        2C2H60. 

Glucose.  Carbon  Alcohol 

dioxide. 

Cane  sugar,  C,2H12Oj,,  is  first  converted  into  glucose  by  assumption  of 
water  (Ci2H22Ou  -j-  OH2  =  2C6H1206),  and  the  latter  is  then  decomposed  as 
above.* 

If  ordinary  cane-sugar  be  dissolved  in  a  large  quantity  of  water,  a  due 
proportion  of  active  yeast  added,  and  the  whole  maintained  at  a  tempera- 
ture of  21°-26°  C.  (70°-80°  F.),  the  change  will  go  on  with  great  rapidity. 
The  gas  disengaged  is  nearly  pure  carbon  dioxide :  it  is  easily  collected 
and  Examined,  as  the  fermentation,  once  commenced,  proceeds  perfectly 
well  in  a  close  vessel,  such  as  a  large  bottle  or  flask  fitted  with  a  cork  and 
a  conducting-tube.  When  the  effervescence  is  at  an  end,  and  the  liquid 
has  become  clear,  it  will  yield  alcohol  by  distillation. 

The  spirit  first  obtained  by  distilling  a  fermented  saccharine  liquid  is 
very  weak,  being  diluted  with  a  large  quantity  of  water.  By  a  second  dis- 
tillation, in  which  the  first  portions  of  the  distilled  liquid  are  collected 
apart,  it  may  be  greatly  strengthened :  the  whole  of  the  water  cannot, 
however,  be  thus  removed.  The  strongest  rectified  spirit  of  wine  of  com- 
merce has  a  density  of  about  0-835,  and  yet  contains  13  or  14  per  cent,  of 
water.  Pure  or  absolute  alcohol  may  be  obtained  from  it  by  redistilling  it 
with  half  its  weight  of  fresh  quicklime.  The  lime  is  reduced  to  coarse 
powder,  and  put  into  a  retort ;  the  alcohol  is  added,  and  the  whole  mixed 
by  agitation.  The  neck  of  the  retort  is  securely  stopped  with  a  cork  and 
the  mixture  left  for  several  days.  The  alcohol  is  distilled  off  by  the  heat 
of  a  water-bath. 

Pure  alcohol  is  a  colorless,  limpid  liquid,  of  pungent  and  agreeable  taste 
and  odor;  its  specific  gravity,  at  15-5° C.  (60°  F.),  is  0-7938,  and  that  of  its 
vapor  referred  to  air,  1-613.  It  is  very  inflammable,  burning  with  a  pale- 
bluish  flame,  free  from  smoke ;  it  has  never  been  frozen.  Alcohol  boils  at 
78-4°  C.  (173°  F.)  when  in  the  anhydrous  state  ;  in  a  diluted  state  the  boil- 

*  Side  by  side  with  this  principal  decomposition,  a  variety  of  other  changes  are  simultane- 
ously accomplished.  According  to  Pasteur,  glycerine,  succinic  acid,  cellulose,  fats,  and  occa- 
sionally lactic  acid,  are  observed  among  the  products  of  alcoholic  fermentation.  Some  of  the 
homologues  of  ethyl  alcohol  are  also  found  amoqg  the  products. 


ETHYL   ALCOHOL. 


517 


ing  point  is  higher,  being  progressively  raised  by  each  addition  of  water. 
In  the  act  of  dilution  a  contraction  of  volume  occurs,  and  the  temperature 
of  the  mixture  rises  many  degrees  :  this  takes  place  not  only  with  pure 
alcohol,  but  also  with  rectified  spirit.  Alcohol  is  iniscible  with  water  in 
all  proportions,  and,  indeed,  has  a  great  attraction  for  the  latter,  absorb- 
ing its  vapor  from  the  air,  and  abstracting  the  moisture  from  membranes 
and  other  similar  substances  immersed  in  it.  The  solvent  powers  of  alco- 
hol are  very  extensive  :  it  dissolves  a  great  number  of  saline  compounds, 
and  likewise  a  considerable  proportion  of  potash.  With  some  salts  it 
forms  definite  crystalline  compounds,  called  alcoholates  :  with  zinc  chloride, 
ZnCl2  .  2C2H60  ;  with  calcium  chloride,  CaCl2  .  4C2II6O  ;  with  magnesium  ni- 
trate, (N08)3Mg  .  6C2H60.  Alcohol  dissolves,  moreover,  many  organic  sub- 
stances, as  the  vegeto-alkalies,  resins,  essential  oils,  and  various  other 
bodies  :  hence  its  great  use  in  chemical  investigations  and  in  several  of  the 
arts. 

Potassium  and  sodium  dissolve  in  ethyl  alcohol  in  the  same  manner  as  in 
methyl  alcohol,  forming  the  compounds  C2H5KO  and  C2H5NaO. 

Alcohol,  passed  through  a  red-hot  tube,  is  resolved  into  marsh-gas,  hy- 
drogen, and  carbon  monoxide  : 


C2H60     = 


H 


CO. 


Small  quantities  of  ethene,  benzene,  and  naphthalene  are,  however,  formed 
at  the  same  time  by  the  mutual  action  of  these  primary  products,  and  car- 
bon is  deposited. 

By  oxidation,  alcohol  is  converted,  first,  into  aldehyde,  then  into  acetic 
acid: 


H60 

johol 


Alcohol. 


+ 


OH, 


C2H40, 
Aldehyde. 


C2H40       -f       0      ==      C2H402 
Aldehyde.  Acetic  acid. 

Chlorine  gas  is  rapidly  absorbed  by  anhydrous  alcohol,  imparting  to  it  a 
yellow  color,  and  causing  considerable  rise  of  temperature.  At  the'  same 
time  it  rapidly  abstracts  hydrogen,  which  is  partly  replaced  by  the  chlo- 
rine, producing  hydrochloric  acid,  aldehyde,  acetic  acid,  ethyl  acetate, 
ethyl  chloride,  and  finally  chloral.  The  mixture  of  these  substances,  freed 
by  water  from  the  soluble  constituents,  was  formerly  called  heavy  muriatic 
'ether.  The  formation  of  the  several  products  is  represented  by  the  follow- 
ing equations  : 


C2H60 
Alcohol. 


Alcohol. 

C2H60 
Alcohol. 

C2H60 
Alcohol. 


Alcohol. 


-f-  C12      =      2HC1 

-f          4C12      =      5HC1 


C2H40, 
Aldehyde. 

C2HC130, 
Chloral. 


HC1      =      OH2      -f     C2H5C1, 

Ethyl  chloride. 


Acetic  acid. 


=      4IIC1 


=       OH, 


Acetic  acid. 

C2H302.C2H6. 
Ethyl  acetate. 


When  the  action  of  the  chlorine  is  continued  for  a  long  time,  chloral  is 
always  the  principal  product.     This  compound  is  a  heavy  oily  liquid,  having 
the  composition  of  aldehyde  with  3  atoms  of  hydrogen  replaced  by  chlorine ; 
44 


518  ALCOHOLS   AND   ETHERS. 

but  it  cannot  be  formed  by  the  direct  action  of  chlorine  upon  aldehyde. 
When  alcohol  containing  water  is  used,  scarcely  any  chloral  is  obtained, 
the  chief  product  being  aldehyde. 

Chlorine,  in  presence  of  alkalies,  converts  alcohol  into  chloroform  and 
carbon  dioxide: 

C2H60     -f     4C12     +     OH2    =    C02    +     5HC1     -f-     CHC13. 
Alcohol.  Chloro- 

form. 

The  same  products  are  formed  by  distilling  dilute  alcohol  with  bleaching 
powder. 

Aqueous  alcohol  heated  with  strong  sulphuric  acid  is  converted  into  ethyl- 
sulphuric  acid,  C2H6SO.,,  or  C2H5(OS03H),  (p.  526) ;  but  when  anhydrous 
alcohol  is  exposed  to  the  vapor  of  sulphuric  oxide,  S03,  a  white  crystalline 
substance  is  formed,  called  ethionic  oxide,  formerly  sulphate  of  carbyl, 
C2H4S206.  This,  when  dissolved  in  water  or  in  aqueous  alcohol,  is  converted 
into  ethionic  acid,  C2H6S207,  a  bibasic  acid,  which  forms  a  soluble  barium 
salt.  Lastly,  a  solution *of  ethionic  acid,  when  boiled,  is  resolved  into  sul- 
phuric acid  and  isethionic  acid,  an  acid  isomeric  with  ethylsulphuric  acid 
(p.  527). 


Commercial  Spirit,  Wine,  Beer,  $c.  Vinous  Fermentation. — The  strength  of 
commercial  spirit,  when  free  from  sugar  and  other  substances  added  sub- 
sequent to  distillation,  is  inferred  from  its  density:  a  table  exhibiting  the 
proportions  of  real  alcohol  and  water  in  spirits  of  different  densities  will 
be  found  at  the  end  of  the  volume.  The  excise  proof  spirit  has  a  sp.  gr. 
of  0-9198  at  60°  F.,  and  contains  49J  per  cent,  by  weight  of  real  alcohol. 

The  high  duty  on  spirits  of  wine  in  this  country  has  hitherto  interfered 
with  the  development  of  many  branches  of  industry,  which  are  dependent  on 
the  free  use  of  this  important  liquid.  The  labors  of  the  scientific  chemist  have 
been  likewise  often  checked  by  this  inconvenience.  A  remedy  for  the  evil 
has  been  supplied  in  Great  Britain  by  a  very  important  measure,  proposed 
and  carried  out  by  the  late  Mr.  John  Wood,  Chairman  of  the  Board  of  Inland 
Revenue.  This  measure  consists  in  issuing  for  manufacturing  and  scientific 
purposes,  duty  free,  a  mixture  of  90  per  cent,  of  spirits  of  wine  of  not  less 
strength  than  corresponds  to  a  density  of  0-830,  with  10  per  cent,  of  partially 
purified  wood-spirit,  which  is  now  sold  by  licensed  dealers  under  the  name 
of  Methylated  Spirit.  It  appears  that  a  mixture  of  this  kind  is  rendered  per- 
manently unfit  for  human  consumption,  the  separation  of  the  two  substances, 
in  consequence  of  their  close  analogy,  being  not  only  difficult,  but  to  all 
appearance  impossible:  at  the  same  time,  and  for  the  same  reasons,  this 
mixture  is  not  materially  impaired  for  the  greater  number  of  the  more 
valuable  purposes  in  the  arts  to  which  spirits  are  usually  employed.  Methyl- 
ated spirit  may  be  used,  instead  of  pure  spirit,  as  a  solvent  of  resinous 
substances,  and  of  many  chemical  preparations,  especially  of  the  alkaloids 
and  other  organic  products.  It  may  be  used  for  the  production  of  fulmi- 
nating mercury,  ether,  chloroform,  iodoform,  olefiant  gas,  and  all  its  de- 
rivatives—  in  fact,  for  an  endless  number  of  laboratory  purposes.  Mythyl- 
ated  spirit  may  also  be  substituted  for  pure  spirit  of  wine  in  the  preser- 
vation of  anatomical  preparations.  The  introduction  of  this  spirit  has 
already  exerted  a  very  beneficial  effect  upon  the  development  of  organic 
chemistry  in  that  country.* 

*  See  Report  on  the  Supply  of  Spirits  of  Wine,  free  from  duty,  for  use  in  the  Arts  and  Manu- 
factures, addressed  to  the  Chairman  of  Inland  Revenue,  by  Professors  Graham,  Hofinann,  and 
Kedwood.  (Quarterly  Journal  of  Chemical  Society,  vol.  via",  p.  120. 


WINE  —  BEER.  519 

Wine,  beer,  &c.,  owe  their  intoxicating  properties  to  the  alcohol  they  con- 
tain, the  quantity  of  which  varies  very  much.  Port  and  sherry,  and  some 
other  strong  wines,  contain,  according  to  Mr.  Brande,  from  19  to  25  per 
cent,  of  alcohol,  while  in  the  lighter  Avines  of  France  and  Germany  it  some- 
times falls  as  low  as  12  per  cent.  Strong  ale  contains  about  10  per  cent. ; 
ordinary  spirits,  as  brandy,  gin,  whiskey,  40  to  50  per  cent.,  or  occasionally 
more.  These  latter  owe  their  characteristic  flavors  to  certain  essential  oils, 
present  in  very  small  quantity,  either  generated  in  the  act  of  fermentation 
or  purposely  added. 

In  making  wine,  the  expressed  juice  of  the  grape  is  simply  set  aside  in 
large  vats,  where  it  undergoes  spontaneously  the  necessary  change.  The 
vegetable  albumin  of  the  juice  absorbs  oxygen  from  the  air,  runs  into  de- 
composition, and  in  that  state  becomes  a  ferment  to  the  sugar,  which  is 
gradually  converted  into  alcohol.  If  the  sugar  be  in  excess,  and  the 
azotized  matter  deficient,  the  resulting  wine  remains  sweet;  but  if,  on  the 
other  hand,  the  proportion  of  sugar  be  small  and  that  of  albumen  large,  a 
dry  wine  is  produced.  When  the  fermentation  stops,  and  the  liquor  becomes 
clear,  it  is  drawn  off  from  the  lees,  and  transferred  to  casks,  to  ripen  and 
improve. 

The  color  of  red  wine  is  derived  from  the  skins  of  the  grapes,  which  in 
such  cases  are  left  in  the  fermenting  liquid.  Effervescent  wines,  as  cham- 
pagne, are  bottled  before  the  fermentation  is  complete ;  the  carbonic  acid 
is  disengaged  under  pressure,  and  retained  in  solution  in  the  liquid.  A 
certain  quantity  of  sugar  is  frequently  added.  The  process  requires  much 
delicate  management. 

During  the  fermentation  of  the  grape-juice,  or  must,  a  crystalline,  stony 
matter,  called  argol,  is  deposited.  This  consists  chiefly  of  acid  potassium 
tartrate  with  a  little  coloring  matter,  and  is  the  source  of  all  the  tartaric 
acid  met  with  in  commerce.  The  salt  in  question  exists  in  the  juice  in  con- 
siderable quantity ;  it  is  but  sparingly  soluble  in  water,  but  still  less  so  in 
dilute  alcohol :  hence,  as  the  fermentation  proceeds,  and  the  quantity  of 
spirit  increases,  it  is  slowly  deposited.  The  acid  of  the  juice  is  thus  re- 
moved as  the  sugar  disappears.  It  is  this  circumstance  which  renders 
grape-juice  alone  fit  for  making  good  wine ;  when  that  of  gooseberries  or 
currants  is  employed  as  a  substitute,  the  malic  and  citric  acids  which  these 
fruits  contain  cannot  be  thus  withdrawn.  There  is  then  no  other  resource 
but  to  add  sugar  in  sufficient  quantity  to  mask  and  conceal  the  natural 
acidity  of  the  liquor.  Such  wines  are  necessarily  acescent,  prone  to  a 
second  fermentation,  and,  to  many  persons,  at  least,  very  unwholesome. 

Beer  is  a  well-known  liquor,  of  great  antiquity,  prepared  from  germi- 
nated grain,  generally  barley,  and  is  used  in  countries  where  the  wine  does 
not  flourish.  The  operation  of  malting  is  performed  by  steeping  the  barley 
in  water  until  the  grains  become  swollen  and  soft,  then  piling  it  in  a  heap 
or  couch,  to  favor  the  elevation  of  temperature  caused  by  the  absorption  of 
oxygen  from  the  air,  and  afterwards  spreading  it  upon  a  floor,  and  turning 
it  over  from  time  to  time  to  prevent  unequal  heating.  When  germination 
has  proceeded  far  enough,  the  vitality  of  the  seed  is  destroyed  by  kiln- 
drying.  During  this  process,  a  peculiar  nitrogenous  substance  called 
diastase  is  produced,  which  acts  as  a  ferment  on  the  starch  of  the  grain, 
converting  a  portion  of  it  into  sugar  and  rendering  it  soluble. 

In  brewing,  the  crushed  malt  is  infused  in  water  at  about  77°  C.  (170°  F.), 
and  the  mixture  is  left  to  stand  during  the  space  of  two  hours  or  more. 
The  easily  soluble  diastase  has  thus  an  opportunity  of  acting  upon  the  un- 
altered starch  of  the  grain,  and  changing  it  into  dextrin  and  sugar.  The  clear 
liquor,  or  wort,  strained  from  the  exhausted  malt,  is  next  pumped  up  into 
a  copper  boiler,  and  boiled  with  the  requisite  quantity  of  hops,  to  com- 
municate a  pleasant  bitter  flavor,  and  confer  on  the  beer  the  property  of 


520  ALCOHOLS   AND   ETHERS. 

keeping  without  injury.  The  flowers  of  the  hop  contain  a  bitter,  resinous 
principle,  called  lupulin,  and  an  essential  oil. 

When  the  wort  has  been  sufficiently  boiled,  it  is  drawn  from  the  copper, 
and  cooled  as  rapidly  as  possible,  to  near  the  ordinary  temperature  of  the 
air,  in  order  to  avoid  an  irregular  acid  fermentation,  to  which  it  would 
otherwise  be  liable.  It  is  then  transferred  to  the  fermenting  vessels,  which 
in  large  breweries  are  of  great  capacity,  and  mixed  with  a  quantity  of 
yeast,  the  product  of  a  preceding  operation,  by  which  the  change  is  speedily 
induced.  This  is  the  most  critical  part  of  the  whole  operation,  and  one  in 
which  the  skill  and  judgment  of  the  brewer  are  most  called  into  play.  The 
process  is  in  some  measure  under  control  by  attention  to  the  temperature 
of  the  liquid  ;  and  the  extent  to  which  the  change  has  been  carried  is  easily 
known  by  the  diminished  density,  or  attenuation  of  the  wort.  The  fermenta- 
tion is  never  suffered  to  run  its  full  course,  but  is  always  stopped  at  a  par- 
ticular point,  by  separating  the  yeast,  and  drawing  off  the  beer  into  casks. 
A  slow  and  almost  insensible  fermentation  succeeds,  which  in  time  renders 
the  beer  stronger  and  less  sweet  than  when  new,  and  charges  it  with  car- 
bonic acid. 

Highly  colored  beer  is  made  by  adding  to  the  malt  a  small  quantity  of 
strongly  dried  or  charred  malt,  the  sugar  of  which  has  been  changed  to 
caramel ;  porter  and  stout  are  so  prepared. 

The  yeast  of  beer  is  a  very  remarkable  substance,  and  has  excited  much 
attention.  To  the  naked  eye  it  is  a  greenish-yellow  soft  solid,  nearly  in- 
soluble in  water,  and  dries  up  to  a  pale-brownish  mass,  which  readily 
putrefies  when  moistened,  and  becomes  offensive.  Under  the  microscope 
it  exhibits  a  kind  of  organized  appearance,  being  made  up  of  little  trans- 
parent globules,  which  sometimes  cohere  in  clusters  or  strings,  like  some 
of  the  lowest  members  of  the  vegetable  kingdom.  Whatever  may  be  the 
real  nature  of  the  substance,  no  doubt  can  exist  that  it  is  formed  from  the 
soluble  azotized  portion  of  the  grain  during  the  fermentative  process.  No 
yeast  is  ever  produced  in  liquids  free  from  azotized  matter ;  that  added  for 
the  purpose  of  exciting  fermentation  in  pure  sugar  is  destroyed,  and  ren- 
dered inert  thereby.  When  yeast  is  deprived,  by  straining  and  strong 
pressure,  of  as  much  water  as  possible,  it  may  be  kept  in  a  cool  place,  with 
unaltered  properties,  for  a  long  time ;  otherwise  it  speedily  spoils. 

The  distiller,  who  prepares  spirits  from  grain,  makes  his  wort,  or  wash, 
much  in  the  same  manner  as  the  brewer ;  he  uses,  however,  with  the  malt 
a  large  quantity  of  raw  grain,  the  starch  of  which  suffers  conversion  into 
sugar  by  the  diastase  of  the  malt,  which  is  sufficient  for  his  purpose.  He  does 
not  boil  his  infusion  with  hops,  but  proceeds  at  once  to  the  fermentation, 
which  he  pushes  as  far  as  possible  by  large  and  repeated  doses  of  yeast. 
Alcohol  is  manufactured  in  many  cases  from  potatoes.  The  potatoes  are 
ground  to  pulp,  mixed  with  hot  water  and  a  little  malt,  to  furnish  diastase, 
made  to  ferment,  and  then  the  fluid  portion  is  distilled.  The  potato-spirit 
is  contaminated  by  a  very  offensive  volatile  oil,  again  to  be  mentioned :  the 
crude  product  from  corn  contains  a  substance  of  a  similar  kind.  The  busi- 
ness of  the  rectifier  consists  in  removing  or  modifying  these  volatile  oils, 
and  in  replacing  them  by  others  of  a  more  agreeable  character. 

In  making  bread,  the  vinous  fermentation  plays  an  important  part :  the 
yeast  added  to  the  dough  converts  the  small  portion  of  sugar  the  meal  nat- 
urally contains  into  alcohol  and  carbonic  acid.  The  gas  thus  disengaged 
forces  the  tough  and  adhesive  materials  into  bubbles,  which  are  still  further 
expanded  by  the  heat  of  the  oven,  which  at  the  same  time  dissipates  the 
alcohol:  hence  the  light  and  spongy  texture  of  all  good  bread.  The  use 
of  leaven  is  of  great  antiquity :  this  is  merely  dough  in  a  state  of  incipient 
putrefaction.  When  mixed  with  a  large  quantity  of  fresh  dough,  it  excites 
in  the  latter  the  alcoholic  fermentation,  in  the  same  manner  as  yeast,  but 


VINOUS    FERMENTATION.  521 

less  perfectly ;  it  is  apt  to  communicate  a  disagreeable  sour  taste  and  odor. 
Sometimes  carbonate  of  ammonia  is  employed  to  lighten  the  dough,  being 
completely  volatilized  by  the  high  temperature  of  the  oven.  Bread  is  now 
sometimes  made  by  mixing  a  little  hydrochloric  acid  and  sodium  carbonate 
in  the  dough  ;  if  proper  proportions  be  taken  and  the  whole  thoroughly 
mixed,  the  operation  appears  to  be  very  successful. 

Another  mode  of  bread-making,  now  practised  on  a  large  scale  with  great 
success,  is  that  invented  by  the  late  Dr.  Dauglish,  which  consists  in  agitat- 
ing the  dough  in  a  strong  vessel  with  water  saturated  under  pressure  with 
carbonic  acid  gas.  When  the  dough  thus  treated  is  subsequently  released 
from  this  pressure  and  exposed  to  the  air,  the  gas  escapes  in  bubbles,  and 
lightens  the  mass  as  effectually  as  that  evolved  within  its  substance  by  fer- 
mentation. The  bread  thus  made,  called  "aerated  bread,"  is  of  excellent 
quality,  not  being  subject  to  the  deterioration  which  so  frequently  takes 
place  in  ordinary  bread,  when  the  fermentation  is  allowed  to  go  too  far. 

Vinous  fermentation,  that  is  to  say  the  conversion  of  sugar  into  alcohol  and 
carbon  dioxide,  never  takes  place  except  in  presence  of  some  nitrogenous 
body  of  the  albuminoid  class  in  a  state  of  decomposition  (p.  463).  The 
manner  in  which  these  bodies  act  in  inducing  fermentation  is  very  obscure  : 
they  neither  add  anything  to  the  sugar  nor  take  anything  from  it ;  but  the 
motion  or  disturbance  of  their  particles,  while  undergoing  putrefaction,  is 
supposed  to  be  communicated  to  the  particles  of  the  sugar  with  which  they 
are  in  contact,  and  thus  to  induce  the  decomposition  above  mentioned; 
hence  such  bodies  are  called  ferments.  There  are  other  modes  of  fermen- 
tation, which  sugar  and  substances  allied  to  it  are  capable  of  undergoing, 
and  the  particular  change  induced  varies  with  the  kind  of  ferment  present: 
thus  vinous  fermentation  is  induced  with  peculiar  facility  by  yeast;  lactous 
fermentation,  or  the  conversion  of  sugar  into  lactic  .acid,  by  putrefying 
cheese.  Another  very  remarkable  circumstance  connected  with  fermenta- 
tion is  that  it  is  always  accompanied  by  the  development  of  certain  minute 
living  organisms — fungi  and  infusoria — like  those  already  mentioned  as 
existing  in  yeast.  So  constantly  indeed  is  this  the  case,  that  many  chem- 
ists and  physiologists  regard  these  organisms  as  the  exciting  cause  of  fer- 
mentation and  putrefaction ;  and  this  view  appears  to  be  corroborated  by 
the  fact  that  each  particular  kind  of  fermentation  takes  place  most  readily 
in  contact  with  a  certain  living  organism,  or  at  least  with  nitrogenous  mat- 
ter containing  it;  thus  beer-yeast  contains  two  species  of  fungus,  called 
.Torvula  cerevisix  and  Penicillium  glaucum,  the  cells  of  which  are  of  very  dif- 
ferent sizes,  so  that  they  may  be  separated  by  filtering  an  infusion  of  the 
yeast,  the  larger  cells  of  the  Torvula  remaining  on  the  filter,  while  those  of 
the  Penicillium,  which  are  much  smaller,  pass  through  with  the  liquid. 
Now,  it  is  found  that  the  residue  on  the  filter  brings  a  solution  of  sugar 
into  the  state  of  vinous  fermentation,  whereas  the  filtered  liquid  induces 
lactous  fermentation.  But  whether  this  effect  is  due  to  the  fungi  them- 
selves, or  to  the  peculiar  state  of  the  albuminous  matter  in  which  they  oc- 
cur, is  a  question  not  yet  decided.  The  investigation  is  attended  with 
peculiar  difficulties,  arising  chiefly  from  the  universal  diffusion  of  the  germs 
of  these  minute  organisms,  which  are  present  not  only  in  all  decaying  albu- 
minous matter,  and  on  the  skins  of  fruits,  leaves,  and  other  parts  of  plants, 
but  are  likewise  diffused  through  the  air ;  so  that  in  experiments  made  for 
the  purpose  of  ascertaining  whether  fermentation  can  take  place  without 
them,  it  is  extremely  difficult  to  insure  their  complete  exclusion  from  the 
substances  under  examination.* 

See  the  article  "  Fermentation,"  in  Watts's  Dictionary  of  Chemistry,  vol.  ii.  p.  6'23. 


522  ALCOHOLS   AND    ETHERS. 


ET  HYLIC  ETHERS. 

fCH3 
Ethyl   Chloride,   or  Chlorethane,   C2H5C1,  or   C  4  H2  ,  often  called  Hy- 

(ci 

drochloric  ether. — To  prepare  this  compound,  rectified  spirit  of  wine  is 
saturated  with  dry  hydrochloric  acid  gas,  and  the  product  distilled  with 
very  gentle  heat;  or  a  mixture  of  3  parts  oil  of  vitriol  and  2  parts  of  alco- 
hol is  poured  upon  4  parts  of  dry  common  salt  in  a  retort,  and  heat  applied  ; 
in  either  case  the  vapor  of  the  hydrochloric  ether  should  be  conducted 
through  a  little  tepid  water  in  a  wash-bottle,  and  then  conveyed  into  a 
small  receiver  surrounded  by  ice  and  salt.  It  is  purified  from  adhering 
water  by  contact  with  a  few  fragments  of  fused  calcium  chloride.  Hydro- 
chloric ether  is  a  thin,  colorless,  and  excessively  volatile  liquid,  of  a  pene- 
trating, aromatic,  and  somewhat  alliaceous  odor.  At  the  freezing  point  of 
water,  its  sp.  gr.  is  0-921,  and  it  boils  at  12-5°  C.  (55°  F.);  it  is  soluble  in 
10  parts  of  water,  is  but  incompletely  decomposed  by  solution  of  silver 
nitrate  when  the  two  are  heated  together  in  a  sealed  tube,  but  is  quickly 
resolved  into  potassium  chloride  and  ethyl  alcohol  by  a  hot  aqueous  solu- 
tion of  caustic  potash : 

C2H5C1        +        KOH        =        KC1        +        C2H5OH. 

With  alcoholic  potash,  on  the  other  hand,  or  potassium  ethylate,  it  yields 
ethyl-oxide,  or  common  ether: 

C2H5C1     +     C2H5OK     =     KC1     +     (C2H6)20. 
Heated  with  soda-lime,  it  yields  ethene  or  olefiant  gas : 

2C2H5C1     +     ONa2    =    2NaCl    +     OH2    -f     C2H4. 

When  vapor  of  ethyl  chloride  is  mixed  with  chlorine  gas  in  a  vessel  ex- 
posed first  to  diffused  daylight,  and  afterwards  to  direct  sunshine,  hydro- 
chloric acid  is  formed,  and  the  chlorine  displaces  one  atom  of  hydrogen  in 
the  ethyl  chloride,  producing  monochlorinated  ethyl  chloride,  or  dichlor- 
ethane,  C2H4C12,  a  colorless,  oily  liquid,  isomeric  with  ethene  chloride  or 
Dutch  liquid.  By  the  prolonged  action  of  chlorine  in  excess,  the  com- 
pounds C2H?C13,  C2H2C14,  C2HC15,  and  C2C16  are  produced,  the  last  of  which 
is  a  crystalline  body,  identical  with  the  carbon  trichloride  produced  by  the 
action  of  chlorine  on  Dutch  liquid. 

Ethyl  Bromide,  or  Bromethane,  C2H5Br,  also  called  Hydrobromic  ether,  is 
prepared  by  distilling  a  mixture  of  8  parts  bromine,  1  part  phosphorus, 
and  39  parts  alcohol.  It  is  a  very  volatile  liquid,  heavier  than  water,  hav- 
ing a  penetrating  taste,  and  odor,  boiling  at  41°  C.  (106°  F.). 

Ethyl  Iodide,  or  lodethane,  C2HfiI,  also  called  Hydriodic  ether,  may  be  con- 
veniently prepared  with  5  parts  of  phosphorus,  70  parts  of  alcohol  (of  0-84 
sp.  gr.)  and  100  parts  of  iodine.  The  phosphorus  is  introduced  into  a  tu- 
bulated retort,  covered  with  part  of  the  alcohol,  and  heated  to  fusion. 
The  rest  of  the  alcohol  is  poured  upon  the  iodine,  and  the  solution  thus 
obtained  is  allowed  to  flow  gradually  through  a  tap-funnel  into  the  retort. 
The  brown  liquid  is  at  once  decolorized,  and  ethyl  iodide  distils  over,  which 
is  condensed  by  a  good  cooling  apparatus.  The  distillate,  consisting  of  al- 
cohol and  ethyl  iodide,  is  again  poured  on  the  residuary  iodine,  which  is 
thus  rapidly  dissolved,  introduced  into  the  retort,  and  ultimately  entirely 
converted  into  ethyl  iodide.  The  latter  is  washed  with  water  to  remove 
adhering  alcohol,  separated  from  this  water  by  a  tap-funnel,  digested  with 
calcium  chloride,  and  rectified  in  the  water-bath.  Ethyl  iodide  may  also 
be  formed  by  heating  in  a  sealed  glass  vessel  a  mixture  of  hydriodic  acid 
and  olefiant  gas.  Hydriodic  ether  is  a  colorless  liquid,  of  penetrating  ethe- 


ETHYLIC    ETHERS.  523 

real  odor,  having  a  density  of  1-92,  and  boiling  at  72°  C.  (162°  F.).  It  be- 
comes red  by  exposure  to  light,  from  a  commencement  of  decomposition. 
This  substance  has  become  highly  important  as  a  source  of  ethyl,  and  from 
its  remarkable  deportment  with  ammonia,  which  will  be  discussed  in  the 
Section  on  Organic  Bases. 

Ethyl  Oxide,  or  Ethylic  ether,  C4HiqO=C2H6(OC2H6)=(C2H6)20.  This 
compound,  also  called  common  ether,  or  simply  ether,  contains  the  elements 
of  2  molecules  of  alcohol  minus  1  molecule  of  water : 

2C2H60  OH2       =       C4H100; 

and  it  is  in  fact  produced  by  the  action  of  various  dehydrating  agents, 
such  as  zinc  chloride,  phosphoric  oxide,  and  strong  sulphuric  acid,  upon 
alcohol.  The  process  does  not  appear,  however,  to  be  one  of  direct  dehy- 
dration, at  least  in  the  case  of  sulphuric  acid ;  for  when  that  acid  is  heated 
with  alcohol  to  a  certain  temperature,  it  does  not  become  weaker  by  taking 
water  from  the  alcohol,  but  ether  and  water  distil  over  together,  and  the 
sulphuric  acid  remains  in  its  original  state,  ready  to  act  in  the  same  man- 
ner on  a  fresh  portion  of  alcohol.  The  reaction  is  in  fact  one  of  sub- 
stitution, the  ultimate  result  being  the  conversion  of  alcohol,  C2H5(OH), 
into  ether,  C2H5(OC2H6),  by  the  substitution  of  ethyl  for  hydrogen.  The 
manner  in  which  this  takes  place  will  be  better  understood  when  another 
mode  of  the  formation  of  ether  has  been  explained. 

When  a  solution  of  sodium  ethylate,  C2H5ONa,  in  anhydrous  alcohol,  ob- 
tained by  dissolving  sodium  to  saturation  in  that  liquid,  is  mixed  with  ethyl 
iodide,  double  decomposition  takes  place,  resulting  in  the  formation  of  so- 
dium iodide  and  ethyl  oxide : 

C2H5ONa     -f     C2H5I     =     Nal     -f     C2H6(OC2H50). 

The  result  would  be  the  same  if  chloride  or  bromide  of  ethyl  were  substi- 
tuted for  the  iodide :  moreover,  when  methyl  iodide  is  added,  instead 
of  the  ethyl  iodide,  an  oxygen  ether  is  formed  containing  both  ethyl  and 
methyl: 

C2H6ONa      -f       CH3I     =      Nal      +       C2H6QCHS. 
Sodium  ethylate.         Methyl  Methyl-ethyl 

iodide.  ether. 

In  each  case  the  reaction  consists  in  an  interchange  between  the  sodium 
and  the  alcohol-radical. 

Now,  when  alcohol  is  heated  with  strong  sulphuric  acid,  the  first  result 
is  the  formation  of  ethylsulphuric  acid,  S02(OC2H6)OH,  by  substitution  of 
ethyl  for  hydrogen  in  the  acid : 

S02(OH)(OH)    +    C2H5(OH)    =    H(OH)    -f    S02(OC2H6)(OH); 
Sulphuric  Alcohol.  Water.  Ethylsulphuric 

acid.  acid. 

and  when  the  ethylsulphuric  acid  thus  formed  is  brought  in  contact,  at  a 
certain  temperature,  with  a  fresh  portion  of  alcohol,  the  reverse  sub- 
stitution takes  place,  resulting  in  the  formation  of  ethyl  oxide  and  sulphu- 
ric acid: 

SO,(OC2H5)(OH)    +    C2H6(OH)    =    C2H5(OC2H6)    +    S04(OH)2 
Ethylsulphuric  Alcohol.  Ether.  Sulphuric 

acid.  acid. 

The  sulphuric  acid  is  thus  reproduced  in  its  original  state,  and  if  the  sup- 
ply of  alcohol  be  kept  up,  and  the  temperature  maintained  within  certain 
limits,  the  same  series  of  actions  is  continually  repeated,  and  ether  and 
water  distil  over  together. 


524: 


ALCOHOLS   AND   ETHERS. 


The  most  favorable  temperature  for  etherification  is  between  127°  and 
154°  C.  (200°  and  310°  F.);  below  127°  very  little  ether  is  produced,  and 
above  154°  a  different  reaction  takes  place,  resulting  in  the  formation  of 
olefiant  gas.  The  maintenance  of  the  temperature  within  the  ether-pro- 
ducing limits  is  best  effected  by  boiling  the  mixture  of  sulphuric  acid  and 
alcohol  in  a  flask  into  which  a  further  quantity  of  alcohol  is  supplied  in  a 
continuous  and  regulated  stream.  This  is  called  the  continuous  ether  process, 

A  wide-necked  flask  is  fitted  with  a  sound  cork,  perforated  by  three 
apertures,  one  of  which  is  destined  to  receive  a  thermometer  with  the  grad- 
uation on  the  stem;  a  second,  a  vertical  portion  of  a  long,  narrow  tube, 
terminating  in  an  orifice  of  about  J^  Of  an  inch  in  diameter ;  and  the  third, 

fig.  191.* 


a  wide  bent  tube,  connected  with  the  condenser,  to  carry  off  the  volatilized 
products.  A  mixture  is  made  of  8  parts  by  weight  of  concentrated  sul- 
phuric acid,  and  5  parts  of  rectified  spirit  of  wine,  of  about  0-834  sp.  gr. 
This  is  introduced  into  the  flask,  and  heated  by  a  lamp.  The  liquid  soon 
boils,  and  the  thermometer  very  shortly  indicates  a  temperature  of  140° 
C.  (284°  F.).  When  this  happens,  alcohol  of  the  above  density  is  suffered 
slowly  to  enter  by  the  narrow  tube,  which  is  put  into  communication  with 
a  reservoir  of  that  liquid,  consisting  of  a  large  bottle  perforated  by  a  hole 

*  Fig.  191.  Apparatus  for  the  preparation  of  ether,  a.  Flask  for  containing  the  mixture 
of  oil  of  vitriol  and  alcohol,  b.  Reservoir  with  stopcock,  for  supplying  a  constant  stream  of 
alcohol,  c.  Wide  bent  tube  connected  with  the  condenser  for  conveying  away  tho  vapors,  d. 
The  thermometer  for  regulating  the  temperature  of  the  boiling  liquid. 


ETHYLIC    ETHERS.  525 

near  the  bottom,  and  furnished  with  a  small  brass  stopcock  fitted  by  a 
cork.  The  stopcock  is  secured  to  the  end  of  the  long  tube  by  a  caoutchouc 
connector.  As  the  tube  passes  nearly  to  the  bottom  of  the  flask,  the  al- 
cohol gets  thoroughly  mixed  with  the  acid  liquid,  the  hydrostatic  pressure 
of  the  fluid  column  being  sufficient  to  insure  the  regulai-ity  of  the  flow ;  the 
quantity  is  easily  adjusted  by  the  aid  of  the  stopcock.  For  condensation 
a  Liebig's  condenser  may  be  used,  supplied  with  ice-water.  The  arrange- 
ment is  shown  in  figure  191. 

The  intensity  of  the  heat,  atid  the  supply  of  alcohol,  must  be  so  adjusted 
that  the  thermometer  may  remain  at  140°  C.  (284°  F.),  or  as  near  that  tem- 
perature as  possible,  while  the  contents  of  the  flasMkre  maintained  in  a  state 
of  rapid  and  violent  ebullition  —  a  point  of  essential  importance.  Ether  and 
water  distil  over  together,  and  collect  in  the  receiver,  forming  two  distinct 
strata :  the  mixture  slowly  blackens,  from  some  slight  secondary  action  of 
the  acid  upon  the  spirit,  or  upon  the  impurities  in  the  latter,  but  retains, 
after  many  hours'  ebullition,  its  etherifying  powers  unimpaired.  The  acid, 
however,  slowly  volatilizes,  partly  in  the  state  of  oil  of  wine,  and  the  quantity 
of  liquid  in  the  flask  is  found,  after  the  lapse  of  a  considerable  interval, 
sensibly  diminished.  The  loss  of  acid  constitutes  the  only  limit  to  the 
duration  of  the  process,  which  might  otherwise  be  continued  indefinitely. 

On  the  large  scale,  the  flask  may  be  replaced  by  a  vessel  of  lead,  the 
tubes  being  also  of  the  same  metal:  the  stem  of  the  thermometer  may  be 
made  to  pass  air-tight  through  the  cover,  and  heat  may  perhaps  be  advan- 
tageously applied  by  high-pressure  steam,  or  hot  oil,  circulating  in  a  spiral 
tube  of  metal  immersed  in  the  mixture  of  acid  and  spirit. 

The  crude  ether  is  to  be  separated  from  the  water  on  which  it  floats, 
agitated  with  a  little  solution  of  caustic  potash,  and  re-distilled  by  the  heat 
of  warm  water.  The  aqueous  portion,  treated  with  an  alkaline  solution, 
and  distilled,  yields  alcohol  containing  a  little  ether.  Sometimes  the  spon- 
taneous separation  before  mentioned  does  not  occur,  from  the  accidental 
presence  of  a  larger  quantity  than  usual  of  undecomposed  alcohol;  the 
addition  of  a  little  water,  however,  always  suffices  to  determine  it. 

Pure  ethylic  ether  is  a  colorless,  transparent,  fragrant  liquid,  very  thin 
and  mobile.  Its  sp.  gr.  at  15-5°  is  about  0-720 ;  it  boils  at  35-6°  C.  (96°  F.) 
under  the  pressure  of  the  atmosphere,  and  bears  without  freezing  the 
severest  cold.  When  dropped  on  the  hand  it  occasions  a  sharp  sensation 
of  cold,  from  its  rapid  volatilization.  Ether  is  very  combustible,  and  burns 
with  a  white  flame,  generating  water  and  carbon  dioxide.  Although  the 
substance  itself  is  one  of  the  lightest  of  liquids,  its  vapor  is  very  heavy, 
having  a  density  of  2-586  (referred  to  air).  Mixed  with  oxygen  gas,  and 
fired  by  the  electric  spark,  or  otherwise,  it  explodes  with  the  utmost  vio- 
lence. Preserved  in  an  imperfectly  stopped  vessel,  ether  absorbs  oxygen, 
and  becomes  acid  from  the  production  of  acetic  acid:  this  attraction  for 
oxygen  is  increased  by  elevation  of  temperature.  It  is  decomposed  by 
transmission  through  a  red-hot  tube  into  ethene,  methane,  aldehyde,  and 
ethine,  and  two  substances  yet  to  be  described. 

Ether  is  miscible  with  alcohol  in  all  proportions,  but  not  with  water;  it 
dissolves  to  a  small  extent  in  that  liquid,  10  parts  of  water  taking  up  about 
1  part  of  ether.  It  may  be  separated  from  alcohol,  provided  the  quantity 
of  the  latter  is  not  excessive,  by  addition  of  water,  and  in  this  manner 
samples  of  commercial  ether  may  be  conveniently  examined.  Ether  dis- 
solves oily  and  fatty  substances  generally,  and  phosphorus  to  a  small  extent, 
also  a  few  saline  compounds  and  some  organic  principles;  but  its  powers 
in  this  respect  are  much  more  limited  than  those  of  alcohol  or  water. 

Anhydrous  ether,  subjected  to  the  action  of  chlorine,  yields  the  three  sub- 
stitution-products C4H80120,  C4H6C140,  and  C4C1100,  the  first  two  of  which 
are  liquids,  while  the  third,  produced  by  the  prolonged  action  of  chlorine 
on  ether  in  sunshine,  is  a  crystalline  solid.  The  second  chlorine  compound 


526  ALCOHOLS   AND   ETHERS. 

is  converted  by  hydrogen  sulphide  into  the  two  crystalline  compounds 
C4H6C12SO  and  C4H6S20. 

Ethyl-methyl  oxide,  Ethyl-methyl  ether,  Ethyl  melhylate,  or  Methyl  ethylate, 
C3H80  =  C2H5OCH3,  is  produced,  as  already  mentioned,  by  the  action  of 
methyl  iodide  on  potassium  ethylate,  or  of  ethyl  iodide  on  potassium  me- 
thylate.  It  is  a  very  inflammable  liquid,  boiling  at  11°  C.  (52°  F.). 

Ethyl  Nitrate,  C2H6N03,  or  C2H5ON02.—  Nitric  ether.—  When  nitric  acid  is 
heated  with  alcohol  alone,  part  of  the  alcohol  is  oxidized,  and  the  nitric 
acid  is  reduced  to  nitrous  acid,  which,  with  the  remainder  of  the  alcohol, 
forms  ethyl  nitrite,  C2H-N02,  together  with  other  products;  but  by  adding 
urea  to  the  liquid,  whicMfrdecomposes  the  nitrous  acid  as  fast  as  it  is  formed, 
this  action  may  be  prevented,  and  the  alcohol  and  nitric  acid  then  form 
ethyl  nitrate.  The  experiment  is  most  safely  conducted  on  a  small  scale, 
and  the  distillation  must  be  stopped  when  seven-eighths  of  the  whole  have 
passed  over;  a  little  water  added  to  the  distilled  product  separates  the 
nitric  ether.  Nitric  ether  has  a  density  of  1-112;  it  is  insoluble  in  water, 
has  an  agreeable  sweet  taste  and  odor,  and  is  not  decomposed  by  an  aqueous 
solution  of  caustic  potash,  although  that  substance  dissolved  in  alcohol 
attacks  it  even  in  the  cold,  with  production  of  potassium  nitrate.  Its 
vapor  is  apt  to  explode  when  strongly  heated. 

ETHYL  NITRITE,  C2H5ONO. — Nitrous  ether. — Pure  nitrous  ether  can  only 
be  obtained  by  the  direct  action  of  the  acid  itself  upon  alcohol.  1  part  of 
starch  and  10  parts  of  nitric  acid  are  gently  heated  in  a  capacious  retort 
or  flask,  and  the  vapor  of  nitric  acid  thereby  evolved  is  conducted  into 
alcohol  mixed  with  half  its  weight  of  water,  contained  in  a  two-necked 
bottle,  which  is  to  be  plunged  into  cold  water  and  connected  with  a  good 
condensing  arrangement.  All  elevation  of  temperature  must  be  carefully 
avoided.  The  product  of  this  operation  is  a  pale-yellow  volatile  liquid, 
having  an  exceedingly  agreeable  odor  of  apples:  it  boils  at  16-4°  C.  (61°  F.), 
and  has  a  density  of  0-947.  It  is  decomposed  by  potash,  without  darkening, 
into  potassium  nitrite  and  alcohol. 

Nitrous  ether,  but  contaminated  with  aldehyde,  may  be  prepared  by  the 
following  simple  method.  Into  a  tall  cylindrical  bottle  or  jar  are  to  be  in- 
troduced successively  9  parts  of  alcohol  of  sp.  gr.  0-830,  4  parts  of  water, 
and  8  parts  of  strong  fuming  nitric  acid;  the  two  latter  are  added  by 
means  of  a  long  funnel  with  a  very  narrow  orifice,  reaching  to  the  bottom 
of  the  bottle,  so  that  the  contents  may  form  three  distinct  strata,  which 
slowly  mix  from  the  solution  of  the  liquids  in  each  other.  The  bottle  is 
then  loosely  stopped,  and  left  two  or  three  days  in  a  cool  place,  after  which 
it  is  found  to  contain  two  layers  of  liquid,  of  which  the  uppermost  is  nitrous 
ether.  It  is  purified  by  rectification.  A  somewhat  similar  product  may  be 
obtained  by  carefully  distilling  a  mixture  of  3  parts  rectified  spirit  and  2 
of  nitric  acid  of  1-28  sp.  gr. :  the  fire  must  be  withdrawn  as  soon  as  the 
liquid  boils. 

The  sweet  spirits  of  nitre  of  pharmacy,  prepared  by  distilling  three  pounds 
of  alcohol  with  four  ounces  of  nitric  acid,  is  a  solution  of  nitrous  ether, 
aldehyde,  and  perhaps  other  substances,  in  spirits  of  wine. 

Ethyl  Sulphates. — There  are  two  of  these  ethers,  corresponding  to  the 
methyl  sulphates. 

Acid  Ethyl  sulphate,  Ethylsulphuric  acid  or  Sulphovinic  acid,  C2H6S04=: 
C2H5OS03H=S02(OC2H5)(OH)=S04(C2H6)H,  which  has  the  composition  of 
sulphuric  acid,  S04H2,  with  half  the  hydrogen  replaced  by  ethyl,  is 
formed  by  the  action  of  sulphuric  acid  upon  alcohol.  To  prepare  it,  strong 
rectified  spirit  of  wine  is  mixed  with  twice  its  weight  of  concentrated  sul- 
phuric acid ;  the  mixture  is  heated  to  its  boiling  point,  and  then  left  to  cool. 
When  cold,  it  is  diluted  with  a  large  quantity  of  water,  and  neutralized 


ETHYLIC   ETHERS.  527 

with  chalk,  whereby  much  calcium  sulphate  is  produced.  The  mass  is 
placed  upon  a  cloth  filter,  drained,  and  pressed;  and  the  clear  solution  is 
evaporated  to  a  small  bulk  by  the  heat  of  a  water-bath,  filtered  from  a 
little  sulphate,  and  left  to  crystallize:  the  product  is  calcium  ethylsulphate, 
in  beautiful,  colorless,  transparent  crystals,  containing  (S04)2(C2H5)2Ca//. 
20H2.  They  dissolve  in  an  equal  weight  of  cold  water,  and  effloresce  in  a 
dry  atmosphere. 

Barium  ethylsulphate,  (S04)2(C2H5)Ba// .  20H2,  equally  soluble,  and  still 
more  beautiful,  may  be  produced  by  substituting,  in  the  above  process, 
barium  carbonate  for  chalk :  from  this  substance  the  acid  may  be  procured 
by  exactly  precipitating  the  base  with  dilute  sulphuric  acid,  and  evaporat- 
ing the  filtered  solution  in  a  vacuum  at  the  temperature  of  the  air.  It 
forms  a  sour,  syrupy  liquid,  in  which  sulphuric  acid  cannot  be  recognized 
by  the  ordinary  reagents,  and  is  very  easily  decomposed  by  heat,  and  even 
by  long  exposure  in  the  vacuum  of  the  air-pump.  All  the  ethylsulphates 
are  soluble ;  the  solutions  are  decomposed  by  ebullition.  The  lead-salt  re- 
sembles the  barium-compound.  The  potassium  salt,  S04(C2H6)K — easily 
made  by  decomposing  calcium  ethylsulphate  with  potassium  carbonate — is 
anhydrous,  permanent  in  the  air,  very  soluble,  and  crystallizes  well. 

Potassium  ethylsulphate  distilled  with  concentrated  sulphuric  acid,  gives 
ether;  with  dilute  sulphuric  acid,  alcohol;  and  with  strong  acetic  acid, 
acetic  ether.  The  ethylsulphates  heated  with  calcium  or  barium  hydrate, 
yield  a  sulphate  of  the  base  and  alcohol. 

Isethionic  acid,  C2H6S04,  an  acid  isomeric  with  ethylsulphuric  acid,  is  ob- 
tained, as  already  observed,  by  boiling  ethionic  acid  (p.  518)  with  water; 
also  by  the  prolonged  action  of  strong  sulphuric  acid  or  sulphuric  oxide  on 
alcohol  or  ether,  and  is  found  among  the  residues  of  the  preparation  of 
ether.  It  is  a  viscid,  strongly  acid  liquid,  which  decomposes  acetates  and 
common  salt,  bears  without  decomposition  a  heat  of  150°  C.  (302°  F.),  but 
blackens  at  a  higher  temperature. 

The  metallic  isethionates  are  soluble  and  crystallizable,  and  are  distin- 
guished from  the  ethylsulphates,  with  which  they  are  isomeric,  by  their 
much  greater  stability,  most  of  them  sustaining,  without  alteration,  a  tem- 
perature of  200°  C.  (392°  F.I. 

Potassium  isethionate,  C2H5KS04,  distilled  with  phosphorus  pentachlo- 
ride,  yields  isethionic  chloride,  C2H4S02C12;  and  this  compound,  heated  in 
sealed  tubes  with  ammonia,  is  converted  into  taurin,  a  neutral  crystallizable 
Bubstance  likewise  obtained  from  bile: 

C2H4S02C!2    -f     NH3    +     OH2    =    2HC1     -f     C2H7NS03. 
Isethionic  Taurin. 

chloride. 

Taurin,  treated  with  nitrous  acid,  is  reconverted  into  isethionic  acid. 

Neutral  Ethyl  sulphate,  S04(C2H5)2,  or  S02(OC2H5)2,  is  formed  by  passing 
the  vapor  of  sulphuric  oxide  into  perfectly  anhydrous  ether.  A  syrupy 
liquid  is  produced,  which,  when  shaken  with  4  vols.  of  water  and  1  vol.  of 
ether,  separates  into  two  layers,  the  lower  containing  ethylsulphuric  acid 
and  various  other  compounds,  while  the  upper  layer  consists  of  an  ethereal 
solution  of  neutral  ethyl  sulphate.  At  a  gentle  heat  the  ether  is  volatilized, 
and  the  ethyl  sulphate  remains  as  a  colorless  liquid.  It  cannot  be  distilled 
without  decomposition. 

Ethyl  Sulphites. — The  acid  sulphite,  or  Ethylsulphurous  acid,  S03(C2H5)H, 
is  produced  by  the  action  of  nitric  acid  on  ethyl  sulphhydrate  or  sulpho- 
cyanate.  When  concentrated  by  evaporation  it  is  a  heavy  oil  of  specific 
gravity  1-30.  It  is  a  monobasic  acid,  forming  crystallizable  salts,  which 
decompose  when  heated,  giving  off  sulphurous  oxide. — Neutral  Ethyl  sul- 
phite, S03(C2H6)2,  is  obtained  by  adding  absolute  alcohol  in  excess  to  chlorine. 


528  ALCOHOLS   AND   ETHERS. 

bisulphide  (p.  203).  Hydrochloric  acid  is  evolved,  and  sulphur  deposited, 
while  the  ethyl  sulphite  distils  as  a  limpid  strongly-smelling  liquid,  of  sp. 
gr.  1-085,  boiling  at  170°;  it  is  slowly  decomposed  by  water. 

Ethyl  Phosphates. — Three  ethyl  orthophosphates  have  been  obtained, 
two  acid  and  one  neutral,  analogous  in  composition  to  the  sodium  phos- 
phates ;  also  a  neutral  pyrophosphate. 

Monethylic  phosphate,  or  Ethylphosphoric  acid,  P04(C2H5)H2,  or  (P0)/r/ 
(OC2H6)(OH)2,  also  called  Phosphovinic  acid.  This  acid  is  bibasic.  Its  barium 
salt  is  prepared  by  heating  to  82°  C.  (180°  F.)  a  mixture  of  equal  weights  of 
strong  alcohol  and  syrupy  phosphoric  acid,  diluting  this  mixture,  after  the 
lapse  of  24  hours,  with  water,  and  neutralizing  with  barium  carbonate. 
The  solution  of  ethylphosphate,  separated  by  filtration  from  the  insoluble 
phosphate,  is  evaporated  at  a  moderate  temperature.  The  salt  crystallizes 
in  brilliant  hexagonal  plates,  which  have  a  pearly  lustre,  and  are  more 
soluble  in  cold  than  in  hot  water;  it  dissolves  in  15  parts  of  water  at  20° 
C.  (68°  F.).  The  crystals  contain  P()4(C2H6)Ba" .  60H2.  From  this  salt 
the  acid  may  be  obtained  by  precipitating  the  barium  with  dilute  sulphuric 
acid,  and  evaporating  the  filtered  liquid  in  the  vacuum  of  the  air-pump :  it 
forms  a  colorless,  syrupy  liquid,  of  intensely  sour  taste,  sometimes  exhibit- 
ing appearances  of  crystallization.  It  is  very  soluble  in  water,  alcohol, 
and  ether,  and  easily  decomposed  by  heat  when  in  a  concentrated  state. 
The  ethylphosphates  of  calcium,  silver,  and  lead  possess  but  little  solubil- 
ity; those  of  the  alkali-metals,  magnesium,  and  strontium,  arc  freely 
soluble. 

JJiethylie  phosphate,  or  Diethylphosphoric  acid,  P04(C2H5)2H,  or  (P0)//x 
(02C2H5)2(OH),  is  a  monobasic  acid,  obtained,  together  with  the  preceding, 
by  the  action  of  syrupy  phosphoric  acid  upon  alcohol.  Its  barium,  silver, 
and  lead-salts  are  more  soluble  than  the  methylphosphates.  The  calcium 
salt,  (P04)2(C2H5)4Ca//,  and  the  lead-salt,  (P04)2(C2H6)2Pb",  are  anhydrous. 

Triethylic  phosphate,  P04(C2H5)3,  or  (PO)"'(OC2H6)8,  is  obtained  in  small 
quantity  by  heating  the  lead-salt  of  diethylphosphoric  acid  to  100°,  more 
easily  by  the  action  of  ethyl-iodide  on  triargentic  phosphate,  or  of  phos- 
phorus oxychloride  on  sodium  ethylate: 

3C2H5ONa     -f     (PO)"'C1S    =     3NaCl    +     (PO)'"(OC2H6)8. 
It.  is  a  limpid  liquid  of  sp.  gr.  1-072  at  12°  C.  (54°  F.),  boiling  at  215°  C. 
(129°  F.),  soluble  in  alcohol  and  ether,  and  also  'in  water,  by  which  how. 
ever  it  is  slowly  decomposed. 

Tetrethylic  Pyrophosphate,  P2^7(C2H5)4,  produced  by  the  action  of  ethyl 
iodide  on  argentic  pyrophosphate,  is  a  viscid  liquid  of  sp.  gr.  1-172  at  17° 
C.  (63°  F.),  decomposed  by  potash,  with  formation  of  potassium  diethyl- 
phosphate. 

Ethyl  Berates.  —  Three  of  these  ethers  are  known,  viz. : 
Triethylic  borate          .         (C2H5)3B03, 
Monethylic  borate         .          C2H5B02, 
Ethylic  anhydroborate,    \on  H  BO     BO 
orbiborate        .         .     /  ^VV^ .  J52U3. 

Triethylic  borate  is  formed  by  the  action  of  boron  trichloride  on  alcohol : 
3C2H6(OH)     -j-     BC13    =     3HC1     +     (C2H6)3B03. 

It  is  a  thin  limpid  liquid,  of  agreeable  odor,  sp.  gr.  0-885,  boiling  at 
119°  C.  (246°  F,),  decomposed  by  water.  Its  alcoholic  solution  burns  with 
a  fine  green  flame,  throwing  off  a  thick  smoke  of  boric  acid. 

Monethylic  borate,  C2H5B02,  is  formed,  with  separation  of  boric  acid,  by 
the  action  of  alcohol  on  the  anhydroborate : 

2C2HB02.B203    +     C2H5(OH)     =    HB02    +     3C2H6B02. 


ETHYLIC    ETHERS.  529 

It  is  a  colorless,  mobile  liquid,  resembling  triethylic  borate.  The  anhy- 
droborate,  2C2H6B02 .  B203,  is  formed  by  the  action  of  boric  oxide  on  an 
equal  weight  of  anhydrous  alcohol,  and  may  be  obtained  by  concentration, 
in  the  form  of  a  viscid  liquid,  which  solidifies  at  300°  C.  (572°  F.),  giving 
off  alcohol  vapor  and  etheue  gas,  and  leaving  boric  oxide. 

Ethyl  Silicates.  —  Tetrethylic  silicate,  (C2H5)4Si04,  or  SiiT(OC2H6)4,  is  pro- 
duced by  treating  silicic  chloride  with  a  small  quantity  of  anhydrous  al- 
cohol: 

4C2H5OH     +     SiCl4    =    4HC1    +     Si(OC2H5)4. 

It  is  a  colorless  liquid,  having  a  rather  pleasant  ethereal  odor,  and  strong 
peppery  taste ;  sp.  gr.  0-993  at  20°.  It  boils  without  decomposition  be- 
tween 166°  and  160°  C.  (329°-330°  F.),  and  when  set  on  fire  burns  with  a 
dazzling  flame,  diffusing  a  white  smoke  of  finely  divided  silica.  It  is  de- 
composed slowly  by  water,  quickly  by  ammonia  and  the  fixed  alkalies. 

Diethylic  silicate,  (C2H5)2Si03,  or  (SiO)//(OC2H6)2,  is  produced,  according 
to  Ebelmen,*  by  the  action  of  silicic  chloride  on  aqueous  alcohol: 

2C2H5OH    -f    OH2    -f    SiCl4    =    4HC1    -f    (SiO)(OC2H6)2. 

It  is  a  colorless  liquid,  of  sp.  gr.  1  -079,  boiling  at  350°  C.  (662°  F. ),  decomposed 
by  water,  with  separation  of  silica.  On  distilling  it  with  a  small  quantity  of 
aqueous  alcohol,  a  liquid  remains  in  the  retort  consisting  of  diethylic  di- 
silicate,  (C2H5)2Si.,05,  or  (C2H5)2Si03  .  Si02. 

Hezethylic  disilicate,  (C2H5)gSi207,  or  6(C2H6)4Si04 .  2Si02.— Friedel  and 
Crafts*  were  not  able  to  obtain  the  two  ethylic  silicates  last  mentioned; 
but  having  prepared  a  considerable  quantity  of  tetrethylic  silicate  with  al- 
cohol that  was  not  quite  anhydrous,  they  found  that  the  greater  part  of  the 
product  distilled  over  toward  240°,  and  that  it  was  not  possible,  by  distil- 
lation under  the  ordinary  atmospheric  pressure,  to  obtain  a  product  of 
definite  boiling  point.  By  distillation  in  a  vacuum,  however  (under  a  pres- 
sure of  3  to  5  millimetres),  they  obtained,  after  eight  fractionations,  a  pro- 
duct boiling  between  125°  and  130°  C.  (257°-266°  F.),  and  having  the  com- 
position of  hezethylic  disilicate.  This  ether  is  a  slightly  oily  liquid,  having 
a  rather  fragrant  odor,  like  that  of  tetrethylic  silicate,  and  a  specific  grav- 
ity of  1-0 196  at  0°. 

Silicic  ethers  containing  ethyl  and  methyl,  and  ethyl  and  amyl,  have 
likewise  been  obtained. 

The  ethylic  ethers  of  organic  acids  (carbon  acids)  will  be  described  in 
connection  with  those  acids. 

Ethyl  Sulph-hydrate,  or  Mercaptan,  C2H5SH. — This  compound,  the  sul- 
phur analogue  of  ethyl  alcohol,  is  produced  analogously  to  methyl 
sulph-hydrate  (p.  515),  by  the  action  of  potassium  sulph-hydrate  on  cal- 
cium ethylsulphate.  A  solution  of  caustic  potash  of  sp.  gr.  1-28  or  1-3,  is 
saturated  with  sulphuretted  hydrogen,  and  mixed  in  a  retort  with  an  equal 
volume  of  solution  of  calcium  ethylsulphate  of  the  same  density.  The  re- 
tort is  connected  with  a  good  condenser,  and  heat  is  applied  by  means  of  a 
bath  of  salt  and  water.  Mercaptan  and  water  distil  over  together,  and 
are  easily  separated  by  a  tap-funnel.  The  product  thus  obtained  is  a 
colorless,  limpid  liquid,  of  sp.  gr.  0-842,  but  slightly  soluble  in  water,  easily 
miscible,  on  the  contrary,  with  alcohol.  It  boils  at  36°  C.  (96°  F.).  The 
vapor  of  mercaptan  has  a  most  intolerable  odor  of  onions,  which  adheres 
to  the  clothes  and  person  with  great  obstinacy:  it  is  very  inflammable,  and 
burns  with  a  blue  flame. 

When  mercaptan  is  brought  into  contact  with  mercuric  oxide,  even  in 


*  Ann.  Chim.  Phys.  [3]  xvi.  144.  f  Ann.  Chim.  Phys.  [4]  ix.  5. 

45 


530  ALCOHOLS    AND   ETHERS. 

the  cold,  violent  reaction  ensues,  water  is  formed,  and  a  white  substance  is 
produced,  soluble  in  alcohol,  and  separating  from  that  liquid  in  distinct 
crystals  which  contain  (C2H5)2S2Hg//.  This  compound  is  decomposed  by 
sulphuretted  hydrogen,  mercuric  sulphide  being  thrown  down,  and  mer- 
captan  reproduced.  By  adding  solutions  of  lead,  copper,  silver,  and  gold 
to  an  alcoholic  solution  of  mercaptan,  corresponding  compounds  containing 
those  metals  are  formed.  Caustic  potash  produces  no  eifect  upon  mercap- 
tan, but  potassium  displaces  hydrogen,  and  gives  rise  to  a  crystallizable 
compound,  C2H5SK,  soluble  in  water.  Sodium  acts  in  a  similar  manner. 

Ethyl  Sulphides. — Three  of  these  compounds  have  been  obtained,  analo- 
gous in  composition  to  the  methyl  sulphides,  and  produced  by  similar  re- 
actions. The  monosulphide,  (C2H5)S,  or  C2H5SC2H5,  is  a  colorless  oily  liquid, 
having  a  very  pungent  alliaceous  odor,  a  specific  gravity  of  0-825  at  20°  C. 
(68°  F.),  and  boiling  at  72°  C.  (162°  P.).  It  is  very  inflammable,  and  burns 
with  a  blue  flame.  When  poured  into  chlorine  gas,  it  takes  fire  ;  but  when 
dry  chlorine  is  passed  into  a  flask  containing  it,  not  at  first  into  the  liquid, 
the  vessel  being  kept  cool  and  in  the  shade,  substitution-products  are 
formed  and  hydrochloric  acid  is  copiously  evolved.  The  product  consists 
chiefly  of  dichlorethylic  sulphide,  (C2H4C1)2S.  If  the  action  takes  place  in 
diifused  daylight,  and  without  external  cooling,  the  compounds  (C2H2C13)2S 
and  (C2HC14)2S  are  obtained,  which  may  be  separated  by  fractional  distil- 
lation, the  first  boiling  between  189°  and  192°  C.  (372°-378°F.),  the  second 
between  217°  and  222°  C.  (423-432°  F.).  The  action  of  chlorine  on  ethyl 
sulphide  in  sunshine  yields  a  more  highly  chlorinated  compound,  probably 
(C2C16)2S. 

Ethyl  bisulphide,  (C2H5)2S2,  obtained  by  distilling  potassium  bisulphide 
with  potassium  ethylsulphate  or  with  ethyl  oxalate,  is  a  colorless  oily  liquid, 
very  inflammable,  boiling  at  151°  C.  (302°  F.).  The  trisulphide,  (C2H5)2S3, 
is  a  heavy  oily  liquid,  obtained  by  acting  in  like  manner  on  potassium 
pentasulphide. 

Triethylsulphurous  Compounds.*  —  When  ethyl  monosulphide  and  ethyl 
iodide  are  heated  together,  they  unite  and  form  sulphurous  iodotriethide, 
(C2H5)2S  .  C2H5I,  or  Siv(C2H6)3I,  which  crystallizes  in  needles.  The  same 
compound  is  formed  by  the  action  of  ethyl  iodide  on  ethyl  sulph-hydrate : 

2C2H5I        +        C2H5SH        =        HI        +        S(C2H6)3I, 
or  of  hydrogen  iodide  on  ethyl  monosulphide  : 

HI        +        2(C2H5)2S        =        C2H5SH        +        S(C2H5)3I. 
Sulphurous  iodotriethide  is  insoluble  in  ether,  slightly  soluble  in  alcohol,  and 
crystallizes  from  the  solution  in  white  deliquescent  needles  belonging  to  the 
monoclinic  system.     It  unites  with  metallic  chlorides. 

Ethyl  chloride  and  ethyl  bromide  unite  in  like  manner,  but  less  readily, 
with  ethyl  sulphide,  forming  the  compounds  S(C2H5)3C1  and  S(C2H5)3Br, 
both  of  which  crystallize  in  needles. 

By  treating  the  iodine  compound  with  recently-precipitated  silver  oxide, 
a  strongly  alkaline  solution  is  obtained,  which  dries  up  over  oil  of  vitriol 
to  a  crystalline  deliquescent  mass,  consisting  of  sulphurous  triethyl-hydroxy- 
late,  (C2H5)3S(OH).  The  solution  of  this  substance  dissolves  the  skin  like 
caustic  potash,  and  forms  similar  precipitates  with  various  metallic  salts. 
It  neutralizes  acids,  forming  definite  crystallizable  salts,  e.g.,  the  nitrate, 
(C2H5)3SON02,  the  acetate  (C2H6)8S(OC2H,0),  &c. 

The  formulae  of  these  compounds  show  that  sulphur  is  at  least  quadri- 
valent (p.  237). 

*  A.  vnn  OeffeJc,  Chem.  Soc.  Journal,  xvii.  108.  Cahours,  Ann.  Ch.  Pharm.  cxxxv.  352; 
cxxxvi.  151.  ftehn,  Aim.  Cl*.  Pharm.  Suppl.  iv.  83. 


PROPYL   ALCOHOL.  531 


PROPYL  ALCOHOLS  AND  ETHERS. 

It  has  already  been  observed  that  the  three-carbon  alcohol,  C3H80,  is 
susceptible  of  two  isomeric  modifications,  namely : 


CH3 

(CH2CH3          7 
Normal  Propyl  alcohol       C  -j  H2  or     CH2  thus 

CH2( 


2 
(OH 

OH 


H3C  CH3 

Isopropyl  alcohol  C 1  ^"8        or  \/ 

HCOH 


{I 


each  of  which  may  give  rise  to  a  corresponding  set  of  ethers  and  other 
derivatives.  The  normal  propyl  compounds,  however,  are  but  little  known, 
none  of  them  having  yet  been  prepared  synthetically,  except  propylamine 
and  propyl  cyanide,  to  be  afterwards  considered.  Chancel,  in  1853,  by 
subjecting  the  fusel-oil  of  marc  brandy,  prepared  in  the  south  of  France, 
to  fractional  distillation,  obtained  a  number  of  alcohols,  among  which  was 
one  to  which  he  assigned  the  composition  C3II80;  this  has  usually  been 
regarded  as  normal  propyl  alcohol,  but  it  was  not  obtained  pure,  and  is 
altogether  very  little  known. 

Isopropyl  Alcohol,  CII(CH3)2OH. — This  alcohol  is  prepared:  1.  From 
acetone,  (CO)//(CH3)2,  by  direct  addition  of  hydrogen,  evolved  by  the 
action  of  water  on  sodium  amalgam: 

H3C  CH3  H3C  CH, 

V          +      H2      =          v 

CO  HCOH 

Acetone.  Isopropyl 

alcohol. 

This  mode  of  synthesis  affords  direct  proof  of  the  constitution  of  iso- 
'propylic  alcohol,  the  addition  of  the  two  hydrogen-atoms  being  tantamount 
to  the  replacement  of  the  bivalent  radical  oxygen  by  the  two  monad  radi- 
cals, hydrogen  and  hydroxyl. 

2.  Isopropyl  iodide  is  prepared  by  the  action  of  iodine  and  phosphorus 
on  glycerin ;  this  iodide  is  easily  converted  into  the  oxalate  or  acetate  by 
treatment  with  silver  oxalate  or  acetate ;  and  from  either  of  these  ethers 
the  alcohol  may  be  obtained  by  distillation  with  potash  or  soda. 

Isopropyl  alcohol  is  a  colorless,  not  very  mobile  liquid,  having  a  peculiar 
odor,  a  specific  gravity  of  0  791  at  15°  C.  (60°  F.),  boiling  at  83°  to  84°  C. 
(181°-183°F.),  under  a  barometric  pressure  of  739  millimetres,  not  freezing 
at  20°.  It  does  not  act  on  polarized  light.  It  is  very  difficult  to  dry,  as  it 
mixes  with  water  in  all  proportions,  and  forms  with  it  three  definite  and 
very  stable  hydrates,  viz.,  3C3H80.20H2,  boiling  at  78°-80°  C.  (172°-176° 
F.);  2C,H8O.OII2,  boiling  at  80°;  and  3C3H80 .  OH2,  boiling  at  81°.  The 
second  of  these  hydrates  exhibits  a  very  close  resemblance  to  ethyl  alcohol, 
and  has  the  same  percentage  composition,  boils  at  nearly  the  same  tem- 
perature, and  likewise  yields  acetic  acid  by  oxidation  (see  p.  532) ;  more- 
over it  retains  its  water  of  hydration  so  obstinately,  that  it  does  not  even 
change  the  white  color  of  anhydrous  cupric  sulphate  to  blue.  The  readiest 
mode  of  distinguishing  between  this  hydrate  and  ethyl  alcohol  is  to  submit 


532  ALCOHOLS   AND   ETHERS. 

them  to  the  action  of  iodine  and  phosphorus,  whereby  the  former  is  con- 
verted into  isopropyl  iodide,  the  latter  into  ethyl  iodide. 

The  characteristic  property  of  isopropyl  alcohol  is  that  it  yields  acetone 
by  oxidation  with  dilute  chromic  acid,  this  transformation  being  the  reverse 
of  that  by  which  it  is  produced : 

H3C  CH,  H3C  CH3 

V          +          °        =  V  +     OH2 

HCOH  CO 

On  pushing  the  oxidation  further,  the  acetone  breaks  up  into  acetic  acid, 
carbon  dioxide  and  water : 

CO(CH3)2     -f     04     =     CO(CH3)OH     -f     C02     -f     OH2 
Acetone.  Acetic  acid. 

The  evolution  of  carbon  dioxide  in  this  reaction  affords  a  further  distinc- 
tion between  hydrated  isopropyl  alcohol  and  ethyl  alcohol. 

The  formation  of  a  ketone  by  oxidation  is  the  essential  characteristic  of 
a  secondary  alcohol,  and  is  an  immediate  consequence  of  its  structure. 
The  primary  alcohols,  Cn  H2n+2O,  are  directly  converted  by  oxidation  into 
aldehydes,  Cn  H^O,  and  acids,  CnH2a02,  not  into  ketones;  thus: 

CH3  CH3 

I    '         +  0          =          OH2          +          |    * 
CH2OH  H— C=0 

Ethyl  alcohol.  Aldehyde. 

C2H40  +  0  =  C2H402 

Aldehyde.  Acetic  acid. 

Isopropyl  alcohol,  heated  with  acetic  acid,  or  with  potassium  acetate  and 
sulphuric  acid,  is  converted  into  isopropyl  acetate,  CH(CH3)2OC2H30. 

ISOPROPYL  IODIDE,  CH(CH3)2I,  is  most  conveniently  prepared  by  the  ac- 
tion of  hydriodic  acid,  concentrated  and  in  larger  excess,  on  glycerin 
(propenyl  alcohol)  C3Hg03: 

C3H803    +     5HI    =    C3H7I     -f     30H2    -f-    2I2. 

The  iodine,  as  fast  as  it  is  set  free  by  the  reaction,  may  be  reconverted 
into  hydriodic  acid  by  means  of  phosphorus,  and  will  then  be  ready  to 
act  upon  another  portion  of  glycerin.  It  may  also  be  produced  by  the  ac- 
tion of  hydriodic  acid  on  isopropyl  alcohol,  allyl  iodide,  C3H5I,  propene,  or 
propene  alcohol. 

Isopropyl  iodide  is  an  oil  boiling  at  89°-90°  C.  (192°-194°  F.),  and  having 
a  specific  gravity  of  1-70.  With  sodium  in  presence  of  ether  it  yields  pro- 
pene, propane,  and  di-isopropyl,  C6H14.  Bromine  expels  the  iodine  and 
forms  isopropyl  bromide. 


QUARTYL  OR  BUTYL  ALCOHOLS  AND  ETHERS. 

Theory  indicates  the  existence  of  four  alcohols  included  in  the  formula 
C4H100,  two  primary,  one  secondary,  and  one  tertiary ;  thus, 


QUABTYL  OR  BUTYL  ALCOHOLS. 


533 


Primary. 


CH, 


CVH 


Secondary.       Tertiary. 
CH3  H8C1  CHS 

CH2  COH 

CH3 


GHt                 H2COH  H2COH 

H2COH  CH3 

Propyl  carbinol      Isopropyl  Methyl-ethyl     Trimethyl 

carbinol  carbinol            carbiuol. 


Propyl  Carbinol,  C 


rCH2CH2CH3 

loft 


. — This  alcohol  is  obtained  from  quartyl 


chloride,  C4II9C1  (produced  by  the  action  of  chlorine  or  quartane  or  diethyl, 
C14H10),  by  heating  that  chloride  with  potassium  acetate  arid  strong  acetic 
acid,  whereby  it  is  converted  into  quartyl  acetate,  and  treating  that  com- 
pound with  barium  hydrate.  The  alcohol  thus  prepared  yields  butyric 
acid  by  oxidation.* 


Isopropyl  Carbinol,  C 


rCH(CH3)2 


1H 

(o 


OH 


. — This  variety  of  primary  butyl-alcohol 


was  found  by  Wurtz  in  the  fusel-oil  obtained  by  fermenting  the  molasses 
of  beet-root  sugar.  To  separate  it,  this  oil  is  submitted  to  fractional  distil- 
lation, and  the  liquid  boiling  between  108°  and  118°  is  repeatedly  rectified 
over  potassium  hydrate,  till  it  boils  constantly  at  110°  C.  (230°  F.). 

Pure  isopropyl  carbinol  is  a  colorless  liquid,  having  an  odor  somewhat 
like  that  of  amyl  al<:ohol,  but  less  pungent,  and  more  vinous:  sp.  gr.  = 
"0-8032  at  18-5°  C.  (05°  F.).  It  dissolves  in  10£  times  its  weight  of  water, 
and  is  separated  therefrom,  as  an  oil,  by  calcium  chloride,  sodium  chloride, 
and  other  soluble  salts.  By  oxidation  it  is  converted  into  butyric  acid, 
C4II802,  whence  it  appears  to  be  a  primary  alcohol.  Formerly  also  this  alco- 
hol was  assumed  to  have  the  constitution  represented  by  the  first  of  the  for- 
jnuhe  above  given ;  in  other  words,  to  consist  of  propyl-carbinol,Cl{2(C3tt^OR ; 
and  all  the  other  alcohols  of  the  series  produced  by  fermentation  were  sup- 
posed to  be  similarly  constituted.  This  assumption,  however,  did  not 
rest  on  very  exact  experimental  data ;  and  from  recent  experiments  by 
Erlenmeyer,j"  it  appears  that  butyl  alcohol  produced  by  fermentation  con- 
sists of  isopropyl-carbinol,  CH2[CH(CH3)2]OH,  or  is  represented  by  the 
second  of  the  formulae  above  given  for  the  primary  four-carbon  alcohol. 

Isopropyl-carbinol  is  acted  upon  by  acids  and  other  chemical  reagents 
much  in  the  same  manner  as  common  alcohol  (methyl-carbinol).  With 
strong  sulphuric  acid  it  yields  quartyl- sulphuric  acid,  S04H(C4H9),  if  the  mix- 
ture is  kept  cool;  but  on  heating  the  liquid  quartern,  or  butylene,  C4H8  is 
given  off  mixed  with  sulphurous  oxide  and  carbon  dioxide.  Heated  with 
hydrochloric  acid  in  a  sealed  tube,  or  treated  with  phosphorus  pentachloride  or 
oxychloridc,  it  is  converted  into  quartyl  chloride,  C4H9C1,  or  chloroquartane, 
an  ethereal  liquid,  having  a  pungent  odor,  and  boiling  at  70°  C.  (158°  F.); 
quartyl  bromide,  C4H9Br,  obtained  in  like  manner,  boils  at  89°,  the  iodide 
C4II9i,  at  121°  C.  (250  F.).  The  iodide  is  decomposed  by  potassium  or 
sodium,  yielding  diquartijl  or  dibutyl,  C8H18,  probably : 

*  Ftr.Ju'h/en,  Ann.  Oh.  Pharm.  cxxx.,  233. 

f  Zcitsrlirift  fur  Cheinie,  Ncue  Koilio,  iii.  117.  The  details  of  the  investigation  arc  not  yet 
published. 

45* 


534 


ALCOHOLS   AND   ETHERS. 
H3C...         H    H   H    H        ...-CHS 


H.C 


H  H 


•CH, 


a  limpid  liquid,  lighter  than  water,  and  boiling  at  105°  C.  (221°  F.).     The 
same  hydrocarbon  is  obtained  by  the  electrolysis  of  valeric  acid,  C5H1002. 


Methyl-ethyl  Carbinol,  or  Secondary  Butylic  Alcohol,— C 


This 


alcohol  is  obtained  from  erythrite  (erythromannite),  a  saccharine  substance 
having  the  composition  of  a  tetratomic  alcohol,  C4H,004,  or  C4H6(OH)4. 
The  erythrite,  distilled  with  fuming  hydriodic  acid,  yields  methyl-ethyl- 
iodomethane,  or  secondary  butyl  iodide,  C(CH3)(C2H6)HI,  and  this  liquid, 
treated  with  moist  silver  oxide,  is  converted  into  methyl-ethyl  carbinol: 


C(CH3)(C2H5)HI 

Methyl-ethyl  iodo- 

methane. 


AgOH     =     Agl     -f- 
Silver  Silver 

hydrate.        iodide. 


C(CH3)(C2H5)HOH. 

Methyl-ethyl- 

carbinol. 


Methyl-ethyl  carbinol  is  a  colorless  oily  liquid,  having  a  strong  odor  and 
burning  taste,  a  specific  gravity  of  0-85  at  0°,  and  boiling  at  95°-98°  C. 
(208°-208°  F.)  (about  10°  C.  (18°  F.)  lower  than  the  primary  alcohol).  When 
heated  to  250°  C.  (482°  F.),  it  is  for  the  most  part  resolved  into  water  and 
quartene  or  butylene:  C4H100  =  OH2  -}-  C4H8. 

Methyl-ethyl  lodomethane,  or  Secondary  Butyl  iodide,  prepared  as  above,  or 
by  the  action  of  strong  hydriodic  acid  on  the  alcohol,  is  a  liquid  having  a 
pleasant  ethereal  odor,  a  specific  gravity  of  ]  -632  at  0°,  1-600  at  20°  C. 
(68°  F.)  and  1-584  at  30°  C.  (86°  F.).  It  boils  at  118°  C.  (244°  F.).  Bromine 
decomposes  it,  expelling  the  iodine  and  forming  quartene  dibromide 
C4H8C12.  When  distilled  with  alcoholic  potash  it  gives  off  quartene.  This 
tendency  to  give  off  the  corresponding  olefine  is  characteristic  of  all  the 
secondary  alcohols  and  ethers,  as  will  be  further  noticed  in  connection  with 
the  five-carbon  compounds. 


Trimethyl  Carbinol  or  Tertiary  Butyl  Alcohol,  C  |  \y^*\  is  produced  by 

treating  zinc  methide  with   carbonyl  chloride   (phosgene   gas)   or  acetyl 
chloride,  and  submitting  the  product  to  the  action  of  water.* 


=     ZnCl2     +  2COCH3C1 
Carbonyl              Zinc""             Zinc.  Acetyl 

chloride.  methide.  chloride.  chloride. 

+  C^ 


COCHgCl     -f     Zn(CH3)2    =     ZnO 

Acetyl 
chloride. 


Zinc 
methide. 

HOH 
Water. 


Zinc, 
oxide. 


Trimethyl 
chloromethane. 


=     HC1        -f 


Trimethyl-  Water.  Trimethyl 

chloromethane.  carbinol. 

When  acetyl  chloride  is  used,  the  formation  of  trimethyl-chloromethane 
takes  place  by  a  very  simple  reaction.     In  the  case  of  carbonyl  chloride  it 

*  Buitlerow,  Zeitschrift  fUr  Chem.  und  Pharm.  1864,  pp.  385,  702. 


QUINTYL    OR    AMYL    ALCOHOLS.  535 

takes  place  by  two  stages,  the  first  of  which  is  the  production  of  acetyl 
chloride.  The  other  tertiary  alcohols,  to  be  noticed  hereafter,  are  obtained 
by  similar  series  of  reactions. 

The  properties  of  this,  and  of  the  other  tertiary  alcohols,  have  not  been 
much  studied.  They  are  distinguished  from  the  primary  and  secondary 
alcohols  by  the  products  which  they  yield  with  oxidizing  agents.  Primary 
alcohols  of  the  series  Cn  H^-f  20,  oxidizing  with  chromic  acid,  yield,  as  already 
observed,  the  corresponding  acids,  Cn  H2nO2;  secondary  alcohols,  the  corre- 
sponding ketones.  Tertiary  alcohols,  on  the  other  hand,  are  split  up  by 
oxidation,  yielding  bodies  containing  a  smaller  number  of  carbon-atoms: 
thus,  trimethyl  carbinol  is  converted  by  oxidizing  agents  into  formic  and 
propionic  acids : 

C4H100     +     04    =    CH202    +     C3H602     +     OH2 
Trimethyl  Formic          Propionic 

carbinol.  acid.  acid. 


QUINTYL  OR  AMYL  ALCOHOLS  AND  ETHERS. 

The  formula  C5HI00  may  include  six  different  alcohols:  two  primary, 
three  secondary,  and  one  tertiary,  viz.  : 

rCH2CH2CH2CH3  fCH2CH(CH3)2 

Primary       C  \  ^  and  C  j  ** 

[OH  [OH 

Butyl  carbinol.  Isobutyl  carbinol.* 

fCH2CH2CH3          rCH(CH3)2  fCH2CH8 

Secondary   CJ£H'  ^H1^  and    C  j  °H'CH* 

[OH  [OH  [OH 

Methyl-propyl       Methyl-isopropyl  Diethyl 

carbinol.  carbinol.  carbinol. 

rCH2CH3 
Tertiary       Cj  ^3        Dimethyl-ethyl  carbinol. 

[OH3 

Of  these,  however,  only  two  have  been  distinguished  with  certainty,  viz., 
a  primary  alcohol,  produced  by  fermentation,  and  a  secondary  alcohol  ob- 
tained from  the  corresponding  olefine,  namely,  quintene  or  amylene. 

Isobutyl  Carbinol,  CH2(C4H9)OH.— This,  according  to  Erlenmeyer,  is  the 
ordinary  amyl  alcohol  produced  by  fermentation.  In  the  manufacture  of 
brandy  from  corn,  potatoes,  or  the  must  of  grapes,  the  ethyl  alcohol  is 
found  to  be  accompanied  by  an  acrid  oily  liquid  called  fusel-oil,  which  is 
very  difficult  to  separate  completely  from  the  ethyl  alcohol.  It  passes  over, 
however,  in  considerable  quantity  towards  the  end  of  the  distillation,  and 
may  be  collected  apart,  washed  by  agitation  with  several  successive  por- 
tions of  water  to  free  it  from  ethyl  alcohol,  and  re-distilled.  The  liquid 
thus  obtained  consists  chiefly  of  amyl  alcohol,  sometimes  mixed  with  pro- 
pylic,  butylic,  and  other  alcohols.  The  amyl  alcohol  maybe  obtained  pure  by 
fractional  distillation,  the  portion  which  passes  over  between  128°  and  132° 
C.  (2(')2°-2700  F. )  being  collected  apart.  Potato  fusel-oil  consists  almost  wholly 
of  ethyl  and  amyl  alcohols,  the  latter  constituting  the  greater  quantity. 

*  Tho  four-carbon  radical  derived  from  methyl  by  substitution  of  isopropyl  for  one  atom 
of  hydrogen  may  be  called  isoquartyl  or  isobutyl. 


536  ALCOHOLS   AND   ETHERS. 

Amyl  alcohol  is  an  oily,  colorless,  mobile  liquid,  having  an  odor  peculiar 
to  itself,  and  a  burning  acrid  taste.  Its  vapor  when  inhaled  produces 
coughing  and  oppression  of  the  chest.  Its  specific  gravity  is  0-8111.  When 
dropped  on  paper  it  forms  a  greasy  stain,  which,  however,  disappears  after 
a  while.  It  is  not  perceptibly  soluble  in  water,  but  floats  on  the  surface 
of  that  liquid  like  an  oil;  common  alcohol,  ether,  and  various  essential 
oils  dissolve  it  readily. 

Amyl  alcohol  usually  exerts  a  rotatory  action  on  polarized  light,  but  the 
rotatory  power  varies  considerably  in  different  samples.  Pasteur,  indeed, 
has  shown  that  ordinary  amyl  alcohol  is  a  mixture  of  two  isomeric  alcohols, 
having  the  same  vapor-density,  but  differing  in  their  optical  properties, 
one  of  them  turning  the  plane  of  polarization  to  the  right,  whereas  the 
other  is  optically  inactive.  They  are  separated  by  converting  the  crude 
amyl  alcohol  into  amylsulphuric  acid,  saturating  with  barium  carbonate, 
and  crystallizing  the  barium  amyl  sulphate  thus  formed.  The  salt  obtained 
from  the  active  amyl  alcohol  is  2J  more  soluble  than  that  obtained  from 
the  inactive  alcohol,  and  consequently  the  latter  crystallizes  out  first;  and 
by  precipitating  the  barium  from  the  solution  of  either  salt  with  sulphuric 
acid,  and  distilling  the  amylsulphuric  acid  thus  separated  with  water,  the 
corresponding  amyl  alcohol  is  obtained.  The  difference  of  optical  character 
between  the  two  alcohols  —  which  is  traceable  through  many  of  their  de- 
rivatives—  has  not  been  satisfactorily  explained;  but  it  probably  depends 
upon  the  arrangement  of  the  molecules,  rather  than  upon  that  of  the  atoms 
within  the  molecule. 

Vapor  of  amyl  alcohol  passed  through  a  red-hot  tube,  yields  a  mixture 
of  ethene,  propene,  quartene,  and  quintene  or  amylene. 

Amyl  alcohol  takes  fire  easily  and  burns  with  a  blue  flame.  When  ex- 
posed to  the  air  in  contact  with  platinum  black,  it  is  oxidized  to  valeric 
acid,  C5H1002.  The  same  acid  is  obtained  by  heating  amyl  alcohol  with  a 
mixture  of  potassium  bichromate  and  sulphuric  acid. 

CH2(C4H9)OH        -f        03       =       OH2        +        CO(C4H9)OH. 
Amyl  alcohol.  Valeric  acid. 

Amyl  alcohol,  heated  to  220°  C.  (423°  F.)  with  a  mixture  of  potassium 
hydrate  and  lime,  is  converted  into  valeric  acid,  with  evolution  of  hydrogen: 

C5H120        -f        KHO        =        C5H9K02        -f        H2. 
Amyl  al-  Potassium 

cohol.  valerate. 

Potassium  and  sodium  dissolve  in  amyl  alcohol  as  in  ethyl  alcohol,  yield- 
ing the  compound,  C6HUKO,  and  C5HnNaO,  which,  when  treated  with  amyl 
iodide,  yield  amyl  oxide  or  amyl  ether,  (C5Hn)20 ;  and  with  ethyl  iodide, 
ethyl-amyl  oxide,  (C2H5)(C5HU)6. 

Chlorine  acts  upon  amyl  alcohol  as  upon  ethyl  alcohol,  excepting  that  it 
finally  removes  only  four  atoms  of  hydrogen,  instead  of  five : 

C5HJ20      -f       3C12      =      4HC1      +      C5H8C120. 
Amyl  alcohol.  Chloramylal. 

Amyl  alcohol  is  acted  upon  by  acids,  like  common  alcohol,  yielding 
ethers.  When  mixed  with  strong  sulphuric  acid,  it  is  converted  into  amyl- 
sulphuric acid,  (C5H11)HS04;  and,  on  distilling  the  mixture,  amyl  oxide, 
(C6Hn)20,  passes  over,  together  with  amylene,  and  several  other  hydrocar- 
bons. 

AMYLENE,  on  QUINTENE,  C5H,0.  is  likewise  obtained,  together  with  quin- 
tane,  C5H12,  and  higher  homologues  of  both  these  bodies,  by  distilling  amyl 
alcohol  with  zinc  chloride.  It  is  a  colorless  liquid,  having  a  peculiar  and 
somewhat  unpleasant  odor;  boils  at  35°  C.  (95° F.),  and  when  set  on  fire, 


AMYL   ALCOHOLS   AND   ETHERS.  537 

burns  with  a  bright,  very  smoky  flame.— Vapor  of  amylene  is  completely 
absorbed  by  antimony  pentachloride  and  sulphuric  oxide.  —  Strong  sul- 
phuric acid  dissolves  amylene,  when  the  two  are  shaken  up  together,  but 
the  hydrocarbon  soon  separates  as  an  oily  layer,  which  however  consists, 
not  of  amylene,  but  of  diamylem  (par amylene},  C^H^.  Amylene  unites 
with  hydrochloric,  hydrobromic,  and  hydriodic  acid,  forming  compounds 
isomeric  with  amyl  chloride,  &c. 

AMYL  CHLORIDE,  C6H,,C1,  is  prepared  by  distilling  equal  weights  of  amyl 
alcohol  and  phosphorus  pentachloride,  washing  the  product  repeatedly 
with  alkaline  water,  and  rectifying  it  from  calcium  chloride.  Less  pure  it 
may  be  obtained  by  saturating  amyl  alcohol  with  hydrochloric  acid.  It  is 
a  colorless  liquid,  of  agreeable  aromatic  odor,  insoluble  in  water,  and  neu- 
tral to  test-paper:  it  boils  at  102°  C.  (216°  F.),  and  ignites  readily,  burn- 
ing with  a  flame  green  at  the  edges.  By  the  long-continued  action  of  chlo- 
rine, aided  by  powerful  sunshine,  it  is  converted  into  octochlorinated  amyl 
chloride,  or  nonochloroquintane,  C5H3C19,  a  volatile,  colorless  liquid,  smelling 
like  camphor :  the  whole  of  the  hydrogen  has  not  yet,  however,  been  re- 
moved. 

AMYL  BROMIDE,  C5TI,,Br,  is  a  volatile,  colorless  liquid,  heavier  than 
water.  It  is  obtained  by  distilling  amyl  alcohol,  bromine,  and  phosphorus 
together.  (See  ethyl  bromide,  p.  522.)  Its  odor  is  penetrating  and  allia- 
ceous. The  bromide  is  decomposed  by  an  alcoholic  solution  of  potash,  with 
reproduction  of  the  alcohol  and  formation  of  potassium  bromide. 

AMYL  IODIDE,  C5H,,I,  is  procured  by  distilling  a  mixture  of  15  parts  of 
amyl  alcohol,  8  of  iodine,  and  1  of  phosphorus.  It  is  colorless  when  pure, 
heavier  than  water,  volatile  without  decomposition  at  146°  C.  (295  F.),  and 
in  other  respects  resembles  the  bromide :  it  is  partly  decomposed  by  ex- 
posure to  light.  Heated  to  290°  C.  (554°  F.)  in  sealed  tubes,  with  zinc,  it 
yields  diamyl,  C10H22,  or  C5Hn .  C5Hn,  a  colorless  ethereal  liquid,  boiling  at 
155°  C.  (311°  F.),  and  isomeric,  or  identical  with  decane  (p.  474).  At  the 
same  time  there  is  formed  a  compound  of  zinc  iodide  with  zinc  amylide, 
Zn(C5Hu)2,  which  is  decomposed  by  contact  with  water,  yielding  zinc  oxide 
and  quintane  or  amyl  hydride  (p.  478) : 

Zn(C6Hn)2     +     OH2    =    ZnO     +     2C5H12. 

^  •  AMYL  OXIDE,  (C5Hn)20,   obtained  by  the  processes  already  mentioned, 
is  a  colorless  oily  liquid,  of  specific  gravity  of  0-779°,  and  boiling  at  176°. 

AMYL  SULPHURIC,  or  SULPHAMYLIC  ACID,  (Cr5Hn)HS04,  or  C5HnOS03H. — 
The  barium  salt  of  this  acid,  (C5H11)2Ba//(SO4t2 .  2  aq.,  prepared  like  the 
ethylsulphate  (p.  527).  crystallizes  on  evaporating  the  solution  in  small  bril- 
liant pearly  plates ;  the  difference  of  solubility  of  the  salts  prepared  from  op- 
tically active  and  optically  inactive  amyl  alcohol  has  already  been  mentioned. 
The  barium  may  be  precipitated  from  the  salt  by  dilute  sulphuric  acid,  and 
the  sulphamylic  acid  concentrated  by  spontaneous  evaporation  to  a  syrupy,  or 
even  crystalline  state:  it  has  an  acid  and  bitter  taste,  strongly  reddens 
litmus-paper,  and  is  decomposed  by  ebullition  into  amyl  alcohol  and  sul- 
phuric acid.  The  potassium  salt  forms  groups  of  small  radiated  needles, 
very  soluble  in  water.  The  sulphamylates  of  calcium  and  lead  are  also  sol- 
uble and  crystallizable. 

Amyl  sulph-hydrate,  C5Hj,SH,  and  Amyl  sulphide,  (C5Hn)2S,  have  likewise 
been  obtained :  they  resemble  the  ethyl  compounds  in  their  properties  and 
reactions. 

Fusel-oil  or  Grain-spirit. — The  fusel  oil,  separated  in  large  quantities 
from  grain-spirit  by  the  London  rectifiers,  consists  chiefly  of  amyl  alcohol 


538  ALCOHOLS   AND   ETHERS. 

mixed  with  ethyl  alcohol  and  water.  Sometimes  it  contains  in  addition 
more  or  less  of  the  ethyl-  or  amyl-compounds  of  certain  fatty  acids  thought 
to  have  been  identified  with  cenanthylic  and  palmitic  acids.  These  last- 
named  substances  form  the  principal  part  of  the  nearly  solid  fat  produced 
in  this  manner  in  whiskey  distilleries  conducted  on  the  old  plan.  Mulder 
has  described,  under  the  name  of  corn-oil,  another  constituent  of  the  crude 
fusel-oil  of  Holland:  it  has  a  very  powerful  odor,  resembling  that  of  some 
of  the  umbelliferous  plants,  and  is  unaffected  by  solution  of  caustic  potash. 
According  to  Mr.  Rowney,  the  fusel-oil  of  the  Scotch  distilleries  contains 
in  addition  a  certain  quantity  of  capric  acid,  C10H2002.  Amyl  alcohol,  in 
addition  to  butyl  alcohol,  has  been  separated  from  the  spirit  distilled  from 
beet-molasses,  and  from  artificial  grape-sugar  made  by  the  aid  of  sulphu- 
ric acid.  Although  much  obscurity  yet  hangs  over  the  history  of  these 
substances,  it  is  generally  supposed  that  they  are  products  of  the  fermen- 
tation of  sugar,  and  have  an  origin  contemporaneous  with  that  of  common 
alcohol. 

H3C  CH3 

V 
CH 

Methyl-isopropyl  carbinol,  CH(CH3)[CH(CH3)2]'OH  =        |          or  Amyl- 

HCOH 

CH3 
ene  hydrate,   (C6H10)"JQH'  —  This  is  a  secondary  alcohol  produced  from 

amylene,  C5H10,  by  combining  that  substance  with  hydriodic  acid,  and  de- 
composing the  resulting  hydriodide,  C5H,0.HI,  with  moist  silver  oxide, 
whereby  silver  iodide  and  amylene  hydrate  are  obtained : 

2(C6H10.HI)  +  Ag20  +  H20  =  2AgI  +  2[C5H10.H(OH)]. 

A  portion  of  the  hydriodide  is  at  the  same  time  resolved,  by  the  heat 
evolved  in  the  reaction,  into  hydriodic  acid  and  amylene ;  and,  on  submit- 
ting the  resulting  liquid  to  fractional  distillation,  the  amylene  passes  over 
first,  and  then,  between  105°  and  108°  C.  (221°  and  226°  F.),  the  amylene 
hydrate  or  methyl-isopropyl  carbinol. 

This  alcohol  is  a  liquid  having  a  specific  gravity  of  0-829  at  0°,  and  a 
pungent  ethereal  odor,  quite  distinct  from  that  of  ordinary  amyl  alcohol. 
Heated  with  strong  sulphuric  acid,  it  is  converted,  not  into  amylsulphuric 
acid,  but  into  hydrocarbons  polymeric  with  amylene,  viz.,  diamylene,  or 
decene,  C^H^,  and  triamylene,  or  quindecene,  Gl5H-go.  Hydriodic  acid  con- 
verts it,  at  ordinary  temperatures,  into  amylene  hydriodide,  C5H,0.HI, 
boiling  at  130°  C.  (266°  F.),  (amyl  iodide  at  146°  C.  [295°  F.]).  Hydrochloric 
acid  converts  it  (even  at  0°)  into  amylene  hydrochloride,  C5H10.HC1,  having 
a  boiling  point  10°  C.  (18°  F.)  below  that  of  amyl  chloride.  On  mixing  it 
with  two  atoms  of  bromine  at  a  very  low  temperature,  a  red  liquid  is  formed, 
which,  as  soon  as  it  attains  the  ordinary  temperature  of  the  air,  is  resolved 
into  water  and  amylene  bromide.  Heated  for  some  time  to  100°  C.  with  strong 
acetic  acid,  it  yields  amylene,  together  with  a  small  quantity  of  amylene 
acetate.  Sodium  dissolves  in  amylene  hydrate  with  evolution  of  hydrogen, 
forming  a  colorless  translucent  mass,  which  has  the  composition  C5H,0NaOH, 
and  is  decomposed  by  amylene  hydriodide  in  the  manner  shown  by  the 
equation: 

C6H10NaOH     -f     C5H10HI    =     C5H10    +     C5H10H(OH)     +     Nal. 

Sodium  com-  Amylene        Amylene.  Amylene 

pound.  hydriodide.  hydrate. 

From  these  reactions  it  is  apparent  that  amylene   hydrate  or  methyl- 


HEXYL    ALCOHOLS    AND    ETHERS.  539 

isopropyl  carbinol  is  especially  distinguished  from  amyl  alcohol  or  butyl 
carbinol,  by  the  facility  with  which  it  gives  up  the  corresponding  olefiue. 
This  peculiarity  is  exhibited  also  by  all  the  secondary  alcohols  of  the  series. 
These  alcohols  indeed  may  be  regarded  as  connecting  links  between  the 
primary  monatomic  alcohols  and  the  secondary  alcohols,  or  glycols;  e.  g.  : 


C5Hn(OH)  C5 

Amyl  alcohol.  Amylene  Amylene  glycoL 

hydrate. 


SEXTYL,  OR  HEXYL,  ALCOHOLS  AND  ETHERS. 

The  number  of  possible  modifications  of  an  alcohol  increases  with  the 
number  of  carbon-atoms  in  its  molecular  formula.  Thus  we  have  seen  that 
there  may  be  two  propyl  alcohols,  C3H80,  four  butyl  alcohols,  C4H100,  and 
six  amyl  alcohols,  C5H,20.  The  six-carbon  formula,  C6H140,  will  in  like 
manner  be  found  to  include  ten  isomeric  alcohols — three  primary,  four 
secondary,  and  three  tertiary ;  but  as  the  manner  in  which  these  modifica- 
tions arise  has  been  sufficiently  explained  in  the  preceding  pages,  the 
further  development  of  the  theoretical  formulae  may  be  left  as  an  exercise 
for  the  student. 

The  number  of  modifications  of  the  six-carbon  alcohol  actually  known,  is 
five ;  of  which  two  are  primary,  one  is  secondary,  and  the  remaining  two 
are  tertiary. 

Primary  Hexyl  Alcohols. — The  normal  alcohol,  or  Amyl-carbinol,  G6HI3 


(OH),  or  C  \  H2      ,  is   prepared   by  treating   sextane,  or  hexyl  hydride, 

(OH 

C6H,4,  obtained  from  American  petroleum,  with  chlorine,  converting  the 
resulting  hexyl  chloride,  C6H13C1,  into  hexyl  acetate,  C6H13(OC2II30), 
by  treatment  with  silver  acetate,  and  distilling  the  hexyl  acetate  with 
potash.  The  hexyl  alcohol  thus  prepared  boils  at  about  150°  C.  (302°  F.), 
and  smells  like  arnyl  alcohol. 

Another  primary  hexyl  alcohol  was  found  by  Faget  in  fusel-oil.  The 
statements  respecting  it  are  not  very  exact,  but  as  it  is  produced  by 
fermentation,  it  is  probably  constituted  like  ordinary  amyl  alcohol,  and 

C  CH2CH2CH(CH3)2 
therefore  in  the  manner  represented  by  the  formula,  C  \  H 

(OH 

Both  these  alcohols,  when  oxidized  by  chromic  acid,  yield  caproic  acid, 

(  CH2CH(CH3)2 

1     /~^1T 

Secondary  HexylAlcohol,probablyMethyl-isobutylcarbinol,C  -I  g  * 

(  OH 
or  Hexylene  hydrate,  C6H12  j  ^  —  This   alcohol,  discovered  by  Wanklyn 

and  Erlenmeyer,*  is  produced  from  mannite,  a  saccharine  body  having  the 
composition  of  a  hexatomic  alcohol,  C6H8(OH)6,  by  treating  that  substance 
with  a  large  excess  of  very  strong  hydriodic  acid,  whereby  it  is  converted 
into  secondary  hexyl  iodide,  or  hexylene  hydriodide,  C6H,2.HI: 

C6H8(OH)6     +     11  III     =     C6H12HI     -f-     60H2     -f-     5I2; 
and  digesting  this  hydriodide  with  silver  oxide  and  water: 

C12H12HI     +     H20     +     Ag20     =     2AgI     +     C6H12H(OH). 
*  Journal  of  the  Chemical  Society  [2],  i.  221. 


540  ALCOHOLS   AND    ETHERS. 

It  is  a  viscid  liquid,  having  a  pleasant,  refreshing  odor;  boils  at  137°; 
has  a  sp.  gr.  of  0-8327  at  0°,  0-8209  at  16°,  and  0-7482  at  99°,  so  that  it  ex- 
pands somewhat  rapidly  by  heat.  Strong  hydrochloric  acid  converts  it 
into  the  corresponding  hydrochloride,  C6H12HC1,  which  boils  at  120°  C. 
(248°  F.),  and  yields  hexylene  when  digested  at  100°  C.,  with  alcoholic 
potash. 

Hexylene  hydrate,  or  methyl-isobutyl  carbinol,  is  converted  by  oxidation 
with  potassium  bichromate  and  sulphuric  acid,  into  a  ketone,  C6H120  = 

CH2CH<CH3)2 
C-|  CH.  ,  which  does  not  absorb  oxygen  from  the  air;  but,  when 


rCH2( 

JCH3 

lo/> 


further  treated  with  the  oxidizing  mixture  just  mentioned,  yields  butyric, 
acetic,  and  carbonic  acids,  and  water.  These  reactions  show  that  the  al- 
cohol in  question  is  a  secondary  alcohol. 

Tertiary  Hexyl  Alcohols.  —  Three  of  these  alcohols  are  possible,  namely : 
Methyl-diethyl  carbinol 


rCH2(C2H6) 

Propyl-dimethyl  carbinol        C  \  (CH3)2 

(OH 

(CH(CH3)2 
Isopropyl-dimethyl  carbinol    C  -1  (CH8)3 

(OH. 

The  third  has  not  yet  been  obtained.     The  first  is  prepared  by  treating 
zinc  ethyl  with  acetyl  chloride,    and  decomposing  the  resulting  methyl- 

f  CH3 
diethyl-chlorethane,  C  4  (C2H6)2,  with  water ;  the  second  by  proceeding  in 

(  Cl 
like  manner  with  zinc  methyl  and  butyryl  chloride,  CO(CSH?)C1. 


SEPTYL,  OR  HBPTYL,  ALCOHOLS  AND  ETHERS. 
Of  these  compounds  only  the  normal  primary  alcohol,  C7Hi6(OH),  or 

Hexyl  carbinol,  C  -|  H2      ,  is  known  with  certainty.     It  is  prepared,  either 


by  the  action  of  nascent  hydrogen  (evolved  by  the  action  of  sodium  amal- 
gam on  water)  on  oenanthylic  aldehyde  (oenanthol) : 

CH140        +        Hj        =        C7H160; 

Aldehyde.  Alcohol. 

or  from  septane  or  heptyl  hydride,  C7H,6,  in  the  same  manner  as  hexyl 
alcohol  from  hexyl  hydride  (p.  539).  It  is  a  colorless,  oily  liquid,  insoluble 
in  water ;  but  its  properties  are  not  much  known. 

Another  heptyl  alcohol  was  separated  by  Faget  from  fusel-oil ;  and  a 
third  has  been  said  by  several  chemists  to  be  obtained,  together  with  octyl 
alcohol,  by  distilling  castor-oil  with  excess  of  potash ;  but,  according  to 
the  most  trustworthy  experiments,  there  is  but  one  alcohol  obtained  by  this 
process,  viz.,  an  8-carbon  alcohol. 


OCTYL    ALCOHOLS   AND   ETHERS.  541 


OCTYL  ALCOHOLS  AND  ETHERS. 

Alcohols  having  the  composition  C8H,80  are  obtained:  1.  From  the  octane 
or  octyl  hydride  of  American  petroleum,  by  the  series  of  processes  already 
indicated  in  the  case  of  hexyl  alcohol.  2.  By  distilling  castor-oil  with 
potash.  The  first  is  an  oily  liquid,  having  a  specific  gravity  of  0-82G  at 
16°,  and  boiling  at  180°-184°  C.  (356°-363°  F.).  Its  structure  is  not  exactly 
known,  but  it  closely  resembles  the  alcohol  obtained  from  castor-oil,  both 
in  its  physical  properties  and  in  its  reactions. 

The  chloride,  C8fl,7Cl,  obtained  by  the  action  of  chlorine  on  octane,  is 
also  very  similar  in  its  properties  to  that  obtained  from  the  alcohol  of 
castor-oil  by  the  action  of  phosphorus  pentachloride. 

Secondary  Octyl  Alcohol,  or  Methyl-hexyl  Carbinol, 

C6H,3  H     H    H    H    H        XCH3 

CH3         or      H3C— C— C— C— C— C  <' 

OH  OHH   H    H  ''•'  CH3 

This  alcohol  is  produced  by  heating  castor-oil  with  excess  of  solid  potas- 
sium hydrate.  Castor-oil  contains  ricinoleic  acid,  CjgH^Og;  and  this  acid, 
when  heated  with  potash,  yields  free  hydrogen,  a  distillate  containing 
methyl-hexyl  carbinol,  together  with  products  of  its  decomposition,  and  a 
residue  of  potassium  sebate : 

C18H3403    +     2KOH    =    C8H180     +     C10H16K204    +     Hr         , 
Ricinoleic  Octyl  Potassium 

acid.  alcohol.  sebate. 

To  separate  the  alcohol,  the  distillate  is  repeatedly  rectified  over  fused 
potash,  the  portion  boiling  below  200°  C.  (392°  F.)  only  being  collected: 
this  liquid,  subjected  to  fractional  distillation,  yields  a  portion  boiling  at 
181°,  which  is  the  pure  secondary  octyl  alcohol.  The  portions  of  the  orig- 
inal distillate  having  a  lower  boiling  point,  consist  of  olefines,  amongst 
which  octylene,  C8HI6,  boiling  at  125°  C.  (257°  F.),  preponderates.* 

Methyl-hexyl  carbinol  is  a  limpid  oily  liquid,  having  a  strong  aromatic 
edor,  and  making  grease  spots  on  paper.  It  has  no  action  on  polarized 
light.  It  has  a  specific  gravity  of  0-823  at  17°,  and  boils  at  181°  C.  (358° 
F.).  It  is  insoluble  in  water,  but  dissolves  in  alcohol,  ether,  wood-spirit, 
and  acetic  acid.  It  mixes  with  sulphuric  acid,  forming  octyl-sulphuric  acid, 
C8H,7HS04,  generally  also  octylene  and  neutral  octyl-sulphate.  Fused  zinc 
chloride  converts  it  into  octylene.  With  potassium  and  sodium  it  yields 
substitution-products. 

Methyl-hexyl  carbinol,  oxidized  with  potassium  bichromate  and  sulphu- 
ric acid,  yields  the  corresponding  ketone,  viz.,  methyl-oenanthol, 


!C*  H" 
C°H313;  thus, 
0" 


-f     0    =    OH2    + 

OH 

Methyl-hexyl  Methyl 

carbinol.  oenanthol. 

*  ,SbA0rkm»ier,  Proceedings  of  tho  Royal  Society,  xvi.  376. 

46 


542  ALCOHOLS   AND   ETHERS. 

By  the  prolonged  action  of  the  oxidizing  mixture,  this  ketone  is  further 
oxidized  to  caproic  and  acetic  acids : 

C8H180     +     04    =     C6H1208     +     C2H402    +     OHr 
Methyl  Caproic  Acetic 

renantliol.  acid.  acid. 

These  reactions  show  that  the  alcohol  produced  from  castor-oil  is  a  sec- 
ondary alcohol ;  and  from  further  considerations,  for  which  we  must  refer 
to  Schorlemmer's  paper  above  cited,  it  is  inferred  to  contain  the  radical 
isopropyl,  that  is,  to  have  one  of  its  carbon-atoms  directly  combined  with 
three  others. 

Octyl  chloride,  C8H17C1,  produced  by  the  action  of  phosphorus  pentachlo- 
ride  on  the  alcohol,  has  a  specific  gravity  of  0-892  at  18°  C.  (64°  F.),  and 
boils  at  175°  C.  (347°  F.).  Heated  with  alcoholic  potash,  it  yields  octene, 
C8H16;  by  alcohol  and  potassium  acetate,  it  is  converted  into  octene  and 
octyl  acetate. 


Nonyl  Alcohol,  C9H200,  or  Octyl  Carbinol,  C  |  Ha     ,  is  obtained  by  the 

Oil 

series  of  reactions  above  described  from  nonane  or  nonyl-hydride,  which 
is  one  of  the  constituents  of  American  petroleum,  and  likewise  occurs,  to- 
gether with  nonene,  C9H18,  in  that  portion  of  the  liquid  obtained  by  dis- 
tilling amyl  alcohol  with  zinc  chloride,  which  boils  between  134°  and  150° 
C.  (273°  and  302°  F.).  Nonyl  alcohol  boils  at  about  200°.  Nonyl  chloride, 
C9H,9C1,  has  a  specific  gravity  of  0-899  at  16°  C.  (60°  F.),  and  boils  at  196°. 

The  alcohols  of  the  series,  CnH2n-f20,  containing  from  10  to  15  carbon- 
atoms,  are  not  known,  but  compound  ethers  containing  12  and  14  carbon- 
atoms  appear  to  occur  in  spermaceti. 

Sexdecyl,  or  Cetyl  Alcohol,  C16H340=:C16H33(OH),  also  called  Ethal,  is  ob- 
tained from  spermaceti,  a  crystalline  fatty  substance  found  in  peculiar  cav- 
ities in  the  head  of  the  sperm  whale  (Physeter  macroccphalus}.  This  sub- 
stance consists  of  cetyl  palmitate,  C32H6402,  or  C,6H3102  CjgHgg,  and  when 
heated  for  some  time  with  solid  potash,  is  resolved  into  potassium  palmitate 
and  cetyl  alcohol : 

CwHsA.CrtHa  +  KOH  =  C16H3102K  +  C16H33fOH). 

The  cetyl  alcohol  is  dissolved  out  from  the  fused  mass  by  alcohol  and  ether, 
and  purified  by  several  crystallizations  from  ether. 

Cetyl  alcohol,  or  ethal,  is  a  white  crystalline  mass,  which  melts  at  about 
50°,  and  crystallizes  by  slow  cooling  in  shining  laminae.  It  has  neither 
taste  nor  smell,  is  insoluble  in  water,  but  dissolves  in  all  proportions  in 
alcohol  and  ether.  When  heated  it  distils  without  decomposition.  With 
sodium  it  gives  off  hydrogen  and  yields  sodium  cetylate,  O^H^RO.  It  is 
not  dissolved  by  aqueous  alkalies ;  but  when  heated  with  a  mixture  of  pot- 
ash and  lime,  it  gives  off  hydrogen,  and  is  converted  into  palmitic  acid: 

C^O     +     KOH    =    C,6H3102K    -f     2H2. 

Distilled  with  phosphorus  pentachloride  it  yields  cetyl  chloride,  C,6H3301,  a 
limpid  oily  liquid,  having  a  specific  gravity  of  0-8412  at  12°,  and  distilling 
with  partial  decomposition  at  a  temperature  above  200°.  Cetyl  iodide, 
CjeHggl,  obtained  by  treating  the  alcohol  with  iodine  and  phosphorus,  is  a 
solid  substance  which  melts  at  22°,  dissolves  in  alcohol  and  ether,  and 
crystallizes  from  alcohol  in  interlaced  laminse. 

According  to  Heintz,  cetyl  alcohol,  or  ethal,  prepared  as  above,  is  not 
a  definite  compound,  but  a  mixture  of  sexdecyl  alcohol,  C16H!402,  with 
small  quantities  of  three  other  alcohols  of  the  same  series,  containing  re- 


ALCOHOLS   AND   ETHERS.  543 

spectively  12,  14,  and  18  atoms  of  carbon,  inasmuch  as,  when  fused  with 
potash-lime,  it  yields  the  corresponding  fatty  acids  CnH2n02. 

Ceryl  Alcohol,  C^H^O  =  C27H65(OH)  ;  also  called  Cerolic  alcohol  and 
Cerotin.  —  This  alcohol  is  obtained  from  Chinese  wax  or  Pela,  a  secretion 
enveloping  the  branches  of  certain  trees  in  China,  and  supposed  to  be  pro- 
duced by  the  puncture  of  an  insect.  This  wax  consists  mainly  of  ceryl 
cerotate,  C27H5302  .  C27H55,  and  is  decomposed  by  fused  potash  in  the  same 
manner  as  spermaceti,  yielding  potassium  cerotate  and  ceryl  alcohol: 


C^O.K    +    C27H56(OH). 

On  digesting  the  fused  mass  with  boiling  water,  a  solution  of  potassium 
cerotate  is  obtained,  holding  ceryl  alcohol  in  suspension  ;  and  by  precipi- 
tating the  cerotic  acid  with  barium  chloride  and  treating  the  resulting  pre- 
cipitate with  alcohol,  the  ceryl  alcohol  dissolves,  and  may  be  purified  by 
repeated  crystallization  from  alcohol  or  ether.  It  then  forms  a  waxy  sub- 
stance, melting  at  97°  C.  (206°  F.).  Heated  with  potash-lime,  it  gives  off 
hydrogen,  and  is  converted  into  potassium  cerotate.  At  very  high  temper- 
atures it  distils,  partly  undecomposed,  partly  resolved  into  water  and  cero- 
tene,  C27H54;  by  this  character  it  would  appear  to  be  related  to  the  secon- 
dary alcohols.  With  sulphuric  acid  in  excess,  it  forms  hydrated  neutral  ceryl 
sulphate,  (C27H55)2S04.  OH2. 

Myricyl  Alcohol,  C30H620  =  C^,  (OH).  —This  alcohol,  the  highest 
known  member  of  the  series,  Cn  H2n+2O,  is  obtained  from  myricin,  the  por- 
tion of  common  bees'-wax  which  is  insoluble  in  boiling  alcohol.  Myricin 
consists  of  myricyl  palmitate,  C16H3102  .  C^II^,  and  when  heated  with 
potash  is  decomposed  in  the  same  manner  as  spermaceti  and  Chinese  wax, 
yielding  potassium  palmitate  and  myricyl  alcohol.  On  dissolving  the  pro- 
duct in  water,  precipitating  with  barium  chloride,  exhausting  the  precipi- 
tate with  boiling  alcohol,  and  dissolving  the  substance  deposited  from  the 
alcohol  in  mineral  naphtha,  pure  myricyl  alcohol  separates  as  a  crystalline 
substance,  having  a  silky  lustre.  When  heated,  it  partly  sublimes  unal- 
tered, and  is  partly  resolved  (like  ceryl  alcohol)  into  water  and  melene, 
C30H60.  With  strong  sulphuric  acid  it  yields  myricyl  sulphate.  Heated  with 
potash  lime,  it  gives  off  hydrogen,  and  is  converted  into  potassium  melissate  : 

C30H620     +     KOH    =    C30H5902K     +     2H2. 

The  mother-liquor  from  which  the  myricyl  alcohol  has  crystallized  out, 
as  above  mentioned,  retains  a  small  quantity  of  an  isomeric  alcohol,  which 
melts  at  72°  C.  (162°  F.),  and  when  treated  with  potash-lime  yields  an  acid 
containing  a  smaller  proportion  of  carbon. 


/?.  Monatomic  Alcohols,  CnH2nO,  or  CnII2Il_1OH. 
Two  alcohols  of  this  series  are  known,  viz. : 

Vinyl  alcohol,  C2H40  =  C2IT3(OII). 
Allyl  alcohol,  C3H40  ==  C3II5(OH). 

The  first,  discovered  by  Berthelot*  in  I860,  is  produced  by  combining 
ethine  or  acetylene  with  sulphuric  acid,  and  distilling  the  product  with 
water,  just  as  in  the  preparation  of  ethyl  alcohol  from  ethene : 

SOJIII  -f        C2H2        =  S04H(C2H3). 

Sulphuric  acid.  Ethine.  Vinyl-sulphuric  acid. 

*  Comptes  Rendus,  i.  805. 


544  ALCOHOLS   AND   ETHERS. 

S04H(C2H3)       +        HOH        =        S04HH        -f        C2H3(OH) 
Viriyl-sul-  Water.  Sulphuric  Vinyl 

pliuric  acid.  acid.  alcohol. 

It  is  an  easily  decomposable  liquid,  having  a  highly  pungent  odor,  some- 
what more  volatile  than  water,  soluble  in  10  to  15  parts  of  that  liquid,  and 
precipitated  from  the  solution  by  potassium  carbonate.  Its  chemical  reac- 
tions have  not  been  much  examined,  but  it  is  probably  a  secondary  alcohol, 

CH2 
represented  by  the  formula  ||  .     It  is  isomeric  with  acetic  aldehyde 

CHOH 

and  ethylene  oxide  (p.  484).  The  univalent  radical  vinyl,  C2H3,  which  may 
be  supposed  to  exist  in  it,  is  related  to  the  trivalent  radical  ethenyl  (p.  468), 
in  the  same  manner  as  allyl  to  propenyl  (see  below). 

CH2 
Allyl  Alcohol,  C3H6,  =  C3H6(OH)  =  CH        .— This  alcohol,  discovered 

CH2OH 

by  Cahours  and  Hofmann  *  in  1856,  may  be  supposed  to  contain  the 
univalent  radical  allyl,  C3H5,  derived  from  a  saturated  hydrocarbon, 
CH2 

CH,  by  abstraction  of  one  atom  of  hydrogen,  and  isomeric  with  the  triva- 

CH3 

lent  radical  propenyl,  (C3H2)///,  derived  in  like  manner  from  the  bivalent 
—  CH2 

radical  propene,  — CH  ,  or  from  the   saturated  hydrocarbon  propane, 


CH3 

CH2,  by  abstraction  of  three  atoms  of  hydrogen.     Allyl  and  propenyl  com- 

1 
CH3 

pounds,  indeed,  are  easily  converted  one  into  the  other  by  addition  or  sub- 
traction of  two  atoms  of  a  monad  element  or  radical. 

To  obtain  the  alcohol,  allyl  iodide  is  first  prepared  by  the  action  of  phos- 
phorus tetriodide  on  propenyl  alcohol  (glycerin) : 

2(C8HB)'"(OH)8    +     P2I4    =    2C3H5I     -f     2P(OH)3    +     I2. 
Propenyl  Allyl  Phosphorous 

alcohol.  iodide.  acid. 

The   allyl  iodide  is  next  decomposed  by  silver  oxalate,  yielding   allyl 
oxalate : 

2C3H6I         +         C204Ag2        =        2AgI         +         C204(CaH5)2; 
Allyl  Silver  Silver  Allyl 

iodide.  oxalate.  iodide.  oxalate. 

and  the  allyl  oxalate  is  decomposed  by  ammonia,  yielding  oxamide  and 
allyl  alcohol: 

CAfCA),        +        2NH3        =        (C202)"(NH2)2  +       2C3H5(OH) 

Allyl  Ammonia.  Oxamide.  Allyl 

oxalate.  alcohol. 

*  Phil.  Trans.,  1837,  p.  1. 


ALLYL   ALCOHOLS   AND   ETHERS.  545 

Ally!  alcohol  is  a  colorless  liquid,  having  a  pungent  odor  and  a  spirituous 
burning  taste.  It  mixes  in  all  proportions  with  water,  common  alcohol, 
and  ether;  boils  at  103°  C.  (217°  F.)  ;  burns  with  a  brighter  flame  than 
common  alcohol. 

Allyl  alcohol  is  a  primary  alcohol,  similar  in  all  its  ordinary  reactions  to 
ethyl  alcohol.  By  oxidation  in  contact  with  platinum-black,  or  more 
quickly  by  treatment  with  potassium  bichromate  and  sulphuric  acid,  it  is 
converted  into  acrylic  aldehyde  (acrolein),  C3H50,  and  acrylic  acid,  C3H402, 
compounds  related  to  it  in  the  same  manner  as  common  aldehyde  and  acetic 
acid  to  ethyl  alcohol.  Heated  with  phosphoric  oxide,  it  yields  allylene, 
C3II4.  With  potassium  and  sodium  it  yields  substitution-products.  Strong 
sulphuric  acid  converts  it  into  allyl-sulphuric  acid.  With  the  bromides  and 
chlorides  of  phosphorus  it  yields  allyl  bromide,  C3H5Br,  and  allyl  chloride, 

CjjIIeCl. 

ALLYL  BROMIDES. — The  monobromide,  C3H5Br,  prepared  as  just  men- 
tioned, or  by  distilling  propene  bromide,  C3H6Br2,  with  alcoholic  potash,  is 
a  liquid  of  sp.  gr.  1-47,  and  boiling  at  62°  C.  (144°  F.).  A  tribromide  of 
allyl,  C3H5Br3,  is  obtained  by  adding  bromine  to  the  mono-iodide  in  a  vessel 
surrounded  by  a  freezing  mixture.  It  is  a  liquid  of  sp.  gr.  1-436  at  23°  C. 
(73°  F.),  boiling  at  217°  C.  (422°  F.),  and  solidifying  when  cooled  below 
10°  C.  (50°  F.).  It  is  isomeric  with  propenyl  bromide  or  tribromhydrin, 
obtained  by  the  action  of  phosphorus  pentabromide  on  glycerin. 

A  diallyl  tetrabromide,  C6H,0Br4,  is  formed  by  the  direct  combination  of 
diallyl  (p.  487)  with  bromine ;  it  is  a  crystalline  body,  melting  at  37°. 

ALLYL  IODIDES. — The  mono-iodide,  C3H5I,  obtained,  as  above  described, 
by  distilling  glycerin  with  phosphorus  tetriodide,  is  a  liquid  of  sp.  gr. 
1-780  at  16°  C.  (60°  F.),  and  boiling  at  100°  C.  (320°  F.),  It  is  decom- 
posed by  sodium,  with  formation  of  diallyl,  C6H10.  By  the  action  of  zinc 
or  mercury  and  hydrochloric  or  dilute  sulphuric  acid,  it  is  converted  into 
propene  (or  allyl  hydride)  : 

2C3H5I     -f     Zn2     -f     2HC1    =     ZnCl2     -f     ZnI2     -f     2C3H6. 

Diallyl  tetriodide,  C6H,0I4,  is  a  crystalline  body  obtained  by  dissolving 
iodine  in  diallyl  at  a  gentle  heat. 

ALLYL-SULPHURIC  ACID,  S04H(C3H5),  is  produced  by  adding  allyl  alcohol 
to  strong  sulphuric  acid.  The  solution,  diluted  with  water  and  neutralized 
with  barium  carbonate,  yields  barium  allylsulphate,  (S04)2Ba//(C3H5)2. 

ALLYL  OXIDE,  (C3H5)20,  is  produced  by  the  action  of  allyl  iodide  on 
potassium  allylate  (the  gelatinous  mass  obtained  by  dissolving  potassium 
in  allyl  alcohol) : 

C3H5OK         -f        C,H5I        ==        KI  +         (C3H5)20. 

It  is  a  colorless  liquid,  boiling  at  82°. 

ALLYL  SULPHIDE,  (C3H5)2S. — This  compound  exists,  together  with  a 
small  quantity  of  allyl  oxide,  in  volatile  oil  of  garlic,  and  is  formed  arti- 
ficially by  distilling  allyl  iodide  with  potassium  monosulphide : 

2C3H5I         +         K2S         =         2KI         +         (C,II6)2S. 

To  prepare  it  from  garlic,  the  sliced  bulbs  are  distilled  with  water,  and 
the  crude  oil  thus  obtained  —  which  is  a  mixture  of  the  sulphide  and  oxide 
of  allyl  —  is  subjected  to  the  action  of  metallic  potassium,  renewed  until  it 
is  no  longer  tarnished,  whereby  tho  allyl  oxide  is  decomposed,  after  which 
the  sulphide  may  he  obtained  pure  by  redistillation.  In  this  state  it  forms 
46  * 


546  ALCOHOLS    AND    ETHERS. 

a  colorless  liquid,  lighter  than  water,  of  high  refractive  power,  possessing 
in  a  high  degree  the  peculiar  odor  of  the  plant,  and  capable  of  being  dis- 
tilled without  decomposition.  Allyl  sulphide,  dissolved  with  alcohol  and 
mixed  with  solutions  of  platinum,  silver,  and  mercury,  gives  rise  to  crys- 
talline compounds,  consisting  of  a  double  sulphide  of  allyl  and  the  metal, 
either  alone  or  mixed  with  a  double  chloride. 

Volatile  oil  of  mustard  consists  of  allyl  sulphocyanate,  C3H6 .  CNS,  and 
will  be  described  in  connection  with  the  sulphocyanic  ethers. 

ALLYL  SULPH-HYDRATE,  or  ALLYL  MERCAPTAN,  C3H6(SH),  obtained  by 
distilling  allyl  iodide  with  potassium  sulph-hydrate,  is  a  volatile  oily  liquid, 
having  an  odor  like  that  of  garlic  oil,  but  more  ethereal ;  boiling  at  90° 
C.  (194°  F.).  It  attacks  mercuric  oxide,  like  ethyl  mercaptan,  forming  the 
compound  (C3H5)2S2Hg". 


y.  Monatomic  Alcohols,  Cn.Hg^O,  or  CnH2n_3OH. 
Only  one  alcohol  of  this  series  is  at  present  known,  viz. : 
Camphol,  C10H180      =      C10H17(OH). 

Of  this  compound  there  are  several  physical  modifications,  distinguished 
from  one  another  by  their  action  on  polarized  light. 

One  variety,  called  JBorneol  or  JSorneo  camphor,  is  obtained  from  Drya- 
balanops  camphora,  being  found  in  cavities  of  the  trunks  of  old  trees  of  that 
species.  It  has  a  dextro-rotatory  power  =  34-4°.  A  second,  having  a 
dextro-rotatory  power  of  44-9°,  is  produced,  together  with  camphic  acid, 
by  the  action  of  alcoholic  potash  on  common  camphor,  to  which  indeed 
camphol  bears  the  same  relation  that  ethyl  alcohol  bears  to  aldehyde : 

2C10H160     +     OH2    ==    C10H180     +     C}0H1602 
Camphor.  Camphol.        Camphic  acid. 

A  third  variety,  possessing  a  dextro-rotatory  power  of  4-5°,  is  obtained 
by  distilling  amber  with  potash ;  and  a  fourth,  called  lievo-camphol,  which 
has  a  laevo-rotatory  power  of  33-4°  (equal  and  opposite  to  that  of  borneol), 
is  found  in  the  alcohol  produced  in  the  fermentation  of  sugar  from  mad- 
der-root. 

Dextro-rotatory  camphol,  both  natural  and  artificial,  forms  small  trans- 
parent, colorless  crystal.s,  apparently  having  the  form  of  regular  hexago- 
nal prisms,  insoluble  in  water,  very  soluble  in  alcohol  and  ether.  It  melts 
at  198°  C.  (388°  F.),  and  boils  at  212°  C.  (414°  F.),  distilling  without  altera- 
tion. Laevo-rotatory  camphol  forms  crystalline  laminae,  or  a  white  powder, 
sparingly  soluble  in  water,  easily  in  acetic  acid,  alcohol,  and  ether.  Both 
varieties  smell  like  pepper  and  common  camphor. 

Camphol,  distilled  with  phosphoric  oxide,  gives  up  water,  and  yields  a 
hydrocarbon,  C10H16,  isomeric  with  turpentine  oil.  When  boiled  with  nitric 
acid,  it  gives  off  two  atoms  of  hydrogen,  and  is  reduced  to  the  correspond- 
ing aldehyde,  viz.,  common  or  laurel  camphor,  C10H160,  which  is  dextro-  or 
laevo-rotatory,  according  to  the  variety  of  camphol  used.  With  other  acids, 
camphol  behaves  like  alcohols  in  general,  forming  ethers:  thus,  when 
heated  in  a  sealed  tube  with  strong  hydrochloric  acid,  it  forms  camphor 
chloride,  C10H17C1,  a  crystalline  laevo-rotatory  substance  isomeric  with  hy- 
drochloride  of  turpentine  oil,  C10H16.HC1  (p.  489).  With  benzoic  acid 
camphol  forms  camphyl  benzoate,  C7II502.  C10HW. 


AROMATIC   ALCOHOLS   AND   ETHERS.  547 


<J,  Monatomic  Alcohols,  Cn  H^^O,  or  Cn  H^jOH. 

These  alcohols  correspond  to  the  aromatic  hydrocarbons,  and  are  there- 
fore called  aromatic  alcohols.  The  lowest  member  of  the  series  corresponds 
to  benzene,  and  therefore  contains  six  atoms  of  carbon.  Now,  the  consti- 
tutional formula  of  benzene  (p.  493)  shows  that  in  this  hydrocarbon  every 
carbon-atom  is  directly  combined  with  two  others.  Hence,  when  one  of 
the  hydrogen-atoms  in  benzene  is  replaced  by  hydroxyl,  the  resulting  alco- 
hol must  be  a  secondary  alcohol.  The  relation  of  this  alcohol,  called  phenol, 
to  benzene,  is  shown  by  the  following  formulae  : 

H— C— C— H  H— C— C— OH 

H-C    C-H  H-C    C-H 

H— C=C— H  H— C=C— H 

Benzene.  Phenol. 

It  appears,  then,  that  there  can  be  no  primary  six-carbon  alcohol  of  the 
aromatic  series.  But  with  the  higher  alcohols  of  the  series  the  case  is  dif- 
ferent. For  in  any  homologue  of  benzene,  —  formed,  as  already  observed, 
by  replacing  one  or  more  of  the  hydrogen-atoms  in  that  body  with  an  alco- 
hol radical  of  the  series  CttH2n  -^v  viz.,  methyl  and  its  homologues, — the 
substitution  of  hydroxyl  for  hydrogen  may  take  place  either  in  the  benzene 
molecule  itself,  or  in  the  methyl,  ethyl,  &c.,  attached  to  it ;  in  the  latter 
case  the  carbon-atom  united  with  hydroxyl  will  be  directly  combined  with 
only  one  other  atom  of  carbon,  so  that  a  primary  alcohol  will  result ;  but 
in  the  former  case,  the  carbon  united  with  hydroxyl  will  still  be  combined 
also  with  two  other  atoms  of  carbon,  so  that  the  resulting  alcohol  will  be 
secondary ;  thus, 

H— C— C— H  H— C— C— H  H— C— C— OH 

II     II  II     H  II      II 

H-C    C— H  H— C    C— H  H— C    C— H 

H— C=C— CH3  H— C=C— CH2OH         H— C=C— CH3 

Methyl  benzene,  or  Primary  alcohol.         Secondary  alcohol. 

Toluene. 

In  the  higher  terms  of  the  series,  a  greater  number  of  isomeric  alcohols 
may  exist,  inasmuch  as  each  of  the  isomeric  hydrocarbons  containing  a 
given  number  of  carbon-atoms  (p.  494)  may  furnish  a  primary  and  a 
secondary  monatomic  alcohol.  Thus  the  formulae  C8H10  include  sethyl  ben- 
zene, C6H5(C2H5),  and  dimethyl  benzene,  C6H4(CH3)2,  to  each  of  which  there 
corresponds  a  primary  and  a  secondary  alcohol : 

H— C— C— H  H— C— C— H  H— C— C— OH 

H  J  LH  H  J  LH  H  J   LH 

H— C=G— CH2CH3      H— Ct=C— CH2CH2OH     H-C=C— CH2CH3 
Ethyl-benzene.  Primary  alcohol.  Secondary  alcohol. 

H— C— C— H  H— C— C— H  H— C— C— OH 

H— G    C— CH3  H— C    C— CH3  H— C    C— CH3 

H— C=C— CH3  H— C=C— CH2OH  H— C=C— CH3. 

Dimethyl-benzene.  Primary  alcohol.  Secondary  alcohol. 


548  AROMATIC   ALCOHOLS    AND   ETHERS. 

The  constitution  of  the  primary  aromatic  alcohols  is  similar  to  that  of 
the  alcohols  of  the  methyl  series,  in  this  respect,  that  the  carbon-atom 
combined  with  hydroxyl  is  also  directly  associated  with  two  atoms  of  hy- 
drogen; and  accordingly  these  alcohols,  when  subjected  to  the  action  of 
oxidizing  agents,  easily  give  up  these  two  atoms  of  hydrogen  in  exchange 
for  an  atom  of  oxygen,  and  are  thereby  converted  into  acids,  the  group, 
CH2OH,  being  converted  into  COOH,  just  as  in  the  conversion  of  common 
alcohol,  CH3CH2OH,  into  acetic  acid,  CH3COOH.  But  in  the  secondary 
aromatic  alcohols,  or  phenols,  the  carbon-atom  united  with  hydroxyl,  has 
its  three  other  units  of  equivalence  satisfied  by  combination  with  two  other 
carbon-atoms,  and  there  is  no  hydrogen  in  its  immediate  neighborhood 
to  be  exchanged  for  oxygen:  hence,  these  alcohols  are  not  converted  by 
oxidation  into  acids  containing  the  same  number  of  carbon-atoms. 

The  actually  known  alcohols  of  the  aromatic  series  are  the  following: 

Primary.  Secondary, 

Phenol,  C6H5OH 

Benzyl  alcohol,         C6H5.CH2OH  Cresol,  C6H4(CHo)OH 

fPhlorol,  C6H4(C2H5)OH 
Xylyl  alcohol,           C7H7 .  CILOH          \  Dimethyl 

[      phenol,  C6H3(CH3)2OH 

Cymyl  alcohol,        C9HU.CH2OH  Thymol,  C6H3(CaH5)2OH? 

Sycoceryl  alcohol,  C17H27.  CH2OH 

The  secondary  aromatic  alcohols  are  often  designated  by  the  generic 
name  of  phenols;  thus  cresol  is  methyl-phenol,  phlorol  is  ethyl-phenol,  &c. 
There  are  also  diatomic  and  triatomic  phenols,  which  will  be  noticed  here- 
after. 


PRIMARY  AROMATIC  ALCOHOLS. 

Benzyl  Alcohol,  C7H80==C7H7(OH)=C6H5.CH2OH;  also  called  Benzole 
alcohol.*  —  This  alcohol  is  produced:  1.  By  the  action  of  alcoholic  potash 
on  benzoic  aldehyde  (bitter-almond  oil) : 

2C7H60        -f        KOH        =        C7H80        -f        C7H502K 

Benzoic  Benzyl  Potassium 

aldehyde.  alcohol.  benzoate. 

2.  From  toluene,  C7H8,  by  converting  that  compound  into  benzyl  chloride, 
C7H7C1,  by  the  action  of  chlorine  at  high  temperatures  (p.  496),  and  dis- 
tilling this  chloride  with  potash : 

C7H7C1        +        KOH        =        KC1        +        C7H7OH. 

3.  Together  with  other  products,  by  the  action  of  nascent  hydrogen  on 
benzoic  or  hippuric  acid  (see  those  acids). 

Benzyl  alcohol  is  a  colorless,  strongly  refracting,  oily  liquid,  having  a 
specific  gravity  of  1-051  at  14°  C.  (57°  F.),  and  boiling  at  206-5°  C.  (404° 
F.).  It  is  insoluble  in  water,  but  soluble  in  all  proportions  in  common  al- 
cohol, ether,  acetic  acid,  and  carbon  bisulphide.  By  oxygen  in  presence 
of  platinum  black,  or  by  nitric  acid,  it  is  converted  into  benzoic  aldehyde; 
by  aqueous  chromic  acid,  into  benzoic  acid: 

C6H5.CH2OH        +        0        =        OH2        -f        C6H5.COH 
Benzyl  alcohol.  Benzoic  aldehyde. 

C6H5.CH2OH        +        02       =        OH2        -f       C6H6.CO(OII) 
Benzyl  alcohol.  Benzoic  acid. 

*  Cannizea.ro,  Ann.  Ch.  Pharm.  Ixxxviii.  129;  xc.  252;  xcii.  113. 


PRIMARY   AROMATIC   ALCOHOLS.  549 

Heated  with  boric  oxide,  it  is  converted  into  benzyl  oxide,  C7H.OC7H7,  or 
(C7II7)20: 

2C7H7(OH)  —  OH2  =  (C7H7)20. 

Strong  hydrochloric  acid  converts  it  into  benzyl  chloride,  C,H7C1  (p.  49G). 
Distilled  with  acetic  acid  and  strong  sulphuric  acid,  it  is  converted  into 
benzyl  acetate,  C7H7(OC2H30),  a  liquid  having  an  odor  of  pears,  and  boiling 
at210°C.  (410  F.) 

Xylyl  Alcohol,  C8H100  =  C8H9(OH)^C7H7.  CH2OH,  or  C6H4(CH)3.  CH2OH, 
also  called  Toluylic  alcohol.  —  The  formation  of  this  compound  is  exactly 
analogous  to  that  of  the  preceding,  viz. :  1.  Together  with  toluic  acid, 
(C8H802),  by  the  action  of  alcoholic  potash  on  toluic  aldehyde,  (C8H80). 
2.  By  distilling  xylyl  chloride  (p.  498)  with  potash.  It  is  a  white  crystal- 
line body,  which  melts  between  58-5°  and  59-5°  C.  (138°  and  140°  F.),  and 
boils  at  217°  C.  (422°  F.).  Nitric  acid  converts  it  into  toluic  aldehyde. 

Xylyl  chloride,  C9H9C1,  is  obtained,  as  already  observed,  by  the  action  of 
chlorine  on  xylene-vapor  at  high  temperatures ;  and  this  chloride,  treated 
with  sulph-hydrate  and  potassium  sulphide,  yields  xylyl  sulph-hydrate, 
C8H9(SH),  and  xylyl  sulphide  (C8H9)2S. 

Cymyl  Alcohol,  C10HuO=C10H13(OH)=C9Hn.CH2OH,  also  called  Cumylic 
Alcohol. — This  alcohol,  discovered  by  Kraut,*  is  produced  by  the  action, 
of  alcoholic  potash  on  cuminic  aldehyde : 

2C]0H120     +     KOH    =    C10Hn02K    +     C10H140 
Cuminic  Potassium  Cymyl 

aldehyde.  cuminate.  alcohol. 

It  is  a  colorless  liquid,  boiling  at  243°  C.  (470°  F.),  insoluble  in  water, 
soluble  in  all  proportions  in  common  alcohol  and  ether.  Nitric  acid  con- 
verts it  into  cuminic  acid.  Boiled  with  alcoholic  potash,  it  is  converted  into 
potassium  cuminate  and  cymene : 

3C]0H140     +     KOH    =     C10HH02K    +    2C10H14    -f    20H2 
Cymyl  Potassium  Cymene. 

alcohol.  cuminate. 

Hydrochloric  acid  gas  converts  it  into  cymyl  chloride,  C10H13C1. 

Sycoceryl  Alcohol,  C18H300=C18H29(OH)=CH17H27.CH2OH.— This  com- 
pound, discovered  by  De  la  Rue  and  Miiller,f  is  produced  by  the  action  of 
alcoholic  soda  on  sycoceryl  acetate  (a  crystalline  substance  extracted  from 
the  resin  of  Ficus  rubiginosa],  and  purified  by  precipitation  with  water  or 
by  crystallization  from  common  alcohol.  It  forms  very  thin  crystals  re- 
sembling caffeine,  and  melting  at  90°  to  a  liquid  heavier  than  water.  It 
is  slowly  attacked  by  dilute  nitric  acid,  yielding  a  crystalline  mass  ap- 
parently consisting  of  a  mixture  of  sycoceric  acid,  C^H^O^  and  nitrbsycoceric 
acid,  C18H27(N02)02.  Boiled  with  dilute  aqueous  chromic  acid,  it  yields  thin 
prisms,  probably  of  Sycoceric  aldehyde,  C^H^O.  With  acetyl  chloride,  it 
forms  crystalline  sycoceryl  acetate: 

C18H29OH     -f     C2H3OC1    ==    HC1    +     C18H29OC2H30 
Sycoceryl  Acetyl  Sycoceryl 

alcohol.  chloride.  acetate. 

With  benzoic  acid  it  yields,  in  like  manner,  sycoceryl  benzoate,  C18H29OC7H60, 
which  crystallizes  in  prisms  from  solution  in  benzene  or  chloroform. 

The  resin  of  Ficus  rubiyinoxd,  an  Australian  plant,  is  resolved  by  treat- 
ment with  alcohol,  into  about  73  per  cent,  of  sycoretin,  soluble  in  cold  alcohol, 

*  Ann.  Ch.  Pharm.  xcii.  66.  t  Phil-  Trans.  I860,  p.  43. 


550  AROMATIC   ALCOHOLS   AND   ETHERS. 

14  per  cent,  of  sycoceryl  acetate,  soluble  in  hot  alcohol,  and  13  percent,  of 
residue,  consisting  of  caoutchouc,  sand,  and  fragments  of  bark.  Sycoretin 
is  an  amorphous  white  neutral  resin,  very  brittle  and  highly  electric ;  it 
melts  in  boiling  water  to  a  thick  liquid  which  floats  on  the  surface.  It 
dissolves  easily  in  alcohol,  ether,  chloroform,  and  oil  of  turpentine. 


SECONDARY  AROMATIC  ALCOHOLS;  PHENOLS. 

Phenol,  C6H6O^C6H5OH.— Phenyl  alcohol,  Phenic  acid,  Carbolic  acid,  Coal-tar 
creosote. — This  compound  is  produced:  1.  By  the  action  of  nitrous  acid  on 
aniline  (amidobenzene) : 

C6H5(NH2)     -f     NO(OH)     =    C6H5(OH)     +     OH2    +     N2 
Aniline.  Nitrous  Phenol, 

acid. 

2.  By  the  dry  distillation  of  salicylic  acid: 

C7H603        =        C02        +        C6H60 
Salicylic  Carbon  Phenol, 

acid.  dioxide. 

It  may  be  conveniently  prepared  by  heating  crystallized  salicylic  acid 
strongly  and  quickly  in  a  glass  retort,  either  alone  or  mixed  with  pounded 
glass  or  quicklime.  Phenol  then  passes  over  into  the  receiver,  and  crys- 
tallizes almost  to  the  last  drop. 

3.  Phenol  is  produced  in  the  dry  distillation  of  coal,  and  forms  the  chief 
constituent  of  the  acid  portion  of  coal-tar  oil;  this  is  the  source  from  which 
it  is  most  frequently  obtained.     Crude  coal-tar  oil  is  agitated  with  a  mix- 
ture of  slaked  lime  and  water,  the  whole  being  left  for  a  considerable  time; 
the  aqueous  liquid  is  then  separated  from  the  undissolved  oil,  decomposed 
by  hydrochloric  acid,  and  the  oily  product  thus  obtained  is  purified  by 
cautious  distillation,  the  first  third  only  being  collected.     Or  the  coal-tar 
oil  is  subjected  to  distillation  in  a  retort  furnished  with  a  thermometer,  and 
the  portion  which  passes  over  between  the  temperatures  of  150°  and  200°  C. 
(302° and  390°  F.)  is  collected  apart.    This  product  is  then  mixed  with  a  hot, 
strong  solution  of  caustic  potash,  and  left  to  stand,  whereby  a  whitish, 
somewhat  crystalline,  pasty  mass  is  obtained,  which  by  the  action  of  water 
is  resolved  into  a  light  oily  liquid  and  a  dense  alkaline  solution.     The  latter 
is  withdrawn  by  a  siphon,  decomposed  by  hydrochloric  acid,  and  the  sepa- 
rated  oil  purified  by   contact   with   calcium   chloride,    and  redistillation. 
Lastly,  it  is  exposed  to  a  low  temperature,   and  the  crystals  formed  are 
drained  from  the  mother-liquid  and  carefully  preserved  from  the  air. 

Pure  phenol  forms  long,  colorless,  prismatic  needles,  which  melt  at  35°  C. 
(95°  F.)  to  an  oily  liquid,  boiling  at  180°  C.  (356°  P.),  and  greatly  resem- 
bling creosote*  in  many  particulars,  having  a  very  penetrating  odor  and 
burning  taste,  and  attacking  the  skin  of  the  lips.  Its  sp.  gr.  is  1-065.  It 
is  slightly  soluble  in  water,  freely  in  alcohol  and  ether,  and  has  no  acid 
reaction  to  test-paper.  The  crystals  absorb  moisture  with  avidity,  and 
liquefy. f  It  coagulates  albumen,  and  is  a  powerful  antiseptic,  preserving 
meat  and  other  animal  substances  from  decomposition,  and  even  removing 
the  fetid  odor  from  them  after  they  have  begun  to  putrefy.  It  has  also 

*  A  considerable  portion  of  the  creosote  of  commerce  consists  of  phenol  or  carbolic  acid, 
more  or  less  pure. 

f  Phenol  prepared  from  salicylic  acid  is  much  less  deliquescent  than  that  obtained  from  coal- 
tar. 


SECONDARY   AKOMATIC   ALCOHOLS.  551 

been  successfully  used  by  Mr.  Crookes  for  destroying  the  infection  of  cattle 
plague.  Sulphur  and  iodine  dissolve  in  it;  nitric  acid,  chlorine,  and  bro- 
mine attack  it  with  energy,  forming  substitution-products,  all  of  which  are 
of  acid  character:  thus  with  chlorine  it  forms  the  two  compounds,  C6H4C12O 
and  CgtLClgO";  and  with  nitric  acid  the  three  products,  C6II6i£sO,)0, 
C6H4(N02)20,  and  C6H3(N02)30. 

With  sulphuric  acid,  phenol  forms  sulphophenic  acid,  C6H6S04,  or  C6H5 
OS03H,  which  assumes  a  syrupy  state  in  a  dry  vacuum.  This  acid  is  to  a 
certain  extent  analogous  in  composition  to  ethylsulphuric  acid,  and  forms 
a  soluble  barium  salt,  which  crystallizes  from  alcohol  in  minute  needles. 

Phenol  dissolves  in  alkalies,  forming  salts  called  phenates,  which,  how- 
ever, are  difficult  to  obtain  in  definite  form.  Potassium  phenate,  C6H5KO, 
obtained  by  heating  phenol  with  potassium,  or  with  solid  potassium  hy- 
drate, crystallizes  in  tine  white  needles.  On  heating  this  potassium-com- 
pound with  iodide  of  methyl,  ethyl,  or  amyl,  double  ethers  are  produced, 
viz.,  methyl-phenate,  or  anisol,  C6H5OCH3;  ethyl-phenate,  or  phenetol, 
C6H5OC2H5,  and  amyl-phenate,  or  phenamylol,  C6H5OC5Hn.  These  bodies 
resemble  the  mixed  ethers  of  the  ordinary  alcohols  (p.  501J)  in  composition 
and  mode  of  formation,  but  differ  greatly  from  them  in  their  behavior  with 
sulphuric  and  nitric  acids,  with  which  in  fact  they  behave  just  like  phenol 
itself,  forming  substitution-products  possessing  acid  properties. 

Methyl phenat e,  or  Anisol,  C?H80  —  C6H5OCH3,  is  also  produced,  with  evo- 
lution of  carbon  dioxide,  by  the  dry  distillation  of  methyl  salicylate,  C7H5 
03 .  OH,,  just  as  phenol  is  obtained  from  salicylic  acid  or  hydrogen  salicy- 
late, C7H5O.H: 

C,HB0S.CH,        =        C02        -f-        C6H5O.CH3 

Methyl  Methyl 

salicylate.  phenate. 

In  the  same  manner  also  may  ethyl  phenate  and  amyl  phenate  be  obtained 
from  the  corresponding  ethers  of  salicylic  acid. 

Anisol  is  a  colorless,  very  mobile  liquid,  having  a  pleasant  aromatic  odor, 
a  specific  gravity  of  0-991  at  15°  C.  (59°  F.),  and  boiling  without  decompo- 
sition at  152°  C.  (306°  F.).  It  dissolves  completely  in  strong  sulphuric 
acid,  forming  sulphanisolic  acid,  C7H8S04.  Fuming  nitric  acid  acts  strongly 
on  anisol,  forming  three  substitution-products,  each  of  which  when  treated 
with  a  reducing  agent,  such  as  ammonium  sulphide,  yields  a  corresponding 
basic  amido-compound :  thus, 

C7H7(N02)0  C7H7(NH2)0 

Nitranisol.  Nitranisidine. 

C7H6(N02)20  C7H6(NH2)20 

Dmitranisol.  Dinitranisidine. 

C7H,(NO,)80  C7H5(NH2)30 

Trinitranisol.  Trinitranisidine. 

No  such  substitution-products  are  obtained  from  the  mixed  or  compound 
ethers  of  any  primary  alcohol. 

Phenol,  distilled  with  phosphorus  pentachloride,  yields  a  distillate  contain- 
ing a  small  quantity  of  phenyl  chloride  or  chloro-benzene,  C6H5C1  (p.  494), 
and  a  residue  containing  a  triphenyl  phosphate,  P04(C6H5)3,  or  diphenyl 
phosphate,  P04(C6H5)2H ;  but  the  conditions  under  which  one  or  the  other 
of  these  compounds  is  formed  have  not  been  exactly  determined. 

With  benzoic  chloride,  phenol  yields  a  white,  fusible  crystalline  compound 
consisting  of  phenyl  benzoate,  or  benzyl  phenol : 

06H5(OH)     4-     C7H5OC1    =    HC1    +     C6H5OC7H50 
Phenol.  Benzoic  Phenyl 

chloride.  beiizqate, 


552  ALCOHOLS   AND   ETHERS. 

Phenol,  heated  for  a  long  time  with  ammonia  in  sealed  tubes,  is  converted 
into  aniline,  C6H7N. 

Chlorophenols. — Monochlorophenol  has  not  been  obtamed. 

Dichlorophenol,  or  Chlorophenesic  acid,  C6H4C120,  is  produced  by  the  com- 
paratively feeble  action  of  chlorine  on  phenol,  but  is  best  obtained  by  the 
dry  distillation  of  dichlorosalicylic  acid.  It  is  a  volatile  oil,  insoluble  in 
water,  easily  soluble  in  alcohol  or  ether. 

Trichlorophenol,  or  Chlorophenisic  acid,  C6H3C130,  is  the  principal  product 
of  the  action  of  chlorine  on  phenol.  It  may  be  conveniently  prepared  from 
those  portions  of  crude  coal-oil  which  boil  between  182°  and  204°  C.  (860° 
and  400°  F.).  The  oil  is  saturated  with  chlorine,  and  distilled  in  the  open 
air,  the  first  and  last  portions  being  rejected  ;  and  the  product  is  again 
treated  with  chlorine  until  the  whole  solidifies.  The  crystals  are  drained 
and  dissolved  in  hot  dilute  solution  of  ammonia :  on  cooling,  the  sparingly 
soluble  ammonium  chlorophenisate  crystallizes  out.  This  is  dissolved  in 
pure  water,  decomposed  by  hydrochloric  acid,  washed,  and  lastly  distilled. 

Chlorophenisic  acid  forms  exceedingly  fine,  colorless,  silky  needles, 
which  melt  when  gently  heated :  it  has  a  very  penetrating,  persistent,  and 
characteristic  odor,  is  very  sparingly  soluble  in  water,  but  dissolves  freely 
in  alcohol,  ether,  and  hot  concentrated  sulphuric  acid.  It  slowly  sublimes 
at  common  temperatures,  and  distils  with  ebullition  when  strongly  heated. 
It  forms  well-defined  salts,  the  general  formula  of  which  is  C6H2MC130. 
When  treated  in  alcoholic  solution  with  excess  of  chlorine,  it  is  converted 
into  pentachlorophenol,  or  chlorophenusic  acid,  C6HC150,  which  is  also 
crystalline. 

Bromophenols. — Three  bromophenols  have  been  obtained,  viz.,  C6H5BrO 
and  C6H4Br20,  by  distillation  of  monobromosalicylic  and  dibromosalicylic 
acids ;  and  C6H3Br30  by  the  action  of  bromine  in  excess  on  phenol.  The 
first  is  liquid ;  the  other  two  are  crystalline. 

lodophenols,  C6H5IO,  C6H4I20,  and  C6H3I30,  are  produced  by  the  action 
of  iodine-chloride  on  phenol. 

Nitrophenols. — Three  of  these  compounds  are  known,  all  of  acid  character. 

Mononitrophenol,  or  Nitrophenasic  acid,  C6H5(N02)0,  is  obtained  by  distilling 
phenol  with  very  dilute  nitric  acid,  in  beautiful  yellow  needles,  soluble  in 
ammonia  and  potash,  and  yielding  a  beautiful  red  silver  salt,  C6H4Ag(N02)0. 

Dinitrophenol,  or  Nitrophenesic  add,  C6H4(N02)20,  may  be  prepared  directly 
from  the  oil  which  is  employed  in  the  preparation  of  mononitrophenol. 
The  oil  is  carefully  mixed  in  a  large  open  vessel  with  rather  more  than  its 
own  weight  of  ordinary  nitric  acid.  The  action  is  very  violent.  The 
brownish-red  substance  produced  is  slightly  washed  with  water,  then  boiled 
with  dilute  ammonia,  and  filtered  hot.  A  brown  mass  remains  on  the  filter, 
which  is  preserved  to  prepare  trinitrophenol,  and  the  solution  deposits  on 
cooling  a  very  impure  ammoniacal  salt  of  nitrophenesic  acid,  which  requires 
several  successive  crystallizations,  after  which  it  is  decomposed  by  nitric 
acid,  and  the  product  is  crystallized  from  alcohol. 

Nitrophenesic  acid  forms  yellow  prismatic  crystals,  very  sparingly  soluble 
even  in  boiling  water,  but  freely  soluble  in  alcohol.  It  has  no  odor.  Its 
taste,  at  first  feeble,  becomes  after  a  short  time  very  bitter.  It  melts  at  104°, 
and  crystallizes  on  cooling.  In  very  small  quantity  it  may  be  distilled  with- 
out decomposition,  but  when  briskly  heated  it  often  detonates,  but  not  vio- 
lently. The  salts  of  this  acid  are  yellow  or  orange,  and  very  beautiful ; 
they  are  mostly  soluble  in  water,  and  detonate  feebly  when  heated. 

Trinitrophenol,  or  Nitrophcnisic  acid —  generally  called  Picric  acid,  and  some- 
times Carbazotic  acid—  C6H3N307  =  C6H3(N02).,0. — This  acid  may  be  eco- 
nomically prepared  from  impure  nitrophenesic  acid,  or  from  the  brown 
mass  insoluble  in  dilute  ammonia  already  referred  to.  It  is  purified  by  a 
process  similar  to  that  employed  in  the  case  of  the  preceding  compound. 


SECONDARY   AROMATIC   ALCOHOLS.  553 

It  is  also  one  of  the  ultimate  products  of  the  action  of  nitric  acid  upon 
indigo  and  numerous  other  substances,  as  silk,  wool,  several  resins,  espe- 
cially that  of  Xanthorrcea  hastilis  (yellow  gum  of  Botany  Bay),  salicin  and 
some  of  its  derivatives,  coumarin,  &c.  It  may  be  prepared  from  indigo  by 
adding  that  substance  in  coarse  powder,  and  by  small  proportions,  to  10  or 
12  times  its  weight  of  boiling  nitric  acid  of  sp.  gr.  1-43.  When  the  last  of 
the  indigo  has  been  added,  and  the  action,  at  first  extremely  violent,  has 
become  moderate,  an  additional  quantity  of  nitric  acid  may  be  poured  upon 
the  mixture,  and  the  boiling  kept  up  until  the  evolution  of  red  fumes  nearly 
ceases.  When  cold,  the  impure  picric  acid  obtained  may  be  removed,  con- 
verted into  potassium-salt,  several  times  recrystallized,  and  lastly,  decom- 
posed by  nitric  acid.  In  the  pure  state  it  forms  beautiful  pale-yellow  scaly 
crystals,  but  slightly  soluble  in  cold  water  and  of  insupportably  bitter  taste. 
Picric  acid  is  now  extensively  used  in  dyeing  yellow.  It  forms  a  series  of 
crystallizable  salts  of  a  yellow  or  orange  color.  The  potassium  salt,  C6H2K 
(N02)30,  forms  brilliant  needles,  and  is  so  little  soluble  in  cold  water  that 
a  solution  of  picric  acid  is  occasionally  used  as  a  precipitant  for  potassium. 
The  alkaline  salts  of  this  acid  explode  by  heat  with  extraordinary  violence. 
When  a  solution  of  picric  acid  is  distilled  with  calcium  hypochlorite,  or  a 
mixture  of  potassium  chlorate  and  hydrochloric  acid,  an  oily  liquid  of  a 
penetrating  odor  is  obtained,  having  a  sp.  gr.  of  1-665,  and  boiling  between 
114°  and  115°  C.  (237°  and  239°  F.).  This  substance,  chloropicrin,  has  the 
composition  CN02C13,  which  is  that  of  chloroform  (CHC13),  having  the  hy- 
drogen replaced  by  nitryl.  Bromopicrin,  CN02Br3,  is  obtained  in  like  man- 
ner by  treating  picric  acid  with  calcium  hypobromite. 

Cresol,  C7H80  =  C6H4(CH3)  .  OH.  —This  compound  exists,  together  with 
phenol,  in  the  so-called  coal-tar  creosote,  and  is  separated  by  fractional 
distillation.  It  is  also  contained,  together  with  phenol  and  other  com- 
pounds, in  the  tar  of  pine-wood,  and  is  obtained  therefrom  by  treating  the 
oil  which  passes  over  in  distillation  between  150°  and  220°  C.  (302°  and>408° 
F.),  with  weak  soda-lye  to  separate  hydrocarbons,  supersaturating  the  alka- 
line liquid  with  sulphuric  acid,  and  repeating  the  treatment  with  soda-lye 
and  sulphuric  acid,  till  the  oil  becomes  perfectly  soluble  in  the  alkaline 
liquid.  The  oil  thus  obtained  is  a  mixture  of  phenol  and  cresol,  which  are 
separated  by  fractional  distillation. 

Cresol  is  a  colorless,  strongly  refracting  liquid,  which  boils  at  203°  C. 
(397°  F.).  It  is  slightly  soluble  in  water,  and  mixes  in  all  proportions  with 
alcohol  and  ether.  It  reacts  with  potassium,  phosphorus  pentachloride, 
sulphuric  acid,  and  nitric  acid,  in  the  same  manner  as  phenol,  forming 
analogously  constituted  compounds.  Trinitrocresol,  or  Trinitrocresylic  acid, 
C7H-(N02)30,  crystallizes  in  yellow  needles  like  picric  acid:  its  potassium- 
salt,  C7H4K(N02)30,  in  orange-red  needles,  moderately  soluble  in  water. 

Crysol  is  isomeric  with  benzyl  alcohol  and  with  anisol :  the  difference  of 
constitution  of  these  three  compounds  is  exhibited  in  the  following  dia- 
grams : 

H— C— C— H  H— C— C— OH  H-C— C— OCHS 

H  J  U  nJ,  U  HJj  LH 

H— C=rC— CH2OH          H— C=C—  CH3  H— C=C— H 

Benzyl  alcohol.  Cresol.  Anisol. 

Eight-carbon  Xylylic  Phenols,  C8TI100.  —  This  formula  may  include  two 
secondary  alcohols,  isomeric  with  xylyl  alcohol,  viz., 

Dimethyl-phenol C6H3(CH3)2OH 

Ethyl-phenol C6H4(C2H5)OH. 

47 


554  ALCOHOLS   AND   ETHERS. 

A  xylylic  phenol  is  mentioned  by  Hugo  Muller*  as  occurring  in  coal-tar. 
This  is  probably  dimethyl  phenol,  inasmuch  as  products  obtained  by  de- 
structive distillation  have  hitherto  been  found  to  contain  only  methyl  deriva- 
tives of  benzene.  The  portion  of  aloi'sol  (a  product  obtained  by  distilling 
aloes  with  lime),  which  is  soluble  in  potash,  has,  according  to  Rembold,f 
the  composition  of  a  xylylic  phenol,  and  is,  perhaps,  identical  with  that 
occurring  in  coal-tar. 

Phlorol,  an  oily  liquid  obtained  by  the  dry  distillation  of  the  barium  salt 
of  phloretic  acid,  C9H1003,  has  also  the  composition  C8H100,  and  probably 
consists  of  ethyl-phenol.  Its  formation  is  represented  by  the  equation, 

C9H1003        =        C02        +        C8H100. 

Phlorol  is  a  colorless,  strongly  refracting  oil,  having  a  specific  gravity 
of  1-0374  at  12°  C.  (54°  P.),  and  boiling  between  190°  and  200°.  It  dis- 
solves in  strong  sulphuric  acid,  forming  a  sulpho-acid  which  yields  a  soluble 
barium  salt.  With  chlorine  it  forms  a  substitution-product.  It  reacts  vio- 
lently with  strong  nitric  acid,  forming  the  compound,  C8H7(N02)30. 

Ten-carbon  Phenols. — The  formula,  C10H140,  may  evidently  include  a 
considerable  number  of  phenols  isomeric  with  cymyl  alcohol  (p.  549); 
only  one  of  these,  however,  is  known,  viz.,  thymol,  and  even  of  this  the 
exact  constitution  has  not  been  ascertained. 

Thymol,  C10HU0,  is  a  crystalline  body,  occurring  (together  with  thymene, 
C10H16,  and  cymene,  C,0H14)  in  the  volatile  oil  of  thyme  (Thymus  vulgaris), 
It  sometimes  crystallizes  out  spontaneously,  and  may  in  all  cases  be  sepa- 
rated by  agitating  the  oil  with  soda-solution,  and  supersaturating  the  alka- 
line liquid  with  hydrochloric  acid.  It  is  also  obtained  from  the  volatile  oil 
of  horse-mint  (Monarda punctata),  and  from  that  of  an  East  Indian  umbelli- 
ferous plant  called  Ptychotis  Ajowan. 

Thymol  crystallizes  in  transparent  rhomboi'dal  plates,  melting  at  44°.  It 
has^a  mild  odor,  peppery  taste,  and  boils  without  decomposition  at  220°  C. 
(428°  F.).  It  is  distinguished  from  cymyl  alcohol  by  yielding  with  oxidiz- 
ing agents,  not  cuminic  acid,  but  thymoi'l,  C,2H,602.  With  sodium  it  forms 
the  compound,  C,0HJ3NaO,  which  absorbs  carbon  dioxide,  forming  the  so- 
dium salt  of  thyinotic  acid,  C,0H,403,  or  C,0H,4O.C02.  Strong  sulphuric  acid 
converts  thymol  into  thymylsulphuric  acid,  C,0H14S04.  With  bromine  in  sun- 
shine it  yields  pentabromothymol,  C10H9Br60;  and  with  chlorine,  Ci0H,,Cl30, 
or  C,0H9C150,  according  as  the  reaction  takes  place  in  the  shade  or  in  sun- 
shine ;  both  these,  as  well  as  the  bromine-compound,  are  crystalline. 

There  are  two  nitro-thymols,  C,0H,2(NO2)20  and  C10Hn(N02)30,  obtained 
by  the  action  of  nitric  acid  on  thymyl-sulphuric  acid.  Both  form  potassium- 
salts,  which  crystallize  in  yellow  or  orange-yellow  needles. 


e.  Monatomic  Alcohols,  CnH2n_80,  or  CnH2n_7(OH). 
Two  only  of  these  bodies  are  known,  viz.,  cinnyl  alcohol  and  cholesterin. 

Cinnyl  Alcohol,  Styryl  Alcohol,  or  Styrone,  C9H100,  or  C9H9OH,  is  obtained 
by  heating  styracin  or  cinnyl  ci-nnamate,  C9H9(OC9H70),  (a  compound  con- 
tained in  liquid  storax  and  in  balsam  of  Peru,)  with  caustic  alkalies.  It 
crystallizes  in  soft  silky  needles,  having  a  sweet  taste  and  an  odor  of  hya- 
cinths, melting  at  33°,  and  volatilizing,  without  decomposition,  at  a  higher 

*  Zeitschrift  fur  Chemie,  1865,  p.  271.  •          f  Ann,  Ch.  Pharm.  cxxxviii.  186. 


DIATOMIC   ALCOHOLS   AND   ETHERS.  555 

temperature.  It  is  moderately  soluble  in  water,  freely  in  alcohol  and  ether. 
By  oxidizing  agents  it  is  converted  into  cinnamic  aldehyde,  C9H80,  and  cin- 
namic  acid,  C9H802,  being  related  to  those  compounds  in  the  same  manner  as 
ethyl  alcohol  to  acetic  aldehyde  and  acetic  acid.  With  fuming  sulphuric 
acid  it  forms  a  sulpho-acid,  C9H,0S03,  the  barium-salt  of  which  is  soluble 
in  water. 


Cholesterin,  C^H^O  —  CggH^OH).  —  This  substance  is  found  in  small 
quantity  in  various  parts  of  the  animal  system,  as  in  the  bile,  the  brain 
and  nerves,  and  the  blood:  it  forms  the  chief  ingredient  of  biliary  calculi, 
from  which  it  is  easily  extracted  by  boiling  the  powdered  gall-stones  in 
strong  alcohol,  and  filtering  the  solution  while  hot;  on  cooling,  the  choles- 
terin  crystallizes  in  brilliant  colorless  plates.  It  is  a  fatty  substance,  in- 
soluble in  water,  tasteless  and  inodorous;  it  is  freely  soluble  in  boiling 
spirit  and  in  ether,  and  crystallizes  from  the  alcoholic  solution  in  beautiful 
white  laminae  having  a  mother-of-pearl  lustre.  It  melts  at  137°  0.  (279°  F.), 
and  sublimes  at  200°  C.  (392°  F.). 

Heated  with  strong  sulphuric  acid,  it  gives  up  water,  and  yields  a  res- 
inous hydrocarbon,  C26H42.  With  nitric  acid  it  yields  cholesteric  acid, 
C8H1006,  together  with  other  products.  With  chlorine  and  bromine  it  forms 
substitution-products.  Heated  to  200°  with  acetic,  butyric,  benzoic,  and 
stearic  acids,  it  forms  compound  ethers,  thus: 


C26H43(OH)     +     C^OCOH)     =    C^OC^O)     -f     OH3 
Cholesterin.  Stearic  Cholesteryl 

acid.  stearate. 


DIATOMIC  ALCOHOLS  AND  ETHERS. 


The  diatomic  alcohols  are  derived  from  saturated  hydrocarbons  by  sub- 
stitution of  two  equivalents  of  hydroxyl  for  two  atoms  of  hydrogen,  and 
may,  therefore,  be  regarded  as  compounds  of  bivalent  alcohol  radicals  with 
two  equivalents  of  hydroxyl.  Thus  ethene  alcohol,  C2H602,  may  be  formu- 
lated in  either  of  the  three  following  ways: 


CH2OH 


(C2H4)"(OH)2; 


the  first  of  which  represents  it  as  a  derivative  of  methane,  CH4;  the  second 

CH3 
as  a  derivative  of  ethane    |      ;  the  third  as  a  compound  of  ethene,  C2H4, 

CH3 

with  hydroxyl ;  or  as  derived   from  a  double  molecule  of  water,  H2(OH)2, 
by  substitution  of  ethene  for  two  atoms  of  hydrogen. 

Two  series  of  these  alcohols  are  known;  the  first  derived  from  the  par- 
affins, the  second  from  the  aromatic  hydrocarbons. 

1.— Diatomic  Alcohols,  CJI^+.jO.,,  or  (CnH2n)^(OH)2. 

The  alcohols  of  this  series  are  designated  by  the  generic  name  of  gly- 
cols.*  They  may  be  regarded  as  compounds  of  olefines  with  two  equivalents 
of  hydroxyl.  The  following  are  known  : 

*  This  term,  formed  from  the  first  syllable  of  flljicerin  and  the  last  of  alcohol,  indicates  that 
tho  compounds  to  which  it  is  applied  nrc  internu'diato  between  the  alcohols,  commonly  so 
called,  and  the  glycerins  or  triatomic  alcohols. 


556  DIATOMIC   ALCOHOLS   AND   ETHERS. 

Name.  Formula.  Boiling  point. 

Ethene  alcohol  .     .     .  C2H602  =  C2H4(OH)2     197-5°  C.  (388°  F.). 
Propene  alcohol     .     .  C3H802  =  CSH6(OH)2     188°-189°  C.  (370°-372°  F  ) 

e    «2  =  C ACOH),    183°-184°  C.  (361°-365°  *)! 


5H1202  =  C5H10(OH)2   177°  C.  (351°  F.). 
Octene  alcohol  .     .    ".  C8H1802=:  C8H16(OH)2   235°-240°C.  (455°-464°F.). 
Methene  alcohol,  CH2(OH)2,  has  not  been  obtained. 
The  glycols  are  formed  by  the  following  processes : 

1.  By  combining  an  olefine  with  bromine  ;  treating  the  resulting  dibro- 
mide  with  an  alcoholic  solution  of  potassium  acetate  or  with  silver  acetate, 
whereby  it  is  converted  into  a  diacetate  of  the  olefine ;  and  decomposing 
this  compound  with  solid  potassium  hydrate,  whereby  potassium  acetate 
and  a  diatomic  alcohol  are  formed,  the  latter  of  which  may  be  distilled  off. 

CH2Br  CH2OC2H30 

-f     2AgOC2H30     =  2AgBr    +      | 
CH2Br  CH2OC2H30 

Ethene  bromide.  Silver  acetate.  Ethene  diacetate. 

CH2OC2H30  CH2OH 

4-   2KOH       =       2KOCJLO    +      I    ' 
CH2OC2H30  CH2OH 

Ethene  di-     Potassium  Potassium  Ethene 

acetate.         hydrate.  acetate.  alcohol. 

2.  By  treating  a  monochlorohydrate  corresponding  to  a  triatomic  alcohol 
(a  glycerin)  with  nascent  hydrogen  (evolved  from  water  by  sodium  amal- 
gam) ;  the  chlorine  is  then  replaced  by  hydrogen,  and  a  diatomic  alcohol 
results;  thus, 

(C,HB)'"(OH)2C1    +     HH    =    HC1    +     (C,He)'(OH)s 
Propenyl  monochloro-  Propene 

hydrate.  alcohol. 

Properties. — The  glycols  are  colorless,  inodorous,  more  or  less  viscid 
liquids,  freely  soluble  in  water  and  alcohol;  ethene  alcohol  is  but  sparingly 
soluble  in  ether ;  the  rest  dissolves  easily  in  that  liquid.  The  boiling  points 
of  ethene,  propene,  quartene,  and  quintene  glycols,  exhibit  the  singular 
anomaly  of  becoming  lower  as  the  molecular  weight  of  the  compound  in- 
creases (see  table,  above) :  octene  glycol,  however,  exhibits  a  higher  boil- 
ing point.  This  anomaly  probably  arises  from  difference  of  constitution  in 
the  successive  terms  of  the  series  at  present  known,  ethene  glycol  being  a 
primary  alcohol,  whereas  the  higher  numbers  may  be  secondary  or  tertiary 
alcohols.  Thus  the  ethene  and  propene  glycols  probably  differ  in  consti- 
tution in  the  manner  shown  by  the  following  formulae  : 

CH2OH  H3C  CH3 

CH2OH  HOCOH 

Ethene  Propene 

alcohol.  alcohol. 

The  reactions  of  the  higher  glycols  are  not  sufficiently  known  to  decide 
this  question  :  it  is  known,  however,  that  propene  alcohol  heated  with  hy- 
driodic  acid,  yields  isopropyl  iodide. 

The  chemical  reactions  of  the  glycols  have  been  studied  chiefly  in  the 
case  of  ethene  alcohol.  They  are,  for  the  most  part,  similar  to  those  of  the 


DIATOMIC    ALCOHOLS    AND    ETHERS. 


557 


monatomic  alcohols  ;  but  inasmuch  as  the  glycols  contain  two  atoms  of  re- 
placeable hydrogen,  or  of  hydroxyl,  the  reactions  generally  take  place  by 
two  stages,  yielding  two  series  of  products. 

1.  Ethene  alcohol  treated  with  nitric  acid  gives  up  2  or  4  atoms  of  hydro- 
gen in  exchange  for  oxygen,  and  is  converted  into  glycollic,  or  oxalic  acid, 
according  as  the  action  takes  plaice  at  ordinary  or  at  higher  temperatures, 


CH2OH 

Glycol. 


CH2OH 

CO(OH) 

Glycollic 

acid. 

CO(OH) 

+     04    =  20H2    +     | 
2OH  CO(OH) 

Ethene  Oxalic  acid, 

alcohol. 


CH2( 


Under  certain  circumstances  the  corresponding  aldehydes  are  also  pro- 

COH 
duced,  as  glyoxal,  \        ,  from  ethene  alcohol,  by  removal  of  four  hydrogen- 

COH 
atoms  without  substitution. 

Ethene  alcohol  is  also  converted  into  oxalic  acid  by  fusion  with  potash: 


C2H602 
Ethene 
alcohol. 


2KOH         = 


4H, 


Potassium 
oxalate. 


Propene  glycol,  C3H602,  is  converted  into  lactic  acid,  C3H603,  by  slow  oxida- 
tion in  contact  with  platinum  black.  When  heated  with  dilute  nitric  acid 
it  yields  glycollic  acid,  losing  carbon  as  well  as  hydrogen;  and  concentrated 
nitric  acid  oxidizes  it  still  further  to  oxalic  acid. 

Quartene  glycol,  C4H1002,  is  converted  by  slow  oxidation  with  nitric  acid 
into  oxy butyric  acid,  C4H803,  and  when  the  action  is  accelerated  by  heat, 
into  oxalic  acid.  Quintene  glycol,  CgH1202,  likewise  yields  oxybutyric  acid  by 
slow  oxidation  with  dilute  nitric  acid. 

2.  Potassium  and  sodium  eliminate  one  or  two  atoms  of  hydrogen  from  the 
•glycols,  and  form  substitution-products.  Ethene  alcohol  is  strongly  attacked 
by  sodium,  yielding  sodium  ethcnate,  C2H6Na02;  and  this  compound,  fused 
with  excess  of  sodium,  is  converted  into  disodium  ethcnate,  C2H4Na202. 
These  compounds,  treated  with  monatomic  alcoholic  iodides,  yield  the 
alcoholic  ethers  of  the  glycols;  thus, 


C2H6I   = 


CH2ONa 

CH2OH 
Sodium  Ethyl 

ethenate.          iodide. 


Nal 


2C2H2I   =   2NaI      -f 


CH2OC2H6 

CH2OH 

Sodium  Ethyl 

iodide.  ethenate. 

CH2OC2H5 


Disodium 
ethenate. 


Ethyl 
iodide. 


Sodium 
iodide. 


CH2OC2H, 
Diethyl 
ethenate. 


3.  Oxygen  acids,  heated  with  glycols  in  closed  vessels,  act  upon  them  in 
the  same  manner  as  upon  the  monatomic  alcohols,  converting  them  into 
ethereal  salts  or  compound  ethers,  mono-acid  or  di-acid,  according  to  the  pro- 

47* 


558 


DIATOMIC   ALCOHOLS   AND   ETHERS. 


HOC2H30 

Acetic 
acid. 


portions  used.  In  the  di-acid  glycol-ethers,  the  two  radicals  by  which  the 
hydrogen  is  replaced  may  belong  either  to  the  same  or  to  different  acids ; 
e.g., 

CH2OH 

CH2OH        '  '  "  '        ' 

Ethene 
glycol. 

CH2OH 

CH2OH 
Ethene 
glycol. 


+    2HOC2H30      = 

Acetic 
acid. 


CH2OC2H30 

Ethene  mono- 

acetate. 

CH2OC2H30 

i 

CH2OCH0 
Eth 


23 
ene. 
di-acetate. 


CH2OH 


-f      HOC4H70       = 


Ethene 
mono-acetate. 


Butyric 
acid. 


CH2OC4H70 

CH2OC2H30 

Ethene 
butyracetate. 


The  halo'id  acids  act  in  the  same  manner  as  oxygen-acids,  excepting  that 
the  reaction  never  goes  beyond  the  first  stage;  e.  g., 


CH2OH 

CHjOH 

Ethene 
alcohol. 


HC1 


=      OH2 


CH2C1 

CH2OH 
Ethene 
chloro-hydrate. 


The  bichlorinated,  bibrominated  ethers,  &c.,  resulting  from  the  substitu- 
tion of  the  remaining  equivalent  of  hydroxyl  by  the  haloid  element,  may, 
however,  be  obtained  from  the  glycols  by  the  action  of  the  chlorides,  bro- 
mides, and  iodides  of  phosphorus;  e.  g., 


C2H4(OH)2    + 
Ethene 
alcohol. 


2PC16       =       2PC130 


Phosphorus 

penta- 

chloride. 


Phosphorus 

oxy- 
chloride. 


-f       2HC1       -f       C2H4C12 
Hydrogen  Ethene 

chloride.  chloride. 


The  same  compounds  are  produced,  as  already  observed,  by  direct  combi- 
nation of  chlorine,  bromine,  and  iodine  with  the  olefines. 

ETHENE  CHLORIDE,  C2H4C12,  has  long  been  known  by  the  name  of  Dutch 
liquid,  having  been  discovered  by  four  Dutch  chemists  in  1795.  When  equal 
measures  of  ethene  gas  and  chlorine  are  mixed  over  water,  absorption  of 
the  mixture  takes  place,  and  a  yellowish  oily  liquid  is  produced,  which 
collects  upon  the  surface  of  the  water,  and  ultimately  sinks  to  the  bottom 
in  drops.  It  may  be  easily  prepared,  in  quantity,  by  causing  the  two  gases 
to  combine  in  a  glass  globe,  having  a  narrow  neck  at  the  lower  part,  dip- 
ping into  a  small  bottle,  destined  to  receive  the  product.  The  two  gases 
are  conveyed  by  separate  tubes,  and  allowed  to  mix  in  the  globe,  the  ethene 
gas  being  kept  a  little  in  excess.  The  chlorine  should  be  washed  with 
water,  and  the  ethene  passed  through  strong  oil  of  vitriol,  to  remove  vapor 
of  ether:  the  presence  of  sulphurous  and  carbonic  acids  is  not  injurious. 
Combination  takes  place  very  rapidly,  and  the  liquid  product  trickles  down 
the  sides  of  the  globe  into  the  receiver.  When  a  considerable  quantity  has 
been  collected,  it  is  agitated,  first  with  water,  and  afterward  with  concen- 
trated sulphuric  acid,  and,  lastly,  purified  by  distillation. 


DIATOMIC   ALCOHOLS   AND   ETHERS. 


559 


Pure  ethene  chloride  is  a  thin,  colorless  liquid,  of  agreeably  fragrant 
odor,  and  sweet  taste :  it  is  slightly  soluble  in  water,  and  readily  so  in  alco- 
hol and  ether.     It  is  heavier  than  water,  and  boils  when  heated  to  82-3°  C. 
(180°  F.):  it  is  unaffected  by  oil  of  vitriol,  or  solid 
potassium  hydrate.     When  inflamed,  it  burns  with  a  Fig- 192. 

greenish,  smoky  light.  When  treated  with  an  alco- 
holic solution  of  potash,  it  is  slowly  resolved  into 
potassium  chloride,  which  separates,  and  an  exceed- 
ingly volatile  substance,  containing  C2H3C1,  whose 
vapor  requires  to  be  cooled  down  to  — 18°  C.  (0°  F.) 
before  it  condenses.  At  this  temperature  it  forms  a 
limpid,  colorless  liquid.  Chlorine  is  absorbed  by  this 
latter  substance,  and  a  compound  is  produced,  which 
contains  C2H3C13:  this  is  in  turn  decomposed  by  an 
alcoholic  solution  of  potash  into  potassium  chloride 
and  another  volatile  liquid,  C2H2C12.  This  series  of 
reactions  is  analogous  to  that  already  noticed  in  the 
case  of  the  bromine  compounds  (p.  465). 

PRODUCTS  OP  THE  ACTION  OF  CHLORINE  ON  ETHENE 
CHLORIDE  ;  CHLORIDES  OF  CARBON.  —  Ethene  chloride 
readily  absorbs  chlorine  gas,  and  yields  four  new 
compounds,  produced  by  the  abstraction  of  successive 
portions  of  hydrogen,  and  its  replacement  by  equiv- 
alent quantities  of  chlorine.  Three  out  of  the  four 
are  volatile  liquids,  containing  respectively,  C2H3C13, 
C2H2C14,  and  C2HC15;  the  fourth,  C2C16,  in  which  the 
substitution  of  chlorine  for  hydrogen  is  complete,  is 

the  chloride  of  carbon  long  ago  obtained  by  Faraday  by  putting  Dutch  liquid 
into  a  vessel  of  chlorine  gas,  and  exposing  it  to  sunshine. 

CC13 
Carbon  trichloride,  C3CL,  or    I      ,  the  chlorine  analogue  of  ethane,  C2H6, 

CC13 

is  a  white,  crystalline  substance,  of  aromatic  odor,  insoluble  in  water,  but 
easily  dissolved  by  alcohol  and  ether:  it  melts  at  160°  C.  (320°  F.),  and 
boils  at  a  temperature  a  little  above.  It  burns  with  difficulty,  and  is  not 
altered  by  distillation  with  aqueous  or  alcoholic  potash. 
•  Its  vapor,  passed  through  a  red-hot  porcelain  tube  filled  with  fragments 
of  glass  or  rock-crystal,  is  decomposed  into  free  chlorine,  and  the  dichlo- 
ride,  C2C14,  analogous  to  ethene.  This  substance  condenses  in  the  form  of 
a  volatile,  colorless  liquid,  which  has  a  density  of  1*55,  and  boils  at  120° 
C.  (248°  F.).  The  density  of  its  vapor  is  5-82  (referred  to  air).  When 
heated  to  200°  C.  (392°  F.)  with  potassium  hydrate,  it  is  completely  con- 
verted into  potassium  chloride  and  oxalate,  with  evolution  of  hydrogen: 


C2C14    -f-     GKOH    =    4KC1    + 


-f-     20H,    +     Hs 


It  absorbs  chlorine  and  bromine  in  sunshine,  forming  in  the  one  case  the 
trichloride,  C2C16,  and  on  the  other  the  chlorobromide,  C2Cl4Br2,  a  white 
crystalline  body  resembling  the  trichloride. 

Carbon  monochloride,  C2C12,  analogous  to  ethine  or  acetylene,  is  obtained 
by  passing  the  vapor  of  chloroform  or  of  carbon-dichloride  through  a  red- 
hot  tube.  It  forms  white  needles  subliming  between  175°  and  200°  C.  (347° 
and  392°  F.). 

Carbon  tetrachloride,  CC14,  may  also  be  described  in  this  place,  though  it 
belongs  to  another  series,  being  the  chlorine  analogue  to  marsh-uus. 

It  is  formed  by  passing  the  vapor  of  carbon  bisulphide,  together  witli 
chlorine,  through  a  red-hot  porcelain  tube.  A  mixture  of  sulphur  chloride 


560  DIATOMIC   ALCOHOLS   AND   ETHERS. 

and  carbon  tetrachloride  is  formed,  which  is  distilled  with  potash,  where'by 
the  chloride  of  sulphur  is  decomposed,  and  pure  tetrachloride  passes  over. 
It  is  a  colorless  liquid  of  1-56  sp.  gr.,  and  boils  at  77?  C  (170°  F.).  The 
same  compound  is  formed  by  exhausting  the  action  of  chlorine  upon  marsh- 
gas  or  methyl  chloride  in  sunshine.  An  alcoholic  solution  of  potash  con- 
verts this  compound  into  a  mixture  of  potassium  chloride  and  carbonate. 

ETHENE  BROMIDE  AND  IODIDE,  C2H4Br2  and  C2H4I2,  are  produced  by 
bringing  olefiant  gas  in  contact  with  bromine  and  iodine.  The  bromide  is 
a  colorless  liquid,  of  agreeable  ethereal  odor,  and  has  a  density  of  2-16: 
it  boils  at  129-5°  C.  (265°  F.),  and  solidifies  when  cooled  to  near — 18°. 
The  iodide  is  a  colorless,  crystalline,  volatile  substance,  of  penetrating 
odor:  it  melts  at  79°  C.  (174°  F.),  resists  the  action  of  sulphuric  acid,  but 
is  decomposed  by  caustic  potash. 

The  action  of  bromine  upon  ethene  bromide  gives  rise  to  the  compound 
C2H3Br3,  from  which  the  other  bromine-compounds  corresponding  to  the 
chlorine  bodies  above  mentioned  may  be  obtained  by  treatment  with 
bromine. 

Ethene  bromide  acts  strongly  upon  an  alcoholic  solution  of  potassium 
sulph- hydrate,  forming  ethene  sulph-hydrate  or  ethene  mercaptan,  C2H4(SH)2,  a 
colorless  oil,  which  is  partially  decomposed  by  distillation,  and  yields,  with 
lead  acetate,  a  yellow  precipitate  consisting  of  C2H4S2Pb.  With  potassium 
monosulphide,  in  like  manner,  ethene  bromide  forms  ethene  sulphide,  C2H4S, 
which  crystallizes  in  white  prisms. 

The  haloid  ethers  corresponding  to  the  higher  glycols  are  similar  in  their 
reactions  to  those  of  ethene  alcohol. 

OXYGEN  ETHERS  OF  THE  GLYCOLS. — The  ethereal  salts  of  the  glycols 
(acetates,  butyrates,  &c.)  are  decomposed  by  alkalies  in  the  same  manner 
as  those  of  the  monatomic  alcohols,  reproducing  the  alcohols  themselves: 
this  is,  in  fact,  the  general  mode  of  preparing  the  glycols  (p.  556).  But 
the  mono-acid  haloi'd  ethers  of  the  glycols  are  decomposed  by  alkalies  in  a 
different  manner,  giving  up  the  elements  of  hydrochloric,  hydriodic,  or 
hydrobromic  acids,  and  leaving  an  oxide  of  the  diatomic  alcohol-radical; 
thus, 

(C2H4)"C1(OH)  +  KOH  =  KC1  -f  OH2  -f  (C2H4)"0 

Ethene  Ethene 

chloro-hydrate.  oxide. 

Ethene  oxide  is  isomeric  with  aldehyde  and  with  vinyl  alcohol  (p.  484). 
It  is  a  transparent  colorless  liquid,  boiling  at  13-5°  C.  (56°  F.,)  (aldehyde 
boils  at  21°  C.  [70°  F.]),  and  miscible  in  all  proportions  with  water  and 
with  alcohol.  When  the  aqueous  solution  is  treated  with  sodium  amalgam, 
in  a  vessel  surrounded  with  a  freezing  mixture,  the  ethene  oxide  takes  up 
hydrogen,  and  is  converted  into  ethyl  alcohol: 

C2H40         +         H2        =        C2H60. 

Ethene  oxide  unites  with  ammonia  in  several  proportions,  forming  the 
following  basic  compounds,  all  of  which  are  syrupy  liquids: 

Monoxethylenamine         .....      C2H4O.NH3 

Dioxethylenamine (C2H40)2.NH3 

Trioxethylenamine (C2H40)3.NH3 

Tetroxethylenamine (C2H40)4.NH3. 

This  character  distinguishes  ethene  oxide  from  aldehyde,  which  forms 
with  ammonia  a  crystalline  compound  not  possessing  basic  properties.  A 
further  distinction  between  these  two  isomeric  bodies  is,  that  aldehyde 
forms  crystalline  compounds  with  the  acid  sulphites  of  the  alkali-metals, 
a  property  not  possessed  by  ethene  oxide. 


DIATOMIC   ALCOHOLS   AND   ETHERS. 


561 


Ethene  oxide  is  a  powerful  base,  uniting  directly  with  acids,  precipitating 
magnesia  from  a  solution  of  magnesium  chloride  at  ordinary  temperatures, 
and  ferric  oxide  and  alumina  from  their  saline  solutions,  at  100°  C.  With 


and  with 


hydrochloric  acid,  it  forms  ethene  chlorohydrate,  (C2H4)//  \  ,-.„, 

acetic  acid,   ethene  acetohydrate,  or  monoacetate,    (C2H4)//|0ij2    3   m     it 

also  unites  with  water  in   several  proportions,  forming  glycol  and  other 
compounds  to  be  noticed  immediately. 

The  oxygen-ethers  'of  the  higher  glycols  are  not  much  known ;  but  they 
appear  to  be  less  disposed  to  combine  with  water  and  acids  in  proportion 
as  their  molecules  become  heavier;  thus  amylene  oxide  does  not  appear  to 
reproduce  amylene  alcohol  by  combination  with  water. 

Polyethenic  Alcohols.  —  These  are  bodies  which  contain  the  elements  of 
two  or  more  molecules  of  ethene  oxide  combined  with  one  molecule  of 
water,  and  may  be  regarded  as  formed  by  the  union  of  two  or  more  mole- 
cules of  glycol  (mono-ethenic  alcohol),  with  elimination  of  a  number  of 
water-molecules  less  by  one  than  the  number  of  glycol  molecules  which 
enter  into  combination;  or  as  derived  from  three  or  more  molecules  of 
water,  by  substitution  of  ethene  for  the  whole  of  the  hydrogen  except  two 
atoms;  thus, 


C2H602  or  (C2H4)"H202 

Monethenic  alcohol 

(glycol). 


C4Hlq03  or  (C2H4)'/2H20; 
Diethenic  alcohol. 


C2H4O.OH2 

Ethene 

oxide. 

2C2H4O.OH2 

Ethene 

oxide. 


2C2H60— OH2 

Glycol. 


C6H1404  or  (C2H4)"3H204 
Triethenic  alcohol. 


=    3C2H4O.OH2  =    3C2H60— 20H2 
Ethene  Glycol. 

oxide. 


Ethene 
oxide. 


Glycol. 


C8H1806or(C2H4)"4H205 
Tetrethenic  alcohol. 

Generally  — 

C2nH4n+2On+I  or  (C2H4)"nHaOn+,  ==  nC2H4O.OH2      =  wC2H60— (n— 1)OH2 
n-ethenic  alcohol.  Ethene  Glycol. 

oxide. 

The  polyethenic  alcohols  are  formed:  1.  By  heating  ethene  oxide  with 
water  in  sealed  tubes.  In  this  manner  Wurtz  obtained  diethenic  alcohol 
together  with  monethenic,  and  a  small  quantity  of  tri-ethenic  alcohol.  — 
2.  By  heating  ethene  oxide  with  glycol  in  sealed  tubes:  this  process  yields 
the  di- and  tri-ethenic  alcohols.  —  3.  By  heating  glycol  with  ethene  bro- 
mide in  sealed  tubes  to  100°-120°  C.  (212°-248°  F.).  The  first  products  of 
this  reaction  are  diethenic  alcohol,  ethene  bromo-hydrate  and  water : 


8(C,H4)"H,Oa 

Monethenic 
alcohol.  bromide.  alcohol. 


C2H4Br2   =  (C2H4)"2H203 
Ethene  Diethenic 


2(C2H4)"Br(OH) 
Ethene  bromo- 
hydrate. 


OH 


and  the  other  polyethenic  alcohols  are  formed,  each  from  the  one  next  be- 
low it  in  the  series,  by  the  action  of  ethene  bromo-hydrate,  according  to 
the  general  equation: 

(C2H4)"nH2On+I  +  (<yi4)"Br(OH)  =  (C2H4)^n+1H2On+2  +  HBr. 


562  ALCOHOLS   AND   ETHERS. 

The  hydrobromie  acid  thus  formed  then  acts  on  the  excess  of  glycol  present, 
reproducing  ethene  bromo-hydrate,  and  thus  the  action  is  continued.  By 
this  process,  the  2-,  3-,  4-,  5-,  and  6-ethenic  alcohols  have  been  obtained 
and  separated  by  fractional  distillation ;  and  when  a  sufficient  excess  of 
glycol  is  present,  the  temperature  being  kept  between  110°  and  120°  C. 
(230°  and  248°  F.),  still  higher  members  of  the  series  are  produced.* 

The  polyethenic  alcohols  are  syrupy  liquids,  becoming  more  viscid  as 
their  molecular  weight  increases:  their  boiling  point  rises  by  about  45°  for 
each  addition  of  C2H40 

Diethenic  alcohol,  C4H1003,  or  (C4H4)-'/tH,Os,  boils  at  about  245°;  the  den- 
sity of  its  vapor  is  3-78  referred  to  air  as  unity ;  by  calculation  it  should 
be  3-67,  so  that  it  exhibits  the  normal  condensation  to  two  volumes.  By 
contact  with  platinum-black,  or  by  treatment  with  nitric  acid,  it  is  oxidized 
to  diyly  collie  acid,  C4H605,  an  acid  isomeric  with  malic  acid,  and  formed 
from  diethenic  alcohol  by  substitution  of  O  for  H2,  just  as  glycollic  acid, 
C2H403,  is  formed  from  monethenic  alcohol,  C2H60. — Triethenic  alcohol, 
C6HUO4,  or  (C2HJ"3H204,  is  oxidized  in  like  manner  to  ethene- digly collie  acid, 
C6H1205. 


2.— Diatomic  Phenols,  CnB^./^. 

There  are  five  known  compounds  included  in  this  general  formula,  viz. : 
Oxyphenol  or  Pyrocatechin  ....  C6H602 

Orcin  \  r  TT  O 

Guaiacol  (in  part)       / 

Creosol     \  n  TT  n 

Veratrol  /  '  ^10^2 

Oxyphenol,  Oxyphenic  Acid,  or  Pyrocatechin,  C6H602,  or  (C6H4)//(OH)2, 
is  produced  by  heating  oxysalicylic  acid  to  210°-212°,  just  as  phenol  is 
produced  from  salicylic  acid : 

C?H6Or       =        C02        +        C6H602; 
Oxysalicylic  acid.  Oxyphenol. 

also  by  the  action  of  alkalies  on  iodophenol : 

C6H4T(OH)        -f        KOH        =        KI        -f        C6H4(OH)2 
Iodophenol.  Oxyphenol. 

It  is  likewise  formed  by  the  dry  distillation  of  catechin  (a  substance  ob- 
tained from  catechu),  of  morintannic  acid  (the  yellow  coloring  matter  of 
Morus  tinctorial),  and  of  wood,  whence  it  is  found  in  wood  vinegar:  it  does 
not  occur  in  coal-tar.  It  is  a  white  crystalline  body,  which  melts  at  111° 
or  112°  C.  (230°-233°  F.),  and  volatilizes  even  at  lower  temperatures.  It 
has  a  bitter  taste,  and  scarcely  reddens  litmus.  In  contact  with  hydro- 
chloric acid,  it  colors  fir-wood  violet.  It  dissolves  in  water,  alcohol,  and 
ether.  The  aqueous  solution  forms  a  white  precipitate  with  lead  acetate, 
and  colors  ferric  salts  dark-green.  Nitric  acid  acts  upon  it  with  violence, 
forming  oxalic  acid  and  a  small  quantity  of  a  yellow  nitro-compound,  prob- 
ably nitro-oxyphcnol.  With  acetyl  chloride  it,  forms  acetoxyphenol,  CCH5 
(C2H30)02,  and  with  benzoyl  chloride,  benzoxyphenol,  C6H5(C7H50)02,  both 
of  which  are  crystalline  bodies. 

Orcin,  CTH802.— This  substance  appears  to  exist  ready  formed  in  all  the 
lichens  (Lecanora  tartar ea,  Roccella  tinctoria,  Variolaria  orcina,  &c.),  which 
*  Lourenzo,  Ann.  Ch.  Pharm.  cxvii.  269. 


DIATOMIC    PHENOLS.  563 

are  used  for  the  preparation  of  archil  and  litmus ;  and  is  the  general  pro- 
duct of  the  decomposition  of  certain  acids  extracted  from  those  lichens 
(orsellinic  acid,  erythric  acid,  £c  )  under  the  influence  of  heat  or  of  alka- 
lies. Orsellinic  acid,  C8H804,  when  boiled  with  baryta-water,  splits  up  into 
carbon  dioxide  and  orcin,  just  as  the  homologous  acid,  oxysalicylic  acid, 
C7H604,  splits  up  into  carbon  dioxide  and  oxyphenol  (p.  562) : 

C8H804  '     =.       C02        +        C7H802 

Hence  orcin  appears  to  have  the  constitution  of  a  diatomic  phenol.  To  ob- 
tain the  orcin,  the  excess  of  baryta  is  precipitated  from  the  liquid  by  car- 
bonic acid,  and  the  nitrate  evaporated  to  a  small  bulk.  It  forms,  when 
pure,  large  square  prisms,  which  have  a  slightly  yellowish  tint,  an  intensely 
sweet  taste,  and  a  high  degree  of  solubility  both  in  water  and  alcohol. 
When  heated,  it  loses  water,  and  melts  to  a  syrupy  liquid,  which  distils  un- 
changed. The  crystals  of  orcin  contain  C7H802 .  OH2.  It  forms  substitu- 
tion-products with  chlorine  and  bromine. 

ORCEIN. — When  ammonia  is  added  to  a  solution  of  orcin,  and  'the  whole 
is  exposed  to  the  air,  the  liquid  assumes  a  dark-red  or  purple  tint  by  ab- 
sorption of  oxygen ;  a  slight  excess  of  acetic  acid  then  causes  the  precipi- 
tation of  a  deep-red  powder,  not  very  soluble  in  water,  but.  freely  dissolved 
by  ammonia  and  fixed  alkalies,  with  a  purple  or  violet  color.  This  powder 
is  an  azotized  substance,  orcein,  formed  from  the  elements  of  the  ammonia 
and  the  orcin ;  it  probably  constitutes  the  chief  ingredient  of  the  red  dye- 
stuff  of  the  commercial  articles  before  mentioned.  Orcein  probably  con- 
tains C7H7N03,  according  to  which  formula,  its  formation  from  orcin,  under 
the  joint  influence  of  oxygen  and  ammonia,  may  be  represented  by  the 
equation : 

C7H802     -f     NH3     +     03    =    C7H7N03    +     20H2. 

Guaiacol  and  Creosol. — Guaiacum,  a  yellow  or  brown  resin  exuding  from 
a  West  Indian  tree  (Guatacum  officinalc),  yields  by  dry  distillation  an  oily 
liquid,  which,  when  washed  with  water  and  rectified  at  a  moderate  heat, 
gives  off,  first,  guaiaccne,  C5H80,  and  afterward  a  colorless  oil  called  guaia- 
col.  This  compound  has  a  specific  gravity  of  1-119  at  22°  C.  (72°  F.),  and 
boils  at  210°  C.  (410°  F  ).  It  is  soluble  in  alcohol,  slightly  soluble  in 
water.  Nitric  acid  converts  it  into  oxalic  acid  and  a  brown  resin.  With 
chlorine  and  bromine  it  forms  substitution-products.  It  dissolves  in  potash, 
and  forms  crystallizable  salts  with  other  bases.  Guaiacol  is  not,  however, 
a  perfectly  definite  compound,  but  a  mixture  in  varying  proportions  of  the 
homologous  compounds  C7H802  and  C8H1002.  The  latter  compound  likewise 
exists  in  some  kinds  of  wood-creosote  :  hence  it  is  called  creosoL 

CREOSOTE  OR  KREOSOTE. — This  substance,  discovered  by  Reichenbach, 
is  contained  in  many  kinds  of  wood-tar,  but  most  abundantly  in  the  heavy 
oil  of  beech-tar,  as  obtained  from  the  wood-vinegar  makers.  It  is  extracted 
and  purified  by  a  series  of  processes  similar  to  those  employed  for  the  pre- 
paration of  phenol  or  carbolic  acid  from  coal-tar  (p.  550). 

Creosote  is  a  colorless,  somewhat  viscid  oily  liquid,  of  great  refractive 
and  dispersive  power.  It  is  quite  neutral  to  test-paper;  has  a  penetrating 
and  most  peculiar  odor,  that,  namely,  of  smoked  meat,  and  a  pungent  and 
almost  insupportable  taste  when  placed  even  in  very  small  quantity  upon 
the  tongue.  Its  density  is  1-037,  and  its  boiling-point  about  203°  C. 
(397°  F  ).  It  takes  fire  with  difficulty,  and  then  burns  with  a  smoky  light. 
When  quite  pure,  it  is  not  altered  by  exposure  to  the- air;  but  much  of  the 
creosote  of  commerce  gradually  turns  brown  under  these  circumstances. 
100  parts  of  cold  water  take  up  about  1}  part  of  creosote;  at  a  high  tem- 
perature rather  more  is  dissolved,  and  the  hot  solution  abandons  a  portion 


564:  ALCOHOLS   AND    ETHERS. 

on  cooling.  The  creosote  itself  absorbs  water  also  to  a  considerable  extent. 
In  acetic  acid  it  dissolves  in  much  larger  quantity.  Alcohol  and  ether  mix 
with  creosote  in  all  proportions.  Concentrated  sulphuric  acid,  by  the  aid 
of  heat,  blackens  and  destroys  it.  Caustic  potash  dissolves  creosote  with 
great  facility,  and  forms  with  it  a  compound,  which  crystallizes  in  brilliant 
pearly  scales,  and  consists,  according  to  Hlasiwetz,*  of  potassium  creosolate, 
C8H9K0220H2.  When  distilled  with  dilute  sulphuric  acid,  it  yields  creosol, 
C8H,002.  By  treating  creosote  with  potassium  in  an  atmosphere  of  hydrogen, 
and  crystallizing  the  product  from  ether,  an  acid  potassium  creosolate  is 
obtained,  consisting  of  C8H9K02.  C8H1002. 

Hlasiwetz  regards  beech-tar  creosote  as  an  ether  of  creosol,  represented 
either  by  the  formula  C8H9R02,  or  by  C8H9R02.  C8H,002,  in  which  R  denotes 
a  monatomic  alcohol-radical.  According  to  Frisch,f  it  consists  mainly  of 
acid  phenylic  creosol,  C8H9(C6H5)02.  C8H1002.  It  may  be  distinguished 
from  phenol  by  its  behavior  to  ferric  chloride,  an  alcoholic  solution  of  that 
salt  producing  a  green  color  with  creosote  and  brown  with  phenol ;  an 
aqueous  solution  gives  no  color  with  creosote  and  a  blue  color  with  phenol. 
The  creosote  of  commerce  is,  however,  a  substance  of  very  variable  consti- 
tution, much  of  it  being  nothing  but  impure  phenols  (commonly  called 
coal-tar  creosote).  The  tar  of  pine-wood,  as  already  observed  (p.  553),  con- 
sists mainly  of  phenol  and  creosol. 

The  most  characteristic  property  of  wood-creosote  is  its  extraordinary 
antiseptic  power,  which  appears  to  be  even  greater  than  that  of  phenol.  A 
piece  of  meat  steeped  in  a  very  dilute  solution  of  creosote  dries  up  to  a 
mummy-like  substance,  but  absolutely  refuses  to  putrefy.  The  well-known 
efficacy  of  impure  wood-vinegar  and  of  wood-smoke  in  preserving  provisions 
is  doubtless  to  be  attributed  to  the  creosote  which  they  contain.  Both 
creosote  and  phenol  are  used  by  the  dentist  for  relieving  toothache  arising 
from  putrefactive  decay  in  the  substance  of  the  tooth. 

Veratrol,  C8H1002. — This  compound  is  obtained  by  distilling  veratric  acid 
(an  acid  extracted  from  the  seeds  of  Veratrum  Sabadilla)  with  excess  of 
baryta  at  a  gentle  heat,  the  mode  of  formation  being  that  of  the  phenols  in 
general  from  the  corresponding  acids  of  the  series  CnH2n— 804. 

C9H1004        =         C02        +        C8H1002. 
Veratric  acid.  Veratrol. 

Veratrol  is  a  colorless  oil  having  an  agreeable  aromatic  odor,  and  specific 
gravity  1-086  at  15° ;  it  solidifies  at  15°  C.  (59°  F.),  and  boils  at  202°-205° 
C.  (395°-401°  F.).  Bromine  converts  it  into  dibromoveratrol,  C8H8Br202, 
which  forms  prismatic  crystals.  Nitric  acid  acts  strongly  upon  it,  forming 
nitroveratrol,  C8H9(N02)02,  which  crystallizes  from  alcohol  in  yellow  laminse, 
and  dinitroveratrol,  C8Hg(N02)202,  which  crystallizes  in  yellow  needles,  melt- 
ing at  100°,  and  then  volatilizing  without  decomposition. 

Anisic  Alcohol,  C8H,002. — Crude  anise  oil,  the  essential  oil  of  Pimpinella 
Anisum,  contains  a  crystalline  substance,  C10H,20,  called  anethol  or  anise 
camphor.  This  substance  when  oxidized  with  nitric  acid  is  converted  into 
anisic  aldehyde,  C8H802,  which,  when  treated  with  alcoholic  potash,  takes 
up  two  atoms  of  hydrogen  and  is  converted  into  anisic  alcohol,  C8H1002  (just 
as  benzoic  aldehyde,  C7H00,  under  similar  circumstances  yields  benzyl 
alcohol,  C7H80 ;  p.  548).  Now  this  alcohol,  though  it  contains  two  atoms  of 
oxygen,  nevertheless  behaves,  not  like  a  diatomic,  but  like  a  monatomic 
alcohol,  yielding  only  one  series  of  ethers.  The  so-called  anisic  alcohol 
appears,  indeed,  to  be  really  the  methylic  ether  of  the  diatomic  alcohol, 

*  Ann.  Ch.  Pharm.  cvi.  339.  f  Journal  fur  praktische  Chemie,  c.  283. 


TBIATOMIC   ALCOHOLS   AND   ETHERS.  565 

CTH802,  its  formula  being  C7H6(OCH3)OH;  so  that  it  contains  only  one  atom 
of  replaceable  hydrogen.  Hydrochloric  acid  gas  converts  it  into  the  cor- 
responding hydrochloric  ether,  C8H9C1(OH),  or  C7H6(OCH3)C1(OH). 


TRIATOMIC  ALCOHOLS  AND  ETHERS. 

Triatomic  alcohols  may  be  derived  from  saturated  hydrocarbons  by  sub- 
stitution of  three  equivalents  of  hydroxyl  for  three  atoms  of  hydrogen,  and 
may  accordingly  be  regarded  as  compounds  of  trivalent  alcohol  radicals 
with  three  equivalents  of  hydroxyl,  or  as  compounds  derived  from  a  triple 
molecule  of  water,  by  substitution  of  a  trivalent  radical  for  three  atoms  of 
hydrogen.  The  hydrocarbons  of  the  paraffin  series,  CnH:>n+2.  should  ac- 
cordingly yield  a  series  of  triatomic  alcohols  of  the  form  (CnH2n_,)///(OH)3, 
yiz. : — 

Methenyl  alcohol CH(OH)3 

Ethenyl  alcohol C2H3(OH)S 

Propenyl  alcohol C3H5(OH)3 

Quartenyl  alcohol C4H7(OH)3 

Quintenyl  alcohol C6H9(OH)3 

&c.  &c. 

Of  these,  however,  only  two  are  known,  viz.,  propenyl  alcohol,  or  glycerin, 
and  quintenyl  alcohol,  or  amyl  glycerin.  There  are  also  two  or  three  bodies 
which  may  be  regarded  as  triatomic  phenols,  represented  by  the  general 
formula  CnH,n_«08,  or  CnH2n_9(OH3). 

Each  triatomic  alcohol,  subjected  to  the  action  of  acids,  or  of  the  chlo- 
rides, bromides,  or  iodides  of  phosphorus,  may  yield  three  classes  of  ethers, 
derived  from  it  by  substitution  of  a  halogen  element,  or  acid  radical,  for 
part  or  the  whole  of  the  hydroxyl;  thus,  from  glycerin  may  be  obtained 
the  three  hydrochloric  ethers,  C3H5C1(OH)2,  C3H6C12OH,  C3H5C13,  and  the 
three  acetic  ethers,  C3H5(OC2H30)(OH)2,  C3H5(OC2H30)2OH,  and  C3H5 
(OC2H30)3. 

Methenyl  Ethers. — Methenyl  alcohol,  CH(OH)3,  has  not  been  obtained; 
but  ethers  are  known  which  may  be  derived  from  it,  by  substitution  of 
halogen  elements  for  the  three  equivalents  of  hydroxyl,  CHC13  for  example. 
These  compounds,  which  may  also  be  directly  derived  from  methane,  are 
usually  distinguished  bynames  ending  in  "form,"  to  denote  their  relation 
to  formic  acid,  (CH)///0(OH). 

METHENYL  CHLORIDE  OR  CHLOROFORM,  CHC13.  —  This  compound  is  pro- 
duced: 1.  Together  with  methene  chloride,  CH2C12,  when  a  mixture  of 
chlorine  and  gaseous  methyl  chloride  is  exposed  to  the  sun's  rays.  — 2.  By 
the  action  of  alkalies  on  chloral  (p.  517): 

C2HC130        -f        KOH        =         CHC13        +        CH02K 
Chloral.  Cnloro-  Potassium 

form.  formate. 

3.  By  boiling  trichloracetic  acid  with  aqueous  alkalies: 

C2HC1302       -f      2KOH      =      CHC13      -f       C03K2      -f      OH2 
Trichlor-  Chloro-  Potassium 

acetic  acid.  form.  carbonate. 

4.  By  the  action  of  nascent  hydrogen  on  carbon  tetrachloride : 

CC14        +         H2        =         HC1         -f         CHCL,. 
48 


566  TRIATOMIC   ALCOHOLS   AND   ETHERS. 

5.  By  the  action  of  hypochlorites,  or  of  chlorine  in  presence  of  alkalies, 
on  various  organic  substances,  as  methyl,  ethyl,  and  amyl  alcohols,  acetic 
acid,  acetone,  &c.  The  reaction  is  complicated,  giving  rise  to  several  other 
products ;  with  common  alcohol  and  calcium  hypochlorite  the  principal 
reaction  appears  to  be  — 

2C2H60  +  5Cl202Ca  =  2CHCL,  +  2C03Ca  -f  2CaCl2  -f  CaH202  -f  40 H2. 

Chloroform  is  prepared  on  the  large  scale  by  cautiously  distilling  together 
good  commercial  chloride  of  lime,  water,  and  alcohol.  The  whole  product 
distils  over  with  the  first  portions  of  water,  so  that  the  operation  may  be 
soon  interrupted  with  advantage.  The  chloroform,  which  constitutes  the 
oily  portion  of  the  distillate,  is  purified  by  agitation  with  water,  desicca- 
tion with  calcium  chloride,  and  distillation  in  a  water-bath. 

Chloroform  is  a  thin,  colorless  liquid  of  agreeable  ethereal  odor,  much 
resembling  that  of  Dutch  liquid,  and  of  a  sweetish  taste.  Its  density  is 
1-48,  and  it  boils  at  61°  C.  (142°  F.):  the  density  of  its  vapor  (compared 
with  air)  is  4-20.  Chloroform  is  difficult  to  kindle,  and  burns  with  a  green- 
ish flame.  It  is  nearly  insoluble  in  water,  and  is  not  affected  by  concen- 
trated sulphuric  acid.  When  boiled  with  aqueous  potash  in  a  closed  tube, 
it  is  converted  into  potassium  chloride  and  formate : 

CHC13        +        4HOK        =      3KC1      +       CHO(OK)      +      20H2 
Chloroform.  Potassium  Potassium 

hydrate.  formate. 

Chloroform  is  well  known  for  its  remarkable  effects  upon  the  animal 
system,  in  producing  temporary  insensibility  to  pain  when  its  vapor  is 
inhaled. 

BROMOFORM,  CHBr3,  is  a  heavy,  volatile  liquid,  prepared  by  the  simul- 
taneous action  of  bromine  and  aqueous  alkalies  on  alcohol,  wood-spirit, 
and  acetone.  It  is  converted  by  caustic  potash  into  potassium  bromide 
and  formate. 

IODOFORM,  CHI3,  is  a  solid,  yellow,  crystallizable  substance,  easily  ob- 
tained by  adding  alcoholic  solution  of  potash  to  tincture  of  iodine,  avoiding 
excess,  evaporating  the  whole  to  dryness,  and  treating  the  residue  with 
water.  It  is  nearly  insoluble  in  water,  but  dissolves  in  alcohol,  and  is  de- 
composed by  alkalies  in  the  same  manner  as  the  preceding  compounds. 
Bromine  converts  it  into  bromiodoform,  CHBr2I,  a  colorless  liquid  which 
solidifies  at  0°.  lodoform  distilled  with  phosphorus  pentachloride  or  mer- 
curic chloride,  is  converted  into  chloriodoform,  CHC12I,  a  colorless  liquid 
of  sp.  gr.  1-96,  which  does  not  solidify  at  any  temperature.  Nitroform, 
CH(N02)3,  a  body  analogous  in  composition  to  the  methenyl  ethers,  will  be 
considered  in  connection  with  the  cyanogen  compounds. 

Propenyl  Alcohol,  or  Glycerin, 

CH2OH 

(OH  | 

C3H803        =        (C3H5)'"JOH        or        CHOH 

(OH 

CH2OH 

This  compound  is  obtained  by  the  action  of  alkalies  on  natural  fats, 
which  are,  in  fact,  the  propenylic  ethers  of  certain  fatty  acids;  thus 
stearin,  one  of  the  constituents  of  mutton  suet,  consists  of  propenyl  tri- 
stearate,  (C3H5)///(OC18H350)3,  a  compound  derivable  from  glycerin  itself,  by 
substitution  of  stearyl,  C]8H350,  for  hydrogen.  Now,  when  stearin  is 
boiled  with  a  caustic  alkali,  it  is  converted  into  a  stearate  of  the  alkali- 
metal  and  glycerin,  thus ; 


GLYCEKIlSr.  567 

C3H6(OC1?H350)3    +     3KOH    =    3KOC18H350     -f     C,H6(OH)8 
Stearin.  Potassium  Glycerin. 

stearate. 

A  similar  reaction  takes  place  when  any  other  similarly  constituted  fat  is 
treated  with  a  caustic  alkali.  The  metallic  salts  of  the  fatty  acids  thus 
obtained  are  the  well-known  bodies  called  soaps,  and  the  process  is  called 
saponification  ;  this  term,  originally  restricted  to  actual  soap-making,  has 
been  extended  to  all  cases  of  the  resolution  of  a  compound  ether  into  an 
acid  and  an  alcohol,  such,  for  example,  as  the  conversion  of  ethyl  acetate 
into  acetic  acid  and  ethyl  alcohol  by  the  action  of  alcoholic  potash. 

Glycerin  was  originally  obtained  by  heating  together  olive  or  other  suit- 
able oil,  lead  oxide,  and  water,  as  in  the  manufacture  of  common  lead-plaster  ; 
an  insoluble  soap  of  lead  is  thereby  formed,  while  the  glycerin  remains  in 
the  aqueous  liquid.  The  latter  is  treated  with  sulphuretted  hydrogen, 
digested  with  animal  charcoal,  filtered  and  evaporated  in  a  vacuum  at  the 
temperature  of  the  air.  Glycerin  is  now  produced  in  very  large  quantity 
and  perfect  purity  in  the  decomposition  of  fatty  substances  by  means  of 
overheated  steam,  a  process  which  Mr.  George  Wilson  has  lately  introduced 
into  the  manufacture  of  candles.*  In  this  reaction  a  fatty  acid  and 
glycerin  are  produced  by  assimilation  of  the  elements  of  water  ;  they  are 
carried  over  by  the  excess  of  steam  in  a  state  of  mechanical  mixture,  which 
rapidly  separates  into  two  layers  in  the  receiver.  The  reaction  is  exactly 
similar  to  that  which  takes  place  when  a  caustic  alkali  is  used  to  effect  the 
saponification,  e.  g.  : 


C3H5(OC1?H350)3    +     30H2    =    SHOCjgH^O     +     C3H5(OH)3 
Stearin.  Stearic  acid.  Glycerin. 

Glycerin  may  also  be  produced  from  propenyl  bromide,  (C<Hi)///Bjv  a 
compound  formed,  as  already  observed,  by  the  action  of  bromine  on  allyl 
iodide,  C3H5I.  The  process  consists  in  converting  the  propenyl-bromide 
into  propenyl  triacetate,  (C3H6)///(OC2H30)3,  by  the  action  of  silver  acetate, 
and  decomposing  this  compound  ether  with  potash. 

This  mode  of  formation  must  not,  however,  be  regarded  as  an  actual 
synthesis  of  glycerin  from  compounds  of  simpler  constitution  ;  for  the 
allyl-compounds  are  themselves  prepared  from  glycerin  (p.  544),  and  have 
never  yet  been  obtained  from  any  other  source. 

.  Glycerin  is  a  nearly  colorless  and  very  viscid  liquid,  of  sp.  gr.  1-27,  which 
cannot  be  made  to  crystallize.  It  has  an  intensely  sweet  taste,  and  mixes 
with  water  in  all  proportions  :  its  solution  does  not  undergo  the  alcoholic 
fermentation,  but  when  mixed  with  yeast  and  kept  in  a  warm  place,  it  is 
gradually  converted  into  propionic  acid.  Glycerin  has  no  action  on  vege- 
table colors.  Exposed  to  heat,  it  volatilizes  in  part,  darkens,  and  decom- 
poses, giving  off',  amongst  other  products,  a  substance  called  acrolein,  C3H40, 
having  an  intensely  pungent  odor. 

Concentrated  nitric  acid  converts  glycerin  into  glyccric  acid,  C3H604.  an  acid 
related  to  glycerin  in  the  same  manner  as  glycollic  acid  to  glycol,  and 
acetic  acid  to  ethyl  alcohol  ;  being  formed  from  it  by  substitution  of  oxygen 
for  two  atoms  of  hydrogen  in  immediate  relation  to  hydroxyl;  thus: 

CH2OH  CH.OH 

CHOH      -f      Oa      =      OH2      +         CHOH 

CH2OH  COOH 

Glycerin.  Glyceric  acid. 

*  By  Tilghman's  process,  an  emulsion  of  water  and  fat  is  passed  under  pressure  through  a 
highly  heated  tul>e,  and  alter  delivery  at  tho  extreme  end  separates  into  a  solution  of 
glycerin  and  the  fatty  acid.  —  11.  B. 


568  TKIATOMIC   ALCOHOLS    AND   ETHERS. 

The  formula  of  glycerin  indicates  the  possibility  of  effecting  a  second  sub- 
stitution of  the  same  kind,  which  would  yield  diglyceric  acid,  C3H406,  but 
this  acid  has  not  been  actually  obtained. 

Glycerin,  treated  with  a  mixture  of  strong  nitric  and  sulphuric  acids, 
forms  nitroglycerin,  C3H5(N02)303,  a  heavy  oily  liquid  which  explodes  power- 
fully by  percussion.  It  is  much  used  for  blasting  in  mines  and  quarries, 
but  is  very  dangerous  to  handle,  and  has  given  rise  to  several  fatal  ac- 
cidents. 

Glycerin  combines  with  the  elements  of  sulphuric  acid,  forming  a  sul- 
phogly  eerie  acid,  C3H803S03,  wrhich  gives  soluble  salts  with  lime,  baryta,  and 
lead  oxide. 

Monatomic  oxygen  acids  (acetic,  benzoic,  stearic,  &c.),  heated  in  sealed 
tubes  with  glycerin,  yield  compound  ethers,  in  which  1,  2,  or  3  hydrogen- 
atoms  of  the  glycerin  are  replaced  by  an  equivalent  quantity  of  the  acid 
radical,  according  to  the  proportions  employed.  The  resulting  compound 
ethers  are  denoted  by  names  ending  in  in ;  thus : 

C3H5(OH)3      +       HOC2H30     =      C3H5(OH)2OC2H30      +     OH2 
Glycerin.  Acetic  acid.  Mono-acetin. 

C3H5(OH)3      -j-     2HOC2H30    =     C3H5(OH)(OC2H30)2    +     20H2 
Glycerin.  Acetic  acid.  Diacetin. 

C3H5(OH)3      +     8HOC,H,0    =        C3H5(OC2H30)3         -f     30H2 
Glycerin.  Acetic  acid.  Triacetin. 

The  glyceric  ethers  or  glycerides  thus  produced  are,  for  the  most  part, 
oily  liquids  increasing  in  viscidity  as  the  acid  from  which  they  are  formed 
has  a  higher  molecular  weight;  those  formed  from  the  higher  members  of 
the  fatty  acid  series,  Cn  H2n02  (such  as  palmitic  and  stearic  acids),  are  solid 
fats.  Some  of  the  triacid  glycerides,  produced  artificially  in  the  way  just 
mentioned,  are  identical  with  natural  fats  occurring  in  the  bodies  of  plants 
and  animals ;  thus  tristearin  is  identical  with  the  stearin  of  beef  and  mutton 
suet;  triolein  with  the  olein  of  olive  oil,  &c. 

Hydrochloric  and  hydrobromic  acids  act  upon  glycerin  in  the  same  manner 
as  oxygen  acids,  excepting  that  the  reaction  always  stops  at  the  second 
stage  (just  as  in  the  action  of  these  acids  on  the  glycols  it  stops  at  the  first 
stage).  The  ethers  thus  formed  are  called  chlorhydrins  and  bromhydrins,  &c., 
e.  <?•  : 

C2H5(OH)3     +     HC1     =     03H5(OH)2C1    +     OH2 
Glycerin.  Chlorhydrin. 

C3H6(OH),    -f    2HC1  =     C3H5(OH)C12    +     20H2 
Glycerin.  Dichlorhydrin. 

Hydriodic  acid  acts  somewhat  differently,  producing  an  ether,  C6H,,I08, 
which  may  be  regarded  as  a  double  molecule  of  glycerin,  having  four  equiv- 
alents of  hydroxyl  replaced  by  two  atoms  of  oxygen,  and  a  fifth  by  iodine, 
C6H1002(OH)I. 

The  chlorides  and  bromides  of  phosphorus  act  upon  glycerin  in  the  same 
manner  as  hydrochloric  and  hydrobromic  acid,  but  their  action  goes  on  to 
the  third  stage,  producing  trichlorhydrin  or  propenyl  chloride  and  the  cor- 
responding bromine  compound : 

C3H5(OH)C12    +     PC15    =    PC130     -f     HC1    -f     C3H5C13 
Dichlorhydrin.  Trichlor- 

hydrin. 

Iodide  of  phosphorus  acts  on  glycerin  in  a  totally  different  manner,  yield- 
ing iodopropene  or  allyl  iodide,  C3H5I  (p.  544). 


GLYCEKIN.  569 

GLYCIDE.  —  When  dichlorhydrin  is  treated  with  potash,  it  gives  up  a 
molecule  of  hydrochloric  acid,  and  is  converted  into  a  compound  called 
epichlorhydrin  : 

C3H5OHC12    —    HC1    =    C3H3OC1 
Dichlorhydrin.  Epichlor- 

hydrin. 

This  compound  may  be  regarded  as  the  hydrochloric  ether  of  an  alcohol, 
C3H50(OH),  called  glycide,  formed  from  glycerin  by  abstraction  of  OH2. 
Dibromhydrin,  C3H5(OH)Br2,  treated  in  the  same  manner,  yields  epibrom- 
hydrin,  or  the  hydrobromic  ether  of  glycide,  C3H5OBr.  Epichlorhydrin 
heated  with  dry  potassium  iodide  is  converted  into  epi-iodhydrin,  C3H5OI  : 

C3H5OC1     -f     KI    =     KC1    +     C3H5OI. 

These  glycidic  ethers  are  easily  reconverted  into  bodies  of  the  glycerin 
type.  Thus  epichlorhydrin  combines  with  acetic  acid,  forming  glyceric 
acetochlorhydrin  : 


(C,H6)'"C10     -f     HOC^p    =    (C3H5)'"C1(OH)(OC2H30)  ; 
Epichlor-  Acetic  acid.  Acetochlorhydrin. 

hydrin. 

and  with  alcohol,  in  like  manner,  forming  glyceric  ethylchlorhydrin,  (C3H5)X// 
C1(OH)(OC2H5). 

Epichlorhydrin  unites  directly  with  water,  forming  glyceric  monochlorhy- 
drin,  C3H5(OH)2C1. 

POLYGLYCERINS.  —  Two,  three,  or  more  molecules  of  glycerin  can  unite 
into  a  single  molecule,  with  elimination  of  a  number  of  water  molecules 
less  by  one  than  the  number  of  glycerin  molecules  which  combine  together  ; 
thus: 

2C3H5(OH)3          •    OH2  (C»H6)/"»{(OH)4 

Glycerin.  Diglycerin. 

3C3H5(OH)3  -    20H3  (C3H5)/ 

Glycerin.  Triglycej-in. 

Generally  : 

nC3H5(OH)3  •     (n-l)OH2  =  (C3H5) 


The  product  is  a  polyglycerin  whose  atomicity  (determined  by  the  num- 
ber of  equivalents  of  hydroxyl  contained  in  it)  is  w-f-2. 

The  mode  of  preparing  the  polyglycerins  is  similar  to  that  of  the  poly- 
etlienic  alcohols  (p.  561),  and  consists  in  heating  glycerin  with  chlorhydrin, 
whereby  diglycerin  and  hydrochloric  acid  are  formed  : 

C3H5C1(OH)2    +     C3H5(OH)3  =  (C,H6)S0(OH)4    -f     HC1 
Chlorhydrin.  Glycerin.  Diglycerin. 

The  hydrochloric  acid  thus  formed  converts  a  fresh  quantity  of  glycerin 
into  chlorhydrin,  which  then  acts  in  a  similar  manner  on  the  diglycerin 
and  converts  it  into  triglycerin,  and  in  this  manner  the  process  is  con- 
tinued. The  polyglycerins  may  then  be  separated  by  fractional  distilla- 
tion. Their  properties  are  but  little  known. 

Quintenyl  Alcohol,  or  Amyl  Glycerin,  C5H1203=(C6H9)'"(OH)3.—  This 
compound  is  formed  from  bromoquintene  dibromide,  C-H9Br  .  Br2,  or  quin- 
tonyl  bromide,  (1-II9Br3,  by  the  series  of  processes  represented  in  the  fol- 
lowing »'<|nations: 

48* 


570  TRIATOMIC   ALCOHOLS   AND    ETHERS. 

C5H9Br3  +  2AgOC2H30   =   2AgBr   +  (CBHB)'"{  (OCB 

Quintenyl  Silver  Silver  Quintenyl  diaceto- 

bromide.  acetate.  bromide.  bromhydrin. 


(C6H9)'"{  (OC^3°)2  _|_  2KOH  =  2KOC2H30  -f  C6H9'"  J 

Quintenyl  diaceto-        Potassium     Potassium  Quintenyl 

bromhydrin.  hydrate.        acetate.  bromhydrin. 

(<W"{(B?)a    +     KOH     =      KBr  +  (C.H,)///(OH)8 

Quintenyl  Quintenyl 

bromhydrin.  alcohol. 

Quintenyl  alcohol  is  a  thick  colorless  liquid,  having  a  sweet  aromatic 
taste,  and  soluble  in  water.* 

Triatomic  Phenols. 

There  are  three  compounds  represented  by  the  formula  C6H603,  and 
exhibiting  a  certain  relationship  to  the  phenols  ;  these  are  : 

1.  Pyrogallol,  or  Pyrogallic  acid,  produced  by  the  action  of  heat  on  gallic 
(dioxysalicylic)  acid: 

C7H605        =        C02        +        C6H603; 
Gallic  Pyrogallic 

acid.  acid. 

also,  together  with  gallic  acid,  by  the  action  of  hot  caustic  potash  on  di- 
iodo  salicylic  acid,  C7H4I203.  It  is  conveniently  prepared  by  heating  a 
dried  aqueous  extract  of  gall-nuts  to  180°-185°  C.  (356°-365°  F.)  in  an 
iron  pot  covered  with  a  paper  cap.  It  then  sublimes  and  condenses  on  the 
cap  in  long  flattened  prisms. 

Pyrogallic  acid  is  soluble  in  water,  alcohol,  and  ether;  it  melts  at  115° 
C.  (239°  F.),  boils  at  210°  C.  (410°  F.),  and  decomposes  at  250°  C.  (482° 
F.),  giving  off  water  and  leaving  a  residue  of  metagallic  acid,  C6H402.  It 
dissolves  in  caustic  potash  or  soda,  forming  a  solution  which  quickly  ab- 
sorbs oxygen  from  the  air,  and  turns  black:  this  solution  forms  a  very 
convenient  reagent  for  the  eudiometric  analysis  of  air  (p.  155).  With 
solutions  of  pure  ferrous  salts  it  produces  a  fine  blue  color,  but  the  smallest 
trace  of  ferric  salt  changes  the  tint  to  green.  With  bromine,  pyrogallic 
acid  forms  a  substitution-product  containing  C6H3Br303. 

2.  Phloroglucin.  —  Phlorizin,  or  phloridzin,  a  crystalline  substance,  exist- 
ing ready-formed  in  the  root-bark  of  the   apple,  pear,  plum,  and  cherry- 
trees,  is  resolved  by  boiling  with   dilute   acids  into   glucose,  and  another 
crystalline  substance,  phloretin: 

C2IH24010        +        OH2        =        C6H1206        +        C15H140; 
Phlorizin.  Glucose.  Phloretin. 

and  phloretin,  treated  with  aqueous  potash,  is  resolved  into  phloretic  acid, 
and  phloroglucin: 

C15H1405        +        OH2        =        C9H1003        +        C6H603 
Phloretin.  Phloretic  Phloro- 

acid.  glucin. 

Phloroglucin  is  a  neutral  crystalline  substance,  having  a  very  sweet 
taste,  soluble  in  water,  alcohol,  and  ether.  With  bromine  it  forms  the  com- 

*  Bauer,  Zeitsclmft  fiir  Chem.  u.  Pharm.  1861,  p.  673. 


TETRATOMIC    ALCOHOLS    AND    ETHERS.  571 

pound  C6H3Br303;  with  nitric  acid,  C6H5(N02)03;  with  ammonia,  a  base 
called  pkloraininc,  C6II5(NII2)O2;  with  acetyl  chloride  and  benzoyl  chloride,  it 
yields  the  compounds  C6H6(C2H30)03,  and  C6H6(C7H50)03,  both  of  which 
are  crystalline. 

3.  Frangulin. — This  is  a  yellow  cry stalliz able  substance,  contained  in 
the  bark  of  the  berry-bearing  alder  (Rhamnus  frangula).  It  is  insoluble  in 
water,  slightly  soluble  in  warm  alcohol  and  ether,  soluble  in  fixed  oils, 
benzene,  and  oil  of  turpentine.  Fuming  nitric  acid  dissolves  it,  forming 
oxalic  acid,  and  an  acid  called  nitrofrangulic  acid,  said  to  contain  O^I^NgO^. 


TETRATOMIC  ALCOHOLS  AND  ETHERS. 

The  only  tetratomic  alcohols  at  present,  known  are  erythrite,  C4H1004, 
and  propylphycite,  C3H804. 

Erythrite,  C4H1004=(C4H6)iT(OH)4,  also  called  Erythromannite,  Erythro- 
glucin,  and  Phycite,  is  the  tetratomic  alcohol  corresponding  to  quartyl  alco- 
hol, C4H100,  and  quartyl  glycol,  C4H,002;  the  corresponding  glycerin  is 
not  known. 

Erythrite  is  a  saccharine  substance,  existing  ready-formed  in  Protococcus 
vulgaris.  It  was  originally  discovered  by  Dr.  Stenhouse  among  the  pro- 
ducts of  decomposition  of  erythric  acid.*  It  crystallizes  in  large  trans- 
parent prisms,  is  readily  soluble  in  water,  sparingly  soluble  in  alcohol, 
insoluble  in  ether ;  not  fermentable.  Heated  with  hydriodic  acid,  it  yields 
secondary  quartyl  iodide,  C4H9I  (p.  534) : 

C4H,004        H-        7HI        =        C4H9I        -{-        40H2        -f        3I2. 

Heated  with  oxygen  acids,  it  forms  compound  ethers,  in  the  manner  of  alco- 
hols in  general;  thus,  with  benzoic  acid,  C7H602,  or  HOC7H50,  it  forms  a 
dibenzoate,  (C4H6)iT(OH)2(OC7H50)2,  and  a  hexbenzoate,  (C4H6)iv(OC7H50)4. 
2C7H602,  consisting  of  neutral  benzoyl-erythrite  united  with  two  molecules 
of  benzoic  acid. 

Propylphycite,  C3H804—  (C3H4)iT(OH)4.  —  This  alcohol  is  obtained  synthet- 
ically by  the  following  series  of  processes:  1.  Epichlorhydrin  which 
combines  with  hypochlorous  acid,  forming  the  dichlorhydrin  of  propyl- 
phycite : 

C3H5OC1  -f  C10H  =  (C3H4)iTCl2(OH)2 

Epichlor-  Hypo-  Dichlorhydrin  of 

hydrin.  chlorous  acid.  propylphycite. 

2.  This  dichlorhydrin,  treated  with  silver  acetate,  is  converted  into  the 
corresponding  diacetin,  (C3H4)iT(OC2H30)2(OH)2.  —  3.  The  diacetin,  heated 
with  aqueous  potash,  yields  the  tetratomic  alcohol. 

Propylphycite  is  a  colorless,  solid,  amorphous  mass,  which  deliquesces 
in  the  air  to  a  glutinous  liquid.  It  has  a  sweetish  taste,  dissolves  easily  in 
alcohol,  and  resembles  erythrite  in  its  chemical  relations.  With  fuming 
nitric  acid,  it  forms  nitropropylphycite,  C3H7(N02)04. 

Carbon  tetrachloride,  CC14,  may  be  regarded  as  a  tetratomic  ether;  the 
corresponding  alcohol,  C(OH)4,  is  theoretically  possible,  but  is  not  actually 
known. 

*  See  the  chapter  on  coloring  matters. 


572  ALCOHOLS   AND   ETHERS. 


PENTATOMIC  ALCOHOLS. 

Finite  and  guercite,  two  saccharine  substances  having  the  composition 
C6H,205,  probably  belong  to  this  class  of  bodies,  inasmuch  as  they  produce 
ethers  when  treated  with  acids,  and  the  atomicity  of  an  alcohol  —  that  is  to 
say,  the  number  of  replaceable  hydrogen-atoms  which  it  contains —  is  equal 
to  the  number  of  oxygen-atoms  in  its  molecule  ;  such  indeed  is  the  case  with 
all  the  alcohols  described  in  the  preceding  pages. 

Finite  is  contained  in  the  sap  of  a  Californian  pine  (Finns  Lambertiana), 
and  is  deposited  from  the  aqueous  extract  of  the  hardened  juice,  in  hard 
white  crystalline  nodules,  as  sweet  as  sugar-candy,  very  soluble  in  water, 
nearly  insoluble  in  alcohol.  It  turns  the  plane  of  polarization  of  a  luminous 
ray  to  the  right;  is  not  fermentable.  With  benzoic  acid  it  forms  dibenzo- 
pinite,  C6H7(OC7H50)2(OH)3,  and  tctrabenzopinite,  C6H7(OC7H50)4(OH) ;  and 
similar  compounds  with  stearic  acid. 

Quercite  is  a  saccharine  substance  extracted  from  acorns,  by  treating  the 
aqueous  infusion  with  milk  of  lime  to  remove  tannic  acid,  leaving  the  liquid 
to  ferment  with  yeast  to  remove  fermentable  sugar,  evaporating  the  filtrate 
to  a  syrup,  and  leaving  it  to  crystallize.  It  forms  hard  monoclinic  crystals, 
which  grate  between  the  teeth,  and  are  soluble  in  water  and  in  hot  dilute 
alcohol.  Heated  in  a  sealed  tube  with  benzoic  acid,  it  forms  dibenzoquercite, 
C6H7(OC7H50)2(OH)3. 


HEXATOMIC  ALCOHOLS  AND  ETHERS. 

This  class  of  compounds  includes  most  of  the  saccharine  substances  found 
in  plants,  and  others  produced  from  them  by  artificial  transformation.  Two 
of  the  natural  sugars,  mannite  and  dulcite,  having  the  composition  C6H,406, 
or  (C6H8)vi(OH)6,  are  saturated  hexatomic  alcohols  derived  from  the  satu- 
rated hydrocarbon,  C6HU.  Several  others,  called  glucoses,  contain  C6H,206, 
that  is  to  say,  two  atoms  of  hydrogen  less  than  mannite  and  dulcite,  and 
may  therefore  be  regarded  —  so  far  as  composition  is  concerned  —  as  the 
aldehydes  of  these  alcohols;  moreover,  ordinary  glucose  (grape-sugar)  is 
converted  into  mannite  by  the  action  of  nascent  hydrogen,  just  as  acetic 
aldehyde,  C2H40,  is  converted  into  common  alcohol,  C2H60.  Further,  there 
are  diglucosic  alcohols,  Cl2H22On(=^  2C6H1206  —  OH2),  related  to  the  glucoses 
in  the  same  manner  as  diethenic  alcohol  to  glycol,  or  diglycerin  to  glycerin  : 
the  most  important  of  these  are  cane-sugar  and  milk-sugar  ;  and,  lastly,  there 
are  certain  vegetable  products  —  viz.,  starch,  cellulose,  and  a  few  others,  re- 
presented by  the  formula  C6H1003,  or  multiples  thereof  which  may  be  re- 
garded as  the  oxygen-ethers  or  anhydrides  of  the  glucoses,  or  of  the  diglu- 
cosic alcohols,  inasmuch  as  they  differ  therefrom  by  a  molecule  of  water. 


SATURATED  HEXATOMIC  ALCOHOLS. 

Mannite,  C6H,406  =  (C6H8)  fOH)6.  —  This  is  the  chief  component  of  manna, 
an  exudation  from  a  species  of  ash:  it  is  also  found  in  the  juice  of  certain 
other  plants,  in  several  sea-weeds,  and  in  mushrooms.  It  is  best  prepared 
by  treating  manna  with  boiling  alcohol,  and  filtering  the  solution  while 
hot;  it  then  crystallizes  on  cooling  in  tufts  of  slender  needles.  Mannite 
may  be  produced  artificially  by  treating  a  solution  of  glucose  with  sodium 
amalgam,  the  glucose  then  taking  up  2  atoms  of  hydrogen : 

C6H1206         +         H2        =         C6H1406' 


MANNITE  —  DULCITfc.  573 

The  same  transformation  of  glucose  sometimes  takes  place  under  the  action 
of  certain  ferments. 

Mannite  crystallizes  in  thin  four-sided  prisms,  easily  soluble  in  water  and 
in  hot  alcohol,  insoluble  in  ether.  It  is  slightly  sweet,  has  no  action  on 
polarized  light,  and  is  not  fermentable  except  under  very  unusual  conditions. 

By  oxidation  in  contact  with  platinum-black,  mannite  is  converted  into 
mannitic  acid,  C6H)007,  and  mannitose,  C6H1206,  a  kind  of  sugar  isomeric  with 
glucose.  By  oxidation  with  nitric  acid  it  yields  saccharic  acid,  C6H10,  and 
ultimately  oxalic  acid.  Mannitic  acid  and  saccharic  acid  are  related  to 
mannite  in  the  same  manner  as  glycollic  acid  and  oxalic  acid  to  glycol  ;  the 
relation  between  the  three  compounds  is  shown  by  the  following  formvlse  : 

CH2OII  COOH  COOH 

CHOH  CHOH  CHOH 

CHOH  CHOH  CHOH 

CHOH  CHOH  CHOH 

CHOH  CHOH  CHOH 

CH2OH  CH2OH  COOH 

Mannite.  Mannitic  Saccharic 

acid.  acid. 

By  fuming  nitric  acid,  or  more  easily  by  a  mixture  of  nitric  and  sulphuric 
acids,  mannite  is  converted  into  nitromannite,  C6H8(N02)606,  a  crystalline 
body,  which  explodes  violently  by  percussion  or  when  suddenly  heated, 
and  is  reconverted  into  mannite  by  ammonium  sulphide.  With  sulphuric 
acid  mannite  forms  sulpho-mannitic  acid,  C6H1406  .  3S03. 

Mannite,  treated  with  hl/driodic  acid,  is  converted  into  secondary  hexyl 
iodide,  or  hexylene  hydriodide  (p.  539)  : 


+     60H3    -f     5I2 
Mannite.  Hexyl 

iodide. 

.Mannite,  heated  with  organic  acids,  forms  compound  ethers,  after  the 
manner  of  alcohols  in  general,  the  elements  of  the  mannite  and  the  acid 
uniting  together,  with  elimination  of  one  or  more  molecules  of  water.  The 
resulting  compounds,  called  mannitanides,  bear  a  considerable  resemblance 
to  the  fats  ;  but  their  composition  has  not  been  very  exactly  determined. 

These  ethers,  when  saponified  with  alkalies,  yield,  not  mannite,  but  man- 
nitan,  C6H1205,  a  compound  differing  from  mannite  by  one  molecule  of  water. 
The  same  compound  is  obtained  in  small  quantity  by  heating  mannite  to 
200°  C.  (392°  F.),  and  more  easily  by  prolonged  boiling  of  mannite  with 
strong  hydrochloric  acid.  It  is  a  syrupy  liquid,  which  volatilizes  slowly 
at  140°  C.  (284°  F.),  and  dissolves  easily  in  water  and  in  cold  absolute 
alcohol  :  this  last  property  affords  the  means  of  separating  it  from  mannite. 
When  exposed  to  the  air,  it  slowly  absorbs  water,  and  is  reconverted  into 
mannite  ;  the  change  is  accelerated  by  boiling  with  acids  or  with  alkalies. 

Mannite,  boiled  with  butyric  acid,  gives  up  two  molecules  of  water,  and 
is  converted  into  mannide,  C6111004,  which  is  also  a  syrupy  liquid,  but  differs 
from  manriitan  in  being  much  more  volatile,  evaporating  rapidly  at  140°, 
and  in  being  quickly  reconverted  into  mannite  by  exposure  to  moist  air. 
It  dissolves  easily  in  water  and  in  absolute  alcohol. 

Dulcite,  C6H,406,  also  called  Dulcin,  Dulcose,  and  Mdampyrite.  —  This  sugar, 


574  HEXATOMIC   ALCOHOLS   AND    ETHERS. 

isomeric  with  mannite,  is  obtained  from  a  crystalline  substance,  of  unknown 
origin,  imported  from  Madagascar :  it  is  extracted  therefrom  by  boiling 
with  water,  and  crystallizes  from  the  filtered  solution.  Dulcite  is  likewise 
obtained  from  Melampyrum  nemorosum,  by  mixing  the  aqueous  decoction 
of  the  plant  with  lirne,  concentrating,  adding  hydrochloric  acid  in  slight 
excess,  and  evaporating  a  little ;  it  then  separates  in  crystals  as  the  liquid 
cools. 

Dulcite  is  a  sweet  substance  resembling  mannite  in  most  of  its  properties, 
but  differing  from  it  in  its  crystalline  form,  which  is  that  of  a  monoclinic 
prism,  whereas  the  crystals  of  mannite  are  trimetric ;  and  also  in  its  melt- 
ing point,  dulcite  melting  at  182°  C.  (360°  F.),  mannite  at  165°  C.  (329°  F.), 
and  by  yielding,  when  oxidized  with  nitric  acid,  not  saccharic  acid,  but 
mucic  acid,  which  is  isomeric  therewith.  Heated  with  organic  acids,  it 
forms  ethers  called  dulcitanides,  analogous  to  the  mannitanides,  and  yielding 
by  saponification,  not  dulcite,  but  dulcitan,  C6H,.,05,  which  may  likewise  be 
obtained  by  heating  dulcite  or  by  boiling  it  with  hydrochloric  acid. 

Isodulcitc,  C6H1406,  or  C6H1205.OH2,  a  saccharine  substance  isomeric  with 
mannite  and  dulcite,  is  produced,  according  to  Hlasiwetz  and  Pfaundler,* 
by  the  action  of  dilute  acid  on  quercitrin  (p.  000).  It  forms  large  trans- 
parent, regularly  developed  crystals  resembling  those  of  cane-sugar:  it  is 
sweeter  than  grape-sugar,  not  fermentable,  dissolves  in  2-09  parts  of  water  at 
18°  C.  (64°  F.),  and  easily  in  absolute  alcohol.  The  solutions  turn  the  plane 
of  polarization  to  the  right.  Isodulcite  melts  with  loss  of  water  between 
105°  and  110°  C.  (221°-230°  F.),  is  colored  yellow  or  brown  by  strong  sul- 
phuric acid  and  caustic  alkalies,  and  reduces  cupric  oxide.  By  a  mixture 
of  nitric  and  sulphuric  acids,  it  is  converted  into  a  slightly  explosive  nitro- 
compound,  C6H9(N02)305. 


GLUCOSES,  C6H1206. 

The  sugars  included  in  this  formula  may  be  regarded  as  aldehydes  of  the 
saturated  alcohols,  C6H1406.  Ordinary  glucose  (grape-sugar)  is  converted 
into  mannite  by  the  action  of  nascent  hydrogen  (p.  572),  and,  on  the  other 
hand,  mannite  when  slowly  oxidized  in  contact  with  platinum  black  is 
partly  converted  into  mannitose.  Nevertheless,  the  glucoses  still  exhibit 
the  characteristic  property  of  alcohols,  namely,  that  of  forming  ethers  by 
combination  with  acids  and  elimination  of  water.  The  formula  of  a  glucose 
may  indeed  be  derived  from  that  of  mannite  given  on  page  573,  by  remov- 
ing two  hydrogen-atoms  from  one  of  the  groups,  CH2OH,  the  other  groups 
remaining  as  before;  the  glucoses  may  therefore  be  expected  to  act  as  pen- 
tat  omic  alcohols.  Bodies  thus  constituted  may  be  called  alcoholic  aldehydes. 

The  following  varieties  of  glucose  are  known : 

1.  Ordinary  glucose,  produced  by  hydration  of  starch  under  the  influence 
of  dilute  acids  or  of  diastase,   and  existing  ready-formed,  together  with 
other  kinds  of  sugar,  in  honey  and  various  fruits,  especially  in  grapes,  and 
alone  in  diabetic  urine. 

2.  Maltose,  produced  by  the  limited  action  of  diastase  on  starch,  and 
differing  from  glucose  only  in  its  optical  rotatory  power. 

3.  Levulose,  existing  in  cane-sugar  which  has  been  acted  upon  by  acids, 
and  obtained  pure  by  the  action  of  dilute  acids  upon  a  variety  of  starch 
called  inulin. 

4.  Mannitose,  produced  by  oxidation  of  mannite 

5.  Galactose,  formed  by  the  action  of  acids  on  milk-sugar. 

*  Ann.  Ch.  Pharm.  cxxvii.  362. 


GLUCOSE.  575 

6.  Inosite,  existing  in  muscular  flesh. 

7.  Sorbin,  obtained  from  mountain-ash  berries. 

8.  Eucalyn,  existing,  together  with  another  kind  of  sugar,  in  the  so-called 
Australian  manna. 

The  first  four  of  these  glucoses  exhibit  but  very  slightly  diversity  in  their 
chemical  properties,  differing  chiefly  indeed  in  their  action  on  polarized 
light,  and  a  few  other  physical  properties.  They  all  yield  saccharic  acid 
by  oxidation.  Galactose  differs  from  them  in  yielding  mucic  acid  when 
oxidized.  Inosite,  sorbin,  and  eucalyn  exhibit  still  greater  differences  in 
their  chemical  properties,  especially  in  not  being  fermentable  except  under 
very  peculiar  circumstances,  whereas  the  five  other  glucoses  undergo  vinous 
fermentation  when  placed  under  certain  conditions  in  contact  with  yeast. 

All  the  glucoses,  except  inosite,  are  decomposed  by  boiling  with  aqueous 
alkalies ;  this  property  distinguishes  them  from  rnannite  and  dulcite.  They 
are  not  carbonized  by  strong  sulphuric  acid  at  ordinary  temperatures.  When 
boiled  with  a  solution  of  potassio-cupric  tartrate,  they  throw  down  the 
copper  in  the  form  of  red  cuprous  oxide. 

1.  Ordinary  Glucose,  Dextro-glucose,  Dextrose,  C6H1206 .  OH2.  —  This  va- 
riety of  sugar  is  very  abundantly  diffused  through  the  vegetable  kingdom: 
it  may  be  extracted  in  large  quantity  from  the  juice  of  sweet  grapes  (whence 
it  is  often  called  grape-sugar},  and  also  from  honey,  of  which  it  forms  the 
solid  crystalline  portion,  by  washing  with  cold  alcohol,  which  dissolves  the 
fluid  syrup.  The  appearance  of  this  substance,  to  an  enormous  extent,  in 
the  urine,  is  the  most  characteristic  feature  of  the  disease  called  diabetes. 
It  exists  in  diabetic  urine  unmixed  with  any  other  kind  of  sugar,  and  is 
easily  obtained  by  concentrating  the  liquid  till  it  crystallizes,  washing  the 
crystals  with  cold  alcohol,  dissolving  them  in  water,  and  re-crystallizing. 
It  may  also  be  prepared  from  starch  by  the  action  of  diastase,  a  peculiar 
ferment  existing  in  germinating  barley,  or  by  boiling  with  dilute  sulphuric 
acid.  In  these  reactions  the  starch  takes  up  the  elements  of  water,  and  is 
resolved  into  glucose  and  dextrin,  a  compound  isomeric  with  starch  itself, 
the  transformation  being  exactly  similar  to  the  saponification  of  a  fat  under 
the  influence  of  alkalies: 

3C6H1005        +        OH2        =        CfiH1206        +       2C6H1005 
Starch.  Glucose.  Dextrin. 

.  Glucose  is  always  prepared  from  starch  when  required  in  considerable 
quantity.  The  mode  of  preparation  will  be  described  in  connection  with 
starch.  Cellulose  is  likewise  converted  into  glucose  by  the  action  of  acids 
(p.  000).  Lastly,  glucose  is  produced  by  the  decomposition  of  natural 
glucosides  by  boiling  with  dilute  acids. 

Glucose  is  much  less  sweet  than  cane-sugar,  and  less  soluble  in  water, 
requiring  1£  parts  of  the  cold  liquid  for  solution.  It  separates  from  its 
solutions  in  water  and  alcohol  in  granular  warty  masses,  which  but  seldom 
present  crystalline  faces.  When  pure,  it  is  nearly  white.  In  the  state 
of  solution  it  turns  the  plane  of  polarization  of  a  ray  of  light  to  the  right 
(hence  the  name  dexlro-glucose  and  dextrose] :  its  specific  or  molecular  rota- 
tory power*  is  -|-  56°,  and  does  not  vary  with  the  temperature. 

Glucose  may  be  heated  to  120°  or  even  130°  C.  (248°-256°  F.)  without 

*  The  specific  or  molecular  rotatory  power  of  an  optically  active  substance, 
usually  denoted  by  the  symbol  [«],  is  measured  by  the  number  of  degrees  through 
which  a  column  100  millimetres  or  1  decimetre  thick,  of  a  solution  containing  1 
grain  of  the  pure  substance,  would  rotate  the  plane  of  polarization,  supposing  the 
specific  gravity  of  the  solution  to  be  =  1.  Henqe,  if  the  molecular  rotatory  power 
[a]  is  known,  the  rotation,  a,  of  the  plane  of  polarization  caused  by  a  stratum  1 
decimetre  thick,  of  a  solution  of  sp.  gr.  1,  and  containing  c  grams  of  substance  in 
1  gram  of  solution,  is  expressed  by  the  equation,  <j  —  e  [«].  If,  however,  the  sp. 


576  HEXATOMIC   ALCOHOLS   AND   ETHERS. 

alteration,  but  at  170°  C.  (338°  F.)  it  gives  off  water  and  is  converted  into 
glucosan,  C6H1005,  which,  when  freed  from  caramel  (p.  000}  by  means  of 
charcoal,  and  from  glucose  by  fermentation,  forms  a  colorless  mass,  scarcely 
sweet  to  the  taste,  and  having  somewhat  less  dextro-rotatory  power  than 
glucose.  At  higher  temperatures  glucose  blackens  and  suffers  complete 
decomposition.  Glucose  boiled  for  some  time  with  dilute  sulphuric  or  hydro- 
chloric acid,  is  converted  into  brown  substances  called  ulmin,  ulmic  acid, 
&c.  —  Strong  sulphuric  acid  converts  it  at  ordinary  temperatures  into  sulpho- 
saccharic  acid,  C6H1205S03,  which  forms  a  soluble  barium  salt. 

Lime,  baryta,  and  lead  oxide  dissolve  slowly  in  aqueous  solution  of  glucose, 
and  on  adding  alcohol  to  the  liquid,  compounds  of  these  oxides  with  glucose 
are  precipitated.  The  barium  compound  is  said  to  contain  (C2HI206)2 
(BaO)3.20H2;  the  calcium  compound,  (C,H,aO,),(CaO)8 . 20H, ;  the  lead 
compound,  (C6H,206)vi2(PbO)3(OH)6.  These  compounds  are,  however,  very 
unstable,  being  decomposed  at  the  heat  of  boiling  water.  Glucose  also  com- 
bines with  sodium  chloride,  forming  the  compound  (C6H12Og)2NaC1.0H2. 

Glucose,  boiled  with  a  cupric  salt  in  presence  of  alkalies,  easily  reduces 
the  cupric  oxide  to  cuprous  oxide:  by  this  character  it  is  easily  distin- 
guished from  cane-sugar. 

When  solutions  of  cane-sugar  and  glucose  are  mixed  with  two  separate 
portions  of  solution  of  cupric  sulphate,  and  caustic  potash  added  in  excess 
to  each,  deep-blue  liquids  are  obtained,  which,  on  being  heated,  exhibit 
different  characters ;  the  one  containing  cane-sugar  is  at  first  but  little 
altered;  a  small  quantity  of  red  powder  falls  after  a  time,  but  the  liquid 
long  retains  its  blue  tint:  with  the  glucose,  on  the  other  hand,  the  first  ap- 
plication of  heat  throws  down  a  copious  greenish  precipitate,  which  rapidly 
changes  to  scarlet,  and  eventually  to  dark-red  cuprous  oxide,  leaving  a 
nearly  colorless  solution.  If  the  analyst  have  but  small  quantities  of  ma- 
terial at  his  disposal,  a  mixture  of  cupric  sulphate  and  tartaric  acid,  to 
which  an  excess  of  potash  has  been  added,  may  be  used  with  advantage. 
This  solution,  called  potassio-cupric  tartrate,  is  an  excellent  test  for  distin- 
guishing the  two  varieties  of  sugar,  or  discovering  an  admixture  of  glucose 
with  cane-sugar. 

gr.  is  S,  we  have  a  =  e[a]S.  If  the  thickness  of  the  stratum  is  X  decimetres,  we 
have  finally : 

a   =  £[a]3X. 

If,  then,  the  angle  of  rotation,  «,  has  been  found  by  experiment,  the  quantity 
of  substance,  i,  in  1  gram  of  solution  is  given  by  the  equation, 


If,  on  the  other  hand,  it  is  desired  to  determine  the  specific  rotatory  power,  we 
have  the  equation, 


w=- 


sSX. 

For  example,  by  dissolving  11-347  grams  of  dextro-glucose  in  88-653  grams  of 
water,  a  solution  is  obtained,  having  a  sp.  gr.  of  1*048,  and  producing  in  a  tube  2 
decimetres  long,  a  rotation  of  13-7°.  Hence  the  molecular  rotatory  power  of  dex- 
tro-glucose is  given  by  the  equation, 

[a]  -  ^1 -  57-6. 

0-11347  X  2  X  1-048. 

The  rotation  is  generally  observed  for  the  transition  tint  between  the  blue  and 
the  purple,  in  which  case  the  molecular  rotatory  power  is  denoted  by  the  simple 
symbol  [a]  ;  sometimes,  however,  it  is  observed  for  the  red  ray  •  and  in  this  case 
the  symbol  [a]r  is  employed.  The  rotation  is  distinguished  as  +  or  — ,  according 
as  it  takes  place  to  the  right  or  the  left. 


MALTOSE — LEVULOSE  —  MANNITOSE.  577 

Glucose  mixed  in  dilute  solution  with  yeast  and  exposed  to  a  temperature 
of  21°-26°  C.  (70°-8U°  F.),  easily  undergoes  vinous  fermentation  (p.  516). 

2.  Maltose,  C6H1206. — This  name  is  given  by  Dubrunfaut  to  the  sugar  pro- 
duced by  the  action  of  diastase  upon  starch.  It  has  a  dextro-rotatory  power 
three  times  as  great  as  that  of  ordinary  glucose,  but  resembles  the  latter  in 
all  other  respects,  and  is  converted  into  it  by  boiling  with  dilute  acids.  It 
appears  to  be  merely  a  physical  modification  of  glucose,  the  difference  be- 
tween the  two  depending  on  the  arrangement  of  the  molecules,  not  on  that 
of  the  atoms  within  a  molecule. 

8.  Levulose,  C6H1206. — This  sugar,  distinguished  from  dextro-glucose  by 
turning  the  plane  of  polarization  to  the  left,  occurs,  together  with  dextro- 
glucose,  in  honey,  in  many  fruits,  and  in  other  saccharine  substances. 
The  mixture  of  these  two  sugars  in  equivalent  quantities  constitutes  fruit- 
sugar,  or  inverted  sugar,  which  is  itself  levorotatory,  because  the  specific  ro- 
tatory power  of  levulose  is,  at  ordinary  temperatures,  greater  than  that  of 
dextro-glucose. 

Cane-sugar  may  be  inverted,  that  is,  transformed  into  a  mixture  of  equal 
parts  of  dextro-glucose  and  levulose,  by  warming  with  dilute  acids: 

C12H22On    +     OH2    =     C6H1206    +     C6H1206. 

The  same  change  is  brought  about  by  contact  with  yeast,  or  with  pectase, 
the  peculiar  ferment  of  fruits;  and  likewise  takes  place  slowly  when  a  so- 
lution of  cane-sugar  is  left  to  itself. 

To  separate  the  levulose,  the  inverted  sugar  obtained  from  10  grams  of 
cane-sugar  is  mixed  with  6  grams  of  slaked  lime  and  100  grams  of  water, 
whereby  a  solid  calcium-compound  of  levulose  is  formed,  while  the  whole 
of  the  dextro-glucose  remains  in  solution,  and  may  be  separated  from  the 
precipitate  by  pressure.  The  calcium  salt  of  levulose  suspended  in  water 
and  decomposed  by  carbon  dioxide,  yields  a  solution  of  pure  levulose, 
which  may  be  filtered  and  concentrated  by  evaporation.  Levulose  may  be 
at  once  obtained  in  the  pure  state  by  the  action  of  dilute  acids  on  inulin. 

Levulose  is  a  colorless  uncrystallizable  syrup,  as  sweet  as  cane-sugar, 
more  soluble  in  alcohol  than  dextro-glucose.  Its  rotatory  power  is  much 
greater  than  that  of  dextro-glucose  at  ordinary  temperatures,  but  dimin- 
ishes as  the  temperature  rises.  For  the  transition  tint,  [a]  =  — 106°  at 
l-f°  C.  (57°  F.) ;  =  —  79-5°  at  52°  C.  (122°  F. ) ,  =  —  53°  at  90°  C.  (194° 
F.).  Now,  the  rotatory  power  of  dextro-glucose  is  the  same  at  all  tem- 
peratures, and  equal  to  -j-56°  ;  consequently  that  of  inverted  sugar,  which 
is  — 25°  at  15°,  diminishes  by  about  one-half  at  52°,  becomes  nothing  at 
90°,  and  changes  sign  above  that  temperature. 

Levulose  exhibits,  for  the  most  part,  the  same  chemical  reactions  as  dex- 
tro-glucose, but  is  more  easily  altered  by  heat  or  by  acids,  and  on  the  con- 
trary offers  greater  resistance  to  the  action  of  alkalies  or  of  ferments. 

Levolasan,  C6H1005,  the  oxygen-ether  or  anhydride  of  levulose,  is  pro- 
duced, together  with  dextro-glucose,  by  melting  cane-sugar  for  some  time 
at  160° C.  (32°  F.): 

The  glucose  may  be  removed  from  the  liquid  by  fermentation,  and  the 
levolusan,  which  is  unfermentable,  may  be  obtained  by  evaporation  as  an 
uncrystallizable  syrup.  By  boiling  with  water  or  dilute  acids,  it  is  con- 
verted into  a  fermentable  levorotatory  sugar,  probably  levulose. 

4.  Mannitose,  fgll^Og — This  is  the  sugar  produced,  together  with  man- 
nitic  acid,  by  the  oxidation  of  mannite  in  contact  with  platinum  black.      It 
may  be  separated  by  saturating  the  liquid  with  lime,  precipitating  the  cal- 
49 


578  HEXATOMIC   ALCOHOLS   AND   ETHERS. 

ciura  mannitate  with  alcohol,  evaporating  the  filtrate  to  a  syrup,  adding 
alcohol,  again  filtering,  and  evaporating  to  dryness. 

Mannitose  is  syrupy,  uncrystallizable,  fermentable,  inactive  to  polarized 
light,  and  resembles  the  other  glucoses  in  its  chemical  reaction. 

5.  Galactose,  C6H1206,  is  produced  by  boiling  milk-sugar  with  dilute  acids. 
It  is  soluble  in  water,  sparingly  soluble  in  cold  alcohol,  crystallizes  more 
readily  than  ordinary  glucose;  has  a  dextro-rotatory  power  of  83-3°;  and 
is  very  easily  fermentable.     It  resembles  dextro-glucose  in  most  of  its  re- 
actions, but  is  distinguished  from  all  the  four  glucoses  above  described  by 
yielding  mucic  instead  of  saccharic  acid,  when  oxidized  by  nitric  acid. 

6.  Inosite,  or  Phaseomannite,  C6H1206,  is  a  variety  of  glucose  occurring 
in  the  muscular  substance  of  the  heart  and  other  organs  of  the  animal  body, 
also  in  green  kidney-beans,  the  unripe  fruit  of  Phaseolus  vulgaris,  and  in 
many  other  plants.     It  forms  prismatic  crystals,  resembling  gypsum,  solu- 
ble in  water,  but  insoluble  in  alcohol  and  ether.     It  may  be  boiled  with 
strong  aqueous  potash  or  baryta  without  alteration  or  coloration.     If  this 
sugar  be  evaporated  with  nitric  acid  nearly  to  dryness,  the  residue  mixed 
with  a  little  ammonia  and  calcium  chloride  and  again  evaporated,  a  beau- 
tiful and  characteristic  rose  tint  is  produced. 

Inosite  does  not  ferment  with  yeast,  but  in  contact  with  cheese,  flesh, 
or  decaying  membrane  and  chalk,  it  undergoes  lactous  fermentation,  pro- 
ducing lactic,  butyric,  and  carbonic  acids. 

7.  Sorbin,  or  Sorbite,  C6H1206,  is  a  crystallizable  sugar  existing  in  the  juice 
of  ripe  mountain-ash  berries  (Sorbus  aucuparia).     The  juice,  when  allowed 
to  stand  for  some  time  in  open  vessels,  deposits  a  brown  crystalline  matter, 
which  may  be  obtained  in  transparent  colorless  crystals  belonging  to  the 
trimetric  system.     This  substance  is  almost  insoluble  in  alcohol,  but  easily 
soluble  in  water,  to  which  it  imparts  an    exceedingly  sweet  taste.     A  solu- 
tion of  sorbin,  mixed  with  ammonia  and  lead  acetate,  yields  a  white  floccu- 
lent  precipitate,  containing  C6H4Pb//06.     With  sodium  chloride  it  forms  a 
compound  which  crystallizes  in  cubes. 

Sorbin  is  converted  by  hot  nitric  acid  into  oxalic  acid.  It  does  not  fer- 
ment with  yeast,  but  in  contact  with  cheese  and  chalk,  at  40°,  it  undergoes 
lactous  fermentation,  yielding  a  large  quantity  of  lactic  acid,  together  with 
alcohol  and  butyric  acid. 

8.  Eucalyn,  C6H1206,  is  an  unfermentable  sugar,  separated  in  the  fermen- 
tation of  melitose   (the  sugar  of  the  Eucalyptus  of  Tasmania),   in  conse- 
quence of  the  destruction  of  a  fermentable  kind  of  sugar  which,  in  combi- 
nation with  eucalyn,  constitutes  melitose : 

C12H220H    +     OH2  =  2C02    +     2C2H60     -f     C6H1206 
Melitose.  Alcohol.  Eucalyn. 

On  evaporating  the  liquid,  the  eucalyn  remains  as  an  uncrystallizable 
syrup,  having  a  specific  rotatory  power  of  -f-  50°  nearly.  It  is  not  ren- 
dered fermentable  by  the  action  of  sulphuric  acid. 


GLUCOSIDES. 


When  ordinary  glucose  is  heated  to  100°-120°  for  fifty  or  sixty  hours 
with  acetic,  butyric,  stearic,  benzoic,  and  other  organic  acids,  the  two 
unite,  with  elimination  of  water,  and  compound  ethers  called  glucosides 


GLUCOSIDES.  579 

are  formed,  analogous  to  the  mannitanides.  A  number  of  these  artificial 
glucosides  have  been  prepared  by  Berthelot,  who  regards  them  as  deriva- 
tives of  glucosan,  C6H1005,  because  when  heated  with  alkalies  they  yield 
glucosan,  not  glucose.  Thus,  there  is  a  glucoso-butyric  ether  to  which 
Berthelot  assigns  the  formula  C6H8(C4H70)205,  and  an  acetic  ether,  which 
he  regards  as  hexaceto-glucosan,  C6H4(C2H30)606;  but  they  are  merely  oily 
liquids,  which  are  very  difficult  to  obtain  pure,  and  therefore  their  analyses 
are  not  much  to  be  depended  on. 

A  considerable  number  of  bodies  of  similar  constitution  exist  ready- 
formed  in  plants,  many  of  them  constituting  the  bitter  principles  of  the 
vegetable  kingdom.  None  of  these  natural  glucosides  have  been  produced 
artificially,  but  they  are  all  resolved  by  boiling  with  dilute  acids  into  glu- 
cose and  some  other  compound.  We  shall  describe  some  of  the  most  im- 
portant of  these  bodies. 

AESCULIN,  C21H,,4Oj3,  is  a  crystalline  fluorescent  substance  obtained  from 
the  bark  of  the  horse-chestnut  and  other  trees  of  the  genera  Aesculus  and 
Pavia.  It  has  a  bitter  taste,  is  slightly  soluble  in  water  and  alcohol,  more 
soluble  in  the  same  liquids  at  the  boiling  heat,  nearly  insoluble  in  ether. 
It  is  colored  red  by  chlorine.  By  boiling  with  hydrochloric  or  dilute  sul- 
phuric acid,  it  is  resolved  into  glucose  and  a  bitter  crystalline  substance 
called  sesculetin  : 


c21H24Oi3   4- 

Aesculiu.  Glucose.  JEsculetin. 

The  aqueous  solution  of  aesculin  is  highly  fluorescent,*  the  reflected 
light  being  of  a  sky-blue  color.  Nearly  the  same  fluorescent  tint  is  exhi- 
bited by  an  infusion  of  horse-chestnut  bark.  The  color  of  the  latter  is, 
however,  slightly  modified  by  the  presence  of  another  substance,  paviin, 
which  exhibits  a  blue-green  fluorescence:  it  may  be  separated  from  aescu- 
lin by  its  greater  solubility  in  ether.  Aesculin  and  paviin  appear  to  exist 
together  in  the  barks  of  all  species  of  Aesculus  and  Pavia,  —  aesculin  being 
more  abundant  in  the  former,  and  paviin  in  the  latter. 

AMYODALIN,  C20H27NOU  .  30H2,  is  a  crystalline  body  existing  in  bitter 
almonds,  the  leaves  of  the  cherry-laurel  (Cerasus  laurocerasus},  and  many 
other  plants  which  by  distillation  yield  hydrocyanic  acid  and  bitter-almond 
oil,.  These  compounds  do  not  exist  ready-formed  in  the  plants,  but  are 
produced  by  the  decomposition  of  amygdalin  under  the  influence  of  emul- 
sin  or  synaptase,  a  nitrogenized  ferment  likewise  existing  in  the  plant. 
The  decomposition  is  expressed  by  the  equation  — 

C2oH27N°n     +    20II2    =    C7H60  +     CNH     +     2C6H1206 
Amygdalin.                                Bitter-          Hydro-          Glucose. 
almond  cyanic 

oil.  acid. 

To  prepare  amygdalin,  the  paste  of  bitter-almonds,  from  which  the 
fixed  oil  has  been  expressed,  is  exhausted  with  boiling  alcohol,  which 
coagulates  the  synaptase,  renders  it  inactive,  and  dissolves  out  the  amygda- 
lin. The  alcoholic  liquid  is  distilled  in  a  water-bath,  and  the  syrupy  resi- 
due is  diluted  with  water,  mixed  with  a  little  yeast,  and  set  in  a  warm 
place  to  ferment:  a  portion  of  sugar,  present  in  the  almonds,  is  thus 
destroyed.  The  filtered  liquid  is  then  evaporated  to  a  syrup  in  a  water- 
bath,  and  mixed  with  alcohol,  which  throws  down  the  amygdalin  as  a  white 
crystalline  powder;  the  latter  is  collected  on  a  cloth  filter,  pressed,  redis- 
solved  in  boiling  alcohol,  and  left  to  cool.  It  separates  in  small  crystal- 

*  See  LIGHT,  p.  91. 


580  HEXATOMIC    ALCOHOLS   AND   ETHERS. 

line  plates  of  pearly  whiteness,  which  are  inodorous  and  nearly  tasteless  : 
it  is  decomposed  by  heat,  leaving  a  bulky  coal,  and  diffusing  the  odor  of 
the  hawthorn.  In  water,  both  hot  and  cold,  amygdalin  is  nearly  insoluble; 
a  hot  saturated  solution  deposits,  on  cooling,  brilliant  prismatic  crystals, 
which  contain  water.  In  cold  alcohol  it  dissolves  with  great  difficulty. 
Heated  with  dilute  nitric  acid,  or  a  mixture  of  dilute  sulphuric  acid  and 
manganese  dioxide,  it  is  resolved  into  ammonia,  bitter-almond  oil,  bcnzoic 
acid,  formic  acid,  and  carbonic  acid;  with  potassium  permanganate,  it 
yields  a  mixture  of  potassium  cyanate  and  benzoate. 

Synaptase  has  never  been  obtained  in  a  state  of  purity:  it  is  described 
as  a  yellowish-white,  opaque,  brittle  mass,  very  soluble  in  water,  and  co- 
agulable,  like  albumin,  by  heat,  in  which  case  it  loses  its  specific  property. 
In  solution  it  very  soon  becomes  turbid,  and  putrefies.  The  decomposition 
of  amygdalin  under  the  influence  of  this  body  may  be  exhibited  by  dis- 
solving a  portion  in  a  large  quantity  of  water,  and  adding  a  little  emulsion 
of  sweet  almonds  :  the  odor  of  the  volatile  oil  immediately  becomes  ap- 
parent, and  the  liquor,  on  distillation,  yields  hydrocyanic  acid. 

CHITIN,  C9HI5N06,  is  the  substance  which  forms  the  elytra  and  integu- 
ments of  insects  and  the  carapaces  of  crustaceans.  It  is  best  prepared  by 
boiling  the  wing-cases  of  cockchafers  with  water,  alcohol,  ether,  acetic 
acid,  and  alkalies  in  succession,  as  long  as  anything  is  dissolved  out  by 
each.  According  to  Stadeler,*  it  is  resolved  by  boiling  with  dilute  acids 
into  glucose  and  lactamide  : 

C9H]5N06     -f     20H2    =     C6H1206    +     C3H7N02 
Chitin.  Glucose.         Lactamide. 

GALLOTANNIC  ACID,  C27H22On,  the  acid  contained  in  the  gall-nuts  of 
Quercus  infectoria  and  other  species  of  oaks,  and  of  certain  species  of 
sumach,  is  a  glucoside,  resolved  by  the  action  of  acids  into  glucose  and 
gallic  acid: 

C»HM0W     +     40H2     =     C6H1206    +     3C7H605 
Gallotannic  Glucose.         Gallic  acid. 

acid. 

It  will  be  described  in  connection  with  gallic  acid.  (See  the  chapter  on 
ACIDS.) 

GLYCYRRHIZIN,  C24H3609;  LIQUORICE-SUGAR.  —  The  root  of  the  common 
liquorice  yields  a  large  quantity  of  a  peculiar  sweet  substance,  which  is 
soluble  in  water,  but  refuses  to  crystallize  :  it  cannot  be  made  to  ferment. 
Glycyrrhizin  forms  difficultly  soluble  compounds  with  acids  ;  it  is  precipitated 
from  its  solution  by  lead,  calcium,  and  barium  salts,  the  precipitate  con- 
sisting of  glycyrrhizin  in  combination  with  the  base.  According  to  Gorup 
Besanez,  glycyrrhizin  when  boiled  with  dilute  acids,  splits  into  a  resinous 
body  called  glycyrretin,  and  glucose. 


+       OH2      =      CJ8H2604      +       C6H1206 
Glycyrrhizin.  Glycyrretin.  Glucose. 

MTRONIC  ACID,  C,0H19NS20,0,  an  acid  existing  as  a  potassium  salt  in  the 
seed  of  black  mustard,  is  resolved  by  the  action  of  myrosin,  an  albuminous 
ferment  likewise  contained  in  the  seeds,  into  volatile  oil  of  mustard  (allyl 
sulphocyanate),  glucose  and  sulphuric  acid: 

C10HJ8KNS2010    =    C3H5CNS  +     C6H1206     +     S04HK 
Potassium                     Allyl  Glucose.  Acid 

myronate.  sulpho-  potassium 

cyanate.  sulphate. 

*  Ann.  Ch.  Pharm.  cxi.  21. 


GLUCOSIDES.  581 

PIILORTZIN,  C21TI24010.20II2. — This  is  a  substance  bearing  a  great  likeness 
to  salicin,  found  in  the  root-bark  of  the  apple  and  cherry-tree,  and  ex- 
tracted by  boiling  alcohol.  It  forms  fine,  colorless,  silky  needles,  soluble^ 
in  1000  parts  of  cold  water,  but  freely  dissolved  by  that  liquid  when  hot: 
it  is  also  soluble  without  difficulty  in  alcohol.  Dilute  acids  convert 
phlorizin  into  glucose  and  a  crystallizable  sweet  substance  called  phloretin : 

C,,H24010      +      OH,      =      C6H1206      +      C15H1405 
Phlorizin.  Glucose.  Phloretin. 

Phlorizin,  fused  with  potash,  yields  phloretic  acid,  C9pj,003,  a  beautifully 
crystalline  acid,  homologous  with  salicylic  and  anisic  acids. 

QUERCITRIN  is  n  crystallizable  yellow  coloring  matter  occurring  in  quercitron 
bark, the  bark  of  Qucrcusinfecloria,  whence  it  is  extracted  by  boiling  with  water. 
Its  compbsition  has  been  variously  stated  ;  indeed  it  is  by  no  means  certain 
that  the  so-called  quercitrins  examined  by  different  chemists  were  really 
identical  substances.  According  to  Hlasiwetz  and  Pfaundler*  it  contains 
C33H30O17,  and  is  resolved  by  boiling  with  dilute  acids  into  another  yellow 
crystalline  body  called  querceli?i,  and  isodulcite  (p.  000): 

C^cAr      +      OH2     =     C27H]8012       -f       C6HI406 
Quercitrin.  Quercetin.  Isodulcite. 

SALICIN,  C,3H1807,  is  a  crystallizable  bitter  substance  contained  in  the 
leaves  and  young  bark  of  the  poplar,  willow,  and  several  other  trees.  It 
may  be  prepared  by  exhausting  the  bark  with  boiling  water,  concentrating 
the  solution  to  a  small  bulk,  digesting  the  liquid  with  powdered  lead  oxide, 
and  then,  after  freeing  the  solution  from  lead  by  a  stream  of  sulphuretted 
hydrogen  gas,  evaporating  till  the  salicin  crystallizes  out  on  cooling.  It  is 
purified  by  treatment  with  animal  charcoal  and  re-crystallization. 

Salicin  forms  small,  white,  silky  needles,  having  an  intensely  bitter  taste, 
but  no  alkaline  reaction.  It  melts  and  decomposes  by  heat,  burning  with 
a  bright  flame,  and  leaving  a  residue  of  charcoal.  It  is  soluble  in  5'G  parts 
of  cold  water,  and  in  a  much  smaller  quantity  when  boiling  hot.  Oil  of 
vitriol  colors  it  deep  red. 

When  distilled  with  a  mixture  of  potassium  bichromate  and  sulphuric 
acid,  it  yields,  among  other  products,  a  yellow,  sweet-scented  oil,  called 
saUci/lol,  having  the  composition,  C7IT602,  and  identical  with  the  volatile 
oil  distilled  from  the  flowers  of  the  Sjpirsea  ulmaria,  or  common  meadow- 
sweet. 

Salicin,  under  the  influence  of  the  emulsin  or  synaptase  of  sweet  almonds, 
is  resolved  into  glucose  and  saligenin: 

C,3HiA     +     OH2    =    C.HW06      +      C7H8H2 
Salicin.  Glucose.  Saligenin. 

Saligenin  forms  colorless,  nacreous  scales,  freely  soluble  in  water,  alco- 
hol, and  ether.  It  melts  at  82°,  and  decomposes  at  a  higher  temperature. 
Dilute  acids  at  boiling  heat  convert  it  into  saliretin,  C7H60,  a  resinous  sub- 
stance differing  from  saligenin  by  the  elements  of  water.  The  same  sub- 
stance is  produced  directly  from  salicin  by  boiling  with  dilute  acids.  Many 
oxidizing  agents,  as  chromic  acid  and  silver  oxide,  convert  saligenin  into 
salicylol ;  even  platinum  black  produces  this  effect.  Its  aqueous  solution 
gives  a  deep  indigo-blue  color  with  ferric  salts. 

Salicin  yields,  with  chlorine,  substitution-products  which  are  decomposed 
by  synaptase  in  the  same  manner  as  salicin  itself,  yielding  chlorosaligenin, 
C7H7C1O2,  and  dichlorosaligenin,  C7H6C1202.  Dilute  nitric  acid  converts  sali- 

*  Ann.  Ch.  Pharm.  cxxvii.  362. 
49* 


582  HEXATOM1C    ALCOHOLS   AND   ETHERS. 

cin  into  helicin,  helicoi'din,  and  anilotic  acid.  With  strong  nitric  acid,  at  a 
high  temperature,  nitrosalicylic  acid,  C7H5(N02)03,  is  produced. 

POPULIN,  C20H2208,  is  a  substance  resembling  salicin  in  appearance  and 
solubility,  but  having  a  penetrating  sweet  taste.  It  is  found  accompanying 
salicin  in  the  bark  and  leaves  of  the  aspen.  It  has  the  composition  of  ben- 
zoyl-salicin,  C13H17(C7H50)07,  and  when  heated  with  dilute  acids  is  resolved 
into  benzoic  acid,  and  the  products  of  decomposition  of  salicin,  namely, 
saliretin  and  glucose : 

C13H17(C7H60)07    +    OH2    ==    C7H602    +     C7H60     +     C6H1206 
Populin.  Benzoic         Saliretin.          Glucose. 

acid. 

With  potassium  bichromate  and  sulphuric  acid,  populin  yields  a  consider- 
able quantity  of  salicylol. 

HELICIN,  C,3H,607,  is  a  white,  crystalline,  slightly  bitter  substance,  pro- 
duced by  the  action  of  very  dilute  nitric  acid  upon  salicin: 

C13H1807    +     0     =     OH,    +     CI3H1(|0T 
Salicin.  Helicin. 

It,  is  slightly  soluble  in  cold,  freely  soluble  in  boiling  water,  and  is  resolved 
by  the  action  of  synaptase,  or  of  acids  or  alkalies  at  the  boiling  heat,  into 
glucose  and  salicylol: 

C13H1?07     +     OH3    =    C6H1206       +      C7H602 
Helicin.  Glucose.  Salicylol. 

Benzohelicin,  C24H2008,  or  C13H,5(C7H50)07,  produced  by  the  action  of 
dilute  nitric  acid  on  benzo-salicin,  is  resolved  in  like  manner  into  benzoic 
acid,  salicylol,  and  glucose : 

CAA    +     20H2    =    C7H602    +     C7H602     +      C6H1206 
Benzo-  Benzoic          Salicylol.  Glucose. 

helicin.  acid. 

SOLANINE  is  a  crystalline  base  occurring  in  various  plants  of  the  solana- 
ceous  order,  especially  in  the  flower-stalks  and  berries  of  the  woody  night- 
shade (Solanum  dulcamara),  and  in  the  shoots  or  germs  thrown  out  by  po- 
tatoes kept  in  cellars  during  the  winter;  it  maybe  extracted  from  these 
shoots  by  water  containing  a  little  sulphuric  acid.  It  probably  contains 
C43H71N016,  and  is  resolved  by  boiling  with  dilute  acids  into  glucose  and 
solanidine,  which  is  also  a  basic  compound  crystallizing  from  alcohol  in  long 
needles : 

C43H71N016     +      30H2     =     3C6H1206      +       C26H41NO 
Solanine.  Glucose.  Solanidine. 

THUJIN,  C20H22012,  is  aglucoside  occurring  in  the  green  parts  of  the  Amer- 
ican Arbor  Vitte  (Thuja  occidentalis).  It  forms  shining,  lemon-yellow, 
microscopic  crystals,  having  an  astringent  taste,  and  soluble  in  alcohol. 
When  heated  in  alcoholic  solution  with  hydrochloric  or  dilute  sulphuric 
acid,  it  is  resolved  into  glucose  and  thujetin,  C28H28016 : 

20^0,2    +     40H2    =    2C6H1206    +     C28H28016. 

When  heated  for  a  short  time  only  with  hydrochloric  acid,  it  yields  also 
another  substance  called  thujenin,  containing  C28H24014,  or  two  molecules  of 
water  less  than  thujetin.  Thujin  dissolves  in  baryta  water,  forming  a 
yellow  solution,  which  when  heated  deposits  an  orange-yellow  precipitate 
of  thujetic  acid,  C28H22013,  while  glucose  remains  dissolved : 

2C20H22012    +     OH2    =     2C6H1206    +     C28H22013. 
All  these  compounds  are  crystalline. 


POLYGLUCOSIC   ALCOHOLS.  583 

XANTIIOIUIAMNIN,  C23H28014,  a  crystallizable  yellow  coloring  matter  ob- 
tained from  Persian  or  Turkey  berries,  the  seeds  of  several  species  of 
Jthamnus,  is  resolved  by  boiling  with  dilute  acids,  into  glucose  and  rham- 
nctin,  CUH1005,  which  is  also  a  yellow  crystalline  substance : 

CjH^On    +     30H2    =    2C6H1206     If     CUHM0, 

According  to  some  authorities,  xanthorhamnin  is  identical  with  quercitrin, 
and  rhamnetin  with  quercetin. 

There  are  a  few  compounds  which,  when  treated  with  dilute  acids,  split 
up  similarly  to  the  glucosides,  but  yield  saccharine  substances  differing 
in  composition  from  glucose.  Thus  phloretin,  as  already  observed,  is  re- 
solved into  phloretic  acid,  and  phloroglucin,  C6H603  (p.  570),  which  differs 
from  glucose  by  30H2.  Quercitrin  yields  quercetin  and  isodulcite,  C6FTU06, 
containing  two  atoms  of  hydrogen  more  than  glucose;  and  indican,  C.^Hgj 
N017,  yields  indiglucin,  C6H1006,  containing  two  atoms  of  hydrogen  less  than 
glucose. 

INDICAN  is  a  colorless  substance  existing  in  woad  (Isatis  tinctoria),  and 
probably  in  most  other  plants  which  yield  indigo-blue.  It  likewise  occurs 
in  human  urine,  both  healthy  and  diseased,  and  when  present  in  considei*- 
able  quantity,  causes  the  urine,  after  spontaneous  fermentation  or  addition 
of  acids,  to  deposit  sometimes  indigo-blue,  sometimes  a  brown  substance 
isomeric  with  it,  called  indirubin. 

Indican  is  decomposed  by  dilute  acids  into  indigo-blue  (or  its  isomer, 
indirubin)  and  indiglucin: 

CANO!,        +        20H2        =        C8H3NO        +        8CeHI006 
Indican.  Indigo-  Indiglucin. 

blue. 

In  contact  with  aqueous  soda  or  baryta  it  is  resolved  into  indiglucin,  and 
a  yellow  uncrystallizable  substance  called  indicanin : 

C26H31NOI7        +        OH2        =        C6H100?        +        C20H23NO]2; 
Indican.  Indiglucin.  Indicanin. 

and  indicanin,  by  boiling  with  dilute  acids,  is  further  resolved  into  indi- 
glucin and  other  products. 

Indiglucin,  C6H1006,  is  a  colorless  or  light-yellow  syrup,  having  a  slightly 
sweet  taste,  soluble  in  water  and  alcohol,  but  precipitated  from  the  alco- 
holic solution  by  ether.  It  is  not  fermentable,  but  turns  acid  by  prolonged 
contact  with  yeast.  It  throws  down  cuprous  oxide  from  an  alkaline  cupric 
solution,  metallic  silver  from  an  ammoniacal  solution  of  the  nitrate,  and 
gold  from  the  trichloride.  With  basic  or  neutral  lead  acetate,  on  addition 
of  ammonia,  it  forms  a  precipitate  containing  C12Hl8Pb//012 .  3Pb//0. 


POLYGLUCOSIC  ALCOHOLS. 

The  compounds  of  this  group,  including  cane-sugar  and  other  bodies  more 
or  less  resembling  it,  may  be  regarded  as  formed  by  the  combination  of 
two  or  more  molecules  of  glucose,  with  elimination  of  a  number  of  mole- 
cules of  water,  less  by  one  than  the  number  of  glucose  molecules  which 
cuter  in  the  combination: 

1><VTT120B    —     TI.,0  =     (VUO,,,  Diglucosic  alcohol. 

rj  I  ..A.'    —     Ufi.,0  =     CI8II3,016,  Triglucosic  alcohol. 

(n-l)H20      ±= 


584:  HEXATOMIC   ALCOHOLS   AND    ETHERS. 

The  only  known  alcohols  of  this  class  are  diglucosic  alcohols,  C12H.220U; 
but  starch,  cellulose,  and  other  plant-constituents  appear  to  be  oxygen 
ethers,  or  anhydrides,  of  polyglucosic  alcohols  of  higher  orders. 

Cane-sugar  or  Saccharoge,  C12H220U.  —  This  most  useful  substance  is  found 
in  the  juice  of  many  of  the  grasses,  in  the  sap  of  several  forest-trees,  in 
the  root  of  the  beet  and  the  mallow,  and  in  several  other  plants.  Most 
sweet  fruits  contain  cane-sugar,  together  with  inverted  sugar  (p.  577) ; 
some,  as  walnuts,  hazelnuts,  almonds,  coffee-beans,  and  St.  John's-bread 
(the  fruit  of  Ceratonia  siliqua),  contain  only  cane-sugar.  Honey  and  the 
nectars  of  flowers  contain  cane-sugar  together  with  inverted  sugar;  the 
sugar  in  the  nectars  of  cactuses  is  almost  wholly  cane-sugar. 

Sugar  is  extracted  most  easily  and  in  greatest  abundance  from  the  sugar- 
cane (Saccharum  officinarum],  cultivated  for  the  purpose  in  many  tropical 
countries.  The  canes  are  crushed  between  rollers,  and  the  expressed  juice 
is  suffered  to  flow  into  a  large  vessel,  where  it  is  slowly  heated  nearly  to 
its  boiling  point.  A  small  quantity  of  slaked  lime  mixed  with  water  is 
then  added,  which  occasions  the  separation  of  a  coagulum  consisting  chiefly 
of  earthy  phosphates,  waxy  matter,  a  peculiar  albuminous  principle,  and 
mechanical  impurities.  The  clear  liquid  separated  from  the  coagulum  is 
rapidly  evaporated  in  open  pans,  heated  by  a  strong  fire  made  with  the 
crushed  canes  of  the  preceding  year,  which  have  been  dried  in  the  sun, 
and  preserved  for  the  purpose.  When  sufficiently  concentrated,  the  syrup 
is  transferred  to  a  shallow  vessel,  and  left  to  crystallize,  during  which  time 
it  is  frequently  agitated  in  order  to  hasten  the  change  and  hinder  the  forma- 
tion of  large  crystals.  It  is,  lastly,  drained  from  the  dark  uncrystallizable 
syrup,  or  molasses,  and  sent  into  commerce,  under  the  name  of  raw  or  Mus- 
covado sugar.  The  refining  of  this  crude  product  is  effected  by  redissolv- 
ing  it  in  water,  adding  a  quantity  of  albumen  in  the  shape  of  serum  of 
blood  or  white  of  egg,  and  sometimes  a  little  lime-water,  and  heating  the 
whole  to  the  boiling  point:  the  albumen  coagulates,  and  forms  a  kind  of 
network  of  fibres,  which  enclose  and  separate  from  the  liquid  all  mechan- 
ically suspended  impurities.  The  solution  is  decolorized  by  filtration 
through  animal  charcoal,  evaporated  to  the  crystallizing  point,  and  put  into 
conical  earthen  moulds,  where  it  solidifies,  after  some  time,  to  a  confusedly 
crystalline  mass,  which  is  drained,  washed  with  a  little  clean  syrup,  and 
dried  in  a  stove:  the  product  is  ordinary  loaf-sugar.  When  the  crystalliza- 
tion is  allowed  to  take  place  quietly  and  slowly,  sugar-candy  results,  the 
crystals  under  these  circumstances  acquiring  large  volume  and  regular 
form.  The  evaporation  of  the  decolorized  syrup  is  best  conducted  in 
strong  close  boilers  exhausted  of  air;  the  boiling  point  of  the  syrup  is 
reduced  in  consequence  from  110°  C.  (280°  F.)  to  65-5°  C.  (150°  F.),  or 
below,  and  the  injurious  action  of  the  heat  upon  the  sugar  is  in  great 
measure  prevented.  Indeed,  the  production  of  molasses  in  the  rude  colo- 
nial manufacture  is  chiefly  the  result  of  the  high  and  long-continued  heat 
applied  to  the  cane-juice,  and  might  be  almost  entirely  prevented  by  the 
use  of  vacuum-pans,  the  product  of  sugar  being  thereby  greatly  increased 
in  quantity,  and  so  far  improved  in  quality  as  to  become  almost  equal  to 
the  refined  article. 

In  many  parts  of  the  continent  of  Europe,  sugar  is  manufactured  on  a 
large  scale  from  beet-root,  which  contains  about  8  per  cent,  of  that  sub- 
stance. The  process  is  far  more  complicated  and  troublesome  than  that 
just  described,  and  the  raw  product  much  inferior.  When  refined,  how- 
ever, it  is  scarcely  to  be  distinguished  from  the  preceding.  The  inhabit- 
ants of  the  Western  States  of  America  prepare  sugar  in  considerable 
quantity  from  the  sap  of  the  sugar-maple,  Acer  saccharim/m,  which  is  come 
mon  in  those  parts.  The  tree  is  tapped  in  the  spring  by  boring  a  hole  a 


CANE-SUGAR.  585 

little  way  into  the  wood,  and  inserting  a  small  spout  to  convoy  the  liquid 
into  a  vessel  placed  for  its  reception.  This  is  boiled  down  in  an  iron  pot, 
and  furnishes  a  coarse  sugar,  which  is  almost  wholly  employed  for  domes- 
tic purposes,  but  little  finding  its  way  into  commerce. 

Pure  sugar  slowly  separates  from  a  strong  solution  in  large,  transparent, 
colorless  crystals,  having  the  figure  of  a  modified  mono-clinic  prism.  The 
crystals  have  a  specific  gravity  of  1-6,  and  are  unchangeable  in  the  air. 
Sugar  has  a  pure,  sweet  taste,  is  very  soluble  in  water,  requiring  for  solu- 
tion only  one-third  of  its  weight  in  the  cold,  and  is  also  dissolved  by  alco- 
hol, but  less  easily.  When  moderately  heated  it  melts,  and  solidifies  on 
cooling  to  a  glassy  amorphous  mass,  familiar  as  barley-sugar. 

1.  Cane-sugar,  heated  a  little  above  160°  C.  (320°  P.),  is  converted,  with- 
out loss  of  weight,  into  a  mixture  of  dextro-glucose  and  levolusan  (p.  577): 

ClaHBOn      =      C6II1206      +      C6H1005. 

At  a  higher  temperature,  water  is  given  off,  the  dextro-glucose  being 
probably  converted  into  glucosan  (p.  579) :  afterward,  at  about  210°  C. 
(410°  F.),  more  water  goes  off,  and  a  brown  substance  called  caramel  re- 
mains, consisting  of  a  mixture  of  several  compounds,  all  formed  from  sugar 
by  elimination  of  water.  At  a  still  higher  temperature,  an  inflammable 
gaseous  mixture  is  given  off,  consisting  of  carbon  monoxide,  marsh-gas, 
and  carbon  dioxide ;  a  distillate  is  obtained,  consisting  of  brown  oils,  acetic 
acid,  acetone,  and  aldehyde;  and  a  considerable  quantity  of  charcoal  re- 
mains behind.  The  brown  oils  contain  a  small  quantity  of  furfurol,  and  a 
bitter  substance  called  assamar. 

2.  By  prolonged  boiling  with  water,  cane-sugar  is  converted  into  inverted 
sugar.     This  transformation  is  accelerated  by  the  presence  of  acids,  and 
apparently  also  of  certain  salts.     Different  acids  act  with  various  degrees 
of  rapidity — mineral  more  quickly  than  organic  acids,  sulphuric  acid  most 
quickly  of  all.     When  sugar  is  boiled  even  with  very  dilute  acids,  especially 
if  the  boiling  be  long  continued,  a  number  of  brown  amorphous  products 
are  formed,  called  ulmin,  ulmic  acid,*  &c. ;  if  the  air  has  access  to  the  liquid, 
formic  acid  is  likewise  produced.      Concentrated  hydrochloric  acid  decom- 
poses sugar  very  quickly. 

Strong  sulphuric  acid  decomposes  dry  sugar  when  heated,  and  a  concen- 
trated solution,  even  at  ordinary  temperatures,  with  copious  evolution  of 
sulphurous  oxide,  and  formation  of  a  large  quantity  of  black  carbonaceous 
matter.  By  this  reaction  cane-sugar  may  be  distinguished  from  glucose. 

3.  Cane-sugar  is  very  easily  oxidized.     It  reduces  silver-  and  mercury- 
salts  when  heated  with   them,   and   precipitates   gold  from  the  chloride. 
Pure  cupric  hydrate  is  but  slowly  reduced  by  it,  even  at  the  boiling  heat; 
in  presence  of  alkali,  however,  a  blue  solution  is  formed,  and  on  boiling 
the  liquid,  cuprous  oxide  is  slowly  precipitated  (p.  674).     Cane-sugar  takes 
fire  when  triturated  with  8  parts  of  lead  dioxide,  and  forms  with  potassium 
chlorate  a  mixture  which  detonates  on  percussion,  and  burns  vividly  when 
a  drop  of  oil  of  vitriol  is  let  fall  upon  it.     Distilled  with  a  mixture  of  sul- 
phuric acid  and  manganese  dioxide,  it  yields  formic  acid.     Heated  with 
dilute  nitric  acid,  it  yields  saccharic  and  oxalic  acids.      1  part  sugar  mixed 
with  3  parts  nitric  acid,  of  specific  gravity  1-25  to  1  30,  and  heated  to  50° 
C.  (122°  F.),  is  wholly  converted  into  saccharic  acid: 

*  Under  the  names  nlmin  and  ulmic  acid  have  heen  confounded  a  number  of  brown  or  black 
nncrystallizable  Hubs tancee  produced  by  the  action  of  powerful  chemical  agents  upon  snirar, 
lignin,  Ac.,  or  p-nr.rat.-d  by  the  putrefactive  decay  of  vegetable  fibre.  Common  garden  mould, 
for  example,  treated  with  dilute,  boiling  solution  of  caustic  pofa*sa,  yields  a  deep-brown  solu- 
tion, from  which  acids  precipitate  a  flocculcnt,  brown  substance,  having  but  a  slight  degree 
of  solubility  in  water.  This  is  generally  called  iil.niii-  or  lut.>nir.  acid,  and  its  origin  ascribed  to 
the  reaction  of  the  alkali  on  the  ulmin  or  humus  of  the  soil.  It  is  known  that,  these  bodies 
differ  exceedingly  in  composition:  they  arc  too  indefinite  to  admit  of  ready  investigation. 


586  HEXATOMIC   ALCOHOLS   AND   ETHERS. 

C12H22On       +       06       =        2C6H1008       OH2 
Sugar.  Saccharic  acid. 

At  the  boiling  heat,  the  product  consists  chiefly  of  oxalic  acid.  Very 
strong  nitric  acid,  or  a  mixture  of  strong  nitric  and  sulphuric  acids,  con- 
verts sugar  into  nitrosacc/tarose,  probably  C12H18(N02)4Oir  Sugar  is  like- 
wise oxidized  by  chloride  of  lime,  but  the  products  have  not  been  examined. 

4.  Cane-sugar  does  not  turn  brown  when  triturated  with  alkalies,  a 
character  by  which  it  is  distinguished  from  glucose :  it  combines  with 
them,  however,  forming  compounds  called  sucrates.  By  boiling  with  potash- 
lye  it  is  decomposed,  but  much  more  slowly  than  the  glucoses. 

Potassium-  and  Sodium-compounds  of  cane-sugar,  C12H21KOn  and  C]2TI21 
NaOu,  are  formed,  as  gelatinous  precipitates,  on  mixing  an  alcoholic  solu- 
tion of  cane-sugar  with  potash-  or  soda-lye. 

A  barium-compound,  C12H20Ba//On  .  H20,  or  C12H220U  .  Ba//0,  is  obtained, 
as  a  crystalline  precipitate,  on  adding  hydrate  or  sulphide  of  barium  to  an 
aqueous  solution  of  sugar.  It  may  be  crystallized  from  boiling  water,  but 
is  insoluble  in  alcohol. 

Calcium-compounds. — Lime  dissolves  in  sugar-water  much  more  readily 
than  in  pure  water.  The  solution  has  a  bitter  taste,  and  is  completely  but 
slowly  precipitated  by  carbonic  acid.  There  are  three  or  four  of  these 
compounds,  which  may  be  approximately  represented  by  the  following  for- 
mulae : 

1.  C12H22On .  Ca"0.  3. 

2.  2CuHaOu.3Ca"0(?) 

Magnesia  and  lead  oxide  are  also  dissolved  by  sugar-water.  A  crystalline 
lead-compound,  C12H18Pb//2011,  is  precipitated  on  mixing  sugar-water  with 
neutral  lead-acetate  and  ammonia. 

Sugar  also  forms,  with  sodium  chloride,  a  crystalline  compound  contain- 
ing C,2H22On  .  NaCl. 

Cane-sugar  is  not  directly  fermentable,  but  when  its  dilute  aqueous  solu- 
tion is  mixed  with  yeast,  and  exposed  to  a  warm  atmosphere,  it  is  first 
resolved  into  a  mixture  of  dextrose  and  levulose  (p.  577),  which  then  enter 
into  fermentation,  yielding  alcohol  and  carbon  dioxide. 

Paras accharose,  Ci2H22On. — This  is  an  isomer  of  cane-sugar,  produced, 
according  to  Jodin,*  by  spontaneous  fermentation.  An  aqueous  solution 
of  cane-sugar  containing  ammonium  phosphate  left  to  itself  for  three 
months  in  summer,  yielded,  under  circumstances  not  further  specified,  a 
crystallizable  sugar,  isomeric  with  saccharose,  together  with  an  amorphous 
sugar  having  the  composition  of  a  glucose,  both  dextro-rotatory.  Para- 
saccharose  is  very  soluble  in  water,  nearly  insoluble  in  alcohol  of  90  per 
cent.  Its  specific  rotatory  power  at  10°  =  -f-  108°,  appearing  to  increase 
a  little  with  rise  of  temperature.  It  does  not  melt  at  100°,  but  becomes 
colored,  and  appears  to  decompose.  It  reduces  an  alkaline  cupric  .solution, 
but  only  half  as  strongly  as  dextro-glucose.  It  is  not  perceptibly  altered 
by  dilute  sulphuric  acid,  even  at  100° ;  hydrochloric  acid  weakens  its  rota- 
tory power,  turns  the  solution  brown,  and  heightens  its  reducing  power  for 
cupric  oxide. 

Melitose,  C,2IT220,,. — A  kind  of  sugar  obtained  from  the  manna  which 
falls  in  opaque  drops  from  various  species  of  Eucalyptus  growing  in  Tas- 
mania. It  is  extracted  by  water,  and  crystallizes  in  extremely  thin  inter- 
laced needles,  having  a  slightly  saccharine  taste. 

The  crystals  of  melitose  are  hydrated,  containing  C,2II22On  .  30II2.  They 
give  off  2  atoms  water  at  100°,  and  become  anhydrous  at  130°  C.  (266°  F.). 

*  Comptes  Rendus,  torn.  liii.  p.  1252 ;  liv.  720. 


MELEZITOSE — TREHALOSE — MYCOSE — MILK-SUGAK.   587 

They  dissolve  in  9  parts  of  cold  water,  very  easily  in  boiling  water,  and 
dissolve  also  in  boiling  alcohol  more  freely  than  mannite.  The  alcoholic 
solution  yields  small  but  well-developed  crystals.  The  aqueous  solution 
turns  the  plane  of  polarization  to  the  right :  for  the  transition  tint  [a]  = 
+  102°. 

Melitose,  heated  with  dilute  sulphuric  acid,  is  resolved  into  a  fermentable 
sugar  (probably  dextroglucose),  and  non-fermentable  eucalyn  (p.  578). 
Melitose  ferments  in  contact  with  yeast,  but  is  resolved,  in  the  first  in- 
stance, into  glucose  and  eucalyn.  It  does  not  reduce  an  alkaline  cupric 
solution,  and  is  not  altered  by  boiling  with  dilute  alkalies  or  with  baryta- 
water.  It  is  oxidized  by  nitric  acid,  yielding  a  certain  quantity  of  mucic 
acid,  together  with  a  large  quantity  of  oxalic  acid. 

Melezitose,  C12H22On. — This  variety  of  sugar  is  found  in  the  so-called 
manna  of  Briangon,  which  exudes  from  the  young  shoots  of  the  larch 
(Larix  Europsea).  The  manna  is  exhausted  with  alcohol,  which,  when  evap- 
orated, yields  melezitose  in  very  small,  hard,  shining  efflorescent  crystals, 
which  give  off  4  per  cent,  of  water  when  heated,  melt  below  140°  without 
further  alteration,  forming  a  liquid  which  solidifies  to  a  glass  on  cooling. 
Melezitose  is  dextro-rotatory;  [a]  =  -(-  94-1°.  It  dissolves  easily  in 
water,  is  nearly  insoluble  in  cold,  slightly  soluble  in  boiling  alcohol. 

Melezitose  decomposes  at  about  200°  C.  (392°  F.).  It  is  carbonized  by 
cold  strong  sulphuric  acid,  quickly  turns  brown  with  boiling  hydrochloric 
acid,  and  forms  oxalic  acid  with  nitric  acid.  By  an  hour's  boiling  with 
dilute  sulphuric  acid,  it  is  converted  into  glucose.  In  contact  with  yeast  it 
passes  slowly,  or  sometimes  not  at  all,  into  vinous  fermentation.  It  is  not 
altered  at  100°  by  aqueous  alkalies,  and  scarcely  by  potassio-cupric  tar- 
trate. 

Trehalose,  C12H220,, .  20H2*  is  obtained  from  Trehala  manna,  the  produce 
of  a  species  of  Echinops  growing  in  the  East,  by  extraction  with  boiling 
alcohol.  It  forms  shining  rhombic  crystals,  containing  C,2H22On  .  20H2, 
which  melt  when  quickly  heated  to  109°  C.  (228°  F.) ;  but  if  slowly  heated 
give  off  their  water  even  below  100°.  It  has  a  strongly  saccharine  taste, 
dissolves  easily  in  water  and  in  boiling  alcohol,  but  is  insoluble  in  ether. 
The  aqueous  solution  is  dextro-rotatory ;  [«]  —  -}-  199°. 

By  several  hours'  boiling  with  dilute  sulphuric  acid,  it  is  converted  into 
dextroglucose.  With  strong  nitric  acid  it  forms  a  detonating  nitro-com- 
pound ;  heated  with  dilute  nitric  acid  it  yields  oxalic  acid.  In  contact  with 
yeast  it  passes  slowly  and  imperfectly  into  alcoholic  fermentation.  It  is 
not  altered  by  boiling  with  alkalies,  and  does  not  reduce  cuprous  oxide 
from  alkaline  cupric  solutions.  Heated  with  acetic  or  butyric  acid,  it  yields 
compounds  not  distinguishable  from  those  which  are  formed  in  like  man- 
ner from  dextroglucose  (p.  577). 

Mycose,  C12H22On  .  20H2,  is  a  kind  of  sugar  very  much  like  trehalose, 
obtained  from  ergot  of  rye  by  precipitating  the  aqueous  extract  of  the 
fungus  with  basic  lead  acetate,  removing  the  lead  from  the  filtrate  by 
sulph-hydric  acid,  evaporating  to  a  syrup,  and  leaving  the  liquid  to  crys- 
tallize. It  differs  from  trehalose  only  in  possessing  a  somewhat  feebler 
rotatory  power;  [a]  =  -4-  192-5°,  and  in  not  being  completely  dehydrated 
at  100°. 

Milk-sugar,  Lactin,  or  Lactose,  C^Tl^O^  .  OH2.—  This  kind  of  sugar  is 
an  important  constituent  of  milk;  it  is  obtained  in  large  quantities  by  evap- 
orating whey  to  a  syrupy  state,  and  purifying  the  lactose,  which  slowly 
crystallizes  out,  with  animal  charcoal.  It  forms  white,  translucent,  four- 
sided,  trimetric  prisms,  of  great  hardness.  It  is  slow  and  difficult  of  solu- 
tion in  cold  water,  requiring  for  that  purpose  5  or  6  times  its  weight :  it 


588  HEXATOMIC    ALCOHOLS   AND   ETHERS. 

lias  a  faint,  sweet  taste,  and  in  the  solid  state  feels  gritty  between  the  teeth. 
When  heated,  it  loses  water,  and  at  a  high  temperature  blackens  and  de- 
composes. Milk-sugar  combines  with  bases,,»forming  compounds  which 
have  an  alkaline  reaction,  and  are  easily  decomposed.  Dilute  acids  con- 
vert it  into  galactose  -{p.  578). 

Milk-sugar,  when  distilled  with  oxidizing  mixtures,  such  as  sulphuric 
acid  arid  manganese  dioxide,  yields  formic  acid.  With  nitric  acid,  it  forms 
mucic,  saccharic,  tartaric,  and  a  small  quantity  of  racemic  acid,  and  finally 
oxalic  acid.  Very  strong  nitric  acid,  or  a  mixture  of  nitric  and  sulphuric 
acids,  converts  milk-sugar  into  a  crystalline  substitution-product  called 
nitro-lactin. 

Milk-sugar  is  not  brought  immediately  by  yeast  into  the  state  of  alco- 
holic fermentation;  but  when  it  is  left  for  some  time  in  contact  with  yeast, 
fermentation  gradually  sets  in.  When  cheese  or  gluten  is  used  as  the  fer- 
ment, the  milk-sugar  is  converted  into  lactic  acid.  Alcohol  is,  however, 
always  formed  at  the  same  time,  especially  if  no  chalk  is  added  to  neutral- 
ize the  acid  as  it  forms ;  the  quantity  of  alcohol  formed  is  greater  also  as 
the  solution  is  more  dilute. 

Gum.  —  Gum-arabic,  which  is  the  produce  of  several  species  of  acacia, 
may  be  taken  as  the  most  perfect  type  of  this  class  of  bodies.  In  its  purest 
and  finest  condition,  it  forms  white  or  slightly  yellowish  irregular  masses, 
which  are  destitute  of  crystalline  structure,  and  break  with  a  smooth  cou- 
choi'dal  fracture.  It  is  soluble  in  cold  water,  forming  a  viscid,  adhesive, 
tasteless  solution,  from  which  the  pure  soluble  gummy  principle,  or  arabin, 
is  precipitated  by  alcohol,  and  by  basic  lead  acetate,  but  not  by  the  neutral 
acetate.  Arabin  is  composed  of  C12H22On,  and  is  consequently  isomeric 
with  cane-sugar. 

Mucilage,  so  abundant  in  linseed,  in  the  roots  of  the  mallow,  in  salep,  the 
fleshy  root  of  Orchis  mascula,  and  in  other  plants,  diifers  in  some  respects 
from  gum-arabic,  although  it  agrees  in  the  property  of  dissolving  in  cold 
water.  The  solution  is  less  transparent  than  that  of  gum,  and  is  precipi- 
tated by  neutral  lead  acetate.  Gum-tragacanth  is  chiefly  composed  of  a 
kind  of  mucilage  to  which  the  name  bassorin  has  been  given ;  it  refuses  to 
dissolve  in  water,  merely  softening  and  assuming  a  gelatinous  aspect.  It 
is  dissoved  by  caustic  alcali.  Cerasin  is  the  insoluble  portion  of  the  gum 
of  the  cherry-tree  ;  it  resembles  bassorin.  The  composition  of  these  vari- 
ous substances  has  been  carefully  examined  by  Schmidt,  who  finds  that  it 
closely  agrees  with  that  of  starch.  Mucilage  invariably  contains  hydrogen 
and  oxygen  in  the  proportion  in  which  they  form  water,  and  when  treated 
with  acid,  yields  glucose. 

Pectin,  or  the  jelly  of  fruits,  is,  in  its  physical  properties,  closely  allied 
to  the  foregoing  bodies.  It  may  be  extracted  from  various  vegetable  juices 
by  precipitation  with  alcohol.  It  forms  when  moist  a  transparent  jelly, 
which  is  soluble  in  water,  tasteless,  and  dries  up  to  a  translucent  mass.  It 
is  to  this  substance  that  the  firm  consistence  of  currant  and  other  fruit- 
jellies  is  ascribed.  According  to  Fre"my,  the  composition  of  pectin  is 
C32H48032.  By  ebullition  with  water  and  with  dilute  acids  it  is  changed 
into  two  isomeric  modifications,  called  paropectin  and  metopectin.  In  contact 
with  bases,  these  three  substances  are  converted  intopectic  acid,  C16H22C15  (?), 
which  closely  resembles  pectin,  except  that  it  possesses  feeble  acid  proper- 
ties, and  is  insoluble  in  water.  By  long  boiling  with  caustic  alkali,  a  fur- 
ther change  is  produced,  and  metopectic  acid,  C24H32027  (?),  is  formed,  which 
does  not  gelatinize.  The  metallic  pectates  and  metapectates  are  uncrystal- 
lizable.  Much  doubt  still  exists  respecting  the  composition  of  the  various 
bodies  of  the  pectin  group ;  but  from  the  analyses  hitherto  made,  they  do 
not  appear  to  contain  hydrogen  and  oxygen  in  the  proportion  to  form  water 
and  therefore  scarcely  belong  to  the  sugar  and  starch  group. 


uu 

• 


OXYGEN-ETHERS  —  STAKCH.  589 


OXYGEN-ETHERS,  OR  ANHYDRIDES,  OF  THE  POLYGLUCOSIC  ALCOHOLS. 

These  compounds,  which  are  important  constituents  of  the  vegetable  or- 
ganism, may  be  derived  from  glucose  and  the  polyglucosic  alcohols  by 
abstraction  of  a  molecule  of  water: 

C6HIa06      -    H20 

Glucose. 

CwH-jAj      —     H20     =     CuH^Ojo,  or  2C6H1005, 
Diglucosic 
alcohol. 

CwH^O,,     —    H20    =    C^Otf,  or  3C6H1005, 
Triglucosio 
alcohol. 


C6JI10n+2b5n+i  —  H20  =  C6nH10n05 
All  these  bodies  are  therefore  isomeric  or  polymeric  one  with  the  other. 
Their  compounds  with  metallic  oxides,  &c.,  have  not  been  sufficiently  in- 
vestigated to  fix  their  exact  molecular  weight,  or  to  determine  in  each 
case  the  value  of  n;  but  from  the  mode  of  conversion  of  starch  into  glu- 
cose, and  the  constitution  of  certain  substitution-products  obtained  by  the 
action  of  nitric  acid  on  cellulose,  it  appears  most  probable  that  in  these 
bodies  n=3. 

Starch,  nC6H1006,  probably  C18H300]5,  also  called  Fecultt  and  Amidine. — 
This  is  one  of  the  most  important  and  widely  diffused  of  the  vegetable  prox- 
imate principles,  being  found  to  a  greater  or  less  extent  in  every  plant.  Tt 
is  most  abundant  in  certain  roots  and  tubers,  and  in  soft  stems :  seeds  often 
contain  it  in  large  quantity.  From  these  sources  the  starch  can  be  obtained 
by  rasping  or  grinding  the  vegetable  structure  to  pulp,  and  washing  the 
mass  upon  a  sieve,  by  which  the  torn  cellular  tissue  is  retained,  while  the 
starch  passes  through  with  the  liquid,  and  eventually  settles  down  from 
the  latter  as  a  soft,  white,  insoluble  powder,  which  may  be  washed  with 
cold  water,  and  dried  at  a  very  gentle  heat. 
•Potatoes  treated  in  this  manner  yield  a  large  -fig- 193. 

proportion  of  starch.  Starch  from  grain  may  be 
prepared  in  the  same  manner,  by  mixing  the 
meal  with  water  to  a  paste,  and  washing  the 
mass  upon  a  sieve :  a  nearly  white,  insoluble 
substance  called  gluten  is  then  left,  containing  a 
large  proportion  of  nitrogen.  The  gluten  of 
wheat-flour  is  extremely  tenacious  and  elastic. 
The  value  of  meal  as  an  article  of  food  greatly 
depends  upon  this  substance.  Starch  from  grain 
is  commonly  manufactured  on  the  large  scale  by 
steeping  the  material  in  water  for  a  consider- 
able time,  when  the  lactic  acid,  always  devel- 
oped under  such  circumstances  from  the  sugar 
of  the  seed,  disintegrates,  and  in  part  dissolves 
the  azotized  matter,  thereby  greatly  facilitating 
the  mechanical  separation  of  that  which  re- 
mains.  A  still  more  easy  and  successful  process  has  lately  been  introduced, 
in  which  a  very  dilute  solution  of  caustic  soda,  containing  about  200  grains 
of  alkali  to  a  gallon  of  liquid,  is  employed  with  the  same  view.  Excellent 
starch  is  thus  prepared  from  rice.  Starch  is  insoluble  in  cold  water,  as 
50 


590  HEXATOMIC   ALCOHOLS    AND   ETHERS. 

indeed  its  mode  of  preparation  sufficiently  shows :  it  is  equally  insoluble 
in  alcohol  and  other  liquids,  which  do  not  effect  its  decomposition.  To 
the  naked  eye  it  presents  the  appearance  of  a  soft,  white,  and  often  glis- 
tening powder :  under  the  microscope  it  is  seen  to  be  altogether  destitute 
of  crystalline  structure,  but  to  possess,  on  the  contrary,  a  kind  of  organi- 
zation, being  made  up  of  multitudes  of  little  rounded  transparent  bodies, 
upon  each  of  which  a  series  of  depressed  parallel  rings,  surrounding  a 
central  spot  or  hilum,  may  often  be  traced.  The  starch-granules  from  dif- 
ferent plants  vary  both  in  magnitude  and  form:  those  from  the  Canna  coc- 
cinea,  or  tons  les  mois,  and  potato  being  lai-gest ;  and  those  from  wheat,  and 
the  cereals  in  general,  very  much  smaller.  Figure  193  will  serve  to  con- 
vey an  idea  of  the  appearance  of  the  granules  of  potato-starch,  highly  mag- 
nified. 

When  a  mixture  of  starch  and  water  is  heated  to  near  the  boiling-point 
of  the  latter,  the  granules  burst  and  disappear,  producing,  if  the  propor- 
tion of  starch  be  considerable,  a  thick  gelatinous  mass,  very  slightly  opal- 
escent, from  the  shreds  of  fine  membrane,  the  envelope  of  each  separate 
granule.  By  the  addition  of  a  large  quantity  of  water,  this  gelatinous 
starch,  or  amidin,  may  be  so  far  diluted  as  to  pass  in  great  measure  through 
filter-paper.  It  is  very  doubtful,  however,  how  far  the  substance  itself  is 
really  soluble  in  water,  at  least  when  cold;  it  is  more  likely  to  be  merely 
suspended  in  the  liquid  in  the  form  of  a  swollen,  transparent,  and  insoluble 
jelly,  of  extreme  tenuity.  Gelatinous  starch,  exposed  in  a  thin  layer  to  a 
dry  atmosphere,  becomes  converted  into  a  yellowish,  horny  substance,  like 
gum,  which,  when  put  into  water,  again  softens  and  swells. 

Thin  gelatinous  starch  is  precipitated  by  many  of  the  metallic  oxides, 
as  lime,  baryta,  and  lead  oxide ;  also  by  a  large  addition  of  alcohol.  In- 
fusion of  galls  throws  down  a  copious  yellowish  precipitate  containing  tan- 
nic  acid,  which  re-dissolves  when  the  solution  is  heated.  By  far  the  most 
characteristic  reaction,  however,  is  that  with  free  iodine,  which  forms  with 
starch  a  deep  indigo-blue  compound,  which  appears  to  dissolve  in  pure 
water,  although  it  is  insoluble  in  solutions  containing  free  acid  or  saline 
matter.  The  blue  liquid  has  its  color  destroyed  by  heat,  temporarily  if  the 
heat  be  quickly  withdrawn,  and  permanently  if  the  boiling  be  long  con- 
tinued, in  which  case  the  compound  is  decomposed  and  the  iodine  volatil- 
ized. Dry  starch,  put  into  iodine-water,  acquires  a  purplish-black  color. 

The  unaltered  and  the  gelatinous  starch,  in  a  dried  state,  have  the  same 
empirical  formula,  C6H1005.  A  compound  of  starch  and  lead  oxide  was 
found  to  contain,  when  dried  at  100°,  C6H1005  .  PbO,  or  C^H^O^  .  3PbO. 

DEXTRIN. — When  gelatinous  starch  is  boiled  with  a  small  quantity  of  di- 
lute sulphuric,  hydrochloric,  or  indeed,  almost  any  acid,  it  speedily  loses 
its  consistency,  and  becomes  thin  and  limpid,  from  having  suffered  conver- 
sion into  a  soluble  gum-like  substance,  called  dextrin,  on  account  of  its 
dextro-rotatory  action  on  polarized  light.  The  experiment  is  most  con- 
veniently made  with  sulphuric  acid,  which  may  be  afterward  withdrawn 
by  saturation  with  chalk.  The  liquid  filtered  from  the  nearly  insoluble 
gypsum,  may  then  be  evaporated  to  dryness  in  a  water-bath.  The  result 
is  a  gum-like  mass,  destitute  of  crystalline  structure,  soluble  in  cold  water, 
precipitable  from  its  solution  by  alcohol,  and  capable  of  combining  with 
lead  oxide. 

When  the  ebullition  with  the  dilute  acid  is  continued  for  a  considerable 
time,  the  dextrin  first  formed  undergoes  a  further  change,  and  becomes 
converted  into  dextro-glucose,  which  can  be  thus  artificially  produced  with 
the  greatest  facility.  The  length  of  time  required  for  this  remarkable 
change  depends  upon  the  quantity  of  acid  present ;  if  the  latter  be  very 
small,  it  is  necessary  to  continue  the  boiling  many  successive  hours,  re- 


STARCH.  591 

placing  the  water  which  evaporates.  With  a  larger  proportion  of  acid,  the 
conversion  is  much  more  speedy.  A  mixture  of  15  parts  of  potato-starch, 
60  parts  water,  and  0  parts  sulphuric  acid,  may  be  kept  boiling  for  about 
four  hours ;  the  liquid  neutralized  with  chalk,  filtered,  and  rapidly  evapo- 
rated to  a  small  bulk.  By  digestion  with  animal  charcoal  and  a  second 
filtration,  much  of  the  color  will  be  removed,  after  which  the  solution  may 
be  boiled  down  to  a  thin  syrup  and  left  to  crystallize :  in  the  course  of  a 
few  days  it  solidifies  to  a  mass  of  glucose.  There  is  another  method  of 
preparing  this  substance  from  starch  which  deserves  particular  notice. 
Germinating  seeds,  and  buds  in  the  act  of  development,  are  found  to  con- 
tain a  small  quantity  of  a  peculiar  azotized  substance,  called  diastase ;  formed 
at  this  particular  period  from  the  gluten  of  vegetable  albuminous  matter. 
This  substance  possesses  the  same  curious  property  of  effecting  the  conver- 
sion of  starch  into  dextrin  and  glucose,  and  at  a  much  lower  temperature 
than  that  of  ebullition.  When  a  little  infusion  of  malt,  or  germinated  bar- 
ley, in  tepid  water,  is  mixed  with  a  large  quantity  of  thick  gelatinous  starch, 
and  the  whole  maintained  at  about  71°,  complete  liquefaction  takes  place 
in  the  space  of  a  few  minutes  from  the  production  of  dextrin  and  glucose. 
If  a  greater  degree  of  heat  be  employed,  the  diastase  is  coagulated  and 
rendered  insoluble  and  inactive.  Very  little  is  known  respecting  diastase 
itself;  it  seems  very  much  to  resemble  vegetable  albumin,  but  has  never 
been  obtained  in  a  state  of  purity. 

The  change  of  starch  or  dextrin  into  sugar,  whether  produced  by  the 
action  of  dilute  acid  or  by  diastase,  takes  place  quite  independently  of  the 
oxygen  of  the  air,  and  is  unaccompanied  by  any  secondary  product.  The 
acid  takes  no  direct  part  in  the  reaction;  it  may,  if  not  volatile,  be  all 
withdrawn  without  loss  after  the  experiment.  The  whole  reaction  lies 
between  the  starch  and  the  elements  of  water,  a  fixation  of  the  latter  oc- 
curring in  the  new  product,  as  will  be  seen  on  comparing  the  composition 
of  starch  and  glucose.  Dextrin  itself  has  exactly  the  same  composition  as 
the  original  starch. 

It  was  formerly  supposed  that,  in  the  action  of  acids  or  of  disastase  upon 
starch,  the  starch  is  first  converted  into  dextrin  by  a  mere  alteration  of 
physical  structure,  and  that  the  dextrin  then  takes  up  the  elements  of 
water,  and  is  converted  into  glucose,  this  second  stage  of  the  process  oc- 
cupying a  much  longer  time  than  the  first;  but  from  recent  experiments 
by  Musculus*  it  appears  that  both  dextrin  and  glucose  are  produced  at  the 
very  commencement  of  the  reaction,  and  always  in  the  proportion  of  1 
molecule  of  glucose  to  2  molecules  of  dextrin,  whence  it  may  be  inferred 
that  the  molecule  of  starch  contains  C18H30015,  and  that  it  is  resolved  into 
glucose  and  dextrin  by  taking  up  a  molecule  of  water: 

C18H30015        +        OH2        =        C.HW06        +        2CaH1006 
Starch.  Glucose.  Dextrin. 

When  the  conversion  is  effected  by  a  dilute  acid,  the  dextrin  is,  after  sev- 
eral hours'  boiling,  completely  converted  into  glucose,  which  is  therefore 
the  sole  ultimate  product  of  the  reaction.  But  when  diastase  is  used  as 
the  converting  agent,  the  production  of  glucose  goes  on  only  so  long  as 
there  is  any  unaltered  starch  still  present,  the  dextrin  undergoing  no  fur- 
ther alteration. 

Dextrin  is  used  in  the  arts  as  a  substitute  for  gum ;  it  is  sometimes  made 
in  the  manner  above  described,  but  more  frequently  by  heating  dry  potato- 
starch  to  400°  C.  (752°  F.),  by  which  it  acquires  a  yellowish  tint  and  be- 
comes soluble  in  cold  water.  It  is  sold  in  this  state  under  the  name  of 
Britith  dun. 

Starch  is  an  important  article  of  food,  especially  when  associated,  as  in 

*  Comptes  Rendus,  1.  785;  liv.  191;  Ann.  Ch.  Phys.  [3],  Ix.  208;  [4],  vi.  177. 


592  HEXATOMTC    ALCOHOLS   AND   ETHERS, 

ordinary  meal,  with  albuminous  substances.  Arrowroot,  and  the  fecula  of 
the  Canna  coccinea,  are  very  pure  varieties,  employed  as  articles  of  diet; 
arrowroot  is  obtained  from  the  Maranta  arundinacea,  cultivated  in  the  West 
Indies;  it  is  with  difficulty  distinguished  from  potato-starch.  —  Tapioca  is 
prepared  from  the  root  of  the  Jalropha  manihot,  being  thoroughly  purified 
from  its  poisonous  juice.  —  Cassava  is  the  same  substance  modified  while 
moist  by  heat. — Sago  is  made  from  the  soft  central  portion  of  the  stem  of 
a  palm ;  and  salep  from  the  fleshy  root  of  the  Orchis  mascula. 

STARCH  FROM  ICELAND  Moss. — The  lichen  called  Cetraria  Islandica,  puri- 
fied by  a  little  cold  solution  of  potash  from  a  bitter  principle,  yields,  when  ^ 
boiled  in  water,  a  slimy  and  nearly  colorless  liquid,  which  gelatinizes  on  ' 
cooling,  and  dries  up  to  a  yellowish  amorphous  mass,  which  does  not  dis- 
solve in  cold  water,  but  merely  softens  and  swells.  A  solution  of  this  sub- 
stance in  warm  water  is  not  affected  by  iodine,  although  the  jelly  is  ren- 
dered blue.  It  is  precipitated  by  alcohol,  lead  acetate,  and  infusion  of  galls, 
and  is  converted  into  glucose  by  boiling  with  dilute  sulphuric  acid.  Ac- 
cording to  Mulder,  it  contains  C6H1005.  The  jelly  from  certain  algse,  as 
that  of  Ceylon,  and  the  so-called  Carragheen  moss,  closely  resembles  the 
above. 

INULIN. —  This  substance,  which  differs  from  common  starch  in  some 
important  particulars,  is  found  in  the  root  of  Inula  hclenium,  Helianthus  tu- 
berosus,  dahlia,  and  several  other  plants :  it  may  be  easily  obtained  by  wash- 
ing the  rasped  root  on  a  sieve,  and  allowing  the  inulin  to  settle  down  from 
the  liquid;  or  by  cutting  the  root  into  thin  slices,  boiling  these  in  water, 
and  filtering  while  hot;  the  inulin  separates  as  the  solution  cools.  It  is  a 
white,  amorphous,  tasteless  substance,  nearly  insoluble  in  cold  water,  but 
freely  dissolves  by  the  aid  of  heat;  the  solution  is  precipitated  by  alcohol, 
but  not  by  acetate  of  lead  or  infusion  of  galls.  Iodine  colors  it  brown. 
Inulin  has  the  same  percentage  composition  as  common  starch.  By  boiling 
with  dilute  acids,  it  is  completely  converted  into  levulose  (p.  577) 

Cellulose,  wC6H|006,  probably  C18H300 13 ;  also  called  Lignin. — This  sub- 
stance constitutes  the  fundamental  material  of  the  structure  of  plants ;  it 
is  employed  in  the  organization  of  cells  and  vessels  of  all  kinds,  and  forms 
a  large  proportion  of  the  solid  parts  of  every  vegetable.  It  must  not  be 
confounded  with  ligneous  or  ivoody  tissue,  which  is  in  reality  cellulose  with 
other  substances  superadded,  incrusting  the  walls  of  the  original  mem- 
branous cells,  and  conferring  stiffness  and  inflexibility.  Thus  woody  tissue, 
even  when  freed  as  much  as  possible  from  coloring  matter  and  resin  by 
repeated  boiling  with  water  and  alcohol,  yields,  on  analysis,  a  result  indi- 
cating an  excess  of  hydrogen  above  that  required  to  form  water  with  the 
oxygen,  besides  traces  of  nitrogen.  Pure  cellulose,  on  the  other  hand, 
has  the  same  percentage  composition  as  starch.* 

The  properties  of  cellulose  may  be  conveniently  studied  in  fine  linen 
and  cotton,  which  are  almost  entirely  composed  of  the  body  in  question, 
the  associated  vegetable  principles  having  been  removed  or  destroyed  by 
the  variety  of  treatment  to  which  the  fibre  has  been  subjected.  Pure  cel- 
lulose is  tasteless,  insoluble  in  water  and  alcohol,  and  absolutely  innutri- 
tions: it  is  not  sensibly  affected  by  boiling  water,  unless  it  happens  to 
have  been  derived  from  a  soft  or  imperfectly  developed  portion  of  the 
plant,  in  which  case  it  is  disintegrated  and  rendered  pulpy.  Dilute  acids 
and  alkalies  exert  but  little  action  on  lignin,  even  at  a  boiling  tempera- 
ture ;  strong  oil  of  vitriol  converts  it,  in  the  cold,  into  a  nearly  colorless, 
adhesive  substance,  which  dissolves  in  water,  and  presents  the  characters 


*  Dumas,  Chimie  appliqu6e  aux  Arts,  vi.  5. 


CELLULOSE.  593 

of  dextrin.  This  curious  and  interesting  experiment  may  be  conveniently 
made  by  very  slowly  adding  concentrated  sulphuric  acid  to  half  its  weight 
of  lint,  or  linen  cut  into  small  shreds,  taking  care  to  avoid  any  rise  of  tem- 
perature which  would  be  attended  with  charring  or  blackening.  The  mix- 
ing is  completed  by  trituration  in  a  mortar,  and  the  whole  left  to  stand  a 
few  hours  ;  after  which  it  is  rubbed  up  with  water,  warmed,  and  filtered 
from  a  little  insoluble  matter.  The  solution  may  then  be  neutralized  with 
chalk,  and  again  filtered.  The  gummy  liquid  retains  lime,  partly  in  the 
state  of  sulphate,  and  partly  in  combination  with  sulpholignic  acid,  an 
acid  composed  of  the  elements  of  sulphuric  acid,  in  union  with  those  of 
cellulose.  If  the  liquid,  previous  to  neutralization,  be  boiled  during  three 
or  four  hours,  and  the  water  replaced  as  it  evaporates,  the  dextrin  becomes 
entirely  changed  to  glucose.  Linen  rags  may,  by  these  means,  be  made  to 
furnish  more  than  their  own  weight  of  that  substance.  If  a  piece  of  un- 
sized paper  be  dipped  for  a  few  seconds  into  a  mixture  of  2  volumes  of  con- 
centrated sulphuric  acid  and  1  volume  of  water,  and  then  thoroughly 
washed  with  water  and  dilute  ammonia,  a  substance  is  obtained  which 
resembles  parchment,  and  has  the  same  composition  as  cellulose;  it  occurs 
in  commerce  under  the  name  of  parchment  paper  (papyrin).  An  excel- 
lent application  of  this  substance  in  diffusion  experiments  is  mentioned  on 
page  149. 

Cellulose  dissolves  in  an  ammoniacal  solution  of  cupric  oxide  (prepared 
by  dissolving  basic  cupric  carbonate  in  strong  ammonia),  from  which  it  is 
precipitated  by  acids  in  colorless  flakes. 

Cellulose  is  not  colored  by  iodine. 

XYLOIDIN  AND  PYROXYLIN. — When  starch  is  mixed  with  nitric  acid  of  spe- 
cific gravity  1-5,  it  is  converted,  without  disengagement  of  gas,  into  a 
transparent,  colorless  jelly,  which,  when  put  into  water,  yields  a  white, 
curdy,  insoluble  substance:  this  is  xylo'idin.  When  dry,  it  is  white  and 
tasteless,  insoluble  even  in  boiling  water,  but  freely  dissolved  by  dilute 
nitric  acid,  and  the  solution  yields  oxalic  acid  when  boiled.  Other  sub- 
stances belonging  to  the  same  class  also  yield  xylo'idin ;  paper  dipped  into 
the  strongest  nitric  acid,  quickly  plunged  into  water,  and  afterward  dried, 
becomes  in  great  part  so  changed :  it  assumes  the  appearance  of  parch- 
ment, and  acquires  an  extraordinary  degree  of  combustibility. 

If  pure,  finely  divided  ligneous  matter,  as  cotton-wool,  be  steeped  for  a 
few  minutes  in  a  mixture  of  nitric  acid  of  sp.  gr.  1-5  and  concentrated 
sulphuric  acid,  then  squeezed,  thoroughly  washed,  and  dried  by  very 
gentle  heat,  it  will  be  found  to  have  increased  in  weight  about  70  per  cent., 
and  to  have  become  highly  explosive,  taking  fire  at  a  temperature  not  much 
above  149°  C.  (300°  F.),  and  burning  without  smoke  or  residue.  This  is 
pyroxylin,  the  gun-cotton  of  Professor  Schonbein. 

Xylo'idin  and  pyroxylin  are  substitution-products  consisting  of  starch  and 
cellulose,  in  which  the  hydrogen  is  more  or  less  replaced  by  nitryl,  N02. 
Xylo'idin  consists  of  C6H9(N02)05,  or  C,gH27(N02)30J5.  Of  pyroxylin  several 
varieties  are  known,  distinguished  by  their  different  degrees  of  stability 
and  solubility  in  alcohol,  ether,  and  other  liquids.  According  to  Hadow,* 
the  three  principal  varieties  are : 

a.— C181[21(N02)90,5,  or  C6H7(N02)305,  insoluble  in  a  mixture  of  ether  and 
alcohol,  but  soluble  in  ethylic  acetate.  It  is  produced  by  repeated  immer- 
sion of  cotton-wool  in  a  mixture  of  2  molecules  of  nitric  acid,  N03H,  2 
molecules  of  oil  of  vitriol,  S04H2,  and  three  molecules  of  water. 

0. — C18H22(N02)80,5,  soluble  in  ether-alcohol,  insoluble  in  glacial  acetic 


*  Chom.  Soc.  Journal,  vii.  201. — A  series  of  elaborate  and  valuable  researches  on  gmi- 
coltnu  IM-,  n-<-.-iitlv  buun  published  by  Abd  (Proceed.  ttuyal  Soc.)  xv.  182;  Chetu.  Soc.  J.  [15], 
XT.  310. 

50* 


594  HEXATOMIC    ALCOHOLS   AND    ETHERS. 

acid.  Produced  when  the  acid  mixture  contains  half  a  molecule  more 
water  than  in  a. 

y. — 018H23(N02)70,5  (Gladstone's  cotton-xyloidin},  soluble  in  ether  and  in 
glacial  acetic  acid.  Produced  when  the  acid  mixture  contains  one  mole- 
cule more  water  than  in  o. 

The  first  of  these,  which  consists  of  trinitrocellulose,  is  the  most  explo- 
sive of  the  three,  and  the  least  liable  to  spontaneous  decomposition.  It  is 
the  only  one  adapted  for  use  in  gunnery,  and  is  especially  distinguished  as 
"gun-cotton."  From  the  experiments  of  General  von  Lenk,  of  the  Aus- 
trian service,it  appears  that  to  insure  the  uniform  production  of  this  par- 
ticular compound  the  following  precautions  are  necessary: 

1.  The  cleansing  and  perfect  desiccation  of  the  cotton,  previously  to  its 
immersion  in  the  mixed  acids. — 2.  The  employment  of  the  strongest  acids 
procurable  in  commerce. — 3.  The  steeping  of  the  cotton  in  a  fresh  strong 
mixture  of  acids  after  the  first  immersion  and  partial  conversion  into  gun- 
cotton. — 4.  The  continuance  of  the  steeping  for  forty-eight  hours. — 5.  The 
thorough  purification  of  the  gun-cotton  thus  produced  from  every  trace  of 
free  acid,  by  washing  the  product  in  a  stream  of  water  for  several  weeks  ; 
subsequently  a  weak  solution  of  potash  may  be  used,  but  this  is  not  essen- 
tial. 

The  solution  of  the  less  highly  nitrated  compounds  in  alcohol  and  ether 
is  called  collodion.  This  solution,  when  left  to  evaporate,  dries  up  quickly 
to  a  thin,  transparent,  adhesive  membrane :  it  is  employed  with  great  ad- 
vantage in  surgery  as  an  air-tight  covering  for  wounds  and  burns.  It  is 
also  largely  used  in  photography  (p.  98). 

Glycogen,  wC6H1005,  was  obtained  by  Bernard  from  the  liver  of  several 
animals  (calf  or  pig)  by  exhaustion  with  water  and  precipitating  with 
boiling  alcohol.  The  precipitate  is  purified  by  boiling  with  dilute  pot- 
ash, repeatedly  dissolving  in  strong  acetic  acid,  and  precipitating  by 
alcohol.  Glycogen  also  enters  largely  into  the  composition  of  most  of  the 
tissues  of  the  embryo.  The  muscles  of  foetal  calves  of  three  to  seven 
months  have  been  found  to  yield  from  20  to  50  per  cent,  of  it. 

Glycogen  is  a  white,  amorphous,  starch-like  substance,  without  odor  or 
taste,  yielding  an  opalescent  solution  with  water,  but  insoluble  in  alcohol. 
It  does  not  reduce  an  alkaline  solution  of  copper.  This  substance  does  not 
ferment  with  yeast,  but  is  converted  into  glucose  by  boiling  with  dilute  acids, 
or  by  contact  with  diastase,  pancreatic  juice,  saliva,  or  blood. 


ORGANIC  ACIDS. 

ORGANIC  ACIDS,  or  carbon  acids,  are  derived,  as  we  have  several 
times  had  occasion  to  observe,  from  alcohols,  by  the  substitution  of 
oxygen  for  an  equivalent  quantity  of  hydrogen  (0  for  H2) ;  in  fact  they  are 
often  produced  directly  from  alcohols  by  the  action  of  oxidizing  agents. 
Now  the  formula  of  an  alcohol  is  derived  from  that  of  a  hydrocarbon  by 
substitution  of  one  or  more  equivalents  of  hydroxyl  (OH)  for  an  equal 
number  of  hydrogen-atoms,  the  number  of  such  substitutions  determining 
the  atomicity  of  the  alcohol  (p.  508),  that  is  to  say,  the  number  of  its  hy- 
drogen-atoms that  can  be  replaced  by  a  monatomic  alcohol  radical  or  acid 
radical,  and  in  some  cases  by  an  alkali-metal;  in  other  words,  the  number 
of  ethers  that  an  alcohol  can  form  with  a  monatomic  alcohol  radical  is  equal 
to  the  number  of  equivalents  of  hydroxyl  contained  in  its  molecules;  thus 
glycerin,  which  is  a  triatomic  molecule,  yields  three  ethylic  ethers : 

CH2OH  CH2OC2H6  CH2OC2H5  CH2OC2H5 

CHOH  CHOH  CHOH  CHOC2H6 

CH2OH  OH2OH  CH2OC2H5  CH2OC2H5 

Glycerin.        Mono  ethylin.         Diethylin.  Triethylin. 

The  hydrogen  thus  replaceable,  called  typic  hydrogen,  is  that  which  is 
combined  with  the  carbon,  not  directly,  but  only  through  the  medium  of 
oxygen. 

The  number  of  acids  which  any  alcohol  can  yield  is  equal  to  the  number 
of  times  that  the  group  or  radical,  CH2OH,  enters  into  its  molecule  ;  and 
the  passage  from  the  alcohol  to  the  acid  consists  in  the  substitution  of  0 
for  H2  in  this  group,  or  in  the  conversion  of  CH2OH  into  the  acid  radical 

CH3 

t!OOH,  called  oxatyl.     Thus  ethyl  alcohol,    I     '        ,  which  is  monatomic, 

CELOH 
CH3 
can  yield  but  one  acid,  namely,  acetic  acid,    |  ;  but  ethene  alcohol  or 

COOH 
glycol,  which  is  diatomic,  yields  two,  viz.,  glycollic  and  oxalic  acids: 

CH2OH  CH2OH  COOH 

CH2OH  COOH  COOH 

Ethene  Glycollic  Oxalic 

alcohol.  acid.  acid. 

Further  observation  shows  that  the  basicity  of  an  organic  acid,  that  is  to 
say  the  number  of  its  hydrogen-atoms  that  can  be  replaced  by  metals  to 
form  salts,  is  equal  to  the  number  of  equivalents  of  oxatyl  contained  in  it, 
or,  in  other  words,  to  the  number  of  hydrogen-molecules  (H2)  that  have 
been  replaced  by  oxygen  (0),  in  the  immediate  neighborhood  of  hydroxyl 
(Oil),  to  convert  the  alcohol  into  an  acid.  Thus  from  propene-glycol, 
C3I180.2,  are  derived  the  two  diatomic  acids,  lactic  acid,  C3!J6().,,  which  is 
monobasic,  and  malouic  acid,  C3H4O4,  which  is  bibasic : 

595 


596  ORGANIC   ACIDS. 

CH2OH  CH2OH  COOH 

CH2  CH2  CH2 

CH2OH  COOH  COOH 

Propene  Lactic  Malonic 

glycol.  acid.  acid. 

The  atomicity  of  an  acid  is  the  same  as  that  of  the  alcohol  from  which 
it  is  derived  ;  thus  lactic  acid,  though  it  contains  only  one  atom  of  basic  hy- 
drogen, and  therefore  forms  only  one  class  of  metallic  salts,  represented 
by  the  formula  C3H503M,  can  form  two  ethylic  ethers,  viz.,  ethyl-lactic  acid 
and  diethyl-lactate  or  ethyl-lactate  ;  thus  : 

CHaOH  CH2OC2H5  CH2OC2H6 

CH2  CH2  CH2 

COOH  COOH  COOC2H6 

Lactic  acid  Ethyl-lactic  Diethylic 

(monobasic).  acid  (mono-  lactate 

basic).  (neutral). 

From  these  considerations  it  appears,  that  monatomic  acids  must  neces- 
sarily be  monobasic ;  but  diatomic  acids  may  be  either  monobasic  or 
bibasic ;  triatomic  acids,  either  monobasic,  bibasic,  or  tribasic ;  and  so  on. 

Many  of  the  most  important  acids  are  derived,  in  the  manner  above  ex- 
plained, from  actually  known  alcohols ;  others,  though  they  have  no  alco- 
hols actually  corresponding  to  them,  are  homologous  with  other  acids  de- 
rived from  known  alcohols;  but  there  is  also  a  considerable  number  of 
acids,  especially  those  formed  in  the  vegetable  or  animal  organism,  which 
cannot  be  regarded  as  derivatives  of  alcohols  of  any  known  series;  but 
the  number  of  these  unclassified  acids  will  doubtless  diminish  as  their  com- 
position and  reactions  become  more  thoroughly  known. 

These  acids  may  also  be  regarded  as  compounds  of  hydroxyl  with  oxygen- 
ated radicals  (acid  radicals)  formed  from  the  corresponding  alcohol-radi- 
cals by  substitution  of  0  for  H2,  or  as  derived  from  one  or  more  molecules 
of  water  (according  to  their  atomicity),  by  substitution  of  such  radicals 
for  half  the  hydrogen  in  the  water ;  e.  g., 

Type. 

Slo  C^\o  c^°\o 

a.  j  a.  j  Jti     j 

Water.  Ethyl  alcohol.  Acetic  acid. 

H       \0  H 


Water  (2  mol.)         Propene  Lactic  acid.         Malonic  acid, 

glycol. 

In  these  typical  formulae  of  polyatomic  acids,  the  typic  or  alcoholic  hy- 
drogen (replaceable  only  by  alcoholic  or  acid  radicals),  is  placed,  for  dis- 
tinction, above  the  acid  radical ;  and  the  basic  hydrogen,  replaceable  either 
by  metals  or  alcohol  radicals,  below. 

The  acid  radicals  are  denoted  by  names  ending  in  yl,  formed  from  those 
of  the  acids  themselves ;  thus,  C2H30,  the  radical  of  acetic  acid,  is  called 
acetyl ;  C3H40,  is  lactyl;  C3H.,O.,,  is  malonyl,  &c. 

The   replacement  of  the  hydroxyl  in  an  acid  by  chlorine,  bromine,  or 


MONATOMIC   ACIDS. 


597 


iodine,  gives  rise  to  acid  chlorides,  &c.  ;  thus  from  acetic  acid,  C2H30(OH), 
is  derived  acetic  chloride,  C2H3OC1,  &c.  The  replacement  of  the  hydrogen 
within  the  radical  (radical  hydrogen)  by  the  same  elements,  or  by  the  rad- 
icals, CN,  N02,  NH2,  &c.,  gives  rise  to  chlorinated,  brominated,  cyanated, 
nitrated,  and  amidated  acids  (see  p.  469).  Lastly,  the  replacement,  of  the 
typic  hydrogen  by  alcohol-radicals  gives  rise  to  ethereal  salts  or  compound 
ethers  ;  and  its  replacement  by  acid  radicals  yields  acid  oxides  or  anhy- 
drides (p.  409).  The  derivatives  of  each  acid  will  be  described  in  connec- 
tion with  the  acid  itself. 


MONATOMIC  ACIDS. 

These  acids,  being  derived  from  monatomic  alcohols  by  substitution  of 
0  for  H2,  necessarily  contain  two  atoms  of  oxygen.  Each  series  of  hydro- 
carbons yields  a  series  of  monatomic  alcohols  and  a  series  of  monatomic 
acids ;  thus : 

Alcohols.  Acids. 

CaH2n+20  CnH2n02 


Hydrocarbons. 

CnH2n+2 

CnH2n 

Cn  H2n_2 

Cn  H2n_4 

&C. 


CaH2n_20 
CnH2n_40 

&c. 


CnH2n-402 
H2n 
&c. 


CnH2n_602 


The  best  known  monatomic  acids  are  those  belonging  to  the  series 
CnH2n02,  CnH2n_202,  CnH2u_802,  and  CnH2n_J002.  Of  the  other  series  only 
a  few  terms  have  hitherto  been  obtained. 

1.  —Acids  belonging  to  the  series  CnH2n02,  or  CnH2n_10(OH). 

These  acids  are  called  fatty  or  adipic  acids,  most  of  them  being  of  an  oily 
consistence,  and  the  higher  members  of  the  series  solid  fats.  The  follow- 
ing is  a  list  of  the  known  acids  of  the  series,  together  with  their  melting 
and  boiling  points. 


Name. 

Formula. 

Melting  point. 

Boiling  point. 

Formic  acid  . 

CII202 

+1°C. 

(34°  F.) 

100°  C. 

(212°  F.) 

Acetic  acid 

C2II402 

+17°  » 

(62°  »  ) 

117°  " 

(242°  "  ) 

Propionic  acid 

C3H602 

141°  « 

(280°  "  ) 

Butyric  acid      . 

C4II802 

below  —20°  C.  (-4°  F.) 

161°  " 

(322°  «) 

Valeric  acid  . 

C5H1002 



,  

175°  " 

(347°  "  ) 

Caproic  acid      .        .        . 

C6n12o2 

+5°C. 

(41°  F.) 

198°  " 

(389°  "  ) 

(Enaiithylic  acid   . 

C7u14oj 

212°  « 

>414o  »  ) 

Caprylic  acid     . 

C8Hio02 

+14°  C. 

(57°  F.) 

23(5°  " 

457°  «) 

Pdargonic  acid     .        . 
llutic  or  Capric  acid 

cyi18o2 

Cio'laA 

+18°  "  ? 
-(-30°  « 

(64°  "  ) 
(86°  " 

260°  " 

(500°  «  ) 

Laurie  acid    . 

C,«Ho402 

+43-6°  •« 

1  10°  " 

Mvristic  acid    . 

curr:^o, 

53-8°  " 

129°' 

Palmitic  acid 

CIGI&; 

62°" 

144°' 

Margaric  acid  . 

Cn»3A 

59-9°  "  ? 

140°  ' 

Stearic  acid  . 

OwHaSS 

69-2°  " 

q.r>7°  ' 

Ararhidic  acid 

C^H^O, 

75°  "        (167°  ' 

Beheiiic  acid 

C.olI44Oo 

76°" 

169°' 

Cerotic  acid 

<3HS3 

78o.« 

172°' 

Melissic  acid 

ciujjo! 

88°  "       (190°  " 

These  acids  may  be  represented  on  the  marsh-gas  type  and  on  the  water- 
type  by  the  following  formulae  : 


598  MONATOMIC   ACIDS. 

Acid. 

(C.-iH^i' 

or  | 

)H 


f(C^.iH^4'  yn-ii 

Marsh-gas..  0  oj  £  or^ 


Water   .  .  £  }  0  or  HOH  (C^-iO)'  1 0  or  ((^H^O/OH. 

If  in  either  of  these  formulae  we  make  n  successively  equal  to  1,  2,  3,  &c., 
we  get  the  formulas  of  formic,  acetic,  propionic,  &c.  acid ;  thus : 

fH  fCH,  rC2H5  fC3H7  (C4H9 

ClO"          CIO"  CIO"  CIO"  C]0" 

(OH          (OH  (OH  (OH  (OH 

Formic.  Acetic.  Propionic.         Butyric.          Valeric. 

The  acid  radicals  CnH2n_iO,  in  the  water-type  formulae,  may  be  regarded 
as  compounds  of  carbonyl  with  alcohol  radicals,  CnII2n_10  =  CO(Cn_iH2n_i), 
and  accordingly  the  several  acids  may  be  represented  as  follows : 


COH|Q  CO(CH3)|0 

Formic.  Acetic.  Propionic. 

All  the  acids  of  the  series  containing  more  than  three  carbon-atoms  admit 
of  isomeric  modifications,  according  to  the  constitution  of  the  alcohol-radi- 
cal which  they  contain:  butyric  acid,  C6H802,  for  example,  may  exhibit  the 
following  modifications  : 

Normal  butyric  acid.  Isobutyric  acid. 


v^rio 

I  H3C  CH3 

CH2CH2CHS  CH2  CH(CHS)2  V 

or  or        CH 

>=C— OH  CH2         0=C— OH 

0=C— OH 


=C— OH 


0 

But  none  of  these  acids  can  exhibit  modifications  analogous  to  the  second- 
ary and  tertiary  alcohols :  because  in  them  the  carbon-atom  which  is  asso- 
ciated with  hydroxyl  has  two  of  its  other  units  of  equivalence  satisfied  by 
an  atom  of  bivalent  oxygen,  and  therefore  cannot  unite  directly  with  more 
than  one  other  atom  of  carbon.  Accordingly,  it  is  found  that  the  second- 
ary and  tertiary  alcohols  are  not  converted  by  oxidation  into  acids  contain- 
ing the  same  number  of  carbon-atoms  as  themselves. 

Occurrence.  —  Most  of  the  fatty  acids  are  found  in  the  bodies  of  plants  or 
animals,  some  in  the  free  state:  formic  acid  in  ants  and  nettles:  valeric 
acid  in  valerian  root ;  pelargonic  acid  in  the  essential  oil  of  Pelargonium 
roseum;  and  cerotic  acid  in  bees'-wax.  Others  occur  as  ethereal  salts  of 
monatomic  or  polyatomic  alcohols :  as  cetyl  palmitate  in  spermaceti ;  ceryl 
cerotate  in  Chinese  wax;  glyceric  butyrate,  palmitate,  stearate,  &c.,  in 
natural  fats. 

Formation.  —  1.  By  oxidation  of  the  primary  alcohols  of  the  methyl  series, 
as  by  exposure  to  the  air  in  contact  with  platinum  black,  or  by  heating  with 
aqueous  chromic  acid. — 2.  By  the  oxidation  of  aldehydes.  In  this  case  an 
atom  of  oxygen  is  simply  added;  e.  ff.,  C2H40  (aldehyde)  -f-  0  =  C2H402 
(acetic  acid). 

3.  By  the  action  of  carbon  dioxide  on  the  potassium  or  sodium  compound 
of  an  alcohol-radical  of  the  methyl  series ;  thus, 


FATTY    ACIDS.  599 

CH3 
C02  4-  CH3Na  =  | 

COONa 

Carbon  Sodium  Sodium 

dioxide.  methide.  acetate. 

4.  By  the  action  of  alkalies  or  acids  on  the  cyanides  of  the  alcohol- 
radicals;  CnH.jQ.f-!:  thus, 

CnH2n+1  CnH2n+1 

4-        KOH  4-        OH2        =         |              4-        NH3 

CN  COOK 

Alcoholic        Potassium  Water.            Potassium-salt      Ammo- 

cyanide.           hydrate.  of  fatty  acid.          nia. 
and: 


4-        HC1          4-  20H3      =          |              4-      NH4C1 

CN  COOH 

Alcoholic      Hydrochloric  Water.               Potassium      Ammonium 

cyanide.               acid.  salt.               chloride. 

In  this  manner  the  cyanide  of  each  alcohol-radical  yields  the  potassium 
salt  of  the  acid  next  higher  in  the  series,  that  is,  containing  one  atom  of 
carbon  more;  methyl  cyanide,  for  example,  yielding  acetic  acid,  ethyl 
cyanide,  yielding  propionic  acid,  &c.  ;  thus, 

CH3  CH, 

4-        KOH        4-        OH3        =  4-        NH, 

CN  COOK 

Methyl  Potassium 

cyanide.  acetate. 

5.  By  the  action  of  water  on  the  corresponding  acid  chlorides;  e.  g.t 

C2H3OC1        4-        HOH        =        HC1        4-        C2H30(OH) 
Acetyl  Acetic  acid. 

chloride. 

Now,  these  acid  chlorides  can  be  produced,  in  some  instances  at  least,  by 
the  action  of  carbonyl  chloride  (phosgene  gas)  on  thecorresponding  par- 
affins ;  *  thus, 

CH4          -|-        COC12        =        HC1        -}-        C2H3OC1 
Methane.  Carbonyl  Acetyl 

chloride.  chloride. 

C4H,0        4-        COC12        =        HC1        4-        C5H9OC1 

Quartane.  Carbonyl  Valeryl 

chloride.  chloride. 

By  these  combined  reactions,  therefore,  the  paraffins  may  be  converted 
into  the  corresponding  fatty  acids. 

6.  By  the  following  reaction,  the  fatty  acids  may  be  built  up  one  from 
the  other,  starting  from  acetic  acid.f     Ethyl  acetate,  treated  with  sodium, 
gives  up  one  atom  of  radical  hydrogen  in  exchange  for  that  metal: 

CH3  CH2Na 

2l  4-        Na2        =        2  |  4-        Ha 

COOC2H6  COOC2H5 

Ethyl  Monosodic 

acetate.  ethyl  acetate. 

*  Harnitz-Harnitzky,  Ann.  Ch.  Pharm.  cxxxvi.  121. 

f  Franltland  aud  Duppa,  Proceed.  Roy.  Soc.  xiv.  198,  458;  xv.  37. 


600  MONATOMIC   ACIDS. 

By  acting  on  this  body  with  the  iodide  of  a  radical,  CnHjn-j-j,  ethylic 
ethers  of  the  higher  acids  may  be  produced;  thus, 

CH2Na  CH2CH3 

I    '  +  CH3I        =        Nal        +          | 

COOCSH.  COOC2H5 

Monosodic  Methyl  Ethyl 

ethyl  acetate.  iodide.  propionate. 

If  ethyl  iodide  were  used  instead  of  methyl  iodide,  the  product  would  be 
ethyl  butyrate,  C4H702C2H5.  It  has  not  been  found  possible  to  produce,  by 
this  reaction,  the  higher  acids  of  the  series  from  formic  acid. 

The  six  modes  of  formation  above  given  are  general,  or  capable  of  being 
made  so.  There  are  also  special  methods  of  producing  particular  acids  of 
the  series,  but  in  most  of  these  cases  the  reactions  cannot  be  distinctly 
traced  ;  thus  formic,  acetic,  propionic,  butyric,  and  valeric  acids  are  pro- 
duced by  the  oxidation  of  albumin,  fibrin,  casein,  gelatin,  and  other  similar 
substances:  propionic  and  butyric  acids  in  certain  kinds  of  fermentation; 
acetic  acid  by  the  destructive  distillation  of  wood  and  other  vegetable 
substances. 

Properties.  —  Most  of  the  fatty  acids  are,  at  ordinary  temperatures,  trans- 
parent and  colorless  liquids  ;  formic  and  acetic  acids  are  watery  ;  propionic 
acid  and  the  higher  acids,  up  to  pelargonic  acid,  are  oily  ;  rutic  acid  and 
those  above  it  are  solid  at  ordinary  temperatures,  most  of  them  being  crys- 
talline fats  ;  cerotic  and  melissic  acids  are  of  waxy  consistence.  By  in- 
specting the  table  on  page  597,  it  will  be  seen  that  the  boiling  points  of 
these  acids  dift'er,  for  the  most  part,  by  24°  C.  (43°  F.)  for  each  addition  of 
CH2.  There  are,  however,  a  few  exceptions  to  this  rule,  some  of  which  may 
arise  from  the  existence  of  isomeric  modifications.  The  boiling  points  of 
formic  and  acetic  acids,  however,  which  cannot  exhibit  any  such  modifi- 
cations, differ  by  only  17°  C.  (30°  F.). 

Reactions.  —  1.  When  the  fatty  acids  are  submitted  to  the  action  of  nas- 
cent oxygen  evolved  by  electrolysis,  the  oxatyl  (COOH)  contained  in  them, 
is  resolved  into  water  and  carbon  dioxide,  and  the  alcohol  radical  is  set 
free  ;  thus, 

C4H9  C4H9 

21             +        0        =        OH2  +        2C02        +          | 

COOH  C4H9 

Valeric  acid.  Diquartyl. 

2.  When  the  ammonium  salt  of  either  of  these  acids  is  heated  with  phos- 
phoric oxide,  it  gives  up  water  and  is  converted  into  the  cyanide  of  the 
alcohol-radical  next  below  it,  e.  g., 

CH3  CH. 

|    '  20H2  =  |    ' 

COONH4  CN 

Ammonium  Methyl 

acetate.  cyanide. 

This  reaction  is  the  converse  of  the  fourth  mode  of  formation  above 
given. 

3.  By  distilling  the  potassium  salt  of  a  fatty  acid  with  an  equivalent 
quantity  of  potassium  formate,  the  corresponding  aldehyde  is  obtained: 


=    CO(CH3)H     +     C03K2; 

Potassium  Potassium  Aldehyde.          Potassium 

acetate.  formate.  carbonate. 


FATTY   ACIDS.  601 

and  the  aldehyde,  treated  with  nascent  hydrogen,  is  converted  into  a  pri- 
mary alcohol: 

CH3  CH3 

|  +                H2               = 

COH  CH2OH 

Aldehyde.  Alcohol. 

4.  By  subjecting  the  barium  or  calcium  salt  of  a  fatty  acid  to  dry  distil- 
lation, a  similar  decomposition  takes  place,  resulting  in  the  formation  of  a 

ketone  : 


+        C03Ca"; 

Calcium  Acetone.  Calcium 

acetate.  carbonate. 

and  the  ketone,  treated  with  nascent  hydrogen,  yields  a  secondary  alcohol  : 

CH3  H3C  CH3 

I    '        +  H2  V 

COCHS  CHOH 

Acetone.  Secondary 

propyl  alcohol. 

By  these  reactions,  the  fatty  acids  may  be  converted  into  alcohols. 
5.  The  fatty  acids,  heated  with  alcohols  in  sealed  tubes,  yield  compound 
ethers,  or  ethereal  salts,  water  being  eliminated  : 

C4H70(OH)     -f     HOC2H6    =    OH2    -f     C4H70(OC2H6) 
Butyric  Ethyl  Ethyl 

acid.  alcohol.  butyrate. 

The  conversion,  however,  is  never  complete,  a  portion,  both  of  the  acid 
and  of  the  alcohol,  remaining  unaltered  in  whatever  proportion  they  may 
be  mixed. 

The  ethereal  salts  of  the  fatty  acids  are,  for  the  most  part,  more  easily 
obtained  by  acting  upon  the  alcohol  with  an  acid  chloride,  or  by  passing 
hydrochloric  acid  gas  into  a  solution  of  the  fatty  acid  in  the  alcohol  : 

C4H7OC1    -f     HOC2H6    ==    HC1    +     C4H70(OC2H6) 
Butyric  Ethyl  Ethyl 

chloride.  alcohol.  butyrate. 

Another  method  very  commonly  adopted  is,  to  distil  a  potassium  salt  of  the 
fatty  acid  with  a  mixture  of  the  alcohol  and  strong  sulphuric  acid.  In 
this  case  an  acid  sulphuric  ether  is  first  formed  (as  ethyl-sulphuric  acid 
from  ethyl  alcohol,  p.  527),  and  this  acts  upon  the  salt  of  the  fatty  acid  in 
the  manner  illustrated  by  the  equation  : 

S02(OH)(OC2H5)   -f   C4H70(OK)    =    C4H70(OC2H6)  +   S02(OH)(OK) 
Ethyl-sulphuric  Potassium  Ethyl  Acid  potassium 

acid.  butyrate.  butyrate.  sulphate. 

The  ethereal  salts  of  the  fatty  acids  are  either  volatile,  oily,  or  syrupy 
liquids,  or  crystalline  solids,  for  the  most  part  insoluble  in  water,  but  sol- 
uble in  alcohol  and  in  ether.  When  distilled  with  potash  or  soda,  they  take 
up  water  and  are  saponified,  that  is  to  say  resolved  into  the  alcohol  and 
acid;  e.  g., 

C4H70(OC2H6)  -f     HOH     =     C4H70(OH)  -f-     C2H5(OH) 

Ethyl  Water.  Butyric  Ethyl 

butyrate.  acid.  alcohol. 

51 


602  MONATOMIC    ACIDS. 

6.  The   fatty  acids   are   strongly  acted  upon  by  the  chlorides,  bromides, 
oxychlorides,  and  oxybromides  of  phosphorus,  yielding  acid  chlorides  and  bro- 
mides, the  phosphorus  being  at  the  same  time  converted  into  phosphorous 
or  phosphoric  acid ;  thus, 

3C2H30(OH)         +         PC13         =         P03H3         +         3C2H3OC1 
Acetic  acid.  Phosphorus          Phosphorus  Acetic 

trichloride.  acid.  chloride. 

3C2H30(OH)        +         PC130       =       P04H3        +        3C2H3OC1 
Acetic  acid.  Phosphorus         Phosphoric  Acetic 

oxybromide.  acid.  chloride. 

C2H30(OH)      +      PC16       =       PC130      4-      HC1     4-     C2H6OC1 
Acetic  acid.         Phosphorus      Phosphoric         Hydro-  Acetic 

pentachloride.  oxychloride.  chloric  acid,     chloride. 

These  acid  chlorides,  are,  for  the  most  part,  oily  liquids,  having  a  pun- 
gent acid  odor ;  they  are  easily  decomposed  by  water,  yielding  the  fatty 
acid  and  hydrochloric"  acid.  This  decomposition  takes  place  also  when 
they  are  exposed  to  the  air :  hence  they  emit  dense  acid  fumes.  They 
react  in  an  exactly  similar  manner  with  alcohols,  as  above  mentioned, 
yielding  hydrochloric  acid  and  a  compound  ether. 

7.  The  chlorides  of  the  acid  radicals,  Cn  H2n_,0,  act  violently  on  ammonia, 
forming  ammonium  chloride,  and  the  amide  corresponding  to  the  acid  from 
which  they  are  derived  ;  e.  a., 

C2H3OC1      4-      2NH3      =       NH4C1      +       NH2(C2H30) 
Acetic  Ammonia.        Ammonium  Acetamide. 

chloride.  chloride. 

8.  The  acid  chlorides,  distilled  with  a  metallic  salt  of  the  corresponding 
acid,  yield  a  metallic  chloride  and  the  oxide  or   anhydride  corresponding  to 
the  acid :  thus, 

C2H3OC1      4-       C2H30(OK)       =      KC1       +       (C2H30)20 

Acetic  Potassium  Acetic 

chloride.  acetate.  oxide. 

In  like  manner,  when  distilled  with  the  potassium  salt  of  another  mon- 
atomic  acid,  they  yield  oxides  or  anhydrides  containing  two  monatomic  acid 
radicals ;  e.  g., 

C2H3OC1      4-      C7H60(OK)       =      KC1      +       C$ 

Acetic  Potassium  Aceto-ben- 

ehloride.  benzoate.  zoic  oxide. 

The  oxides  of  the  fatty  acid  radicals  may  also  be  prepared  by  heating  a 
dry  lead-salt  of  the  acid,  in  a  sealed  tube,  with  carbon  bisulphide  ;  e.  g., 

2Pb{oC2H30     +     CS2     =     2PbS     +     C°2    +     2(C2H30)20 
Lead  acetate.  Acetic 

oxide. 

The  oxides  of  the  fatty  acid  radicals  are  gradually  decomposed  by  water, 
quickly  when  heated,  yielding  two  molecules  of  the  corresponding  acid : 

(C2H30)20        4-        OH2        =        2C2H30(OH) 

Those  containing  two  acid  radicals  yield  one  molecule  of  each  of  the 
Corresponding  acids. 


FATTY   ACIDS.  603 

In  contact  with  alcoholic  oxides  (oxygen  ethers],  the  acid  oxides  are  con- 
verted into  ethereal  salts : 

(C2H30)20        +        (C2H5)?0        =        2C2H30(OC2H6) 
Acetic  oxide.  Ethyl  oxide.  Ethyl  acetate. 

With  alcohols,  in  like  manner,  they  yield  a  mixture  of  a  compound  ether 
with  the  acid : 

(C2H30)20     +     C2H5(OH)     =    C2H30(OC2H6)     +     C.H30(OH) 
Acetic  oxide.        Ethyl  alcohol.         Ethyl  acetate.  Acetic  acid. 

The  acid  oxides  are  decomposed  by  ammonia  gas,  yielding  a  mixture  of 
an  ammonium-salt  with  an  amide : 

(C2H30)20     +     2NH3    =    C2H80(ONH4)     +     NH2C2H30 
Acetic  Ammonia.         Ammonium  Acetamide. 

oxide.  acetate. 

9.  The  fatty  acids,  subjected  to  the  action  of  chlorine  or  bromine,  give  off 
hydrochloric  or  hydrobromic  acid,  and  are  converted  into  substitution-com- 
pounds containing  one  or  more  atoms  of  chlorine  or  bromine  in  place  of 
hydrogen;  but  it  is  only  the  hydrogen  within  the  radical  that  can  be  thus 
exchanged,  the  typic  hydrogen  remaining  unaltered,  so  that  the  number 
of  chlorine  or  bromine-atoms  introduced  in  place  of  hydrogen  is  always 
less  by  at  least  one  than  the  number  of  hydrogen-atoms  in  the  acid : 

C2H30(OH)       -f       C12      =      HC1      +       C2H2C10(OH) 
Acetic  acid.  Chloracetic  acid. 

C2H30(OH)       -f       3C12    =      3HC1     -f  C2C130(OH) 

Acetic  acid.  Trichloracetic 

acid. 

The  iodated  acids  of  the  same  series  (or  rather  their  ethereal  salts)  are 
obtained  by  heating  the  corresponding  bromine-compounds  with  potassium 
iodide : 

C2H2BrO(OC2H6)     +     KI     =     KBr    -f-     C2H2IO(OC2H5) ; 
Ethyl-brom-  Ethyl-iodacetate. 

acetate. 

land  the  ethers  treated  with  potash  yield  potassium  salts  of  the  iodated 
acids,  from  which  the  acids  may  be  obtained  by  decomposition  with  sulphu- 
ric acid. 

The  chlorinated  and  brominated  fatty  acids,  boiled  with  water  and  silver 
oxide,  exchange  the  whole  of  their  chlorine  or  bromine  for  an  equivalent 
quantity  of  hydroxyl,  producing  new  acids,  which  differ  from  the  primi- 
tive acids  by  a  number  of  atoms  of  oxygen  equal  to  the  number  of  atoms 
of  chlorine  or  bromine  present ;  e.  g., 

2C2H3Br02     -f     Ag20     -f     H20     =     2AgBr     +     2C2H403 

Bromacetic  Glycollic 

acid.  acid. 

CJT6Br202     -f     Ag20     +     H20     -f-     2AgBr     +     C4H8O4, 
Dibromo-  Dioxy-bu- 

butyric  acid.  tyric  acid. 

Dichloracetic  and  trichloracetic  acid  are  not  sufficiently  stable  to  exhibit 
this  transformation,  their  molecules  splitting  up  altogether  when  boiled 
with  silver  oxide. 

The  monochlorinated  and  monobrormnated  acids,  subjected  to  the  action 
of  an  alcoholic  solution  of  ammonia  gas,  yield  ammonium  chloride  and  a  new 


604  MONATOMIC    ACIDS. 

acid,  in  which  the  chlorine  or  bromine  is  replaced  by  amidogen.  Thus 
monochloracetic  acid  yields  amidacetic  acid,  or  glycocine : 

C2H3C102     +     2NH3    =    NH4C1     +     C2H3(NH2)02 
Chloracetic  Amidacetic 

acid.  acid. 

There  is  another  way  of  viewing  these  amidated  acids  which  will  be  con- 
sidered hereafter. 

(H          H 

Formic  Acid,  CH202=CHO(OH)=C^  0"  =   \          .—This  acid  occurs  in 

(OH       COOH 

the  concentrated  state  in  the  bodies  of  ants,  in  the  hairs  and  other  parts 
of  certain  caterpillars,  and  in  stinging  nettles.  It  may  be  produced  by  the 
first,  second,  and  fourth  of  the  above-mentioned  general  methods  of  form- 
ing the  fatty  acids — viz.,  by  the  slow  oxidation  of  methyl  alcohol,  or  of 
formic  aldehyde,  in  contact  with  platinum  black,  and  as  a  potassium  salt 
by  heating  hydrocyanic  acid  (hydrogen  cyanide)  with  an  alcoholic  solution 
of  potash : 

HCN    -f     KOH     +     OH2    =    NH3     -f     CHO(OK) 
Hydrogen  Potassium 

cyanide.  formate. 

It  is  also  produced  by  certain  special  reactions — viz :  a.  By  passing  car- 
bon monoxide  over  moist  potassium  hydrate,  the  gas  being  thereby  ab- 
sorbed, and  producing  potassium  formate  : 

CO        +        HOK        =        COH(OK) 

The  absorption  of  the  gas  is  accelerated  by  the  presence  of  a  considerable 
quantity  of  water,  and  still  more  by  alcohol  or  ether. 

/?.  By  distilling  dry  oxalic  acid  mixed  with  sand  or  pumice-stone,  or 
better  with  glycerin: 

C2H204        =         C02        +         CH202 

Oxalic  Carbon  Formic 

acid.  dioxide.  acid. 

The  distillation  of  oxalic  acid  with  glycerine  is  a  very  advantageous 
mode  of  preparing  formic  acid.  The  glycerine  takes  no  part  in  the  decom- 
position, but  appears  to  act  by  preventing  the  temperature  from  rising  too 
high  :  when  oxalic  acid  is  distilled  alone  or  with  sand,  the  greater  part  of 
the  formic  acid  produced  is  resolved  into  water  and  carbon  monoxide. 

y.  By  passing  carbon  dioxide  and  water-vapor  over  potassium  at  a  mod- 
erate heat,  acid  potassium  carbonate  being  formed  at  the  same  time : 

K2    4-     2C02     -f     OH2    =    C03KH     +     CH02K 
Acid  car-         Formate, 
bonate. 

i.  By  the  oxidation  of  sugar,  starch,  gum,  and  organic  substances  in 
general.  A  convenient  mode  of  preparation  is  the  following :  1  part  of 
sugar,  3  parts  of  manganese  dioxide,  and  2  parts  of  water,  are  mixed  in  a 
very  capacious  retort,  or  large  metal  still ;  3  parts  of  oil  of  vitriol,  diluted 
with  an  equal  weight  of  water,  are  then  added,  and  when  the  first  violent 
effervescence  from  the  disengagement  of  carbon  dioxide  has  subsided,  heat 
is  cautiously  applied,  and  a  considerable  quantity  of  liquid  distilled  over. 
This  is  very  impure :  it  contains  a  volatile  oily  matter,  and  some  substance 
which  communicates  a  pungency  not  proper  to  formic  acid  in  that  dilute 
state.  The  acid  liquid  is  neutralized  with  sodium  carbonate,  and  the  re- 


FORMIC    ACID.  605 

suiting  formate  purified  by  crystallization,  and,  if  needful,  by  animal  char- 
coal. From  this,  or  any  other  of  its  salts,  solution  of  formic  acid  may  be 
readily  obtained  by  distillation  with  dilute  sulphuric  acid. 

To  obtain  the  acid  in  its  most  concentrated  state,  the  dilute  acid  is  satu- 
rated with  lead  oxide,  the  liquid  is  evaporated  to  complete  dryness,  and 
the  dried  lead  formate,  reduced  to  fine  powdei*,  is  very  gently  heated  in  a 
glass  tube  connected  with  a  condensing  apparatus,  through  which  a  cur- 
rent of  dry  sulphuretted  hydrogen  gas  is  transmitted.  It  forms  a  clear, 
colorless  liquid,  which  fumes  slightly  in  the  air,  has  an  exceedingly  pene- 
trating odor,  boils  at  98«3°  C.  (210°  F.),  and  crystallizes  in  large  brilliant 
plates  when  cooled  below  0°.  The  specific  gravity  of  the  acid  is  1  235  ;  it 
mixes  with  water  in  all  proportions:  the  vapor  is  inflammable,  and  burns 
with  a  blue  flame.  Concentrated  formic  acid  is  extremely  corrosive,  at- 
tacking the  skin,  and  forming  a  blister  or  an  ulcer,  painful  and  difficult  to 
heal. 

Formic  acid  mixes  with  water  in  all  proportions.  The  aqueous  acid  has 
an  odor  and  taste  much  resembling  those  of  acetic  acid :  it  reddens  litmus 
strongly,  and  decomposes  alkaline  carbonates  with  effervescence.  Formic 
acid  likewise  dissolves  readily  in  alcohol,  being  partly  converted  into  ethyl 
formate. 

Formic  acid  is  a  powerful  reducing  agent.  It  may  be  readily  distin- 
guished from  acetic  acid  by  heating  it  with  solution  of  silver  nitrate;  the 
metal  is  thus  reduced,  sometimes  in  the  pulverulent  state,  sometimes  as  a 
specular  coating  on  the  glass  tube,  and  carbon  dioxide  is  evolved.  Mer- 
curic chloride  is  reduced  by  formic  acid  to  calomel.  Formic  acid  heated 
with  oil  of  vitriol  splits  up  into  water  and  carbon  monoxide,  CH202=OH2 
+CO. 

Chlorine  converts  it  into  hydrochloric  acid  and  carbon  dioxide: 

CH202        -f         C12        =        2HC1         -f         C02 

Formic  acid  heated  with  strong  bases  is  converted  into  oxalic  acid,  with 
disengagement  of  hydrogen: 

2CH202     -f     BaO     =     C2Ba04    -f     H2     +     OIIr 
Formic          Baryta.          Barium 
acid.  oxalate. 

Formates.  —  The  composition  of  these  salts  is  expressed  by  the  formulas, 
•Cll(>aM,  (CHOa),M//,  (CH02)3M"',  &c.,  according  to  the  equivalent  value 
of  the  metal  or  other  positive  radical  contained  in  them.  They  are  all 
soluble  in  water:  their  solutions  form  dark-red  mixtures  with  ferric  salts. 
When  distilled  with  strong  sulphuric  acid  they  give  off  acid  carbon  monox- 
ide, arid  leave  a  residue  of  sulphate.  The  formates  of  the  alkali-metals 
heated  with  the  corresponding  salts  of  other  fatty  acids,  yield  a  carbonate 
and  an  aldehyde  (p.  GOO). 

Sodium  formate  crystallizes  in  rhombic  prisms  containing  CH02Na.  Aq.  It 
reduces  many  metallic  oxides  when  fused  with  them.  Potassium  formate, 
CH02K,  is  difficult  to  crystallize,  on  account  of  its  great  solubility.  Ammo- 
nium formate  crystallizes  in  square  prisms:  it  is  very  soluble,  and  is  decom- 
posed at  high  temperatures  into  hydrocyanic  acid  ami  water,  the  elements 
of  which  it  contains:  CII02NH4=20II2+CNH.  The  formates  of  barium, 
strontium,  calcium,  and  magnesium  form  small  prismatic,  easily  soluble 
crystals.  Lead  formate  crystallizes  in  small,  diverging,  colorless  needles, 
which  require  for  solution  40  parts  of  cold  water.  The  manganous,  ferrous, 
zinc,  nickel,  and  cobalt  formates  are  also  crystallizable.  Cupric  formate  is  very 
beautiful,  constituting  bright-blue  rhombic  prisms  of  considerable  magni- 
tude. Si/r,'/-  format*'  is  white,  but  slightly  soluble,  and  decomposed  by  the 
least  elevation  of  temperature. 


606  MONATOMIC    ACIDS. 

Methyl  formate,  CH02CH3,  isomeric  with  acetic  acid,  is  prepared  by  heat- 
ing in  a  retort  equal  weights  of  neutral  methyl  sulphate  and  sodium  for- 
mate. It  is  a  very  volatile  liquid,  lighter  than  water,  boiling  between 
36°  and  38°. 

Ethyl  formate,  CH02C2H5,  isomeric  with  methyl  acetate  and  propionic  acid 
(p.  475),  is  prepared  by  distilling  a  mixture  of  7  parts  of  dry  sodium  for- 
mate, 10  of  oil  of  vitriol,  and  6  of  strong  alcohol.  The  formic  ether, 
separated  by  the  addition  of  water  to  the  distilled  product,  is  agitated  with 
a  little  magnesia,  and  left  for  several  days  in  contact  with  calcium  chloride. 
Ethyl  formate  is  colorless,  has  an  aromatic  odor,  a  density  of  0-915,  and 
boils  at  56°  C.  (133°  F.).  Water  dissolves  it  to  a  small  extent. 

( CH3       CH3 

Acetic  Acid,  C2H402  =  C2H30(OH),  or  COCH3(OH)  =  C I O"  =•  I          ._ 

I  OH        COOH 

This  acid  is  found  in  small  quantities  in  the  juices  of  plants  and  in  animal 
fluids.  It  may  be  produced  by  either  of  the  first  five  general  methods  of 
formation  given  on  pages  598,  599,  and  in  particular  by  the  slow  oxidation 
of  alcohol.  When  spirit  of  wine  is  dropped  upon  platinum  black,  the 
oxygen  condensed  in  the  pores  of  the  latter  reacts  so  powerfully  upon  the 
alcohol  as  to  cause  its  instant  inflammation.  When  the  spirit  is  mixed  with 
a  little  water,  and  slowly  dropped  upon  the  finely  divided  metal,  oxidation 
still  takes  place,  but  with  less  energy,  and  vapor  of  acetic  acid  is  abun- 
dantly evolved.  In  all  these  modes  of  formation,  the  acetic  acid  is  ultimately 
producible  from  inorganic  materials.  It  is  also  formed  by  the  action  of 
nascent  hydrogen  on  trichloracetic  acid,  which  may  itself  be  produced  from 
inorganic  materials.  Lastly,  acetic  acid  is  obtained,  together  with  many 
other  products,  in  the  destructive  distillation  of  wood  and  other  vegetable 
substances. 

Preparation.  —  1.  Dilute  alcohol,  mixed  with  a  little  yeast,  or  almost  any 
azotized  organic  matter  susceptible  of  putrefaction,  and  exposed  to  the  air, 
speedily  becomes  oxidized  to  acetic  acid.  Acetic  acid  is  thus  manufactured 
in  Germany,  by  suffering  such  a  mixture  to  flow  over  wood-shavings  steeped 
in  a  little  vinegar,  contained  in  a  large  cylindrical  vessel  through  which  a 
current  of  air  is  made  to  pass.  The  greatly  extended  surface  of  the  liquid 
expedites  the  change,  which  is  completed  in  a  few  hours.  No  carbonic  acid 
is  produced  in  this  reaction. 

The  best  vinegar  is  made  from  wine  by  spontaneous  acidification  in  a 
partially  filled  cask  to  which  the  air  has  access.  Vinegar  is  first  introduced 
into  the  empty  vessel,  and  a  quantity  of  wine  added ;  after  some  days,  a 
second  portion  of  wine  is  poured  in,  and  after  similar  intervals,  a  third  and 
a  fourth.  When  the  whole  has  become  vinegar,  a  quantity  is  drawn  off 
equal  to  that  of  the  wine  employed,  and  the  process  is  recommenced.  The 
temperature  of  the  building  is  kept  up  to  30°  C.  (86°  F.).  Such  is  the  plan 
adopted  at  Orleans.*  In  England,  vinegar  is  prepared  from  a  kind  of  beer 
made  for  the  purpose.  The  liquor  is  exposed  to  the  air  in  half  empty 
casks,  loosely  stopped,  until  acidification  is  complete.  Frequently  a  little 
sulphuric  acid  is  afterwards  added,  with  the  view  of  checking  further 
decomposition,  or  mothering,  by  which  the  product  would  be  spoiled. 

When  dry,  hard  wood,  as  oak  and  beech,  is  subjected  to  destructive  dis- 
tillation at  a  red  heat,  acetic  acid  is  found  among  the  liquid  condensable 
products  of  the  operation.  The  distillation  is  conducted  in  an  iron  cylinder 
of  large  dimensions,  to  which  a  worm  or  condenser  is  attached;  a  sour 
watery  liquid,  a  quantity  of  tar,  and  much  inflammable  gas  pass  over, 
while  charcoal  of  excellent  quality  remains  in  the  retort.  The  acid  liquid 
is  subjected  to  distillation,  the  first  portion  being  collected  apart  for  the 

*  Dumas,  Chiinie  applique  aux  Arts,  vi.  5o7. 


ACETIC    ACID.  607 

preparation  of  wood-spirit.  The  remainder  is  saturated  with  lime,  concen- 
trated by  evaporation,  and  mixed  with  the  solution  of  sodium  sulphate; 
calcium  sulphate  is  thereby  precipitated,  while  the  acetic  acid  is  transferred 
to  the  soda.  The  filtered  solution  is  evaporated  to  its  crystallizing  point; 
and  the  crystals  are  drained  as  much  as  possible  from  the  dark,  tarry 
mother-liquor,  and  deprived  by  heat  of  their  combined  water.  The  dry  salt 
is  then  cautiously  fused,  by  which  the  last  portions  of  tar  are  decomposed 
or  expelled :  it  is  then  re-dissolved  in  water,  and  re-crystallized.  Pure 
sodium  acetate,  thus  obtained,  readily  yields  acetic  acid  by  distillation  with 
sulphuric  acid. 

The  strongest  acetic  acid  is  prepared  by  distilling  finely  powdered  anhy- 
drous sodium  acetate  with  three  times  its  weight  of  concentrated  oil  of 
vitriol.  The  liquid  is  purified  by  rectification  from  sodium  sulphate  acci- 
dentally thrown  up,  and  exposed  to  a  low  temperature.  Crystals  of  pure 
acetic  acid,  C2H402,  then  form  in  large  quantity :  they  may  be  drained  from 
the  weaker  fluid  portion,  and  suffered  to  melt.  Below  15-5°  C.  (GO0  F.) 
this  substance,  often  called  glacial  acetic  acid,  forms  large,  colorless,  trans- 
parent crystals,  which  above  that  temperature  fuse  to  a  thin,  colorless 
liquid,  of  exceedingly  pungent  and  well-known  odor:  it  raises  blisters  on 
the  skin.  It  is  miscible  in  all  proportions  with  water,  alcohol,  and  ether, 
and  dissolves  camphor  and  several  resins.  When  diluted  it  has  a  pleasant 
acid  taste.  Glacial  acetic  acid  in  the  liquid  state  has  a  density  of  1-063, 
and  boils  at  120°  C.  (248°  P.).  Its  vapor  is  inflammable,  and  exhibits  the 
variations  of  density  noticed  at  page  461.  At  300°  C.  (572°  F.),  or  above, 
it  is  2-08  compared  with  air,  er  30°  compared  with  hydrogen,  agreeing  ex- 
actly with  the  theoretical  density,  which  is  half  the  molecular  weight ;  but 
at  temperatures  near  the  boiling  point  it  is  considerably  greater,  being  2-90 
at  140°  C.  (284°  F.),  and  3-20  at  125°  C.  (257°  F.)  (referred  to  air). 

Dilute  acetic  acid,  or  distilled  vinegar,  used  in  pharmacy,  should  always 
be  carefully  examined  for  copper  and  lead ;  these  impurities  are  contracted 
from  the  metallic  vessel  or  condenser  sometimes  employed  in  the  process. 
The  strength  of  any  sample  of  acetic  acid  cannot  be  safely  inferred  from 
its  density,  but  it  is  easily  determined  by  observing  the  quantity  of  dry 
sodium  carbonate  necessary  to  saturate  a  known  weight  of  the  liquid. 

Acetic  acid  exhibits  all  the  reactions  of  the  fatty  acids  in  general  (pp. 
601-604).  The  acid  itself  does  not  readily  conduct  the  electric  current, 
but  a  solution  of  potassium  acetate  is  decomposed  by  electrolysis,  with  for- 
mation of  dimethyl  or  ethane: 

CII8 
2  |  +     OH2     =     C2H6    +     II2    +     C02    +     CO(OK)2 

COOK 
Potassium  Ethane.  Potassium 

acetate.  carbonate. 

Acetic  acid  is  not  attacked  by  nitric  acid,  but  periodic  acid  converts  it  by 
oxidation  into  formic  acid  and  carbon  dioxide,  being  itself  reduced  to 
iodic  acid  or  even  to  free  iodine: 

C2H402    +     03    =    CII202     +     C02     +     OH2. 

Potassium  acetate  distilled  with  arscnious  oxide  gives  off  a  highly  inflam- 
mable and  characteristically  fetid  oil,  consisting  chiefly  of  arsendimethyl 
or  cacodyl,  As2(CH3)4. 

Acetates. — Acetic  acid  forms  a  large  number  of  highly  important  salts, 
rc]>n-sciiu-(l  by  the  formula},  (yis(),M,  (C2HSO2)2M//,  or  (<V l3<y,.M '",  ac- 
cording to  the  equivalent  value  of  the  metals  contained  in  them.  Being  a 
monobasic  acid,  it  cannot  form  any  acid  salts  properly  so  called,  that  is  by 


608  MO^ATOMIC    ACIDS. 

replacement  of  a  part  of  its  typic  hydrogen  (p.  282) ;  but  the  normal 
acetates  of  the  alkali-metals  can  take  up  a  molecule  of  acetic  acid,  just  as 
they  take  up  water  of  crystallization,  forming  salts  called  acid  acetates  or 
diacetates,  C2H302M  .  C2H402.  There  are  also  basic  acetates  formed  by  the 
union  of  a  molecule  of  a  normal  acetate  with  a  molecule  of  metallic  oxide 
or  hydrate. 

POTASSIUM  ACETATES. — The  normal  salt,  C2H302K,  crystallizes  with  great 
difficulty :  it  is  generally  met  with  as  a  foliated,  white,  crystalline  mass, 
obtained  by  neutralizing  potassium  carbonate  with  acetic  acid,  evaporating 
to  dryness,  and  heating  the  salt  to  fusion.  It  is  extremely  deliquescent, 
and  soluble  in  water  and  alcohol:  the  solution  is  usually  alkaline  from  a 
little  loss  of  acid  by  the  heat  to  which  it  has  been  subjected.  From  the 
alcoholic  solution,  potassium  carbonate  is  thrown  down  by  a  stream  of  car- 
bon dioxide. 

The  acid  salt,  C2H302K  .  C2H402,  is  formed  by  evaporating  a  solution  of 
the  neutral  salt  in  excess  of  acetic  acid,  and  crystallizes  by  slow  evapora- 
tion in  long  flattened  prisms.  It  is  very  deliquescent,  and  decomposes  at 
200°,  giving  off  crystallizable  acetic  acid. 

SODIUM  ACETATE,  C2H302Na  .  3  Aq. — The  mode  of  preparation  of  this  salt 
on  the  large  scale  has  been  already  described  :  it  forms  large,  transparent, 
colorless  crystals,  derived  from  a  rhombic  prism,  which  are  easily  ren- 
dered anhydrous  by  heat,  effloresce  in  dry  air,  and  dissolve  in  3  parts  of 
cold,  and  in  an  equal  weight  of  hot  water:  it  is  also  soluble  in  alcohol. 
The  taste  of  this  salt  is  cooling  and  saline.  The  dry  salt  melts  at  288°  C. 
(550°  F.),  and  begins  to  decompose  at  315°  C.  (600°  F.). 

AMMONIUM  ACETATES. — The  neutral  acetate,  C2H302NH4,  is  a  white  odor- 
less salt  obtained  by  saturating  glacial  acetic  acid  with  dry  ammonia  gas. 
It  is  very  difficult  to  obtain  in  the  crystalline  form,  for  its  aqueous  solution, 
when  evaporated,  gives  off  ammonia  and  leaves  the  acid  salt.  When  dis- 
tilled with  phosphoric  oxide,  it  loses  2  molecules  of  water,  and  gives  off 
ethenyl  nitrile  or  acetonitrile,  (C2H8)"'N  =  C2H302NH4  — 20H2.  The 
aqueous  solution,  known  in  the  Pharmacopoeia  as  Spiritus  Mindereri,  is  pre- 
pared by  saturating  aqueous  acetic  acid  with  ammonia  or  ammonium  car- 
bonate. 

The  acid  salt,  C2H302NH4 .  C2H402,  is  obtained  as  a  crystalline  sublimate 
by  heating  powdered  sal-ammoniac  with  potassium  or  calcium  acetate, 
ammonia  being  given  off  at  the  same  time ;  also  as  a  radiated  crystalline 
mass  by  evaporating  the  aqueous  solution  of  the  neutral  salt. 

The  acetates  of  barium,  strontium,  and  calcium  are  very  soluble,  and  can 
be  procured  in  crystals ;  magnesium  acetate  crystallizes  with  difficulty. 

ALUMINIUM  ACETATES. — This  salt  is  very  soluble  in  water,  and  dries  up 
in  the  vacuum  of  the  air-pump  to  a  gummy  mass  without  trace  of  crystal- 
lization. If  foreign  salts  are  present,  the  solution  of  the  acetate  becomes 
turbid  on  heating,  from  the  separation  of  a  basic  compound,  which  redis- 
solves  as  the  liquid  cools.  Aluminum  acetate  is  much  employed  in  calico 
printing:  it  is  prepared  by  mixing  solutions  of  lead  acetate  and  alum,  and 
filtering  from  the  insoluble  lead  sulphate.  The  liquid  is  thickened  with 
gum  or  other  suitable  material,  and  with  it  the  design  is  impressed  upon 
the  cloth  by  a  wood-block,  or  by  other  means.  Exposure  to  a  moderate 
degree  of  heat  drives  off  the  acetic  acid,  and  leaves  the  alumina  in  a  state 
capable  of  entering  into  combination  with  the  dye-stuff. 

Some  very  interesting  researches  on  aluminum  acetate  have  been  pub- 
lished by  the  late  Mr.  Walter  Crum.*  The  solution  obtained  by  decompos- 

*  Chcm.  Soc.  Quar.  Jour.  vi.  216. 


ACETATES.  609 

ing  aluminum  sulphate,  (S04)3A12,  with  lead  acetate,  may  be  supposed  to 
contain  neutral  aluminium  acetate,  (C2H302)3A1///.  This  salt  cannot,  how- 
ever, be  obtained  in  the  dry  state.  It'  the  solution  be  rapidly  evaporated 
at  low  temperatures,  by  being  spread  in  thin  layers  on  glass  or  porcelain, 
a  basic  soluble  acetate  is  obtained,  having  the  composition  4(C2II302)3A1///. 
A1203 .  (5  aq. ;  but  if  the  solution  be  left  to  stand,  or  submitted  to  the  action 
of  heat,  insoluble  basic  salts  are  precipitated,  differing  in  composition  from 
the  former  only  by  containing  3  or  8-J-  molecules  of  water  instead  of  four. 

The  soluble  aluminum  acetate,  when  exposed  in  a  dilute  solution  to  the 
temperature  of  boiling  water  for  several  days,  undergoes  a  very  remarkable 
change,  the  whole,  or  nearly  the  whole,  of  the  acetic  acid  being  expelled 
by  the  action  of  heat,  and  a  peculiar  soluble  modification  of  alumina  (al- 
ready described  under  ALUMINIUM,  p.  335),  remaining  in  solution. 

Manganese  acetate  forms  colorless,  rhombic,  prismatic  crystals,  permanent 
in  the  air.  Ferrous  acetate  crystallizes  in  small,  greenish-white  needles, 
very  prone  to  oxidation ;  both  salts  dissolve  freely  in  water.  Ferric  acetate 
is  a  dark  brownish-red,  uncrystallizable  liquid,  of  powerful  astringent 
taste.  Cobalt  acetate  forms  a  violet-colored,  crystalline,  deliquescent  mass. 
The  nickel  salt  separates  in  green  crystals,  which  dissolve  in  6  parts  of 
water. 

LEAD  ACETATES. — The  normal  salt,  (C2H302)2Pb//.3  aq.,  is  prepared  on  a 
large  scale  by  dissolving  litharge  in  acetic  acid:  it  may  be  obtained  in  col- 
orless, transparent,  prismatic  crystals,  but  is  generally  met  with  in  com- 
merce as  a  confusedly  crystalline  mass,  somewhat  resembling  loaf-sugar. 
From  this  circumstance  and  from  its  sweet  taste,  it  is  often  called  sugar  of 
lead.  The  crystals  are  soluble  in  about  1^  parts  of  cold  water,  effloresce  in 
dry  air,  and  melt  when  gently  heated  in  their  water  of  crystallization;  the 
latter  is  easily  driven  off,  and  the  anhydrous  salt  obtained,  which  melts, 
and  afterward  decomposes,  at  a  high  temperature.  Acetate  of  lead  is  sol- 
uble in  alcohol.  The  aqueous  solution  has  an  intensely  sweet,  and  at  the 
same  time  astringent  taste,  and  is  not  precipitated  by  ammonia.  It  is  an 
article  of  great  value  to  the  chemist. 

Basic  Acetates  (Subacetates]  of  Lead. — A  sesquibasic  acetate,  2(C2H302)2Pb//. 
PV'O,  is  produced  when  the  neutral  anhydrous  salt  is  so  far  decomposed 
by  heat  as  to  become  converted  into  a  porous  white  mass,  decomposable 
only  at  a  much  higher  temperature.  It  is  soluble  in  water,  and  separates 
from  the  solution  evaporated  to  a  syrupy  consistence  in  the  form  of  crys- 
talline scales.  A  triplumbic  acetate,  (C2H302)2Pb//  .  2Pb//0,  is  obtained  by 
digesting  at  a  moderate  heat,  1  parts  of  finely  powdered  litharge,  6  parts 
of  lead  acetate,  and  30  parts  of  water;  or,  by  mixing  a  cold  saturated  solu- 
tion of  neutral  lead  acetate  with  a  fifth  of  its  volume  of  caustic  ammonia, 
and  leaving  the  Avhole  some  time  in  a  covered  vessel.  The  salt  separates 
in  minute  needles  containing  one  molecule  of  water.  The  solution  of  basic 
acetate  prepared  by  the  first  method  is  known  in  pharmacy  under  the 
name  of  Goulard  water.  There  is  also  a  sexplumbic  acetate,  (C2H302)2Pb//. 
5Pb/xO,  formed  by  adding  a  great  excess  of  ammonia  to  a  solution  of  nor- 
mal lead  acetate,  or  by  digesting  the  normal  salt  with  a  large  quantity  of 
oxide.  It  is  a  white,  slightly  crystalline  substance,  insoluble  in  cold,  and 
but  little  soluble  in  boiling  water.  The  solutions  of  the  basic  lead  acetates 
have  a  strong  alkaline  reaction,  and  absorb  carbonic  acid  with  the  greatest 
avidity,  becoming  turbid  from  precipitation  of  basic  carbonate. 

CUPRIC  ACETATES. — The  normal  acetate.  (OJT^O./UOu.  aq.,  is  prepared  by 
dissolving  verdigris  in  hot  acetic  acid,  and  leaving  the  filtered  solution  to 
cool.  It,  forms  beautiful  dark-green  crystals,  which  dissolve  in  14  parts  of 
cold  and  5  parts  of  boiling  water,  and  are  also  soluble  in  alcohol.  A  solu- 


610  MONATOMIC   ACIDS. 

tion  of  this  salt,  mixed  with  sugar  and  heated,  yields  cupric  oxide  in  the 
form  of  minute  red  octohedral  crystals :  the  residual  copper  solution  is  not 
precipitated  by  an  alkali.  Cupric  acetate  yields,  by  destructive  distilla- 
tion, strong  acetic  acid  containing  acetone  and  contaminated  with  copper. 
The  salt  is  sometimes  called  distilled  verdigris,  and  is  used  as  a  pigment. 

Basic  Cupric  Acetates.—  Common  verdigris,  made  by  spreading  the  marc 
of  grapes  upon  plates  of  copper  exposed  to  the  air  for  several  weeks,  or  by 
substituting,  with  the  same  view,  pieces  of  cloth  dipped  in  crude  acetic  acid, 
is  a  mixture  of  several  basic  cupric  acetates  which  have  a  green  or  blue 
color.  One  of  these,  2(C2H302)2Cu// .  CuO  .  6  aq.,  is  obtained  by  digesting 
the  powdered  verdigris  in  warm  water,  and  leaving  the  soluble  part  to 
spontaneous  evaporation.  It  forms  a  blue,  crystalline  mass,  but  little  sol- 
uble in  cold  water.  When  boiled,  it  deposits  a  brown  powder,  which  is  a 
subsalt  with  large  excess  of  base.  The  green  insoluble  residue  of  the  ver- 
digris contains  (C2H302)2Cu  .  2CuO  .  3  aq. ;  it  may  be  formed  by  digesting 
normal  cupric  acetate  with  the  hydrated  oxide.  By  ebullition  with  water 
it  is  resolved  into  normal  acetate  and  the  brown  basic  salt. 

SILVER  ACETATE,  C2H302Ag,  is  obtained  by  mixing  potassium  acetate 
with  silver  nitrate,  and  washing  the  precipitate  with  cold  water  to  remove 
the  potassium  nitrate.  It  crystallizes  from  a  warm  solution  in  small  color- 
less needles,  which  have  but  little  solubility  in  the  cold. 

Mercurous  acetate  forms  small  scaly  crystals,  which  are  as  feebly  soluble 
as  those  of  acetate  of  silver.  Mercuric  acetate  dissolves  with  facility. 

METHYL  ACETATE,  C2H302CH3,  occurs  in  crude  wood-spirit.  It  is  prepared 
by  distilling  2  parts  of  methyl  alcohol  with  1  part  of  glacial  acetic  acid  and 
1  part  of  sulphuric  acid,  or  I  part  of  methyl  alcohol  with  1  part  of  potas- 
sium acetate  and  2  parts  of  sulphuric  acid.  When  purified  by  rectification 
over  calcium  chloride  and  quick-lime,  it  forms  a  colorless  fragrant  liquid 
of  sp.  gr.  0-9562  at  0°,  boiling  at  55°  or  56°  C.  (13l°-133°  F.).  It  dissolves 
in  water,  and  mixes  in  all  proportions  with  alcohol  and  ether. 

ETHYL  ACETATE,  C2H302C2H5,  may  be  prepared  by  heating  together  in  a 
retort  3  parts  of  potassium  acetate,  3  parts  of  strong  alcohol,  arid  2  parts 
of  oil  of  vitriol.  The  distilled  product  is  mixed  with  water,  to  separate  the 
alcohol,  digested  first  with  a  little  chalk,  and  afterwards  with  fused  calcium 
chloride,  and,  lastly,  rectified.  The  pure  ether  is  an  exceedingly  fragrant 
limpid  liquid:  it  has  a  density  of  0-890,  and  boils  at  73-8°  C.  (165°  F.). 
Alkalies  decompose  it  in  the  manner  already  mentioned  (p.  601).  When 
treated  with  ammonia,  it  yields  acetamide,  NH2C2H30. 

AMYL  ACETATE,  C2H302C5H1P  prepared  in  a  similar  manner,  boils  at  133° 
C.  (272°  F.).  It  possesses  in  a  remarkable  manner  the  odor  of  the  Jar- 
gonelle pear,  and  is  now  manufactured  on  a  large  scale  for  flavoring  liquors 
and  confectionery. 

ETHENE  ACETATES.  —  These  compounds  may  be  derived  from  ethene  al- 
cohol (glycol)  by  substitution  of  one  or  two  equivalents  of  acetyl  for  hydro- 
gen. The  monacetatc,  (C^)"/  jjS ^  Q,  is  produced  by  heating  ethene  di- 

bromide  with  an  alcoholic  solution  of  potassium  acetate.  The  product  is  dis- 
tilled, the  portion  coming  over  at  1 82°  C.  (360°  F.)  being  kept  separate.  It  is 
a  colorless,  oily  liquid,  miscible  in  every  proportion  with  water  or  alcohol. 
Hydrochloric  acid  gas  passed  into  ethene  monacetate  converts  it  into  ethene 

( r^i 
acetochloride,  or  glycolic  chloracetin,  C2H4<  x|L  „  Q,  which  is  precipitated, 

on  addition  of  water,  as  an  oily  liquid  boiling  at'lls0  C.  (293°  F.).     Treat- 


ACETIC    ETHERS.  611 

ment  with  potash  decomposes  it  into  ethene  oxide,  potassium  acetate,  and 
potassium  chloride. 

f  OC  H  O 
Ethene  diacetate,  C2H4  -j  Q(j2^3Q>  is  prepared  by   digesting  a  mixture  of 

ethene  dibromide,  silver  acetate,  and  glacial  acetic  acid  in  the  water-bath, 
and  exhausting  the  digested  mass  with  ether.  On  distilling  the  ethereal 
solution,  the  ether  first  passes  over,  then  the  acetic  acid,  and  lastly,  when 
the  temperature  has  reached  187°  C.  (368°  F.),  ethene  diacetate.  It  is  a 
colorless,  neutral  liquid,  of  sp.  gr.  1-128,  at  0°;  soluble  in  7  parts  of  water 
and  in  every  proportion  in  alcohol  and  ether. 

PROPENYL  OR  GLYCERYL  ACETATES  ;  OR  ACETINS.  —  These  ethers  are  de- 
rived from  propenyl  alcohol  (glycerin)  by  substitution  of  1,  2,  or  3  equiva- 
lents of  acetyl  for  hydrogen.  The  formula  of  glycerin  being  (C3H6)///  OH3, 
those  of  the  three  acetins  are  : 

Monoacetin  .  .  .  (C3H6)'"(OH)2(OC2H80) 
Diacetin  .  .  .  (C3H5)'"(OH)(OC2H30)2 
Triacetin  ....  (C8H6)'"(OC2HS0)8 

They  are  oily  liquids,  produced  by  heating  glycerin  and  acetic  acid  to- 
gether, in  various  proportions,  in  sealed  tubes. 

ACETIC  CHLORIDE  OR  ACETYL  CHLORIDE,  C2H3OC1.  —  This  compound,  which 
has  the  constitution  of  acetic  acid  with  chlorine  substituted  for  hydroxyl, 
is  produced,  as  already  observed  (p.  602),  by  the  action  of  phosphorus  tri- 
chloride, pentachloride,  or  oxychloride  on  glacial  acetic  acid.  The  pro- 
duct heated  with  water  and  dilute  soda-solution,  to  remove  phosphorus 
oxychloride  and  hydrochloric  acid,  and  then  rectified,  yields  acetic  chlo- 
ride as  a  colorless  liquid,  having  a  suffocating  odor  and  emitting  dense  fumes 
of  hydrochloric  acid  in  contact  with  the  air.  It  is  heavier  than  water,  boils 
at  55°  C.  (131°  F.),  and  is  decomposed  by  water  and  alkaline  solutions, 
yielding  hydrochloric  and  acetic  acids. 

ACETIC  OXIDE  OR  ANHYDRIDE,  C4H603  =  (C2H30)20,  sometimes  called 
Anhydrous  acetic  acid.  —  This  compound  is  obtained: 

1.  By  the  action  of  acetyl  chloride  on  potassium  or  sodium  acetate: 

C2H30(ONa)     -f     C2H3OC1    =    NaCl     -f     (C2H30)20. 

2.  By  heating  sodium  acetate  with  benzoyl  chloride,  C7H5OC1,  whereby 
benzo-acetic  oxide  is  formed  in  the  first  instance,  and  subsequently  resolved 
into  acetic  and  benzoic  oxides,  the  former  distilling  over,  while  the  latter 
remains  : 

C2H30(ONa)      +      C7H5OC1      =      NaCl      +      ^n 

Sodium  acetate.  Benzoyl  Benzo-acetic 

chloride.  oxide. 

and: 


(C2H30)20          +          (C7H60)20 

Benzo-acetic  Acetic  Benz.oic 

oxide.  oxide.  oxide. 

Acetic  oxide  is  a  heavy  oil  which  dissolves  slowly  in  water,  being  gradu- 
ally converted  into  acetic  acid  : 

(C2H30)20  -|-  OH2  ==  2C2H3C(OH). 


612  MONATOMIC   ACIDS. 


Acids  derived  from  Acetic  Acid  by  Substitution. 

CHLORACETIC  ACIDS.—  The  three  acids,  C2H3C102,  C2H2C1202,  and  C2HC1302, 
are  produced  by  the  action  of  chlorine  on  acetic  acid  in  sunshine ;  the 
second,  however,  is  formed  in  small  quantity  only,  the  first  or  the  third  be- 
ing produced  in  greatest  abundance  according  as  the  acetic  acid  or  the 
chlorine  is  in  excess. 

Monochloracetic  acid,  C2H2C10(OH),  is  produced,  according  to  R.  Hoff- 
mann, by  the  action  of  chlorine  on  boiling  glacial  acetic  acid  in  sunlight. 
Dr.  H.  Miiller  finds  that  the  formation  of  monochloracetic  acid  is  facilitated 
by  dissolving  a  little  iodine  in  the  hydrated  acetic  acid,  and  passing  a  stream 
of  chlorine  through  the  boiling  solution.  On  submitting  the  products  of 
this  reaction  to  repeated  distillation,  a  substance  is  obtained  boiling  at 
186°  C.  (367°  F.),  and  solidifying  to  a  crystalline  mass  which  melts  at  64° 
C.  (147°  F.)  and  dissolves  with  facility  in  water.  This  acid,  when  heated 
with  potash,  is  converted  into  potassium  glycollate  (p.  604): 

C2H3C102     +     2KHO     =     KC1     -f     C2H303K     -f     OH2 
Chloracetic  Potassium 

acid.  glycollate. 

Dichloracetic  acid,  C2HC120(OH),  is  produced,  together  with  the  preceding 
compound,  by  the  action  of  chlorine  and  iodine  on  boiling  acetic  acid,  and 
is  found  in  that  portion  of  the  product  which  boils  above  188°  C.  (370°  F.). 

According  to  Maumene*,*  it  may  be  obtained  by  exposing  monochlor- 
acetic acid  in  large  flasks  to  the  action  of  dry  chlorine  (5  atoms  of  chlorine  to 
3  molecules  of  chloracetic  acid)  for  twenty-four  hours,  warming  the  product  to 
expel  hydrochloric  acid,  and  then  distilling.  At  ordinary  temperatures  it 
is  a  liquid  having  a  specific  gravity  of  1-5216  at  15°  C.  (59°  F.),  and  boiling 
at  105°  C.  (221°  F.).  According  to  Miiller,  it  remains  liquid  when  cooled  ; 
but  according  to  Maumene,  it  crystallizes  in  rhombohedral  plates.  It  forms 
a  soluble  silver  salt,  C2HCl202Ag,  which  is  decomposed  when  its  solution  is 
heated  with  silver  oxide  to  75°  or  80°,  giving  off  a  mixture  of  carbon  mon- 
oxide and  dioxide : 

2C2HCl202Ag  -f  3Ag20  =  2CO  +  2C02  -f  4AgCl  +  2Ag2  -f  OH2. 

Trichlor acetic  acid,  C2C130(OH). —  Discovered  by  Dumas.  When  a  small 
quantity  of  crystallizable  acetic  acid  is  introduced  into  a  bottle  of  dry 
chlorine  gas,  and  the  whole  exposed  to  the  direct  solar  rays  for  several 
hours,  the  interior  of  the  vessel  is  found  coated  with  a  white  crystalline 
substance,  which  is  a  mixture  of  trichloracetic  acid  with  a  small  quantity 
of  oxalic  acid.  The  liquid  at  the  bottom  contains  the  same  substances,  to- 
gether with  the  unaltered  acetic  acid.  Hydrochloric  and  carbonic  acid 
gases  are  at  the  same  time  produced,  together  with  a  suffocating  vapor,  re- 
sembling carbonyl  chloride.  The  crystalline  matter  is  dissolved  out  by  a 
small  quantity  of  water  added  to  the  liquid  contained  in  the  bottle,  and  the 
whole  is  placed  in  the  vacuum  of  the  air-pump,  with  capsules  containing 
fragments  of  caustic  potash  and  concentrated  sulphuric  acid.  The  oxalic 
acid  is  first  deposited,  and  afterward  the  trichloracetic  acid,  in  beautiful 
rhombic  crystals.  If  the  liquid  refuses  to  crystallize,  it  may  be  distilled 
with  a  little  anhydrous  phosphoric  acid,  and  then  evaporated.  The  crys- 
tals are  spread  upon  bibulous  paper  to  drain,  and  dried  in  a  vacuum. 
The  reaction  probably  takes  place  according  to  the  equation : 

4C2H402    -f     11C12    =    2C2HC1302    -f     C2H204    +     10HC1 
Acetic  acid.  '  Trichloracetic         Oxalic 

acid.  acid. 

+     2CHC13 
Chloroform. 

*  Bull.  S0c.  Chim.  de  Paris,  [2],  i.  417. 


ACETIC   ACID.  613 

The  chloroform  is  converted,  by  the   further  action   of  the  chlorine,  into 
carbon  tetrachloride,  CC14  (Maumene"). 

Trichloracetic  acid  may  also  be  produced  synthetically,  viz.,  by  the  ac- 
tion of  chlorine  and  water  on  carbon  tetrachloride,  this  compound  first 
taking  up  2  atoms  of  chlorine  and  ftmning  carbon  trichloride,  C2C16,  and  the 
latter  being  converted  by  the  water  into  hydrochloric  and  trichloracetic 
acids : 

C2C16        +        20H2        =        3HC1        -f        C2HC1302 

Trichloracetic  acid  is  a  colorless  and  extremely  deliquescent  substance  : 
it  has  a  faint  odor,  and  sharp  caustic  taste,  bleaching  the  tongue  and  de- 
stroying the  ski-n  ;  the  solution  is  powerfully  acid.  At  46°  C.  (115°  F.)  it 
melts  to  a  clear  liquid,  and  at  199°  C.  (390°  F.)  boils  and  distils  unchanged. 
The  density  of  the  fused  acid  is  1-617;  that  of  the  vapor,  which  is  very  ir- 
ritating, is  probably  5-0. 

The  trichloracetates  are  analogous  to  the  acetates.  The  potassium-salt, 
2C2C1302K.  aq.,  crystallizes  in  fibrous  silky  needles,  permanent  in  the  air. 
The  ammonium-salt,  2C2C1302NH4 .  5  Aq.,  is  also  crystallizable  and  neutral. 
The  silver-salt,  C2Cl302Ag,  is  soluble,  and  crystallizes  in  small,  grayish  scales, 
easily  altered  by  light. 

Trichloracetic  acid  boiled  with  excess  of  ammonia  yields  ammonium  car- 
bonate and  chloroform : 

C2HC1302    +     2NH3    -f     OH2    =    C03(NH4)2    -f     CHCL, 

With  caustic  potash,  it  yields  a  smaller  quantity  of  chloroform,  together 
with  potassium  chloride,  carbonate,  and  formate.  The  chloride  and  for- 
mate are  secondary  products  of  the  reaction  of  the  alkali  upon  the  chloro- 
form. 

Nascent  hydrogen  reduces  trichloracetic  to  acetic  acid.  When  potassium 
or  sodium  amalgam  is  put  into  a  strong  aqueous  solution  of  trichloracetic 
acid,  the  temperature  of  the  liquid  rises,  without  disengagement  of  gas, 
and  the  solution  is  found  to  contain  acetate  and  chloride  of  potassium,  to- 
gether with  caustic  potash. 

BROMACETIC  ACIDS. — Monobromacetic  acid,  C2H2BrO(OH),  discovered  by 
Perkin  and  Duppa,  is  analogous  in  every  respect  to  monochloracetic  acid. 
It. is  formed  by  acting  with  bromine  on  glacial  acetic  acid  in  sealed  tubes 
at  a  temperature  above  that  of  boiling  water.  Ammonia  converts  it  into 
glycocine,  C2H5N02  (p.  614). 

Dibromacetic  acid,  C2HBr20(OH),  is  obtained  by  the  further  action  of  bro- 
mine upon  bromacetic  acid.  It  is  a  liquid  boiling  at  240°  C.  (464°  F.); 
heated  with  silver  oxide  and  water,  it  is  decomposed  into  silver  bromide 
and  bromoglycollic  acid: 

2C2H2Br202     +     Ag20     +     H20     =    2AgBr     +     2C2H3Br03 

Dibromacetic  Bromogly- 

acid.  collie  acid. 

Ethyl-dibromacctate,  C2HBr202 .  C2H5,  produced  by  heating  an  alcoholic 
solution  of  the  acid  in  a  sealed  tube,  is  an  oily  liquid  which  is  decomposed 
by  ammonia,  yielding  alcohol  and  dibromacetamide  : 

C2HBr202 .  C2H5     -f     NH3     =     C2H5OH     -f     NH2C2HBr20 

IODACETIC  ACID,  C9H3I02,  and  DI-IODACETIC  ACID,  C2H2I202,  have  like- 
wise been  obtained. 

CH3 
TIIIACETIC  ACID,  C2H4OS,  or  C2H30(SH),  or         |  .—This  acid,  dis- 

O^rC— SH 
52 


614  MONATOMIC   ACIDS,  CnH2I1O2. 

covered  by  Kekule",  is  formed  by  the  action  of  phosphorus  pentasulphide 
on  glacial  acetic  acid  : 

5C2H30(OH)     +     P2S6     =     P205     +     5C2H30(SH) 

Thiacetic  acid  is  a  colorless  liquid,  boiling  at  93°  C.  (199°  F.) ;  it  smells 
like  acetic  acid  and  hydrogen  sulphide.  With  solution  of  lead  acetate,  it 

forms  a  crystalline  precipitate  containing  (C2H30)2Pb//S2,  or  Pb  "  \  Qp2JJ32 

)  ov/a"^ 

AMIDACETIC  ACID,  or  GLYCOCINE,  C2H3N02,  or  C2H3(NH2)02. — This  com- 
pound is  formed  by  the  action  of  ammonia  on  bromacetic  or  chloracetic 
acid: 

C2H3C102    -f    2NH3    =    NH4C1    -f-     C2H3(NH2)02 
Chloracetic  Amidacetic 

acid.  acid. 

It  is  also  produced  by  the  action  of  acids  or  alkalies  upon  animal  sub- 
stances, such  as  glue,  hippuric  acid,  glycollic  acid,  etc.  From  hippuric 
acid  it  is  formed  according  to  the  equation : 

C9H9N03        +        OH2        =        C2H5N02        +        C7H602 
Hippuric  acid.  Glycocine.  Benzoic  acid. 

To  prepare  it,  hippuric  acid  is  boiled  for  several  hours  with  concentrated 
hydrochloric  acid  ;  the  liquid  is  evaporated  nearly  to  dryness  ;  the  residue 
exhausted  with  cold  water;  the  solution  treated  with  lead  oxide,  to  sepa- 
rate the  hydrochloric  acid,  and  filtered :  the  filtrate,  after  precipitation  of 
the  lead  by  sulphuretted  hydrogen,  yields  on  evaporation  hard  transparent 
crystals  of  glycocine.  Glycocine  is  easily  soluble  in  water,  nearly  insol- 
uble in  alcohol  and  ether.  '  It  combines  with  acids  in  different  proportions. 
With  sulphuric  acid  it  forms  the  compound  (C2H5N02)2S04H2;  and  on  addi- 
tion of  alcohol  to  a  solution  of  this  sulphate,  a  salt  crystallizing  in  rectan- 
gular prisms  is  deposited,  containing  3C2H5N02 .  S04H2.  Glycocine  also 
forms  saline  compounds  by  substitution  of  metal  for  hydrogen ;  for  example, 
C^HgCu^N^ .  OH2,  and  C2H4AgN02:  it  also  combines  with  metallic  salts, 
forming  crystalline  compounds,  such  as  C2H5N02.  N08K,  and  C2H5N02. 

Nitrous  acid  converts  glycocine  into  glycollic  or  oxyacetic  acid : 

C2H3(NH2)02     +    2NO(OH)     =     C2H3(OH)02    -f     OH2    +    N2 
Amidacetic  Oxyacetic 

acid.  acid. 

MetTiyl-glycocine,  or  Sarcosine,  C3H7N02,  or  C2H4(CH3)N02,  isomeric  with 
alanine  (p.  619),  is  produced  by  digesting  ethyl-chloracetate  with  an  excess 
of  a  concentrated  aqueous  solution  of  methylamine : 

C2H2C102.C2H6    +    2NH2CH3    +     OH2    =     C2H2(CH3)(NH2)02 

Sarcosine. 

-f     NH2CH3.HC1    +   C,H6(OH) 
Methylamine  Alcohol, 

hydrochloride. 

The  same  compound  is  formed  by  boiling  creatine  *  with  baryta-water ; 
ammonia  is  then  eliminated,  a  precipitate  of  barium  carbonate  separates, 
and  the  solution,  after  the  removal  of  the  barium  by  carbonic  acid,  yields 
on  evaporation  colorless  rhombic  prisms  of  Sarcosine.  The  creatine  splits 
into  sarcosine  and  urea,  the  latter  being  further  decomposed  into  ammonia 
*  See  the  chapter  on  Organic  Bases. 


PROPIONIC   ACID.  615 

and  carbonic  acid.  Sarcosine  dissolves  with  facility  in  water  ;  it  is  diffi- 
cultly soluble  in  alcohol,  insoluble  in  ether,  and  has  no  action  upon  vege- 
table colors.  It  combines  with  acids  to  soluble  salts,  which  have  an  acid 
reaction.  The  double  salt  of  sarcosine  with  platinum  tetrachloride  crys- 
tallizes in  large  yellow  octohedrons  having  the  composition  2C3H7N02. 
2HCl.PtCl4.2  Aq. 

C  H 
Propionic   Acid,    C3H602  =  C3H50(OH)  ==    |2    5    .  —  This  acid   is  pro- 


COOH' 


duced :  1.  As  a  potassium-salt  by  the  combination  of  carbon-dioxide  with 
potassium-ethyl,  C02  -+-  C2H5K  —  CO(C2H5)OK.  —2.  By  the  action  of  acids 
or  alkalies  on  ethyl  cyanide  (p.  599).  —  3.  By  the  simultaneous  action  of 
water  and  carbonyl  chloride  on  ethane  (p.  599)-  —  4.  By  the  oxidation  of 
propionic  aldehyde,  C3H60.  It  should  also  be  formed  by  oxidation  of  nor- 
mal propylic  alcohol :  but  that  compound  is  not  known  with  certainty 
(p.  531). — 5.  Together  with  acetic  acid,  by  oxidizing  propione,  or  meta- 
cetone,  C5Hi00,  with  aqueous  chromic  acid.  This  is  the  process  by  which 
it  was  first  obtained. —  6.  From  lactic  acid  —  from  which  it  differs  only  by 
containing  one  atom  of  oxygen  less  —  by  the  action  of  hydriodic  acid: 
C3H603  +  2HI  =  C3II602  +  OH2  -f  I2 
Lactic  Propionio 

acid.  acid. 

7.  Together  with  several  other  products,  in  the  fermentation  of  glycerin, 
and  likewise  of  sugar,  by  the  action  of  putrid  cheese  in  presence  of  cal- 
cium carbonate. 

Propionic  acid  is  usually  prepared  by  the  second  of  the  above-mentioned 
processes.  Ethyl  cyanide  is  added  by  drops  to  a  moderately  strong  solution 
of  potash  heated  in  a  tubulated  retort,  the  distillate  being  repeatedly  poured 
back  as  long  as  it  smells  of  ethyl  cyanide.  The  residue  in  the  retort,  con- 
sisting of  potassium  propionate,  is  then  evaporated  down  to  dryness,  and 
distilled  with  syrupy  phosphoric  acid. 

Propionic  acid,  when  perfectly  dry,  crystallizes  in  laminae,  and  boils  at 
140°  C.  (284°  F.).  It  is  soluble  in  water,  and  when  the  water  is  quite 
saturated  with  it,  the  excess  of  acid  floats  on  the  surface  in  the  form  of  an 
oil.  It  has  a  very  sour  taste,  and  a  somewhat  pungent  odor. 

The  propionates  are  soluble  in  water.  The  barium-salt,  (CgHjO.^.jBa", 
'yields  propione  by  dry  distillation. 

Propionic  acid  forms  substitution-products  with  chlorine,  bromine,  and 
iodine.  Chloropropionic  acid,  CgHgClO^  does  not  appear  to  be  formed  by 
the  action  of  chlorine  on  propionic  acid;  but  it  is  obtained  by  treating  the 
calcium  salt  of  lactic  acid  with  phosphorus  pentachloride,  whereby  lactyl 
chloride  or  chloropropionyl  chloride  is  formed,  and  decomposing  this 
chloride  with  water : 

C3H40(OH)2     -f     PC15     =    C3H4C10.C1     -f-     PC130     -f     OH3 
Lactic  acid.  Chloropropionyl 

chloride. 

C3H4C10.C1       -f      OH2      =      HC1      +       C3H4C10(OH) 
Chloropropionyl  Chloropropionio 

chloride.  acid. 

Chloropropionic  acid  is  a  liquid  less  volatile  than  propionic  acid,  and  hav- 
ing the  odor  of  trichloracetic  acid.  Nascent  hydrogen  converts  it  into 
propionic  acid. 

liromopropionic  acid,  C3II5Br02,  produced  by  the  action  of  bromine  on 
propionic  acid,  is  converted  by  alcoholic  ammonia  into  alanine,  or  amido- 
propianic  acid: 

C3II5Br02        +        2NH,        =        C3H6(NH2)02        +        NH4Br. 


616  MONATOMIC    ACIDS,  CnH2nO2. 

Alanine,  homologous  with  glycocine  and  isomeric  with  sarcosine  (p.  614), 
is  also  produced  by  boiling  a  mixture  of  aldehyde-ammonia  and  hydro- 
cyanic acid  with  dilute  hydrochloric  acid: 

C2H4O.NH3    +    CNH    +    HC1   +   OH2  =  NH4C1  +  C3H7N02. 
Aldehyde-  Alanine. 

ammonia. 

On  evaporating  the  solution,  extracting  the  hydrochloride  of  alanine  with 
alcohol,  and  separating  the  hydrochloric  acid  by  hydrated  lead  oxide,  a 
solution  is  obtained  containing  alanine  in  combination  with  lead  oxide, 
from  which  the  alanine  may  be  separated  by  saturating  the  solution  with 
sulphuretted  hydrogen,  filtering,  and  evaporating.  It  forms  rhombic  prisms 
of  a  pearly  lustre,  easily  soluble  in  alcohol,  sparingly  soluble  in  ether. 
Alanine,  like  glycocine,  combines  with  acids,  bases,  and  salts. 

Nitrous  acid  converts  alanine  into  lactic  or  oxypropionic  acid,  C4H603, 
the  reaction  being  exactly  similar  to  that  by  which  glycocine  is  converted 
into  glycollic  acid. 

Butyric  Acid,  C4H802=C4H70(OH).  — Acids  having  this  composition,  are 
obtained  by  the  following  synthetical  processes: 

a.  By  the  action  of  ethyl-iodide  on  monosodic  ethyl  acetate  (p.  600),  and 
decomposition  of  the  resulting  ethylic  ethyl-acetate  with  potash:  the  pro- 
duct thus  obtained  is  ethyl-acetic  or  normal  butyric  acid : 

CH2Na  CH2C2H6 

|  +        C2H6I        =          Nal          +       I 

COOC2H5  COOC2H6 

Monosodic  Ethyl  Ethylic 

ethyl-acetate.  iodide.  ethyl-acetate. 

CH2C2H5  CH2C2H5 

I  +        HOH         =     C2H5(OH)      +       | 

COOC2H6  COOH 

Ethylic  Water.  Ethyl  Ethylacetic 

ethyl-acetate.  alcohol.  acid. 

fi.  Disodic  ethyl-acetate,  treated  in  like  manner  with  methyl-iodide,  yields 
dimethylic  ethyl-acetate : 

CHNa2  JCH(CH3)2 

+        2CH,I        =        2NaI          +       I 
COOC2H6  COOC2H5; 

and  this  compound,  treated  with  potash,  is  converted  into  dimethyl-acetic 

CH(CH3)2 
or  isobutync  acid, 

COOH. 

Ethylacetic  acid  boils  at  161°  C.  (322°  F.),  dimethylacetic  acid  at  152°  C. 
(305°  F.)  (Frankland  and  Duppa). 

Butyric  acid,  identical  with  the  first  of  these  synthetical  products,  occurs 
ready-formed  in  tamarinds  and  a  few  other  plants,  and  in  certain  beetles, 
and  is  obtained  artificially  by  several  processes. 

1.  By  oxidation  of  primary  butyl  alcohol.*  —  2.  By  saponification  of  ordi- 
nary butter,  which  contains  tributyrin : 

(C8H5)'"(OC4H70)3    +     3KOH    =    3C4TI7OH    +     C3H5(OH3) 
Tributyrin.  Potassium  Glycerin. 

butyrate. 

*  If  Erlenmeyer's  view  of  the  constitution  of  the  fermentation  alcohols  be  correct,  the  acid 
produced  by  oxidation  of  butyl  alcohol  obtained  from  fusel  oil,  should  be  isobutyric  acid:  the 
point  requires  further  investigation. 


BUTYRIC    AND    VALERIC    ACIDS.  617 

Other  acids  of  the  series  are,  however,  formed  at  the  same  time,  which  are 
difficult  to  separate. 

3.  By  the  fermentation  of  sugar  in  contact  with  putrid  cheese  and  chalk, 
calcium  lactate  being  first  formed  in  large  quantity,  and  afterward  dis- 
solved and  converted  into  butyrate,  which  may  be  decomposed  by  sulphuric 
acid,  and  distilled.  The  conversion  of  lactic  into  butyric  acid  probably 
takes  place  as  shown  by  the  equation : 

2C3H603        =        C4H802        +    2C02    -f-     2H2 
Lactic  acid.  Butyric  acid. 

Butyric  acid  thus  obtained  is  a  colorless,  very  mobile  liquid,  having  an 
odor  of  acetic  acid  and  also  of  rancid  butter.  Its  specific  gravity  is  0-9886 
at  0°,  and  0-9739  at  15°.  At  the  temperature  of  a  mixture  of  solid  car- 
bonic acid  and  ether  it  crystallizes  in  large  laminae.  It  boils  at  164°  C. 
(327°  F.),  giving  off  a  vapor  which  burns  with  a  blue  flame.  It  dissolves 
in  all  proportions  in  water,  alcohol,  and  wood-spirit.  Boiling  nitric  acid 
converts  it  into  succinic  acid : 

2C4H802    +     06    =    20II2     -f     2C4H603 

Butyric  Succinic 

acid.  acid. 

The  metallic  butyrates  are,  for  the  most  part,  soluble  in  water,  and  crys- 
tallizable.  The  calcium  salt  C4H7OaCa",  yields  butyrone,  C4H70 .  C3H7, 
by  dry  distillation. 

Ethyl  Butyrate,  C4H702 .  C2H5,  is  a  liquid  having  a  pleasant  fruity  odor: 
it  is  sometimes  used  for  flavoring  confectionery. 

Butyric  acid,  subjected  to  the  action  of  dry  chlorine,  is  converted  first 
into  dlchlorobutyric  acid,  C4H6C1202,  and  afterward  into  tetrachlorobutyric 
acid,  C4H4C1402.  Heated  with  bromine  in  sealed  tubes  to  150°-200°  C.  (302°- 
392°  F.),  it  forms  mono-  or  dibromobutyric  acid,  according  to  the  propor- 
tions used.  Dibromobutyric  acid  is  crystallizable. 

Amidobutyric  acid,  C4H9N02,  or  C4H7(NH2)02,  is  said  to  exist,  together 
with  its  homologue,  leucine  or  amidocaproic  acid,  in  the  pancreas  of  the  ox. 

Valeric,  or  Valerianic  Acid,  C5TI1002  =  C5H90(OH).— This  acid  occurs  in 
valerian  root,  in  angelica  root,  in  the  berries  of  the  guelder  rose  (  Vibur- 
num opulus],  and  probably  in  many  other  plants.  It  is  produced  by  the 
oxidation  of  amyl  alcohol,  either  by  absorption  of  atmospheric  oxygen 
under  the  influence  of  platinum  black,  or  by  treatment  with  aqueous 
chromic  acid,  or  by  heating  it  with  a  mixture  of  caustic  potash  and  quick- 
lime, the  reaction,  in  this  last  case,  being  attended  with  evolution  of  hy- 
drogen : 

C5Hi2O     +     KOH     =     C5H902K     -f     OH2    -f     H2 
Amyl  Potassium 

alcohol.  valerate. 

The  potassium  salt,  distilled  with  sulphuric  acid,  yields  valeric  acid. 

The  most  advantageous  mode  of  preparing  valeric  acid,  is  to  oxidize 
amyl  alcohol  with  a  mixture  of  sulphuric  and  potassium  bichromate.  4 
parts  of  the  bichromate  in  powder,  6  parts  of  oil  of  vitriol,  and  8  parts  of 
water  are  mixed  in  a  capacious  retort,  and  1  part  of  amyl  alcohol  is  added 
by  small  portions,  with  strong  agitation,  the  retort  being  plunged  into  cold 
water  to  moderate  the  violence  of  the  reaction.  When  the  change  appears 
complete,  the  deep-green  liquid  is  distilled  nearly  to  dryness,  the  product 
mixed  with  excess  of  caustic  potash,  and  the  aqueous  solution  separated 
mechanically  from  a  pungent,  colorless,  oily  liquid  which  floats  upon  it, 
consisting  of  amyl  valerate.  The  alkaline  solution  is  then  evaporated  to  a 
52* 


618  MONATOMIC   ACIDS,  CnH2nO2. 

small  bulk,  and  decomposed  by  dilute  sulphuric  acid  in  excess.  The 
greater  part  of  the  valeric  acid  then  separates  as  an  oily  liquid  lighter 
than  water:  this  is  a  hydrate  consisting  of  C5H1002.  OH2.  When  distilled 
alone,  it  undergoes  decomposition :  water,  with  a  little  of  the  acid,  first 
appears,  and  eventually  the  pure  acid,  C5H1002,  in  the  form  of  a  thin,  mo- 
bile, colorless  oil,  having  the  persistent  and  characteristic  odor  of  valerian 
root.  It  has  a  sharp  and  acid  taste,  reddens  litmus  strongly,  bleaches  the 
tongue,  and  burns  when  inflamed  with  a  bright,  yet  smoky  light.  Valeric 
acid  has  a  density  of  0-937:  it  boils  at  175°  C.  (347°  F.).  Placed  in  con- 
tact with  water,  it  absorbs  a  certain  quantity,  and  is  itself  to  a  certain  ex- 
tent soluble. 

Valeric  acid  is  active  or  inactive  to  polarized  light,  accordingly  as  it  has 
been  prepared  from  active  or  inactive  amyl  alcohol.  That  which  has  been 
prepared  from  the  active  alcohol  produces  a  right-handed  rotation  of  43° 
in  a  tube  50  centimetres  long.* 

The  metallic  valerates  are  not  of  much  importance;  several  of  them  are 
crystallizable.  The  silver-salt  contains  C5H902Ag.  A  solution  of  potassium 
valerate,  subjected  to  electrolysis,  yields  dibutyl,C8H]8  (p.  475). 

Ethyl  valerate,  C6H902 .  C2H5,  is  obtained  by  passing  hydrochloric  acid  gas 
into  an  alcoholic  solution  of  valeric  acid.  Ammonia  converts  it  into  vale- 
ramide,  C5H9ONH2. 

CHLOROVALERIC  ACIDS. — Trichlorovaleric  acid,  C5H7C1302,  obtained  by  the 
prolonged  action  of  chlorine  on  valeric  acid  in  the  dark,  aided  toward  the 
end  of  the  process  by  a  gentle  heat,  is  an  oily  liquid,  becoming  very  viscid 
at  18°  C.  (64°  F.),  perfectly  mobile  at  30°  C.  (86°  F.).  In  contact  with 
water  it  forms  a  very  viscid  hydrate,  which  sinks  to  the  bottom.  It  dis- 
solves in  aqueous  alkalies,  and  is  precipitated  by  acids  in  its  original  state. 

Tetrachlorovaleric  acid,  C5H6C1402,  is  the  ultimate  product  of  the  action  of 
chlorine  on  the  preceding  substance,  aided  by  exposure  to  the  sun.  It  is  a 
semifluid,  colorless  oil,  destitute  of  odor,  of  powerful  pungent  taste,  and 
heavier  than  water.  It  can  neither  be  solidified  by  cold  nor  distilled  with- 
out decomposition.  In  contact  with  water,  it  forms  a  hydrate  containing 
C6H6C1402 .  OH2,  which  is  slightly  soluble  in  water,  easily  soluble  in  alcohol 
and  ether. 

Isomeric  forms  of  Valeric  acid.  —  The  formula  C5H1002  may  include  the 
four  following  compounds: 

CII2CH2CII2CH3       CH2CH(CH3)2      CHCH3[CH2CH3]       C(CH3)3 

COOH  COOH  COOH  COOH 

Propyl-  Isopropyl-  Methyl-ethyl-       Triinethyl 

acetic  acid.  acetic  acid.  acetic  acid.         acetic  acid. 

The  second  and  fourth  of  these  acids  have  been  prepared  by  Frankland 
and  Duppa.j- 


CH2CH(CH3) 


Ethyl  isopropylacetate,     \  ,  is  obtained  by  the  action  of  isopro- 

COOC2H5 

pyliodide,  CH(CH3)2I,  on  monos<?dic  ethyl  acetate,  and  from  this  ether  iso- 
propylaceiic  acid  is  prepared,  as  in  the  similar  cases  previously  described. 

It  is  identical  in  every  respect  with  valeric  acid  prepared  from  optically 
inactive  amyl  alcohol. 

Trimethylacetic  acid  is  obtained  as  an  ethyl  ether  by  the  action  of  methyl 
iodide  on  trisodic  ethyl  acetate : 

*  Pedler,  Chem.  Soc.  Journal  [2],  vi.  74.  f  Chem.  Soc.  Journal  [2],  v.  102. 


CAPROIC  —  (E^ANTHYLIC   ACID.  619 

CNa,  C(CH3)3 

|  +      3CH3I      =      3NaI       -f 

COOC2II5  COOC2H6 


Uaproic  Acid,  C6Hla02  =  C6HU0(OH)  =  |          .  —  This  acid  is  produced  by 

COOH 

the  action  of  alkalies  or  acids  on  amyl  cyanide,  C5H,,CN  (p.  599)  ;  also,  as  a 
sodium-salt,  by  the  action  of  carbon  dioxide  on  sodium-amyl:  COg-j-CgHjj 
Na—  CO(C5HH)ONa.*  It  occurs  as  a  glyceride  in  the  butter  of  cow's  milk, 
and  abundantly  in  cocoa-nut  oil;  it  is  a  not  unfrequent  product  of  the  oxi- 
dation of  fatty  acids  of  higher  atomic  weight,  and  is  also  produced  by  the 
oxidation  of  poppy  oil  and  of  casein.  It  may  be  prepared  from  cocoa-nut 
oil  by  saponifying  the  oil  with  strong  soda-lye,  and  distilling  the  soap  with 
dilute  sulphuric  acid.  The  distillate  contains  caproic  and  caprylic  acids, 
and,  when  neutralized  with  baryta  and  evaporated,  yields,  first  crystals  of 
barium  caprylate,  and  afterwards  verucose  crystals  of  the  caproate,  which, 
when  decomposed  by  sulphuric  acid,  yield  caproic  acid. 

Caproic  acid  is  a  clear  mobile  oil  of  sp.  gr.  0-931  at  15°,  having  a  sudo- 
rific odor  and  pungent  taste.  The  acid  prepared  from  amyl  cyanide  solid- 
ifies at  —  9°C.  (10°  F.),  boils  at  198°  C.  (388°  F.),  and  is  active  to  polarized 
light.  That  from  cocoa-nut  oil  boils  between  202°  and  209°  C.  (395°-408°  F.) 
(perhaps  owing  to  admixture  of  caprylic  acid),  and  is  optically  inactive. 

The  metallic  caproates  are  soluble  and  crystallizable.     A  strong  solution 
of  the  potassium-salt,  subjected  to  electrolysis,  yields  diamyl,  C10H22(p.  475). 
The  silver-salt,  C6Hn02Ag,  is  nearly  insoluble  in  water,  and  crystallizes  in 
broad  plates,  but  is  little  altered  by  exposure  to  light. 
CH(C2H5)2 

DIETHYL-ACETIC  ACID,    |  ,  the  ethylic  ether  of  which  is  prepared 

COOH 

by  the  action  of  ethyl  iodide  on  disodic  ethyl  acetate,  is  isomeric  with  ca- 
proic acid.  It  has  a  different  odor,  and  its  silver-salt  forms  silky  asbestos- 
like  crystals,  soluble  in  water,  and  turning  brown  when  exposed  to  a  strong 
light. 

AMIDOCAPROIC  ACID,  or  LEUCINE,  C6H,3N02  or  C6Hn(NH2)02,  has  not  been 
obtained  directly  from  any  derivative  of  caproic  acid,  but  is  produced  by 
digesting  together  valeral-ammonia,  hydrocyanic  acid,  and  hydrochloric 
acid,  the  reaction  being  analogous  to  that  by  which  alanine  is  prepared 
from  the  ammonia-compound  of  acetic  aldehyde: 

C5H10O.NH3  +  CNH  +  HC1  +  OH2  =  C6H13N02  +  NH4C1 
Valeral-aui*  Leucine. 

monia. 

Leucine  is  also  formed  by  the  decomposition  of  animal  substances,  such 
as  glue,  horn,  wool,  &c.,  during  putrefaction,  and  by  the  treatment  of  these 
substances  with  acids  or  alkalies.  It  was  first  discovered  in  putrid  cheese; 
more  recently  it  has  been  found  in  several  parts  of  the  animal  organism. 
Leucine  crystallizes  in  white  shining  scales,  which  melt  at  100°,  and  may 
be  sublimed  without  decomposition;  it  is  but  little  soluble  in  water,  still 
tless  in  alcohol,  insoluble  in  ether.  When  heated  with  caustic  baryta,  it 
splits  into  carbon  dioxide  and  amylamine:  C6H13N02=C5H13N-[-CO2.  It 
unites  with  acids,  bases,  and  salts.  Treatment  with  nitrous  acid  converts 
it  into  leucic  acid,  C6H,203,  homologous  with  lactic  and  glycollic  acids. 

<VT,3 

(Enanthylic  Acid,  C7IIU02  =  C7H,3(OH)  =    |      .  —  This  acid  is  produced 

COOH 

*  Wanklyn  and  Schcnk,  Cheui.  Soc.  Journal  [2],  vi.  31. 


620  MONATOMIC   ACIDS,  CnH  nO2. 

from  oenanthol,  or  oenanthylic  aldehyde,  C7H140  (a  liquid  obtained  by  the 
dry  distillation  of  castor-oil),  by  oxidation  in  the  air,  or  with  nitric  acid, 
or  with  chromic  acid  ;  also  by  oxidation  of  castor-oil  with  nitric  acid. 
Amyl-acetic  acid,  isomeric  or  identical  with  it,  is  obtained  as  an  ethylic 
ether,  together  with  several  other  products,  by  the  action  of  amyl  iodide 
on  disodic  ethyl  acetate. 

(Enanthylic  acid  is  a  transparent  colorless  oil,  having  an  unpleasant  odor 
like  that  of  codfish.  It  boils,  according  to  Strecker,  at  212°  C.  (413°  F.). 
It  is  insoluble  in  water,  but  soluble  in  alcohol  and  ether.  When  heated 
with  baryta,  it  gives  off  sextane  or  hexyl  hydride.  C6H,4,  the  baryta  ab- 
stracting carbon  dioxide:  C7H1402— C02-^C6HU.  The  potassium-salt,  sub- 
jected to  electrolysis,  yields  dikczyl,  C12H26. 

Caprylic  Acid,  C8H1602=C8H130(OH),  occurs  as  a  glyceride  in  the  butter 
of  cow's-milk  and  in  cocoa-nut  oil;  it  is  also  found  in  several  kinds  of  fusel- 
oil,  partly  free,  partly  as  an  ethylic  or  amylic  ether.  It  is  best  prepared  by 
saponification  of  cocoa-nut  oil ;  its  barium-salt,  being  very  sparingly  solu- 
ble, is  easily  separated  from  the  barium-salt  of  caproic  acid  formed  at  the 
same  time. 

Caprylic  acid  has  a  faint  but  unpleasant  odor,  especially  when  warmed. 
It  solidifies  at  12°  C.  (54°  F.),  melts  at  15°  C.  (59°  F.),  and  boils  at  236°- 
238°  C.  (457°-460°  F.).  When  boiled  with  nitric  acid,  it  is  converted  into 
nitrocaprylic  acid,  C8H,5(N02)02. 

Pelargonic  Acid,  C9H1802  —  C9H,7(OH),  was  first  obtained  from  the  leaves 
of  the  geranium  (Pelargonium  roseurn),  in  which  it  exists  ready  formed.  It 
may  be  procured  in  large  quantity  by  the  action  of  nitric  acid  upon  the 
essential  oil  of  rue  (which  contains  the  two  aldehydes,  C,,H220  and  C12II240)  ; 
also,  together  with  several  acids  of  the  fatty  series,  by  the  action  of  boiling 
nitric  acid  on  oleic  acid.  It  is  a  liquid  having  a  slightly  unpleasant  odor, 
and  boiling  at  260°  C.  (500°  F.). 

Ethyl  pelargonate,  C9II902 .  C2H5,  may  be  easily  produced  by  dissolving 
the  acid  in  strong  alcohol,  and  passing  a  current  of  hydrochloric  acid 
through  the  solution.  It  is  a  liquid  of  specific  gravity  0-862,  and  boiling 
at  250°  C.  (482°  F.).  It  has  a  powerful  and  most  intoxicating  vinous  odor. 

The  aroma  possessed  by  certain  wines  appears  to  be  due  to  the  presence 
of  the  ether  of  pelargonic  acid,  which,  in  this  case,  is  probably  generated 
during  fermentation.  When  such  wines,  or  the  residues  of  their  fermen- 
tation, are  distilled  on  the  large  scale,  an  oily  liquid  passes  over  towards 
the  close  of  the  operation,  which  consists,  in  great  measure,  of  the  crude 
ether :  it  may  be  purified  by  agitation  with  solution  of  potassium  carbonate, 
freed  from  water  by  a  few  fragments  of  calcium  chloride,  and  redistilled. 
The  pelargonic  ether  obtained  by  this  process  was  originally  described  as 
cenanthic  ether,  and  the  acid  as  cenanthic  acid. 

Eutic  or  Capric  Acid,  C)0H2002. — This  acid  exists  as  a  glyceride  in  ordi- 
nary butter  and  in  cocoa-nut  oil :  it  occurs  also  in  several  kinds  of  fusel-oil, 
and  is  formed  by  the  oxidation  of  oleic  acid  and  of  oil  of  rue.  It  may  be 
obtained  pure  and  in  tolerable  quantity  from  the  liquid  which  remains  in 
the  distillation  of  the  fusel-oil  of  the  Scotch  distilleries  (p.  626)  after  the 
amyl  alcohol  has  been  distilled  off  at  132°  C.  (270°  F.).  This  residue  con- 
sists chiefly  of  amyl  rutate,  C10H,902 .  C5H,,,  and  when  distilled  with  potash 
gives  off  amyl  alcohol  and  leaves  potassium  rutate,  from  which  the  rutic 
acid  may  be  obtained  by  distillation  with  sulphuric  acid. 

Rutic  acid  is  a  colorless  crystalline  body,  having  a  slight  odor  of  the 
goat,  becoming  stronger  when  the  acid  is  warmed.  It  melts  at  27°-30°  C. 
(80°-86°  F.),  is  very  soluble  in  cold  alcohol  and  ether,  insoluble  in  cold 
water,  slightly  soluble  in  boiling  water,  and  dissolves  without  alteration  in 
strong  nitric  acid. 


LAURIC —  MYRISTIC  —  PALMITIC    ACID.  621 

The  metallic  rutates  are  mostly  sparingly  soluble  in  water.  The  barium- 
salt,  (C|0H1902)8Ba//,  separates  from  solution  in  boiling  water  in  needle- 
shaped  or  large  prismatic  crystals  which  float  on  the  water  if  not  moistened. 

Laurie  Acid,  C12H2402,  occurs  as  a  glyceride  (laurostearin)  in  the  fat  of 
the  bay-tree  (Lauras  nobilis),  and  in  the  solid  fat  and  volatile  oil  of  pichu- 
rim  beans  (Fabse  Pichurim  maj.}.  It  is  prepared  by  saponifying  these  fats 
with  caustic  alkali,  and  decomposing  the  resulting  soap  with  tartaric  or 
hydrochloric  acid.  It  likewise  occurs,  together  with  other  fatty  acids,  or 
their  glycerides,  in  cocoa-nut  oil  and  the  oils  or  fats  of  several  other  plants, 
also  in  spermaceti ;  and  is  separated  from  the  mixtures  of  fatty  acids  re- 
sulting from  the  saponification  of  these  substances  by  a  complicated  process 
of  fractional  precipitation  with  barium  and  magnesium  salts,  into  the  de- 
tails of  which  we  cannot  enter.* 

Laurie  acid  is  insoluble  in  water,  but  dissolves  easily  in  alcohol  and  ether, 
and  crystallizes  from  alcohol  in  white,  silky  needles,  which  melt  at  about 
43°  C.  (109°  F.). 

The  laurates  of  the  alkali-metals  and  of  barium  are  soluble  in  water;  the 
other  salts  are  insoluble  or  sparingly  soluble.  The  calcium  salt,  (C12H230)2 
Cax/,  is  resolved  by  distillation  into  calcium  carbonate  and  laurostearone : 

(C12H230)2Ca"         =         C03Ca"         +         C24H460 
Calcium  laurate.  Calcium  Lauro- 

carbonate.  stearone. 

Myristic  Acid,  C,4H2802. —  This  acid  occurs  as  a  glyceride  in  nutmeg-but- 
ter and  Otoba  fat ;  also,  together  with  lauric  acid,  in  Dika  bread,  the  fruit 
of  Mangifera  gabonensis,  an  African  tree;  and,  together  with  other  fatty 
acids,  in  cocoa-nut  oil  and  spermaceti.  It  may  be  produced  from  crude 
ethal  (cetyl  alcohol)  by  heating  with  a  mixture  of  potash  and  lime,  its  for- 
mation being  doubtless  due  to  the  presence  of  methal  or  myristic  alcohol  in 
the  crude  ethal  (p.  543)  : 

CUH300     +     KHO    =     CUH2702K    -f     2H2 
Methal.  Potassium 

myristate. 

Lauric  acid  is  likewise  produced  by  a  similar  process  from  crude  ethal, 
doubtless  because  that  substance  also  contains  lethal  or  lauric  alcohol, 

C»H*O. 

Pure  myristic  acid  is  most  easily  obtained  by  saponification  of  Otoba  fat 
(from  Myristica  Otoba).  It  forms  white,  shining,  crystalline  laminae,  melt- 
ing at  53-8°  C.  (129°  F.).  It  is  quite  insoluble  in  water  and  in  ether,  but 
dissolves  easily  in  hot  alcohol,  and  crystallizes  therefrom  on  cooling. 

The  myristates  of  the  alkali-metals,  C14H2702K,  &c.,  are  soluble  in  water, 
and  not  decomposed  thereby  (like  the  stearates).  The  other  myristates  are 
insoluble  or  sparingly  soluble,  and  are  obtained  by  precipitation. 

Mi/ristic  oxide,  or  Anhydride,  (C,4H270)20,  is  obtained,  like  other  acid 
oxides  of  the  series,  by  the  action  of  phosphorus  oxychloride  on  potassium 
myristate.  It  is  a  fatty  substance,  having  a  somewhat  lower  melting  point 
than  myristic  acid.  It  is  slowly  saponified  by  boiling  caustic  potash. 

Mtirixtin,  (CtH5)///(CMH29Oa).,  the  glyceride  of  myristic  acid,  is  obtained 
by  pressing  nutmegs  between  hot  plates,  exhausting  the  crude  fat  thus  ob- 
tained with  spirits  of  wine,  and  crystallizing  the  undissolved  portion  from 
boiling  ether.  It  is  a  crystalline  fat  having  a  silky  lustre. 

Palmitic  Acid,  C16II3202. — This  acid  occurs  as  a  glyceride  (tripalmitin)  in. 
many  natural  fats,  often  associated  with  stearin.  Palm-oil,  the  produce  of 

*  See  Watts'a  Dictionary  of  Chemistry,  vol.  iii.  p.  474. 


622  MONATOMIC   ACIDS;  CnH2nO2. 

Elais  guianensis,  Chinese  tallow,  the  produce  of  the  tallow-tree  (StiUingia 
sebifera],  and  Japan  wax,  from  R has  succedania,  consist  mainly  of  tripalmitin. 
Palmitic  acid  is  easily  prepared  by  saponifying  palm-oil  with  caustic  potash, 
decomposing  the  soap  with  sulphuric  acid,  and  crystallizing  the  separated 
fatty  acid  several  times  from  hot  alcohol  till  it  exhibits  a  constant  melting 
point.  Chinese  tallow  may  be  saponified  with  alcoholic  potash,  and  Japan 
wax  by  fusion  with  solid  potassium  hydrate,  and  the  soap  treated  in  a 
similar  manner. 

Palmitic  acid  exists  also  as  cetyl  palmitate  (cetin),  C]6H3i02 .  C16H33,  in 
spermaceti,  and  as  myricyl  palmitate  (melissin),  C16H3,02.  C^II^,  in  bees'- 
wax.  It,  is  produced,  together  with  acetic  acid,  by  melting  oleic  acid  with 
potassium  hydrate: 

C18H3402    +    2KOH     =     C16H3I02K     +     C2H302K    +     H2 
Oleic  acid.  Palmitic  Acetic 

acid.  acid. 

Palmitic  acid  is  a  colorless,  solid  body  without  taste  or  smell,  lighter 
than  water.  It  is  insoluble  in  water,  but  dissolves  abundantly  in  boiling 
alcohol  or  ether.  The  solutions  are  acid,  and  when  concentrated,  solidify 
in  a  mass  on  cooling.  When  dilutfc  they  yield  the  acid  in  tufts  of  slender 
needles.  It  melts  at  62°  C.  (144°  F. ),  and  solidifies  on  cooling  in  a  mass 
of  shining  nacreous  laminae.  When  heated  in  a  dish,  it  boils  and  evapo- 
rates without  residue,  and  may  be  distilled  almost  without  change.  When 
gently  heated  in  the  air,  it  is  but  slightly  altered,  but  at  higher  tempera- 
tures it  takes  fire,  and  burns  with  a  bright  smoky  flame  like  other  fats.  It 
is  attacked  by  chlorine  at  100°,  giving  off  hydrochloric  acid,  and  forming 
oily  substitution-products.  Heated  with  alcohols,  it  forms  compound 
ethers. 

Palmitic  acid  forms  normal  or  neutral  salts,  having  the  composition 
C,6H3102M  for  univalent,  and  (Cj6II3l02)2M//  for  bivalent  metals,  and  with 
the  alkali-metals  also,  acid  salts  analogous  to  the  acid  acetates.  The  normal 
palmitates  of  potassium  and  sodium  are  soluble  in  water  and  alcohol;  the 
rest  are  insoluble,  and  are  obtained  by  precipitating  a  metallic  salt  with 
an  alcoholic  solution  of  sodium  or  potassium  palmitate.  The  normal  potas- 
sium-salt, CI6H3]02K,  obtained  by  melting  the  acid  with  potassium  cai'bonate, 
and  exhausting  with  boiling  alcohol,  crystallizes  in  pearly  scales.  The 
acid  salt,  Cl6H3l02K.  C|6H3202,  is  precipitated  on  mixing  a  solution  of  1  part 
of  the  normal  salt,  in  20  parts  of  boiling  water  with  1000  parts  of  cold 
water.  The  barium-salt,  (C16H3I02)2Ba//,  is  a  white,  pearly,  crystalline 
powder;  the  magnesium-salt,  (C16H3102)2Mg//,  is  a  snow-white,  loose,  crys- 
talline precipitate. 

Ethyl  palmitate,  C,6H3102.  C2H5,  obtained  by  passing  hydrochloric  acid 
gas  into  a  saturated  alcoholic  solution  of  palmitic  acid,  crystallizes  in 
prisms,  and  melts  at  24°  C.  (75°  F.). 

Glyceryl  palmitates,  or  Palmitins.  —  There  are  three  of  these  ethers — viz., 
monopalmitin,  (C3H5)'"(OH)2(C16H3102),  dipalmitin,  (C3H5)'"(OH)(C16H3102)2, 
and  tripalmitin,  (C3H5)///(C16H3,02)3.  The  first  and  second  are  obtained  by 
heating  palmitic  acid  with  glycerin  in  sealed  tubes ;  the  third  by  heating  a 
mixture  of  1  part  of  monopalmitin  and  10  parts  of  palmitic  acid  to  250°  C. 
(482°  F.)  for  twenty-eight  hours.  They  are  all  crystalline  fats.  Tri- 
palmitin thus  obtained  melts  at  46°  C.  (115°  F.).  Natural  palrnitin,  obtained 
from  palm-oil  and  other  fats,  has  the  composition  of  tripalmitin,  but  ex- 
hibits three  isomeric  (or  rather  allotropic)  modifications  (like  those  of 
stearin),  melting  respectively  at  46°,  (U-7°,  and  62-8°  C.  (115°,  142°,  144° 
F.):  the  first  appears  to  be  identical  with  artificial  tripalmitin. 

Palm-oil  comes  chiefly  from  the  coast  of  Africa.  It  has  when  fresh,  a 
deep  orange-red  tint,  and  a  very  agreeable  odor:  the  coloring  matter  — 


MARGARIC  —  STEARIC    ACID.  623 

the  nature  of  which  is  unknown  —  is  easily  destroyed  bv  exposure  to  light, 
especially  at  a  high  temperature,  and  also  by  oxidizing  agents.  The  oil 
melts  at  ^7°  C.  (80°  F.).  By  cautious  pressure  it  may  be  separated  into 
fluid  olein  and  solid  palmitin,  which,  when  purified  by  crystallization  from 
hot  ether,  is  perfectly  white.  By  keeping,  palm-oil  seems  to  suffer  a  change 
similar  to  that  produced  by  saponification  :  in  this  state  it  is  found  to  con- 
tain traces  of  glycerin  and  a  considerable  quantity  of  oleic  acid,  together 
with  palmitic  acid.  The  oil  becomes  harder  and  rancid,  and  its  melting 
point  is  raised  at  the  same  time. 

Margaric  Acid,  C^H^O^  —  This  name  was  formerly  applied  to  an  acid, 
intermediate  between  stearic  and  palmitic  acids,  supposed  to  be  produced, 
together  with  others,  by  the  saponification  of  natural  fats;  but  it  is  now 
restricted,  for  reasons  to  be  presently  mentioned,  to  an  acid  prepared  by 
a  definite  reaction  —  viz.,  by  the  action  of  boiling  alcoholic  potash  on  cetyl 
cyanide  : 


+      KOH      +       OH2      =      NH3      -f       C17H3302K 
Cetyl  Potassium 

cyanide.  margarate. 

The  solid  potassium  salt  thus  obtained  is  decomposed  by  boiling  dilute  hy- 
drochloric acid,  and  the  separated  margaric  acid  is  purified  by  precipitat- 
ing its  ammoniacal  solution  with  barium  chloride,  decomposing  the  pre- 
cipitate with  hydrochloric  acid  and  ether,  separating  the  ethereal  solution 
by  means  of  a  pipette,  and  distilling  off  the  ether.  It  forms  white  crystals, 
melting  at  59  9°  C.  (140°  F.),  and  is  intermediate  in  all  its  properties  be- 
tween palmitic  and  stearic  acids. 

The  so-called  margaric  acid,  obtained  by  the  saponification  of  natural 
fats,  and  regarded  by  Chevreul*and  many  other  chemists  as  a  distinct 
acid  having  the  composition  C,7H3402,  has  been  shown  by  Heintz  f  to  be  a 
mixture,  resolvable  into  stearic  acid  and  other  fatty  acids  of  lower  melting 
points,  chiefly  palmitic  acid.  Such  mixtures  of  solid  fatty  acids,  or  of  the 
corresponding  glycerides,  cannot  be  completely  resolved  into  their  constit- 
uent fats  by  ci'ystallization  from  alcohol,  ether,  or  other  solvents,  which 
was  the  method  of  separation  resorted  to  in  the  earlier  investigations. 
The  only  effectual  method  of  separation  is  to  subject  the  alcoholic  solution 
of  the  acids  to  a  series  of  fractional  precipitations  with  acetate  of  lead, 
barium,  or  magnesium,  the  stearate  then  separating  out  first. 

Stearic  Acid,  C,8H3602.  —  This  acid  was  discovered  by  Chevreul  as  a  con- 
stituent of  the  more  solid  fats  of  the  animal  kingdom.  It  is  most  abun- 
dant in  these,  especially  in  beef-  and  mutton-suet;  but  exists  also,  together 
with  palmitic,  myristic  acid,  &c.,  in  the  softer  fats,  such  as  the  butter  of 
cow's-milk,  human  fat,  that  of  the  goose,  of  serpents,  of  cantharides,  and 
in  spermaceti.  It  occurs  also  in  vegetable  fats,  especially  those  of  cacao- 
beans,  of  the  berries  of  Cocculus  indicus,  and  in  shea-butter,  obtained  from 
the  nuts  of  Bassia  Parkii,  a  tree  growing  in  West  Africa.  In  all  these  fats 
it  occurs  as  a  glyceride,  but  in  that  of  cocculus  grains  also  in  the  free 
state. 

Stearic  acid  is  prepared  from  beef-  or  muffon-suet,  or  better  from  cacao-  fat, 
by  saponifying  the  fat  with  soda-lye,  heating  the  soap-paste  with  water 
and  dilute  sulphuric  acid,  removing  the  separated  fatty  acids  after  cooling, 
washing  them  with  water,  and  then  dissolving  them  in  as  small  a  quantity 
as  possible  of  hot  alcohol.  On  cooling,  the  greater  part  of  the  solid  acid 
separates  out,  while  the  oleic  acid  remains  in  solution,  and  may  be  sepa- 

*  RechercJies  snr  fcs  cnrps  f/rns  <T<iriti!ne  animilf..     Paris,  1823. 

f  For  references  to  Ileintz's  memoirs,  see  Gmcliu's  Handbook,  vol.  xvi.  p.  343, 


624  MONATOMIC   ACIDS,  CuH2I1Oa. 

rated  by  subjecting  the  mass,  after  draining,  to  strong  pressure,  redissolv- 
ing  the  residue  in  a  small  quantity  of  alcohol,  leaving  it  to  separate  by 
cooling,  and  again  pressing  the  solid  mass.  From  the  mixture  of  solid 
fatty  acids  thus  obtained,  the  stearic  may  be  separated,  in  a  comparatively 
pure  state,  by  repeated  crystallization  from  considerable  quantities  of 
alcohol,  only  the  portion  which  first  separates  being  each  time  collected. 
But  to  obtain  pure  stearic  acid,  it  is  better  to  dissolve  the  impure  stearic 
acid  (4  parts),  melting  at  about  60°  C.  (140°  F.),  in  such  a  quantity  of  hot 
alcohol  that  nothing  will  separate  out  on  cooling,  even  to  0°,  and  mix  the 
hot  liquid  with  a  boiling  alcoholic  solution  of  magnesium  acetate  (1  part). 
The  magnesium-salt  which  separates  on  cooling,  is  pressed  and  boiled  for 
some  time  with  a  large  quantity  of  dilute  hydrochloric  acid,  and  the  stearic 
acid  thereby  separated  is  repeatedly  crystallized  from  alcohol,  till  it  melts 
constantly  at  69°  to  70°  C.  (156°-158°  F.). 

Stearic  acid  is  also  easily  prepared  from  the  fat  of  cocculus-berries, 
which  consists  mainly  of  stearin,  by  saponifying  it  with  potash,  £c.  Ac- 
cording to  Buff  and  Oudemanns,*  the  best  material  for  the  preparation  of 
stearic  acid  is  shea-butter,  which  contains  about  70  per  cent,  stearic,  and  30 
per  cent,  oleic  acid,  but  no  other  solid  fatty  acid. 

On  the  large  scale,  impure  stearic  acid  is  prepared  for  the  manufacture 
of  stearin-candles,  by  saponifying  some  of  the  harder  fats,  generally  with 
lime.  The  resulting  lime-soap,  decomposed  by  sulphuric  acid,  yields  a 
mixture  of  fatty  acids,  which  are  pressed,  first  in  the  cold,  and  afterwards 
at  a  higher  temperature,  in  order  to  separate  the  oleic  acid  from  the  less 
fusible  palmitic  and  stearic  acids.  Another  method,  applied  chiefly  to 
palm-oil,  consists  in  decomposing  the  fat  with  superheated  steam,  as  de- 
scribed under  GLYCERIN  (p.  567).  A  third  method  consists  in  treating  the 
fat  with  sulphuric  acid,  and  distilling  the  product. 

Pure  stearic  acid  crystallizes  from  alcohol  in  nacreous  laminae  or 
needles  ;  it  is  tasteless  and  inodorous,  and  has  a  distinct  acid  reaction.  At 
low  temperatures  it  is  heavier  than  water,  having  a  specific  gravity  of  1*01 
atO°;  but  between  9°  and  10°  C.  (48°-50°  F.),  its  specific  gravity  is  the 
same  as  that  of  water.  It  melts  at  69°-69-2°  C.  (150°  F.)  to  a  colorless 
oil,  which  on  cooling  solidifies  to  a  white,  fine,  scaly,  crystalline  mass, 
lamino-crystalline  on  the  fractured  surface.  When  heated  it  distils,  for 
the  most  part,  without  alteration.  Chlorine  converts  it  into  chlorostearic 
acid,  C,8H35C102.  Heated  with  bromine  and  water  in  a  sealed  tube,  it  is 
converted  into  bromostearic  acid,  C,oHorBr09,  and  dibromostearic  acid. 
C18H34Br202. 

Stearates. — Stearic  acid  dissolves  in  a  cold,  aqueous  solution  of  alkaline 
carbonate,  probably  from  formation  of  acid  carbonate,  and  does  not  expel 
the  carbonic  acid  and  form  a  mono-acid  salt,  till  heated  to  about  100°.  On 
the  other  hand,  the  stearates  are  decomposed  by  most  other  acids,  the 
separated  stearic  acid  rising  to  the  surface  as  an  oil  when  the  liquid  is 
warm.  The  stearates  have  the  consistence  of  hard  soaps  and  plasters,  and 
are  mostly  insoluble  in  water.  The  normal  potassium-salt,  C18H3602K,  sepa- 
rates on  cooling  from  a  solution  of  1  part  stearic  acid  and  1  part  potassium 
hydrate  in  10  parts  of  water,  in  white  opaque  granules.  The  acid  salt, 
ci8ir3502K  •  Ci8H36°2>  is  obtained  by  decomposing  the  normal  salt  with  1000 
parts  or  more  of  water,  and  separates  in  silvery  scales  from  solution  in 
boiling  alcohol.  Normal  sodium  stearate,  C,8H3502Na,  is  very  much  like  the 
potassium-salt,  but  harder.  The  acid  salt,  C18ll3502Na .  C18H3602,  obtained 
by  decomposing  the  normal  salt  with  2000  parts  or  more  of  water,  sepa- 
rates from  the  hot  solution  in  nacreous  laminae.  The  stearates  of  the 
earth-metals  and  heavy  metals  are  insoluble  in  water,  and  are  obtained  by 
precipitation. 

*  Journal  fur  praktiscbe  Chemie,  Ixxxix.  215, 


AKACHIDIC  —  BENIC  —  CEKOTIC   ACID.  625 

Soaps  consist  of  mixtures  of  the  sodium  or  potassium-salts  of  stearic, 
palmitic,  oleic,  and  other  fatty  or  oily  acids,  and  are  produced  by  saponifying 
tallow,  olive  oil,  and  other  fats  with  caustic  alkalies.  The  soda-soaps  are 
called  hard  soaps :  they  separate  from  the  alkaline  liquor,  on  addition  of 
common  salt,  in  hard,  unctuous  masses,  which  are  the  soaps  in  common 
use :  this  mode  of  separation  is  called  salting  out.  The  potash  soaps,  on 
the  other  hand,  cannot  be  thus  separated ;  for  on  adding  salt  to  their  solu- 
tion, they  are  decomposed  and  converted  into  soda-soaps;  but  they  are  ob- 
tained in  a  semi-solid  state  by  evaporating  the  solution.  The  products, 
called  soft  soap,  always  contain  a  considerable  excess  of  alkali,  and  are  used 
for  cleansing  and  scouring  when  a  powerful  detergent  is  required. 

Stearic  ethers  are  formed  by  heating  stearic  acid  with  alcohols,  mon- 
atomic  or  polyatomic.  Ethyl  stearate,  C,8H3502  ..C2H5,  is  most  easily  obtained 
by  passing  hydrochloric  acid  gas  into  an  alcoholic  solution  of  stearic  acid. 
It  resembles  white  wax,  is  inodorous  and  tasteless,  melts  at  80°  C.  (86°  F.), 
and  cannot  be  distilled  Avithout  decomposition.  It  is  readily  decomposed 
by  boiling  with  caustic  alkalies.  There  are  three  glyceryl  stearates  or  stearins, 
analogous  in  composition  to  the  palmitins:  Monostearin,  (C3H5)///(OH) 
(CjgHggOjj),  prepared  by  heating  a  mixture  of  equal  parts  of  stearic  acid 
and  glycerin  to  200°  C.  (392°  F.),  in  a  sealed  tube  for  36  hours,  forms  very 
small  white  needles,  melting  at  61°  C.  (142°  F.),  and  solidifying  again  at 
60°  C.  (140°  F.).—  Distearin,  (C3H5)///OH(C18H3502)2,  obtained  by  heating 
monostearin  with  3  parts  of  stearic  acid  to  260°  C.  (500°  F. ),  for  three  hours, 
forms  white  microscopic  laminoe,  melts  at  58°  C.  (136°  F.),  and  solidifies 
at  55°  C.  (131°  F.).  —  Trislearin  is  prepared  by  heating  monostearin  with  15 
to  20  times  its  weight  of  stearic  acid  to  270°  C.  (518°  F.),  for  three  hours 
in  a  sealed  tube ;  also  from  various  solid  natural  fats  by  solution  in  ether 
and  repeated  crystallization  from  the  hot  solution.  It  crystallizes  in  masses 
of  white  pearly  laminae  or  needles,  inodorous,  tasteless,  neutral,  and  vola- 
tilizing without  decomposition  under  reduced  pressure.  Both  natural 
and  artificial  tristearin  exhibit  three  isomeric  or  allotropic  modifications. 
Stearin,  separated  from  ether,  melts  at  69-7°  C.  (157°  F.) ;  but  if  heated  to 
73-7°  C.  (164°  F.),  or  higher,  and  then  cooled,  it  does  not  solidify  till  cooled 
to  51-7°  C.  (124°  F.).  It  is  solid  below  52°  C.  (125°  F.),  but  melts  at  that 
temperature,  and  if  heated  a  few  degrees  higher,  passes  into  a  third  modi- 
fication, which  does  not  melt  below  64-2°  C.  (148°  F.).* 

Arachidic  Acid,  C20H4002,  is  a  fatty  acid  obtained  by  saponification  of  oil 
of  earth-nut  (Arachis  hypoysea}.  It  crystallizes  in  very  small,  shining  scales, 
melts  at  75°  C.  (167°  F.),  and  solidifies  again  at  73-5°  C.  (164°  F.),  to  a  ra- 
diated crystalline  mass.  It  is  but  slightly  soluble  in  cold  alcohol  of  ordi- 
nary strength,  but  dissolves  easily  in  boiling  absolute  alcohol  and  in  ether. 

The  silver-salt,  C20H3902Ag,  is  a  white  precipitate,  which  separates  from 
boiling  alcohol  in  slightly  lustrous  prisms,  not  altered  by  exposure  to  light. 
Ethyl  arachidate,  C20H3902 .  C2H6,  is  a  crystalline  mass,  melting  at  52-5°  C. 
•(120°  F.).  Berthelot  has  obtained  three  glyceryl  arachidates  or  arachins, 
analogous  to  the  stearins,  by  heating  the  acid  with  glycerin  in  sealed  tubes. 


by  saponification  of  oil  of  ben,  the  oil  expressed  from  the  fruits  of  Moringa 
Nux  Behen.  It  is  a  white  crystalline  fat,  melting  at  76°,  and  solidifying  at 
70°  C.  (158°  F.). 

Cerotic  Acid,  C^II^Oj. — This  acid  is  the  essential  constituent  of  cerin,  the 
portion  of  bees'-wax  which  is  soluble  in  boiling  alcohol.  It  is  prepared  by 
heating  the  wax  several  times  in  succession  with  boiling  alcohol,  till  the 

*  Duffy,  Chem.  Soc.  Journal,  vol.  v.,  pp.  197,  303. 

63 


626 


MONATOMIC   ACIDS,  CnH2n_2O2. 


deposit,  which  forms  on  cooling,  melts  at  70°  or  72°  C.  (158°-162°  F.),  and 
may  be  further  purified  by  precipitating  it  from  the  boiling  alcoholic  solu- 
tion with  lead  acetate,  decomposing  the  precipitate  with  strong  acetic  acid, 
and  crystallizing  the  separated  acid  from  boiling  alcohol.  Cerotic  acid  is 
also  produced  by  the  dry  distillation  of  Chinese  wax,  which  consists  of 
ceryl  cerotate,  C^H^C^ .  C^H55,  or  by  melting  that  substance  with  potash, 
and  decomposing  the  resulting  potassium-salt  with  an  acid  (p.  543). 

Pure  cerotic  acid  crystallizes  in  small  grains,  melting  at  78°  C.  (172°  F.), 
and  distilling  without  alteration.  Chlorine  converts  it  into  chlorocerotic 
acid,  C27H42C11202,  a  thick  transparent  gum  of  a  pale-yellow  color. 

Ceryl  cerotate,  or  Chinese  wax,  is  produced  on  certain  trees  in  China  by  the 
puncture  of  a  species  of  coccus.  It  is  crystalline,  of  a  dazzling  whiteness, 
like  spermaceti,  melts  at  82°  C.  (180°  F.)  ;  dissolves  in  alcohol ;  yields 
cerotic  acid  and  cerylene,  C^H^,  by  dry  distillation.  It  is  used  in  China 
for  making  candles. 

Melissic  Acid,  CgoH^Og,  the  highest  known  member  of  the  fatty  series,  is 
obtained  by  heating  myricyl  alcohol  (p.  543)  with  potash  lime : 


Myricyl 
alcohol. 


KOH 


=  C30H5902K 
Potassium, 
melissate. 


2H, 


It  bears  considerable  resemblance  to  cerotic   acid,  but  melts  at  a  higher 
temperature,  viz.,  at  88°  or  89°  C.  (190°-192°  F.).  The  silver-salt,  C^ 
is  a  white  precipitate. 


Monatomic  Acids  of  the  Series  CnH2n_202.  —  Acrylic  Series. 

This  series  comprises  two  isomeric  groups  of  acids :  the  one  consisting 
of  acids  occurring  in  the  vegetable  or  animal  organism,  or  obtained  from 
natural  products  by  special  processes  ;  the  other  of  acids  formed  by  a  gen- 
eral synthetical  process:  we  shall  designate  the  acids  of  the  first  group  as 
normal  acrylic  acids,  those  of  the  second  as  isoacrylic  acids. 

Normal  Acrylic  Acids. 
The  following  are  the  known  acids  of  this  group : 

Acrylic  acid     . 

Crotonic  acid 

Angelic  acid     . 

Pyroterebic  acid . 
?  Damaluric  acid 
?  Damolic  acid        .         .         C13H2402     Doeglic  acid      .         .         .    C19H3602 

Moringic  acid  "I 

Cimicic  acid    / 

Most  of  these  acids  are  oily  liquids.  When  fused  with  potassium  hydrate, 
they  yield  the  potassium-salt  of  acetic  and  of  another  acid  of  the  fatty 
series,  with  elimination  of  hydrogen,  thus : 


C3H402 

Physetoleic  acid 

C4H602 
C6H802 

Hypogseic  acid 
Gai'dic  acid 

C6  H1002 

Oleic  acid     ) 

C  H   0 

Elai'dic  acid  / 

CXX 

Doeglic  acid 

C15H2802 

Brassic  acid  ~) 
Erucic  acid  J 

2KOH 


Acrylio 
acid. 


Angelic 
acid, 


==     C2H3K02 
Acetate. 


2KOH    = 


Acetate. 


CHK02 
Formate. 


C3H5K02 
Propionate, 


ACRYLIC  —  CROTONIC — ANGELIC    ACID.  627 

C^HsA     +     2KOH    =    C2H3K02    +       C16H31K02       -f     H, 
Oleic  acid.  Acetate.  Palmitate. 

Generally : 

CaH2n_202    +     2KOH     =    C2H3K02     +    Cn_2H2n_6K02     +     H2 
They  are  also  converted  into  fatty  acids  by  the  action  of  nascent  hydrogen ; 

C4H602        +        H2        =         C4H802 

Crotonic  Butyric 

acid.  acid. 

Acrylic  Acid,  C3H402,  is  produced  by  the  oxidation  of  its  aldehyde,  acro- 
lein,  C3H40,  with  moist  silver  oxide.  It  is  a  colorless  liquid,  having  a 
slightly  empyreumatic  odor,  and  miscible  in  all  proportions  with  water. 
Its  salts  resemble  the  formates  and  acetates,  and  are  for  the  most  part  very 
soluble  in  water. 

Acrylic  acid  is  converted  by  nascent  hydrogen  into  propionic  acid, 
C3H602,  and  by  bromine  into  dibromopropionic  acid,  C3H4Br202. 

Crotonic  Acid,  C4H602,  is  produced  by  saponification  of  the  oil  of  Croton 
Tiglium.  It  is  an  oily  liquid,  having  a  somewhat  pungent  odor  and  an  acrid 
taste,  moderately  soluble  in  pure  water,  insoluble  in  saline  water.  Heated 
with  potassium  hydrate  it  gives  off  hydrogen  and  forms  two  molecules  of 
potassium  acetate : 

C4H602        +        2KOH        =        2C2H3K02        +        H2. 

Angelic  Acid,  C5H802,  exists  in  the  root  of  the  archangel  (Angelica  arch- 
angelica],  and  in  sumbul  or  moschus  root,  a  drug  imported  from  Asia  Minor, 
and  probably  also  belonging  to  an  umbelliferous"  plant.  It  is  obtained  from 
archangel-root,  by  boiling  the  root  with  lime  and  water,  and  distilling  the 
strained  and  concentrated  liquid  with  dilute  sulphuric  acid.  It  is  also  pro- 
duced by  heating  the  essential  oil  of  chamomile,  which  consists  of  angelic 
aldehyde  together  with  a  hydrocarbon,  with  potassium  hydrate: 

C5H80        +        KOH        =        C7H7K02        -f         H2. 

Also,  together  with  oreoselin,  by  treating  peucedanin  or  imperatorin  (a 
•neutral  substance  contained  in  the  root  of  Imperaloria  Ostruthium,  and  some 
other  umbelliferous  plants),  with  alcoholic  potash : 

C,,HI20,        -f         KOH        =        C5H7K02        -f        C7H602 
Peucedanin.  Potassium  Oreoselin. 

angelate. 

Angelic  acid  crystallizes  in  long  prisms  and  needles,  melts  at  45°  C.  (113° 
F.),  boils  at  190°  C.  (374°  F.),  and  distils  without  decomposition.  It  has 
an  aromatic  taste  and  odor,  dissolves  sparingly  in  cold,  abundantly  in  hot 
water,  also  in  alcohol  and  ether. 

The  angelates  of  the  alkali-metals  are  soluble  in  water  and  in  alcohol. 
Calcium  angclate,  (C5H702)2Cax/.  Aq.,  forms  shining,  very  soluble  laminae. 
The  lead-salt,  (C5H7O2)2Pb//,  is  a  white  precipitate. 

Potassium  angclate  treated  with  phosphorus  oxychloride  yields  angelic 
oxide,  or  anhydride,  (C5II70)20,  which  is  a  viscid  uncrystallizable  oil,  boil- 
ing at  240°  C.  (464°  F.). 

Pyroterebic  acid,  C6H1002,  is  produced  by  dry  distillation  of  terebic  acid, 
C7II]0O4  (one  of  the  products  of  the  action  of  nitric  acid  on  turpentine  oil). 
It  is  a  liquid,  boiling  at  210°  C.  (410°  F.).—J)amaluric  acid,  C7H12C2,  and 
Damolic  acid,  C,3H2402,  are  volatile  acids,  said  to  exist  in  the  urine  of  cows 


628  MONATOMIC   ACIDS,  CnH2n_aO2. 

and  horses. — Moringic  acid,  C,5H2802,  is  an  oily  acid  obtained,  together  with 
palmitic,  stearic,  and  benic  acids,  by  the  saponification  of  oil  of  ben  (p. 
625).  —  Cimicic  acid  is  a  yellow  crvstallizable  acid,  having  a  rancid  odor, 
extracted  by  alcohol  and  ether  from  a  kind  of  bug  (Raphigaster  puncti- 
pennis). 

Hypogseic  Acid,  C,6H3002,  is  contained,  as  a  glyceride,  together  with  pal- 
mitin  and  arachin,  in  oil  of  earth-nut  (Arachis  hypogiea}.  To  obtain  it,  the 
mixture  of  fatty  acids  obtained  by  saponifying  the  oil,  is  dissolved  in  alco- 
hol; the  palmitic  and  arachidic  acids  are  precipitated  by  ammonia  and 
magnesium  acetate;  the  filtrate  is  mixed  with  ammonia  and  lead  acetate; 
the  lead  precipitate  is  decomposed  by  hydrochloric  acid ;  and  the  separated 
hypogseic  acid  is  dissolved  out  by  ether.  It  is  also  produced  by  oxidation 
of  axinic  acid  (C^H^O^),  an  acid  obtained  by  saponification  of  age  or  axin, 
a  fatty  substance  contained  in  the  Mexican  plant  Coccus  Axin.  —  Hypogasic 
acid  crystallizes  from  ether  in  stellate  groups  of  needles,  melting  at  34°  or 
35°  C.  (93°-95°  F.),  easily  soluble  in  alcohol  and  ether.  Its  potassium  and 
sodium  salts  are  soluble  in  water,  the  barium  salt  is  soluble  in  hot,  insoluble 
in  cold  water;  the  copper  and  silver  salts  are  obtained  by  precipitation. 
The  ethylic  ether,  C16H2902.  C2H5,  is  a  yellow  oil,  not  volatile  without  decom- 
position. 

Nitrous  acid  converts  hypogaoic  acid  into  the  isomeric  or  allotropic  com- 
pound, Ga'idic  acid,  related  to  it  in  the  same  manner  as  elai'dic  acid  to  oleic 
acid.  It  forms  a  colorless  crystalline  mass  which  melts  at  38°  C.  (100°  F.). 

Physetolcic  acid,  a  crystalline  acid  obtained  from  sperm-oil,  is  isomeric,  if 
not  identical,  with  hypogeeic  acid ;  it  melts  at  30°,  and  solidifies  at  28°  C. 
(82°  F.). 

Oleic  Acid,  C]8H3402.  —  This  acid,  the  most  important  of  the  series,  is  ob- 
tained by  saponification  of  olein,  the  fluid  constituent  of  most  natural  fats 
and  fixed  oils. 

To  obtain  pure  oleic  acid,  olive  or  almond  oil  is  saponified  with  potash; 
the  soap  is  decomposed  by  tartaric  acid ;  and  the  separated  fatty  acid,  after 
being  washed,  is  heated  for  some  hours  in  the  water-bath,  with  half  its 
weight  of  lead  oxide  previously  reduced  to  fine  powder.  The  mixture  is 
then  well  shaken  up  with  about  twice  its  bulk  of  ether,  which  dissolves  the 
oleate  of  lead  and  leaves  the  stearate ;  the  liquid  after  standing  for  some 
time  is  decanted  and  mixed  with  hydrochloric  acid ;  the  oleic  acid  thereby 
eliminated  dissolves  in  the  ether,  and  the  ethereal  solution,  which  rises  to 
the  surface  of  the  water,  is  decanted,  mixed  with  water,  and  freed  from 
ether  by  distillation. 

Large  quantities  of  crude  oleic  acid  are  now  obtained  in  the  manufacture 
of  stearin-candles,  by  treating  with  dilute  sulphuric  acid  the  lime-soap 
resulting  from  the  action  of  lime  upon  tallow.  The  fatty  acids  resulting 
from  the  decomposition  are  washed  with  hot  water,  and  solidify  in  a  mass 
on  cooling;  and  this  mass,  when  subjected  to  pressure,  yields  a  liquid  rich 
in  oleic  acid,  but  still  retaining  a  considerable  quantity  of  stearic  acid. 
After  remaining  for  some  time  in  a  cold  place,  it  deposits  a  quantity  of 
solid  matter,  and  the  liquid  decanted  from  this  is  sent  into  the  market  as 
oleic  acid  or  red  oil.  It  may  be  purified  by  the  process  just  described. 

Oleic  acid  crystallizes  from  alcoholic  solution  in  dazzling  white  needles, 
melting  at  14°  C.  (57°  F.)  to  a  colorless  oil,  which  solidifies  at  4°  C.  (39°  F.) 
to  a  hard,  white  crystalline  mass,  expanding  considerably  at  the  same  time. 
Specific  gravity  =  0-808  at  19°  C.  (66°  F.).  The  acid  volatilizes  in  a  va- 
cuum without  decomposition.  It  is  tasteless  and  inodorous,  and  reacts  neu- 
tral when  unaltered  (not  oxidized),  also  in  alcoholic  solution.  It  is  insoluble 
in  water,  very  soluble  in  alcohol,  and  dissolves  in  all  proportions  in  ether. 
Cold  strong  sulphuric  acid  dissolves  it  without  decomposition.  It  dissolves 


OLEIC   AND    ISO-ACRYLIC   ACIDS.  629 

solid  fats,  stearic  acid,  palmitic  acid,  &c.,  and  is  dissolved  by  bile,  with 
formation  of  a  soap  and  strong  acid  reaction. 

Oleic  acid,  in  the  solid  state,  oxidizes  but  slowly  in  the  air;  but  when 
melted,  it  rapidly  absorbs  oxygen,  acquiring  a  rancid  taste  and  smell  and 
a  decided  acid  reaction.  Its  decomposition  by  fusion  with  potash  has  been 
already  mentioned.  Chlorine  and  bromine,  in  presence  of  water,  convert  it 
into  dichloroleic  and  dibromoleic  acid.  Bromine,  added  by  drops  to  fused 
oleic  acid,  forms  tribromoleic  acid,  CJ8H31Br302. 

Strong  nitric  acid  attacks  oleic  acid  with  violence,  giving  off  red  nitrous 
vapors,  and  producing  volatile  acids  of  the  series  CnH2n02,  viz.,  acetic,  pro- 
pionic,  butyric,  valeric,  caproic,  cenanthylic,  caprylic,  pelargonic,  and  rutic 
acids;  also  fixed  acids  of  the  series  CnH2n-402,  viz.,  suberic,  pimelic,  adipic, 
lipic,  and  azelaic  acids,  the  number  and  proportion  of  these  products  vary- 
ing with  the  duration  of  the  action. 

Nitrous  add  converts  oleic  acid  into  a  solid  isomeric  or  allotropic  modifi- 
cation, called  ela'idic  acid. 

Oleates.— ThQ  formula  of  the  neutral  oleates  isCl8H3302M,  or  (C18H3302)2M//, 
according  to  the  equivalence  of  the  metal;  there  are  likewise  acid  oleates. 
The  neutral  oleates  of  the  alkali-metals  are  soluble  in  water,  and  not  so  com- 
pletely precipitated  from  their  solutions  by  the  addition  of  another  soluble 
salt,  as  the  stearates  and  palmitates.  The  acid  oleates  are  liquid  and  in- 
soluble in  water.  The  oleates  dissolve  in  cold  absolute  alcohol  and  in 
ether,  a  property  by  which  they  may  be  distinguished  and  separated  from 
the  stearates  and  palmitates. 

Oleins.  — Oleic  acid  forms  three  glycerides,  viz.,  monolein,  (C3H5)///(OH) 
(C,8H330?);  diolein,  (C3H5)^(OH)(CI8H3302)2;  and  triolein,  (C8HB)'"(C18HB 
02)3,  which  are  produced  by  heating  oleic  acid  and  glycerin  together  in 
sealed  tubes  in  various  proportions.  The  first  two  solidify  at  about  15°. 

The  olein  of  animal  fats,  and  of  olive  oil  and  several  other  oils,  both  ani- 
mal and  vegetable,  which  do  not  dry  up  in  the  air  by  slow  oxidation,  but 
are  converted  into  viscid  masses  having  a  rancid  odor  and  acid  reaction 
(non-drying  oils),  appears  to  be  identical  with  triolein,  but  there  is  great 
difficulty  in  obtaining  it  pure.  Olive  oil,  cooled  to  4°  C.  (39°  F.)  or  a  lower 
temperature,  deposits  a  large  quantity  of  solid  fat,  consisting  mainly  of 
palmitin  (originally  called  margarin,  from  its  pearly  lustre),  and  the  oil 
filtered  therefrom  consists  mainly  of  olein.  A  purer  olein  is  obtained  by 
treating  olive  oil  with  a  cold  strong  solution  of  caustic  soda,  which  saponi- 
fies the  solid  fats,  and  leaves  the  olein  unaltered.  Olein,  subjected  to  dry 
distillation,  yields  gaseous  products,  liquid  hydrocarbons,  acrolein,  and 
sebic  acid. 

Some  non-drying  oils  contain  the  glycerides  of  acids  homologous  with 
oleic  acid  ;  such  is  the  case,  as  already  observed,  with  croton-oil,  earth-nut 
oil,  and  sperm-oil.  Doegling  train-oil,  obtained  from  the  doegling  or  bottle- 
nosed  whale  (Balama  rostrata),  yields  doealic  acid,  C^H^O^  Colza-oil,  ob- 
tained from  the  seeds  of  certain  species  of  Brassica,  especially  the  summer 
rape  or  colza,  Brassica  campestris,  var.  oleifera,  yields  brassic  acid,  C2.,H4202; 
and  the  oil  of  black  mustard-seed  yields  a  similar  and  probably  identical 
acid,  called  erucic  acid. 

Drying  oils,  such  as  linseed  and  poppy  oils,  and  castor-oil  which  is  a 
non-drying  oil,  contain  the  glycerides  of  acids  belonging  to  other  series, 
which  will  be  noticed  hereafter. 


Iso-acrylic  Acids. 

Acids  isomeric  with  the  natural  acrylic  acids  are  produced  by  abstraction 
of  the  elements  of  water  from  certain  acid  ethers,  having  the  composition 


630 


MONATOMIC    ACIDS,  CuH2n_2O2. 


of  oxalic  acid  in  which  one  atom  of  oxygen  is  replaced  by  two  equivalents 
of  an  alcohol-radical  of  the  series,  CnH2n4-1: 


CH 


CH2CH3 
HO—  C—  CH3 

HO—  C:=0 

Ethometh- 
oxalic  acid. 

CH2CH3 
HO—  C—  CH2CH3 

HO—  C=0 

Dieth  oxalic 
acid. 

HO—  C=0       HO—  C—  CH 

HO—  C=0       HO—  0=0 
Oxalic  acid.    Dimethoxalic 

acid. 

Now,  when  the  ethylic  ethers  of  these  acids  are  treated  with  phosphoric 
oxide  or  phosphorus  trichloride,  they  give  up  a  molecule  of  water  (OH2), 
at  the  expense  of  one  of  the  molecules  of  hydroxyl  (OH)  and  an  atom  of 
hydrogen  abstracted  from  one  of  the  monad  alcohol-radicals,  which  is 
thereby  converted  into  a  dyad  radical  (an  olefine)  capable  of  saturating  the 
unit  of  equivalence  of  the  carbon-atom  set  free  by  abstraction  of  the  hy- 
droxyl. The  product  is  the  ethylic  ether  of  an  iso-acrylic  acid  ;  thus, 


CH 


HO—  C 


—  CH, 

I 
H6C20—  C=0 

Ethylic  dimeth- 
oxalate. 


-        OH2        = 


H2C=C—  CH3 

| 
H6C20—  C=0 

Ethylic  methyl- 
acrylate. 


The  ethylic  ether  thus  formed  is  converted  into  methacrylic  acid  by  saponi- 
fication  with  potash  in  the  usual  way.  In  this  manner  the  following  iso- 
acrylic  acids  have  been  obtained  : 

C(CH3)(CH2)" 
Methacrylic  acid  .  .  .  |  isomeric  with  Crotonic  acid 

COOH 


C(CH3)(C2H4)" 
Methylcrotonic  acid  .  | 

COOH 

C(C2H5)(C2H4)" 
Ethylcrotonic  acid  .  .  | 

COOH 


Angelic  acid 


Pyroterebic  acid 


The  actual  formation  of  the  ethers  of  these  acids,  by  the  action  of  phos- 
phoric oxide  and  phosphorous  chloride  on  the  oxalic  compounds  above 
mentioned,  takes  place  in  the  manner  shown  by  the  following  equations: 


C(OH)(CH3)(C2H6) 


C 


Ethylic  ethometh- 
oxalate. 

C(OH)(C2H6)2 


Phosphoric 
oxide. 


C(CH3)(C2H4) 


Ethylic  methyl-    Metaphos- 
crotonate.         phoric  acid. 

C(C2H,)(C2HJ" 
' 


Ethylic  dieth-  Phosphor-  Ethylic*  Phosphor- 

oxalate.  ous  chloride,     ethyl-crotonate.  ous  acid. 

The  iso-acrylic  acids,  when  fused  with  potassium  hydrate,  are  converted, 
like  the  normal  acrylic  acids,  into  two  acids  of  the  acetic  series.  The  dyad 
radical  of  the  iso-acrylic  acid  is  displaced  by  two  atoms  of  hydrogen  de- 
rived from  two  molecules  of  potassium  hydrate  (2KOH),  and  enters  into 


ISO-ACRYLIC   ACIDS.  631 

combination  with  two  atoms  of  oxygen;  and  at  the  same  time  the  two 
atoms  of  potassium  displace  the  basic  hydrogen-atoms  of  the  two  acids  thus 
produced,  converting  them  into  potassium-salts,  and  expelling  the  hydro- 
gen as  gas;  thus: 


C(CH2)"CH3 

CH2CH3 

H 

COOH 

2KOH  =    1 
COOK 

COOK 

Methacrylic 

Propionate. 

Formate. 

acid. 

C(C,H4)"CH§ 

CH2CH3 

CH3 

I                        -f 
COOH 

2KOH  =    1 
COOK 

COOK 

Methyl-cro- 

Propionate. 

Acetate. 

tonic  acid. 

C(C2H4)"C2H6 

CH2C2H6 

CH3 

COOH 

2KOH  =    | 
COOK 

+    1 
COOK 

Ethyl-cro- 

Butyrate. 

Acetate. 

tonic  acid. 

+ 


The  normal  acrylic  acids  are  decomposed  by  potash  in  a  similar  manner, 
yielding  two  acids  of  the  series,  Cn  H2n02 ;  but  one  of  these  is  always  acetic 
acid.  Hence  it  is  inferred  that  they  have  a  constitution  represented  by 

C(CQH2n)"H 
the  formula  I  ,  and  that  their  decomposition  by  potash  is  rep- 

COOH 
resented  by  the  equation  : 

C(CnH2n)"H  CH,  Cn-.EU..! 

|  +     20H2     =1  +|                      +     H2 

COOH  COOH               COOH 

Iso-acrylic  Acetic           Homologue  of 

acid.  acid.              acetic  acid. 

The  formulae  of  the  individual  acids  are  as  follows : 
CH(CH,)"     CH(CaH4)"     CH(C8H6)"    CH(C4H8)"        CH(C16H32) 

COOH  COOH  COOH  COOH  '  '  COOH 

Acrylic.         Crotonic.         Angelic.       Pyroterebic.  Oleic. 

It  is  easily  seen  from  these  formulae  that  crotonic  acid,  when  decomposed 
by  an  alkali,  must  yield  two  molecules  of  acetic  acid;  and  that  the  other 
acids  above  formulated  must  yield  acetic  acid  together  with  formic,  pro- 
pionic,  butyric,  and  palmitic  acids  respectively. 

An  acid  isomeric  with  crotonic  acid,  and  differing  from  methacrylic  acid, 
has  been  obtained  by  boiling  allyl  cyanide  with  caustic  potash: 

C3H5CN     +     KOH     -}-     OH2    =    NH3    +     C4H5K02 

CH(CH2)" 

Frankland  assigns  to  this  acid  the  composition  CH2 

COOH 

There  is  also  an  acid  called  campholic  acid,  C]0H,602,  produced  by  heating 
common  camphor,  C^H^O,  with  potassium  hydrate.  It  cannot  be  included 
in  either  of  the  series  of  acrylic  acids,  inasmuch  as  it  does  not  exhibit  the 


632  MONATOMIC   ACID,  CuH2n_6O2. 

reactions  of  either.  It  is  a  white  crystalline  body,  insoluble  in  water, 
soluble  in  alcohol  and  ether,  decomposed  by  distillation  with  phosphoric 
oxide,  into  carbon  monoxide,  water,  and  campholene,  C9HJ6. 


Monatomic  Acids  belonging  to  the  series  CnH2n_402,  or  CnH2n_50(OH). 

Only  three  acids  of  this  series  are  known,  viz. :  sorbic  and  parasorbic 
acids,  both  having  the  composition  C6H802,  and  camphic  acid,  C^H^O.^. 

Parasorbic  acid  is  a  volatile  oily  acid  obtained  from  mountain-ash  berries; 
sorbic  acid  is  a  crystallizable  acid  produced  from  it  by  gentle  heating  with 
solid  potash,  or  boiling  with  strong  hydrochloric  acid;  it  melts  at  134-5° 
C.  (274°  F.),  volatilizes  without  decomposition,  and  decomposes  carbonates. 

Camphic  acid,  C10H1602,  is  obtained,  together  with  the  corresponding  alco- 
hol, camphol  (p.  546),  by  heating  common  camphor  with  alcoholic  soda- 
solution  in  sealed  tubes  to  170°-190°  C.  (338°-374°  F.). 

2C10HW0     +     OH2    =     C10H180     +     C10H1602 
Camphor.  Camphol.  Camphic 

acid. 

By  neutralizing  the  resulting  alkaline  solution  with  sulphuric  acid,  dis- 
solving out  the  sodium  camphate  with  alcohol,  evaporating,  and  again  adding 
sulphuric  acid,  the  camphic  acid  is  obtained  as  a  solid  mass  heavier  than 
water,  insoluble  therein,  easily  soluble  in  alcohol.  The  potassium  and 
sodium  salts  are  insoluble  in  strong  alkaline  lyes.  They  precipitate  the 
salts  of  copper,  iron,  silver,  and  zinc,  not  those  of  the  alkali-metals ;  all 
the  precipitates  are  soluble  in  a  large  quantity  of  water. 


Monatomic  Acid  belonging  to  the  series  CnH^^C-.,. 

Ilydrobenzoic  acid,  C7H1002,  or  C7H90(OH).* —  This  acid,  corresponding 
to  the  unknown  alcohol,  C7H120,  is  formed,  together  with  other  products, 
by  the  action  of  sodium  amalgam  on  benzoic  acid: 

C7H602        +        2H2        =        C7H1002 
Benzoic  Hydroben- 

acid.  zoic  acid. 

It  is  more  easily  obtained,  however,  by  boiling  hydrobenzyluric  acid  (a 
product  of  the  decomposition  of  hippuric  acid  by  sodium  amalgam)  with 
alkalies  in  a  close  vessel: 

C16H21N04    +     OH2    =    C2H5N02    +     C7H80     +     C7H1002 

Hydrobenzyl-  Glycocine.  Benzyl          Hydroben- 

uric  acid.  alcohol.          zoic  acid. 

It  is  a  crystalline  acid,  forming  a  crystalline  calcium  salt,  (C7H902)2Ca, 
and,  when  recrystallized  either  in  the  free  state  or  in  the  form  of  calcium 
salt,  is  ultimately  converted  by  oxidation  into  benzoic  acid.  Its  ethylic 
ether,  C7H902 .  C2H5,  has  the  odor  of  ethyl  valerate. 

*  M.  Hermann,  Ann.  Ch.  Pharm.  cxxxii.  75.  —  R.  Otto,  ibid,  cxxxiv.  303. 


BENZOIC    ACID.  633 


Monatomic  Acids  belonging  to  the  series  OH2n_802.  —  Aromatic  Acids. 

These  acids  are  produced  by  some  of  the  processes  which  yield  the  fatty 
acids,  viz. — 1.  By  the  oxidation  of  the  corresponding  aldehydes  and  primary 
alcohols:  thus  benzoic  acid,  C7H802,  is  formed  by  oxidation  of  benzole 
aldehyde,  C7H60,  and  of  benzylic  alcohol,  C7H80. — 2.  By  the  action  of 
water  on  the  corresponding  acid  chlorides.  —  3.  By  the  action  of  alkalies 
on  the  cyanides  of  aromatic  alcohol-radicals. 

They  are  likewise  obtained :  4.  By  the  simultaneous  action  of  sodium  and 
carbon  dioxide  on  the  monobrominated  derivatives  of  the  aromatic  hydro- 
carbons: thus, 

C6H5Br     +     Na    -f     C02    =    NaBr    -f-     C7H5Na02 
Bromo-  Sodium 

benzene.  benzoate. 

5.  Certain  aromatic  acids  are  produced  by  the  oxidation  of  hydrocar- 
bons homologous  with  benzene. 

The  known  acids  of  this  series  are : 

Benzoic  acid,  C7H602. 

Toluic  and  Alpha-toluic  acids,  C8H802. 

Xylic  and  Alpha-xylic  acids,  C9H1002. 

Cumic  acid,  C10H1202,  homologous  with  toluic  acid. 

Alpha-cymic  acid,  C11HU02,  homologous  with  alpha-toluic  acid. 

Benzoic  Acid,  C7H602  =  C7H50(OH).— This  acid  is  the  analogue  of  ben- 
zylic alcohol,  and  is  produced  from  it  by  oxidation  with  aqueous  chromic 
acid: 

C6H5.CH2OH     +     02    =    OII2    -f     C6H5.COOH 

Benzyl  al-  Benzoic 

cohol.  acid. 

It  is  also  formed  by  oxidation  of  benzoic  aldehyde,  C7H60  (bitter-almond 
oil),  in  presence  of  platinum  black,  or  with  nitric  acid. 

It  may  be  produced  directly  from  benzene,  by  acting  upon  that  com- 
pound in  the  state  of  vapor  with  carbonyl  chloride  (phosgene  gas)  whereby 
.it  is  converted  into  benzoyl  chloride,  and  decomposing  this  chloride  with 
water : 

C6H6      +      COC12      =      HC1      -f      C7H5OC1 

Benzene.          Carbonyl  Benzoyl 

chloride.  chloride. 

C7H6OC1        +        OH2        =        HC1        -f        C7H60(OH) 
Benzoyl  Benzoic 

chloride.  acid. 

Fourthly,  it  is  obtained  by  boiling  hippuric  acid  (or  the  urine  of  cows 
or  horses  which  contains  that  acid)  with  hydrochloric  acid.  The  hippuric 
acid,  C(jH9NO3,  which  has  the  composition  of  benzoyl-glycocine,  then  takes 
up  a  molecule  of  water,  and  is  resolved  into  glycocine  (p.  G14)  and  benzoic 
acid: 

C2H4(C7H60)N02    +     OH2    =    C2H6N02    -f-     C7H602 
Hippuric  acid.  Glycocine.  Benzoic 

acid. 

This  process  is  applied  to  the  preparation  of  benzoic  acid  on  the  large 
scale. 

Benzoic  acid  is  also  produced  by  the  oxidation  of  a  great  variety  of  or- 


634  MONATOMIC   ACIDS,  CnH2n_8O2, 

ganic  bodies,  as  cumene,  cinnamic  aldehyde,  cinnamic  acid,  cinnamene, 
casein,  gelatin,  &c. 

Benzoic  acid  exists  ready  formed  in  large  quantity  in  several  balsams 
and  gum-resins,  especially  in    gum-benzoin,  a  resin   which  exudes  from 
the  bark  of  Styrax  benzoin,  a  tree  growing  in  Sumatra,  Java,  Borneo,  and 
Siam.    When  this  substance  is  exposed  to  a  gentle  heat  in  a  subliming  ves- 
sel, the  benzoic  acid  is  volatilized,  and  may  be  condensed.     The  simplest 
and  most  efficient  apparatus  for  this  and  all  similar  operations  is  the  con- 
trivance of  Dr.  Mohr:  it  consists  of  a  shallow  iron  pan,  over  the  bottom 
of    which    the   substance    to    be    sublimed   is    thinly 
Fig.  194.  spread ;  a  sheet  of  bibulous   paper,   pierced  with  a 

number  of  pin-holes,  is  then  stretched  over  the  ves- 
sel, and  a  cap  made  of  thick,  strong  drawing  or  car- 
tridge-paper, is  secured  by  a  string  or  hoop  over  the 
whole.  The  pan  is  placed  upon  a  sand-bath,  and 
slowly  heated  to  the  requisite  temperature ;  the  va- 
por of  the  acid  condenses  in  the  cap,  and  the  crystals 
are  kept  by  the  thin  paper  diaphragm  from  falling 
back  again  into  the  pan.  Benzoic  acid  thus  obtained 
assumes  the  form  of  light,  feathery,  coloi^less  crys- 
tals, which  exhale  a  fragrant  odor,  not  belonging  to 
the  acid  itself,  but  due  to  a  small  quantity  of  volatile 
oil.  A  more  productive  method  of  preparing  the  acid  is  to  mix  the  pow- 
dered gum-benzoin  very  intimately  with  an  equal  weight  of  slaked  lime, 
boil  this  mixture  with  water,  and  decompose  the  filtered  solution,  concen- 
trated by  evaporation  to  a  small  bulk,  with  excess  of  hydrochloric  acid  ; 
the  benzoic  acid  crystallizes  out  on  cooling  in  thin  plates,  which  may  be 
drained  upon  a  cloth  filter,  pressed,  and  dried  in  the  air.  By  sublimation, 
which  is  then  effected  with  trifling  loss,  the  acid  is  obtained  perfectly 
white. 

Benzoic  acid  is  inodorous  when  cold,  but  acquires  a  faint  smell  when 
gently  warmed:  it  melts  just  below  121°  C.  (250°  F.),  and  sublimes  at  a 
temperature  a  little  above ;  it  boils  at  249°  C.  (480°  F.),  and  emits  a  vapor 
of  the  density  of  4-27.  It  dissolves  in  about  200  parts  of  cold  and  25  parts 
of  boiling  water,  and  with  great  facility  in  alcohol.  Benzoic  acid  is  not 
affected  by  ordinary  nitric  acid,  even  at  boiling  heat;  but  with  fuming  nitric 
acid  it  forms  a  substitution-product. — Chlorine  also  acts  on  benzoic  acid, 
forming  substitution-products. — Phosphorus  pentachloride  converts  it  into 
benzoyl  chloride,  C7H5OC1. — Benzoic  acid  dissolves  in  ordinary  strong  sul- 
phuric acid,  but  is  precipitated  unaltered  on  addition  of  water.  By  fuming 
sulphuric  acid,  however,  and  still  more  readily  by  sulphuric  oxide,  it  is 
converted  into  sulphobenzoic  acid,  C7H6S05,  a  bibasic  acid  to  be  described 
hereafter.  By  nascent  hydrogen  (evolved  by  sodium-amalgam)  it  is  partly 
reduced  to  benzoic  aldehyde  and  benzylic  alcohol,  and  is  partly  converted, 
by  addition  of  hydrogen,  into  hydrobenzoic  acid,  C7H1002  (p.  632). 

All  the  benzoates  are  more  or  less  soluble  :  they  are  easily  formed,  either 
directly  or  by  double  decomposition.  The  benzoates  of  the  alkalies  and  of  am- 
monia are  very  soluble,  and  somewhat  difficult  to  crystallize.  —  Calcium  ben- 
zoate forms  groups  of  small  colprless  needles,  which  require  20  parts  of 
cold  water  for  solution.  The  barium  salts  are  soluble  with  difficulty  in  the 
cold.  Neutral  ferric  benzoate  is  a  soluble  compound;  but  the  basic  salt  ob- 
tained by  neutralizing  as  nearly  as  possible  with  ammonia  a  solution  of 
ferric  oxide,  and  then  adding  ammonium  benzoate,  is  quite  insoluble.  Iron 
is  sometimes  thus  separated  from  other  metals  in  quantitative  analysis. 
Neutral  and  basic  lead  benzoate  are  freely  soluble  in  the  cold.  Silver  ben- 
zoate crystallizes  in  thin  transparent  plates,  which  blacken  on  exposure  to 
light. 


BENZOIC   ACID. 


635 


Calcium  benzoate  is  resolved  by  dry  distillation  into  calcium  carbonate 
and  benzone,  or  benzophenone,  C13H100,  the  ketone  of  benzoic  acid: 

(C7HA)2Ca"         =         C03Ca        +        CO(C6H6)2 
Calcium.  l}en-  Benzone. 

zoate. 

On  the  other  hand,  benzoic  acid,  distilled  with  excess  of  lime,  is  resolved 
into  carbon  dioxide  and  benzene: 

C7H602         =         C02        +        C6H6. 

BENZOIC  CHLORIDE,  OR  BENZOYL  CHLORIDE,  C7H5OC1.  —  This  compound, 
derived  from  benzoic  acid  by  substitution  of  chlorine  for  hydroxyl,  is  pre- 
pared by  the  action  of  phosphorus  pentachloride  on  benzoic  acid: 

C7H50(OH)     +     PC13C12    =     POC13    +     HC1     -f     C7H6OC1. 

The  two  substances  are  mixed  in  equivalent  quantities,  and  gently  heated. 
A  brisk  reaction  ensues,  hydrochloric  acid  is  evolved,  while  oxychloride  of 
phosphorus  distils  over;  and  when  the  temperature  rises  to  196°  C.  (884°  F.), 
the  receiver  is  to  be  changed,  and  the  benzoyl  chloride,  which  passes  over 
at  that  temperature,  collected  separately.  It  may  also  be  prepared  by  sub- 
jecting bitter-almond  oil  (C7H60)  to  the  action  of  dry  chlorine  gas.  It  is 
a  colorless  liquid  of  peculiar,  disagreeable,  and  pungent  odor;  its  density 
is  1'106.  The  vapor  is  inflammable,  and  burns  with  a  greenish  flame;  its 
density  (referred  to  air)  is  4-987.  Benzoyl  chloride  is  decomposed  slowly 
by  cold  and  quickly  by  boiling  water  into  benzoic  and  hydrochloric  acids : 
with  an  alkaline  hydrate,  a  benzoate,  and  chloride  of  the  alkalic  metal,  are 
generated. 

BENZOYL  IODIDE,  C7H5OI,  is  prepared  by  distilling  the  chloride  with  po- 
tassium iodide:  it  forms  a  colorless,  crystalline,  fusible  mass,  decomposed 
by  water  and  alkalies  in  the  same  manner  as  the  chloride.  The  bromide, 
C7H5OBr,  has  very  similar  properties.  Benzoyl  cyanide,  C7H50 .  CN,  ob- 
tained by  heating  the  chloride  with  mercuric  cyanide,  forms  a  crystalline 
mass,  fusing  at  31°  C.  (87°  F.),  boiling  at  207°  C.  (404°  F.),  and  having  a 
pungent  odor,  somewhat  resembling  that  of  cinnamon.  All  these  com- 
pounds yield  benzamide  with  dry  ammonia. 

BENZOYL  OXIDE,  OR  ANHYDRIDE,  C,4H1003,  or  (C7H50)20,  is  obtained  by 
the  action  of  benzoyl  chloride  on  potassium  benzoate : 

C7H50(ONa)     -f     C7H6OC1    =    NaCl     +     (C7H50)20. 

Benzoyl  chloride  acts  in  like  manner  on  acetate  or  valerate  of  sodium,  form- 
ing aceto-benzoic  or  valero-benzoic  oxide,  either  of  which  splits  up  on  dis- 
tillation into  acetic  or  valeric  oxide  and  benzoic  oxide : 


C7H5OC1 

Benzyl 

chloride. 


C6HflO(ONa)      = 

Sodium 
valerate. 


NaCl 


59 

Valero-ben- 
zoic oxide. 


and 


f  C7H50  \  0 


Valero-ben- 
zoic oxide. 


(C7H50)20 

Benzoic 
oxide. 


(<W>)20 

Valeric 
oxide. 


Benzo-oenanthylic,  benzostearic,  ben/o-angelic,  benzo-cuminic  oxide,  and 
several  others,  have  been  obtained  by  similar  processes. 

Benzoic  oxide  crystallizes  in  oblique  rhombic  prisms,  melting  at  42°  C. 


636  MONATOMIC   ACIDS,  CnH2n_8O2. 

(107°  F.),  and  distilling  undecomposed  at  310°  C.  (590°  F.).  It  melts  in 
boiling  water,  remaining  fluid  for  a  long  time,  but  is  ultimately  converted 
into  benzoic  acid,  and  dissolves  :  caustic  alkalies  etfect  the  conversion  much 
more  rapidly.  With  ammonia  it  forms  ammonium  benzoate  and  benzamide  : 

(C7H.O)20     +     2NH3    =     C7H60(NH4)0     -f     NH2C7H50 
Benzoic  Ammonium  Benzamide. 

oxide.  benzoate. 

BENZOYL  DIOXIDE,  OR  PEROXIDE,  C14H1004,  or  (C7H502)2. —  Brodie  ob- 
tained this  compound  by  bringing  benzoyl  chloride  in  contact  with  bari- 
um dioxide  under  water;  the  product,  when  re-crystallized  from  ether, 
yields  large  shining  crystals  of  benzoyl  dioxide,  which  explode  when  heated. 
When  submitted  to  the  action  of  a  boiling  solution  of  potash,  this  substance 
evolves  oxygen,  and  forms  potassium  benzoate. 

BENZOYL  SULPHIDE,  (C7H50)2S,  obtained  by  distilling  the  chloride  with 
finely  powdered  lead  sulphide,  is  a  yellow  fetid  oil,  solidifying  at  a  low 
temperature  to  a  soft  crystalline  mass. 

DIBENZOYL,  C14H1004.  —  Cupric  benzoate  subjected  to  gradual  dry  distil- 
lation, gives  a  residue  containing  salicylic  and  benzoic  acids,  and  an  oily 
distillate  which  crystallizes  on  cooling,  and  consists  of  dibenzoyl.  This 
substance  possesses  the  odor  of  the  geranium,  melts  at  70°  C.  (158°  F.).  It 
was  discovered  by  Ettling,  and  subsequently  studied  by  Stenhouse.  By 
heating  with  potassium  hydrate,  it  is  instantly  converted  into  benzoic  acid, 
with  evolution  of  hydrogen. 

Acids  derived  from  Benzoic  Acid  by  substitution. 

CHLOROBENZOIC  ACID,  C7H5C102,  is  obtained  by  treating  benzoic  acid  with 
potassium  chlorate  and  hydrochloric  acid.  Acids  having  the  same  com- 
position are  produced  by  the  action  of  chlorine  upon  benzoic  acid  in  sun- 
light, and  also  by  distilling  sulphobenzoic  acid,  salicylic  acid,  or  hippuric 
acid,  with  phosphorus  pentachloride,  and  boiling  the  distillate  with  water. 
The  acids  obtained  by  these  several  methods,  however,  diifer  in  their  prop- 
erties. Chlorobenzoic  acid  treated  with  sodium  amalgam  and  water  is  con- 
verted into  benzoic  acid. 

BROMOBENZOIC  ACID,  C7H6Br02,  is  formed  by  the  action  of  bromine  on 
silver  benzoate : 

C7H502Ag        -f         Br2         =        AgBr         +         C7H5Br02. 
Bromine  docs  not  act  on  benzoic  acid  at  ordinary  temperatures. 

NITROBENZOIC  ACID,  CjH^NOgjOj,  is  obtained  by  boiling  benzoic  acid  for 
several  hours  with  fuming  nitric  acid;  and  by  prolonged  action  of  the  fum- 
ing nitric  acid,  or  more  readily  by  the  action  of  a  mixture  of  nitric  and 
sulphuric  acids,  dinitrobenzoic  acid,  C7H4(N02)202,  is  produced.  Both  these 
are  crystalline  bodies,  analogous  in  most  of  their  reactions  to  benzoic  acid. 

AMIDOBENZOIC  ACIDS. — Nitrobenzoic  and  dinitrobenzoic  acids  are  re- 
duced, by  treatment  with  certain  reducing  agents,  as  hydrogen  sulphide  or 
ammonium  sulphide,  to  amido-benzoic  and  diamido -benzoic  acids : 


C71T5(N02)02    -f  3SH2    =    20H2    +     S3    +     C7H5(NH2)02 

Nitrobenzoic  Amidobenzoic 

acid.  acid. 

C7H4(N02)202     -f  6SH2    =    40H2    +     S6     -f-     C7H4(NH2)202 

Dinitrobenzoic  Diamido- 

acid.  benzoic  acid. 


ACETAMIDOBENZOIC — HIPPURIC   ACIDS.  637 

Both  these  are  crystalline  compounds.  Amidobenzoic  acid  is  a  monobasic 
acid,  forming  metallic  salts  and  ethers ;  diamidobenzoic  acid,  on  the  con- 
trary, possesses  no  acid  properties,  but  is  rather  a  base,  combining  readily 
with  hydrochloric  and  other  acids,  and  forming  crystallizable  salts. 

When  amidobenzoic  acid,  C7H7N02,  is  subjected  to  the  action  of  nitrous 
acid,  two  molecules  of  it  give  up  three  atoms  of  hydrogen  in  exchange  for 
one  atom  of  nitrogen,  and  are  converted  into  a  compound  containing  CM 
HltN/>, 

2C7H7N02     +     N02H    =    20  H2    -j-     C14HUN304. 

This  substitution  of  hydrogen  for  nitrogen  was  first  observed  by  Griess, 
Avho  has  since  shown  that  it  is  susceptible  of  very  general  application. 

By  the  prolonged  action  of  nitrous  acid,  the  compound  C14HUN304  is 
partially  converted  into  oxybenzoic  acid,  C7H602. 

ACETAMTDOBENZOIC  ACID,*  CgHgNO,,  =  C7H5[NH(C2H30)]02,  or 
C7H4NH(CH30) 

. — This  acid  is  produced  by  digesting  amidobenzoic  acid 
COOH 
with  acetic  acid  at  130°-140°  C.  (266°-284°  F.)  in  a  sealed  tube: 

C7H5(NH2)02     +     C2H30(OH)     =    OH2     +     C7H5[NH(C2H30)]02, 
Amidobenzoic  Acetic  Acetamidobenzoic 

acid.  acid.  acid. 

or  by  the  action  of  acetyl  chloride  or  acetic  acid  on  zinc  amidobenzoate : 

(C7H6N02)2Zn"     -f     2C2H8OC1     ==     ZnCl2     -f     2C7H6(C2H30)N02 
Zinc  oxybenzoate.  Acetyl  Acetamidobenzoic 

chloride.  acid. 

Acetamidobenzoic  acid  is  a  white  powder,  consisting  of  microscopic  crys- 

»tals,  insoluble  in  cold  water  and  ether,  slightly  soluble  in  boiling  water, 
easily  in  boiling  alcohol.  It  is  a  monobasic  acid,  forming  easily  soluble 
salts  with  the  metals  of  the  alkalies  and  alkaline  earths ;  sparingly  soluble 
salts  with  lead,  silver,  and  zinc.  By  boiling  with  hydrochloric  or  dilute 
sulphuric  acid,  it  is  resolved  into  acetic  and  amidobenzoic  acids : 

C9H9N03    +     OH2    =    C2H402    +     C7H7N02. 

HIPPURIC  ACID,  OR  BENZAMIDACETIC  ACID,  CfirLNO.  =  C,H.(C7H-0)N02 

C2H2NH(C6H60) 

=  C2H3[NH(C7H50)]02  or     |  .  —  This   acid,    isomeric   with 

COOH 

acetamidobenzoic  acid,  is  produced  by  the  action  of  benzoyl  chloride  on 
the  zinc  salt  of  amidacetic  acid  (glycocine)  : 

(C2H4N02)2Zn"     +    2C7H5OC1    =    ZnCl2    +    2C2H3[NH(C7H50)]02; 

the  reaction  being  analogous  to  the  second  of  those  above  given  for  the 
formation  of  acetamidobenzoic  acid. 

Hippuric  acid  occurs,  often  in  large  quantity,  as  a  potassium  or  sodium- 
salt,  in  the  urine  of  horses,  cows,  and  other  graminivorous  animals ;  in 
smaller  quantity  also  in  human  urine.  It  is  prepared  by  evaporating  in  a 

Iivater-bath  perfectly  fresh  cows'  urine  to  about  a  tenth  of  its  volume,  filter- 
.ng  from  the  deposit,  and  then  mixing  the  liquid  with  excess  of  hydro- 
chloric acid.     Cows'  urine  frequently  deposits  hippuric  acid  without  con- 
centration, when  mixed  with  a  considerable  quantity  of  hydrochloric  acid, 
in  which  the  acid  is  less  soluble  than  in  water.     The  brown  crystalline 
*  G.  C.  Foster,  Chem.  Soc.  Journal,  xili.  235. 
" 


638  MONATOMIC    ACIDS,  CnH2n_8O2. 

mass,  which  separates  on  cooling,  is  dissolved  in  boiling  water,  and  treated 
with  a  stream  of  chlorine  gas,  until  the  liquid  assumes  a  light  amber  color, 
and  begins  to  smell  of  chlorine  :  it  is  then  filtered  and  left  to  cool.  The 
still  impure  acid  is  re-dissolved  in  water,  neutralized  with  sodium  carbonate, 
and  boiled  for  a  short  time  with  animal  charcoal:  the  hot  filtered  solution 
is,  lastly,  decomposed  by  hydrochloric  acid. 

Hippuric  acid  crystallizes  in  long,  slender,  milk-white,  and  exceedingly 
delicate  square  prisms,  which  have  a  slightly  bitter  taste,  melt  on  the  ap- 
plication of  heat,  and  require  for  solution  about -400  parts  of  cold  water: 
it  also  dissolves- in  hot  alcohol.  It  has  an  acid  reaction,  and  forms  salts 
with  bases,  many  of  which  are  crystallizable.  Exposed  to  a.  high  temper- 
ature, hippuric  acid  undergoes  decomposition,  yielding  benzoic  acid,  am- 
monium benzoate.  and  benzonitrile,  with  a  coaly  residue.  With  hot  oil  of 
vitriol,  it  gives  off  benzoic  acid ;  boiling  hydrochloric  acid  converts  it  into 
benzoic  acid  and  amidacetic  acid  or  glycocine : 

C2H4(C7H50)N02     +      H(OH)     =     C7H50(OH)     +     C2H6N02, 
Hippuric  acid.  Water.  Benzoic  Amidacetic 

acid.  acid. 

just  as  acetamidobenzoic  acid  is  resolved  into  acetic  and  amidobenzoic 
acids. 

Hippuric  acid,  treated  with  nitrous  acid,  gives  off  nitrogen,  and  is  con- 
verted into  benzoglycollic  acid,  an  acid  containing  the  elements  of  benzoic 
and  glycollic  (oxyacetic)  acids,  minus  one  molecule  of  water : 

C9H9N03      -f      N02H      =      C9H804      +      OH2      -f      N2 
Hippuric  Nitrous  Benzogly- 

acid.  acid.  collie  acid. 

Benzoglycollic  acid,  when  boiled  with  water,  splits  up  into  benzoic  and  gly- 
collic acids : 

C9H804  +  OH2  =    CTH602  +  C2H403. 

If,  in  the  preparation  of  hippuric  acid,  the  urine  be  in  the  slightest  de- 
gree putrid,  the  hippuric  acid  is  all  destroyed  during  the  evaporation,  am- 
monia is  disengaged  in  large  quantity,  and  the  liquid  is  then  found  to 
yield  nothing  but  benzoic  acid,  not  a  trace  of  which  can  be  discovered  in 
the  unaltered  secretion.  Complete  putrefaction  effects  the  same  change : 
benzoic  acid  might  thus  be  procured  to  almost  any  extent.  When  benzoic 
acid  is  taken  internally,  it  is  rejected  from  the  system  in  the  state  of  hip- 
puric acid,  which  is  then  found  in  the  urine. 

Hippuric  acid  is  monobasic,  the  formula  of  the  hippurates  of  monatomic 
metals  being  C9H8MN03.  Most  metallic  oxides  dissolve  readily  in  hippuric 
acid.  The  hippurates  of  potassium,  sodium,  and  ammonium,  are  very 
soluble,  and  difficult  to  crystallize ;  their  solutions  form  a  cream-colored 
precipitate  with  ferric  salts,  and  white  curdy  precipitates  with  silver  ni- 
trate and  mercurous  nitrate.  A  characteristic  reaction  of  the  hippurates 
is,  that,  when  fused  with  excess  of  potash  or  lime,  they  give  off  ammonia 
and  yield  benzene  by  distillation.  Mineral  acids  decompose  them,  separat- 
ing the  hippuric  acid. 

Hippuric  acid  dissolves  so  abundantly  in  an  aqueous  solution  of  sodium 
phosphate,  that  this  solution  loses  its  alkaline  reaction  and  becomes  acid. 
This  reaction  may  explain  the  acid  character  of  the  recent  urine  of  man 
and  animals. 

Toluic  Acid,  C8H802  =  C8HtO(OH).— This  formula  includes  two  isomeric 
acids,  viz. : 

Normal  toluic  acid,  C6H4(CH3) .  COOH,  corresponding  to  xylylic  alcohol, 
C6H4(CH3) .  CH2OH,  derived  from  dimethyl-benzene  (p.  497). 


XYLIC  —  CUMIC   ACIDS.  639 

Alpha-toluic  acid,  06H5 .  CII2COOH,  corresponding  to  the  unknown  alco- 
hol, C6H5.CH2CH2OH,  derived  from  ethyl-benzene. 

Normal  toluic  add  is  produced  —  1.  By  oxidation  of  xylene  with  dilute 
nitric  acid: 

C8HW  +  03  =  OH2  +  C8H802 

Also  by  the  prolonged  action  of  dilute  nitric  acid  on  cymene  (p.  500), 
oxalic  acid  being  formed  at  the  same  time : 

C10H14    +     08    =    C8H802     +     C2H204    +    20H2 
Cymene.  Toluic  Oxalic 

acid.  acid. 

2.  Synthetically,  by  the  action  of  sodium  and  carbon  dioxide  on  bromo- 
toluene : 

C7H7Br     -f     Na2    -f-     C02    =    NaBr    -f-     C7H7.C02Na 
Bromo-  Sodium 

toluene.  toluate. 

Toluic  acid  is  precipitated  by  acids  from  the  solution  of  its  salts  as  a 
white  crystalline  mass,  which  melts  at  about  175°  C.  (347°  F.),  and  sub- 
limes without  decomposition  in  fine  needles.  Its  chemical  reactions  are 
analogous  to  those  of  benzoic  acid.  By  distillation  with  lime  or  baryta  it 
is  resolved  into  carbon  dioxide  and  toluene,  C7H8.  Distilled  with  phos- 
phorus pentachloride,  it  yields  toluic  chloride,  C8H7OC1,  or  C6H4CH3 .  COC1. 
Strong  nitric  acid,  at  the  boiling  heat,  converts  it  into  nitrotoluic  acid, 
C8H7(N02)02.  When  introduced  into  the  animal  organism,  it  is  excreted 
as  toluric  acid,  C,0HnN03,  a  homologue  of  hippuric  acid. 

Alpha-toluic  acid,  C6H6.  CH2C02H,  is  produced  by  boiling  benzyl  cyanide 
with  strong  potash  solution  as  long  as  ammonia  is  given  oif : 

C6H6.CH2CN     +     20H2    =    NH3    +     C6H5  CH2COOH 
Benzyl-  Alpha-toluic 

cyanide.  acid. 

The  reaction  amounts  to  an  interchange  between  an  atom  of  trivalent 
nitrogen  and  the  group  0//(OH) :  hence  the  constitution  of  the  acid  is 
apparent. 

Alpha-toluic  acid  crystallizes  from  boiling  water  in  broad,  thin  laminae, 
very  much  like  benzoic  acid :  it  has  an  odor  like  that  of  the  perspiration 
of  horses.  It  melts  at  76-5°  C.  (169°  F.),  gives  oif,  even  below  100°,  vapors 
which  excite  coughing,  and  boils  at  265-5°  C.  (510°  F.).  It  forms  a  sub- 
stitution-product with  nitric  acid,  and  when  distilled  with  phosphorus 
pentachloride,  yields  alpha-toluic  chloride,  C8H7OC1,  or  C6H6.  CH2COC1,  which 
passes  over  as  a  colorless  heavy  liquid. 

Xylic  Acid,  C9H1002  =  C6H3(CH3)2.  C02H,  homologous  with  benzoic  and 
with  normal  toluic  acid,  is  produced  by  the  action  of  sodium  and  carbon 
dioxide  on  bromo-xylene,  C8H9Br;  also,  by  oxidizing  cumene,  C9H12,  with 
nitric  acid.  Insolinic  acid,  C9H804,  is  formed  at  the  same  time,  but  the  two 
acids  are  easily  separated  by  distillation,  the  xylic  acid  passing  over,  while 
the  insolinic  acid  remains  behind.  Xylic  acid  crystallizes  from  boiling 
water  in  needles,  melts  at  103°  C.  (217°  F.),  boils  at  273°  C.  (523°  F.),  and 
sublimes  easily  in  needles. 

Alpha-xylic  acid,  C6H4(CH3) .  CH2C02H,  is  obtained  by  boiling  xylyl  chlo- 
ride with  potassium  cyanide  (whereby  xylyl  cyanide,  C8H9C1,  is  produced), 
and  then  with  potash.  It  crystallizes  in  broad  needles,  having  a  satiny 
lustre,  easily  soluble  in  water,  and  boiling  at  42°  C.  (108°  F.). 

Cumic  Acid,  C10H1202,  probably  C6H4(C3H7) .  C02H,  homologous  with  ben- 


640  MONATOMIC    ACIDS,  C  H2n_10O2. 

zoic  and  normal  toluic  acids,  is  produced  by  oxidation  of  cuminol  or  cumic 
aldehyde,  C10H120,  one  of  the  constituents  of  oil  of  cumin.  It  is  very  much 
like  benzoic  acid,  is  converted  by  fuming  nitric  acid  into  nitrocumic  acid, 
Ci0Hu(NO)204,  and  resolved,  by  distillation  with  lime,  into  carbon  dioxide 
and  cumene,  C9H,2. 

Cymic  Acid,  CUHU02. — Normal  cymic  acid  is  not  known,  but  alphacymic 
acid,  probably  C6H3(C2H6)2COOH,  is  produced  by  the  action  of  caustic 
alkalies  on  cymyl  cyanide,  CJOH13CN. 


Monatomic  Acids,  CnH2n_1002. 

The  acids  of  this  series  are  related  to  the  aromatic  acids,  in  the  same 
manner  as  those  of  the  acrylic  series  to  the  fatty  acids.  Only  two  of  them, 
however,  are  at  present  known,  viz. :  cinnamic  and  atropic  acids,  both 
containing  CqHoO,. 

CH(C7H6)" 
CINNAMIC   ACID,  C9H802  =  C9H70(OH)  —    |  .  —  This   acid  is 

C02H 

produced  synthetically:  1.  By  heating  benzoic  aldehyde  in  close  vessels 
with  acetyl  chloride: 

C7H60     +     C2H3OC1    =     HC1     +     C9H802. 

2.  By  treating  potassium  benzoate  with  chlorethylidene  (produced  by 
the  action  of  carbonyl  chloride  on  acetic  aldehyde) : 

C2H40      -f      COC12      ==      HC1      +      C02      +        C2H3C1 
Aldehyde.          Carbonyl  Chlorethyl- 

chloride.  idene. 

C2H3C1        +        C7H502K        =        KC1        -f        C9H802 
Chlorethyl-  Potassium  Cinnamic 

idene.  benzoate.  acid. 

Cinnamic  acid  is  also  produced  by  oxidation  of  cinnamon-oil  (cinnamic 
aldehyde,  C9H80)  in  air  or  oxygen,  and  exists  ready  formed,  together  with 
benzoic  acid,  and  certain  oily  and  resinous  substances,  in  Peru  and  Tolu 
balsams,  being  doubtless  produced  by  oxidation  of  cinnyl  alcohol  or  styrone, 
C9H,00  (p.  554),  likewise  contained  therein.  It  ma'y  be  procured  by  the 
following  process  in  great  abundance,  and  in  a  state  of  perfect  purity.  Old, 
hard  Tolu  balsam  is  reduced  to  powder  and  intimately  mixed  with  an  equal 
weight  of  slaked  lime :  this  mixture  is  boiled  for  some  time  in  a  large  quan- 
tity of  water,  and  filtered  hot.  On  cooling,  calcium  cinnamate  crystallizes 
out,  while  calcium  benzoate  remains  in  solution.  The  impure  salt  is  redis- 
solved  in  boiling  water,  digested  with  animal  charcoal,  and,  after  filtration, 
suffered  to  crystallize.  The  crystals  are  drained  and  pressed,  once  more 
dissolved  in  hot.  water,  and  an  excess  of  hydrochloric  acid  being  added, 
the  whole  is  allowed  to  cool.  The  pure  cinnamic  acid  separates  in  small 
plates  or  needle-formed  crystals  of  perfect  whiteness.  From  the  original 
mother-liquor  much  benzoic  acid  may  be  procured. 

The  crystals  of  cinnamic  acid  are  smaller  and  less  distinct  than  those  of 
benzoic  acid,  which  in  most  respects  it  very  closely  resembles.  It  melts  at 
120°  C.  (248°  F.),  and  enters  into  ebullition  at  293°  C.  (560°  F.) ;  the  vapor 
is  pungent  and  irritating.  Cinnamic  acid  is  much  less  soluble,  both  in  hot 
and  cold  water,  than  benzoic  acid ;  a  hot  saturated  solution  becomes  on. 


DIATOMIC   ACIDS.  641 

cooling  a  soft  solid  mass  of  small  nacreous  crystals.  It  dissolves  with  perfect 
ease  in  alcohol.  Boiling  nitric  acid  decomposes  cinnamic  acid  with  great 
energy,  and  with  production  of  copious  red  fumes:  bitter  almond-oil  distils 
over,  and  benzoic  acid  remains  in  the  retort.  When  oinnamic  acid  is  heated 
in  a  retort  with  a  mixture  of  strong  solution  of  potassium  bichromate  and 
sulphuric  acid,  it  is  almost  instantly  converted  into  benzoic  acid,  which 
afterwards  distils  over  with  the  vapor  of  water;  the  odor  of  bitter-almond 
oil  is  at  the  same  time  very  perceptible.  Cinnamic  acid  fused  with  excess 
of  potassium  hydrate,  is  decomposed  into  benzoic  and  acetic  acids: 

C9H802     +     20H2    =     C7H602    -f     C2H402    +     H2. 

This  decomposition  is  precisely  analogous  to  that  of  an  acid  of  the  acrylic 
series  into  two  acids  of  the  fatty  series  (p.  626). 

Cinnamic  acid  is  resolved  by  distillation  with  lime  or  baryta,  and  par- 
tially also,  when  distilled  alone,  into  carbon  dioxide  and  cinnamene,  C8H8 
(p.  501). 

The  cinnamates,  C9H?02M  (for  monatomic  metals),  are  very  much  like  the 
benzoates.  Cinnyl  cinnamalc,  Cmnamcin,  or  Styracin,  C9H702 .  C9H9,  is  con- 
tained, together  with  cinnamene  and  styrol,  in  liquid  storax  (which  exudes 
from  Styrax  calamita,  a  shrub  growing  in  Greece  and  Syria) ;  also,  together 
with  styrol  and  other  substances,  in  Peru  and  Tolu  balsams,  the  produce 
of  certain  species  of  Myroxylum  growing  in  South  America.  It  is  obtained 
from  storax  by  distilling  the  balsam  to  expel  the  styrol,  then  boiling  it  with 
aqueous  sodium  carbonate  to  remove  free  cinnamic  acid,  and  kneading  the 
spongy  residue  between  the  fingers.  Styracin  then  runs  out  as  an  oily  liquid, 
and  may  be  obtained  in  tufts  of  beautiful  prisms  by  crystallization  from 
alcohol.  When  distilled  with  potash,  it  is  resolved  into  cinnyl  alcohol  and 
cinnamic  acid. 

ATROPIC  ACID,  C9II802,  is  a  crystalline  acid,  isomeric  with  cinnamic  acid, 
obtained,  together  witli  a  basic  compound,  tropme,  by  the  action  of  alkalies 
on  atropine,  an  alkaloid  existing  in  Atropa  Belladonna  and  Datura  Stram- 
monium : 

C17H23N03        ==         C9H802        +        C8H15NO 
Atropine.  Atropic  acid.  Tropine. 


DIATOMIC  ACIDS. 

These  acids  are  derived  from  diatomic  alcohols  by  substitution  either  of 
0  for  H2,  in  which  case  they  contain  three  atoms  of  oxygen  and  are  mono- 
basic, or  by  substitution  of  02  for  H4,  in  which  case  they  contain  four  atoms 
of  oxygen  and  are  bibasic. 

The  relation  between  the  saturated  hydrocarbons,  the  glycols,  and  the 
diatomic  acids,  is  shown  in  the  following  table: 

Diatomic  Acids. 


Hydrocarbons.  Glycols.  Monobasic.  Bibasic. 

CnH2n-f2  Cnll2n+202  CnH2n03  CnII2n_204 

CTT  r1  TT    n  PTTA          r<  w       n 

nn2n  '-'n*:*2n'-'2  ^-/n**2n — 2*-'3  '-''n"2n — 4^4 

CnH2n_2  CnII2n_202  CnII2a_408 

CnH2n_4  CnH2n_402  CBnta^O, 

&c.  &c. 

54* 


642          DIATOMIC   AND    MONOBASIC   ACIDS;  CuH2nO3. 

Diatomic  and  Monobasic  Acids. 
1.— Lactic  Series,  CnH2n03. 

The  acids  of  this  series  may  be  divided  into  two  groups,  distinguished 
as  normal  lactic  acids  and  isolactic  acids.     The  known  members  of  the  series 


Glycollic  or  Oxyacetic  acid,  C2H403. 

Lactic  or  Oxypropionic  acid,  C3H6O3. 

Oxybutyric  acid,  C4H803,  and  its  isomer,  Dimethoxalic  acid. 

Oxyvaleric  acid,  C5H1003,  and  its  isomer,  Ethomethoxalic  acid. 

Leucic  or  Oxycaproic  acid,  C6H1203,  and  isomer,  Diethoxalic  acid. 

Acids  homologous  with  dimethoxalic  acid,  and  containing  7,  9,  and  12 
atoms  of  carbon,  have  also  been  obtained. 

The  normal  lactic  acids  correspond  to  the  diatomic  alcohols  homologous 
with  ethenic  alcohol  (glycol) ;  thus  : 

Cn_i  H2n_2OH  C^H^OH 

CH2OH  COOH 

Diatomic  Normal  acid  of 

alcohol.  lactic  series. 

If  in  the  second  formula  we  make  n  successively  equal  to  1,  2,  3,  &c., 
we  get  the  series : 

OH  CH2OH  C2H4OH  C3HGOH 

COOH  COOH  COOH  COOH 

Carbonic      Glycollic  Lactic  Oxybutyric 

acid.  acid.  acid.  acid. 

Carbonic  acid  is,  however,  a  bibasic  acid,  for  reasons  which  will  be  ex- 
plained further  on,  and  will  be  considered  by  itself. 
The  normal  lactic  acids  are  produced : 

1.  From  the  glycols  by  slow  oxidation  in  contact  with  platinum  black,  or 
by  the  action  of  dilute  nitric  acid.     The  higher  glycols,  however,  are  partly 
split  up  by  oxidation,  part  of  their  carbon  as  well  as  hydrogen  being  oxi- 
dized, and  a  lower  acid  of  the  series  produced;  thus  amylene  glycol  yields 
Oxybutyric  instead  of  oxyvaleric  acid. 

2.  By  the  action  of  moist  silver  oxide  on  the  monochlorinated  or  mono- 
brominated  fatty  acids  (p.  708),  e.  g.: 

C3H5C102     +    AgHO     =    AgCl    +     C3H603 
Chloropro-  Lactic 

pionic  acid.  acid. 

By  the  action  of  nitrous  acid  on  the  amidated  derivatives  of  the  fatty 
acids : 

C2H5N02    -j-     N02H    =    C2H403    +     OH2    +     N2 
Amidacetic  acid  Glycollic 

(glycocine).  acid. 

C(CnH2n+1)2OH 
The  Isolactic  acids  are  represented  by  the  general  formula,  I 

COOH 

They  are  obtained  in  the  form  of  ethers  by  the  action  of  the  zinc-com- 
pound of  an  alcohol-radical,  CnH^+j,  on  a  neutral  ether  of  oxalic  acid  con- 
taining a  radical  of  the  same  series,  such  as  diethylic  oxalate.  The  reac- 


DIATOMIC    AND   MONOBASIC   ACIDS,  C  H2DO3.          643 

tion  consists  in  the  replacement  of  an  atom  of  oxygen  in  the  oxalic  ether 
by  two  equivalents  of  alcohol-radical,  and  the  simultaneous  replacement  of 
an  equivalent  of  ethyl,  methyl,  &c.,  in  the  oxalic  ether  by  an  equivalent* 
of  zinc,  whereby  an  ether  of  zinc-diethyloxalic  acid,  &c.,  is  produced,  which 
by  certain  obvious  transformations  may  be  converted  into  the  required 
acid ;  thus  : 

COOCH3  C(C2H5)2OZn' 

4-    SZn'CJL  =  Zn'(CH3)0     -f        | 

COOCH3  COOCH, 

Dimethylic  Zinc  Zinc  Methylic  zinco- 

oxalate.  methide.         methylate.  diethoxalate. 

C(C2H5)2OZn'  C(C2H5)2OH 

+  HOH       =       Zn'HO        + 

COOCH3  COOCH3 

Methylic  zinco-  Water.  Zinc  Methylic 

diethoxalate.  hydrate.  diethoxalate. 

The  methylic  diethoxalate  is  easily  decomposed  by  baryta-water,  yield- 
ing methyl  alcohol  and  barium  diethoxalate : 

C(C2H5)2OH  C(C2H5)2OH 

+  Ba'HO      =     CH8(OH)       +        | 

COOCH,  COOBa' 

Methylic  Barium 

diethoxalate.  diethoxalate. 

And  this  salt  decomposed  by  sulphuric  acid  yields  diethoxalic  acid, 
C(C2H5)2OH 

,  isomeric  with  leucic  acid. 
COOH 

In  the  first  stage  of  the  process  it  is  found  best  to  use  a  mixture  of  ethyl 
iodide  with  metallic  zinc,  which  produces  zinc-ethide,  instead  of  the  latter 
compound  previously  prepared.  The  other  isolactic  ethers  are  prepared 
in  a  similar  manner. 

The  acids  of  either  group  are  reduced  by  hydjiodic  acid  to  the  corre- 
sponding acids  of  the  acetic  series  ;  e.  g.  : 

C3Htf03      +      2HI      =      C3H602      -f-       OH2  -f       I2 
Lactic  Propionic 

acid.  acid. 

The  ethereal  salts  of  the  isolactic  acids  are  converted  by  phosphorus  tri- 
chloride or  pentoxide,  into  ethers  of  the  iso-acrylic  acids  (p.  625)  ;  the 
ethereal  salts  of  the  normal  lactic  acids  do  not  exhibit  this  reaction. 

The  normal  lactic  acids,  when  heated,  give  up  a  molecule  of  water,  and 
are  converted  into  oxygen  ethers  or  anhydrides  ;  e .  g. : 

C3H603        —        OH2        =        C3H402 
Lactic  Lactide. 

acid. 

Two  molecules  of  a  normal  lactic  acid  may  also  be  deprived  of  a  molecule 
of  water,  thereby  producing  a  condensed  acid,  analogous  to  the  polyethenic 
alcohols ;  e.  g. : 

2C3H603  OH2  CH61005 

Lactic  Dilactic 

acid.  acid. 

*  To  simplify  the  equations,  we  have  made  use  of  tho  equivalent  (32-5)  instead  of  the  atom 
(65)  of  zinc,  denoting  it  by  the  symbol  Zu'. 


644:          DIATOMIC    AND    MONOBASIC    ACIDS,  CnH2UO3. 


Glycollic  Acid,  C2H403    =      \  .  —  This  acid  is  produced  in  a  variety 

COOH 

of  reactions,  several  of  which  have  been  already  mentioned,  viz.,  the  oxi- 
dation of  glycol  by  contact  with  platinum  black  or  by  treatment  with  dilute 
nitric  acid;  the  decomposition  of  benzoglycollic  acid  by  boiling  with  water  ; 
the  decomposition  of  glycocine  by  nitrous  acid ;  the  action  of  water  or 
alkalies  on  bromacetic  and  chloracetic  acid,  or  their  salts  (pp.  603,  614, 
638),  e.g.,  by  boiling  silver  bromacetate  with  water: 

C2H2BrAg02        4-         OH2        =         AgBr         4-         C2H403 

It  is  also  produced :  a.  By  the  action  of  alkalies  on  glyoxal  and  glyoxylic 
acid  : 

C2H202        4-        OH2  =        C2H403 

Glyoxal.  Glycollic  acid. 

2C2H404        =        C2H204        4-        C2H403        4-        OH2. 
Glyoxylic  Oxalic  Glycollic 

acid.  acid.  acid. 

/?.  Together  with  glyoxal,  glyoxylic  acid,  and  other  products  by  the  ac- 
tion of  nitric  acid  upon  alcohol. 

y.  By  the  action  of  nascent  hydrogen  (evolved  by  zinc  and  sulphuric 
acid)  upon  oxalic  acid: 

C2H204        4-         2H2        =        OH2        4-        C2H403 
Oxalic  Glycollic 

acid.  acid. 

Glycollic  acid  differs  somewhat  in  its  properties,  according  to  the  man- 
ner in  which  it  is  prepared,  being  sometimes  syrupy  and  uncrystallizable, 
sometimes  separating  from  its  solution  in  ether  in  large  regular  crystals. 
It  has  a  very  sour  taste,  dissolves  easily  in  water,  alcohol,  and  ether ;  melts 
at  78°  or  79°  C.  (172°-174°  F.) ;  begins  to  boil  at  100°  ;  decomposes  when 
heated  to  above  150°  C.  (302°  F.).  All  the  glycollates  are  more  or  less  solu- 
ble and  crystallizable. 

Diglycollic  acid,  C4H605  —  2C2H403  —  OH2,  also  called  Paramalic  acid.  — 
This  acid,  isomeric  with  malic  acid,  and  related  to  glycollic  acid  in  the 
same  manner  as  diethenic  alcohol  to  glycol,  is  produced  by  the  dehydra- 
tion of  glycollic  acid,  and  by  the  oxidation  of  diethenic  or  triethenic  alco- 
hol. It  is  also  formed  in  the  preparation  of  glycollic  acid  by  heating 
sodium  chloracetate  with  caustic  soda,  which  in  fact  is  the  process  by  which 
it  was  first  obtained  : 

C2H3C102      4-      2NaHO      ==      NaCl      4-      OH2      +      C2H3Na03 

Chloracetic  Sodium  gly- 

acid.  collate. 

C2H3C102        4-        C2H3Na03        =         NaCl        4-         C4H606 

Chloracetic  Sodium  Diglycollic 

acid.  glycollate.  acid. 

Diglycollic  acid  is  a  crystalline  bibasic  acid,  forming  with  univalent 
metals,  normal  salts  containing  C4H5MX05,  and  acid  salts,  C4H4M205;  with 
bivalent  metals  it  forms  only  normal  salts,  C4H4M//05. 

C2H4OH  (HC2H,OH 

Lactic  Acid,  C3H603  —    I  or  C  \  0"          .—Of  this  acid  there  are 

COOH  ( OH 

two  modifications :  one  called  ordinary  lactic  acid,  produced  by  a  peculiar 
fermentation  of  sugar ;  the  second,  called  paralactic  or  sarcolactic  acid, 


•*• 

' 


LACTIC    ACID.  645 

existing  in  muscular  flesh.     The  difference  of  constitution  between  these 
two  acids  is  represented  by  the  following  formulae : 

CH3  CH2OH 

CHOH  CH2 

COOH  COOH 

Ordinary  lactic  acid.         Paralactic  acid. 

Ordinary  lactic  acid  is  also  produced  by  the  first  three  general  methods 
given  on  page  642,  viz.,  by  the  slow  oxidation  of  propene  glycol;  by  the 
action  of  moist  silver  oxide  on  chloro-propionic  or  bromo-propionic  acid ; 
and  by  the  action  of  nitrous  acid  on  alanine ;  further,  by  the  following 
special  processes: 

a.  By  the  action  of  nascent  hydrogen  on  pyruvic  acid : 

C3H403         -4-         H2        =         C3H603. 
0.  By  the  action  of  hydrocyanic  acid  and  water  on  acetic  aldehyde: 

CH2 
CH3  | 

4-  CNH        =        CHOH 

CO"H  I 

CN 

Aldehyde.          Hydrocyanic    Unknown  inter- 
acid,       mediate  compound. 
CH3  CH3 

CHOH        +        20H2        =        NHS        4-        CHOH 

CN  COOH 

Intermediate  Lactic  acid, 

compound. 

Paralactic  acid  is  produced: — 1.  By  heating  ethene  chlorohydrate  with 
an  alcoholic  solution  of  potassium  cyanide,  and  boiling  the  resulting 
ethene  cyano-hydrate  with  caustic  potash,  whereupon  ammonia  is  given 
off,  and  potassium  paralactate  is  produced  : 

CH2OH  CH2OH 

4-        CNK        =        KC1         4-          |    ' 
CH2C1  CH2CN 

Ethene  chlor-  Ethene  cyano- 

hydrate.  hydrate. 

CH2OH 
CH2OH 

4-        20H2        =        NH3        4-          CH2 
CH2CN  | 

Ethene  cyano-  COOH 

hydrate.  Paralactic 

acid. 

2.  By  combining  ethene  with  carbonyl  chloride,  whereby  paralactyl 
chloride  is  produced,  and  decomposing  this  chloride  with  an  alkali: 

CH2C1 
CH,  I 

4-  COCL  CH, 

CH,  I 

COC1 
Ethene.  Paralactyl  chloride. 


DIATOMIC   AND    MONOBASIC   ACIDS,  CnH2I1O3. 
CH2C1  CH2OH 

CH2        -f        2HOH  2HC1        +        CH2 

COC1  COOH 

Paralactyl  chloride.  Paralactic  acid. 

Paralactic  acid  is  extracted  from  muscular  flesh  by  cold  water  or  dilute 
alcohol. 

Preparation  of  ordinary  lactic  acid  by  Fermentation.  — Various  kinds  of  sugar, 
and  dextrin,  when  subjected  to  the  action  of  particular  ferments,  are  con- 
verted into  lactic  acid,  the  change  consisting  in  a  resolution  of  the  molecule, 
preceded  in  some  cases  by  the  assumption  of  the  elements  of  water: 

C6H1206  =  2C3H603 

Glucose.  Lactic  acid. 

C12H22On        -f        OH2        +        4C3H603 
Milk  sugar.  Lactic  acid. 

This  lactous  fermentation  requires  a  temperature  between  20°  and  40°  C. 
(58°  and  104°  F.),  and  the  presence  of  water  and  certain  ferments  —  viz., 
albuminous  substances  in  a  peculiar  state  of  decomposition,  such  as  casein, 
glutin,  or  animal  membranes,  especially  the  coating  of  the  stomach  of  the 
calf  (rennet),  or  of  the  dog,  or  bladder.  According  to  Pasteur  and  others, 
it  depends  upon  the  presence  of  a  peculiar  fungus,  Pcmcillium  glaucum  (p. 
521).  The  following  is  a  good  method  for  preparing  the  acid  in  consider- 
able quantity:  2  gallons  of  rnilk  are  mixed  with  6  pounds  of  raw  sugar,  12 
pints  of  water,  8  ounces  of  putrid  cheese,  and  4  pounds  of  chalk,  which 
should  be  mixed  up  to  a  creamy  consistence  with  some  of  the  liquid.  This 
mixture  is  exposed  in  a  loosely  covered  jar  to  a  temperature  of  about  80° 
C.  (86°  F.),  with  occasional  stirring.  The  use  of  the  chalk  is  to  neutralize 
the  lactic  acid,  which  would  otherwise  coagulate  the  casein,  render  it  insol- 
uble, and  thereby  put  a  stop  to  the  process.  At  the  end  of  two  or  three 
weeks  it  will  be  found  converted  into  a  semi-solid  mass  of  calcium  lactate, 
which  may  be  drained,  pressed,  and  purified  by  re-crystallization  from 
water.  The  lactate  may  be  decomposed  by  the  necessary  quantity  of  pure 
oxalic  acid,  the  filtered  liquor  neutralized  with  zinc  carbonate,  and,  after 
a  second  filtration,  evaporated  until  the  zinc-salt  crystallizes  out  on  cooling. 
An  important  modification  of  this  process  consists  in  employing  commercial 
zinc-white  instead  of  powdered  chalk,  which  yields  at  once  difficultly  soluble 
zinc  lactate,  easily  purified  by  re-crystallization.  The  zinc  lactate  may, 
lastly,  be  re-dissolved  in  water,  and  decomposed  by  sulphuretted  hydrogen, 
in  order  to  obtain  the  free  acid.  Together  with  the  lactic  acid  a  certain 
quantity  of  mannite  is  invariably  formed.  This  is  separated  by  agitating 
the  concentrated  aqueous  solution  with  ether,  in  which  lactic  acid  alone  is 
soluble. 

If,  in  the  first  part  of  the  process,  the  solid  calcium  lactate  be  not  re- 
moved at  the  proper  time  from  the  fermenting  liquid,  it  will  gradually 
re-dissolve  and  disappear,  being  converted  into  soluble  butyrate  (p.  617). 

Lactic  acid  may  be  extracted  from  a  great  variety  of  liquids  containing 
decomposing  organic  matter,  as  sauerkraut,  a  preparation  of  white  cabbage, 
the  sour  liquor  of  the  starch-maker,  &c. 

Solution  of  lactic  acid  may  be  concentrated  in  the  vacuum  of  the  air- 
pump,  over  a  surface  of  oil  of  vitriol,  until  it  appears  as  a  colorless,  syrupy 
liquid,  of  sp.  gr.  1-215.  It  has  an  intensely  sour  taste  and  acid  reaction: 
it  is  hygroscopic,  and  very  soluble  in  water,  alcohol,  and  ether.  All  its 
salts  are  soluble. 

When  syrupy  lactic  acid  is  heated  in  a  retort  to  130°  C.  (266°  F.),  water 


LACTIC   ACID.  617 

containing  a  little  lactic  acid  distils  over,  and  the  residue  on  cooling  forms 
a  yellowish,  solid,  fusible  mass,  very  bitter,  and  nearly  insoluble  in  water. 
This  is  dilactic  acid,  C6H,003— 2C3H603 — OH2.  Long-continued  boiling  with 
water  re-converts  it  into  lactic  acid.  When  this  substance  is  further  heated, 
it  decomposes,  yielding  numerous  products.  One  of  these  is  lacride,  or 
lactic  anhydride,  C3H4O2,  a  volatile  substance,  crystallizing  in  brilliant, 
colorless,  rhombic  plates,  which,  when  put  into  water,  slowly  dissolve,  with 
production  of  lactic  acid. 

Lactide  combines  with  ammonia,  forming  lactamide,  a  soluble  crystallizable 
substance  isomeric  with  alanine  or  amidopropionic  acid  (p.  G15).  The  dif- 
ference between  these  two  bodies  and  their  relation  to  lactic  acid  is  ex- 
hibited by  the  following  formulae : 

C2H4NH2  C2H4OH  C2H4OH 

COOH  COOH  CONH2 

Alanine.  Lactic  acid.  Lactamide. 

Alanine  may  be  derived  from  lactic  acid  by  substitution  of  amidogen  for 
the  alcoholic  hydroxyl  of  the  acid  (which  comes  to  exactly  the  same  thing 
as  replacing  an  atom  of  hydrogen  in  propionic  acid,  C3H602,  by  amidogen) ; 
accordingly  it  retains  an  atom  of  basic  hydrogen,  and  therefore  reacts  as 
an  acid  (lactamic  or  amidopropionic  acid) ;  but  in  lactamide  the  basic  hy- 
droxyl is  replaced  by  amidogen,  and  therefore  the  compound  is  neutral. 

Another  product  of  the  action  of  heat  on  lactic  acid  is  lactone,  a  colorless 
volatile  liquid,  boiling  at  92-2°  C.  (198°  F.).  Acetone  is  also  formed,  and 
carbon  monoxide  and  dioxide  are  given  off.  Lactic  acid,  boiled  with  dilute 
nitric  acid,  or  with  dioxide  of  lead  or  barium,  is  converted  into  oxalic  acid. 
Distilled  with  dilute  sulphuric  acid  and  dioxide  of  lead  or  manganese,  it 
yields  a  large  quantity  of  aldehyde,  together  with  carbon  dioxide.  Hy- 
driodic  acid,  or  a  mixture  of  phosphorus  tetroxide  and  water,  reduces  it 
to  propionic  acid,  with  liberation  of  iodine : 

C3H603    +     2HI     =     C3H602     +     OH2    +    I2. 

Paralactic  acid  in  solution  or  in  the  syrupy  state  is  undistinguishable  from 
ordinary  lactic  acid.  When  heated  it  is  converted  into  lactide,  which,  when 
boiled  with  water,  yields  ordinary  lactic  acid. 

.  Lactates.  —  The  best  denned  of  these  salts  are  represented  by  the  formulae, 
C-jIIjOgM',  and  (C3H503)2M//.  Barium  and  calcium  also  form  acid  lactates, 
e.  g.,  (C3H503)2Ca// .  2C3lf603.  The  lactates  are,  for  the  most  part,  sparingly 
soluble  in  cold  water,  and  effloresce  rapidly  from  their  solutions:  they  are 
all  insoluble  in  ether.  When  heated  with  excess  of  strong  sulphuric  acid, 
they  give  off  a  large  quantity  of  pure  carbon  monoxide, 

The  paralactates  have,  for  the  most  part,  the  same  composition  as  the 
lactates ;  but  some  of  them  differ  in  form,  solubility,  and  other  characters. 

Calcium  lactate,  (C3H508)8Ca"  .  5  Aq.,  is  obtained  in  the  fermentation  pro- 
cess above  described,  or  by  boiling  aqueous  lactic  acid  with  calcium  car- 
bonate. It  dissolves  in  9-5  parts  of  water  at  ordinary  temperatures.  The 
paralactate  contains  only  4  molecules  of  water,  which  however  it  retains 
longer  than  the  lactate,  and  requires  12  parts  of  water  to  dissolve  it.  — 
Zinc  lactate,  (C3H603)2Zn// .  3  Aq.,  gives  off  its  water  quickly  at  100°,  dis- 
solves in  6  parts  of  boiling  water,  in  5-8  parts  of  cold  water,  and  is  nearly 
insoluble  in  alcohol.  The  paralactate  contains  only  2  molecules  of  crystal- 
lization-water, which  it  retains  with  considerable  force.  It  dissolves  in 
2-88  parts  of  boiling,  5-7  parts  of  cold  water,  and  in  2-23  parts  of  alcohol, 
either  cold  or  boiling. — Ferrous  lactate  is  precipitated  in  small  yellowish 
needles  on  mixing  ammonium  lactate  with  ferrous  chloride  or  sulphate.  — 
Ferric  lactate  is  a  brown  deliquescent  mass. 


64:8  CARBONIC   ACID. 

Lactic  Ethers. — Lactic  acid,  like  the  other  members  of  the  group,  can 
form  three  different  ethers  containing  the  same  univalent  alcohol-radical, 
according  as  the  alcoholic  or  the  basic  hydrogen-atom,  or  both,  are  re- 
placed ;  thus : 

C2H4OH  C2H4OC2H5  C2H4OH  C2H4OC2H5 

COOH  COOH  COOC.Hg  COOC2H5 

Lactic  Ethyl-lactic  Monethylic     Diethylic  lactate, 

acid.  acid.  lactate.          or  ethylic  ethyl 

lactate. 

Monethylic  lactate,  C3H504 .  C2H5,  is  produced  by  distilling  potassium  or 
sodium  lactate  with  potassium  ethylsulphate.  It  is  a  syrupy  liquid,  boiling 
at  176°  C.  (348°  F.).  Potassium  dissolves  in  it,  with  evolution  of  hydrogen, 

C2H4OK 
forming  ethylic  potassio-lactate,    I  .  —  Ethyl-lactic  acid,  C3H4(C2H5)03.H, 

COC2H5 

is  obtained  as  a  potassium  or  calcium-salt  by  decomposing  diethylic  lactate 
with  potash  or  milk  of  lime.  When  separated  from  these  salts  by  sulphuric 
acid,  it  forms  a  viscid  liquid,  boiling  with  partial  decomposition  between 
195°  and  198°  C.  (383°-388°  F.).  Diethylic  lactate,  C3H4(C2H5)03 .  C2H5,  is 
produced  by  the  action  of  ethyl-iodide  on  ethylic  potassio-lactate,  or  on 
sodium  ethylate,  and  by  that  of  sodium  ethylate  on  ethyl-chloropropionate  : 

C3H4C10.C2H5      -f       C2H5ONa    ==    NaCl     +     C3H403.  (C2H5)2 
Ethyl-chloro-  Sodium  Diethylic 

propionate.  ethylate.  lactate. 

Methyllactic  acid,  C3H4(CH3)03(OH),  and  its  zinc  and  silver  salts  have  also 
been  obtained. 

The  alcoholic  hydrogen  of  lactic  acid  may  also  be  replaced  by  ncid  radi- 
cals, forming  such  compounds  as  acetolactic  acid,  C3H4(C2H30)02 .  OH. 

LACTYL  CHLOIMDE,  C3H4OC12,  OR  CHLOROPROPIONYL  CHLORIDE,  C3H4C10 . 
Cl,  is  obtained,  together  with  phosphorus  oxychloride,  by  gently  heating  a 
mixture  of  calcium  lactate  with  phosphorus  pentachloride  ;  also  by  the 
direct  combination  of  ethene  with  carbonyl  chloride.  It  is  a  colorless 
liquid,  boiling  above  100°,  and  decomposed  with  water,  forming  hydro- 
chloric and  chloropropionic  acids. 

C6H10OH 
Leucic  Acid,  C6H1203  =    |  .  —  This  acid,  isomeric  with  diethoxalic 

COOH 

acid,  is  produced  by  the  action  of  nitrous  acid  on  leucine  or  amidocaproic 
acid  (p.  619).  It  forms  needles  or  monoclinic  prisms,  soluble  in  water,  al- 
cohol, and  ether,  melting  at  about  73°  C.  (163°  F.),  and  volatilizing  at  100°. 
When  heated  for  some  time  at  that  temperature,  it  gives  off  water,  and 
leaves  a  syrupy  oxide  or  anhydride.  It  forms  crystallizable  salts  analogous 
to  the  lactates. 


(OH 
Carbonic  Acid,  CH203  =  C  \  0".  —  This  acid  belongs  to  the  lactic  series, 

(OH 
so  far  as  its  constitution  is  concerned,  being  derived  from  the  unknown 

roil 
methane  glycol,  C  -I  H2  ,  by  substitution  of  0  for  H, ;  but  it  differs  from  all 

(OH 


CARBONIC    ETHERS.  649 

the  other  acids  of  the  series  in  being  bibasic,  both  the  hydroxyl  groups 
contained  in  it  being  immediately  connected  with  an  atom  of  oxygen,  so 
that  either  of  the  hydrogen-atoms  may  be  regarded  as  belonging  to  the 
group  C02H. 

Carbonic  acid  itself,  or  hydrogen  carbonate,  is  not  known,  inasmuch  as 
when  a  metallic  carbonate  is  decomposed  by  a  stronger  acid,  the  hydrogen 
carbonate,  CH,,03,  always  splits  up  into  water  and  carbon  dioxide,  which 
escapes  as  gas.  The  corresponding  sulphur-compound,  CII2S3,  is,  how- 
ever, obtained  as  an  oily  liquid  when  a  metallic  sulpho-carbonate  is  decom- 
posed by  an  acid  (p.  203). 

With  the  alkali-metals  carbonic  acid  forms  acid  and  normal  or  neutral 
salts,  according  as  one  or  both  of  the  hydrogen-atoms  are  replaced  ;  e.  g.  : 

(  OH 
Acid  sodium  carbonate, 


Normal  sodium  carbonate,      CNa203,    or  CO(ONa)2. 

With  the  earth-metals  and  other  dyad  metals,  carbonic  acid  forms  only 
normal  salts,  CM/X03,  and  basic  salts  ;  the  so-called  acid  carbonates  of 
barium,  calcium,  &c.,  are  known  only  in  solution,  and  are,  in  fact,  merely 
solutions  of  neutral  carbonates  in  aqueous  carbonic  acid,  which  give  off 
carbon  dioxide  on  boiling.  The  basic  carbonates  of  dyad  metals  may  be 
viewed  as  compounds  of  normal  carbonates  with  metallic  oxides  or  hydrates; 
for  example,  slaked  lime,  produced  by  exposing  quicklin.e  to  moist  air,  has 
the  composition  of  a  dicalcic  carbonate,  Ca"0  .  C03Ca//  .  Aq.  ;  and  native 
green  copper  carbonate,  or  malachite,  consists  of  Cu/X0  .  CO-jCu"  .  Aq. 
These  basic  carbonates  may,  however,  be  viewed  in  another  way,  namely, 
as  derived  from  a  tetratomic  carbonic  acid,  or  orthocarbonic  add,  CH4,04,  or 
C(OH)4,  analogous  to  methane  and  carbon  tetrachloride  ;  thus,  dicalcic  car- 
bonate =  CCa"?04  .  Aq.  ;  malachite  =  CCu"204  .  Aq. 

With  metals  of  higher  atomicity,  carbonic  acid  does  not  form  definite  salts. 

CARBONIC  ETHERS.  —  The  only  carbonic  ethers  known  are  those  in  which 
the  two  hydrogen-atoms  of  carbonic  acid  are  replaced  either  by  two  equiv- 
alents of  a  monad  alcohol-radical,  or  by  one  equivalent  of  a  monad  alco- 
hol-radical and  one  equivalent  of  a  metal. 

Ethyl  carbonate,  C03(C2H5)2,  is  formed  by  the  action  of  ethyl  iodide  on 
silver  carbonate  : 

C03Ag2      +      2C,H6I      =      2AgI      +       C03(C2H5)2; 

also  by  the  action  of  potassium  or  sodium  on  ethyl  oxalate,  C204(C2H6)2  : 
this  reaction  is  not  quite  understood  ;  but  it  amounts  to  the  removal  of  car- 
bon monoxide,  or  carbonyl,  CO,  from  the  oxalic  ether.  Fragments  of  po- 
tassium or  sodium  are  dropped  into  oxalic  ether  as  long  as  gas  is  disen- 
gaged: the  brown  pasty  product  is  then  mixed  with  water  and  distilled. 
The  carbonic  ether  is  found  floating  upon  the  surface  of  the  water  of  the 
receiver  as  a  colorless,  limpid  liquid  of  aromatic  odor  and  burning  taste. 
It  boils  at  125°  C.  (1^57°  F.),  and  is  decomposed  by  an  alcoholic  solution  of 
potash  into  potassium  carbonate  and  alcohol.  By  chlorine  in  diffused  day- 
light it  is  converted  into  tetrachlorethyl  carbonate,  C03.  (C2H3C12)9,  and  in 
sunshine  into  pentachlorethyl  carbonate,  C03(C2Cl5)a. 

Ethyl-potassium  carbonate,  C03(C2H6)K,  is  produced  by  passing  carbonic 
acid  gas  into  a  cooled  solution  of  potassium  hydrate  in  absolute  alcohol  : 

C2H60     -f     KHO     -f     C02    =r     OHa    -f     C03.(C2H6)K. 

It  is  a  white  nacreous  salt,  decomposed  by  water  into  potassium  carbonate 
and  alcohol. 
55 


650  SULPHO-CAEBONIC    ETHERS. 

Ethyl-methyl  carbonate,  C03(C2H5)(CH3),  is  obtained  by  distilling  a  mixture 
of  ethyl-potassium  sulphate  and  methyl-potassium  carbonate  : 

S04.(C2H5)K    +    C03.(CH3)K    ==    S04K2    +    C03(C2H5)(CH3). 

Methyl-barium  carbonate,  (C03)2(CH3)2Ba//,  is  obtained  as  a  white  pre- 
cipitate by  passing  carbonic  acid  gas  into  a  solution  of  baryta  in  methyl 
alcohol. 

Carbonates  of  butyl,  amyl,  and  allyl,  analogous  in  composition  to  ethyl 
carbonate,  have  also  been  obtained.  Phenyl  hydrogen  carbonate,  or  acid 
phenyl  carbonate,  C03(C6H5)H,  is  identical  with  salicylic  acid,  which  will  be 
described  further  on. 

Ethyl  orthocarbonate,*  C(OC2H5)4,  is  produced  by  heating  a  mixture  of 
chloropicrin  (trichloro-nitromethane)  with  absolute  alcohol  and  sodium  : 


C(N02)C13    -f    4C2H5NaO    =    SNaCl    -f    N02Na    +    C(OC2H5)4 
Chloropicrin.  Sodium  Sodium          Sodium        Ethyl  ortho- 

ethylate.  chloride.          nitrile.          carbonate. 

It  is  a  colorless  oil,  boiling  at  158°-159°  C.  (313°-318°F.).  Heated  with 
boric  oxide  to  100°,  it  is  resolved  into  ethyl  anhydroborate  (p.  528),  and 
ordinary  ethyl  carbonate  : 

C(OC2H5)4    +     2B203    =    2B02C2H5.B203    +     C03(C2H5)2. 

SULPHOCARBONIC  ETHERS.  —  These  are  bodies  having  the  composition  of 
carbonic  ethers  in  which  the  oxygen  is  replaced,  wholly  or  partly,  by  sul- 
phur. The  following  table  exhibits  their  names  and  formulae,  the  ethyl 
and  ethene  compounds  being  taken  as  examples  : 

Ethyl-monosulphocarbonic  acid     .         .  C02S  .  (C2H5)H. 


Diet-hylic  monosulphocarbonate     . 
Ethyl-disulphocarbonic  or  Xanthic  acid 
Diethylic  disulphocarbonate 
Ethyl-trisulphocarbonic  acid 
Diethylic  trisulphocarbonate 
Ethene  disulphocarbonate 
Ethene  trisulphocarbonate    . 


C02S  .  (C2H5)2. 
COS2  .  (C2H6)H. 
COS2  .  (C2Hg)2. 
CS3  .  (C2H5)H. 
CS3  .  (C2H5)2. 
COS2  .  (C2H4)". 
CS3  .  (C,H4)". 


The  metallic  salts  of  the  acid  sulphocarbonic  ethers  are  produced  in  the 
same  manner  as  those  of  the  carbonic  ethers :  thus  carbonic  dioxide  unites 
with  potassium  sulphethylate  (mercaptide),  to  form  potassium  ethyl-mono- 
sulphocarbonate,  just  as  it  unites  with  potassiiim  ethylate  to  form  the  ethyl- 
carbonate  ;  and,  in  like  manner,  carbon  disulphide  acts  on  potassium 
ethylate  or  alcoholic  potash,  so  as  to  form  potassium  ethyldisulphocarbon- 
ate  ;  and  on  potassium  mercaptide,  or  an  alcoholic  solution  of  the  sulph- 
hydrate,  so  as  to  form  the  ethyltrisulphocarbonate,  thus: 

C02  -f  (C2H5)KO  =  C03(C2H5)K  Ethylcarbonate. 

C02  -(-   (C2H5)KS  =  C02S(C2H5)K  Ethylmonosulphocarbonate. 

CS2  +  (C2H5)6KO  =  COS2(C2H6)K  Ethyldisulphocarbonate. 

CS2  +   (C2H5)KS   ==  CS3(C2H5)K  Ethyltrisulphocarbonate. 

The  neutral  sulphocarbonic  ethers  (containing  monatomic  alcohol-radicals) 
are  produced  by  the  action  of  the  chlorides,  bromides,  &c.  of  alcohol-radi- 
cals on  the  metallic  salts  of  the  corresponding  acid  ethers,  e.  g. : 

(C2H8)KCS,    +     C2H6C1     =     KC1     -f     (C,H5),CS, 
Potassic  ethyl-  Ethylic  trisul- 

trisulphocarbonate.  phocarbonate. 

*  H.  J3assett,  Chem.  Soc.  Journal  [2],  i.  198. 


DIATOMIC    AND    MONOBASIC    ACIDS.  651 

The  sulphocarbonic  ethers  of  diatomic  alcohol-radicals  are  formed  by  the 
action  of  diatomic  alcoholic  bromides,  iodides,  &c.,  on  sodium  sulphocar- 


bonate,  e. 


C2H4Br2    +     CS3Na2    =    2NaBr     +     CS3(C2H4)" 
Ethene 


Ethene  tri- 
bromide.  sulphocarbonate. 

The  neutral  sulphocarbonic  ethers  are  oily  liquids ;  so  likewise  are  the 
acid  ethers,  such  at  least  as  are  known  in  the  free  state,  or  as  hydrogen- 
salts;  their  metallic  salts  are  mostly  crystalline.  The  best  known  of  these 
compounds  are  the  ethyldisulphocarbonales  or  xanthates. 

To  prepare  xanthic  acid,  alcohol  of  0-800  sp.  gr.  is  saturated,  whilst  boil- 
ing, with  potash,  and  into  this  solution  carbon  bisulphide  is  dropped  till  it 
ceases  to  be  dissolved,  or  until  the  liquid  loses  its  alkalinity.  On  cooling 
the  whole  to  —18°  C.  (0°  F.),  the  potassium-salt  separates  in  the  form  of 
brilliant,  slender,  colorless  prisms,  which  must  be  quickly  pressed  between 
folds  of  bibulous  paper,  and  dried  in  a  vacuum.  It  is  freely  soluble  in 
water  and  alcohol,  but  insoluble  in  ether,  and  is  gradually  destroyed  by 
exposure  to  air,  by  oxidation  of  part  of  the  sulphur.  Xanthic  acid  may  be 
prepared  by  decomposing  this  salt  with  dilute  sulphuric  or  hydrochloric 
acid.  It  is  a  colorless,  oily  liquid,  heavier  than  water,  of  powerful  and 
peculiar  odor,  and  very  combustible :  it  reddens  litmus-paper,  and  ulti- 
mately bleaches  it.  Exposed  to  gentle  heat  (about  24°  C.  [75°  F.]),  it  is 
decomposed  into  alcohol  and  carbon  bisulphide.  Exposed  to  the  air,  or 
kept  beneath  the  surface  of  water  open  to  the  air,  it  becomes  covered  with 
a  whitish  crust,  and  is  gradually  destroyed.  The  xanthates  of  the  alkali- 
metals  and  of  barium  are  colorless  and  crystallizable ;  the  calcium-salt 
dries  up  to  a  gummy  mass ;  the  xanthates  of  zinc,  lead,  and  mercury  are 
white,  and  but  slightly  soluble ;  that  of  copper  is  a  flocculent,  insoluble 
substance,  of  beautiful  yellow  color. 

Ethylic  duulphocarbonate  or  Xanthic  ether,  COS2 .  (C2H5)2,  obtained  by  the 
action  of  ethyl  chloride  on  potassium  xanthate,  is  a  pale-yellow  oil,  boiling 
at  200°  C.  (392°  F.),  insoluble  in  water,  soluble  in  all  proportions  of  alcohol 
or  ether.  Ammonia- gas  passed  into  its  alcoholic  solution  forms  mercaptan 
and  a  crystalline  substance  called  xanthamide : 

COS2(C2H5)2    +     NH,    =     CSH5(SH)     +    COS(C2H5)NH2 
Xanthic  ether.  Mercaptan.  Xanthamide. 

Amyl-disulphocarbonate,  COS(C5HU)2,  treated  in  like  manner,  yields  xan- 
thamylamide,  COS(C6H11)NH2. 


2. — Pyruvic  Series,  CnH2n-203. 
This  is  a  small  group  of  acids,  including  — 

Pyruvic  acid,  C3H403  I  Jalapinoleic  acid,  C^H^Og? 

Convolvulinoleic  acid,  C13H2403?  |  Ricinoleic  acid,  C18H34O3. 

Glyoxylic  acid,  a  product  of  the  oxidation  of  alcohol,  glycol,  and  glyoxal, 
is  sometimes  said  to  have  the  composition  C2H2O3 ;  but  it  is  more  probably 
C2H404,  arid  belongs  to  another  series,  as  will  be  explained  hereafter. 

Pyruvic  Acid,  C3H403,  also  called  Pyroracemic  acid,  is  produced  by  dry 
distillation  of  racemic  or  tartaric  acid : 

C4II606    =     C3H403     +     C02     -f     OH2. 


652         DIATOMIC    AND   MONOBASIC   ACIDS,  CnH2n_gO4. 

It  is  a  liquid,  boiling,  with  partial  decomposition,  at  about  165°  C.  (329°  F.). 
Treated  with  sodium  amalgam,  or  hydriodic  acid,  it  takes  up  two  atoms  of 
hydrogen,  and  is  converted  into  lactic  acid,  C3H603,  or  if  the  reagent  is 
used  in  large  excess,  into  propionic  acid,  C3H6O2.  It  also  unites  directly 
with  bromine,  forming  the  acid,  C3H4Br203,  probably  dibromolactic  acid. 
Its  salts  crystallize  readily. 

Convolvulinoleic  £cid  and  Jalapinoleic  Acid,  are  produced  by  the  action 
of  acids  or  alkalies  from  certain  resinous  glucosides  contained  in  the  root 
of  tuberose  or  officinal  jalap  (Convolvulus  Schiedanus],  and  of  Convolvulus 
(or  Ipomsea)  orizabensis,  the  jalap-stalks  or  jalap-wood  of  commerce;  but 
their  formulae  have  not  been  exactly  determined. 

Eicinoleic  Acid,  C18H3403,  is  a  yellow  oily  acid,  produced  by  the  saponifi- 
cation  of  castor-oil.  At  temperatures  between  — 6°  and  — 7°  C°  (19°-21°  F.), 
it  solidifies  to  a  granular  mass.  The  neutral  ricinoleates  of  the  alkali-metals 
when  distilled  alone  yield  a  distillate  of  osrianthol;  but  when  distilled  with 
excess  of  caustic  alkali,  they  give  off  hydrogen,  and  yield  a  distillate  of 
octyl  alcohol,  C8H180,  and  a  residue  of  alkaline  sebate,  C10H,6K204  (?•  541). 


3.— Series  CnH2n_403. 

The  only  known  acid  of  this  series  is  guaiacic  acid,  C6H803,  which  is  a 
crystallizable  substance  contained  in  guaiacum,  a  resin  obtained  from  Guai- 
acum  offitinale,  a  tree  growing  in  Jamaica.  It  sublimes  in  needles  resem- 
bling benzoic  acid,  and  is  resolved  by  dry  distillation  into  carbon  dioxide 
and  guaiacene,  C6H80. 


4.— Series  CnH2n_803. 

This  series  includes  the  following  acids,  related  to  the  aromatic  acids  in 
the  same  manner  as  the  lactic  acids  are  related  to  the  fatty  acids : 

Oxybenzoic,  Para-oxybenzoic,  and  Salicylic  acids    .         .  C7H603 

Formobenzoic,  Creosotic,  Carbocresylic,  and  Anisic  acids  C8H803 

Phloretic  acid C9H1003 

Thymotic  and  Thymyl-carbonic  acids       ....  CnHuO3 

Oxybenzoic  Acid,  C7H603,  or  C6H4(OH).  C02H,  is  produced  by  the  action 
of  nitrous  acid  on  amidobenzoic  acid : 

C6H4(NH2) .  C02H    -f    NO(OH)  =  C6H4(OH) .  C02H  +  OH2  +  X2. 
Amidobenzoic  acid.  Oxy-benzoic  acid. 

Oxybenzoic  acid  is  only  slightly  soluble  in  cold  water  or  alcohol,  but  dis- 
solves easily  in  either  of  these  liquids  at  the  boiling  heat,  and  separates 
as  a  crystalline  powder  on  cooling.  At  higher  temperatures  it  melts  and 
sublimes  without  decomposition,  a  character  by  which  it  is  distinguished 
from  its  two  isomers.  With  strong  nitric  acid  it  forms  nitro-oxybenzoic 
acid,  C7H5(N02)03,  which  is  converted  by  ammonium  sulphide  into  amid- 
oxybenzoic  acid,  C7H6(NH2)03. 

Para-oxybenzoic  Acid  is  produced  by  heating  anisic  acid  to  125°-130° 
with  strong  hydriodic  acid: 

C8H8°3         +         HI         =         CH3I         +         C7H603. 


SALICYLIC   ACID.  653 

It  is  more  soluble  in  cold  water  than  oxybenzoic  acid,  dissolving  in  126 
parts  of  water  at  15°:  from  a  hot  solution  it  crystallizes  in  small  distinct 
monoclinic  prisms.  It  melts  with  partial  decomposition  at  210°  C. 
(410°  F.),  and  is  easily  resolved  at  higher  temperatures  into  carbon  di- 
oxide and  phenol: 

C7H60S        =         C02         -f         C6H60. 

Its  solution  forms,  with  ferric  chloride,  a  yellow  precipitate  insoluble  in 
excess,  without  violent  coloration.  These  characters  distinguish  it  from 
oxybenzoic  acid.  With  most  metals  it  reacts  like  a  monobasic  acid,  its 
potassium-salt  containing  C7H503K,  and  its  cadmium-salt  (C7H603)2Cd/'/; 
but  it  appears  also,  like  salicylic  acid,  to  form  a  barium-salt  containing 
C7H4Ba"03. 

Salicylic  Acid  is  produced:  1.  By  passing  carbon  dioxide  into  phenol 
containing  small  pieces  of  sodium : 

NaOC6H5        -f        C02        = 
Sodium  phenate.  Sodium  salicylate. 

2.  From  salicylol,  C7H602,  by  oxidation  with,  aqueous  chromic  acid,  or  by 
melting  salicylol  or  salicin  with  potassium  hydrate,  in  which  case  hydro- 
gen is  evolved : 

C7H602        -f        KOH        =        C7H503K        -f        H2. 
Salicylol.  Potassium 

salicylate. 

3.  Coumaric  acid,  heated  with  potassium  hydrate,  yields  potassium  sali- 
cylate and  acetate  : 

C9H803     +     2KOH     ==    C7H503K    +     C2H302K    +     H2. 

4.  Oil  of  wintergreen  (Gaultheria procumbens],  which  consists  of  methyl- 
salicylic  acid,  is  resolved,  by  distillation  with  potash,  into  methyl  alcohol 
and  salicylic  acid : 

C7H5(CH3)03    +     KOH    =    CH3(OH)     -f     C7H6K03. 

Salicylic  acid  crystallizes  from  its  alcoholic  solution  by  spontaneous  eva- 
.  poration  in  large  monoclinic  prisms.  It  requires  about  1000  parts  of  cold 
water  to  dissolve  it,  but  is  much  more  soluble  in  hot  water  and  in  alcohol. 
Its  aqueous  solution  imparts  a  deep  violet  color  to  ferric  salts.  It  melts  at 
130°  C.  ('206°  F.j,  gives  off  phenol  at  a  higher  temperature,  and  when 
heated  with  pounded  glass  or  quicklime,  is  completely  resolved  into  carbon 
dioxide  and  phenol.  It  is  distinguished  from  both  its  isomers  by  its  beha- 
vior with  ferric  salts,  its  very  slight  solubility  in  water,  and  its  lower 
melting  point :  it  differs  from  oxybenzoic  acid  by  its  behavior  when 
heated. 

In  its  relations  to  metals,  salicylic  acid  appears  to  be  intermediate  be- 
tween monobasic  and  bibasic  acids.  With  the  alkali-metals  and  silver,  it 
forms  only  acid  salts  like  C7H6K03;  but  with  dyad  metals  it  forms  both 
acid  and  neutral  salts  ;  with  calcium,  for  example,  the  two  salts,  C7H4Ca"03 
and  Ci4H,0Ca"06,  or  (C7H503)2Ca".  The  neutral  salts  are,  however,  much 
less  easily  formed  than  the  acid  salts,  being  produced  only  in  presence  of 
a  large  excess  of  base.  Its  formation  from  carbon  dioxide  and  phenol 
seems  to  show  that  it  may  be  regarded  as  acid  phenyl  carbonate,  (C0)7/ 
(006ir5)(OH) ;  and  in  the  neutral  salicylates  of  bivalent  metals,  such  as 
C7H4Ca//03,  the  metal  appears  to  replace  one  atom  of  hydrogen  from  the 
group  OH,  and  another  from  the  group  OC6H6.* 

*  Piria,  Ann.  Ch.  Pharm.  xciii.  262. 

65* 


654        DIATOMIC    AND    MONOBASIC   ACIDS,  CnH2n_gO3. 

Salicylic  acid  forms  both  acid  and  neutral  ethers.  Oil  of  wintergreen, 
as  already  observed,  consists  of  methyl-salicylic  acid,  C7H6(CH3)O3.  A 
similar  compound,  containing  ethyl,  is  obtained  by  distilling  crystallized 
salicylic  acid  with  alcohol  and  sulphuric  acid  These  compounds  are  mono- 
basic acids,  the  basic  hydrogen  of  which  may  be  replaced  by  metals  or  by 
alcoholic-radicals,  forming  neutral  salicylic  ethers,  such  as  C7H4(CH3)203, 
C7H4(CH3)(C2H6)03,  &c.  There  is  also  an  ethene-salicylic  acid,  C14H,0 
(C2H4)X/06,  consisting  of  a  double  molecule  of  salicylic  acid  with  two  hy- 
drogen-atoms replaced  by  ethene  ;  it  is  produced  by  heating  ethene-bromide 
with  silver  salicylate. 

Carbocresylic  and  Cresotic  Acids,*  C8H803.  —  The  sodium-salts  of  these 
acids  are  formed  simultaneously  by  the  action  of  carbon  dioxide  and  sodi- 
um on  cresol,  C7H60.  On  treating  the  product  with  hydrochloric  acid,  the 
carbocresylic  acid  is  resolved  into  carbonic  dioxide  and  cresol,  while  the  cre- 
sotic acid  remains  undecomposed,  and  may  be  washed  out  with  ammonium 
carbonate ;  the  solution,  on  evaporation,  yielding  the  cresotic  acid  in  fine 
large  prisms  which  melt  at  153°  C.  (307°  F.),  are  slightly  soluble  in  water, 
easily  in  alcohol  and  ether.  It  forms  a  deep  violet  color  with  ferric  chlo- 
ride. When  heated  with  causic  baryta,  it  is  resolved  into  carbon  dioxide 
and  cresol.  With  regard  to  their  comparative  facility  of  decomposition, 
carbocresylic  and  cresotic  acids  appear  to  be  related  to  one  another,  in  the 
same  manner  as  salicylic  and  oxybenzoic  acids. 

Formobenzoic  Acid,  C8H803,  is  produced  by  evaporating  crude  bitter- 
almond  oil  to  dryness  with  hydrochloric  acid,  and  exhausting  the  residue 
with  ether,  which  leaves  sal-ammoniac  undissolved.  It  contains  the  ele- 
ments of  benzoic  acid,  C7H602,  and  formic  acid,  CH202,  minus  an  atom  of 
oxygen;  and  its  formation  appears  to  be  due  to  the  action  of  the  hydro- 
chloric acid  on  the  hydrocyanic  acid  of  the  crude  bitter-almond  oil,  where- 
by that  acid  is  resolved  into  ammonia  and  formic  acid.  Formobenzoic  acid 
forms  white  crystals  soluble  in  water.  It  is  resolved  by  oxidizing  agents 
into  bitter-almond  oil  (C7HnO),  and  carbon  dioxide. 

Anisic  Acid,  C8H803,  or  Methyl-paraoxybenzoic  acid.  C7H6(CH3)03. —  This 
acid  is  produced  by  oxidation  of  anisic  aldehyde,  C8H8O2,  in  contact  with 
platinum  black,  or  by  treatment  with  dilute  nitric  acid  (strong  nitric  acid 
would  convert  it  into  nitranisic  acid) ;  also  by  dropping  anisic  aldehyde 
into  fused  potash : 

C8H802        -f        KOH        =        C8H7K03        -f        H2. 

It  is  usually  prepared  by  oxidizing  anise-camphor,  C,0H120,  or  the  crude 
oils  of  anise,  fennel,  and  tarragon,  which  contain  that  compound  in  solu- 
tion, with  nitric  acid.  Anisic  aldehyde  is  first  produced,  according  to  the 
equation : 

C10H120       +      06    =    C8H802      +      C2H204      +       OH2, 
Anise-  Anisic  Oxalic 

camphor.  aldehyde.  acid. 

and  subsequently  oxidized  to  anisic  acid.  It  may  also  be  produced  syn- 
thetically by  treating  potassium  para-oxybenzoate  with  methyl  iodide, 
whereby  the  methylic  ether  of  methyl-paraoxybenzoic  acid  is  produced : 

C7H4K203       -f       2CH3I     =r    2KI       -f       C7H4(CH3)03.  CH3 
Potassium  Methylic 

para-oxybenzoate.  methyl-paraoxybenzoate. 

*  Kolbe  and  Lautemann,  Ann.  Ch.  Pharm.  cxv.  203. 


PHLORETIC — THYMOTIC  —  COUMARIC   ACIDS.        655 

And  boiling  this  compound  with  potash : 

C7H4(CH3)03.CH3     -f     OH2    =     CH3(OH)     +     C7H5(CH3)03 
Methylic  methyl-  Methyl  Met-hyl-para- 

paraoxybenzoate.  alcohol.  benzoic  acid. 

Ethyl-parabenzoic  acid,  CTH6(C2H6)03,  may  be  produced  in  a  precisely 
similar  manner. 

Anisic  acid  crystallizes  in  brilliant  colorless  prisms  melting  at  175°  C. 
(347°  F.),  moderately  soluble  in  hot  water,  easily  in  alcohol  and  ether.  It 
yields  substitution-products  with  chlorine,  bromine,  and  nitric  acid.  By 
distillation  with  lime  or  baryta  it  is  resolved  in  carbon  dioxide  and  ani- 
sol  or  methyl-phenol  (p.  551) : 

C8H803  C02          +  C7H802. 

Anisic  acid  is  monobasic,  and  most  of  its  salts  are  crystallizable. 

Phloretic  Acid,  C9H1003,  is  produced,  together  with  phloroglucin,  by  the 
action  of  potash  on  phloretin,  a  substance  resulting  from  the  action  of  di- 
lute acids  on  phlorizin  (p.  581) : 

C»HI406        +V      OH2        =        C9H1003        +        C6H603 
Phloretin.  Phloretic  Phloro- 

acid.  glucin. 

It  forms  prismatic  crystals  melting  at  about  129°  C.  (264°  F.),  somewhat 
less  soluble  in  water  than  in  alcohol;  produces  a  green  color  with  ferric 
chloride.  When  heated  with  lime  or  baryta,  it  is  resolved  into  carbon  di- 
oxide and  phlorol,  C9HJ00,  which  passes  over  as  a  brown  oily  distillate  : 

C9H1003         +         BaO         =        C03Ba         +         C8H100. 
Phloretic  acid  is  bibasic,  forming  acid  and  neutral  salts. 

Another  acid  containing  C9H,?03  is  formed  by  the  action  of  potash  on  the 
cyauo-hydrate  or  cyanhydrin  of  anisic  alcohol,  C8H1002: 

C8H8(CN)(OH)         +        20H2        =        NH3        -f        C9H1003 

Anisic  Acid, 

cyanhydrin. 

Thymotic  and  Thymyl-carbonic  Acids,  CnH1403. — These  isomeric  acids 
are  produced  simultaneously  by  the  action  of  sodium  and  carbon  dioxide 
on  thymol,C,0HuO  (p.  554) ;  and  are  separated  in  the  same  manner  as  the 
homologous  compounds,  cresyl-cai'bonic  and  cresotic  acids.  Thymotic  acid 
is  a  crystalline  body,  melting  at  120°,  nearly  insoluble  in  cold,  slightly 
soluble  in  boiling  water ;  it  produces  a  fine  blue  color  with  ferric  chloride. 
Heated  with  baryta,  it  is  resolved  into  carbon  dioxide  and  thymol. 


5.- Series  CnH2n_1003. 

Coumaric  Acid,  C9H803,  the  only  known  acid  of  this  series,  is  produced 
by  the  action  of  boiling  potash  solution  on  coumarin,  C9H602,  the  odorifer- 
ous principle  of  the  Tonka  bean.  It  crystallizes  in  laminae,  having  a  bitter 
taste,  soluble  in  water,  alcohol,  and  ether,  melting  at  190°  C.  (374°  F.). 
Fused  with  potash,  it  gives  off  hydrogen,  and  yields  potassium  salicylate 
and  apparently  also  acetate : 

C9H803     -f-     2KOH     =     C7H6K03     +     C2H3K02     -f     H2. 
It  is  monobasic,  and  decomposes  carbonates. 

There  are  no  known  acids  belonging  to  the  series  CnII2n_1203  and  CnH2n_,403. 


656  DIATOMIC   AND    BIBASIC   ACIDS. 

6.  — Series  CnH2n_1603. 

Benzilic  Acid,  C14H1203.  —  This  acid  is  produced  by  the  action  of  alcoholic 
potash  on  benzoin,  C14H,202,  a  polymeric  modification  of  benzoic  aldehyde, 
C7H602,  which  remains  in  the  retort  when  the  crude  oil  is  distilled  with 
lime  or  iron-oxide  to  free  it  from  hydrocyanic  acid  ;  or  on  benzile,  CUH,002, 
a  crystalline  substance  formed  from  benzoin  by  the  action  of  chlorine.  On 
saturating  the  alkaline  solution  with  hydrochloric  acid,  and  leaving  the 
filtered  liquid  to  cool,  benzilic  acid  separates  in  small  colorless  transparent 
crystals,  slightly  soluble  in  cold,  more  soluble  in  boiling  water;  it  melts 
at  120°  C.  (248°  F.),  and  cannot  be  volatilized  without  decomposition.  It 
dissolves  in  cold  strong  sulphuric  acid  with  fine  carmine  color. 


DIATOMIC  AND  BIBASIC  ACIDS. 

These  acids  contain  the  group  oxatyl,  C02H,  twice,  and  must  therefore 
contain  four  atoms  of  oxygen.  They  may  all  be  included  in  the  general 
formula,  R//(C02H)2, — B  denoting  a  diatomic  hydrocarbon-radical, — or 
they  may  be  regarded  as  compounds  of  oxygenated  radicals  with  two  equi- 
valents of  hydroxyl,  e.  g.,  succinic  acid  =  (C4H402)"  (OH)2. 

They  are  produced:  —  1.  By  oxidation  of  the  corresponding  glycols, 
B//(CH2OH)2,  the  change  consisting  in  the  substitution  of  O2  for  H4  (p.  557). 
In  this  manner  oxalic  acid,  C2H204,  is  formed  from  ethene  alcohol,  C2II602, 
and  malonic  acid,  C3H404,  from  propene  alcohol,  C3H802 ;  but  the  higher 
glycols  split  up  under  the  influence  of  oxidizing  agents,  and  do  not  yield 
bibasic  acids  containing  the  same  number  of  carbon-atoms  as  themselves. 

2.  By  boiling  the  cyanides  of  diatomic  alcohol-radicals  with  alcoholic 
potash ;  e.  g.  : 


(C.Ht)"{CN)a    +    2KOH    +    20H2    =    2NH3    +    (C8H6)"(C02K) 
Propene  Potassium 

cyanide.  pyrotartrate. 


This  reaction  is  analogous  to  that  by  which  the  fatty  acids  are  formed 
from  the  cyanides  of  the  monatomic  alcohol-radicals,  CnH2n-f  j  (p.  599). 

3.  By  the  addition  of  hydrogen  to  other  acids  containing  a  smaller  pro- 
portion of  that  element ;  in  this  manner  succinic  acid,  C4H604,  is  formed 
from  fumaric  acid,  C4H404. 

4.  By  the  action  of  heat  on  acids  of  more  complicated  structure  ;  e.  g. : 

2C4H606      =      3C02      +      20H2     -f     C6H804 
Tartaric  Pyrotar- 

acid.  taric  acid. 

5.  Many  of  these  acids  are  produced  by  the  action  of  powerful  oxidizers 
on  a  variety  of  organic  bodies:  thus,  succinic  acid,  C4H604,  and  its  homo- 
logues,  are  produced  by  treating  various  fatty  and  resinous  bodies  with 
nitric  acid. 

The  known  acids  of  this  group  belong  to  the  series  CnH2n_204,  CnH2n_404, 
CnH2D_804,  and  CnH2n_io04.  The  acids  of  the  first  series,  and  probably  also 
those  of  the  third  and  fourth,  are  saturated  compounds ;  but  those  of  the 
second  are  imsaturated,  being  capable  of  taking  up  two  atoms  of  hydrogen, 
bromine,  and  other  monad  elements,  whereby  they  are  converted  into  acids 
of  the  first  series. 


OXALIC    ACID. 


657 


1.  — Oxalic  or  Succinic  Series,  CnH2n_204. 
The  known  acids  of  this  series  are: 


Oxalic  acid 
Malonic  acid     . 
Succinic  acid    . 
Pyrotartaric  acid 
Adipic  acid 

•     C2H204 
•     C,H404 
.     C4H604 
•     C5H804 
•     C6H1004 

Pimelic  acid    . 
Suberic  acid    . 
Anchoic  acid  . 
Sebic  acid 
Roccellic  acid 

COOH 


Oxalic 


C7H1204 
C8H1404 
CH0 


=  (C2°2)//(°H)r  — This  important  acid 


lie  Acid,  C2H204  =  \ 

COOH 

exists  ready  formed  in  many  plants  as  a  potassium  or  calcium-salt,  and  is 
produced  by  the  oxidation  of  a  great  variety  of  organic  compounds.  In 
some  cases  the  reaction  consists  in  a  definite  substitution  of  oxygen  for  hy- 
drogen ;  thus  oxalic  acid  is  formed  from  ethene  alcohol,  C2H602,  by  sub- 
stitution of  02  for  H4,  and  from  ethyl  alcohol,  C2H60,  by  the  same  substitu- 
tion and  further  addition  of  one  atom  of  oxygen.  But  in  most  cases  the 
reaction  is  more  complex,  consisting  in  a  complete  breaking  up  of  the  mole- 
cule. In  this  manner  oxalic  acid  is  produced  in  great  abundance  from 
more  highly  carbonized  organic  substances,  such  as  sugar,  starch,  cellulose, 
&c.,  by  the  action  of  nitric  acid,  or  by  fusion  with  caustic  alkalies. 

Oxalic  acid  is  also  produced:  a.  As  a  sodium  or  potassium-salt  by  direct 
combination  of  the  alkali-metal  with  carbon  dioxide  : 

2C02        -f        Na2        =        C204Na2. 

The  sodium-salt  is  obtained  by  passing  the  carbon  dioxide  over  a  heated 
mixture  'of  sodium  and  sand ;  the  potassium-salt,  by  heating  potassium 
amalgam  in  the  gas.* 

0.  As  an  ammonium-salt,  together  with  other  products,  in  the  decompo- 
sition of  cyanogen  by  water: 


C2N2 


40H0 


C2(NH4)20< 


y.  As  a  potassium-salt  by  heating  potassium  formate  with  excess  of  pot- 
ash: 

2CHK02        =        C2K204        -f-        H2. 
Preparation. — 1.  By  the  oxidation  of  sugar  with  nitric  acid : 

C«H«0U        +        0I8        =        6C2H204        +        50H2. 

One  part  of  sugar  is  gently  heated  in  a  retort  with  5  parts  of  nitric  acid 
of  sp.  gr.  142,  diluted  with  twice  its  weight  of  water;  copious  red  fumes 
are  then  disengaged,  and  the  oxidation  of  the  sugar  proceeds  with  violence 
and  rapidity.  When  the  action  slackens,  heat  may  be  again  applied  to  the 
vessel,  and  the  liquid  concentrated,  by  distilling  off  the  superfluous  nitric 
acid,  until  it  deposits  crystals  on  cooling.  These  are  drained,  redissolved 
in  a  small  quantity  of  hot  water,  and  the  solution  is  set  aside  to  cool. 

2.  By  heating  sawdust  with  caustic  alkali. 

Many  years  ago,  Gay-Lussac  observed  that  wood  and  several  other  or- 
ganic substances  were  converted  into  oxalic  acid  by  fusion  with  caustic 
potash.  Messrs.  Roberts,  Dale  &  Co.  have  lately  founded  upon  this  obser- 
vation a  new  method  for  the  preparation  of  oxalic  acid,  which  furnishes 
this  acid  much  cheaper  than  any  other  process.  A  mixed  solution  of  the 
hydrates  of  sodium  and  potassium  in  the  proportion  of  two  equivalents  of 
the  former  to  one  of  the  latter,  is  evaporated  to  about  1  -35  sp.  gr.  and  then 
mixed  with  sawdust,  so  as  to  form  a  thick  paste,  which  is  placed  in  thia 
*  Kolbe  and  Drechsel,  Chem.  Soc.  Journal  [2],  vi.  121. 


658  DIATOMIC    AND   BIBASIC   ACIDS,  CnH2n_2O4. 

layers  on  iron  plates.  The  mixture  is  now  gradually  heated,  care  being 
taken  to  keep  it  constantly  stirred.  The  action  of  heat  expels  a  quantity 
of  water,  and  the  mass  intumesces  strongly,  with  disengagement  of  much 
inflammable  gas,  consisting  of  hydrogen  and  carbonetted  hydrogen.  The 
mixture  is  now  kept  for  some  hours  at  a  temperature  of  204°  C.  (400°  F.), 
care  being  taken  to  avoid  charring,  which  would  cause  a  loss  of  oxalic 
acid.  The  product  thus  obtained  is  a  gray  powder  ;  it  is  now  treated  with 
water  at  about  15-5°  C.  (60°  F.),  which  leaves  the  sodium  oxalate  undis- 
solved.  The  supernatant  liquid  is  drawn  off,  evaporated  to  dryness,  and 
heated  in  furnaces  to  recover  the  alkalies,  which  are  caustified  and  used 
for  a  new  operation.  The  sodium  oxalate  is  washed  and  decomposed  by 
boiling  with  slaked  lime,  and  the  resulting  calcium  oxalate  is  again  decom- 
posed by  means  of  sulphuric  acid.  The  liquid  decanted  from  the  calcium 
sulphate  is  evaporated  to  crystallization  in  leaden  vessels,  and  the  crystals 
are  purified  by  re-crystallization. 

Oxalic  acid  separates  from  a  hot  solution  in  colorless,  transparent  crys- 
tals derived  from  an  oblique  rhombic  prism,  and  consisting  of  C2H204. 
20H2.  The  two  molecules  of  crystallization- water  may  be  expelled  by  a 
very  gentle  heat,  the  crystals  crumbling  down  to  a  soft  white  powder,  con- 
sisting of  anhydrous  oxalic  acid,  C2H204,  which  may  be  sublimed  in  great 
measure  without  decomposition.  The  crystallized  acid,  on  the  contrary,  is 
decomposed  by  a  high  temperature  into  formic  acid,  carbon  monoxide  and 
carbon  dioxide,  without  leaving  any  solid  residue : 

2C2H204     =     CH202    -f     CO     +     2C02    +     OH2. 

The  crystals  of  oxalic  acid  dissolve  in  8  parts  of  water  at  15-5°,  and  in 
their  own  weight,  or  less,  of  hot  water:  they  are  also  soluble  in  spirit. 
The  aqueous  solution  has  an  intensely  sour  taste  and  most  powerful  acid 
reaction,  and  is  highly  poisonous.  The  proper  antidote  is  chalk  or  mngne- 
sia.  Oxalic  acid  is  decomposed  by  hot  oil  of  vitriol  into  a  mixture  of  car- 
bon monoxide  and  carbon  dioxide  :  it  is  slowly  converted  into  carbonic 
acid  by  nitric  acid,  whence  arises  a  considerable  loss  in  the  process  of 
manufacture  from  sugar.  The  dioxides  of  lead  and  manganese  eifect  the 
same  change,  becoming  reduced  to  monoxides,  which  form  salts  with  the 
unaltered  acid. 

Oxalates. — Oxalic  acid,  like  other  bibasic  acids,  forms  with  mon-atomic 
metals,  neutral  or  normal  salts  containing  C2M204,  and  acid  salts,  C2HM04. 
"With  potassium  and  ammonium  it  likewise  forms  hyper-acid  salts,  e.  g., 
C2HK04.  C2H204,  or  C4H3K08.  With  most  diatomic  metals  it  forms  only 
neutral  salts,  C2M//04;  with  barium  and  strontium,  however,  it  forms  acid 
salts  analogous  to  the  hyper-acid  oxalates  of  the  alkali-metals.  It  also 
forms  numerous  well-crystallized  double  salts.  It  is  one  of  the  strongest 
acids,  decomposing  dry  sodium  chloride  when  heated,  with  evolution  of 
hydrochloric  acid,  and  converting  sodium  chloride  or  nitrate  in  aqueous 
solution  into  acid  oxalate. 

The  oxalates  of  the  alkali-metals  are  soluble  in  water :  the  rest  are  for 
the  most  part  insoluble  in  water,  but  soluble  in  dilute  acids. 

All  oxalates  are  decomposed  by  heat.  The  oxalates  of  the  alkali-metals, 
and  also  of  the  alkaline  earth-metals,  if  not  too  strongly  heated,  give  off 
carbon  monoxide  and  leave  carbonates,  while  the  oxalates  of  those  metals 
whose  carbonates  are  decomposed  by  heat  (zinc  and  magnesium,  for  ex- 
ample) give  off  carbon  monoxide  and  carbon  dioxide,  and  leave  metallic 
oxides.  The  oxalates  of  the  more  easily  reducible  metals  (silver,  copper, 
&c.)  give  off  carbon  dioxide  and  leave  the  metal;  the  lead-salt  leaves  sub- 
oxide  of  lead,  and  gives  off  3  volumes  of  carbon  dioxide  to  1  volume  of  car- 
bon monoxide : 

2C2Pb404    =    Pb20    +     3C02    +     CO. 


OXALIC   ACID.  659 

Oxalates  heated  with  sulphuric  acid  give  off  carbon  monoxide  and  dioxide, 
and  leave  a  residue  of  sulphate.  In  this  case,  as  well  as  in  the  decompo- 
sition by  heat  alone,  no  separation  of  carbon  takes  place,  and  consequently 
the  residue  does  not  blacken :  this  character  distinguishes  the  oxalates 
from  the  salts  of  all  other  carbon  acids. 

Oxalic  acid  and  the  soluble  oxalates  give  with  calcium  chloride  a  precipi- 
tate of  calcium  oxalate,  insoluble  in  water  and  in  acetic  acid,  but  soluble 
in  hydrochloric  and  nitric  acid.  This  reaction  affords  a  very  delicate  test 
for  the  presence  of  oxalic  acid:  the  insolubility  of  the  precipitated  oxalate 
in  acetic  acid  distinguishes  it  at  once  from  the  phosphate. 

POTASSIUM  OXALATES. — The  neutral  salt,  C2K204  .  2  Aq.,  prepared  by  neu- 
tralizing oxalic  acid  with  potassium  carbonate,  crystallizes  in  transparent 
rJhombic  prisms,  which  become  opaque  and  anhydrous  by  heat,  and  dissolve 
in  3  parts  of  water. — The  acid  oxalate  or  binoxalate,  C2HK04 .  2  Aq.,  some- 
times called  salt  of  sorrel,  from  its  occurrence  in  that  plant,  is  found  also 
in  other  species  of  Rumex,  in  Oxalis  acetosella,  and  in  garden  rhubarb,  as- 
sociated with  malic  acid.  It  is  easily  prepared  by  dividing  a  solution  of 
oxalic  acid  in  hot  water  into  two  equal  portions,  neutralizing  one  with  po- 
tassium carbonate,  and  adding  the  other:  the  salt  crystallizes,  on  cooling, 
in  colorless  rhombic  prisms.  The  crystals  have  a  sour  taste,  and  require 
40  parts  of  cold,  and  6  of  boiling  water  for  solution.  A  solution  of  this  salt 
is  often  used  for  removing  ink  from  paper.  The  hyper-acid  oxalate  or  quad- 
roxalate,  C2HK04 .  C2H204 .  2  Aq.,  is  prepared  by  a  process  similar  in  prin- 
ciple to  that  last  described.  The  crystals  are  modified  octohedrons,  and 
are  less-  soluble  than  those  of  the  binoxalate,  which  the  salt  in  other  re- 
spects resembles. 

Sodium  oxalate,  C2Na204,  has  but  little  solubility ;  a  binoxalate  exists. 

AMMONIUM  OXALATES. — The  neutral  salt,  C2(NH4)204  .  2  Aq.,  is  prepared 
by  neutralizing  a  hot  solution  of  oxalic  acid  with  ammonium  carbonate.  It 
crystallizes  in  long,  colorless,  rhombic  prisms,  which  effloresce  in  dry  air 
from  loss  of  water  of  crystallization.  They  are  not  very  soluble  in  cold 
water,  but  dissolve  freely  by  the  aid  of  heat. 

The  dry  salt  when  heated  in  a  retort  gives  off  water,  and  yields  a  subli- 
mate of  oxamide :  * 

(C202)//(ONH4)2    =    20H2    +     (C202)"(NH2)2. 
Ammonium  oxalate.  Oxamide. 

When  distilled  with  phosphoric  oxide,  it  gives  up  four  molecules  of  water 
and  yields  a  considerable  quantity  of  cyanogen,  C2(NH4)204  —  40H2  =  2CN. 
Other  products  are,  however,  formed  at  the  same  time. 

Acid  ammonium  oxalate,  or  binoxalate,  C2H(NH4)04  .  Aq.,  is  still  less  soluble 
than  the  neutral  salt.  When  heated  in  an  oil-bath  to  232°  C.  (450°  F.),  it 
loses  one  molecule  of  water,  and  yields  oxamic  acid,  C2H3N03,  or  (C202)x/ 
(OH)(NH2);  other  producis  are,  however,  formed  at  the  same  time. 

CALCIUM  OXALATE,  C2Ca//04 .  4  Aq.,  is  formed  whenever  oxalic  acid  or  an 
oxalate  is  added  to  a  soluble  calcium-salt ;  it  falls  as  a  white  powder,  which 
acquires  density  by  boiling,  and  is  but  little  soluble  in  dilute  hydrochloric, 
and  quite  insoluble  in  acetic  acid.  Nitric  acid  dissolves  it  easily.  When 
dried  at  100°,  it  retains  a  molecule  of  water,  which  may  be  driven  off  by  a 
rather  higher  temperature.  Exposed  to  a  red  heat  in  a  close  vessel,  it  is 
converted  into  calcium  carbonate,  with  escape  of  carbon  monoxide. 

The  oxalates  of  barium,,  zinc,  manganese,  copper,  nickel,  cobalt,  and  ferrous 
oxalaU,  are  nearly  insoluble  in  water:  magnesium  oxalate  is  sparingly  solu- 
ble; ferric  oxalate  is  freely  soluble. — Pot assio- chromic  oxalate,  (C204)3Cr/// 
*  See  the  chapter  ou  Amides. 


660  DIATOMIC   AND   BIBASIC   ACIDS,  CnH2IJ_aO4. 

K3 .  3  Aq.,  prepared  by  dissolving  in  hot  water  1  part  of  potassium  bichro- 
mate, 2  parts  of  potassium  binoxalate,  and  2  parts  of  crystallized  oxalic 
acid,  is  one  of  the  most  beautiful  salts  known.  The  crystals  appear  black 
by  reflected  light  from  the  intensity  of  their  color,  which  is  pure  deep 
blue  :  they  are  very  soluble.  A  corresponding  potassio-fcrric  oxalate  has 
been  formed:  it  crystallizes  freely,  and  has  a  beautiful  green  color. 

ETHYL  OXALATES. — The  neutral  oxalate,  or  Oxalic  ether,  C204(C2H5)2,  is 
most  easily  obtained  by  distilling  together  4  parts  of  potassium  binoxalate, 
5  parts  of  oil  of  vitriol,  and  4  parts  of  strong  alcohol.  The  distillation  may 
be  pushed  nearly  to  dryness,  and  the  receiver  kept  warm  to  dissipate  any 
ordinary  ether  that  may  be  formed.  The  product  is  mixed  with  water,  by 
which  the  oxalic  ether  is  separated  from  the  undecomposed  spirit:  it  is 
repeatedly  washed  to  remove  adhering  acid,  and  re-distilled  in  a  small  re- 
tort, the  first  portion  being  received  apart  and  rejected.  Another  very 
simple  process  consists  in  digesting  equal  parts  of  alcohol  and  dehydrated 
oxalic  acid  in  a  flask  furnished  with  a  long  glass  tube  in  which  the  volatil- 
ized spirit  may  condense.  After  six  or  eight  hours'  digestion,  the  mixture 
generally  contains  only  traces  of  unetherified  oxalic  acid. 

Pure  oxalic  ether  is  a  colorless,  oily  liquid,  of  pleasant  aromatic  odor, 
and  1-09  sp.  gr.  It  boils  at  183-8°  C.  (362°  F.),  is  but  little  soluble  in  water, 
and  is  readily  decomposed  by  caustic  alkalies  into  a  metallic  oxalate  and 
alcohol.  With  solution  of  ammonia  in  excess,  it  yields  oxamide  and  alco- 
hol; thus: 

(C202)"(OC2H5)2    +    2NH3   =  2HOC2H5    +    (C202)"(NH2)2 
Ethyl  oxalate.  Ethyl  Oxamide. 

alcohol. 
This  is  the  best  process  for  preparing  oxamide. 

When  dry  gaseous  ammonia  is  conducted  into  a  vessel  containing  oxalic 
ether,  the  gas  is  rapidly  absorbed,  and  a  white  solid  substance  produced, 
which  is  soluble  in  hot  alcohol,  and  separates  on  cooling  in  colorless,  trans- 
parent, scaly  crystals.  They  dissolve  in  water,  and  are  both  fusible  and 
volatile.  This  substance  is  oxamethane,  the  ethylic  ether  of  oxamic  acid 
(p. 659): 

(C202)"(OC2H5)2    +     NH3    =    HOC2H5    +     C202(NH2)(OC2H6) 
Ethyl  oxalate.  Alcohol.  Ethyl  oxamate. 

The  same  substance  is  formed  when  ammonia  in  small  quantity  is  added  to 
a  solution  of  oxalic  ether  in  alcohol. 

When  oxalic  ether  is  treated  with  dry  chlorine  in  excess  in  sunshine,  a 
white,  colorless,  crystalline,  fusible  body  is  produced,  insoluble  in  water, 
and  instantly  decomposed  by  alcohol.  It  consists  of  pcrctdor ethylic  oxalate, 
C6C11004,  or  C204(C2C16)2,  or  oxalic  ether  in  which  the  whole  of  the  hydro- 
gen is  replaced  by  chlorine. 

Ethyl  oxalate  is  converted  by  potassium  or  sodium  into  ethyl  carbonate, 
with  evolution  of  carbon  monoxide:  C2(C2H5)204  =  C(C2H5)20S  -f  CO; 
but  the  reaction  is  complicated  by  the  formation  of  several  other  products. 

When  ethyl  oxalate  is  agitated  with  sodium  amalgam  in  a  vessel  exter- 
nally cooled,  a  product  is  obtained  which  is  separated  by  ether  into  a  soluble 
and  an  insoluble  portion,  the  latter  consisting  of  fermentable  sugar,  to- 
gether with  sodium  oxalate  and  at  least  one  other  sodium-salt,  while  the 
ethereal  solution  yields,  by  spontaneous  evaporation,  crystals  having  the 
composition  CnH]808,  and  consisting  of  the  ethylic  ether  of  a  tribasic  acid, 
C5H608,  called  desoxalic  acid,  because  it  is  produced  by  deoxidation  of  oxalic 
acid:  5C2H204  -f  5H2  =  2C6H608  -f  40H2;  and  racemo-carbonic  acid,  be- 
cause it,  contains  the  elements  of  racemic  acid,  C4H606,  and  carbon  dioxide, 
COg,  and  is  resolved  into  those  two  compounds  when  its  aqueous  solution  is 


MALONIC   ACID.  661 

heated  in  a  sealed  tube  with  a  small  quantity  of  sulphuric  acid.  The  de- 
composition of  ethylic  oxalate  by  sodium  amalgam  has  not  been  completely 
investigated,  but  the  formation  of  desoxalic  acid  and  glucose  may  be  re- 
presented by  the  equation : 

8C2H204     +     14H2    =     2C5H608    -f     C6H1206     +     10H20. 
Oxalic  acid.  Desoxalic  acid.     Glucose. 

Ethyl  oxalate  treated  with  zinc-ethyl,  and  afterward  with  water,  yields 
the  ethylic  ether  of  diethoxalic  acid,  C2H2(C2H5)2Oe,  and  similar  products 
with  zinc-methyl  and  zinc-amyl  (p.  G30). 

Acid  ethyl  oxalate,  or  Ethyloxalic  acid,  C2H(C2H5)04,  or  (C202)"(OH)(OC2 
H5),  is  obtained  as  a  potassium-salt  by  adding  to  a  solution  of  neutral  ethyl 
oxalate  in  absolute  alcohol,  a  quantity  of  alcoholic  potash  less  than  suffi- 
cient to  convert  the  whole  into  potassium  oxalate  and  alcohol;  on  dissolv- 
ing this  salt  in  hydrated  alcohol,  carefully  saturating  with  sulphuric  acid, 
and  neutralizing  with  carbonate  of  lead  or  barium,  the  ethyloxalate  of 
lead  or  barium  is  obtained.  —  The  acid  itself  is  prepared  by  decomposing 
either  of  these  salts  with  sulphuric  acid ;  but  it  is  very  unstable,  and  is  de- 
composed by  concentration  into  alcohol  and  oxalic  acid.  —  The  potassium- 
salt,  C2(C2H5)K04,  forms  crystalline  scales  which  begin  to  decompose  to- 
ward 100°. 

METHYL  OXALATE,  C2(CH8)204,  or  (C202)"(OCH3)2,  is  easily  prepared  by 
distilling  a  mixture  of  equal  weights  of  oxalic  acid,  wood-spirit,  and  oil  of 
vitriol.  A  spirituous  liquid  collects  in  the  receiver,  which,  when  exposed 
to  the  air,  quickly  evaporates,  leaving  the  methyl  oxalate  in  the  form  of 
rhombic,  transparent,  crystalline  plates,  which  may  be  purified  by  pressure 
between  folds  of  bibulous  paper,  and  redistilled  from  a  little  oxide  of  lead. 
The  product  is  colorless,  and  has  the  odor  of  ethyloxalate  ;  it  melts  at  51° 
C.  (123°  F.),  and  boils  at  161°C.  (321°  F.),  dissolves  freely  in  alcohol  and 
wood-spirit,  and  also  in  water,  which,  however,  rapidly  decomposes  it,  es- 
pecially when  hot,  into  oxalic  acid  and  wood-spirit.  The  alkaline  hydrates 
effect  the  same  change  even  more  easily.  Solution  of  ammonia  converts  it 
into  oxamide  and  methyl  alcohol.  With  dry  ammoniacal  gas  it  yields 
methyl  oxamate,  or  oxamethylane,  (C202)//(NH2)(OCH3),  a  white,  solid  sub- 
stance, which  crystallizes  from  alcohol  in  pearly  cubes. 

'  ETHENE  OXALATE,  C2(C2H4)"04,  or  (C202)"(C2H402)",  appears  to  be 
formed  by  the  action  of  ethene  bromide  on  silver  oxalate. 

Malonic  Acid,  C3H404  =  (CH2)//.  (C02H)2  ==  (C3H202)//(OH)2.  —  This 
acid  is  formed  by  the  slow  oxidation  of  propene  glycol  (p.  595) : 

C3H602      +       04      =      20H2      +       C3H404; 
also  by  oxidizing  malic  acid  with  a  cold  solution  of  potassium  chromate : 

C4H605    +     02    =•    C02    +     OH2    +     C3H404; 
Malic  Malonic 

acid.  acid. 

and  by  the  action  of  alkalies  on  cyanacetic  acid,  or,  better,  on  ethyl  cyan- 
acetate  : 

C2H2fCN)02 .  C2H6    +     30H2    =    NHS    -f     C2H60     +     C3H404 
Ethyl  cyanacetate.  Alcohol.      Malonic  acid. 

Malonic  acid   forms  large  rhombohedral  crystals,  soluble  in  water  and 
alcohol,  melting  at  140°  C.   (284°   F.),   and  resolved  at   150°  C.  (302°  F.) 
into  carbon  dioxide  and  acetic  acid. — Its  relations  to  bodies  of  the  uric 
acid  group  will  be  noticed  hereafter. 
50 


662  DIATOMIC   AND   BIBASIC   ACIDS,  CuH^O,. 

Succinic  Acid,  C4H604  =  (C2H4)"(C02H)2  =  (C4H402)"(OH)2.  —  This  acid 
is  produced:  1.  By  heating  ethene  cyanide*  with  alcoholic  potash: 

C2H4(CN)2     +     40H2    :   :    2NH3    +     C4H604. 

2.  By  the  action  of  nascent  hydrogen  (evolved  by  sodium-amalgam)  on 
maleic  acid,  or  its  isomer,  fumaric  acid,  C4H404  -\-  H2  =  C4H604. —  3.  By 
the  action  of  hydriodic  acid  (or  water  and  phosphorus  iodide)  on  malic 
acid,  C4Hb05,  or  tartaric  acid,  C2H606,  the  reaction  consisting  in  the  abstrac- 
tion of  1  or  2  atoms  of  oxygen,  with  formation  of  water  and  separation  of 
iodine.  —  4.  By  the  fermentation  of  malic  or  fumaric  acid,  and  of  many 
other  organic  substances,  especially  under  the  influence  of  putrefying 
casein;  in  small  quantity  also  during  the  alcoholic  fermentation  of  sugar 
(p.  516,  foot-note). — 5.  By  the  oxidation  of  many  organic  substances, 
especially  of  the  fatty  acids,  laH2n02,  and  their  glycerides,  under  the  in- 
fluence of  nitric  acid.  Its  formation  from  butyric  acid  is  represented  by 
the  equation  C4H802  -f-  03  =  OH2  -f  C4H6O4. 

Succinic  acid  occurs  ready  formed  in  amber  and  in  certain  lignites,  and 
occasionally  in  the  animal  organism.  By  heating  amber  in  iron  retorts,  it 
may  be  obtained  in  colored  crystals,  which  may  be  purified  by  treatment 
with  nitric  acid  and  re-crystallization  from  boiling  water.  The  acid  is, 
however,  more  advantageously  prepared  by  the  fermentation  of  malic  acid, 
the  crude  calcium  malate  obtained  by  neutralizing  the  juice  of  mountain- 
ash  berries  with  chalk  or  slaked  lime  being  used  for  the  purpose.  This 
salt  is  mixed  in  an  earthen  jar  with  water  and  yeast,  or  decaying  cheese, 
and  left  for  a  few  days  at  30°  or  40°;  the  calcium  succinate  thus  obtained 
is  decomposed  by  dilute  sulphuric  acid ;  and  the  succinic  acid  is  purified 
by  crystallization  from  water  and  by  sublimation. 

Succinic  acid  crystallizes  in  colorless,  oblique  rhombic  prisms,  which 
dissolve  in  5  parts  of  cold  and  in  3  parts  of  boiling  water:  it  melts  at 
180°  C.  (356°  F.)  and  boils  at  235°  C.  (455°  F.),  at  the  same  time  under- 
going decomposition  into  water  and  succinic  oxide,  or  anhydride,  C4H403,  or 
(C4H402)//0.  The  same  compound  is  formed  by  the  action  of  phosphorus 
pentachloride  on  succinic  acid:  C4H604  +  PC15  =  2HC1  -f  POC13  + 
C4H403.  It  is  a  white  mass,  less  soluble  in  water,  but  more  soluble  in  alco- 
hol, than  succinic  acid. 

Succinic  acid,  being  bibasic,  forms,  with  monad  metals,  acid  and  neutral 
salts,  C4H5M04  and  C4H4M204,  and  with  dyad  metals,  neutral  salts,  con- 
taining C4H4M//04,  and  acid  salts,  C4H4M04.  C4H604.  —  There  are  also  a 
few  double  succinates,  several  basic  lead-salts,  and  a  hyperacid  potassium- 
salt. 

Succinic  acid  is  distinguished  from  benzoic  acid  by  not  being  precipi- 
tated from  its  soluble  salts  by  mineral  acids,  and  by  forming  a  white  pre- 
cipitate with  barium  chloride,  on  addition  of  ammonia  and  alcohol. 

Pyrotartaric  Acid,  C^H804  =  (C3H6)"(C02H)2  =  (C6H602)"(OH)2,  is  pro- 
duced by  the  dry  distillation  of  tartaric  acid,  and  by  the  action  of  alco- 
holic potash  on  propene  cyanide,  C3H6(CN)2.  It  forms  rhombic  prisms, 
very  soluble  in  water,  alcohol,  and  ether;  melts  at  112°  C.  (233°  F.),  vola- 
tilizes at  about  200°  C.  (392°  F.),  being  partly  resolved  into  water  and 
pyrotartaric  oxide,  C6H603.  It  forms  acid  and  neutral  salts  analogous  to  the 
succinates. 

Adipic  Acid,  C6H,004,  and  Pimelic  Acid, -C7H1204,  are  produced  by  the  oxi- 
dation of  fats  with  nitric  acid. 

Suberic  Acid,  C8HU04,  has  long  been  known  as  a  product  of  the  oxida- 

*  Ethene  cyanide  is  obtained  by  heating  othene  bromide,  C2H4lir2,  with  an  alcoholic  solu- 
tion of  potassium  cyanide. 


FUMARIC   AND    MALEIC   ACIDS.  663 

tion  of  cork  by  nitric  acid.  Recently  it  has  been  produced,  together  with 
other  acids  of  the  series,  by  the  long-continued  action  of  nitric  acid  upon 
stearic  and  oleic  acids  and  other  fatty  bodies.  Suberic  acid  is  a  white 
crystalline  powder,  sparingly  soluble  in  cold  water,  fusible  and  volatile  by 
heat. 

Anchoic  Acid,  or  Lepargylic  Acid,  C9H1604,  is  formed,  together  with  other 
products,  by  the  action  of  nitric  acid  on  Chinese  wax  and  on  the  fatty  acids 
of  cocoa-nut  oil.  —  Azelaic  acid,  obtained  by  oxidizing  castor-oil  with  nitric 
acid,  has  the  same  composition  as  anchoic  acid,  but  differs  so  much  from  it 
in  physical  properties,  that  it  must  be  regarded  as  an  isonieric  or  allo- 
tropic  modification. 

Sebic  or  Sebacic  Acid,  C,0H,804,  is  a  constant  product  of  the  destructive 
distillation  of  oleic  acid,  oiein,  and  all  fatty  substances  containing  those 
bodies;  it  is  extracted  by  boiling  the  distilled  matter  with  water:  it  is 
also  formed  by  the  action  of  potash  on  castor-oil  (see  p.  652.)  It  forms 
small  pearly  crystals  resembling  those  of  benzoic  acid.  It  has  a  faintly 
acid  taste,  is  but  little  soluble  in  cold  water,  melts  when  heated,  and  sub- 
limes unchanged. 

Roccellic  Acid,  C17H3204,  exists  in  Roccella  tinctoria,  and  other  lichens  of 
the  same  genus,  also  in  Lecanora  tartarea,  and  is  obtained  by  exhausting 
the  first-mentioned  plant  with  aqueous  ammonia,  precipitating  the  filtered 
liquor  with  calcium  chloride,  and  decomposing  the  resulting  calcium-salt 
with  hydrochloric  acid.  When  purified  by  solution  in  ether,  it  forms 
white,  rectangular,  four-sided  tabular  crystals,  melting  at  132°  C.  (270°  F.), 
and  subliming  at  200°  C.  (392°  F.),  being  partially  converted  at  the  same 
time  into  an  oxide,  C17H3003.  This  acid  decomposes  carbonates. 


2.— Fumaric  Series  CnH2n_404. 
This  series  includes  the  two  following  groups  of  isomeric  acids: 

Fumaric  and  Maleic  acids  .....     C4H404 
Itaconic,  Citraconic,  and  Mesaconic  acids        .         C5H604. 

They  are  unsaturated  compounds,  capable  of  taking  up  two  atoms  of  hy- 
drogen, bromine,  and  other  monad  elements,  and  passing  into  acids  of  the 
preceding  series. 

Fumaric  and  Maleic  Acids,  C4H404=  (C2H2)"(C02H)2  =  (CJI202)"(OH)2. 
When  malic  acid  is  heated  in  a  small  retort,  nearly  filled,  it  melts,  emits 
water,  and  enters  into  ebullition,  and  a  volatile  acid  passes  over,  which 
dissolves  in  the  water  of  the  receiver.  After  a  time,  small  solid,  crystal- 
line scales  make  their  appearance  in  the  boiling  liquid,  and  increase  in 
quantity  until  the  whole  becomes  solid.  The  process  may  now  be  inter- 
rupted, and  the  contents  of  the  retort,  after  cooling,  treated  with  cold 
water:  unaltered  malic  acid  is  thereby  dissolved  out,  and  a  less  soluble  acid 
is  left  behind,  called  fumaric  acid,  from  its  identity  with  an  acid  extracted 
from  the  common  fumitory  (Fumaria  officinalis}. 

Fumaric  acid  forms  small,  white  crystalline  laminoo,  which  dissolve  freely 
in  hot  water  and  alcohol,  but  require  for  solution  about  200  parts  of  cold 
water:  it  is  unchanged  by  hot  nitric  acid.  When  heated  in  a  current  of 
air  it  sublimes,  but  in  a  retort  undergoes  decomposition ;  this  is  a  phenom- 
enon often  observed  in  organic  bodies  of  small  volatility.  Fumaric  acid 
forms  acid  and  neutral  metallic  salts,  and  an  ether,  which,  by  the  action  of 


664  DIATOMIC    AND   BIBASIC   ACIDS,  CnH2n_4O4. 

ammonia,  yields  fumaramide,    (C4H202)//(NH2)2,   in  the  form  of  a  white, 
amorphous,  insoluble  powder. 

The  volatile  acid  produced  simultaneously  with  fumaric  acid  is  called 
maleic  acid;  it  may  be  obtained  in  crystals  by  evaporation  in  a  warm  place. 
It  is  very  soluble  in  water,  alcohol,  and  ether,  has  a  strongly  acid  taste  and 
reaction,  and  is  convertible  by  heat  into  fumaric  acid.  Maleic  and  fumaric 
acids  are  formed  from  malic  acid  by  separation  of  a  molecule  of  water. 
Fumaric  acid,  when  heated  with  bromine,  combines  with  2  atoms  of  that 
element,  forming  dibromo  succinic  acid,  C4H4Br204,  which  resembles  in  all  its 
properties  the  dibrominated  acid  prepared  from  succinic  acid  by  direct 
substitution.  On  heating  fumaric  acid  with  hydriodic  acid,  it  passes  into 
succinic  acid.  The  same  reaction  takes  place  on  treating  fumaric  acid  with 
water  and  sodium-amalgam,  C3H404  -j-  H2  =  C4H604.  The  deportment  of 
maleic  acid  with  bromine  and  nascent  hydrogen,  is  perfectly  analogous  to 
that  of  fumaric  acid:  when  treated  with  hydriodic  acid,  it  passes  first  into 
fumaric  acid,  and  then  into  succinic  acid  (Kekule). 

Itaconic,  Citraconic,  and  Mesaconic  Acids,  C5E604. — The  first  two  of  these 
acids  are  produced  by  the  action  of  heat  on  citric  acid.  When  crystallized 
citric  acid  is  heated  in  a  retort  it  first  melts  in  its  water  of  crystallization, 
and  then  boils,  giving  oif  water.  Afterwards,  at  about  175°  C.  (347°  F.), 
vapors  of  acetone  distil  over,  and  a  copious  disengagement  of  carbon  mon- 
noxide  takes  place.  At  this  time  the  residue  in  the  retort  consists  of  aco- 
itic  acid.  If  the  distillation  be  still  continued,  carbon  dioxide  is  given 
oif,  and  itaconic  acid  crystallizes  in  the  neck  of  the  retort.  If  these  crys- 
tals be  repeatedly  distilled,  an  oily  mass  of  citraconic  oxide  or  anhydride  is 
obtained,  which  no  longer  solidifies.  These  compositions  are  represented 
by  the  following  equations : 

C6H807  —  OH2  =  C6H6Oe;         C6H606  —  C02  =  C5H604; 

Citric  Aconitic        Aconitic  Itaconic 

acid.  acid.  acid.  acid. 

C5H604        -        OH2        =         C5H403 

Itaconic  Citraconic 

acid.  oxide. 

The  citraconic  oxide  when  exposed  to  the  air  absorbs  moisture,  and  is  con- 
verted into  crystallized  citraconic  acid,  C5H604. 

Mesaconic  acid  is  produced  by  boiling  itaconic  acid  with  weak  nitric  acid. 
These  three  isomeric  acids  are  all  converted  by  nascent  hydrogen  into 
pyrotartaric  acid,  C5H804.  They  also  take  up  a  molecule  of  hydrobromic 
acid,  HBr,  forming  monobromopyrotartaric  acid,  C5H7Br04,  or  of  bromine, 
Br2,  forming  dibromopyrotartaric  acid.  Itaconic  and  citraconic  acids  are, 
however,  more  inclined  to  these  transformations  than  mesaconic  acid,  which 
is  altogether  a  more  stable  compound.* 

Camphoric  Acid,  C10H1604,  produced  by  heating  camphor  (C,0H160)  with 
nitric  acid,  is  likewise  included  in  the  general  formula,  CnH2n_404;  but  it 
appears  to  be  a  saturated  compound,  inasmuch  as  its  ethylic  ether  shows 
no  tendency  to  take  up  chlorine  or  other  elements.  The  acid  forms  small 
colorless  needles  or  plates,  of  acid  and  bitter  taste,  sparingly  soluble  in 
cold  water.  It  melts  when  heated,  and  yields  by  distillation  a  colorless, 
crystalline,  neutral  substance,  consisting  of  camphoric  oxide,  or  anhydride, 
CioHH°3-  Calcium  camphorate  when  distilled  yields  a  volatile  oil  consisting 
of  phorone,  C9HJ40,  the  ketone  of  camphoric  acid: 

C,0H)4Ca04        --=        C03Ca        -f        C9H,40. 

*  "For  an  explanation  of  the  isomerism  between  these  three  acids,  see  KekuU  (Bulletin  de  la 
Societe  Royale  de  Belgique  [2],  xxxiv.  8;  also  Laboratory,  p.  369). 


DIATOMIC   AND   BIBASIC   ACIDS,  CnH2n_^O4.  665 


3.— Series  CnH2n_604. 
The  only  known  acid  belonging  to  this  series  is : 

Mellitic  Acid,  C4H204,  which  occurs  as  an  aluminium-salt  in  a  very  rare 
mineral  called  mellite  or  honeystone,  found  in  deposits  of  lignite.  It  is 
soluble  in  water  and  alcohol,  and  is  crystallizable,  forming  colorless  needles. 
It  is  a  bibasic  acid,  forming  acid  and  neutral  salts:  the  mellitates  of  the 
alkali-metals  are  soluble  and  crystallizable  ;  those  of  the  earths  and  heavy 
metals  are  mostly  insoluble. 

Ammonium  mellitate  yields  by  distillation  paramide  and  euchroic  acid. 
The  former  is  a  white,  amorphous,  insoluble  substance,  containing  C4HN02 
(i.  e.,  acid  ammonium  mellitate,  C4H(NH4)04  minus  20H2),  and  convertible 
by  boiling  with  water  into  acid  ammonium  mellitate.  Euchroic  acid  forms 
colorless,  sparingly  soluble  crystals,  containing  in  the  anhydrous  state 
C6H4N204.  In  contact  with  metallic  zinc  and  deoxidizing  agents  in  general, 
it  yields  a  deep  blue  insoluble  substance  called  euchrone. 


4.  — Series  CnH2n_8O4. 

Quinonic  or  Quinoylic  acid,  C6H404,  is  not  actually  known,  but  its  dichlori- 
nated  derivative,  C6H2C1204,  is  produced  by  the  action  of  potash  on  tetra- 
chloroquinone,  C6C1402.  It  is  a  crystalline  substance,  which  gives  off  water 
when  heated.  It  is  bibasic,  forming  acid  and  neutral  salts. 

Orsellinic  acid,  C8H804,  and  Evernic  acid,  C9H,004,  perhaps  belong  to  the 
ne  series.      They  will  be  further  noticed  in  the  chapter  on  Coloring 


same 
Matters. 


6.  —  Series  CnH2n_1004. 

This  series  includes  the  isomeric  acids,  phthalic  and  terephthalic, 
C8H604 ;  also  insolinic  acid,  C9H804. 

Phthalic  Acid,  C8H604,  also  called  Alizaric  and  Naphthalic  acid,  is  pro- 
duced by  the  action  of  nitric  acid  on  naphthalene,  dichloride  of  naphtha- 
lene, alizarin,  and  purpurin  (the  coloring  matters  of  madder* ) : 

CIOH8         +        08  =  C8H604        +        C2H204 

Naphthalene.  Phthalic  acid.  Oxalic  acid. 

C,0H603        +     OH2+04     =  C8H604         -f        C2H204. 

Alizarin. 

2C9H.O,       +     OH2+06     =         2C8H60,        +         C2H204. 
Purpurin. 

It  is  usually  prepared  by  treating  naphthalene  dichloride  with  boiling  ni- 
tric acid. 

Phthalic  acid  crystallizes  in  colorless  plates :  it  is  but  slightly  soluble  in 
cold  water,  but  dissolves  freely  in  alcohol  and  ether.  It  is  bibasic,  form- 
ing acid  and  neutral  salts.  When  heated,  it  loses  a  molecule  of  water,  and 
leaves  phthalic  oxide,  C8TI403.  Treated  with  fuming  nitric  acid,  it  yields 
nitro-phthalic  acid,  C8H5(N02)04.  When  distilled  with  baryta,  it  gives  off 
benzene: 

C8H604         +         2BaO        =        2C03Ba         +         C6H6. 
56* 


666  TEIATOMIC   AND    MONOBASIC   ACIDS. 

Terephthalic  Acid,  C8H604,  is  produced  by  the  oxidizing  action  of  nitric 
acid  on  turpentine  oil,  lemon-oil,  and  other  terpenes,  also  on  cymene.  It 
is  a  white,  tasteless,  crystalline  powder,  not  perceptibly  soluble  in  water, 
alcohol,  or  ether.  It  is  distinguished  from  phthalic  acid  by  subliming 
without  alteration  when  heated,  and  not  being  resolved  into  water  and  an 
anhydride.  Although  bibasic,  it  forms  no  double  salts,  and  shows  but  little 
tendency  to  form  acid  salts.  Nearly  all  the  terephthalates  are  soluble  arid 
crystallizable,  and  so  inflammable  that  they  may  be  set  on  fire  by  a  spark 
from  a  flint  and  steel,  and  burn  away  slowly  like  tinder,  emitting  the  odor 
of  benzene. 

Insolinic  Acid,  C9H804,  is  produced  by  the  action  of  potassium  bichro- 
mate and  sulphuric  acid  on  cumic  acid,*  and  by  that  of  nitric  acid  on  coal- 
tar  cumene  (trimethyl-benzene,  p.  498),  zylic  acid  being  first  produced,  and 
afterward  further  oxidized  to  insolinic  acid:  f 

C10H,,02        +        06        =       C02      +      20H2      +        C9H804 
Cumic  Isolinic 

acid.  acid. 

C9H12         +        03        =  C?H1002  +        OH2 

Cumene.  Zylic  acid. 

CgHjoO,        +         03        =  C9H804  -f         OH2. 

Zylic  acid.  Insolinic  acid. 

Insolinic  acid  is  a  white  crystalline  powder,  and  resembles  terephthalic 
acid  in  being  nearly  insoluble  in  cold  and  sparingly  soluble  in  hot  water  ; 
from  hot  alcohol  it  separates  in  crystalline  crusts.  When  heated  it  sub- 
limes without  previous  fusion,  and  in  part  without  decomposition.  It  is 
bibasic,  forming  neutral  acid  and  double  salts,  also  a  neutral  and  acid 
ethylic  ether  (Hofmann). 


TRIATOMIC  AND  MONOBASIC  ACIDS. 

These  acids  are  derived  from  triatomic  alcohols  by  substitution  of  0  for 
H2,  as  glyceric  acid,  C3H604,  from  glycerin,  C3H803: 

CH2OH  CH2OH 

CHOH  CHOH 

CH2OH  COOH 

Glycerin.  Glyceric  acid. 

The  known  acids  of  the  group  are : 


Glyoxylic  acid        .         C2H404 
Glyceric  acid     .         .     C3H604 


Eugetic  acid          .         CnH12D4 
Piperic  acid     .         .     C12Hi004 


Oxysalicylic  acid   .         C7H604 
OH 
Glyoxylic  Acid,  C2H404    =     CHOH.  — This  acid  is  produced:  1.  By  the 

COOH 

action  of  nascent  hydrogen  (evolved  by  zinc  and  sulphuric  acid)  on  oxalic 
acid:  C2H204  +  H2  =  C2H404. 


*  Hofmann,  Ann.  Ch.  Pharm.  xcvii.  197. 

t  Hired  and  Heilstein,  Bull.  Soc.  Chim.  de  Paris  [2J,  vii.  345. 


GLYCERIC  —  OXYSALICYLIC    ACIDS.  667 

2.  By  boiling  silver  bromogly collate  with  water: 

C2H2AgBrOs     +         OH2         =        AgBr          +          C2H404. 

3.  By  the  oxidation  of  glycol,  alcohol,  or  glyoxal  with  nitric  acid : 

C2H602  +  03        =        C2H404       +         OH2 

Glycol. 

C2H60  +  04        =        C2H404       +         OH2 

Alcohol. 

C2H202  -f-  0          -f        OH2  =         C2H404. 

Glyoxal. 

Glyoxylic  acid  may  be  obtained  by  evaporation  in  the  form  of  a  viscid 
transparent  syrup,  which  dissolves  readily  in  water,  and  distils  without 
alteration  at  100°.  It  dissolves  zinc  without  evolution  of  hydrogen,  and  is 
converted  into  glycolic  acid  :  C2H404  -f-  H8  =  C2H403  +  OH2.  Glyoxylic 
acid  forms  salts  most  of  which  are  represented  by  the  formulae  C2H304M, 
and  (C2HS04)2M",  e.  g.,  the  silver-salt  is  C2H304Ag,  and  the  calcium-salt, 
(C2H304)2Ca//.  The  ammonium- salt,  however,  has  the  composition  C2H02 
(NH4),  apparently  derived  from  an  acid  containing  C2H203.  This  is  indeed 
the  formula  originally  assigned  to  glyoxylic  acid  by  Debus,*  who  discovered 
it.  This  formula  is  perfectly  consistent  with  the  formation  of  the  acid  by 
oxidation  of  glyoxal,  glycol,  and  alcohol ;  but,  on  the  other  hand,  its  forma- 
tion from  oxalic  and  from  bromoglycolic  acid  seems  rather  to  show  that  it 
consists  of  C2H404.f  Moreover,  if  the  acid  were  really  C2H203,  it  would 
be  necessary  to  suppose  that  all  the  glyoxylates,  except  the  ammonium  salt, 
contain  water  of  crystallization,  the  silver-salt,  for  example,  being  C2H03 
Ag.OH2 ;  now,  there  is  no  other  known  instance  of  a  silver-salt  containing 
water.  The  ammonium-salt  above  mentioned  is  probably  an  amide,  (C2H3 
03)NH2,  formed  from  the  true  ammonium  glyoxylate,  C2H304(NH4),  by  ab- 
straction of  water. 

Glyceric  Acid,  C3H604.  —  This  acid,  isomeric  with  pyruvic  acid,  is  pro- 
duced by  the  action  of  nitric  acid  on  glycerin:  also  by  the  spontaneous 
decomposition  of  nitroglycerin,  and  by  heating  glycerin  with  bromine  and 
a  large  quantity  of  water  to  100°  in  a  sealed  tube : 

C3H803    +     2Br2     -f     OH2    =     4HBr     +     C3H604. 

Glyceric  acid,  when  concentrated,  is  a  colorless  non-crystallizing  syrup 
'which,  when  heated  for  some  time  to  105°  C.  (221°  F .),  gives  off  water  and 
is  converted  into  glyceric  oxide  or  anhydride,  C3H403.  This  acid,  treated 
with  phosphorus  iodide,  is  converted  into  iodopropionic  acid,  C3H5I02. 

The  gly cerates,  C3H504M'  and  (CSH504)2M//,  are  soluble  in  water  and 
crystallize  well.  They  are  not  reddened  by  ferrous  sulphate,  and  are 
thereby  distinguished  from  the  pyruvates,  with  which  they  are  isomeric. 

Oxysalicylic  Acid,  C7I1604,  is  produced  by  boiling  a  solution  of  iodosali- 
cylic  acid,  C7H5I03,  with  potash.  It  forms  highly  lustrous  needles,  soluble 
in  water,  alcohol,  and  ether.  The  aqueous  solution  is  colored  deep  blue  by 
ferric  chloride.  The  crystallized  acid  melts  at  193°  C.  (379°  F.),  and  is 
resolved  between  210°  and  212°  C.  (410°-414°  F.)  into  carbonic  dioxide  and 
oxyphenol  or  pyrocatechin,  C6H602  (p.  562),  and  its  isomer,  hydro-quinone. 
The  oxysalicylates  are  very  unstable. 

There  are  three  acids  isomeric  with  oxysalicylic  acid,  viz.,  hypogallic 
acid,  produced  by  the  action  of  boiling  hydriodic  acid  on  hemipinic  acid, 

C  10^  10^6  : 

C10H1006    -f     2HI    =    C7H604    -f     2CH3I     +    C02; 

*  Phil.  Mag.  [4],  xii.  36. 

t  1'erkin  and  Duppa,  Obem.  Soc.  J.  [2],  vi.  197. 


668  TBIATOMIC   AND   BIBASIC   ACIDS. 

protocatechuic  acid,  produced,  together  with  oxalic  and  acetic  acids,  by  the 
action  of  melted  potash  on  piperic  acid,  C12H,004: 

C12H1004  +  80H2  =  C7H604  +  C2H204  +  C2H402  +  C02+  7H2, 

and  carbohydroquinonic  acid,  produced  by  a  peculiar  transformation  of  quinic 
acid. 

Eugetic  Acid,  CUH1204,  is  produced  by  the  action  of  carbon  dioxide  and 
sodium  on  eugenol  or  eugenic  acid  (oxidized  essence  of  cloves) : 

C10HuNa02  +  C02  C11H11NaO, 

Sodium  Sodium 

eugenate.  eugetate. 

It  crystallizes  from  hot  aqueous  solution  in  long  colorless  prisms,  melting 
at  124°  C.  (255°  F.),  slightly  soluble  in  cold  water,  very  soluble  in  alcohol 
and  ether.  The  aqueous  solution  is  colored  blue  by  ferric  chloride.  The 
acid  is  resolved  by  heat  into  carbon  dioxide  and  eugenic  acid. 

Piperic  Acid,  C12H1004,  is  produced,  together  with  piperidine,  by  boiling 
piperine  (an  alkaloid  from  pepper)  with  potash  : 

C17H19N03        +        OH2        =        CI2H1004         +        C5HUN 
Piperine.  Piperic  Piperidine. 

acid. 

It  forms  yellowish  capillary  needles,  melting  at  150°  C.  (302°  F.),  and  sub- 
liming at  about  200°  C.  (392°  F.) ;  nearly  insoluble  in  water,  easily  soluble 
in  boiling  alcohol.  When  fused  with  potassium  hydrate  it  yields  protoca- 
techuic acid,  together  -with  other  products.  The  piperates  even  of  the 
alkali-metals  are  sparingly  soluble  in  water,  the  rest  insoluble. 


TRIATOMIC  AND  BIBASIC  ACIDS. 


The  only  known  acids  of  this  group  are  malic  acid,  C4H605,  and  tartronic 
acid,  C3H405,  obtained  by  the  spontaneous  decomposition  of  nitrotartaric 
acid,  and  perhaps  also  croconic  acid,  C5H205  (p.  678). 

H  -|0 

Malic  Acid,  C4H605  =  (C4HS02)'"(OH)8,  or  (C4H8Oa)'"  VX  .—This  acid 


is  formed  synthetically  by  the  action  of  moist  silver  oxide  on  monobromo- 
succinic  acid: 

2C4H5Br04    +     OAg2     -f     OH2    =    2AgBr     +     2C4H605. 

It  is  also  produced  by  the  action  of  nitrous  acid  on  asparagin,  a  sub- 
stance existing  in  asparagus,  marsh-mallow,  and  other  plants,  or  on  aspar- 
tic  acid,  an  acid  formed  by  the  decomposition  of  asparagin  under  the  influ- 
ence of  acids  or  alkalies: 

C4H8N203     -f     2N02H     =     C4H605      -f     20H2     -f     2N2. 
Asparagin.  Malic  acid. 

C4H7N04      -f      N02H      ==      C4H606      -f      OH2     -f      N2. 
Aspartic  acid.  Malic  acid. 

Malic  acid  is  the  acid  of  apples,  pears,  and  various   other  fruits :  it 
often  associated  with  citric  acid.     An  excellent  process  for  preparing  it  is 


TRIATOMIC   AND    TRIBASIC   ACIDS.  669 

that  of  Everitt,  who  has  demonstrated  its  existence,  in  great  quantity,  in 
the  juice  of  the  common  garden  rhubarb  :  it  is  there  accompanied  by  acid 
potassium  oxalate.  The  rhubarb  stalks  are  peeled,  and  ground  or  grated 
to  pulp,  which  is  subjected  to  pressure.  The  juice  is  heated  to  the  boiling 
point,  neutralized  with  potassium  carbonate,  and  mixed  with  calcium  ace- 
tate: insoluble  calcium  oxalate  then  falls,  and  may  be  removed  by  filtra- 
tion. To  the  clear  and  nearly  colorless  liquid,  solution  of  lead  acetate  is 
added  as  long  as  a  precipitate  continues  to  be  produced;  and  the  lead  ma- 
late  is  collected  on  a  filter,  washed,  diffused  through  water,  and  decom- 
posed by  sulphuretted  hydrogen.*  The  filtered  liquid  is  carefully  evap- 
orated to  the  consistence  of  a  syrup,  and  left  in  a  dry  atmosphere  until  it 
becomes  converted  into  a  solid  and  somewhat  crystalline  nruass  of  malic 
acid:  regular  crystals  have  not  been  obtained.  From  the  berries  of  the 
mountain-ash  (Sorbus  aucuparia),  in  which  malic  acid  is  likewise  present  in, 
considerable  quantity,  especially  at  the  time  they  begin  to  ripen,  the  acid 
may  be  prepared  by  the  same  process. 

Malic  acid  is  colorless,  slightly  deliquescent,  and  very  soluble  in  water: 
alcohol  also  dissolves  it.  The  aqueous  solution  has  an  agreeable  acid  taste : 
it  becomes  mouldy  and  spoils  by  keeping.  In  contact  with  ferments,  es- 
pecially of  putrefying  cheese,  it  is  decomposed,  yielding  succinic  and  acetic 
acids  and  carbon  dioxide : 

3C4H605  =  2C4H604   -f    C2H402    +     2C02     -f-     OH2. 

Sometimes  also  butyric  acid  and  hydrogen  are  found  among  the  products 
of  the  fermentation.  Malic  acid  is  converted  into  succinic  acid  by  digest- 
ing it  in  sealed  tubes  with  hydriodic  acid: 

C4H605     +     2HI     =     C4IJ604     +     OH2     +     I2. 

The  reconversion  of  succinic  into  malic   acid  has  been  already  mentioned. 
The    sodium-salt    of  bromomalic  acid,  C4H5Br05,   obtained  by  boiling  an 
aqueous  solution  of  sodium  dibromosuccinate  (C4II3NaBr204),  is  converted 
by  boiling  with  lime-water  into  the  calcium-salt  of  tartaric  acid,  C4H606 : 
C4H5Br05      +       OH2      =       HBr       +       C4H606. 

Malic  acid  forms  both  acid  and  neutral  salts.  The  most  characteristic 
of  the  malates  are  acid  ammonium  malate,  C4H505(NH4),  which  crystallizes 
remarkably  well,  and  lead  malate,  C4H405Pb//  .  3  Aq.,  which  is  insoluble  in 
pure  water,  but  dissolves  to  a  considerable  extent  in  warm  dilute  acids,  and 
separates  on  cooling  in  brilliant  silvery  crystals,  containing  water.  By 
this  character  the  acid  may  be  distinguished.  Acid  calcium  malate,  C4H405 
Ca  .  C4H605  .  8  Aq.,  is  also  a  very  beautiful  salt,  freely  soluble  in  warm 
water.  It  is  prepared  by  dissolving  the  sparingly  soluble  neutral  malate  in 
hot  dilute  nitric  acid,  and  leaving  the  solution  to  cool. 

Malic  acid,  as  it  exists  in  plants,  and  as  obtained  from  asparagin,  or 
from  aspartic  acid  produced  from  the  latter,  exerts  a  rotatory  action  on 
polarized  light ;  [<*]=  —  5°  ;  but  by  the  action  of  nitrous  acid  on  inactive 
aspartic  acid  (resulting  from  the  decomposition  of  fumarimide),  Pasteur 
has  obtained  a  modification  of  malic  acid  which  is  also  optically  inactive. 


TRIATOMIC  AND  TRIBASIC  ACIDS. 

But  few  of  these  acids  have  yet  been  obtained ;  the  most  important  are 
aconitic  acid  and  carballylic  acid. 

*  If  the  acid  bo  required  pure,  crystallized  lead  malate  must  be  used,  the  freshly  precipi- 
t;xt«'<l  salt  invariably  carrying  down  a  quantity  of  lime,  which  cannot  be  removed  by  simple 
washing. 


670  TETKATOMIC   ACIDS. 

Aconitic  Acid,  C6H603  =  (C6H303)///(OH)3,  exists  in  monk's-hood  (Aconi- 
tum  Napellus],  and  other  plants  of  the  same  genus,  also  in  Equisetum  fluvia- 
tile,  and  is  one  of  the  products  obtained  by  the  dehydration  of  citric  acid 
(p.  6G4). 

When  crystallized  citric  acid  is  heated  in  a  retort  till  it  begins  to  become 
colored,  and  to  undergo  decomposition,  and  the  fused,  glassy  product,  after 
cooling,  is  dissolved  in  water,  aconitic  acid,  on  evaporation,  remains  as  a 
white,  confusedly  crystalline  mass,  permanent  in  the  air,  and  very  soluble 
in  water,  alcohol,  and  ether;  the  solution  has  an  acid  and  astringent  taste. 
The  salts  of  aconitic  acid  possess  but  little  interest ;  that  of  barium  forms 
an  insoluble  gelatinous  mass ;  calcium  aconitale,  which  has  a  certain  degree 
of  solubility,  is  found  abundantly  in  the  expressed  juice  of  monk's-hood, 
and  magnesium  aconitate  in  that  of  equisetum. 

Carballylic  Acid,  C6H806  =  (C6H503)"'(OH)3  =  (C3H5)'"(C02H)3,  is  pro- 
duced by  the  action  of  nascent  hydrogen  on  aconitic  acid,  and  by  that  of 
alcoholic  potash  on  propenyl  tricyanide,  or  tricyanhydrin: 

(C3H5)"'(CN)3  -f-  3KOH  -f  30H2  ==  3NH3  +  (C3H5)'"(C02K)3 
Tricyanhydrin.  Potassium 

carballylate. 

It  forms  colorless  trimetric  crystals  easily  soluble  in  water  and  alcohol, 
slightly  soluble  in  ether.  The  carballylates  of  the  alkali-metals  are  easily 
soluble  in  water,  the  rest  insoluble  or  sparingly  soluble.  The  ethylic  ether, 
(C6H503)///(OC2H5)3,  is  a  liquid  boiling  between  295°  and  305°  C.  (563°- 
581°  E.). 


TETRATOMIC  ACIDS. 


These  acids  may  be  derived  from  tetratomic  alcohols  by  substitution  of 
one,  two,  three,  or  four  atoms  of  oxygen  for  a  corresponding  number  of 
hydrogen  molecules : 

CH2OH  CH2OH  COOH 

CHOH  CHOH  CHOH 

CHOH  CHOH  CHOH 

CH2OH  COOH  COOH 

Erythrite.  Erythric  acid  Tartaric  acid 

(monobasic).  (bibasic). 

Only  one  tetratomic  acid  has,  however,  been  actually  formed  by  oxida- 
tion of  the  corresponding  alcohol,  namely,  erythric  acid,  C4H805,  from 
erythride,  C4H,004. 

The  known  tetratomic  acids  are  Gallic  acid,  C7H605,  and  Erythric  acid, 
C4H805,  which  are  monobasic ;  Tartaric  acid,  C4H606,  and  an  acid,  C6Hg06, 
homologous  with  it,  obtained  by  the  action  of  moist  silver  oxide  on  dibromo- 
pyrotartaric  acid,  which  are  bibasic,  and  Citric  acid,  C6H807,  which  is  tri- 
basic. 

Opianic  acid,  C]0H,005,  Ilemipinic  acid,  C]0H1006,  and  Meconic  acid,  C7Hg07, 
are  probably  also  tetratomic  acids;  the  first  being  monobasic,  the  second 
bibasic,  and  the  third  tribasic. 

H3        I 
Gallic  Acid,   C7H605  =  (C7H20)'"(OH)4  =  (C7H20)*  \04.  —  This  acid 


TANNIC   ACIDS.  671 

exists  ready  formed  in  certain  plants,  as  sumach,  hellebore  root,  the  acorns 
of  Quercus  segilops,  green  and  black  tea,  and  others ;  it  is  also  produced  by 
the  transformation  of  gallo-tannic  acid,  and  is  therefore  found,  together 
with  the  latter,  in  old  nut-galls.  A  solution  of  tannic  acid  in  water  exposed 
to  the  air,  gradually  deposits  crystals  of  gallic  acid,  formed  by  the  destruc- 
tion of  the  tannic  acid.  The  simplest  method  of  preparing  gallic  acid  in 
quantity  is  to  take  powdered  nut-galls,  which,  when  fresh  and  of  good 
quality,  contain  30  or  40  per  cent,  of  tannic  acid,  with  scarcely  more  than 
a  trace  of  gallic;  mix  this  powder  with  water  to  a  thin  paste,  and  expose 
the  mixture  to  the  air  in  a  warm  situation  for  two  or  three  months,  adding 
water  from  time  to  time,  to  replace  that  lost  by  drying  up.  The  mouldy, 
dark-colored  mass  thus  produced  may  then  be  strongly  pressed  in  a  cloth, 
and  the  solid  portion  boiled  in  a  considerable  quantity  of  water.  The 
filtered  solution  deposits  on  cooling  abundance  of  gallic  acid,  which  may 
be  drained  and  pressed,  and  finally  purified  by  recrystallization. 

Gallic  acid  has  lately  been  produced  by  the  action  of  moist  silver  oxide 
on  dibromo-,  or  di-iodosalicylic  acid  : 

C7H4Br203     +     OAg2     +     OH2     =     2AgBr     +     C7H605; 

hence  it  may  be  regarded  as  dioxysalicylic  acid. 

Gallic  acid  forms  small,  feathery,  and  nearly  colorless  crystals,  which 
have  a  beautiful  silky  lustre;  they  contain  C7H605.  Aq. ;  it  requires  for  solu- 
tion 100  parts  of  cold  and  only  3  parts  of  boiling  water ;  the  solution  has 
an  acid  and  astringent  taste,  and  is  gradually  decomposed  by  keeping. 
Gallic  acid  does  not  precipitate  gelatin ;  with  ferrous  salts  it  produces  no 
change;  but  with  ferric  salts,  it  forms  a  deep  bluish-black  precipitate, 
which  disappears  when  the  liquid  is  heated,  from  the  reduction  of  the 
ferric  to  ferrous  salt  at  the  expense  of  the  gallic  acid. 

The  salts  of  gallic  acid  present  but  little  interest;  those  of  the  alkali- 
metals  are  soluble,  and  readily  destroyed  by  oxidation  in  presence  of  excess 
of  base,  the  solution  acquiring  after  some  time  a  nearly  black  color;  the 
gallates  of  most  of  the  other  metals  are  insoluble. 

Gallic  acid  heated  to  about  215°  C.  (419°  F.)  is  resolved  into  carbon 
dioxide  and  pyrogallol  or  pyrogallic  acid,  C6H603  (p.  570),  which  sublimes 
in  crystalline  plates. 

Gallic  acid  and  pyrogallic  acid  reduce  salts  of  gold  and  silver  to  the 
jnetallic  state:  it  is  on  this  property  that  their  application  in  photography 
depends. 

When  dry  gallic  acid  is  suddenly  heated  to  249°  C.  (480°  F.),  or  above, 
it  is  decomposed  into  carbon  dioxide,  water,  and  metagallic  acid,  C6H402, 
which  remains  in  the  retort  as  a  black,  shining  mass,  resembling  charcoal ; 
a  few  crystals  of  pyrogallic  acid  are  formed  at  the  same  time.  Metagallic 
acid  is  insoluble  in  water,  but  dissolves  in  alkalies,  and  is  again  precipi- 
tated as  a  black  powder  by  the  addition  of  an  acid.  It  forms  insoluble  salts 
with  lead  and  silver.  Pyrogallic  acid,  also,  when  exposed  to  the  requisite 
temperature,  yields  metagallic  acid,  with  separation  of  water. 


Appendix  to  Gallic  Acid. 
TANNIC  ACIDS,  OR  TANNINS. 

These  substances  constitute  the  astringent  principles  of  plants,  and  are 
widely  diffused,  in  one  form  or  other,  through  the  vegetable  kingdom.  It 
is  possible  that  there  may  be  several  distinct  modifications  of  tannic  acid, 
which  differ  among  themselves  in  some  particulars.  The  astringent  prin- 


672  TANNIC   ACIDS. 

ciple  of  oak-bark  and  nut-galls,  for  example,  is  found  to  precipitate  ferric 
salts  bluish-black,  while  that  from  the  leaves  of  the  sumach  and  tea-plant, 
as  well  as  infusions  of  the  substances  known  in  commerce  under  the  names 
of  kino  and  catechu,  are  remarkable  for  giving,  under  similar  circumstances, 
precipitates  which  have  a  tint  of  green.  The  color  of  a  precipitate  is,  how- 
ever, too  much  influenced  by  external  causes  to  be  relied  upon  as  a  proof 
of  essential  difference.  Moreover,  the  tannic  acid  or  acids  appear  to  be 
uncrystallizable  ;  one  most  valuable  test  of  individuality  is  therefore  lost. 

After  the  reaction  with  ferric  salts,  the  most  characteristic  feature  of 
tannic  acid  and  the  other  astringent  infusions  referred  to,  is  that  of  form- 
ing insoluble  compounds  with  a  great  variety  of  organic,  and  especially 
animal  substances,  as  solutions  of  starch  and  gelatin,  solid  muscular  fibre, 
skin,  &c.,  which  then  acquire  the  property  of  resisting  putrefaction:  it  is 
on  this  principle  that  leather  is  manufactured.  Gallic  acid,  on  the  con- 
trary, is  useless  in  the  operation  of  tanning. 

Tannic  Acid  of  the  Oak,  Gallotannic  acid,  C27H22017. — This  substance  may 
be  prepared  by  Pelouze's  method,  from  nut-galls,  which  are  excrescences 
produced  on  the  leaves  of  a  species  of  oak,  the  Quercus  infectoria,  by  the 
puncture  of  an  insect.  A  glass  vessel, — having  somewhat  the  figure  of  that 
represented  in  Fig.  195,  is  loosely  stopped  at  its  lower  ex- 
tremity  by  a  bit  of  cotton  wool,  and  half  or  two-thirds  filled 
with  powdered  Aleppo  galls.  Ether,  prepared  in  the  usual 
manner  by  rectification,  and  containing  as  it  invariably  does 
a  little  water,  is  then  poured  upon  the  powder,  and  the  vessel 
loosely  stopped.  The  liquid,  which  after  some  time  collects 
in  the  receiver  below,  consists  of  two  distinct  strata  :  the 
lower,  which  is  almost  colorless,  is  a  very  strong  solution  of 
nearly  pure  tannic  acid  in  water  ;  the  upper  consists  of  ether 
holding  in  solution  gallic  acid,  coloring  matter,  and  other  im- 
purities. The  carefully  separated  heavy  liquid  is  placed  to 
evaporate  over  a  surface  of  oil  of  vitriol  in  the  vacuum  of  the 
air-pump.  Tannic  acid,  or  tannin,  thus  obtained,  forms  a 
slightly  yellowish,  friable,  porous  mass,  without  the  slightest 
tendency  to  crystallization.  It  is  very  soluble  in  water,  less 
so  in  alcohol,  and  very  slightly  soluble  in  ether.  It  reddens 
litmus  and  possesses  a  pure  astringent  taste  without  bitter- 
ness. 

A  strong  solution  of  this  substance  mixed  with  mineral 
acids  gives  rise  to  precipitates,  which  consist  of  combinations 
of  the  tannic  acid  with  the  acids  in  question :  the  compounds 
are  freely  soluble  in  pure  water,  but  nearly  insoluble  in  acid 
liquids.  Gallotannic  acid  precipitates  albumin,  gelatin,  salts 
of  the  vegeto-alkalies,  and  several  other  substances  :  it  forms 
soluble  compounds  with  the  alkalies,  which,  if  excess  of  base 
be  present,  rapidly  attract  oxygen,  and  become  brown  by  de- 
struction of  the  acid  ;  the  gallotannates  of  barium,  strontium,  and  calcium  are 
sparingly  soluble  ;  those  of  lead  and  antimony  are  insoluble.  Ferrous  salts 
are  unchanged  by  solution  of  gallo-tannic  acid  ;  ferric  salts,  on  the  contrary, 
give  with  it  a  deep  bluish-black  precipitate,  which  is  the  basis  of  writing- 
ink  :  hence  the  value  of  an  infusion  of  tincture  of  nut-galls  as  a  test  for  the 
presence  of  that  metal. 

Gallotannic  acid,  when  boiled  with  acids,  assimilates  water,  and  splits 
into  "glucose  and  gallic  acid: 

C27H220T7    4-     4H.O    =    3C7IV)3    +     C6H1206 
Gallotaunic  Gallic  Glucose, 

acid,  acid. 


TARTARIC   ACID.  673 

The  same  reaction  takes  place  on  heating  tannic  acid  with  a  concentrated 
solution  of  potash :  in  this  case,  however,  the  sugar  is  further  converted 
into  glucic  acid.  Nut-galls  contain  a  ferment  which  induces  the  same  de- 
composition of  tannic  acid,  exciting,  at  the  same  time,  alcoholic  fermenta- 
tion of  the  sugar.  Gallotannic  acid,  prepared  by  the  methods  above  men- 
tioned, still  contains  a  sufficient  quantity  of  the  ferment  to  produce  this 
decomposition  when  the  acid  is  dissolved  in  water,  and  at  the  ordinary 
temperature:  it  ensues,  however,  much  more  rapidly  on  addition  of  nut- 
galls.  If  this  fermentation  takes  place  in  the  presence  of  air,  a  part  of  the 
tannic  acid  is  converted  into  ellagic  acid,  C14H608.  The  same  substance  is 
found  in  the  insoluble  residue  of  woody  fibre  and  other  matters  from  which 
gallic  acid  has  been  withdrawn  by  boiling  water  ;  it  may  be  extracted  by 
an  alkali,  and  afterward  precipitated  by  addition  of  hydrochloric  acid,  as 
a  grayish  insoluble  powder. 

Tannic  acid,  closely  resembling  that  obtained  from  galls,  may  be  ex- 
tracted by  cold  water  from  catechu ;  hot  water  dissolves  out  a  substance 
having  feebly  acid  properties,  termed  catechin.  This  latter  compound, 
when  pure,  crystallizes  iti  fine  colorless  needles,  which  melt  when  heated, 
and  dissolve  very  freely  in  boiling  water,  but  scarcely  at  all  in  the  cold. 
Catechin  dissolves  also  in  hot  alcohol  and  ether.  The  aqueous  solution 
acquires  a  red  tint  by  exposure  to  air,  and  precipitates  lead  acetate  and 
corrosive  sublimate  white,  reduces  silver  nitrate  on  addition  of  ammonia, 
but  does  not  form  insoluble  compounds  with  gelatin,  starch,  and  the  vegeto- 
alkalies.  It  strikes  a  deep  green  color  with  ferric  salts.  Catechin  when 
heated  yields  pyrocatechin,  or  oxyphenol,  C6H602  (p.  562).  Catechin  has 
been  variously  represented  by  the  formulae  C9H,pO4,  and  C8H804. 

Japonic  and  Rubic  acids  are  formed  by  the  action  of  alkali  in  excess  upon 
catechin,  the  first  when  the  alkali  is  in  the  caustic  state,  and  the  second 
when  it  is  in  the  state  of  carbonate.  Japonic  acid  is  a  black  and  nearly 
insoluble  substance,  soluble  in  alkalies  and  precipitated  by  acids ;  it  is 
perhaps  identical  with  a  black  substance  of  acid  properties,  which  Peligot 
obtained  by  heating  grape-sugar  with  barium  hydrate.  Rubic  acid  has 
been  but  little  studied:  it  is  said  to  form  red  insoluble  compounds  with  the 
earths  and  certain  other  metallic  oxides. 

Several  acids  closely  allied  to  tannic  acid  have  been  found  in  coffee  and 
Paraguay  tea. 

Opianic  Acid,  C,0H1?06,  is  a  monobasic  acid,  produced,  together  with  co- 
tarnine,  by  the  oxidation  of  narcotine  : 

C22H23NOT     +     0     =     CJ2H13N03    +     C10H1006 
JNarcotme.  Cotarnine.         Opianic  acid. 

It  crystallizes  in  thin  prisms,  slightly  soluble  in  cold,  easily  in  boiling 
water;  also  in  alcohol  and  ether,  melts  at  140°  C.  (284°  F.).  Caustic  pot- 
ash converts  it  into  meconin  and  hemipinic  acid : 

2C1QH100          =        C10H100«        +        010H1006 
Upianic  acid.  Meconiu.  Hemipinic  acid. 


TETRATOMIC  AND  BIBASIC  ACIDS. 


Tartaric    Acid,    C4H606    =    (C4H202)    (OH)4    =r   (C2H2 

These  formulae  include  four  bibasic  acids  distinguished  from  one  another 
by  certain  physical  properties,  especially  by  their  crystalline  forms,  and 
57 


674  TETEATOMIC   AND   BIBASIC   ACIDS. 

their  action  on  polarized  light, —  namely,  Dextrotartaric  acid,  which  turns 
the  plane  of  polarization  to  the  right ;  Levotartaric  acid,  which  turns  it  to  the 
left  with  equal  force  ;  Paratarlaric,  or  Racemic  acid,  which  is  optically  inac- 
tive, and  separable  into  equal  quantities  of  dextro-  and  levotartaric  acids; 
and  an  inactive  variety  of  tartaric  acid,  which  is  not  thus  separable. 

DEXTROTARTARIC  OR  ORDINARY  TARTARIC  ACID.  —  This  is  the  acid  of 
grapes,  tamarinds,  pine  apples,  and  of  several  other  fruits,  in  which  it  oc- 
curs in  the  state  of  an  acid  potassium-salt ;  calcium  tartrate  is  also  occa- 
sionally met  with.  The  tartaric  acid  of  commerce  is  wholly  prepared  from 
tartar  or  argol,  an  impure  acid  potassium  tartrate,  deposited  from  wine,  or 
rather  from  grape-juice  in  the  act  of  fermentation.  This  substance  is  pu- 
rified by  solution  in  hot  water,  with  the  aid  of  a  little  pipe-clay  and  ani- 
mal charcoal,  to  remove  the  coloring  matter  of  the  wine,  and  subsequent 
crystallization :  it  then  constitutes  cream  of  tartar,  and  serves  for  the  pre- 
paration of  the  acid.  The  salt  is  dissolved  in  boiling  water,  and  powdered 
chalk  is  added  as  long  as  effervescence  is  excited,  or  the  liquid  exhibits  an 
acid  reaction:  calcium  tartrate  and  neutral  potassium  tartrate  result;  the 
latter  is  separated  from  the  former,  which  is  insoluble  by  filtration.  The 
solution  of  potassium  tartrate  is  then  mixed  with  excess  of  calcium  chlo- 
ride, which  throws  down  all  the  remaining  acid  in  the  form  of  calcium- 
salt:  this  is  washed,  and  added  to  the  former  portion,  and  the  whole  is 
digested  with  a  sufficient  quantity  of  dilute  sulphuric  acid  to  withdraw  the 
base,  and  liberate  the  tartaric  acid.  The  filtered  solution  is  cautiously 
evaporated  to  a  syrupy  consistence,  and  placed  to  crystallize  in  a  warm 
situation.  Liebig  has  lately  found  that  tartaric  acid  is  artificially  pro- 
duced by  the  action  of  nitric  acid  upon  milk-sugar.  It  may  also  be  ob- 
tained from  succinic  acid. 

Succinic  acid,  C4H604,  when  submitted  to  the  action  of  bromine,  yields 
two  substitution-products,  bromosuccinic  acid,  C4HgBr04,  and  dibromosuc- 
cinic  acid,  C4H4Br204.  The  latter,  when  treated  with  silver  oxide  in  pres- 
ence of  water,  is  converted  into  tartaric  acid  and  silver  bromide,  C4H4Br2 
04  -f  Ag?0  -f  H20  =  C4H606  -j-  2AgBr  (Perkin  and  Duppa;-Kekul6). 

Tartaric  acid  forms  colorless,  transparent  crystals,  often  of  large  size, 
which  have  the  figure  of  an  oblique  rhombic  prism  more  or  less  modified ; 
they  are  permanent  in  the  air,  and  inodorous ;  they  dissolve  with  great 
facility  in  water,  both  hot  and  cold,  and  are  soluble  also  in  alcohol.  The 
solution  reddens  litmus  strongly,  and  has  a  pure  acid  taste.  The  aqueous 
solution,  as  above  mentioned,  exhibits  right-handed  polarization.  This 
solution  is  gradually  spoiled  by  keeping.  Tartaric  acid  is  consumed  in 
large  quantities  by  the  calico-printer,  being  employed  to  evolve  chlorine 
from  solution  of  bleaching-powder  in  the  production  of  white  or  discharged 
patterns  upon  a  colored  ground. 

Tartrates. — Tartaric  acid  is  tetratomic  and  bibasic,  two  only  of  its  hy- 
drogen-atoms being  replaceable  by  metals,  the  other  two  by  alcoholic  or 
acid  radicals.  With  monad  metals  it  forms  acid  and  neutral  salts,  C4H5M/ 
06,  and  C4H4M206;  with  dyad  metals,  neutral  salts,  C4H4M"O6,  and  double 
salts,  like  bario-potassic  tartrate,  C4H4Ba/x06 .  C4H4K206.  With  triad  metals 
it  forms  a  peculiar  class  of  salts,  best  known  in  the  case  of  the  antimony- 
salt  (p.  675). 

POTASSIUM  TARTRATES. — The  neutral  salt,  C4H4K206,  maybe  procured  by 
neutralizing  cream  of  tartar  with  chalk,  as  in  the  preparation  of  the  acid, 
or  by  adding  potassium  carbonate  to  cream  of  tartar  to  saturation ;  it  is 
very  soluble,  and  crystallizes  with  difficulty  in  right  rhombic  prisms,  which 
are  permanent  in  the  air,  and  have  a  bitter,  saline  taste.  The  acid  salt,  or 
cream  of  tartar,  C4II6K06,  the  prigin  and  preparation  of  which  have  been 


or 
sen 


TARTARIC    ACID.  G75 

already  described,  forms  small  transparent,  or  translucent  prismatic  crystals 
irregularly  grouped  together,  which  grate  between  the  teeth.  It  dis- 
solves pretty  freely  in  boiling  water,  but  the  greater  part  separates  as  the 
solution  cools,  leaving  about  ^  or  less  dissolved  in  the  cold  liquid.  The 
salt  has  an  acid  reaction  and  a  •  sour  taste.  When  exposed  to  heat  in  a 
close  vessel,  it  is  decomposed,  with  evolution  of  inflammable  gas,  leaving  a 
mixture  of  finely  divided  charcoal  and  pure  potassium  carbonate  (black 
flux),  from  which  the  latter  may  be  extracted  by  water.  Cream  of  tartar  is 
almost  always  produced  when  tartaric  acid  in  excess  is  added  to  a  moder- 
ately strong  solution  of  a  potassium-salt,  and  the  whole  agitated. 

SODIUM  TARTRATES. — Two  of  these  salts  are  known  —  a  neutral  sail, 
C4H4Na206  .  2  Aq. ;  and  an  acid  salt,  C4H5Na06  .  Aq.  Both  are  easily  soluble 
in  water,  and  crystallizable.  Tartaric  acid  and  sodium  bicarbonate  form 
the  ordinary  effervescing  draughts. 

Potassium  and  sodium  tartrate  ;  Rochelle  or  Seignette  salt,  C4H4KNa06  .  4  Aq. 
This  beautiful  salt  is  made  by  neutralizing  with  sodium  carbonate  a  hot  so- 
lution of  cream  of  tartar,  and  evaporating  to  the  consistence  of  thin  syrup. 
It  separates  in  large,  transparent,  prismatic  crystals,  the  faces  of  which 
are  unequally  developed  :  these  effloresce  slightly  in  the  air.  and  dissolve 
in  1£  parts  of  cold  water.  Acids  precipitate  cream  of  tartar  from  the  so- 
lution. Rochelle  salt  has  a  mild  saline  taste,  and  is  used  as  a  purgative. 

AMMONIUM  TARTRATES.  —  The  neutral  tartrate  is  a  soluble  and  efflorescent 
salt,  containing  C4H4(NH4)206.  Aq.  The  acid  tartrate,  C4H5(NH4)06,  closely 
resembles  ordinary  cream  of  tartar.  A  salt  corresponding  to  Rochelle  salt 
also  exists,  having  ammonium  in  place  of  sodium. 

The  tartrates  of  calcium,  barium,  strontium,  magnesium,  and  of  most  of  the 
heavy  metals,  are  insoluble,  or  nearly  so,  in  water. 

POTASSIO-ANTIMONIOUS  TARTRATE,  or  tartar  emetic,  is  easily  made  by  boil- 
ing antimony  trioxide  in  solution  of  cream  of  tartar:  it  is  deposited  from 
a  hot  and  concentrated  solution  in  crystals  derived  from  an  octohedron 
with  rhombic  base,  which  dissolve  without  decomposition  in  15  parts  of 
cold  and  3  of  boiling  water,  and  have  an  acrid  and  extremely  disagreeable 
metallic  taste.  The  solution  is  decomposed  by  both  acids  and  alkalies:  the 
former  throws  down  a  mixture  of  cream  of  tartar  and  antimony  trioxide, 
and  the  latter  the  trioxide,  which  is  again  dissolved  by  great  excess  of  the 
reagent.  Sulphuretted  hydrogen  separates  all  the  antimony  in  the  state 
of  trisulphide.  The  dry  salt  heated  on  charcoal  before  the  blowpipe,  yields 
a  globule  of  metallic  antimony.  The  crystals  contain  2C4H4K(SbO)06 .  Aq., 
the  group  SbO  acting  as  aunivalent  radical,  and  replacing  one  atom  of  hy- 
drogen. When  dried  at  100°,  they  give  off  their  water  of  crystallization,  and 
at  200°  C.(392°  F.),  an  additional  molecule  of  water,  leaving  the  compound 
C4H2K(SbO)05,  which  has  the  constitution  of  a  salt,  not  of  tartaric,  but  of 
tartrelic  acid,  C4H40-  Nevertheless,  when  dissolved  in  water,  the  crystals 
again  take  up  the  elements  of  water,  and  reproduce  the  original  salt. 

An  analogous  compound,  containing  arsenic  in  place  of  antimony,  has 
been  described.  It  has  the  same  crystalline  form  as  tartar  emetic. 

A  solution  of  tartaric  acid  dissolves  ferric  hydrate  in  large  quantity, 
forming  a  brown  liquid,  which  has  an  acid  reaction,  and  dries  up  by  gentle 
heat  to  a  brown,  transparent,  glassy  substance,  destitute  of  all  traces  of 
crystallization.  It  is  very  soluble  in  water,  and  the  solution  is  not  preci- 
pitated by  alkalies,  either  fixed  or  volatile.  Indeed,  tartaric  acid,  added  in 
sufficient  quantity  to  a  solution  of  ferric  oxide,  or  alumina,  entirely  pre- 
vents the  precipitation  of  the  bases  by  excess  of  ammonia.  Tartrate  and 
ammoniacal  tartrate  of  iron  are  used  in  medicine,  these  compounds  having 
a  less  disagreeable  taste  than  most  of  the  iron  preparations. 


676  TETRATOMIC    AND    BTBASIC    ACIDS. 

Solutions  of  tartaric  acid  give  with  lime  and  baryta-water,  and  with  lead 
acetate,  white  precipitates,  which  dissolve  in  excess  of  the  acid  ;  with  neu- 
tral calcium  and  barium-salts  no  change  is  produced.  Silver  nitrate  pro- 
duces in  neutral  tartrates  a  white  precipitate  of  silver  tartrate,  which  dis- 
solves in  ammonia.  On  gently  heating  the  solution,  a  bright  metallic  de- 
posit of  silver  is  formed.  The  reaction  of  tartaric  acid  with  solutions  of 
potassium-salts  has  been  already  noticed  (p.  299). 

Tartaric  Ethers.  —  1.  Tartaric  acid  forms,  with  monatomic  alcohol-radi- 
cals, acid  and  neutral  ethers,  in  which  one  or  both  of  the  atoms  of  basic  hy- 
drogen in  its  molecule  is  replaced  by  an  alcohol-radical.  These  compounds 
may  be  conveniently  formulated  as  follows  : 


Tartaric  acid.  Acid  ethyl  tartrate.     Neutral  ethyl  tartrate. 

The  acid  ethers  are  monobasic  acids,  formed  by  the  direct  action  of  tar- 
taric acid  on  the  respective  alcohols  ;  the  neutral  ethers  are  formed  by 
passing  hydrochloric  acid  gas  into  a  solution  of  tartaric  acid  in  an  alcohol. 
Further,  by  treating  these  neutral  ethers  with  chlorides  of  acid  radicals, 
other  neutral  ethers  are  formed,  in  which  one  or  more  of  the  alcoholic  hy- 
drogen-atoms are  replaced  by  acid  radicals.*  In  this  manner  are  formed 
such  compounds  as  the  following: 


COR  (OC2H30       ,rHVv2 

(C2H2H  OC2H30  (C2H2H  OC7H60       &O     J  (02C4H402)" 

1  (C02C32H6)2  1  (C(52C2H5)2  (<W»  1  (C02C2H5)2; 

Ethyl  aceto-tartrate.         Ethyl  aceto-berizo-          Ethyl  succino- 

tartrate.  tartrate. 

The  alcoholic  hydrogen  in  these  neutral  ethers  may  be  replaced  by  potas- 
sium and  sodium. 

2.  There  are  also  bibasic  tartaric  ethers  formed  by  replacing  the  alcoholic 
hydrogen  of  tartaric  acid  with  acid  radicals  ;  e.  g.  : 


Benzotartaric  Diacetotartaric  Dinitrotartaric 

acid.  acid.  acid. 

3.  Lastly,  tartaric  acid  forms  ethers  with  glycol,  glycerin,  mannite,  glu- 
cose, arid  other  polyatomic  alcohols. 

Action  of  heat  on  Tartaric  Acid.  —  When  crystallized  tartaric  acid  is  ex- 
posed to  a  temperature  of  about  204°  C.  (899°  F.),  it  melts,  loses  water,  and 
yields  in  succession  three  different  anhydrides,  viz.  : 

Ditartaric  or  Tartralic  acid  .         .         C8H10On  =  2C4H606  —  H20 
Tartrelic  acid    .         .         .         .          \  P  TT  n  nun  wn 

Insoluble  tartaric  anhydride         .      /  L4H4us    :  :  ^4H6U6    -     W2U 

The  first  two  are  soluble  in  water,  and  form  salts  which  have  properties 
completely  different  from  those  of  ordinary  tartaric  acid.  The  third  is  a 
white  insoluble  powder.  All  three,  in  contact  with  water,  slowly  pass  into 
ordinary  tartaric  acid. 

Tartaric  acid,  subjected  to  destructive  distillation,  is  resolved  into  car- 
bon dioxide  and  pyrotartaric  acid,  €3II604. 

When  tartaric  acid  is  heated  to  204-5°  C.  (400°  F.),  with  excess  of  potas- 

*  Perkin,  Chem.  Soc.  Jour.  [2],  v.  139. 


PARATARTARIC    OR    RACEMIC   ACID.  677 

sium  hydrate,  it  is  resolved,  without  charring  or  secondary  decomposition, 
into  oxalic  and  acetic  acids,  which  remain  in  union  with  the  base,  and  only 
undergo  decomposition  at  a  much  higher  temperature: 

C4H606     -f     2KHO     ='    C2KH04     -f     C2H3K02     +     20H2 
Tartaric  Acid  potas-         Potassium 

acid.  sium  oxalate.          acetate. 

PARATARTARIC  OR  RACEMIC  ACID. — The  grapes  cultivated  in  certain  dis- 
tricts of  the  Upper  Rhine,  and  also  in  the  Vosges,  contain,  in  association 
with  tartaric  acid,  another  acid  body  to  which  the  above  names  are  given. 
This  acid  is  rather  less  soluble  than  tartaric  acid,  and  separates  first  from 
the  solution  of  that  substance.  Between  these  two  acids,  however,  a  very 
great  resemblance  exists;  they  have  exactly  the  same  composition,  and 
ybll,  when  exposed  to  heat,  the  same  products;  the  salts  of  racemic  acid 
correspond  also,  in  the  closest  manner,  with  the  tartrates.  A  solution  of 
racemic  acid,  however,  precipitates  a  neutral  calcium-salt,  which  is  not  the 
case  with  tartaric  acid.  A  solution  of  racemic  acid  does  not  rotate  the 
plane  of  polarization. 

Racemic  acid  has  been  the  subject  of  some  exceedingly  interesting  re- 
searches by  M.  Pasteur,  which  have  thrown  much  light  upon  the  relation 
of  this  acid  to  tartaric  acid.  If  racemic  acid  be  saturated  with  potash,  or 
so  la,  or  with  most  other  bases,  crystals  are  obtained,  which  are  identical 
in  form  and  physical  properties.  By  saturating  racemic  acid,  however, 
with  two  bases,  by  forming,  for  instance,  compounds  corresponding  to 
Rochelle  salt,  which  contain  potassium  and  sodium,  or  ammonium  and  so- 
dium, and  allowing  the  solution  to  crystallize  slowly,  two  varieties  of  crys- 
tals are  produced,  which  may  be  distinguished  by  their  form,  each  of  them 
containing  hemihedral  faces  (p.  263),  equal  in  number  and  exactly  similar 
in  form,  but  developed  on  opposite  sides  of  the  two  crystals,  so  that  each 
of  them  may  be  regarded  as  the  reflected  image  of  the  other,  or  as  right- 
handed  and  left-handed.  If  the  two  kinds  of  crystals  are  carefully 
selected  and  separately  crystallized,  crystals  of  the  one  variety  only  are 
deposited  in  each  case.  The  composition,  the  specific  gravity,  and,  in 
fact,  most  of  the  physical  properties  of  these  two  varieties  of  sodio-potas- 
sic  racamate,  are  invariably  the  same  They  differ,  however,  somewhat  in 
their  ciiemical  characters,  and  especially  in  one  point:  they  rotate  the 
plane  of  polarization  in  opposite  directions.  Pasteur  assumes,  in  the  two 
varieties  of  crystals,  the  existence  of  two  modifications  of  the  same  acid, 
which  he  distinguishes,  according  as  the  salt  possesses  right- or  left-handed 
polarization,  by  the  terms  dextro -racemic  and  levo-raccmic,  or  dextro-  and 
levo-tartaric  acids.  These  acids  may  be  separated  by  converting  the  above 
compounds  into  lead-  or  barium-salts,  and  decomposing  them  by  means  of 
sulphuric  acid.  In  this  manner  two  crystalline  acids  are  obtained,  identi- 
cal in  every  respect,  excepting  in  their  deportment  with  polarized  light, 
and  in  their  crystals  being  related  to  each  other  in  the  manner  above  men- 
tioned. Dextrotartaric  acid  is  nothing  but  common  tartaric  acid.  A  mix- 
ture of  equal  parts  of  the  two  acids  has  no  longer  the  slightest  effect  on 
polarized  light,  and  exhibits  in  every  respect  the  deportment  of  racemic 
acid. 

Pasteur,  in  continuing  his  beautiful  researches,  has  also  made  the  impor- 
tant discovery  that  racemic  acid  may  be  artificially  produced  by  the  action 
of  heat  upon  certain  compounds  of  tartaric  acid  which  are  capable  of  re- 
sisting a  high  temperature.  When  tart  rate  of  cinchonine*  or  tartaric 
ether,  is  exposed  to  a  temperature  of  about  170°  C.  (338°  F.),  and  the  product 
thus  formed  is  repeatedly  boiled  with  water,  a  solution  is  obtained,  which, 
when  mixed,  after  cooling,  with  an  excess  of  calcium  chloride,  yields  a  con- 

*  See  the  chapter  on  Organic  Bases. 


678  TETRATOMIC   AND   TRIBASIC    ACIDS. 

siderable  precipitate  of  calcium  racemate.  Compounds  of  levotartaric  acid, 
when  submitted  to  the  action  of  heat,  likewise  furnish  racemic  acid.  The 
formation  of  racemic  acid  in  these  reactions  is  accompanied  by  the  pro- 
duction of  a  fourth  modification  of  tartaric  acid,  which  Pasteur  calls  inac- 
tive tartaric  acid.  Like  racemic  acid,  it  has  no  action  on  polarized  light, 
but  cannot,  like  the  latter,  be  resolved  into  levo-  and  dextrotartaric  acid. 

Rhodizonic  Acid,  C5H406. — When  potassium  is  heated  in  a  stream  of  dry 
carbon  monoxide,  the  latter  is  absorbed  in  large  quantity,  and  a  black  por- 
ous substance  generated,  which,  according  to  Brodie,  contains  COK3. 
Brought  in  contact  with  water,  it  decomposes  with  great  violence,  and 
even  the  dry  substance  occasionally  explodes;  when  anhydrous  alcohol  is 
poured  upon  it,  a  great  elevation  of  temperature  ensues,  but  the  decompo- 
sition is  far  less  violent  than  with  water.  The  product  of  this  reaction  is 
potassium  rhodizonate,  which  remains  as  a  red  powder,  insoluble  in  alco- 
hol, but  soluble  in  water  with  a  deep  red  color.  This  salt  probably  con- 
tains C5H2K206. 

When  solution  of  potassium  rhodizonate  is  boiled,  it  becomes  orange-yel- 
low from  decomposition  of  the  acid,  and  is  then  found  to  contain  a  free 
potash,  and  a  salt  of  Croconic  acid,  C5H205.  This  acid  can  be  isolated  :  it 
is  yellow,  easily  crystallizable,  soluble  both  in  water  and  alcohol.  It  is 
likewise  bibasic. 


TETRATOMIC  AND  TRIBASIC  ACIDS. 

Citric  Acid,  C6H8Or — This  acid  is  obtained  in  large  quantities  from  the 
juice  of  lemons :  it  is  found  in  many  other  fruits,  as  in  gooseberries,  cur- 
rants, &c.,  in  conjunction  with  malic  acid.  In  the  preparation  of  this  acid, 
the  juice  is  allowed  to  ferment  a  short  time,  in  order  that  mucilage  and 
other  impurities  may  separate  and  subside:  the  clear  liquor  is  then  care- 
fully saturated  with  chalk,  whereby  insoluble  calcium  citrate  is  produced. 
This  is  thoroughly  washed,  decomposed  by  the  proper  quantity  of  sulphu- 
ric acid,  diluted  with  water,  and  the  filtered  solution  is  evaporated  to  a 
small  bulk,  arid  left  to  crystallize.  The  product  is  drained  from  the 
mother-liquor,  redissolved,  digested  with  animal  charcoal,  and  again  con- 
centrated to  the  crystallizing  point. 

Citric  acid  crystallizes  in  two  different  forms.  The  crystals  which  sepa- 
rate by  spontaneous  evaporation  from  &  cold  saturated  solution,  are  tri- 
metric  prisms,  containing  C6H807.  OH2,  whereas  those  which  are  deposited 
from  a  hot  solution  have  a  different  form  and  contain  2C6H807.  OH2. — Ci- 
tric acid  has  a  pure  and  agreeable  acid  taste,  and  dissolves,  with  great  ease, 
in  both  hot  and  cold  water ;  the  solution  strongly  reddens  litmus,  and, 
when  long  kept,  is  subject  to  spontaneous  change.  Citric  acid,  when 
brought  in  contact  with  putrid  flesh  as  a  ferment,  yields  butyric  acid  and 
small  quantities  of  succinic  acid,  it  is  entirely  decomposed  when  heated 
with  sulphuric  and  nitric  acids  :  the  latter  converts  it  into  oxalic  acid. 
Caustic  potash,  at  a  high  temperature,  resolves  it  into  acetic  and  oxalic 
acids.  The  alkaline  citrates,  treated  with  chlorine,  yield  chloroform,  to- 
gether with  other  products. 

Citric  acid  is  tetratomic  and  tribasic,  and  may  be  represented  by  the 

rnw  riv  f  CILOII 

formula   (C3H4)^  /*  or  xJ  II,  .     It  has    not   yet    been    ob- 

uiW»          '    l(C02H)3 
tained  by  any  synthetical  process.     With  potassium  it  forms  a  neutral  salt 


MECONIC   ACID.  679 

containing  C6H5K307,  and  two  acid  salts  containing  respectively  C6H6K207 
andC6H7K07;  and  similar  salts  with  the  other  alkali-metals.  With  dyad 
metals  it  chiefly  forms  salts  in  which  §,.  >-"-<  L»»,  tjiree  hydrogen-atoms  in  the 
molecule  C6H807,  are  replaced  by  metals;  \vn,-'  .ir;///'//  ••>:.  for  example,  it 
forms  the  salts  U6lI6C\i//0,, .  Aq.,  and  (C6H50.)2Ca//3 .  A 4.  A\  .,',7  !•••;>/  it.  form«w 
two  salts  similar  in  constitution  to  the  calcium-salts,  and  likewise  a  tetra- 
plumbic  salt  containing  (C6H607)2Pb"s.  Pb"H2Oa. 

The  citrates  of  the  alkali-metals  are  soluble  and  crystallize  with  greater 
or  less  facility ;  those  of  barium,  strontium,  calcium,  lead,  and  silver  are  in- 
soluble. 

Citric  acid  resembles  tartaric  acid  in  its  relations  to  ferric  oxide,  pre- 
venting the  precipitation  of  that  substance  by  excess  of  ammonia.  The 
citrate  obtained  by  dissolving  hydratcd  ferric  oxide  in  solution  of  citric 
acid,  dries  up  to  a  pale-brown,  transparent,  amorphous  mass,  which  is  not 
very  soluble  in  water ;  an  addition  of  ammonia  increases  the  solubility. 
Citrate  and  ammonia-citrate  of  iron  are  elegant  medicinal  preparations. 
Very  little  is  known  respecting  the  composition  of  these  curious  com- 
pounds :  the  absence  of  crystallization  is  a  great  bar  to  exact  inquiry. 

Citric  acid  is  sometimes  adulterated  with  tartaric  acid:  the  fraud  is 
easily  detected  by  dissolving  the  acid  in  a  little  cold  water,  and  adding  to 
the  solution  a  small  quantity  of  potassium  acetate.  If  tartaric  acid  be 
present,  a  white  crystalline  precipitate  of  cream  of  tartar  will  be  produced 
on  agitation. 

Citric  acid  forms  ethers  in  which  1,  2,  or  3  hydrogen-atoms  are  replaced 
by  methyl  and  other  monad  alcohol-radicals. 

Meconic  Acid,  C7H407,  a  tribasic  acid  existing  in  opium,  may  also  be  de- 
scribed here.  To  prepare  it,  the  liquid  obtained  by  exhausting  opium 
with  water,  is  neutralized  with  powdered  marble  and  precipitated  by 
calcium  chloride ;  and  the  calcium  meconate  thus  precipitated  is  sus- 
pended in  warm  water  and  treated  with  hydrochloric  acid ;  on  cooling,  im- 
pure meconic  acid  crystallizes,  which  may  be  purified  by  repeated  trer.t- 
ment  with  hydrochloric  acid.  The  pure  acid  crystallizes  in  mica-like 
plates,  easily  soluble  in  boiling,  difficultly  soluble  in  cold  water,  soluble 
likewise  in  alcohol.  The  crystals  contain  C7H407 .  3  Aq.  and  give  off  their 
water  at  100°.  The  meconates  are,  for  the  most  part,  mono-  and  bi-metal- 
lic.  There  are  two  silver  mcconates,  one  yellow,  containing  C7HAg307;  the 
other  white,  consisting  of  C7H2Ag207.  Meconic  acid  produces  a  deep  red 
color  with  ferric  salts. 

COMENIC  ACID,  C6H405,  is  a  product  of  decomposition  of  meconic  acid. 
When  an  aqueous,  or,  better,  a  hydrochloric  solution  of  meconic  acid  is 
boiled,  carbon  dioxide  is  evolved,  and  the  solution  now  contains  cotnenic 
acid,  which  crystallizes  on  cooling,  being  very  difficultly  soluble  in  cold 
water.  The  same  acid  may  be  obtained  by  heating  meconic  acid  to  200°  C. 
(892°  F.).  It  is  bibasic :  its  formation  is  represented  by  the  equation 
C7H407  ^  C6H405  +  C02. 

PYROMECONIC  or  PYROCOMENIC  ACID,  C6H403,  is  a  monobasic  acid,  formed 
by  submitting  either  comenic  or  meconic  acid  to  dry  distillation,  one  mole- 
cule of  carbon  dioxide  being  evolved  in  the  former  case  and  two  in  the 
latter. 

Pyrocomenic  acid  is  a  weak  acid:  it  is  soluble  in  water  and  alcohol: 
from  these  solutions  it  crystallizes  in  long  colorless  needles,  which  melt  at 
120°  C.  (248°  F.),  and  begin  to  sublime  at  the  boiling  point  of  water.  Both 
comenic  and  pyrocomenic  acids  exhibit  the  red  coloration  with  ferric  salts. 

The  salts  of  meconic  acid  and  comenic  acid,  together  with  several  deriva- 


680  PENTATOMIC    ACIDS. 

tives  of  these  substances,  have   been  studied  by  Mr.  How,*  but  our  space 
will  not  permit  us  to  describe  these  compounds. 

An  acid  much  resembling  U^^'^%  acid  has  been  extracted  from  the  Che- 
lidonium  majus :  .JJ^  ;.s   PC^ffmea  with  lime,  and  associated  with  malic  and 

-    funiaric  aci'1.  .  ''''  Cbfendonic  acid  is  tribasic,  forming  three  classes  of  salts. 

1  When  exposed  to  a  high  temperature,  it  yields  a  pyro-acid,  with  evolution 
of  water  and  carbon  dioxide.  It  crystallizes  in  slender  colorless  easily  sol- 
uble needles,  containing  C?H405 .  Aq. 


PENTATOMIC  ACIDS. 

There  is  but  one  known  acid  that  can  be  referred  to  this  group,  namely : 

Quinic  or  Kinic  Acid,  C7H1206,  which  is  monobasic,  and  may  perhaps  be 

represented  by  the  formula  (C6H7)T  -|  \Q  A4. — The  calcium-salt  of  this  acid 

is  found  in  the  solution  from  which  the  alkalies  of  cinchona  bark  have  been 
separated  by  lime,  and  is  easily  obtained  by  evaporation,  and  purified  by 
animal  charcoal.  From  the  calcium-salt  the  acid  may  be  extracted  by  de- 
composing it  with  dilute  sulphuric  acid.  The  clear  solution  evaporated  to 
a  syrupy  consistence  deposits  large,  distinct  crystals,  resembling  those  of 
tartaric  acid,  and  soluble  in  2  parts  of  water.  Quinic  acid  has  also  been 
found  in  coffee-berries  and  in  the  leaves  of  the  bilberry-bush. 

When  quinic  acid  is  heated  with  a  mixture  of  sulphuric  acid  and  manga- 
nese dioxide,  it  yields  a  very  volatile  substance  termed  quinone,  the  vapor 
of  which  is  exceedingly  irritating  to  the  eyes.  This  body  forms  crystals, 
both  by  sublimation  and  by  solution  in  boiling  water:  it  melts  at  a  gentle 
heat,  crystallizes  on  cooling,  colors  the  skin  permanently  brown.  It  con- 
tains C6H402,  and  its  formation  is  represented  by  the  equation: 

C7H1206     +     02    :   :     C6II402     4-     C02     +     4II20. 

By  destructive  distillation,  quinic  acid  yields  numerous  arid  interesting 
products,  which  have  been  studied  by  Wohler,  as  benzoic  acid,  phenol,  sa- 
licylol,  benzene,  a  tarry  substance  not  examined,  and  colorless  hydroquinone, 
C6II602,  containing  2  atoms  of  hydrogen  more  than  quinone.  This  sub- 
stance forms  colorless  six-sided  prismatic  crystals  ;  it  is  neutral,  destitute 
of  taste  and  odor,  fusible,  and  easily  soluble  both  in  water  and  in  alcohol. 

Colorless  hydroquinone  can  be  easily  and  directly  produced  from  qui- 
none by  assimilation  of  hydrogen,  as  by  addition  of  hydriodic  acid  to  a  so- 
lution of  the  latter,  iodine  being  then  set  free,  or  by  sulphurous  acid. 

An  intermediate  product  of  reduction  is  green  hydroquinone,  or  quinhy- 
drone,  CI2H1004.  This  is  obtained  by  the  incomplete  action  of  sulphurous 
acid  upon  quinone,  or  by  the  action  of  ferric  chloride,  chlorine,  silver  ni- 
trate, or  chromic  acid,  upon  colorless  hydroquinone  ;  or  by  mixing  together 
solutions  of  quinone  and  colorless  hydroquinone.  It  forms  slender  green 
crystals,  having  the  color  of  the  wing-case  of  the  rose-beetle,  and  of  the 
greatest  brilliancy  and  beauty.  It  is  fusible,  has  but  little  odor,  and  dis- 
solves freely  in  boiling  water,  crystallizing  out  on  cooling. 

If  quinic  acid  be  submitted  to  distillation  with  an  ordinary  chlorine-mix- 
ture, an  acid  liquid  and  a  crystalline  sublimate  are  formed.  The  former 
is  a  solution  of  formic  acid,  and  the  latter  a  mixture  of  four  chlorinetted 
compounds,  which  are  chloroquinone,  C6H3C102,  dichloroquinone,  C6II2C1202, 
trichloroquinone,  C6IIC1302,  and  tetrachloroquinone,  C6C1402.  They  are  all 

*  Chem.  Soc.  Quar.  Journal,  iv.  363. 


HEXATOMIC   ACIDS.  681 

yellow  crystalline  substances,  which  can  be  separated  only  with  great  diffi- 
culty. Like  quinone  itself,  they  poss£ve  e'^g  faculty  of  combining  with  1  or 
2  atoms  of  hydrogen,  producing  two  series  &  M/  .fyces  analogous  to  green 
and  colorless  hydroquinone.  Telrachloroquinone,  ''ueTM5F  known  by  the 
name  chloranil,  likewise  occurs  among  the  products  of  de^*oi>'A2osiii'^Q  ~&£, 
indigo. 

Other  products  are  obtained  by  the  action  of  sulphuretted  hydrogen  and 
strong  hydrochloric  acid  upon  quinone. 


HEXATOMIC  ACIDS. 

Three  acids  of  this  class  are  known ;  namely,  mannitic,  saccharic,  and 
mucic  acids,,  all  of  which  appear  to  be  bibasic. 

Mannitic  Acid,  C6H,207,  is  produced  by  oxidation  of  mannite,  C6H,406, 
under  the  influence  of  platinum  black.  It  is  a  gummy  mass,  soluble  in 
water  and  in  alcohol,  insoluble  in  ether.  According  to  its  constitution 
(p.  573)  it  might  be  expected  to  be  monobasic,  but  from  the  observations 
of  Gorup-Besanez,  who  discovered  it,*  it  appears  to  be  bibasic,  its  potas- 
sium-salt containing  C6H10K207,  and  the  calcium-salt,  C6H10Ca//Or 

Saccharic  Acid,  C6H1008  =  (C4H4)vi{  [co  H)  •  — This  acid  is  produced 
by  the  action  of  dilute  nitric  acid  on  cane-sugar,  glucose,  milk-sugar,  and 
mannite,  and  is  often  formed  in  the  preparation  of  oxalic  acid,  being,  from 
its  superior  solubility,  found  in  the  mother-liquor  from  which  the  oxalic 
acid  has  crystallized.  It  may  be  made  by  heating  together  1  part  of  sugar, 
2  parts  of  nitric  acid,  and  10  parts  of  water.  When  the  reaction  seems 
terminated,  the  acid  liquid  is  diluted,  neutralized  with  chalk,  and  the  fil- 
tered liquid  is  mixed  with  lead  acetate.  The  insoluble  lead  saccharate  is 
washed,  and  decomposed  by  sulphuretted  hydrogen.  The  acid  slowly  crys- 
tallizes from  a  solution  of  syrupy  consistence  in  long  coloi'less  needles ;  it 
has  a  sour  taste,  and  forms  soluble  salts  with  lime  and  baryta.  When 
mixed  with  silver  nitrate  it  gives  no  precipitate,  but,  on  the  addition  of 
ammonia,  a  white  insoluble  substance  separates,  which  is  reduced  by  gently 
warming  the  whole  to  metallic  silver,  the  vessel  being  lined  with  a  smooth 
and  brilliant  coating  of  the  metal.  Nitric  acid  converts  saccharic  into  oxalic 
acid. 

There  are  two  potassium  saccharates,  containing  C6H9K08  and  C6H8K208; 
the  silver-salt  contains  C6M8Ag208 ;  the  barium,  magnesium,,  zinc,  and  cadmium 
salts  have  the  composition  C6H8\IX/0  ;  and  there  are  two  ethylic  ethers,  contain- 
ing C6H9(C2H5)08  and  C6H8(C2H6)208.  In  these  compounds  saccharic  acid 
appears  to  be  bibasic,  as  might  be  expected  from  its  mode  of  formation 
(p  573) ;  the  composition  of  the  lead-salts,  however,  seems  to  show  that  it 
is  saxbasic  as  well  as  hexatomic,  for  Heintz  has  obtained  a  lead-salt  con- 
taining C6II4Pb//308;  but  the  composition  of  the  lead  saccharates  varies  con- 
siderably according  to  the  manner  in  which  they  are  prepared. 

Mucic  Acid,  C6H,008. — This  acid,  isomeric  with  saccharic  acid,  is  produced, 
together  with  a  small  quantity  of  oxalic  acid,  by  the  action  of  rather  dilute 
nitric  acid  on  sugar  and  gum.  It  may  be  easily  prepared  by  heating  to- 
gether in  a  flask  or  retort,  1  part  of  milk-sugar  or  gum,  4  parts  of  nitric 
acid,  and  1  part  of  water;  the  mucic  acid  is  afterwards  collected  upon  a  filter, 
washed  and  dried.  It  has  a  slightly  sour  taste,  and  reddens  vegetable 

*  Aim.  Ch.  Pharra.  cxviii.  257. 


682  SULPHO-ACIDS. 

colors.  It  requires  for  solution  66  parts  of  boiling  water.  Oil  of  vitriol 
dissolves  it,  with  production  of^escl  color.  Mucic  acid  is  decomposed  by 
heat,  yielding,  among  r^tj^wpfoducts,  pyromucic  acid,  C5H406,  which  is  vola- 
tile, soluble  in  vzSfr^and  crystallizes  in  a  form  resembling  that  of  benzoic 

4d^____^' 

Mucic  acid  is  bibasic,  yielding  for  the  most  part  neutral  salts  containing 
C6H8M208  and  C6H8M//08;  with  the  alkali-metals  it  also  forms  acid  salts, 
such  as  C6H9K08.  There  are  also  mucic  ethers,  containing  one  and  two 
equivalents  of  monad  alcohol-radical. 


SULPHO-ACIDS. 

This  name  is  applied  to  a  group  of  acids  formed  from  hydrocarbons,  al- 
cohols, acids,  and  amides,  by  the  action  of  fuming  sulphuric  acid  or  sul- 
phuric oxide.  They  contain  the  elements  of  a  hydrocarbon,  an  alcohol,  or 
an  acid,  combined  with  one  or  two  molecules  of  sulphuric  oxide,  and  may 
be  regarded  as  derived  from  hydrocarbons,  alcohols,  and  acids  by  substitu- 
tion of  the  univalent  radical,  S03H,  for  hydrogen ;  thus,  sulphacetic  acid, 
C2H4S05,  has  the  composition : 

H2C— S— 0— 0— OH 
C2H402 .  S03,  or  CH2(S03H) .  C02H,  or  I 

0  =  C— OH. 

The  sulphur  in  these  acids  is  in  immediate  combination  with  the  carbon; 
in  this  respect  they  differ  from  sulphuric  ethers  (p.  509),  in  which  the 
sulphur  is  united  with  carbon  only  through  the  medium  of  oxygen. 

SULPHACETIC  ACID  is  produced  by  digesting  glacial  acetic  acid  with  sul- 
phuric oxide  at  60°-75°  C.  (140°-167°  F.)  for  several  days.  The  aqueous 
solution  of  the  mass  saturated  with  barium  or  lead  carbonate  deposits  a 
crystalline  barium  or  lead-salt,  containing  respectively  C2H2Ba/xSOK  .  1  \  Aq. 
and  C2H2Pbx/S05.  From  these  salts  the  acid  may  be  obtained  by  means 
of  sulphuric  or  sulph-hydric  acid.  It  is  bibasic,  since  it  contains  two  equiv- 
alents of  hydroxyl  in  immediate  association  with  oxygen,  one  belonging 
to  the  group  C02H,  the  other  to  the  group  S03H. 

When  sulphacetic  acid  is  subjected  to  the  prolonged  action  of  fuming 
sulphuric  acid,  carbon  dioxide  is  evolved,  and  disu/p hornet holic  or  mcthionic 
acid,  CH4(S03)2,  or  CH2(S03H)2,  is  formed,  which  is  also  bibasic,  and  may  be 
derived  from  methane,  CH4,  by  substitution  of  2S03H  for  H2.  The  product 
diluted  with  water  and  saturated  with  barium  carbonate,  yields  a  beauti- 
fully crystallized,  and  rather  sparingly  soluble  barium-salt,  containing 
CH^OgBa";  from  this  salt  the  acid  may  be  separated  by  sulphuric  acid.  . 

Both  sulphacetic  and  disulphometholic  acids  may  be  produced  by  the 
action  of  fuming  sulphuric  acid  on  acetamide  or  on  acetonitrile,  the  former 
when  the  mixture  is  kept  cool,  the  latter  when  the  temperature  is  allowed 
to  rise,  carbon  dioxide  being  then  given  off;  thus: 

C2H3N     -f     OH2     -f     2S04H2     =     S04H(NH4)  -f     C2H4S05 
Acetonitrile.                         Sulphuric            Acid  am-  Sulphacetic 

acid.  monium  acid, 

sulphate. 

C2II3N     -f     3S04H2     =     S04H(NH4)     -f     CH4S2O6     -f-     C02 
Acetonitrile.  Disulpho- 

metholic acid. 


ALDEHYDES.  683 

With  acetaraide,  C2H3ONH2,  which  differs  from  acetonitrile  only  by  the 
elements  of  water,  the  two  reactions  are  exactly  similar. 

STJLPHOPROPIONIC  ACID,  C2H4(S03H)  .  C02H,  and  DISULPHETHOLIC  Acir>, 
C2H4(S03H)2.  are  prepared  in  the  same  way  from  propionic  acid,  propiona- 
mide,  or  propionitrile. 

SULPHOBENZOIC  ACID,  C6H4(S03H)  .  C02H,  is  produced  by  the  action  of 
sulphuric  oxide  on  benzoic  acid  ;  also,  together  with  disulphobenzolic  acid, 
C6H4(S03H)2,  by  that  of  fuming  sulphuric  acid  on  benzonitrile  or  phenyl 
cyanide,  C7H5N.  Both  are  bibasic.  Sulphobenzolic  acid,  C6H5(S03H),  is  pro- 
duced, together  with  sulphobenzide,  C12H10S02,  by  the  action  of  sulphuric 
oxide  on  benzene.  On  mixing  the  resulting  viscid  liquid  with  a  large  quan- 
tity of  water,  the  sulphobenzide  is  precipitated  as  a  crystalline  powder, 
while  sulphobenzolic  acid  remains  in  solution,  and  may  be  obtained  in  the 
crystalline  form  by  converting  it  into  a  copper-salt,  decomposing  the  latter 
with  sulphuretted  hydrogen,  and  evaporating.  It  is  monobasic,  and  forms 
soluble  salts  with  the  alkali-metals,  barium,  iron,  copper,  and  silver.  By 
the  prolonged  action  of  fuming  sulphuric  acid,  it  is  converted  into  disulpho- 
benzolic acid,  C6H4(S03H)2. 

SULPHONAPHTHALIC    ACID,   C,0H7(S03H),   and    DlSTJLPHONAPHTHALIC  AdD, 

C]0H6(S03H)2,  are  produced  by  melting  naphthalene  with  strong  sulphuric 
acid  or  sulphuric  oxide.  By  neutralizing  the  aqueous  solution  of  the  pro- 
duct with  barium  carbonate,  concentrating,  and  adding  alcohol,  the  disul- 
phonaphthalate  of  barium  is  precipitated,  while  the  sulphonaphthalate  re- 
mains dissolved.  By  using  a  large  excess  of  sulphuric  acid,  and  applying 
a  strong  heat,  nearly  the  whole  of  the  naphthalene  is  converted  into  disul- 
phonaphthalic  acid.  Both  these  acids  are  crystalline,  and  form  soluble  and 
crystallizable  salts;  sulphonaphthalic  acid  is  monobasic;  disulphonaph- 
thalic  acid  bibasic. 

Isethionic  acid,  C2H6S04,  ethionic  acid,  C2H6S207,  and  eihionic  oxide,  or  anhy- 
dride, C2H4S206,  produced,  as  already  mentioned  (pp.  518,  527),  by  the  ac- 
tion of  sulphuric  oxide,  or  fuming  sulphuric  acid,  on  alcohol  and  ether, 
likewise  belong  to  this  class  of  bodies,  and  may  be  represented  by  the  fol- 
lowing formulae,  which  show  that  isethionic  acid  is  monobasic,  ethionic  acid 
bibasic,  and  ethionic  oxide  neutral: 

H2CH  H2C— S03H  H2C— S— 0— 0 

0  0  0  O 

H2C-S03H  H2C-S03H  H2C— S— 0— O 

Isethionic  acid.       Ethionic  acid.  Ethionic  oxide. 


ALDEHYDES. 

These  are  bodies  derived  from  alcohols  by  elimination  of  one  or  more 
molecules  of  hydrogen  (H2),  without  introduction  of  an  equivalent  quan- 
tity of  oxygen,  so  that  they  hold  a  position  intermediate  between  the  alco- 
hols and  the  acids ;  thus : 

CH3  CJHjj  dij 

CH2OH  COH  COOH 

Ethyl  Acetic  Acetic 

alcohol.  aldehyde.  acid. 


684:        ALDEHYDES    FROM    MONATOMIC   ALCOHOLS. 

The  hydrogen  eliminated  in  the  conversion  of  an  alcohol  into  an  acid  is 
that  which  is  in  immediate  connection  with  the  hydroxyl,  or  which  belongs 
to  the  group  CH2OH;  consequently  a  monatomic  alcohol  can  yield  but  one 
aldehyde ;  but  a  diatomic  alcohol  can  yield  two,  by  substitution  of  0  for 
H2,  and  of  02  for  2H2;  a  triatomic  alcohol  three,  and  so  on.  At  present, 
however,  we  are  acquainted  only  with  aldehydes  derived  from  monatomic 
and  diatomic  alcohols. 


Aldehydes  derived  from  Monatomic  Alcohols. 
Of  these  aldehydes  four  series  are  known,  viz.  : 

1.  Aldehydes,  CnH2tlO,  corresponding  to  the  Fatty  adds. 


Formic  aldehyde 
Acetic  aldehyde  .     . 
Propionic  aldehyde 
Butyric  aldehyde 
Valeric  aldehyde     . 


C2H40 


Oaproic  aldehyde 
(Enanthylic  aldehyde 
Caprylic  aldehyde     . 
Euodic  aldehyde  . 


C8H, 


n,60 
CnH220. 


2.  Aldehydes,  CnH2n_20,  corresponding  to  the  Acrylic  acids. 

Acrylic  aldehyde,  or  Acrolein          .         .         .         C3H40 
3.  Aldehydes,  CnH2n_80,  corresponding  to  the  Aromatic  acids. 

Benzoic  aldehyde,  or  Bitter-almond  oil  .         .  CTH60 

Toluic  aldehyde C8H80 

Cumic  aldehyde C10H15!C 

Sycocerylic  aldehyde      .... 

4.  Aldehydes,  CnH2n_100. 
Cinnamic  aldehyde         .... 


CQH00, 


All  these  aldehydes  contain  two  atoms  of  hydrogen  less  than  the  corre- 
sponding alcohols,  and  one  atom  of  oxygen  less  than  the  corresponding 
acids. 

They  are  produced  :  — 1.  By  oxidation  of  alcohols,  either  by  the  action 
of  atmospheric  oxygen,  or  by  that  of  a  mixture  of  dilute  sulphuric  acid  and 
potassium  bichromate  or  manganese  dioxide,  or  by  the  action  of  chlorine 
on  the  alcohol  diluted  with  water,  the  chlorine  in  this  case  decomposing 
the  water,  and  thus  acting  as  an  oxidizing  agent. 

2.  By  distilling  an  intimate  mixture  of  the  potassium-salt  of  the  corre- 
sponding acid  with  potassium  formate  ;  e.  g.  : 


COCH3(OK) 
Potassium 

acetate. 

COC6H6(OK) 

Potassium 

benzoate. 


-f     COH(OK)  =     CO(OK)2    -f 
Potassium  Potassium 

formate.  carbonate. 

+     COH(OK)  =     CO(OK)2     -f 


Acetic 
aldehyde. 
C6H5.COH 

Benzoic 
aldehyde. 


3.  By  the  action  of  nascent  hydrogen  (evolved  by  the  action  of  dry  hy- 
drochloric acid  gas  on  sodium  amalgam)  on  the  cyanides  of  acid  radicals : 


C7H5OCN 

Benzoyl 

cyanide. 


H, 


CNH 

Hydrocyanic 
acid. 


Benzoic 
aldehyde. 


ALDEHYDES    FKOM    MONATOMIC   ALCOHOLS.          685 

Properties.  —  The  following  properties  are  common  to  all  the  monatomic 
aldehydes : 

1.  They  easily  take  up  oxygen,  and  are  converted  into  the  corresponding 
acids. 

2.  When  fused  with  potash,  they  are  converted  into  the  corresponding 
acids,  with  evolution  of  hydrogen :  e.  g. : 

C7H60        4-        KOH        =        C7H5K02        +        H2. 
Benzoic  Potassium 

aldehyde.  benzoate. 

3.  Nascent  hydrogen,  evolved  by  the  action  of  water  on  sodium  amalgam, 
converts  them  into  the  corresponding  alcohols;  e.  g.,  C2H40  -f-  H2  =  C2H60. 
If,  however,  the  aldehyde  belongs   to  a  non-saturated   series,  the   action 
goes  further,  an  additional   quantity  of  hydrogen  being  then   taken  up, 
whereby  the  alcohol  first  formed  is  converted  into  a  saturated  alcohol  be- 
longing to  another  series;  thus: 

C3H40     +     Ha    =    C3H60;  and  C3H60     -f     H2    =    C3H80 

Acrylic  Allyl  Allyl  Propyl 

aldehyde.  alcohol.         alcohol.  alcohol. 

Nascent  hydrogen  evolved  by  the  action  of  zinc  on  sulphuric  acid  does  not 
appear  to  unite  with  aldehydes. 

4.  Phosphorus  pentachloride  converts  aldehydes  into  chloraldehydes,  com- 
pounds derived  from  aldehydes  by  substitution  of  C12  for  0 ;  thus : 

CH3  CH3 

I  +  PC16        =        PC130        4-          I 

COH  CHC12 

Aldehyde.  Chloraldehyde. 

.The  compounds  thus  produced  are  isomeric  with  the  chlorides  of  the  ole- 
fines;  e.g.,  acetic  chloraldehyde,  CH3.CHCL,  or  ethidene  chloride,  with 
ethene  chloride,  C2H4  .  C12  (p.  484). 

5.  Chlorine  and  bromine  convert  aldehydes  into  chlorides  of  acid  radicals  : 

C2H40        -f-       C12       =        HC1       4-       C2H3O.C1 
Aldehyde.  Acetyl  chloride. 

C2H40       +      2C13      =       2HC1      +     C2H2C10.C1 
Aldehyde.  Chloracetyl 

chloride. 

6.  The   alkali-metals  dissolve  in  aldehydes,   eliminating  an  equivalent 
quantity  of  hydrogen : 

2CH40       +       K3        =        H2         -f        2C2H3KO 
Aldehyde.  Potassium 

aldehyde. 

7.  Aldehydes  treated  with  hydrocyanic  acid,  hydrochloric  acid,  and  water,  are 
converted  into  an  ammonium-salt,  or  an  amidated  acid,  containing  an  ad- 
ditional atom   of  carbon,  the  former  reaction  taking  place  chiefly  in  th<i 
aromatic  series,  the  latter  in  the  fatty  series : 

C2H40      4-      CNH      4-      OH2      =      C3H7N02 
Acetic  Amidopropionic 

aldehyde.  acid  (alanine). 

C7H60  4-       CNH      4-     20H2     =      C8H7(NH4)03 
Benzoic  Ammonium 

aldehyde.  formobenzoate. 

68 


ALDEHYDES,  CUH2UO. 

8.  Aldehydes  unite  with  aniline,  water  being  eliminated,  and  form  bases 
derived  from  a  double  molecule  of  aniline,  (C6H7N)2,  by  substitution  of  two 
equivalents  of  a  diatomic  radical  for  four  atoms  of  hydrogen ;  e.  g. : 

(C2H40)2  +      2C6H7N      =      20H2      +      C12H10(C2H4)"2N2 
Acetic  Aniline.  Diethidene- 

aldehyde.  dianiline. 

9.  All  aldehydes  unite  directly  with  the  add  sulphites  of  the  alkali-metals, 
forming  crystalline  compounds,  by  which  they  may  be  readily  separated 
from  other  bodies  with  which  they  may  be  mixed.     This  reaction  affords 
a  ready  means  of  purifying   aldehydes,    and  likewise   of  detecting  their 
presence. 

10.  Aldehydes  also  unite  with   acetic  oxide,  forming  such  compounds  as 
C2H40//(C2H30)2,   and  probably  with  the  oxides  corresponding  to  other 
monobasic  acids. 


Aldehydes  belonging  to  the  Series  CnH2nO. 

Formic  Aldehyde,  CH20  or  H .  COH,  also  called  MeAhylic  aldehyde.— This 
compound,  recently  discovered  by  Hofmann,*  is  produced  when  a  current 
of  air  charged  with  vapor  of  methyl  alcohol  is  directed  upon  an  incandes- 
cent spiral  of  platinum  wire ;  and  by  suitable  condensing  arrangements,  a 
liquid  may  be  obtained  consisting  of  a  solution  of  the  aldehyde  in  methyl 
alcohol.  This  liquid,  rendered  slightly  alkaline  by  ammonia,  and  gently 
warmed  with  silver  nitrate,  yields  a  beautiful  specular  deposit  of  silver, 
with  greater  ease  even  than  ordinary  acetic  aldehyde.  The  same  solution, 
heated  with  a  few  drops  of  caustic  potash,  deposits  drops  of  a  brownish 
oil,  having  the  odor  of  the  resin  of  acetic  aldehyde. 

Formic  aldehyde  has  not  yet  been  obtained  in  the  pure  state ;  but  by 
treating  its  solution  with  hydrogen  sulphide,  and  heating  the  resulting 
liquid  with  strong  hydrochloric  acid,  it  solidities,  on  cooling,  to  a  dazzling 
white  mass  of  felted  needles,  consisting  of  the  corresponding  sulphur-com- 
pound, CH2S. 

Acetic  Aldehyde,  C2H40  =  CH3  .  COH  —  CH30  .  H,  generally  designated 
by  the  simple  name  aldehyde.^  —  This  substance  is  formed,  among  other 
products,  when  the  vapor  of  ether  or  alcohol  is  transmitted  through  a  red- 
hot  tube;  also,  by  the  action  of  chlorine  on  weak  alcohol,  and  by  the  other 
general  reactions  above  mentioned.  It  is  best  prepared  by  the  following 
process :  6  parts  of  oil  of  vitriol  are  mixed  with  4  parts  of  rectified  spirit 
of  wine,  and  4  parts  of  water;  this  mixture  is  poured  upon  6  parts  of  pow- 
dered manganese  dioxide  contained  in  a  capacious  retort,  in  connection 
with  a  condenser  cooled  by  ice-cold  water ;  gentle  heat  is  applied,  and  the 
process  is  interrupted  when  6  parts  of  liquid  have  passed  over.  The  dis- 
tilled product  is  put  into  a  small  retort,  with  its  own  weight  of  calcium 
chloride,  and  redistilled ;  and  this  operation  is  repeated.  The  aldehyde, 
still  retaining  alcohol  and  other  impurities,  is  mixed  with  twice  its  volume 
of  ether,  and  saturated  with  dry  ammoniacal  gas ;  a  crystalline  compound 
of  aldehyde  and  ammonia  then  separates,  which  may  be  washed  with  a 
little  ether,  and  dried  in  the  air.  From  this  substance  the  aldehyde  may 
be  separated  by  distillation  in  a  water-bath,  with  sulphuric  acid  diluted 
with  an  equal  quantity  of  water;  by  careful  rectification  from  calcium 
chloride,  at  a  temperature  not  exceeding  30-5°  C.  (87°  F.),  it  is  obtained 
pure  and  anhydrous. 

*  Proceedings  of  the  Royal  Society,  xvi.  156.  f  Alcohol  dehydrogen^tus. 


ALDEHYDES,  CnH2nO.  687 

Aldehyde  is  a  limpid,  colorless  liquid,  of  characteristic  ethereal  odor, 
which,  when  strong,  is  exceedingly  suffocating.  It  has  a  density  of  0-790, 
boils  at  22°  C.  (72°  F.),  and  mixes,  in  all  proportions  with  water,  alcohol, 
and  ether:  it  is  neutral  to  test-paper,  but  acquires  acidity  on  exposure  to 
air,  from  the  production  of  acetic  acid:  under  the  influence  of  platinum- 
black  this  change  is  very  speedy.  When  a  solution  of  this  compound  is 
heated  with  caustic  potash,  a  remarkable  brown  resin-like  substance  is 
produced,  the  so-called  aldehyde-resin.  Gently  heated  with  silver  oxide,  it 
reduces  the  latter  without  evolution  of  gas,  the  metal  being  deposited  on 
the  inner  surface  of  the  vessel  as  a  brilliant  and  uniform  film;  the  liquid 
contains  silver  acetate. 

Aldehyde  can  be  reconverted  into  alcohol  by  treating  its  aqueous  solu- 
tion with  sodium  amalgam,  the  liquid  being  kept  slightly  acid  by  repeated 
additions  of  hydrochloric  acid. 

When  treated  with  hydrocyanic  acid,  aldehyde  yields  alanine  (p.  616). 

An  aqueous  solution  of  aldehyde,  treated  with  hydrogen  sulphide,  yields 
an  oily  compound,  (C2H40)6  .  SH2,  which  is  resolved  by  acids  into  hydrogen 
sulphide  and  sulphaldehyde,  C2H4S  :  the  latter  crystallizes  in  needles  having 
an  alliaceous  odor. 

Other  reactions  of  aldehyde  have  been  already  mentioned. 

Aldehyde-ammonia  or  Ammonium  aldehydate,  C2H40  .  NH3  or  C2H3(NH4)0, 
the  formation  of  which  has  been  already  mentioned,  forms  transparent, 
colorless  crystals,  of  great  beauty :  it  has  a  mixed  odor  of  ammonia  and 
turpentine ;  it  dissolves  very  easily  in  water,  with  less  facility  in  alcohol, 
and  with  difficulty  in  ether;  melts  at  about  76°  C.  (168°  F.),  and  distils 
unchanged  at  100°.  Acids  decompose  it,  with  production  of  an  ammoniacal 
salt  and  separation  of  aldehyde.  Hydrogen  sulphide  converts  it  into  a  basic 
compound,  C6H13NS2,  called  Ihialdine.  Sulphurous  oxide  gas  is  rapidly  ab- 
sorbed by  a  solution  of  aldehyde-ammonia,  forming  the  crystalline  com- 
pound C2H3(NH4)S03,  isorneric  with  taurin  (p.  527).  Aldehyde  also  com- 
bines with  acetic  oxide,  forming  the  compound  C2H40(C2H30)20  ;  also  with 
ethyl  oxide,  as  will  presently  be  further  noticed. 

Polymeric  Modifications  of  Aldehyde. — When  pure  aldehyde  is  long  pre- 
served in  a  closely-stopped  vessel,  it  is  sometimes  found  to  undergo  spon- 
taneous change  into  one,  and  even  two  isomeric  modifications,  differing 
completely  in  properties  from  the  original  compound.  In  a  specimen  kept 
•some  weeks  at  0°,  transparent  acicular  crystals  were  observed  to  form  in 
considerable  quantity,  which,  at  a  temperature  little  exceeding  that  of  the 
freezing  point  of  water,  melted  to  a  colorless  liquid,  miscible  with  water, 
alcohol,  and  ether ;  a  few  crystals  remained,  which  sublimed  without 
fusion,  and  were  probably  composed  of  the  second  substance.  This  new 
body,  called  elaldehyde,  is  identical  in  composition  with  aldehyde,  but  dif- 
fers in  properties  and  in  the  density  of  its  vapor;  the  latter  has  a  sp.  gr. 
of  4-515,  while  that  of  aldehyde  is  only  1  532,  or  one-third  of  that  number. 
It  refuses  to  combine  with  ammonia,  is  not  rendered  brown  by  potash,  and 
is  but  little  affected  by  solution  of  silver. 

The  second  modification,  or  metaldchyde,  is  sometimes  produced  in  pure 
aldehyde  kept  at  the  common  temperature  of  the  air,  even  in  hermetically 
sealed  tubes ;  the  conditions  of  its  formation  are  unknown.  It  forms 
colorless,  transparent,  prismatic  crystals,  which  sublime  without  fusion  at 
a  temperature  above  100°,  and  are  soluble  in  alcohol  and  ether,  but  not  in 
water.  They  also  were  found,  by  analysis,  to  have  the  same  composition 
as  aldehyde. 

ACETAL. — When  gaseous  hydrochloric  acid  is  passed  into  a  solution  of 
aldehyde  in  absolute  alcohol,  a  compound  of  aldehyde  and  ethyl  chloride, 
C2H40 .  C2II5C1,  is  produced,  and  this  compound,  treated  with  sodium 


688  ALDEHYDES;  CUH2UO. 

ethylate,  forms  a  compound  of  aldehyde  with  ethyl  oxide,  called  acetal : 

C.H4O.C,H6C1      +       C2H5ONa     =    NaCl    +     C2H40 .  (C2H6)20 
Ethylchloride  Sodium  Acetal. 

of  aldehyde.  ethylate. 

This  compound,  which  is  isomeric  with  diethylic  ethenate,  (C2H4)" (OC2II6)2 
(p.  557),  is  likewise  found  among  the  products  of  the  slow  oxidation  of  al- 
cohol under  the  influence  of  platinum-black. 

To  prepare  it  in  this  way,  spirit  of  wine  is  poured  into  a  large,  tall, 
glass  jar,  to  the  depth  of  about  an  inch,  and  a  shallow  capsule,  containing 
slightly  moistened  platinum-black,  is  arranged  above  the  surface  of  the 
liquid ;  the  jar  is  loosely  covered  by  a  glass  plate,  and  left  during  two  or 
three  weeks  in  a  warm  situation.  At  the  expiration  of  that  time  the  liquid 
is  found  highly  acid:  it  is  to  be  neutralized  with  potassium  carbonate,  as 
much  calcium  chloride  added  as  the  liquid  will  dissolve,  and  the  whole  sub- 
jected to  distillation,  the  first  fourth  only  being  collected.  Fused  calcium 
chloride  added  to  the  distilled  product  now  throws  up  a  light  oily  liquid, 
which  is  a  mixture  of  acetal  with  alcohol,  aldehyde,  and  acetic  ether.  By 
fresh  treatment  with  calcium  chloride,  and  long  exposure  to  gentle  heat  in 
a  retort,  the  aldehyde  is  expelled.  The  acetic  ether  is  destroyed  by  caus- 
tic potash,  and  the  alcohol  removed  by  washing  with  water,  after  which 
the  acetal  is  again  digested  with  fused  calcium  chloride  and  redistilled. 

Pure  acetal  is  a  thin,  colorless  liquid,  of  agreeable  ethereal  odor,  of  sp. 
gr.  0-821  at  22-2°  C.  (72°  F.),  and  boiling  at  140°  C.  (284°  F.).  It  is  sol- 
uble in  18  parts  of  water,  and  miscible  in  all  proportions  with  alcohol  and 
ether.  It  is  unchanged  in  the  air ;  but,  under  the  influence  of  platinum- 
black,  becomes  converted  into  aldehyde,  and  eventually  into  acetic  acid. 
Nitric  and  chromic  acids  produce  a  similar  effect.  Strong  boiling  solution 
of  potash  has  no  action  on  this  substance. 

CHLORAL,  C2HC1302.  —  This  compound,  already  mentioned  as  being 
formed  by  the  prolonged  action  of  chlorine  on  absolute  alcohol  (p.  517), 
may  be  regarded  as  trichlorinated  aldehyde.  To  prepare  it,  the  current 
of  chlorine  must  be  kept  up  as  long  as  hydrochloric  acid  gas  continues  to 
escape,  and  the  product  agitated  with  three  times  its  volume  of  concen- 
trated sulphuric  acid.  On  gently  warming  this  mixture  in  a  water-bath, 
the  impure  chloral  separates  as  an  oily  liquid,  which  floats  on  the  surface 
of  the  acid ;  it  is  purified  by  distillation  from  fresh  oil  of  vitriol,  and  after- 
ward from  a  small  quantity  of  quicklime,  which  must  be  kept  completely 
covered  by  the  liquid  until  the  end  of-the  operation.  Chloral  has  also  been 
obtained  from  starch,  by  distillation  with  hydrochloric  acid  and  manga- 
nese dioxide. 

Chloral  is  a  thin,  oily,  colorless  liquid,  of  peculiar  and  penetrating  odor, 
which  excites  tears:  it  has  but  little  taste.  When  dropped  upon  paper  it 
leaves  a  greasy  stain,  which  is  not,  however,  permanent.  It  has  a  density 
of  1-502,  and  boils  at  94°  C.  (201°  F.).  Chloral  is  freely  soluble  in  water, 
alcohol,  and  ether ;  it  forms,  with  a  small  quantity  of  water,  a  solid,  crys- 
talline hydrate ;  the  solution  is  not  affected  by  silver  nitrate.  Caustic 
baryta  and  lime  decompose  the  vapor  of  chloral  when  heated  in  it,  with 
appearance  of  ignition ;  the  oxide  is  converted  into  chloride,  carbon  is  de- 
posited, and  carbon  monoxide  set  free.  Solutions  of  caustic  alkalies  also 
decompose  it,  with  production  of  a  formate  and  chloroform. 

When  chloral  is  preserved  for  any  length  of  time,  even  in  a  vessel  her- 
metically sealed,  it  undergoes  a  very  remarkable  change  —  being  converted 
into  a  solid,  white,  translucent  substance,  insoluble  chloral,  possessing  the 
same  composition  as  the  liquid  itself.  This  solid  product  is  but  very 
slightly  soluble  in  water,  alcohol,  or  ether ;  when  exposed  to  heat,  alone, 


ALDEHYDE,  CnH2n_2O. 


689 


or  in  contact  with  oil  of  vitriol,  it  is  reconverted  into  ordinary  chloral. 
Solution  of  caustic  potash  resolves  it  into  formic  acid  and  chloroform. 

Bromine  acts  upon  alcohol  in  the  same  manner  as  chlorine,  and  gives 
rise  to  a  product  very  similar  in  properties  to  the  foregoing,  called  bromal, 
which  contains  C2HBr30.  It  forms  a  crystallizable  hydrate  with  water, 
and  is  decomposed  by  strong  alkaline  solutions  into  formic  acid  and  bromo- 
form. 

The  other  aldehydes  of  the  series  CnH2nO  resemble  acetic  aldehyde  in 
most  of  their  reactions,  especially  in  forming  crystalline  compounds  with 
ammonia :  this  character  distinguishes  the  fatty  from  the  aromatic  alde- 
hydes, which  react  with  ammonia  in  a  different  way.  Another  character- 
istic reaction  of  the  fatty  aldehydes  is  their  conversion  into  amidated  acids 
by  the  action  of  hydrocyanic  acid  (p.  685) ;  in  this  manner  amido-propi- 
onic  acid,  or  alanine,  C3H7N02,  is  formed  from  acetic  aldehyde;  amido- 
caproic  acid,  or  leucine,  C6H,3N02,  from  valeral,  C5H,0On,  &c.  The  fatty 
aldehydes  are  all  converted  into  resinous  compounds  by  the  action  of  caus- 
tic potash. 

All  the  known  aldehydes  of  the  fatty  series  are  liquid  at  ordinary  tem- 
peratures, and  become  more  oily  as  their  molecular  weights  increase. 
Their  boiling  points  are  given  in  the  following  table  : 

Boiling  point. 

Acetic  aldehyde  .  22°  C.  72°  F. 
Propionic  "  55°-65°  C.  131°-149°" 
Butyric  "  68°-75°  "  154°-167°  " 
Valeric  «  93°"  199°" 

Euodic  aldehyde  is  the  essential  constituent  of  oil  of  rue.  It  differs  from 
the  other  compounds  of  the  series  by  not  reacting  in  the  manner  above 
mentioned  with  aniline. 


Boiling  point. 

(Enanthylic  aldehyde  152°  C.  305°  F. 
Caprylic  "          178°"    352°" 

Euodic  "          213°"    329°" 


Aldehyde  belonging  to  the  Series  CnH2n_20. 

C(CH2)"H 
Acrylic  Aldehyde,  or  Acrolein,  C3II40  =  |  .  — This  compound  is 

COH 

formed: — .  1.  By  the  oxidation  of  allyl  alcohol,  C3H60. — 2.  By  the  action 
of  heat  on  the  product  of  the  union  of  acetone  with  bromine : 


CO(CH3)2 
Acetone. 


Br2     = 


C(CH3)Br2 


=      2HBr 


C(CH2)"H 

COH 

Acrolein. 


3.  By  the  dehydration  of  glycerin,  when  that  substance  is  heated  with 
phosphoric  oxide,  strong  sulphuric  acid,  or  acid  potassium  sulphate  : 

C3H803  20  H2  C3II40. 

It  is  always  produced  in  the  destructive  distillation  of  neutral  fats  con- 
taining glycerin,  and  is  the  cause  of  the  intolerably  pungent  odor  attending 
that  process. 

Pure  acrolein  is  a  thin,  colorless,  highly  volatile  liquid,  lighter  than 
water,  and  boiling  at  52  2°  C.  (126°  F.).  Its  vapor  is  irritating  beyond 
description.  It  is  sparingly  soluble  in  water,  freely  in  alcohol  and  ether. 

Acrolein,  by  keeping,  undergoes  partial  decomposition,  yielding  a  white, 
flocculent,  indifferent  body.  <lix<i '•/•///;  the  same  substance  is  sometimes  pro- 
duced, together  with  acrylic  acid,  by  exposure  to  the  air.  In  contact  with 
58* 


690  AROMATIC    ALDEHYDES. 

alkalies,  acrolein  suffers  violent  decomposition,  producing,  like  aldehyde, 
a  resinous  body.  When  exposed  for  some  time  in  the  air,  or  when  mixed 
with  silver  oxide,  it  oxidizes  with  avidity,  and  passes  into  acrylic  acid, 
C3H402. 


Aromatic  Aldehydes,  CnH2n_80. 

Benzole  Aldehyde,  or  Bitter-almond  Oil,  C7H60  =  C6H6.  COH  =  C7H50  .  H. 
This  compound  is  produced  —  1.  By  the  oxidation  of  arnygdalin  with  nitric 

acid. 2.  By  digesting  bitter  almonds  with  water  for  five  or  six  hours  at 

30°-40°  C.  (8G°-104°  F.).  The  synaptase  present  then  acts  as  a  ferment 
on  the  amygdalin,  converting  it  into  glucose,  benzoic  aldehyde,  and  hydro- 
cyanic acid  (see  page  579).  Benzoic  aldehyde  is  prepared  by  this  process 
in  large  quantities,  chiefly  for  use  in  perfumery.  It  does  not  pre-exist  in 
the  almonds,  for  the  fat  oil  obtained  from  them  by  pressure  is  absolutely 
free  from  it.  The  crude  oil  has  a  yellow  color,  and  contains  a  very  con- 
siderable quantity  of  hydrocyanic  acid :  to  free  it  from  this  impurity,  it  is 
agitated  with  dilute  solution  of  ferrous  chloride  mixed  with  slaked  lime  in 
excess,  and  the  whole  is  subjected  to  distillation ;  water  passes  over,  ac- 
companied by  the  purified  essential  oil,  which  is  to  be  left  for  a  short  time 
in  contact  with  a  few  fragments  of  fused  calcium  chloride  to  free  it  from 
water. 

3.  Benzoic  aldehyde  is  formed,  together  with  many  other  products,  by 
the  action  of  a  mixture  of  manganese  dioxide  and  sulphuric  acid  on  albu- 
min, fibrin,  casein,  and  gelatin. 

4.  By  the  action  of  nascent  hydrogen  on  chloride  or  cyanide  of  benzoyl : 

C7H5OC1        1|-        H,        =        HC1        4-        C7H60. 

Pure  benzoic  aldehyde  is  a  thin,  colorless  liquid,  of  great  refractive 
power,  and  peculiar,  very  agreeable  odor:  its  density  is  1-013,  and  its  boil- 
ing point  180°  C.  (356°  F.):  it  is  soluble  in  about  30  parts  of  water,  and 
miscible  in  all  proportions  with  alcohol  and  ether.  Exposed  to  the  air,  it 
greedily  absorbs  oxygen,  and  is  converted  into  a  mass  of  crystallized  ben- 
zoic acid.  Heated  with  solid  potassium  hydrate,  it  gives  off  hydrogen,  and 
yields  potassium  benzoate.  With  the  alkaline  bisulphites  it  forms  beautiful 
crystalline  compounds.  The  vapor  of  the  oil  is  inflammable,  and  burns 
with  a  bright  flame  and  much  smoke.  It  is  very  doubtful  whether  pure 
bitter-almond  oil  is  poisonous ;  but  the  crude  product,  sometimes  used  for 
imparting  an  agreeable  flavor  to  confectionery,  is  very  dangerous. 

Benzoic  aldehyde,  treated  with  sodium  amalgam,  is  converted  into  benzyl 
alcohol,  C7HgO.  With  phosphorus  pentachloride,  it  yields  benzylene  chloride, 
C7H6C12 : 

C7H60         +        PC15        =         PC130         +         C7H6C12. 

Ammonia  converts  it  into  hj/drobenzamide,  a  white  crystalline  neutral  body, 
which,  when  boiled  with  aqueous  potash,  is  converted  into  an  isomeric 
basic  compound,  called  amarine: 

3C7H60       +       2NH3      =       (C7H.)",N2      +       SOH2. 
BenzQic  Hydroberi- 

aldehyde.  zamide. 

All  the  aromatic  aldehydes  act  with  ammonia  in  a  similar  manner,  and  are 
thereby  distinguished  from  the  aldehydes  of  the  fatty  series. 

Toluic  Aldehyde,  C8H80,  is  produced  by  distilling  a  mixture  of  the  cal- 
cium-salts of  toluic  and  formic  acids.  The  oily  distillate  agitated  with  acid 


AROMATIC   ALDEHYDES.  691 

sodium  sulphite,  forms  a  crystalline  compound,  which,  when  distilled  with 
sodium  carbonate,  yields  the  aldehyde,  as  an  oil  having  a  peppery  odor, 
and  boiling  at  204°  C.  (399°  F.).*  On  exposure  to  the  air,  it  is  gradually 
converted  into  toluic  acid,  C8II802.  With  alcoholic  potash  it  forms  potassium 
toluate  and  xylyl  alcohol. 

2C8H80     +     KOH     =    C8H7K02    +     C8H100. 

Cumic  Aldehyde,  C10H,20,  exists  together  with  cymene,  C10H,4,  in  the 
essential  oil  of  cumin,  and  in  that  of  water  hemlock  (Cicuta  virosa),  and 
may  be  obtained  by  agitating  either  of  these  oils  with  acid  sodium  sul- 
phite, which  takes  up  the  cumic  aldehyde,  but  not  the  cymene,  and  forms 
a  crystalline  compound,  from  which  the  aldehyde  may  be  separated  by  dis- 
tillation with  potash.  Cumic  aldehyde  is  a  colorless  or  slightly  yellow 
liquid,  having  a  powerful  odor,  and  is  easily  oxidized  in  the  air,  so  that  it 
must  be  distilled  in  a  current  of  carbonic  acid  gas.  It  is  converted  into 
cumic  acid,  C,0H1202,  by  oxidation,  and  by  alcoholic  potash  into  potassium 
cumate  and  cymyl  alcohol,  C10H140. 

Sycocerylic  Aldehyde,  C18H280,  appears  to  be  produced  in  thin  prisms  by 
oxidizing  sycoceryl  alcohol  with  aqueous  chromic  acid. 

Cinnamic  Aldehyde,  C9H80. — This  compound,  which  is  the  only  known 
member  of  the  series  of  aldehydes  CnH2n_ ioO,  constitutes  the  essential 
part  of  the  volatile  oils  of  cinnamon  and  cassia,  which  are  obtained  from 
the  bark  of  different  trees  of  the  genus  Cinnamonum,  order  Lauracese — • 
viz.,  oil  of  cinnamon,  from  Ceylon  cinnamon,  and  oil  of  cassia,  from  Chi- 
nese cinnamon.  The  aldehyde  may  be  separated  from  these  oils  by  means 
of  acid  potassium  sulphite.  It  is  a  colorless  oil,  rather  heavier  than  water; 
may  be  distilled  without  alteration  in  a  vacuum,  or  with  de-aerated  water: 
but  absorbs  oxygen  quickly  on  exposure  to  the  air,  and  passes  into  cin- 
namic  acid.  When  fused  with  potash,  it  forms  potassium  cinnamate,  and 
gives  off  hydrogen: 

C9H80        -f        KOH        =        C9H7K02        +        H2. 
Ammonia  gas  converts  it  into  hydrocinnamide  : 

3C9H80        +        2NHS       =r        (C9H8)"3N2    -f        30H2. 

No  aldehydes  are  known  belonging  to  the  series  intermediate  between 
CnH2n_20,  and  CnH2n_80. 

There  is  indeed  a  well-known  substance  —  viz.,  common  camphor,  or 
laurel  camphor,  having  the  composition  C10H160,  which  is  that  of  the  alde- 
hyde of  camphol,  C,0H180  (p.  546) ;  but  its  properties  are  not  those  of  an 
aldehyde,  inasmuch  as  it  does  not  unite  with  alkaline  bisulphites  or  with 
aniline,  and  when  fused  with  potash,  does  not  give  off  hydrogen  and  form 
the  potassium-salt  of  the  corresponding  acid,  but  unites  directly  with  the 
alkali,  forming  potassium  campholate,  C10H17K02.  It  may,  however,  be 
conveniently  described  in  this  place. 

Camphor  is  obtained  by  distilling  with  water  the  wood  of  the  cnmphor- 
tree  (Laurus  Camphora).  When  pure  it  forms  a  solid,  white,  crystalline 
and  translucent  mass,  tough,  and  difficult  to  powder,  and  having  a  power- 
ful and  well-known  odor.  It  melts  when  gently  heated,  and  boils,  distil- 
ling unchanged  at  a  high  temperature.  It  sublimes  slowly  at  the  tempera- 
ture of  the  air,  and  often  forms  beautiful  crystals  on  the  sides  of  bottles 
or  jars  containing  it  exposed  to  the  light.  Camphor  is  very  sparingly 
soluble  in  water,  but  readily  soluble  in  alcohol,  ether,  and  strong  acetic 
acid.  Small  pieces  of  it  thrown  upon  water  revolve  and  move  about  on 
the  surface,  with  more  or  less  velocity  in  proportion  to  their  smallness. 

By  the  action  of  nitric  acid  aided  by  heat,  camphor  is  gradually  oxi- 
dized and  dissolved,  with  production  of  camphoric  acid,  C10lIlt.O2  (p.  604). 


692  ALDEHYDES   FROM    DIATOMIC   ALCOHOLS. 

Common  camphor  exerts  a  dextro-rotatory  action  on  polarized  light  [a]  = 
-{-  47-4°;  but  by  distilling  the  essential  oil  of  feverfew  (Pyrethrum  parthe- 
nium),  and  collecting  apart  the  portion  which  passes  over  between  200° 
and  220°  C.  (392°-428°  F.),  an  oil  is  obtained,  which,  on  cooling,  deposits 
a  crystalline  substance  resembling  common  camphor  in  every  respect, 
except  that  its  action  on  polarized  light  is  exactly  equal  and  opposite :  [a] 
=  —  47-4°.  The  essential  oils  of  many  labiate  plants,  as  rosemary,  mar- 
joram, lavender,  and  sage,  often  deposit  a  substance  having  the  composi- 
tion and  all  the  properties  of  common  camphor,  excepting  that  it  is  inac- 
tive to  polarized  light. 


Aldehydes  derived  from  Diatomic  Alcohols. 

Diatomic  alcohols  can  yield  by  oxidation  two  classes  of  aldehydes,  ac- 
cordingly as  the  substitution  of  0  for  H2  takes  place  once  or  twice:  the 
products  thus  formed  may  be  distinguished  as  first  and  second  aldehydes. 
Propene  glycol,  C3H802,  for  example,  might  yield  the  two  aldehydes, 
C3H602  and  C3H402.  Only  a  few  of  these  compounds  have,  however,  been 
obtained. 

Of  aldehydes  derived  from  the  glycols,  CnH2n-f2,  only  one  is  known, 
namely  glyoxal,  C2H202,  which  is  the  second  aldehyde  of  ordinary  glycol, 
C2H602.  This  compound  is  obtained,  together  with  glyoxylic  acid  and 
other  products,  by  the  action  of  nitric  acid  upon  alcohol.  It  may  be  sepa- 
rated by  addition  of  a  strong  solution  of  acid  sodium  sulphite,  with  which 
it  forms  a  crystalline  compound  :  this  compound,  treated  with  barium  chlo- 
ride, yields  the  corresponding  barium  compound ;  and  from  this  the  gly- 
oxal  may  be  separated  by  dilute  sulphuric  acid.  On  evaporating  the 
liquid,  it  is  obtained  as  a  transparent,  amorphous,  deliquescent  mass,  very 
soluble  in  water,  alcohol,  and  ether.  With  an  ammoniacal  solution  of  sil- 
ver nitrate,  it  forms  a  beautiful  silver  speculum.  By  a  small  quantity  of 
nitric  acid  it  is  converted  into  glyoxylic  acid,  C2H404  ;  by  a  larger  quantity, 
into  oxalic  acid,  C2H204.  Fixed  caustic  alkalies  and  alkaline  earths  convert,  it 
into  a  salt  of  glycollic  acid;  e  a.,  C2H202-|-KOH=rC2H3K03.  A  syrupy  so- 
lution of  glyoxal,  heated  with  a  strong  aqueous  solution  of  ammonia,  yields 
two  bases,  glyoxaline  and  glycosine,  according  to  the  equations : 

2C2H202    +     2NH3     =     C3H4N2       +      CH202     +      20Ha 
Glyoxal.  Glyoxaline.        Formic  acid. 

3C2H202     +     4NH3    =        C6H6N4     +     60H2 
Glyoxal.  Glycosine. 

Both  these  bases  are  crystalline :  the  glyoxaline  is  by  far  the  more  abun- 
dant of  the  two. 

Of  aldehydes  derivable  from  diatomic  alcohols  belonging  to  other  series, 
three  only  are  known;  viz.,  salicylic  aldehyde,  C7Hfi09,  anisic  aldehyde, 
C8H802,  and  furfurol,  C6H402. 

Salicylic  Aldehyde,  or  Salicylol,  C7H602  =  C6H50  .  COH ;  also  called 
salicylous  acid,  and  hydride  of  salicyl. — This  compound  is  produced  by  oxi- 
dizing the  corresponding  alcohol,  saligenin,  C7H802,  with  potassium  chro- 
mate  and  dilute  sulphuric  acid.  As  salicin  (p.  581)  is  a  glucoside  of  sali- 
genin, and  populin  has  the  composition  of  benzoyl-salicin,  salicylol  may 
likewise  be  formed  from  these  bodies  by  the  action  of  oxidizing  agents  ; 
it  may  be  conveniently  prepared  by  treating  salicin  or  the  concentrated  ex- 
tract of  willow-bark  with  chromic  acid.  One  part  of  salicin  is  dissolved 
in  10  parts  of  water,  and  mixed  in  a  retort  with  1  part  of  powdered  potas- 


SALICYLIC   ALDEHYDE.  693 

shim  bichromate  and  2J  parts  of  oil  of  vitriol  diluted  with  10  parts  of 
water  ;  gentle  heat  is  applied,  and  after  the  cessation  of  the  effervescence 
first  produced,  the  mixture  is  distilled.  The  yellow  oily  product  is  sepa- 
rated from  the  water,  and  purified  by  rectification  from  calcium  chloride. 
Snlicylol  exists  ready  formed  in  the  flowers  of  meadow-sweet  (Spirxa  ul- 
mtiria),  and  may  be  obtained,  together  with  a  terpene,  by  distilling  the  flowers 
with  water.  On  neutralizing  the  distillate  with  potash,  boiling  to  expel  the 
hydrocarbon,  slightly  supersaturating  the  residue  with  phosphoric  acid, 
and  distilling,  salicylol  passes  over,  and  may  be  purified  by  agitating  the 
distillate  with  ether,  treating  the  decanted  ethereal  solution  with  potash, 
supersaturating  with  phosphoric  acid,  and  redistilling. 

Salicylol  is  a  thin,  colorless,  fragrant  oil,  acquiring  a  red  tint  by  expos- 
ure to  the  air.  It  has  a  specific  gravity  of  1-173,  solidifies  at — 20°  C. 
( — 4°F.),  boils  at  196-5°  C.  (385°  F.),  and  burns  when  set  on  fire,  with  a 
bright  smoky  flame.  Water  dissolves  a  perceptible  quantity  of  salicylol, 
acquiring  its  fragrant  odor,  and  the  property  (likewise  exhibited  by  sali- 
cylic acid)  of  producing  a  deep  violet  color  with  ferric  salts.  Alcohol  and 
ether  dissolve  it  in  all  proportions. 

Salicylol  is  oxidized  to  salicylic  acid  by  boiling  with  cupric  oxide  in  al- 
kaline solution,  partially  also  by  potassium  bichromate  and  sulphuric  acid ; 
it  likewise  reduces  silver  oxide.  When  heated  with  potassium  hydrate,  it 
is  converted  into  potassium  salicylate,  with  evolution  of  hydrogen: 

C7H602      +       KOH       =       C7H5K03      -f       H2. 

By  nascent  hydrogen  it  is  converted  into  saligenin,  C7H802 ;  by  ammonia, 
into  hydrosalicylamide : 

3C?H602      +       2NH2       =       30H2       +        C21H1803N2 
Salicylol.  Hydrosulicyl- 

amide. 

Salicylol  decomposes  alkaline  carbonates,  and  dissolves  in  caustic  alka- 
lies, forming  yellow  crystallizable  salts  ;  the  sodium-salt,  for  example,  hav- 
ing the  composition  C7H-Na02.  This  salt  and  the  corresponding  potassium 
and  ammonium-compounds,  are  soluble  in  water,  and  by  treating  their  so- 
lutions with  salts  of  barium,  copper,  lead,  silver,  &c.,  insoluble  metallic 
derivatives  of  salicylol  are  precipitated.  These  compounds  are  commonly 
'called  salici/litcs,  salicylol  itself  being  called  salicylous  acid  ;  but  it  is  bet- 
ter to  designate  them  as  sodium  salicylol,  copper  salicylol,  &c.,  inasmuch  as 
the  metal  contained  in  them  does  not  appear  to  occupy  the  same  place  as 
in  the  salt  of  an  ordinary  acid,  but  rather  to  take  the  place  of  the  alco- 
holic hydrogen  in  the  molecule  of  salicylol,  C6H50  .  COH,  so  that  sodium 
salicylol  consists  of  C6H4NaO  .  COH.  This  salt,  treated  with  methyl-iodide, 
yields  sodium  iodide  and  methyl-salicylol,  C6H4(CH3)0  .  COH,  a  compound 
exhibiting  properties  exactly  analogous  to  those  of  salicylol  itself.  Ethyl- 
salicylol,  C6M4(C2H5)0  .  COH,  is  obtained  in  a  similar  manner.*  Ammonia 
acts  upon  these  compounds  in  the  same  manner  as  on  salicylol,  converting 
them  into  methyl-hydrosalicylamide,  C21H17(CH3)03N2,  and  ethyl-hydrosali- 
cylamide,  C,,1I17(C2II5)03N2. 

Salicylol  is  strongly  attacked  by  chlorine  and  bromine,  forming  substi- 
tution-products, namely,  chlorosalicylol,  C7H6C102,  and  bromo-salicylol, 
C7II5Br02,  both  of  which  are  crystalline  bodies  possessing  acid  properties. 
Iodine,  dissolves  in  it,  but  does  not  form  a  substitution-product.  Moderately 
strong  nitric  acid  converts  it  into  nitro-salicylol,  C7IIB(N02)02,  which  is  also 
crystalline,  and  forms  crystallizable  salts.  Chlorosulicylol  is  acted  upon 
by  ammonia  in  the  same  manner  as  salicylol,  forming  chlorohydrosalicyla- 
mide,  or  chlorosamide,  C21H15C1303N2. 

*  Perkin,  Chem.  Soc.  Journal  [2],  v.  418. 


694  ALDEHYDES    FROM    DIATOMIC   ALCOHOLS. 

Methyl-salicylol  and  ethyl-salicylol  are  also  attacked  by  chlorine  and 
bromine,  forming  substitution-derivatives  similar  to  those  of  salicylol  it- 
self, e.g.,  ethyl-bromosalicylol,  C7H4(CH3)Br02. 

Salicylol  and  all  its  substitution-derivatives  above  mentioned,  form  crys- 
talline compounds  with  the  acid  sulphites  of  the  alkali-metals. 

Salicylol  unites  with  acetic  oxide  or  anhydride*  forming  the  crystalline 
compound  CnH1205  ==  C7H602  .  (C2H30)20.  Acetic  oxide  likewise  forms 
similar  compounds  with  methyl-  and  ethyl-salicylol. 

Sodium-salicylol,  treated  with  acetic  oxide,  forms  sodium  acetate  and 
nceto-salicylol.  ~f 

C6H4NaO  .  COH  +  (C2H30).,0  =  NaOC2H30  +  C6H4(C2H30)0  .  COH 
Sodium-salicylol.         Acetic  Sodium  Acetosalicylol. 

oxide.  acetate. 

This  compound  has  the  same  composition  as  coumaric  acid,  C9H803,  an  acid 
produced  by  the  hydration  of  coumarin,  the  odoriferous  principle  of  the 
Tonka  bean  ;  but  to  obtain  it  by  the  reaction  above  mentioned,  certain  pre- 
cautions are  necessary.  The  acetic  oxide  must  be  added  to  powdered  an- 
hydrous sodium-salicylol  suspended  in  pure  dry  ether,  the  reagents  being 
employed  in  equivalent  quantities  ;  and  after  the  whole  has  stood  for  twen- 
ty-four hours,  the  ethereal  liquid  must  be  filtered  off  from  the  sodium  ace- 
tate, then  evaporated,  and  the  crystalline  cake  which  separates  on  cooling, 
purified  by  pressure  between  bibulous  paper,  and  crystallization  from  alco- 
hol. Acetosalicylol  thus  prepared  melts  at  37°  C.  (98°  F.),  boils  at  about 
253°  C.  (487°  F.),  and  distils  without  decomposition.  It  is  an  aldehyde, 
like  salicylol  itself,  and  forms  definite  compounds  with  alkaline  bisulphites. 
It  is  decomposed  by  alcoholic  potash,  with  formation  of  potassium  acetate 
and  potassium-salicylol: 

C6H4(C2H30)0  .  COH  +  2KOH  =  C6H4KO  .  COH  -f  C2H3K02  -f  OH2. 

Acetosalicylol  likewise  unites  directly  with  acetic  oxide. 

If  the  product  of  the  action  of  acetic  oxide  on  salicylol,  instead  of  being 
treated  in  the  manner  above  described,  be  poured  into  water  after  a  few 
minutes'  boiling,  an  oily  liquid  sinks  to  the  bottom,  and  sodium-acetate  re- 
mains in  solution  ;  and  on  distilling  this  oil,  and  collecting  apart  that  which 
passes  over  after  the  temperature  has  risen  to  290°  C.  (554°  F.),  a  crystalline 
substance  is  obtained, having  the  composition  of  acetosalicylol  minus  one  mole- 
cule of  water :  this  substance  is  identical  in  every  respect  with  natural  couma- 
rin,  C9H602.  The  dehydration  of  the  acetosalicylol  appears  to  be  due  to  the 
action  of  the  sodium-acetate,  perhaps  to  the  formation  of  an  anhydroace- 
tate  or  biacetate  of  sodium,  2C2H3Na02 .  C4H603,  analogous  to  potassium 
anhydrosulphate  (p.  297),  which  appears  to  exert  a  more  powerful  dehy- 
drating action  than  acetic  oxide  itself. 

Coumarin  thus  obtained  has  lost  the  properties  of  an  aldehyde,  no  longer 
uniting  with  alkaline  bisulphites;  it  differs  also  from  acetosalicylol  in  not 
being  split  up  into  acetic  acid  and  salicylol  by  the  action  of  strong  potash, 
but  simply  taking  up  an  atom  of  water  and  being  converted  into  coumaric 
acid. 

Coumarin,  as  already  observed,  is  the  odoriferous  principle  of  the  Tonka 
bean.  It  may  be  often  seen,  forming  minute,  colorless  crystals  under  the 
skin  of  the  seed,  and  between  the  cotyledons.  It  is  best  extracted  by  ma- 
cerating the  sliced  beans  in  hot  alcohol,  and,  after  straining  through  cloth, 
distilling  off  the  greater  part  of  the  spirit.  The  syrupy  residue  deposits, 
on  standing,  crystals  of  coumarin,  which  must  be  purified  by  pressure  from 
a  fat  oil  which  abounds  in  the  beans,  and  then  crystallized  from  hot  water. 

*  Perldn,  Chem.  Soc.  Journal  [2]  v.  586. 
t  Ibid.  [2],  vi.  53,  181. 


ANISIC   ALDEHYDE  —  FUKFUROL.  695 

So  obtained,  coumarin  forms  slender,  brilliant,  colorless  needles,  fusible  at 
about  67°  C.  (157°  F.),  boiling  between  290°  and  291°  C.  (555°  F.),  and  dis- 
tilling without  decomposition  at  a  higher  temperature.  It  has  a  fragrant 
odor  and  burning  taste;  is  very  slightly  soluble  in  cold  water,  more  soluble 
in  hot  water,  and  in  alcohol.  It  is  unaffected  by  dilute  acids  or  alkalies,  which 
merely  dissolve  it.  Boiling  nitric  acid  converts  it  into  picric  acid,  and  a 
hot  concentrated  solution  of  potash  converts  it  into  coumaric  acid,  C9H803, 
and  eventually  into  salicylic  acid.  Coumarin  exists  in  several  other  plants, 
as  in  Melilotus  offieinalis,  Asperula  odorata,  and  Anthoxanthum  odoratum. 

By  acting  on  sodium  salicylol  with  butyric  and  valeric  oxides,  Perkin 
has  obtained  homologues  of  coumarin,  viz.,  butyric  coumarin,  CUH1002,  and 
valeric  coumarin,  C12H,202. 

Anisic  Aldehyde,  C8HS02,  also  called  Anisal  and  Hydride  of  Anisyl,  is 
formed,  together  with  anisic  acid,  by  oxidation  of  anisic  alcohol,  C8H1002, 
with  platinum-black,  or  of  anise  oil  with  warm  nitric  acid : 

C1?H120     +     06    =    C8H802    +     C2H204    +     OH2. 
Anise  oil.  Anisic  Oxalic 

aldehyde.  acid. 

It  is  a  yellowish  liquid,  having  an  aromatic  odor  and  a  burning  taste,  nearly 
insoluble  in  water,  but  soluble  in  all  proportions  in  alcohol  and  ether.  It 
is  converted  by  oxidation  into  anisic  acid,  C8H803 ;  by  nascent  hydrogen 
into  anisic  alcohol,  C8H,0O2,  and  forms  crystalline  compounds  with  alkaline 
bisulphites.  Ammonia  converts  it  into  anishydramide,  C24H2403N2.  By 
alcoholic  potash  it  is  decomposed  in  the  same  manner  as  benzoic  aldehyde, 
yielding  potassium  anisate  and  anisic  alcohol: 

2C8H802       +       KOH       =       C8H7K02      +       C8H190 

Anisic  Potassium  Anisic 

aldehyde.  anisate.  alcohol. 

Oil  of  anise  is  a  solution  of  a  solid  substance  called  anise-camphor,  having 
the  composition  C,0H120,  in  a  fluid  oil  which  appears  to  have  the  composi- 
tion of  oil  of  turpentine.  The  anise-camphor  is  so  abundant  as  to  cause 
the  whole  to  solidify  at  10°  C.  (50°  F.).  By  pressure  between  folds  of  bibu- 
lous paper,  and  crystallization  from  alcohol,  the  camphor  may  be  obtained 
'pure.  It  forms  colorless  pearly  plates,  more  fragrant  than  the  crude  oil, 
which  melt  when  gently  heated,  and  distil  at  a  high  temperature.  This 
substance  is  attacked  energetically  by  chlorine,  bromine,  and  nitric  acid: 
it  combines  with  hydrochloric  acid,  but  is  unaffected  by  solution  of  caustic 
potash.  With  bromine  the  solid  essence  yields  a  white,  inodorous,  crys- 
tallizable  compound,  bromanisal,  containing  C10H9Br30.  The  action  of  chlo- 
rine is  more  complex,  several  successive  compounds  being  produced.  With 
sulphuric  acid  two  products  are  obtained  —  a  compound  acid  analogous  to 
ethylsulphuric  acid,  and  a  white,  solid,  neutral  substance,  aniso'in,  isomeric 
with  the  fluid  essence. 

The  products  of  the  action  of  nitric  acid  vary  with  the  strength  of  the 
acid  employed  :  the  most  important  are,  anisic  aldehyde;  anisic  acid;  nitra- 
nisic  acid,  a  yellowish-white,  crystalline,  sparingly  soluble  powder;  and 
nilraniside,  a  resinous  body  produced  by  fuming  nitric  acid. 

Furfurol,  C5H402.  — When  sulphuric  acid  diluted  with  an  equal  bulk  of 
water  is  carefully  mixed  with  twice  its  weight  of  wheat-bran,  and  the  ad- 
hesive pasty  mass  obtained  is  exposed  in  a  proper  vessel  to  the  action  of  a 
current  of  steam,  which  is  afterward  condensed  by  a  worm  or  refrigerator, 
a  liquid  is  obtained  which  holds  furfurol  in  solution.  By  redistillation 
several  times  repeated,  the  first  half  of  the  liquid  only  being  collected,  the 


696  KETONES. 

furfurol  can  be  extracted  from  the  water,  and  then  by  distillation  alone 
obtained  in  a  state  of  purity.  The  production  of  furfurol  is  very  greatly 
increased,  and  the  operation  much  facilitated,  by  previously  depriving  the 
bran  of  all  starch,  glutin,  and  soluble  matter,  by  steeping  it  in  cold  dilute 
solution  of  caustic  potash,  and  washing  and  drying  by  gentle  heat  or  in 
tne  sun.  Maceration  in  cold  water  for  some  time  answers  the  same  pur- 
pose, owing  to  the  lactic  acid  formed  in  that  case.  Furfurol  has  a  pale 
yellow  color,  and  a  fragrant  odor  like  that  of  oil  of  cassia:  its  specific 
gravity  is  1-165,  and  it  boils  at  162°  C.  (324°  F.),  distilling  unchanged.  It 
dissolves  in  all  proportions  in  alcohol  and  to  a  very  considerable  extent  in 
water,  and  is  readily  destroyed  by  strong  acids  and  caustic  alkalies,  espe- 
cially when  aided  by  heat.  The  specific  gravity  of  its  vapor  is  3-493. 
Furfurol  may  be  converted  into  silver  pyromucate  by  treating  its  aqueous 
solution  with  silver  oxide  : 

2C6H402    +     3Ag20    =    2C5H3Ag03    +    2Ag2     +     OH2. 

In  contact  with  solution  of  ammonia,  furfurol  is  converted  in  a  few 
hours  into  furfur  amide,  C,5H1203N2,  a  yellowish-white,  crystalline,  insoluble 
substance,  which  is  decomposed  slowly  by  water,  and  instantly  by  an  acid, 
into  ammonia  and  furfurol.  It  may  be  crystallized  from  alcohol,  however, 
in  which  it  dissolves  without  change.  When  boiled  with  dilute  potash,  it 
is  converted  into  the  isomeric  compound  furfurine,*  which  is  a  base  form- 
ing definite  salts  with  acids. 

FUCTJSOL.  —  By  treating  several  varieties  of  fucus  with  sulphuric  acid  in 
exactly  the  same  manner  as  in  the  preparation  of  furfurol,  Dr.  Stenhouse 
obtained  a  series  of  substances,  which  he  designates  by  the  terms  fucusol, 
fucusamide,  and  fucusine.  They  have  exactly  the  same  composition  as  the 
corresponding  terms  in  the  furfurol  series,  and  also  most  of  their  proper- 
ties, but  differ  in  some  details. 


KETONES. 

These  bodies  are  derived  from  aldehydes  by  substitution  of  an  alcohol- 
radical  for  hydrogen  in  the  group  COH ;  thus : 

Acetic  aldehyde CH3 .  COH 

Acetic  ketone  or  Acetone       .         .         .         CH3.COCH3. 

They  may  be  regarded  as  compounds  of  alcohol-radicals  with  acid  radi- 
cals—  acetone,  for  example,  as  methyl-acetyl;  or  as  compounds  of  car- 
bonyl,  C0/x,  with  two  univalent  alcohol-radicals,  which  may  be  either  the 
same  or  different;  e.  g.  : 

00 

Acetone  or  methyl-  Methyl-propyl. 

acetyl. 

The  only  bodies  of  this  class  that  have  been  carefully  studied  are  those 
which  correspond  to  the  aldehydes  CnH2nO,  or  to  the  fatty  acids  CnH2n02. 

The  names,  formulae,  and  boiling-  points  of  the  best  known  ketones  of 
this  series  are  given  in  the  following  table : 

*  See  Organic  Bases. 


KETONES. 


697 


Name. 

Formula. 

Boiling  Point. 

Acetone,  or  Methyl-acetyl     . 
Ethyl-acetyl     •< 

CO(CH3)(CH3) 
CCKCI13)(CII2CH3)          I 
or  CO(CII3XC2I15) 
CO(CII3)ICH(C[I3)2] 
CO(CII3)(CH2C2U5)         \ 
or  CO(C1I8XC,II7)               / 
CO(C2II3)(C2H5) 

CO(C4TT9)(CH3) 
CO(C3H7)(C2H6) 

CO(CH3)[CH(C2H5)2] 
CO(C8H7)(C3H7) 

56°    C.    133°  F. 

81°     "      178°  " 
93-5°  "      200°  " 
101°     "      214°  " 
101°     "      214°  " 

120°     "      248°  " 
128°     "      262°  " 

138°     "      280°  " 
144°     "      291U  " 

.2     ^Propione,  or  Ethyl-propyl     . 
A'C  f  Methyl-  valeryl      

00  2  1  Ethvl-butvrvl 

i,  *c  /  Isobutyl-acetyl 

•8  g  t  Butyrone,  or  Propyl-butyryl 

The  ketones  of  this  group,  containing  two  equivalents  of  the  same  alco- 
hol-radical, are  produced  : 

1.  By  the  action  of  carbon  monoxide  on  sodium  ethide  and  its  homo- 
logues : 

CO     +     2NaCnH2a+1    =    Na2     +     CO(CnH2n+J)2. 
For  example : 

CO         +         2NaC2H5  =        Na2         -f 

Carbon  Sodium  ethyl, 

monoxide. 


CO(C2H6)2 
Propione. 


2.  By  the  action  of  zinc-methyl,  and  its  homologues,  on  the  acid  chlorides, 
BH2n_,OCl;  e.g.: 

2COCH3C1    =     ZnCl2     +     2CO(CH3)2 
Acetic  Acetone, 

chloride. 

3.  By. the  oxidation  of  the  secondary  alcohols;  thus: 

h        0      =      OH,        H 


Zn(CH3)2 
Zinc  methide. 


CH(CH3)2.OH 
Isopropyl  alcohol. 


CO(CH3)2 
Acetone. 


4.  By  the  dry  distillation  of  the  calcium-salts  of  the  fatty  acids ;  e.  g.  : 


c  „  ro(COCH3) 

Ca    \0(COCH3) 
Calcium  acetate. 


CO(CH3)2 
Acetone. 


Calcium 
carbonate. 

The  ketones  formed  in  this  manner  from  the  successive  members  of  the 
fatty  acid  series  differ  from  one  another  by  twice  CH2;  thus: 

Acetic  acid     .  .     .     C2H402,  yields  Acetone  .     .     .     CSH60. 

Propionic  acid  .     .  C3H602,       "       Propione  .     .     .  C5H100. 

Butyric  acid  .     .     C4H8O2,       "       Butyrone 
Valeric  acid  .  C.ILnO0, 


Valerone 


.  C9H180. 


The  intervals  are  filled  up  by  ketones  containing  different  alcohol-radi- 
cals ;  thus  ethyl-acetyl,  C4H80,  or  C2H5.  COCH3,  is  intermediate  between 
acetone  and  propione. 

The  ketones  containing  two  different  alcohol-radicals  may  be  obtained 
by  the  second  of  the  processes  above  given  ;  e.g.  : 


2COCH3C1 

Acetic 
chloride. 
50 


Zn(C2H5)2     = 
Zinc  ethyl. 


ZnCl2     -f 


Ethyl  ucetyl. 


(598  KETONES. 

Or  by  distilling  a  mixture  of  the  calcium-salts  of  two  different  fatty  acids  ; 
thus: 

Ca(COC4H9)2     +     Ca(COCH3)2    =    2C03Ca     +     2CO(CH3)(04H9) 
Valerate.  Acetate.  Butyl-acetyl. 

The  formation  of  aldehydes  by  distilling  a  mixture  of  a  formate  with  the 
salt  of  another  fatty  acid  (p.  684),  is  a  particular  case  of  this  last  reaction. 

Another  mode  of  producing  these  compounds  has  been  given  by  Frank- 
land  and  Duppa,*  depending  on  the  consecutive  action  of  sodium  and  the 
iodides  of  the  alcohol-radicals  CnH2n+,,  on  acetic  ether;  but  we  must  be 
content  with  referring  to  it. 

Every  ketone  is  isomeric  with  an  aldehyde  belonging  to  the  same  series  ; 
thus  acetone,  CH3  .  COCH3,  is  isomeric  with  propionic  aldehyde,  C2H5  .  COH  ; 
butyrone,  C3H7  .  COC3H7,  with  cenanthylic  aldehyde,  C6H13  .  COH,  &c. 
Formic  acetone,  H  .  COH,  is  identical  with  formic  aldehyde. 

Ketones  resemble  aldehydes  in  forming  crystalline  compounds  with  al- 
kaline bisulphites,  from  which  the  ketone  may  be  liberated  by  distillation 
with  an  alkali.  They  differ  from  the  aldehydes:  1.  In  not  being  converted 
by  oxidation  into  the  corresponding  acids.  —  2.  In  being  converted  by  nas- 
cent hydrogen  into  secondary  alcohols,  whereas  the  aldehydes  are  con- 
verted into  primary  alcohols.  —  3.  In  not  combining  with  aniline. 

The  only  ketone  that  has  been  studied  in  detail  is  acetone,  C3H60,  the 
ketone  of  acetic  acid.  This  body  is  prepared,  as  already  observed,  by  the 
destructive  distillation  of  acetates,  the  calcium  or  the  lead  salt  being  the 
most  convenient  for  the  purpose.  The  crude  distillate  is  saturated  with 
potassium  carbonate,  and  afterwards  rectified  in  a  water-bath  from  calcium 
chloride.  Acetone  may  also  be  prepared  by  passing  the  vapor  of  strong 
acetic  acid  through  an  iron  tube  heated  to  dull  redness,  the  acid  being  re- 
solved into  acetone,  carbon  dioxide,  carbon  monoxide,  and  carburetted  hy- 
drogen. 

Acetone  is  also  produced  in  the  destructive  distillation  of  citric  acid,  and 
may  be  procured  from  sugar,  starch,  and  gum,  by  distillation  with  eight 
times  their  weight  of  powdered  quicklime.  The  acetone  is,  in  this  case, 
accompanied  by  propione,  which  is  an  oily  liquid,  separable  from  the  ace- 
tone by  water,  in  which  it  is  insoluble. 

Pure  acetone  is  a  colorless  limpid  liquid,  of  peculiar  odor:  it  has  a 
density  of  0-792,  and  boils  at  55-5°  C.  (132°  F.):  the  density  of  its  vapor 
(referred  to  air)  is  2-022.  Acetone  is  very  inflammable,  and  burns  with 
a  bright  flame:  it  is  miscible  in  all  proportions  with  water,  alcohol,  and 
ether. 

Nascent  hydrogen  converts  it  into  isopropyl  alcohol  (p.  531)  ;  but  at  the 
same  time  a  portion  of  the  acetone  doubles  its  molecule,  and  likewise  takes 
up  hydrogen,  being  thereby  converted  into  a  crystalline  substance,  pina- 
cone,  C6HU02  =  2C3H60  -f-  H2,  which  is  perhaps  a  diatomic  alcohol. 

Acetone  treated  with  hydrocyanic  acid,  water,  and  hydrochloric  acid,  is 
converted  into  acetonic  acid,  C4H803,  isomeric  or  identical  with  oxybutyric 
acid: 


-f     20H2    -f-     HC1    =    NH4C1    -f    C4H803. 

When  acetone  is  heated  to  100°  with  ammonia,  the  two  unite,  with  elimina- 
tion of  water,  forming  a  basic  compound,  acetonme,  related  to  acetone  in 
the  same  manner  as  amarine  (p.  690)  to  benzoic  aldehyde  : 


8C.H.O       +       2NH?      =      N2(CBHe)",      +       30H2 
.  Acetonine. 

*  CUem.  Soc.  Journal  [2],  v.  103. 


KETONES.  699 

Acetone  distilled  with  fuming  sulphuric  acid,  or  other  powerful  dehydrat- 
ing agents,  is  converted  into  m^sityl-cne,  C9H,2  =  3C3H60  —  OH2  (p.  499). 
Phosphorus  pentachloride  converts  acetone  into  the  compound,  C3II6C12,  iso- 
meric  with  propene  chloride : 

C3H60         -f         PC16        =        PC130         -j-         C3H6C12. 

This  chloride  differs  in  boiling  point  from  propene  chloride,  but  resem- 
bles the  latter  in  its  reaction  with  alcoholic  potash,  which  converts  it  into 
chloropropene,  C3H5C1,  identical  with  that  obtained  from  propene. 

Hydrochloric  acid  likewise  converts  acetone  into  a  body  composed  of 
C3H5C1,  but  isomeric,  not  identical,  with  the  preceding.  This  compound, 
called  mesityl  chloride,  is  converted  by  alcoholic  potash  into  mesityl  oxide, 
(CSH5)20: 

2C3H6C1     +     2KOII     ==    2KC1     +      OH2     +      (C3H5)20; 

whereas  chloropropene  treated  with  alcoholic  potash  gives  up  hydrochloric 
acid,  and  yields  allylene  (p.  486)  :  C3H5C1  —  HC1  ^  C3H4. 

Of  the  aromatic  ketones  two  only  are  known,  viz.,  benzone  and  methyl- 
benzoyl. 

Benzone  or  Benzophenone,  C,3H100,  or  C6H5  .  COC6H5,  the  ketone  of  benzoic 
acid,  is  produced  by  heating  potassium  benzoate;  it  is  a  crystalline  body 
melting  at  46°  C.  (115°  F.),  boiling  at  815°  C.  (599°  F.),  and  distilling  with- 
out decomposition.  Warm  fuming  nitric  acid  converts  it  into  dinitroben- 
zone,  C13H8(N02)20. 

Methyl-benzoyl,  CH3 .  COC6H6,  is  formed  by  distilling  a  mixture  of  cal- 
cium acetate  and  benzoate. 


ORGANIC  COMPOUNDS  CONTAINING  NITROGEN. 


CYANOGEN  COMPOUNDS. 

We  have  already  mentioned  (p.  237)  that  the  name  cyanogen  is  applied 
to  the  univalent  radical  CN,  derived  from  the  saturated  molecule  Civ  j  H  , 

by  abstraction  of  hydrogen.  Cyanogen  is  a  chlorous  acid  or  negative  rad- 
ical, analogous  to  chlorine,  bromine,  and  iodine  :  its  compounds  with  metals 
and'  other  positive  radicals  are  called  cyanides : 

Hydrogen  cyanide,  or  Hydrocyanic  acid    .         .  C  N//XH 

Potassium  cyanide CivN'"K 

Ethyl  cyanide tW'CLH, 

Barium  cyanide (ON'")2Ba// 

Ethene  cyanide (ON'")2(C2H4)" 

Propenyl  cyanide (CiTN'")8(C8H§)"> 

Cyanogen,  in  its  capacity  of  a  quasi-element,  is  often  represented  by  the 
symbol  Cy. 

C=N 
Cyanogen  in  the  free  state,  C2N2,  or   |  ,  may  be  obtained  by  decom- 

C=N 

posing  certain  metallic  cyanides.  Pulverized  and  well-dried  mercuric  cy- 
anide, (CN)2Hg",  heated  in  a  small  retort  of  hard  glass,  undergoes  decom- 
position, like  the  oxide  under  similar  circumstances,  yielding  metallic  mer- 
cury, a  small  quantity  of  a  brown  substance,  of  which  mention  will  again 
be  made,  and  cyanogen  itself,  a  colorless,  permanent  gas,  which  must 
be  collected  over  mercury.  It  has  a  pungent  and  very  peculiar  odor, 
remotely  resembling  that  of  peach-kernels,  or  hydrocyanic  acid ;  exposed 
while  at  the  temperature  of  7-2°  C.  (45°F.)to  a  pressure  of  3-6  atmospheres, 
it  condenses  to  a  thin,  colorless,  transparent  liquid.  Cyanogen  is  inflam- 
mable :  it  burns  with  a  beautiful  purple  or  peach-blossom-colored  flame, 
generating  carbon  dioxide,  and  liberating  nitrogen.  The  specific  gravity 
of  this  gas  is  1-806.  Its  composition  may  be  demonstrated  by  mixing  it 
with  twice  its  measure  of  pure  oxygen,  and  firing  the  mixture  in  the  eudi- 
ometer ;  carbon  dioxide  is  formed  equal  in  volume  to  the  oxygen  employed, 
and  a  volume  of  nitrogen  equal  to  that  of  the  cyanogen  is  set  free.  Water 
dissolves  4  or  5  times  its  volume  of  cyanogen  gas,  and  alcohol  a  much 
larger  quantity  :  the  solution  rapidly  decomposes,  yielding  ammonium-ox- 
alate,  (C2N2-f  40H2  =  C2(NH4)204),  a  brown  insoluble  matter,  and  other 
products. 

PARACYANOGEN. —  This  is  the  brown  or  blackish  substance  above  re- 
ferred to,  which  is  always  formed  in  small  quantity  when  cyanogen  is 
prepared  by  heating  mercuric  cyanide,  and  probably,  also,  by  the  decom- 
position of  solutions  of  cyanogen  and  of  hydrocyanic  acid.  It  is  insoluble 
in  water  and  alcohol,  is  dissipated  by  a  very  high  temperature,  and  con- 
tains, according  to  Johnston,  carbon  and  nitrogen  in  the  same  proportion 
as  cyanogen. 

700 


HYDROCYANIC    ACID.  701 

Hydrogen  Cyanide;  Hydrocyanic  or  Prussic  Acid,  HCy. — This  very  im- 
portant compound,  so  very  remarkable  for  its  poisonous  properties,  was 
discovered  as  early  as  1782  by  Scheele.  It  may  be  formulated  as  azomelhane, 

^  i  H  '  ^ia^  *s  to  Sa^'  metnane  or  marsh-gas  having  three  of  its  hydro- 
gen-atoms replaced  by  nitrogen,  or  as  methenyl  nitrile,  (CH)///N,  that  is, 
ammonia  in  which  the  three  atoms  of  hydrogen  are  replaced  by  the  triva- 
lent  radical  methenyl. 

Hydrocyanic  acid  may  be  prepared  in  a  state  of  purity,  and  anhydrous, 
by  the  following  process:  A  long  glass  tube,  filled  with  dry  mercuric  cyan- 
ide, is  connected  by  one  extremity  with  an  arrangement  for  furnishing  dry 
sulphuretted  hydrogen  gas,  while  a  narrow  tube  attached  to  the  other  end 
is  made  to  pass  into  a  narrow-necked  phial  plunged  into  a  freezing  mix- 
ture. Gentle  heat  is  applied  to  the  tube,  the  contents  of  which  suifer  de- 
composition in  contact  with  the  gas,  mercuric  sulphide  and  hydrogen  cyan- 
ide being  produced :  the  latter  is  condensed  in  the  receiver  to  the  liquid 
form.  A  little  of  the  mercuric  cyanide  should  be  left  undecomposed,  to 
avoid  contamination  of  the  product  with  sulphuretted  hydrogen.  The  pure 
acid  is  a  thin,  colorless,  and  exceedingly  volatile  liquid,  which  has  a  den- 
sity of  0-7058  at  7-2°  C.  (45°  F.),  boils  at  26-1°  C.  (79°  F.),  and  solidities, 
when  cooled,  to  — 18°  C.  ( — 0-4°  F.) ;  its  o  lor  is  very  powerful  and  most 
characteristic,  much  resembling  that  of  peach-blossoms  or  bitter-almond 
oil ;  it  has  a  very  feeble  acid  reaction,  and  mixes  with  water  and  alcohol 
in  all  proportions.  In  the  anhydrous  state  this  substance  constitutes  one 
of  the  most  formidable  poisons  known,  and  even  when  largely  diluted  with 
water,  its  effects  upon  the  animal  system  are  exceedingly  energetic:  it  is 
employed,  however,  in  medicine,  in  very  small  doses.  The  inhalation  of 
the  vapor  should  be  carefully  avoided  in  all  experiments  in  which  hydro- 
cyanic acid  is  concerned,  as  it  produces  headache,  giddiness,  and  other 
disagreeable  symptoms:  ammonia  and  chlorine  are  the  best  antidotes. 

The  acid  in  its  pure  form  can  scarcely  be  preserved :  even  when  enclosed 
in  a  carefully  stopped  bottle,  it  is  observed  after  a  very  short  time  to 
darken,  and  eventually  to  deposit  a  black  substance  containing  carbon, 
nitrogen,  and  perhaps  hydrogen :  ammonia  is  formed  at  the  same  time,  and 
many  other  products.  Light  favors  this  decomposition.  Even  in  a  dilute 
condition  it  is  apt  to  decompose,  becoming  brown  and  turbid,  but  not  al- 
'ways  with  the  same  facility,  some  samples  resisting  change  for  a  great 
length  of  time,  and  then  suddenly  solidifying  to  a  brown,  pasty  mass  in  a 
few  weeks. 

When  hydrocyanic  acid  is  mixed  with  concentrated  mineral  acids,  hydro- 
chloric acid,  for  example,  the  whole  solidifies  to  a  crystalline  paste  of  sal- 
ammoniac  and  formic  acid : 

CNH        +        2H20        =        NH3        +        CH,02. 

On  the  other  hand,  when  dry  ammonium  formate  is  heated  to  200°,  it  is 
almost  entirely  converted  into  hydrocyanic  acid  and  water. 

Aqueous  solution  of  hydrocyanic  acid  may  be  prepared  by  various  means. 
The  most  economical,  and  by  far  the  best,  where  considerable  quantities 
are  wanted,  is  to  decompose  yellow  potassium  ferrocyanide  at  boiling  heat 
with  dilute  sulphuric  acid.  For  example,  500  grains  of  the  powdered  fer- 
rocyanide may  be  dissolved  in  four  or  five  ounces  of  warm  water,  and  in- 
troduced into  a  capacious  flask  or  globe,  connected  by  a  perforated  cork 
and  wide  bent  tube  with  a  Liebig's  condenser  well  supplied  with  cold  wa- 
ter ;  300  grains  of  oil  of  vitriol  are  diluted  with  three  or  four  times  as 
much  water  and  added  to  the  contents  of  the  flask;  and  the  distillation  is 
carried  on  till  about  half  the  liquid  has  distilled  over,  after  which  the  pro- 
cess may  be  interrupted.  The  residue  in  the  retort  is  a  white  or  yellow 
59* 


702  CYANOGEN    COMPOUNDS. 

mass,  consisting  of  potassio-ferrous  ferrocyanide  (see  p.  707),  mixed  with 
potassium  sulphate : 

2K4Fe"Cye    -)-     SS04H2    =     GHCy     +     K2Fe"2Cy6     +     3S04K2 
Potassium  Hydrogen      Hydrogen          Potassio-  Potassium 

ferrocyanide.          sulphate.         cyanide.  ferrous  sulphate. 

ferrocyanide. 

When  hydrocyanic  acid  is  wanted  for  the  purposes  of  pharmacy,  it  is 
best  to  prepare  a  strong  solution  in  the  manner  above  described,  and  then, 
having  ascertained  its  exact  strength,  to  dilute  it  with  pure  water  to  the 
standard  of  the  Pharmacopoeia,  viz.,  2  per  cent,  of  real  acid.  This  exami- 
nation is  best  made  by  precipitating  with  excess  of  silver  nitrate  a  known 
weight  of  the  acid  to  be  tried,  collecting  the  insoluble  silver  cyanide  upon 
a  small  filter  previously  weighed,  washing,  drying,  and  lastly  reweighing 
the  Avhole.  From  the  weight  of  the  cyanide  that  of  the  hydrocyanic  acid 
can  be  easily  calculated,  a  molecule  of  the  one  (CNAg=134)  corresponding 
to  a  molecule  of  the  other  (CNH=27) ;  or  the  weight  of  the  silver  cyanide 
may  be  divided  by  5,  which  will  give  a  close  approximation  to  the  truth. 

Another  very  good  method  for  determining  the  amount  of  hydrocyanic 
acid  in  a  liquid  has  been  suggested  by  Liebig.  It  is  based  upon  the  pro- 
perty possessed  by  potassium  cyanide  of  dissolving  a  quantity  of  silver 
cyanide  sufficient  to  produce  with  it  a  double  cyanide  containing  equivalent 
quantities  of  silver  cyanide  and  potassium  cyanide  (KCy  .  AgCy).  Hence 
a  solution  of  hydrocyanic  acid,  which  is  supersaturated  with  potash,  and 
mixed  with  a  few  drops  of  solution  of  common  salt,  will  not  yield  a  perma- 
nent precipitate  with  silver  nitrate  before  the  whole  of  the  hydrocyanic 
acid  is  converted  into  the  above  double  salt.  If  we  know  the  amount  of 
silver  in  a  given  volume  of  the  nitrate  solution,  it  is  easy  to  calculate  the 
quantity  of  hydrocyanic  acid :  for  this  quantity  will  stand  to  the  amount 
of  silver  in  the  nitrate  consumed,  as  2  molecules  of  hydrocyanic  acid  to  1 
atom  of  silver,  i.  e. : 

108  :  54  =r  silver  consumed  :  x. 

It  is  a  common  remark,  that  the  hydrocyanic  acid  made  from  potassium 
ferrocyanide  keeps  better  than  that  made  by  other  means.  The  cause  of 
this  is  ascribed  to  the  presence  of  a  trace  of  mineral  acid.  Everitt  found 
that  a  few  drops  of  hydrochloric  acid,  added  to  a  large  bulk  of  the  pure 
dilute  acid,  preserved  it  from  decomposition,  while  another  portion,  not  so 
treated,  became  completely  spoiled. 

A  very  convenient  process  for  the  extemporaneous  preparation  of  an 
acid  of  definite  strength,  is  to  decompose  a  known  quantity  of  potassium 
cyanide  with  solution  of  tartaric  acid  :  100  grains  of  crystallized  tartaric 
acid  in  powder,  44  grains  of  potassium  cyanide,  and  2  measured  ounces  of 
distilled  water,  shaken  up  in  a  phial  for  a  few  seconds,  and  then  left  at 
rest,  in  order  that  the  precipitate  may  subside,  will  yield  an  acid  of  very 
nearly  the  required  strength.  A  little  alcohol  may  be  added  to  complete 
the  separation  of  the  cream  of  tartar:  no  nitration  or  other  treatment  need 
be  employed. 

The  production  of  hydrocyanic  acid  from  bitter  almonds  has  been  already 
mentioned  in  connection  with  the  history  of  this  volatile  oil.  Bitter  al- 
monds, the  kernels  of  plums  and  peaches,  the  seeds  of  the  apple,  the  leaves 
of  the  cherry-laurel,  atid  various  other  parts  of  plants  belonging  to  the 
great  natural  order  Rosacece,  yield  on  distillation  with  water  a  sweet-smell- 
ing liquid  containing  hydrocyanic  acid.  This  is  probably  clue  in  all  cases 
to  the  decomposition  of  amygdalin  under  the  influence  of  emulsin  or  synap- 
tase  present  in  the  organic  structure  (p.  579).  Hydrocyanic  acid  exists 
ready  formed  to  a  considerable  extent  in  the  juice  of  the  bitter  cassava. 


METALLIC    CYANIDES.  703 

The  presence  of  hydrocyanic  acid  is  detected  with  the  utmost,  ease:  its 
remarkable  odor  and  high  degree  of  volatility  almost  sufficiently  charac- 
terize it.  With  solution  of  silvervnitrate  it  gives  a  dense  curdy  white  pre- 
cipitate, much  resembling  the  chloride,  but  differing  from  that  substance 
in  not  blackening  so  readily  by  light,  in  being  soluble  in  boiling  nitric  acid, 
and  in  suffering  complete  decomposition  when,  heated  in  the  dry  state,  me- 
tallic silver  being  left:  the  chloride  under  the  same  circumstances  merely 
fuses,  but  undergoes  no  chemical  change.  The  production  of  Prussian 
blue  by  "  Scheele's  test"  is  an  excellent  and  most  decisive  experiment,  which 
may  be  made  with  a  very  small  quantity  of  the  acid.  The  liquid  to  be  ex- 
amined is  mixed  with  a  few  drops  of  solution  of  ferrous  sulphate  and  an 
excess  of  caustic  potash,  and  the  whole  exposed  to  the  air  for  10  or  15min- 
utes,  with  agitation,  whereby  the  ferrous  salt  is  partly  converted  into  ferric 
salt:  hydrochloric  acid  is  then  added  in  excess,  which  dissolves  the  iron 
oxide,  and,  if  hydrocyanic  acid  be  present,  leaves  Prussian  blue  as  an 
insoluble  powder.  The  reaction  will  be  explained  in  connection  with  the 
ferrocyanides  (p.  707). 

Another  very  delicate  test  for  hydrocyanic  acid  will  be  mentioned  in  con- 
nection with  sulphocyanic  acid. 

Metallic  Cyanides.  —  The  most  important  of  the  metallic  cyanides  arc  the 
following :  they  bear  the  most  perfect  analogy  to  the  haloid  salts. 

POTASSIUM  CYANIDE,  CNK  or  KCy.  —  Potassium  heated  in  cyanogen  gas, 
takes  fire  and  burns  in  a  very  beautiful  manner,  yielding  potassium  cy- 
anide:  the  same  substance  is  produced  when  potassium  is  heated  in  the  va- 
por of  hydrocyanic  acid,  hydrogen  being  liberated.  When  pure  nitrogen 
gas  is  transmitted  through  a  white-hot  tube  containing  a  mixture  of  potas- 
sium carbonate  and  charcoal,  a  small  quantity  of  potassium  cyanide  is 
formed,  which  settles  on  the  cooler  portions  of  the  tube  as  a  white  amor- 
phous powder:  carbon  monoxide  is  at  the  same  time  evolved.*  If  azotized 
organic  matter  of  any  kind,  capable  of  furnishing  ammonia  by  destructive 
distillation,  as  horn-shavings,  parings  of  hides,  &c.,  be  heated  to  redness 
with  potassium  carbonate  in  a  close  vessel,  a  very  abundant  production  of 
potassium  cyanide  results,  which  cannot,  however,  be  advantageously  ex- 
tracted by  direct  means,  but  in  practice  is  always  converted  into  ferrocy- 
anide,  which  is  a  much  more  stable  substance,  and  crystallizes  better. 

There  are  several  methods  by  which  potassium  cyanide  may  be  prepared 
for  use.  It  may  be  made  by  passing  the  vapor  of  hydrocyanic  acid  into  a 
cold  alcoholic  solution  of  potash :  the  salt  is  then  deposited  in  the  crystal- 
line form,  and  may  be  separated  from  the  liquid,  pressed,  and  dried.  Po- 
tassium ferrocyanide,  heated  to  whiteness  in  a  nearly  close  vessel,  evolves 
nitrogen  and  other  gases,  .and  leaves  a  mixture  of  carbon,  iron  carbide,  and 
potassium  cyanide,  which  latter  salt  is  not  decomposed  unless  the  temper- 
ature is  excessively  high.  Mr.  Donovan  recommends  the  use  in  this  pro- 
cess of  a  wrought-iron  mercury-bottle,  which  is  to  be  half  filled  with  the 
ferrocyanide,  and  arranged  in  a  good  air-furnace  capable  of  giving  the 
requisite  degree  of  heat;  a  bent  iron  tube  is  fitted  to  the  mouth  of  the 
bottle  and  made  to  dip  half  an  inch  into  a  vessel  of  water:  this  serves  to 
give  exit  to  the  gas.  The  bottle  is  gently  heated  at  first,  but  the  tem- 
perature is  ultimately  raised  to  whiteness.  When  no  more  gas  issues,  the 
tube  is  stopped  with  a  cork,  and,  when  the  whole  is  quite  cold,  the  bottle 
is  cut  asunder  in  the  middle  by  means  of  a  chisel  and  sledge-hammer,  and 
the  pure  white  fused  salt  carefully  separated  from  the  black  spongy  mass 

*  According  to  recent  experiments  by  MM.  Marirwritte  and  d"  Sourdeval.  the  formation  of 
cyanide  appears  to  be  more  abundant  if  the  ]>ot;ish  lie  replaced  l>y  baryta.  If  the  barium 
cyanide  thus  formed  he  exposed  to  a  stream  of  superheated  steam  at  :;<to°  0.,  the,  nitrogen  of 
tlie  salt  is  eliminated  in  the  form  of  ammonia.  .Mar.tcuerit  teand  (!••  Sonrdeval  recommend  this 
process  as  a  method  of  preparing  ammonia  by  means  of  atmospheric  nitrogen. 


704  CYANOGEN    COMPOUNDS. 

below,  and  preserved  in  a  well-stopped  bottle  :  the  black  substance  con- 
tains 'much  cyanide,  which  may  be  extracted  by  a  little  cold  water.  It 
would  be  better,  perhaps,  in  the  foregoing  process,  to  deprive  the  potassium 
ferrocyanide  of  its  water  of  crystallization  before  introducing  it  into  the 
iron  vessel. 

Liebig  has  published  a  very  easy  and  excellent  process  for  making  potas- 
sium cyanide,  which  does  not,  however,  yield  it  pure,  but  mixed  with 
potassium  cyanate.  For  most  of  the  applications  of  potassium  cyanide, 
electro-plating  and  gilding,  for  example,  for  which  a  considerable  quan- 
tity is  now  required,  this  impurity  is  of  no  consequence.  Eight  parts  of 
potassium  ferrocyanide  are  rendered  anhydrous  by  gentle  heat,  and  inti- 
mately mixed  with  3  parts  of  dry  potassium  carbonate :  this  mixture  is 
thrown  into  a  red-hot  earthen  crucible  and  kept  in  fusion,  with  occasional 
stirring,  until  gas  ceases  to  be  evolved,  and  the  fluid  portion  of  the  mass 
becomes  colorless.  The  crucible  is  left  at  rest  for  a  moment,  and  then  the 
clear  salt  decanted  from  the  heavy  black  sediment  at  the  bottom,  which  is 
principally  metallic  iron  in  a  state  of  minute  division.  The  reaction  is 
represented  by  the  equation : 

K4Fe"Cy6     +      C03K2     =     5KCy     -f     CyKO  +     Fe  -f     C02. 

Ferrocyanide.     Carbonate.      Cyanide.        Cyanate. 

The  product  may  be  advantageously  used,  instead  of  potassium  ferrocy- 
anide, in  the  preparation  of  hydrocyanic  acid,  by  distillation  with  diluted 
oil  of  vitriol. 

Potassium  cyanide  forms  colorless,  cubic  or  octohedral  crystals,  deli- 
quescent in  the  air,  and  exceedingly  soluble  in  water :  it  dissolves  in  boil- 
ing alcohol,  but  separates  in  great  measure  on  cooling.  It  is  readily 
fusible,  and  undergoes  no  change  at  a  moderate  red  or  even  white  heat, 
when  excluded  from  air;  otherwise,  oxygen  is  absorbed  and  the  cyanide 
becomes  cyanate.  Its  solution  always  has  an  alkaline  reaction,  and  when 
exposed  to  the  air  exhales  the  odor  of  hydrocyanic  acid:  it  is  decomposed 
by  the  feeblest  acids,  even  the  carbonic  acid  of  the  atmosphere,  and  when 
boiled  in  a  retort  is  slowly  converted  into  potassium  formate,  with  separa- 
tion of  ammonia.  This  salt  is  anhydrous:  it  is  said  to  be  as  poisonous  as 
hydrocyanic  acid  itself. 

Potassium  cyanide  has  been  derived  from  a  curious  and  unexpected 
source.  In  some  of  the  iron  furnaces  in  Scotland,  where  raw  coal  is  used 
for  fuel  with  the  hot  blast,  a  saline-looking  substance  is  occasionally  ob- 
served to  issue  in  a  fused  state  from  the  tuyere-holes  of  the  furnace,  and 
concrete  on  the  outside.  This  proved,  on  examination  by  Dr.  Clark,  to  be 
principally  potassium  cyanide. 

SODIUM  CYANIDE,  NaCy,  is  a  very  soluble  salt,  corresponding  closely 
with  the  foregoing,  and  obtained  by  similar  means. 

AMMONIUM  CYANIDE,  NH4Cy.  —  This  is  a  colorless,  crystallizable,  and 
very  volatile  substance,  prepared  by  distilling  a  mixture  of  potassium 
cyanide  and  sal-ammoniac  ;  or  by  mingling  the  vapor  of  anhydrous  hydro- 
cyanic acid  with  ammoniacal  gas ;  or,  lastly,  according  to  the  observa- 
tions of  M.  Langlois,  by  passing  ammonia  over  red-hot  charcoal.  It  is 
very  soluble  in  water,  subject  to  spontaneous  decomposition,  and  is  slightly 
poisonous. 

MERCURIC  CYANIDE,  (CN)2Hg",  or  Hg"Cy2.— One  of  the  most  remark- 
able properties  of  cyanogen  is  its  powerful  attraction  for  certain  of  the 
less  oxidable  metals,  as  silver,  and  more  particularly  for  mercury  and  pal- 
ladium. Dilute  hydrocyanic  acid  dissolves  finely-powdered  mercuric 
oxide  with  the  utmost  ease:  the  liquid  loses  all  odor,  and  yields  on  evapo- 
ration crystals  of  mercuric  cyanide.  Potassium  cyanide  is  in  like  manner 
decomposed  by  mercuric  oxide,  potassium  hydrate  being  produced.  Mer- 


SILVER  —  IRON    CYANIDES.  705 

curie  cyanide  is  generally  prepared  from  common  potassium  ferrocy- 
anide  ;  2  parts  of  the  salt  are  dissolved  in  15  parts  of  hot  water,  and  3 
parts  of  dry  mercuric  sulphate  afe  added;  the  whole  is  boiled  for  fifteen 
minutes,  and  filtered  hot  from  the  iron  oxide,  which  separates.  The  solu- 
tion, on  cooling,  deposits  the  mercuric  cyanide  in  crystals.  Mercuric 
cyanide  forms  white,  translucent  prisms,  much  resembling  those  of  corro- 
sive sublimate  :  it  is  soluble  in  8  parts  of  cold  water,  and  in  a  much  smaller 
quantity  at  a  higher  temperature,  and  also  in  alcohol.  The  solution  has  a 
disagreeable  metallic  taste,  is  very  poisonous,  and  is  not  precipitated  by 
alkalies.  Mercuric  cyanide  is  used  in  the  laboratory  as  a  source  of  cyan- 
ogen. 

SILVER  CYANIDE,  AgCy,  has  been  already  described,  —  Zinc  cyanide, 
ZnCy2,  is  a  white  insoluble  powder,  prepared  by  mixing  zinc  acetate  with 
hydrocyanic  acid.  —  Cobalt  cyanide,  CoCy^,  is  obtained  by  similar  means: 
it  is  dirty-white,  and  insoluble.  —  Palladium  cyanide,  PdCy2,  forms  a  yel- 
lowish-white precipitate  when  the  chloride  of  that  metal  is  mixed  with  a 
soluble  cyanide,  including  that  of  mercury.  —  Auric  cyanide,  AuCy3,  is 
yellowish-white  and  insoluble,  but  freely  dissolved  by  solution  of  potas- 
sium cyanide. 

IRON  CYANIDES.  —  These  compounds  are  scarcely  known  in  the  separate 
state,  on  account  of  their  great  tendency  to  form  double  salts.  On  adding 
potassium  cyanide  to  a  ferrous  salt,  a  yellowish-red  flocculent  precipitate 
is  formed,  consisting  chiefly  of  ferrous  cyanide,  FeCy2,  but  always  con- 
taining a  certain  quantity  of  potassium  cyanide,  and  dissolved  as  ferrocy- 
anide  by  excess  of  that  salt.  Ferric  cyanide,  Fe2Cy6,  is  known  only  in 
solution.  Pelouze  obtained  an  insoluble  green  compound  containing 
Fc3Cy8,  or  FeCy2.  FeaCy6,  by  passing  chlorine  gas  into  a  boiling  solution 
of  potassium  ferrocyanide. 

The  iron  cyanides  unite  with  other  metallic  cyanides,  forming  two  very 
important  groups  of  compounds,  called  ferrocyanides  and  ferricyanides,  the 
composition  of  which  may  be  illustrated  by  the  respective  potassium-salts  : 


Ferrocyanide,  E^Fe^Cy^  or  4KCy  .  Fe"Cy2. 
Ferricyanide,   I^Fe^'Cy,;,  or  SKCy  . 


It  will  be  seen  from  these  formulae,  that  the  ferro-  and  ferricyanides 
diifer  from  one  another  only  by  one  atom  of  univalent  metal,  and,  accord- 
ingly, it  is  found  that  the  former  may  be  converted  into  the  latter,  by  the 
action  of  oxidizing  (metal-abstracting)  agents,  and  the  latter  into  the  for- 
mer by  the  action  of  reducing  (metal-adding)  agents.  Thus  potassium 
ferrocyanide  is  easily  converted  into  the  ferricyanide  by  the  action  of  chlo- 
rine, and  many  double  ferrocyanides  may  be  formed  from  ferricyanides  by 
the  action  of  alkalies  in  presence  of  a  reducing  agent  ;  thus  potassium 
ferricyanide,  K;JFe///Cy6,  is  easily  converted  into  ammonio-tripotassic  fer- 
rocyanide, (NII4)K3Fe//Cy6,  by  the  action  of  ammonia  in  presence  of  glu- 
cose.f 

*  Strictly  speaking,  the  formula  of  potassium  ferricyanide  should  be  6KCy.Fe'"2Cy6  (see 
IRON,  p.  JW);  l.ut,  lor  comparing  the  composition  of  tlic  ferricyanides  with  that  of  the  ferro- 
cyanides, tlie  simpler  formula  al>ove  given  is  more  convenient. 

f  The  ferrocyanides  and  ferricyanides  are  sometimes  regarded  as  salts  of  peculiar  com- 
pound radicals  containing  iron,  vi/.,  .furrocyanngen,  Fe"Cyc,  and  t\'rri<-ii<nxy?.>i.  Fe'"Cy6,  the 
first  being  quadrivalent,  the  second  trivalent;  but  there  is  nothing  gained'  by  this  assump- 
tion. For  a  discussion  of  the  formulae  of  these  salts,  and  of  the  double  cyanides  iu  general 
see  Watts's  Dictionary  of  Chemistry,  vol.  ii.  p.  201. 


706  CYANOGEN    COMPOUNDS. 

Ferrocyanides. 

POTASSIUM  FERROCYANIDE,  K4Fe"Cy6,  or  4KCy  .  Fe//Cya,  commonly 
called  yellow  prussiate  of  potash.  —  This  important  salt  is  formed: — 1.  By 
digesting  precipitated  ferrous  cyanide  in  aqueous  solution  of  potassium 
cyanide. — 2.  By  digesting  ferrous  hydrate  with  potassium  cyanide,  potash 
being  formed  at  the  same  time : 

6KCy     +     Fe"H202     ==     2KHO     -f-     K4Fe"Cy6. 

3.  Ferrous  cyanide  with  aqueous  potash : 

3F"Cy2     4.     4KHO     =     2Fe"H202     +     K4Fe"Cy6. 

4.  Aqueous  potassium  cyanide  with  metallic  iron :  if  the  air  be  excluded, 
hydrogen  is  evolved : 

GKCy     +     Fe     +     20H2    =     K4Fe"Cye     -f     2KHO     +     H2; 

but  if  the  air  has  access  to  the  liquid,  oxygen  is  absorbed,  and  no  hydrogen 
is  evolved : 

6KCy     +     Fe     +     OH2     +     0     =     K4Fe"Cy6     +     2KHO. 

5.  Ferrous  sulphide  with  aqueous  potassium  cyanide : 

•      GKCy     +     Fe"S     =     K2S     -f     K4Fe"Cy6. 

6.  Any  soluble  ferrous  salt  with  potassium  cyanide  ;  e.  g. : 

GKCy     -f     S04Fe"     =     S04K2     -f     K4Fe"Cy6. 

Potassium  ferrocyanide  is  manufactured  on  the  large  scale  by  the  follow- 
ing process:  — Dry  refuse  animal  matter  of  any  kind  is  fused  at  a  red  heat 
with  impure  potassium  carbonate  and  iron  filings,  in  a  large  iron  vessel, 
from  which  the  air  should  be  excluded  as  much  as  possible;  potassium 
cyanide  is  generated  in  large  quantity.  The  melted  mass  is  afterwards 
treated  with  hot  water,  which  dissolves  out  the  cyanide  and  other  salts,  the 
cyanide  being  quickly  converted  by  the  oxide  or  sulphide*  of  iron  into 
ferrocyanide.  The  filtered  solution  is  evaporated,  and  the  first-formed 
crystals  are  purified  by  re-solution.  If  a  sufficient  quantity  of  iron  be  not 
present,  great  loss  is  incurred  by  the  decomposition  of  the  cyanide  into  po- 
tassium carbonate  and  ammonia. 

A  new  process  for  the  preparation  of  potassium  ferrocyanide  has  lately 
been  proposed  by  M.  Gelis.  It  consists  in  converting  carbon  bisulphide 
into  ammonium  sulphocarbonate  by  agitating  it  with  ammonium  sulphide: 
CS2  -^  (NH4)2S  =i  (NH4)2CS3,  and  heating  the  product  thus  obtained  with 
potassium  sulphide,  whereby  potassium  sulphocyanate  (p  717)  is  formed, 
with  evolution  of  ammonium  sulphide  and  hydrogen  sulphide : 

2(NH4)2CS3     -f     RjS     =    2CNSK     -f     2(NH4)HS     -f     3H2S. 

The  potassium  sulphocyanate  is  dried,  mixed  with  finely  divided  metallic 
iron,  and  heated  for  a  short  time  in  a  closed  iron  vessel  to  dull  redness, 
whereby  the  mixture  is  converted  into  potassium  ferrocyanide,  potassium 
sulphide,  and  iron  sulphide : 

6CNSK     -f     Fe6     =     K4Fe"Cy6     -f    5Fe"S     -f     K2S. 

By  treatment  with  water,  the  sulphide  and  ferrocyanide  of  potassium  are 
dissolved,  and  on  evaporation  the  ferrocyanide  is  obtained  in  crystals.  It 
remains  to  be  seen  whether  this  ingenious  process  is  capable  of  being 
carried  out  upon  a  large  scale. 

*  The  sulphur  is  derived  from  the  reduced  sulphate  of  the  crude  pearl-ashes  and  the  animal 
substances  used  in  the  manufacture. 


FERROCYANIDES.  707 

Potassium  ferrocyanide  forms  large,  transparent,  yellow  crystals,  K4Fe7/ 
Cy6 . 3  Aq.,  derived  from  an  octahedron  with  a  squ«are  base:  they  cleave 
with  facility  in  a  direction  parallel  to  the  base  of  the  octohedron,  and  are 
tough  and  difficult  to  powder.  They  dissolve  in  4  parts  of  cold  and  2  parts 
of  boiling  water,  and  are  insoluble  in  alcohol.  They  are  permanent  in  the 
air,  and  have  a  mild  saline  taste.  The  salt  has  no  poisonous  -properties, 
and,  in  small  doses  at  least,  is  merely  purgative.  Exposed  to  a  gentle  heat, 
it  loses  8  molecules  of  -water,  and  becomes  anhydrous :  at  a  high  tempera- 
ture it  yields  potassium  cyanide,  iron  carbide,  arid  various  gaseous  pro- 
ducts; if  air  be  admitted,  the  cyanide  becomes  cyanate. 

Potassium  ferrocyanide  is  a  chemical  reagent  of  great  value;  when  mixed 
in  solution  with  neutral  or  slightly  acid  salts  of  the  heavy  metals,  it  gives 
rise  to  precipitates  which  very  frequently  present  highly  characteristic 
colors.  In  most  of  these  compounds  the  potassium  is  simply  displaced 
by  the  new  metal :  the  beautiful  brown  ferrocyanide  of  copper  contains, 
for  example,  Cu//2Fe//Cy6,  or  2Cu"Cy2 .  Fe"Cy2,  and  that  of  lead,  Pb'^ 
Fe"Cy6. 

With  ferrous  salts,  potassium  ferrocyanide  gives  a  precipitate  which  is 
perfectly  white,  if  the  air  be  excluded  and  the  solution  is  quite  free  from 
ferric  salt,  but  quickly  turns  blue  on  exposure  to  the  air.  It  consists  of 
potassio-ferrous  ferrocyanide,  K2Fe//2Cy6,  or  potassium  ferrocyanide  having 
half  the  potassium  replaced  by  iron.  The  same  salt  is  produced  in  the 
preparation  of  hydrocyanic  acid  by  distilling  potassium  ferrocyanide  with 
dilute  sulphuric  acid  (p.  701). 

When  a  soluble  ferrocyanide  is  added  to  the  solution  of  &  ferric  salt,  a 
deep  blue  precipitate  is  formed,  consisting  of  ferric  ferrocyanide,  Fe7Cy18,  or 
Fe'^Fe'^Cjis'  or  4Fe///Cy3  .  3Fe//Cy2,  which  in  combination  with  18  mole- 
cules of  water  constitutes  ordinary  Prussian  blue.  This  beautiful  pigment 
is  best  prepared  by  adding  potassium  ferrocyanide  to  ferric  nitrate  or 
chloride : 

3K4Fe"Cy6    -f     2Fe'"2Cle     =     12KC1    +     Fe7Cy18. 

It  is  also  formed  by  precipitating  a  mixture  of  ferrous  and  ferric  salts  with 
potassium  cyanide : 

18KCy     +     3Fe"Cla     +     2Fe'"2Cl6    =    18KC1     +     Fe7Cy18. 

This  reaction  explains  Scheele's  test  for  prussic  acid  (p.  703).  Prussian 
blue  is  also  formed  by  the  action  of  air,  chlorine-water,  and  other  oxidizing 
agents,  on  potassio-ferrous  ferrocyanide  ;  probably  thus : 

6K,Fe"sCy.     +     03     =        Fe7Cy18     +     8K4Fe"Cye     +     Fe203. 

It  is  chiefly  by  this  last  reaction  that  Prussian  blue  is  prepared  on  the 
large  scale,  potassium  ferrocyanide  being  first  precipitated  by  ferrous  sul- 
phate, and  the  resulting  white  or  light  blue  precipitate  either  left  to  oxidize 
by  contact  with  the  air,  or  subjected  to  the  action  of  nitric  acid,  chlorine, 
hypochlorites,  chromic  acid,  &c.  The  product,  however,  is  not  pure  ferric 
ferrocyanide:  for  it  is  certain  that  another  and  simpler  reaction  takes 
place  at  the  same  time,  by  which  the  potassio-ferrous  ferrocyanide,  (I^Fe") 
Fe/xCy6,  is  converted,  by  abstraction  of  an  atom  of  potassium,  into  potas- 
sio-ferrous ferricyanidc,  (KFe//)Fe///Cy6,  which  also  possesses  a  fine  deep- 
blue  color.  Commercial  Prussian  blue  is,  therefore,  generally  a  mixture 
of  this  compound  with  ferric  ferrocyanide,  Fe///4Fe//3Cy]8,  the  one  or  the 
other  predominating  according  to  the  manner  in  which  the  process  is  con- 
ducted. 

Prussian  blue  in  the  moist  state  forms  a  bulky  precipitate,  which  shrinks 
to  a  comparatively  small  compass  when  well  washed  and  dried  by  a  gentle 
heat.  In  the  dry  state  it  is  hard  and  brittle,  much  resembling  in  appear- 


708  CYANOGEN    COMPOUNDS. 

ance  the  best  indigo :  the  freshly  fractured  surfaces  have  a  beautiful  cop- 
per-red lustre,  similar  to  that  produced  by  rubbing  indigo  with  a  hard 
body.  Prussian  blue  is  quite  insoluble  in  water  and  dilute  acids,  with  the 
exception  of  oxalic  acid,  in  a  solution  of  which  it  dissolves,  forming  a  deep- 
blue  liquid,  which  is  sometimes  used  as  ink :  concentrated  oil  of  vitriol 
converts  it  into  a  white,  pasty  mass,  which  again  becomes  blue  on  addition 
of  water.  Alkalies  destroy  the  color  instantly:  they  dissolve  out  a  ferro- 
cyanide,  and  leave  ferric  oxide.  Boiled  with  water  and  mercuric  oxide,  it 
yields  a  cyanide  of  the  metal,  and  ferric  oxide.  Heated  in  the  air,  Prus- 
sian blue  burns  like  tinder,  leaving  a  residue  of  ferric  oxide.  Exposed  to 
a  high  temperature  in  a  close  vessel,  it  gives  off  water,  ammonium  cyanide, 
and  ammonium  carbonate,  and  leaves  carbide  of  iron.  It  forms  a  very 
beautiful  pigment,  both  as  oil  and  water  color,  but  has  little  permanency. 

Common  or  basic  Prussian  blue  is  an  inferior  article  prepared  by  pre- 
cipitating a  mixture  of  ferrous  sulphate  and  alum  with  potassium  ferrocy- 
anide,  and  exposing  the  precipitate  to  the  air.  It  contains  alumina,  which 
impairs  the  color,  but  adds  to  the  weight. 

Soluble  Prussian  blue  is  obtained  by  adding  ferric  chloride  to  an  excess 
of  potassium  ferrocyanide  ;  it  is  insoluble  in  the  saline  liquor,  but  soluble 
in  pure  water.  It  has  a  deep  blue  color,  and  probably  consists  of  potassio- 
ferrous  ferricyanide. 

HYDROGEN  FERROCYANIDE  OR,  HYDROFERROCYANIC  ACID,  H4Fe/xCy6,  dis- 
covered by  Mr.  Porrett,  is  prepared  by  decomposing  ferrocyanide  of  lead 
or  copper  suspended  in  water  by  a  stream  of  sulphuretted  hydrogen  gas. 
The  filtered  solution  evaporated  in  a  vacuum  over  oil  of  vitriol,  yields  the 
acid  in  the  solid  form.  If  the  aqueous  solution  be  agitated  with  ether, 
nearly  the  whole  of  the  acid  separates  in  colorless,  crystalline  laminge ;  it 
may  even  be  made  in  large  quantity  by  adding  hydrochloric  acid  to  a  strong 
solution  of  potassium  ferrocyanide  in  water  free  from  air,  and  shaking  the 
whole  with  ether.  The  crystals  may  be  dissolved  in  alcohol,  and  the  acid 
again  thrown  down  by  ether.  Hydroferrocyanic  acid  differs  completely 
from  hydrocyanic  acid :  its  solution  in  water  has  a  powerfully  acid  taste 
and  reaction,  and  decomposes  alkaline  carbonates  with  effervescence :  it 
does  not  dissolve  mercuric  oxide  in  the  cold,  but  when  heat  is  applied,  un- 
dergoes decomposition,  forming  mercuric  cyanide  and  ferrous  cyanide  : 
H4Fe"Cy6  +  2Hg"0  =  2Hg"Cya  +  Fe"Cys  +  20H2;  but  the  ferrous  cy- 
anide is  immediately  oxidized  by  the  excess  of  mercuric  oxide,  with  sepa- 
ration of  metallic  mercury.  In  the  dry  state  the  acid  is  very  permanent, 
but  when  long  exposed  to  the  air  in  contact  with  water,  it  is  entirely  con- 
verted into  Prussian  blue. 

Sodium  ferrocyanide,  Na//Fe//Cy6  .  12  Aq.,  crystallizes  in  yellow  four- 
sided  prisms,  which  are  efflorescent  in  the  air  and  very  soluble. 

Ammonium  ferrocyanide,  (NH4)//Fe//Cy6  .  3  Aq.,  is  isomorphous  with  po- 
tassium ferrocyanide :  it  is  easy  soluble,  and  is  decomposed  by  ebullition. 
Barium  ferrocyanide,  Ba//2Fe//Cy6,  prepared  by  boiling  potassium  ferrocy- 
anide with  a  large  excess  of  barium  chloride,  or  Prussian  blue  with  baryta- 
water,  forms  minute  yellow,  anhydrous  crystals,  which  have  but  a  small  de- 
gree of  solubility  even  in  boiling  water.  The  corresponding  compounds 
of  strontium,  calcium,  and  magnesium  are  more  freely  soluble.  The  ferro- 
cyanides  of  silver,  lead,  zinc,  manganese,  and  bismuth  are  white  and  insoluble  ; 
those  of  nickel  and  cobalt  are  pale-green  and  insoluble ;  and,  lastly,  that  of 
copper  has  a  beautiful  reddish-brown  tint. 

There  are  also  several  double  ferrocyanides.  When,  for  example,  con- 
centrated solutions  of  calcium  chloride  and  potassium  ferrocyanide  are 
mixed,  a  sparingly  soluble  crystalline  precipitate  falls,  containing  K2Cax/ 


FERRICYANIDES.  709 


Ferricyanides. 

These  salts  are  formed,  as  already  observed,  by  abstraction  of  metal  from 
the  ferrocyanides ;  in  other  words,  by  the  action  of  oxidizing  agents. 

POTASSIUM  FERRICYANIDE,  K3Fe//vCy6,  often  called  red  prussiate  of  potash, 
is  prepared  by  slowly  passing  chlorine,  with  agitation,  into  a  somewhat 
dilute  and  cold  solution  of  potassium  ferrocyanide,  until  the  liquid  acquires 
a  deep  reddish-green  color,  and  ceases  to  precipitate  a  ferric  salt.  The 
solution  is  evaporated  until  a  skin  begins  to  form  upon  the  surface,  then 
filtered,  and  left  to  cool ;  and  the  salt  is  purified  by  re-crystallization.  It 
forms  regular,  prismatic,  or  sometimes  tabular  crystals,  of  a  beautiful  ruby- 
red  tint,  permanent  in  the  air,  and  soluble  in  4  parts  of  cold  water:  the 
solution  has  a  dark-greenish  color.  The  crystals  burn  when  introduced 
into  the  flame  of  a  candle,  and  emit  sparks.  The  salt  is  decomposed  by  ex- 
cess of  chlorine,  and  by  deoxidizing  agents,  as  sulphuretted  hydrogen. 

Hydrogen  ferricyanide  is  obtained  in  the  form  of  a  reddish-brown  acid 
liquid,  by  decomposing  lead  ferricyanide  with  sulphuric  acid :  it  is  very 
unstable,  and  is  resolved,  by  boiling,  into  hydrated  ferric  cyanide,  an  in- 
soluble dark-green  powder  containing  Fe2Cy6  .  3  Aq.,  and  hydrocyanic  acid. 
The  ferricyanides  of  sodium,  ammonium,  and  of  the  alkaline  earths,  are  sol- 
uble ;  those  of  most  of  the  other  metals  are  insoluble.  Potassium  ferri- 
cyanide, added  to  a  ferric  salt,  occasions  no  precipitate,  but  merely  a  dark- 
ening of  the  reddish-brown  color  of  the  solution ;  with  ferrous  salts,  on  the 
other  hand,  it  gives  a  deep  blue  precipitate,  consisting  of  ferrous  ferricyanide, 
Fe6Cy,2 .  x  Aq.,  or  Fe//3Fe///2Cy,2 .  x  Aq.,  which,  when  dry,  has  a  brighter 
tint  than  Prussian  blue :  it  is  known  under  the  name  of  TurnbulVs  blue. 
Hence,  potassium  ferricyanide  is  as  delicate  a  test  for  ferrous  salts  as  the 
yellow  ferrocyanide  is  for  ferric  salts. 

COBALTICYANIDES. — This  name  is  applied  to  a  series  of  compounds  analo- 
gous to  the  preceding,  containing  cobalt  in  place  of  iron ;  a  hydrogen-acid 
has  been  obtained,  and  a  number  of  salts,  which  much  resemble  the  ferri- 
cyanides. Several  other  metals  of  the  same  isomorphous  family  are  found 
capable  of  replacing  iron  in  these  compounds. 

NITROPRUSSIDES. — The  action  of  nitric  acid  upon  ferrocyanides  and  fer- 
ricyanides gives  rise  to  the  formation  of  a  very  interesting  series  of  new 
salts,  which  were  discovered  by  Dr.  Playfair.  The  general  formula  of 
these  salts  appears  to  be  M2(NO)Fe//Cy5,  which  exhibits  a  close  relation 
with  those  of  the  ferro-  and  ferricyanides. 

The  formation  of  the  nitroprussides  appears  to  consist  in  the  reduction 
of  the  nitric  acid  to  the  state  of  nitrogen  dioxide  or  nitrosyl,  NO,  which 
replaces  1  molecule  of  metallic  cyanide,  MCy,  in  a  molecule  of  ferricyanide, 
M3Fe///Cy6.  The  formation  of  these  salts  is  attended  by  the  production 
of  a  variety  of  secondary  products,  such  as  cyanogen,  oxamide,  hydrocyanic 
acid,  nitrogen,  carbonic  acid,  &c.  One  of  the  finest  compounds  of  this 
series  is  the  nitroprusside  of  sodium,  Na2(NO)Fe//Cy6.  2  Aq.,  which  is  readily 
obtained  by  treating  2  parts  of  the  powdered  ferrocyanide  with  5  parts  of 
common  -nitric  acid  previously  diluted  with  its  own  volume  of  water.  The 
solution,  after  the  evolution  of  gas  has  ceased,  is  digested  on  the  water-bath, 
until  ferrous  salts  no  longer  yield  a  blue,  but  a  slate-colored  precipitate. 
The  liquid  is  now  allowed  to  cool,  when  much  potassium  nitrate,  and  occa- 
sionally oxamide,  is  deposited  :  it  is  filtered  and  neutralized  with  sodium 
carbonate,  which  yields  a  green  or  brown  precipitate,  and  a  ruby-colored 
filtrate.  This,  on  evaporation,  gives  a  crystallization  of  the  nitrates  of  po- 
tassium and  sodium,  together  with  the  nitroprusside.  The  crystals  of  the 
60 


710  CYANOGEN    COMPOUNDS. 

latter  are  selected  and  purified  by  crystallization  ;  they  are  rhombic  and 
of  a  splendid  ruby  color.  The  soluble  nitroprussides  strike  a  most  beau- 
tiful violet  tint  with  soluble  sulphides.  This  reaction  is  recommended  by 
Playfair  as  the  most  delicate  test  for  alkaline  sulphides. 


ALCOHOLIC  CYANIDES  OR  HYDROCYANIC  ETHERS. 

These  compounds  play  an  important  part  in  organic  chemistry :  we  have 
already  had  occasion  to  notice  them  several  times  in  speaking  of  the  con- 
version of  alcohols  into  acids  containing  a  greater  number  of  carbon-atoms. 

The  cyanides  of  univalent  alcohol-radicals  may  also  be  regarded  as  com- 
pounds of  nitrogen  with  trivalent  radicals :  hence  they  are  often  called 
nilriles ;  thus  : 

Hydrogen  cyanide     II   .  CN  =  (C  H  )'"N  Methenyl  nitrile. 

Methyl  cyanide      C  H3 .  CN  ==  (CgH,)'"!*  Ethenyl  nitrile. 

Ethyl  cyanide         C2H6 .  CN  =  (CgH^^'N  Propenyl  nitrile. 

Propyl  cyanide       C3H7 .  CN  =  (C4H7)//XN  Quartenyl  nitrile. 

Phenyl  cyanide       C6H6 .  CN  =  (CTH6)"'N  Benzonitrile. 

These  alcoholic  cyanides  are  produced: 

1.  By  distilling  a  mixture  of  potassium  cyanide  and  the  potassium-salt 
of  ethylsulphuric  or  a  similar  acid: 

CNK        -f        S04(C2H5)K        =        S04K2        -f        CN .  C2H5 
Potassium  Potassium  Potassium  Ethyl 

cyanide.  ethyl-sulphate.  sulphate.  cyanide. 

2.  By  the  dehydrating  action  of  phosphoric  oxide  on  the  ammonium- 
salts  of   the   corresponding  acids  containing   the  radicals  CnH2n— iO  and 
CnH2n_70;  thus: 

C2H302.NH4         —          20H2          -=         C2H8N 
Ammonium  Ethenyl 

acetate.  nitrile. 

C7H502.NH4         —         20H2        ==          C7H5N 
Ammonium  Benzonitrile. 

benzoate. 

The  bodies  obtained  by  these  two  processes  are  oily  liquids,  exhibiting 
the  same  properties  whether  prepared  by  the  first  or  the  second  method, 
excepting  that  those  obtained  by  the  latter  have  an  aromatic  fragrant  odor, 
whereas  those  prepared  by  the  former  have  a  pungent  and  repulsive  odor, 
due  to  the  presence  of  certain  isomeric  compounds,  to  be  noticed  farther 
on.  Methyl  cyanide,  Ethenyl-nitrile,  or  Acetonitrile,  boils  at  77°  C.  (170°  F.) ; 
Ethyl  cyanide,  or  Propenyl-nitrile,  at  82°  C.  (180°  F.);  Butyl  cyanide,  or 
Valeronitrile,  at  125°-128°  C.  (257°-262°  F.)  ;  Amyl  cyanide,  or  Capronitrile, 
at  146°  C.  (295°  F.);  Phenyl  cyanide,  or  Benzonitrile,  at  190-6°  C.  (375°  F.). 

All  these  cyanides,  when  heated  with  fuming  sulphuric  acid  or  sulphu- 
ric oxide,  imdergo  the  decomposition  already  mentioned  (p.  682),  yielding 
sulpho-acids.  By  heating  with  caustic  potash  or  soda,  they  are  resolved 
into  ammonia  and  the  corresponding  fatty  or  aromatic  acid,  just  as  hydro- 
cyanic acid  similarly  treated  is  resolved  into  ammonia  and  formic  acid ; 
thus: 

CNH         -f          2II20        =         NIT3         -f          CH202 
Hydrogen  Formic 

cyanide.  acid. 


ALCOHOLIC    CYANIDES.  711 

CN.C2H5        +        2H20  NH3         +          C3H602 

Ethyl  Propionic 

cyanide.  acid. 

CN.C6H5        +        2H20  NH3         +          C7H602 

Phenyl  Benzoic  acid, 

cyanide. 

Ethene  cyanide,  (C2H4)//(CN)2,  is  obtained  by  distilling  potassium  cyanide 
with  ethene  bromide : 

C2H4Br2     +     2CNK    =     2KBr     +     C2H4(CN)2. 

It  is  a  crystalline  body,  melting  at  50°,  and  converted  by  alcoholic  potash 
into  ammonia  and  succinic  acid: 

C2H4(CN)2    -f     4H20     =    2NH3    -f     C4H604. 

ISOCYANIUES.  —  On  examining  the  equations  just  given  for  the  decompo- 
sition of  the  alcoholic  cyanides  under  the  influence  of  alkalies,  it  is  easy 
to  see  that  the  reaction  might  be  supposed  to  take  place  in  a  different  way, 
each  cyanide  or  nitrile  yielding,  not  ammonia  and  an  acid  containing  the 
same  number  of  carbon-atoms  as  itself,  but  an  alcoholic  ammonia,  or 
amine,  and  formic  acid  ;  thus : 

CN .  C2H5        -f        2H20        =        NH2C2H5        +        CH202 
Ethyl  Ethyl-  Formic 

cyanide.  amine.  acid. 

In  the  one  case  the  alcohol-radical  remains  united  with  the  carbon,  pro- 
ducing a  homologue  of  formic  acid,  together  with  ammonia;  in  the  other 
it  remains  united  with  the  nitrogen,  producing  a  homologue  of  ammonia, 
together  with  formic  acid. 

A  class  of  cyanides  exhibiting  the  second  of  these  reactions  has  lately 
been  discovered  by  Dr.  Hofmann.*  They  are  obtained  by  distilling  a 
mixture  of  an  alcoholic  ammonia-base  and  chloroform  with  alcoholic  potash ; 
for  example : 

C6H7N        -f        CHC13        =:        3HC1        -f        C7H6N 
Aniline.  Chloro-  Phenyl- 

form.  isocyanide. 

The  potash  serves  to  neutralize  the  hydrochloric  acid  produced,  which 
would  otherwise  quickly  decompose  the  isocyanide.  Phenyl  isocyanide, 
when  freed  from  excess  of  aniline  by  oxalic  acid,  then  dried  with  oaustic 
potash  and  rectified,  is  an  oily  liquid,  green  by  transmitted,  blue  by  re- 
flected light,  and  having  an  intolerably  pungent  and  suffocating  odor.  It 
is  i^omeric  with  benzonitrile,  and  is  resolved  by  boiling  with  dilute  acids 
into  formic  acid  and  aniline  : 

C7H6N        -f        2H20         =         CH202        -f        C6H7N. 

It  is  a  remarkable  fact  that,  whereas  the  normal  alcoholic  cyanides  are 
easily  decomposed  by  boiling  alkaline  solutions,  the  isocyanides  are 
scarcely  altered  by  alkalies,  but  are  easily  hydrated  under  the  influence 
of  acids. 

The  isocyanides  of  ethyl  and  amyl  have  been  obtained  by  similar  pro- 
cesses; also  by  the  action  of  ethylic  and  amylic  iodides  on  silver  cyanide. 
They  resemble  the  phenyl  compound  in  their  reactions,  and  are  also  char- 
acterized by  extremely  powerful  odors.  The  repulsive  odor  possessed  by 
the  normal  alcoholic  cyanides  when  prepared  by  distilling  potassium  cya- 

*  Proceedings  of  the  Royal  Society,  xvi.  144, 148, 150. 


712 


CYANOGEN"    COMPOUNDS. 


nide  with  the  ethyl-sulphate,  appears  to  be  due  to  the   presence  of  small 
quantities  of  these  isocyanides. 

The  difference  of  constitution  between  the  normal  cyanides  and  the  iso- 
cyanides may  be  represented  by  the  following  formulae,*  taking  the  methyl 
compounds  for  example: 


. 

Cyanide.  Isocyanide. 

In  the  isocyanide  the  carbon  belonging  to  the  alcohol-radical  is  united  di- 
rectly with  the  nitrogen;  in  the  isocyanide,  only  through  the  medium  of 
the  carbon  belonging  to  the  cyanogen. 

This  difference  of  structure  may  perhaps  account  for  the  difference  in  the 
reactions  of  the  cyanides  and  isocyanides  under  the  influence  of  hydrating 
agents  ;  thus  : 


CH 


Methyl  cyanide. 


2H20        =        NH3 


CH3 
" 


Ammonia. 


2H20        = 


Methyl  isocyanide. 


Methylamine. 


rci 

\  0' 
(01 

;tic  a 

fH 

1° 
1 01 


OH 

Acetic  acid. 


OH 
Formic  acid. 


Cyanic  and  Cyanuric  Acids. 

These  are  two  remarkable  polymeric  bodies,  related  in  a  very  close  and 
intimate  manner,  and  presenting  phenomena  of  great  interest.  Cyanic 
acid  is  formed  as  a  potassium-salt,  in  conjunction  with  potassium  cyanide, 
when  cyanogen  gas  is  transmitted  over  heated  hydrate  or  carbonate  of  po- 
tassium, or  passed  into  a  solution  of  the  alkaline  base,  the  reaction  resem- 
bling that  by  which  potassium  chlorate  and  potassium  chloride  are  generated 
when  chlorine  is  passed  into  a  solution  of  potash,  (p.  186.)  Potassium 
cyanate  is,  moreover,  formed  when  the  cyanide  is  exposed  to  a  high  tem- 
perature with  access  of  air  :  unlike  the  chlorate,  it  bears  a  full  red  heat 
without  decomposition. 

CYANIC  ACID,  CNHO,  is  procured  by  heating  to  dull  redness  in  a  hard 
glass  retort  connected  with  a  receiver  cooled  by  ice,  cyanuric  acid  deprived 
of  its  water  of  crystallization.  The  cyanuric  acid  is  resolved,  without  any 
other  product,  into  cyanic  acid,  which  condenses  in  the  receiver  to  a  limpid, 
colorless  liquid,  of  exceedingly  pungent  and  penetrating  odor,  like  that  of 
the  strongest  acetic  acid:  it  even  blisters  the  skin.  When  mixed  with 
water,  it  decomposes  almost  immediately,  giving  rise  to  ammonium  bicar- 
bonate : 


CNHO 


OH         = 


C0 


NH 


This  is  the  reason  why  the  acid  cannot  be  separated  from  a  cyanate  by 
a  stronger  acid.  A  trace  of  cyanic  acid,  however,  always  escapes  decom- 
position, and  communicates  to  the  carbon  dioxide  evolved  a  pungent  smell 
similar  to  that  of  sulphurous  acid.  The  cyanates  may  be  easily  distin- 
guished by  this  smell,  and  by  the  simultaneous  formation  of  an  ammonia- 
salt,  which  remains  behind. 

Pure  cyanic  acid  cannot  be  preserved  :  shortly  after  its  preparation  it 
changes  spontaneously,  with  sudden  elevation  of  temperature,  into  a  solid, 
white,  opaque,  amorphous  substance,  called  cyamelide.  This  curious  body 

*  Naqud,  Laboratory,  p.  411. 


CYANATES.  713 

has  the  same  composition  as  cyanic  acid :  it  is  insoluble  in  water,  alcohol, 
ether,  and  dilute  acids:  it  dissolves  in  strong  oil  of  vitriol  by  the  aid  of 
heat,  with  evolution  of  carbon  dioxide  and  production  of  ammonia;  boiled 
with  solution  of  caustic  alkali,  it  dissolves,  ammonia  being  disengaged,  and 
a  mixture  of  cyanate  and  cyanurate  of  the  base  generated.  By  dry  distil- 
lation it  is  again  converted  into  cyanic  acid. 

Potassium  Cyanate,  CNKO. — The  best  method  of  preparing  this  salt  is, 
according  to  Liebig,  to  oxidize  potassium  cyanide  with  litharge.  The 
cyanide,  already  containing  a  portion  of  cyanate,  described  at  page  704, 
is  re-melted  in  an  earthen  crucible,  and  finely  powdered  lead  oxide  added 
by  small  portions :  the  oxide  is  instantaneously  reduced,  and  the  metal,  at 
first  in  a  state  of  minute  division,  ultimately  collects  to  a  fused  globule  at 
the  bottom  of  the  crucible.  The  salt  is  poured  out,  and,  when  cold,  pow- 
dered and  boiled  with  alcohol;  the  hot  filtered  solution  deposits  crystals 
of  potassium  cyanate  on  cooling.  The  great  deoxidizing  power  exerted  by 
potassium  cyanide  at  a  high  temperature  promises  to  render  it  a  valuable 
agent  in  many  of  the  finer  metallurgic  operations. 

Another  method  of  preparing  the  cyanate  is  to  mix  dried  and  finely-pow- 
dered potassium  ferrocyanide  with  half  its  weight  of  equally  dry  manganese 
dioxide ;  heat  this  mixture  in  a  shallow  iron  ladle,  with  free  exposure  to 
air  and  frequent  stirring,  until  the  tinder-like  combustion  is  at  an  end ; 
and  boil  the  residue  in  alcohol,  which  extracts  the  potassium  cyanate. 

This  salt  crystallizes  from  alcohol  in  thin,  colorless,  transparent  plates, 
which  suffer  no  change  in  dry  air,  but  on  exposure  to  moisture  are  gradu- 
ally converted,  without  much  alteration  of  appearance,  into  potassium  bi- 
carbonate, ammonia  being  at  the  same  time  given  off.  Water  dissolves  po- 
tassium cyanate  in  large  quantity :  the  solution  is  slowly  decomposed  in 
the  cold,  and  rapidly  at  a  boiling  heat,  into  potassium  bicarbonate  and  am- 
monia. When  a  concentrated  solution  is  mixed  with  a  small  quantity  of 
dilute  mineral  acid,  a  precipitate  falls,  consisting  of  acid  potassium  cyanu- 
rate. Potassium  cyanate  is  reduced  to  cyanide  by  ignition  with  charcoal 
in  a  covered  crucible.  Mixed  with  solutions  of  lead  and  silver,  it  gives 
rise  to  white  insoluble  cyanates  of  those  metals. 

Ammonium  cyanate  ;  Urea.  — When  the  vapor  of  cyanic  acid  is  mixed  with 
•  excess  of  ammoniacal  gas,  a  white,  crystalline,  solid  substance  is  produced, 
which  has  all  the  characters  of  a  true,  although  not  neutral  ammonium 
cyanate.  It  dissolves  in  water,  and  if  mixed  with  an  acid,  evolves  carbon 
dioxide :  with  an  alkali,  it  yields  ammonia.  If  the  solution  be  heated,  or 
if  the  crystals  be  merely  exposed  for  a  certain  time  to  the  air,  a  portion  of 
ammonia  is  dissipated,  and  the  properties  of  the  compound  are  completely 
changed.  It  may  now  be  mixed  with  acids  without  the  least  sign  of  de- 
composition, and  does  not  evolve  the  smallest  trace  of  ammonia  when 
treated  with  cold  caustic  alkali.  The  result  of  this  curious  metamorphosis 
of  the  cyanate  is  urea,  a  product  of  the  animal  body,  the  chief  and  charac- 
teristic constituent  of  urine.  This  transformation,  the  discovery  of  which 
is  due  to  Wohler,  is  especially  interesting  as  the  first  instance  of  the  arti- 
ficial formation  of  a  product  of  the  living  organism.  The  properties  of 
urea,  and  the  most  advantageous  methods  of  preparing  it,  will  be  found 
described  a  few  pages  hence. 

CYANURIC  Acin,  C3N3H303.  —  The  substance  called  melam,  of  which  fur- 
ther mention  will  be  made,  is  dissolved  by  gentle  heat  in  concentrated  sul- 
phuric acid,  the  solution  mixed  \\-itli  '20  or  30  parts  of  water,  and  the  whole 
maintained  at  a  temperature  approaching  the  boiling  point,  until  a  speci- 
men of  the  liquid,  on  being  tried  by  ammonia,  no  longer  gives  a  white  pre- 
cipitate :  several  days  are  required  to  effect  this  change.  The  liquid,  con- 


[ 


714  CYANOGEN   COMPOUNDS. 

centrated  by  evaporation,  deposits  on  cooling  cyanuric  acid,  which  is 
purified  by  re-crystallization.  Another,  and  perhaps  simpler  method,  is  to 
heat  dry  and  pure  urea  in  a  flask  or  retort :  the  substance  melts,  boils,  gives 
off  ammonia  in  large  quantity,  and  at  length  becomes  converted  into  a 
dirty-white,  solid,  amorphous  mass,  which  is  impure  cyanuric  acid.  This 
is  dissolved  by  the  aid  of  heat  in  strong  oil  of  vitriol,  and  nitric  acid 
added  by  small  portions  till  the  liquid  becomes  nearly  colorless  :  it  is  then 
mixed  with  water,  and  left  to  cool,  whereupon  the  cyanuric  acid  separates. 
The  urea  may  likewise  be  decomposed  very  conveniently  by  gently  heating 
it  in  a  tube,  while  dry  chlorine  or  hydrochloric  acid  gas  passes  over  it.  A 
mixture  of  cyanuric  acid  and  sal-ammoniac  results,  which  is  separated  by 
dissolving  the  latter  in  water. 

Cyanuric  acid  forms  colorless  efflorescent  crystals,  seldom  of  large  size, 
derived  from  an  oblique  rhombic  prism.  It  is  very  little  soluble  in  cold 
water,  and  requires  24  parts  for  solution  at  a  boiling  heat :  it  reddens  lit- 
mus feebly,  has  no  odor,  and  but  little  taste.  The  acid  is  tribasic:  the 
crystals  contain  C3N3HS03.  2  Aq.,  and  are  easily  deprived  of  their  water  of 
crystallization.  In  point  of  stability,  cyanuric  acid  offers  a  most  remark- 
able contrast  to  its  isomer,  cyanic  acid  ;  it  dissolves,  as  above  indicated,  in 
hot  oil  of  vitriol,  and  even  in  strong  nitric  acid,  without  decomposition, 
and,  in  fact,  crystallizes  from  the  latter  in  the  anhydrous  state.  Long- 
continued  boiling  with  these  powerful  agents  resolves  it  into  ammonia  and 
carbonic  acid. 

The  connection  between  cyanic  acid,  urea,  and  cyanuric  acid,  may  be 
thus  recapitulated : 

Ammonium  cyanate  is  converted  by  heat  into  urea. 

Urea  is  decomposed  by  the  same  means  into  cyanuric  acid  and  ammonia. 

Cyanuric  acid  is  changed  by  a  very  high  temperature  into  cyanic  acid, 
one  molecule  of  cyanuric  acid  splitting  into  3  molecules  of  cyanic 
acic. 

ETHYL  CYANATE  AND  CYANURATE. — When  a  dry  mixture  of  potassium 
cyanate  and  ethylsulphate  is  distilled,  a  product  is  obtained  which  consists 
of  a  mixture  of  the  above  ethers.  They  are  separated  without  difficulty, 
the  cyanate  boiling  at  60°  C.  (140°  F.),  while  the  boiling  point  of  the  cyan- 
urate  is  much  higher  —  namely,  276°  C.  (528°  F.).  Ethyl  cyanate,  CNO  . 
C2H5,  is  a  mobile  liquid,  the  vapor  of  which  excites  a  flow  of  tears.  Its 
formation  is  represented  by  the  equation, 

CNOK    +     S04(C2H5)K     =     S04K2     +      CNO .  C2H5. 

Ethyl  cyanurate  contains  C3N303 .  (C2H5)3 :  it  arises  in  this  reaction  from 
the  coalescence  of  3  molecules  of  ethyl  cyanate.  It  may  be  likewise  ob- 
tained by  distilling  a  mixture  of  potassium  ethylsulphate  and  cyanurate. 
Ethyl  cyanurate  is  a  crystalline  mass,  slightly  soluble  in  water,  readily 
soluble  in  alcohol  and  ether,  melting  at  85°  C.  (185°  F.).  By  substituting 
for  potassium  ethylsulphate,  salts  of  methyl-  and  amyl-sulphuric  acid,  the 
corresponding  methyl-  and  amyl-compounds  may  be  obtained. 

The  study  of  the  cyanic  and  cyanuric  ethers,  which  were  discovered  by 
Wurtz,  has  led  to  very  important  results,  which  will  be  fully  described  in 
the  section  on  the  Organic  Bases. 

FULMINIC  ACID. —  This  remarkable  compound,  which  is  polymeric  both 
with  cyanic  and  cyanuric  acids,  originates  in  the  peculiar  action  exercised 
by  nitrous  acid  upon  alcohol  in  presence  of  a  salt  of  silver  or  mercury. 
The  acid  itself,  or  hydrogen  fulminate,  has  not  been  obtained. 

Silver  fulminate  is  prepared  by  dissolving  40  or  50  grains  of  silver,  which 


FULMINTC   ACID.  715 

need  not  be  pure,  in  about  f  oz.  by  measure  of  nitric  acid  of  sp.  gr.  1-37, 
by  the  aid  of  a  little  heat.  To  the  highly  acid  solution,  while  still  hot,  2 
measured  ounces  of  alcohol  are  added,  and  heat  is  applied  until  reaction 
commences.  The  nitric  acid  oxidizes  part  of  the  alcohol  to  aldehyde  and 
oxalic  acid,  becoming  itself  reduced  to  nitrous  acid,  which,  in  turn,  acts 
upon  the  alcohol  in  such  a  manner  as  to  form  nitrous  ether,  fulminic  acid, 
and  water,  1  molecule  of  nitrous  ether  and  1  molecule  of  nitrous  acid 
containing  the  elements  of  1  molecule  of  fulminic  acid  and  2  molecules  of 
water : 

N02G2II5     +     N02H     =      C2N2H202      +      20H2. 
Ethyl  nitrite.        Nitrous  Fulminic 

acid.  acid. 

The  silver  fulminate  slowly  separates  from  the  hot  liquid  in  the  form  of 
small,  brilliant,  white,  crystalline  plates,  which  may  be  washed  with  a  little 
cold  water,  distributed  upon  separate  pieces  of  filter-paper  in  portions  not 
exceeding  a  grain  or  two  each,  and  left  to  dry  in  a  warm  place.  When 
dry,  the  papers  are  folded  up  and  preserved  in  a  box.  The  only  perfectly 
safe  method  of  keeping  the  salt  is  by  immersing  it  in  water.  Silver  fulmi- 
nate is  soluble  in  36  parts  of  boiling  water,  but  the  greater  part  crystallizes 
out  on  cooling:  it  is  one  of  the  most  dangerous  substances  known,  ex- 
ploding with  fearful  violence  when  strongly  heated,  or  when  rubbed  or 
struck  with  a  hard  body,  or  when  touched  with  concentrated  sulphuric 
acid:  the  metal  is  reduced,  and  a  large  volume  of  gaseous  matter  suddenly 
liberated.  Strange  to  say,  it  may,  when  very  cautiously  mixed  with  cop- 
per oxide,  be  burned  in  a  tube  with  as  much  facility  as  any  other  organic 
substance.  Its  composition  thus  determined  is  expressed  by  the  formula 
C2N202Ag2. 

Fulminic  acid  is  bibasic :  when  silver  fulminate  is  digested  with  caustic 
potash,  one-half  of  the  silver  is  precipitated  as  oxide,  and  a  silver  potassium 
fulminate,  C2N202AgK,  is  produced,  which  resembles  the  neutral  silver-salt, 
and  detonates  by  a  blow.  Corresponding  compounds  containing  sodium  or 
ammonium  exist ;  but  a  pure  fulminate  of  an  alkali-metal  has  never  been 
formed.  If  silver  fulminate  be  digested  with  water  and  copper,  or  zinc, 
the  silver  is  entirely  displaced,  and  a  fulminate  of  the  other  metal  produced. 
The  zinc-salt  mixed  with  baryta-water  gives  rise  to  a  precipitate  of  zinc 
oxide,  while  zinco-baric  fulminate,  (C2N202).;Zn//Ba//,  remains  in  solution. 
Mercuric  fulminate,  C2N202Hg//,  is  prepared  by  a  process  very  similar  to  that 
by  which  the  silver-salt  is  obtained  :  one  part  of  mercury  is  dissolved  in 
12  parts  of  nitric  acid,  and  the  solution  mixed  with  an  equal  quantity  of 
alcohol;  gentle  heat  is  applied,  and  if  the  reaction  becomes  too  violent,  it 
may  be  moderated  by  the  addition  from  time  to  time  of  more  spirit:  much 
carbonic  acid,  nitrogen,  and  red  vapors  are  disengaged,  together  with  a 
large  quantity  of  nitrous  ether  and  aldehyde  :  these  are  sometimes  con- 
densed and  collected  for  sale,  but  are  said  to  contain  hydrocyanic  acid. 
The  mercuric  fulminate  separates  from  hot  liquid,  and  after  cooling  may 
be  purified  from  an  admixture  of  reduced  metal  by  solution  in  boiling  wa- 
ter and  re-crystallization.  It  much  resembles  the  silver  salt  in  appear- 
ance, properties,  and  degree  of  solubility.  It  explodes  violently  by  friction 
or  percussion,  but,  unlike  the  silver  compound,  merely  burns  with  a  sud- 
den and  almost  noiseless  flash  when  kindled  in  the  open  air.  It  is  manu- 
factured on  a  large  scale  for  the  purpose  of  charging  percussion-caps  ;  sul- 
phur and  potassium  chlorate,  or  more  frequently  nitre,  are  added,  and  the 
powder,  pressed  into  the  cap,  is  secured  by  a  drop  of  varnish. 

The  relation  of  composition  between  the  three  isomeric  acids  are  beauti- 
fully seen  by  comparing  their  silver  salts:  the  first  acid  is  monobasic,  the 
second  bibasic,  and  the  third  tribasic : 


716  CYANOGEN   COMPOUNDS. 

Silver  cyanate CNOAg. 

Silver  fulminate C2N202Ag2. 

Silver  cyanurate          ....     C3N303Ag3. 

Until  lately,  beyond  that  of  identity  of  composition,  no  relation  was 
known  to  exist  between  fulminic  acid  and  its  isomers.  Dr.  Gladstone  has, 
however,  shown  that,  when  a  solution  of  copper  fulminate  is  mixed  with 
excess  of  ammonia,  filtered,  treated  with  sulphuretted  hydrogen  in  excess, 
and  again  filtered  from  the  insoluble  copper  sulphide,  the  liquid  obtained 
is  a  mixed  solution  of  urea  and  ammonium  sulphocyanate. 

Another  view  regarding  the  constitution  of  fulminic  acid  was  proposed 
by  Gerhardt.  The  fulminates  may  be  considered  as  methyl  cyanide  (aceto- 
nitrile),  in  which  one  atom  of  hydrogen  is  replaced  by  N02  and  2  atoms  of 
hydrogen  by  mercury  or  silver : 

CNCHHH Methyl  cyanide. 

CNC(N02)Ag2          .         .         .         Silver  fulminate. 

CNC(N02)Hg//        .         .         .         Mercuric  fulminate. 

This  view  has  received  some  support  by  the  interesting  observation, 
lately  made  by  Kekule',  that  the  action  of  chlorine  upon  mercuric  fulminate 
gives  rise  to  the  formation  of  chloropicrin,  CC13N02  (p.  588),  a  substance 
originally  obtained  by  Stenhouse,  which  may  be  viewed  as  chloroform,  tl'e 
hydrogen  of  which  is  replaced  by  N02.  The  connection  of  fulminic  acid 
with  the  methyl  series  is  thus  established. 

FULMINURIC  ACID,  C3N3H303.  —  This  acid,  isomeric  with  cyanuric  acid, 
was  discovered  simultaneously  by  Liebig  and  by  Schischkoff.  It  is  ob- 
tained by  the  action  of  a  soluble  chloride  upon  mercuric  fulminate.  On 
boiling  mercuric  fulminate  with  an  aqueous  solution  of  potassium  chloride, 
the  mercury-salt  gradually  dissolves,  and  the  clear  solution,  after  some 
time,  becomes  turbid,  in  consequence  of  a  separation  of  mercuric  oxide ; 
it  then  contains  potassium  fulminurate : 

3C2N202Hg"  -f  8KC1  +  OH2  ==  4KC1  -f  2HgCl2  +  Hg"0  +  2C3N303HK2 
Mercuric  Potassium 

fulminate.  fulminurate. 

If,  instead  of  potassium  chloride,  sodium  or  ammonium  chloride  be  em- 
ployed, the  corresponding  sodium  and  ammonium-compounds  are  obtained. 
The  fulminurates  crystallize  with  great  facility  ;  they  are  not  explosive. 

Fulminuric  acid  has  the  same  composition  as  cyanuric  acid,  but  it  is 
monobasic,  whereas  cyanuric  acid  is  tribasic. 

CYANOGEN  CHLORIDES. — Chlorine  forms  with  cyanogen,  or  its  elements, 
two  compounds,  which  are  polymeric,  and  correspond  to  cyanic  and  cyan- 
uric  acids.  Gaseous  cyanogen  chloride,  CyCl,  is  formed  by  passing  chlorine 
gas  into  anhydrous  hydrocyanic  acid,  or  by  passing  chlorine  over  moist 
mercuric  cyanide  contained  in  a  tube  sheltered  from  the  light.  It  is  a  per- 
manent and  colorless  gas  at  the  temperature  of  the  air,  of  insupportable 
pungency,  and  soluble  to  a  very  considerable  extent  in  water,  alcohol,  and 
ether.  At  — 18°  C.  (0°  F.)  it  congeals  to  a  mass  of  colorless  crystals,  which 
at  —15°  C.  (5°  F.)  melt  to  a  liquid  whose  boiling  point  is  —11  6°  C.  (18° 
F.).  At  the  temperature  of  the  air  it  is  condensed  to  the  liquid  form  under 
a  pressure  of  four  atmospheres,  and  when  long  preserved  in  this  condition 
in  hermetically  sealed  tubes  gradually  passes  into  the  solid  modification. 

On  passing  gaseous  cyanogen  chloride  into  a  solution  of  ammonia  in 
anhydrous  ether,  ammonium  chloride  is  deposited,  and  the  ether  contains 
cyanamide,  CN2H2,  in  solution,  from  which  it  separates  on  evaporation  in 
the  crystalline  form.  Cyanamide  is  easily  soluble  in  water,  alcohol,  and 
ether  ;  it  melts  at  40°  C.  (104°  F.}. 


SULPHOCYANATES.  717 

Solid  cyanogen  chloride,  C3N3C13,  or  Cy3Cl3,  is  generated  when  anhydrous 
hydrocyanic  acid  is  put  into  a  vessel  of  chlorine  gas,  and  the  whole  exposed 
to  the  sun :  hydrochloric  acid  is  formed  at  the  same  time.  It  forms  long 
colorless  needles,  which  exhale  a  powerful  and  offensive  odor,  compared  by 
some  to  that  of  the  excrement  of  mice  ;  it  melts  at  140°  C.  (284°  F.),  and 
sublimes  unchanged  at  a  higher  temperature.  When  heated  in  contact 
with  water,  it  is  decomposed  into  cyanuric  and  hydrochloric  acids.  It  dis- 
solves in  alcohol  and  ether  without  decomposition. 

CYANOGEN  BROMIDE  AND  IODIDE  correspond  to  the  first  of  the  preceding 
compounds,  and  are  prepared  by  distilling  bromine  or  iodine  with  mercuric 
cyanide.  They  are  colorless,  volatile,  solid  substances,  of  powerful  odor. 

CYANOGEN  SULPHIDE,  C2N2S,  or  Cy2S,  recently  obtained  by  Linnemann 
by  the  action  of  cyanogen  iodide  upon  silver  sulphocyanate,  crystallizes 
in  transparent,  volatile,  rhombic  plates,  having  an  odor  similar  to  that  of 
cyanogen  iodide.  It  melts  at  60°,  but  decomposes  rapidly  at  a  higher  tem- 
perature ;  dissolves  in  ether,  alcohol,  and  water,  and  separates  from  hot 
concentrated  solutions,  on  cooling,  in  the  crystalline  form. 

Sulphocyanic  Acid,  CNHS.  —  This  acid  is  the  sulphur  analogue  of  cyanic 
acid,  and,  like  the  latter,  is  monobasic,  the  sulphocyanates  of  monad  metals 
being  represented  by  the  formula  CNSM. 

Potassium  sulphocyanate,  CNSK.  —  To  prepare  this  salt,  yellow  potassium 
ferrocyanide,  deprived  of  its  water  of  crystallization,  is  intimately  mixed 
with  half  its  weight  of  sulphur,  and  the  whole  heated  to  tranquil  fusion  in 
an  iron  pot,  and  kept  for  some  time  in  that  condition.  When  cold,  the 
melted  mass  is  boiled  with  water,  which  dissolves  out  a  mixture  of  potas- 
sium sulphocyanate  and  iron  sulphocyanate,  leaving  little  behind  but  the 
excess  of  sulphur.  This  solution,  which  becomes  red  on  exposure  to  the 
air,  from  oxidation  of  the  iron,  is  mixed  with  potassium  carbonate,  by 
which  the  iron  is  precipitated,  and  potassium  substituted:  an  excess  of 
the  carbonate  must  be,  as  far  as  possible,  avoided.  The  filtered  liquid  is 
concentrated,  by  evaporation  over  an  open  fire,  to  a  small  bulk,  and  left  to 
cool  and  crystallize.  The  crystals  are  drained,  purified  by  re-solution,  if 
necessary,  or  dried  by  enclosing  them,  spread  on  filter-paper,  over  a  sur- 
face of  oil  of  vitriol  covered  with  a  bell-jar. 

•    The  reaction  between  the  sulphur  and  the  potassium  ferrocyanide  is 
represented  by  the  equation: 

K4Fe"C6N6        +        S6        =        4CNSK        +         (CNS)2Fe" 

Another,  and  even  better  process,  consists  in  gradually  heating  to  low 
redness  in  a  covered  vessel  a  mixture  of  46  parts  of  dried  potassium  fer- 
rocyanide, 32  of  sulphur,  and  17  of  pure  potassium  carbonate.  The  mass 
is  exhausted  with  water,  the  aqueous  solution  is  evaporated  to  dryness, 
and  the  residue  is  exhausted  with  alcohol.  The  alcoholic  liquid  deposits 
splendid  crystals  on  cooling  or  evaporation. 

Potassium  sulphocyanate  crystallizes  in  long,  slender,  colorless  prisms, 
or  plates,  which  are  anhydrous:  it  has  a  bitter  saline  taste,  and  is  desti- 
tute of  poisonous  properties:  it  is  very  soluble  in  water  and  alcohol,  and 
deliquesces  when  exposed  to  a  moist  atmosphere.  When  heated,  it  melts 
to  a  colorless  liquid,  at  a  temperature  far  below  that  of  ignition. 

When  chlorine  is  passed  into  a  strong  solution  of  potassium  sulphocya- 
nate, a  large  quantity  of  a  bulky,  deep  yellow,  insoluble  substance,  re- 
sembling some  varieties  of  lead  chromate,  is  produced,  together  with  potas- 
sium chloride;  the  liquid  sometimes  assumes  a  deep-red  tint,  and  emits  a 
pungent  vapor,  probably  cyanogen  chloride.  The  yellow  matter  may  be 
collected  on  a  filter,  well  washed  with  boiling  water,  and  dried:  it  retains 


L 


718  CYANOGEN    COMPOUNDS. 

its  brilliancy  of  tint.  It  was  formerly  called  sulphocyanogen,  from  its  sup- 
posed identity  with  the  radical  of  the  sulphocyanates ;  it  is,  however,  inva- 
riably found  to  contain  hydrogen,  and  is  represented  by  the  formula 
C3N3HS3.  The  yellow  substance,  now  generally  called  per  sulphocyanogen,  is 
quite  insoluble  in  water,  alcohol,  and  ether:  it  dissolves  in  concentrated 
sulphuric  acid,  from  which  it  is  precipitated  by  dilution.  Caustic  potash 
also  dissolves  it,  with  decomposition ;  acids  throw  down  from  this  solution 
a  pale-yellow,  insoluble  body,  having  acid  properties.  When  heated  in 
the  dry  state,  it  evolves  sulphur  and  carbon  bisulphide,  and  leaves  a  pale, 
straw-yellow  substance,  called  hy drome  Hone,  C6N9rl3,  the  decomposition 
being  represented  by  the  equation : 

3C3N3HS3        =        3CS2         +        S3        +        C6N9H3. 

Hydrogen  Sulphocyanate,  or  Hydrosulphocj/anic  Acid,  CNSH,  is  obtained  by 
decomposing  lead  sulphocyanate,  suspended  in  water,  with  sulphuretted 
hydrogen.  The  filtered  solution  is  colorless,  very  acid,  and  not  poisonous  ; 
it  is  easily  decomposed,  in  a  very  complex  manner,  by  ebullition,  and  by 
exposure  to  the  air.  By  neutralizing  the  liquid  with  ammonia,  and  evapo- 
rating very  gently  to  dryness,  ammonium  sulphocyanate,  CNSNH4,  is  obtained 
as  a  deliquescent,  saline  mass.  The  salt  may  be  conveniently  prepared  by 
digesting  hydrocyanic  acid  with  yellow  ammonium  sulphide  (containing 
excess  of  sulphur),  and  boiling  off  the  excess  of  the  latter:  2CNH  -j- 
(NH4)2S  +  S2  =  H2S  -j-  2CNS(NH4).  The  sulphocyanates  of  sodium,  barium, 
strontium,  calcium,  manganese,  and  iron,  are  colorless  and  very  soluble:  those 
of  lead  and  silver  are  white  and  insoluble.  A  soluble  sulphocyanate  mixed 
with  a  ferric  salt  gives  no  precipitate,  but  causes  the  liquid  to  assume  a 
deep  blood-red  tint:  hence  the  use  of  potassium  sulphocyanate  as  a  test 
for  iron  in  the  state  of  ferric  salt.  The  red  color  produced  by  sulphocya- 
nates in  ferric  solutions  is  exactly  like  that  caused  under  similar  circum- 
stances by  meconic  acid.  The  two  substances  may,  however,  be  readily 
distinguished  by  the  addition  of  a  solution  of  gold  chloride,  which  de- 
stroys the  color  produced  by  sulphocyanates.  The  ferric  meconate  may 
also  be  distinguished  from  the  sulphocyanide,  as  Everitt  has  shown,  by  an 
addition  of  corrosive  sublimate,  which  bleaches  the  sulphocyanate,  but 
has  little  effect  upon  the  meconate.  This  is  a  point  of  considerable  prac- 
tical importance,  as  in  medico-legal  inquiries,  in  which  evidence  of  the 
presence  of  opium  is  sought  for  in  complex  organic  mixtures,  the  detec- 
tion of  meconic  acid  is  usually  the  object  of  the  chemist:  and  since  traces 
of  alkaline  sulphocyanide  are  to  be  found  in  the  saliva,  it  becomes  very 
desirable  to  remove  that  source  of  error  and  ambiguity. 

The  great  facility  with  which  hydrocyanic  acid  may  be  converted  into 
ammonium  sulphocyanate  enables  us  to  ascertain  its  presence  by  the  iron 
test  just  described.  The  cyanide  to  be  examined  is  mixed  in  a  watch-glass 
with  some  hydrochloric  acid,  and  covered  with  another  watch-glass,  to 
which  a  few  drops  of  yellow  ammonium  sulphide  adhere.  On  heating  the 
mixture,  hydrocyanic  acid  is  disengaged,  which  combines  with  the  am- 
monium sulphide,  and  produces  ammonium  sulphocyanate  :  this,  after  ex- 
pulsion of  the  excess  of  sulphide,  yields  the  red  color  with  solution  of  ferric 
chloride. 

SULPHOCYANIC  ETHERS.  —  These  ethers  exhibit  isomeric  modifications, 
probably  analogous  to  those  of  the  alcoholic  cyanides  and  isocyanides  (p. 
711).  The  normal  sulphocyanates  of  methyl  and  its  homologues  were  dis- 
covered by  Cahours;*  and  quite  recently  Hofmann  has  obtained  the  corre- 
sponding isosulphocyanates.f  The  same  chemist  some  years  ago  obtained 

*  Ann.  Chim.  Phys.  [3],  viii.  2f>4. 

f  Proceedings  of  the  Royal  Society,  xvi.  254. 


SULPHOCYANIC   ETHERS.  719 

phcnyl  isosulphocyanate.*    Allyl  isosulphocyanate  has  long  been  known  as 
a  natural  product. 

Normal  Ethyl  Sulphocyanate,  C  {  QP  „  ,  is  obtained  by  saturating  a  con- 


centrated  solution  of  potassium  sulphocyanate  with  ethyl  chloride : 

PTTPl  T?T1          -I-          P/N 

£  uaH5w  U\SC2H6; 

also  by  distilling  a  mixture  of  calcium  ethylsulphate  and  potassium  sulpho- 
cyanate. It  is  a  mobile,  colorless,  strongly  refracting  liquid,  having  a  some- 
what pungent  odor,  like  that  of  mercaptan.  It  boils  at  146°  C.  (295° F.)  With 
ammonia  it  does  not  combine  directly,  but  yields  products  of  decomposition. 
The  methyl  and  amyl  sulphocyanic  ethers  resemble  the  ethyl  compound, 
and  are  obtained  by  similar  processes.  The  methyl  ether  boils  at  about 
132°  C.  (270°  F.);  the  amyl  ether  at  197°  C.  (387°  F.). 


f  (CS)" 
\C2H5 
phocarbamide  with  phosphoric  oxide,  which  abstracts  ethylamine: 


Ethyl  Isosulphocyanate,  N  •[  L     '    ,  is  produced  by  distilling  diethyl-sul- 

(.  ^2™5 


Diethyl-sulpho-  Ethylamine.  Ethyl  isosul- 

carbamide.  phocyanate. 

This  ether  differs  essentially  in  all  its  properties  from  ethyl  sulphocyan- 
ate. It  boils  at  134°  C.  (273°  F.),  and  has  a  powerfully  irritating  odor, 
like  that  of  mustard-oil,  and  quite  different  from  that  of  normal  ethyl-sul- 
phocyanate.  It  unites  directly  with  ammonia  in  alcoholic  solution,  forming 
ethylsulphocarbamide,  N2(CS)//(C2H5)H3,  and  forms  similar  compounds  with 
methylamine  and  ethylamine.  The  pungent  odor  and  the  direct  combina- 
tion with  ammonia  and  amines,  are  characteristic  of  all  the  ethers  of  this 
group. 

Phenyl  Isosulphocyanate,  N(CS)"(C6H5),  is  obtained  by  distilling  phenyl- 
sulphocarbamide,  N2(CS)"(C6H6)H8,  with  phosphoric  oxide:  naphthyl  iso- 
sulphocyanate, N(CS)//(C10H7),  in  like  manner  from  dinaphthylsulpho- 
cavbamide.  The  former  boils  at  220°  C.  (428°  F.). 

Allyl  Isosulphocyanate,  N  j  £  '^    .  —  This  is  the  intensely  pungent  yolatile 

oil  obtained  by  distilling  the  seeds  of  black  mustard  with  water.  It  does 
not  exist  ready  formed  in  the  seeds,  but  is  produced  by  the  decomposition 
of  myronic  acid  under  the  influence  of  myrosin,  an  albuminous  substance 
analogous  to  the  synaptase  of  bitter  almonds  (see  p.  579).  The  same 
compound,  or  perhaps  its  isomer,  normal  ethylsulphocyanate,  is  produced 
by  the  action  of  potassium  sulphocyanate  or  silver  sulphocyanate.  on  allyl 
iodide  or  allyl  oxide.  Oil  of  mustard  is  a  transparent,  colorless,  strongly 
refracting  oil,  possessing  in  the  highest  degree  the  sharp  penetrating  odor 
of  black  mustard.  The  smallest  quantity  of  the  vapor  excites  tears,  and  is 
apt  to  produce  inflammation  of  the  eyes.  It  has  a  burning  taste,  and  rapidly 
blisters  the  skin.  Its  specific  gravity  is  1-009  at  15°.  It  boils  at  148°  C. 
(298°  F. ).  It  is  sparingly  soluble  in  water,  easily  soluble  in  alcohol  and 
ether;  dissolves  sulphur  and  phosphorus  when  heated,  and  deposits  them 
in  the  crystalline  state,  on  cooling.  It  is  violently  oxidized  by  nitric  and 
by  nitromuriatic  acids.  Heated  in  a  sealed  tube  with  potassium  monosul- 
phide,  it  yields  potassium  sulphocyanate  and  allyl  sulphide  (volatile  oil  of 
garlic,  p.  545)  : 

2NCS(C3H6)         -f-        K2S        =        2CNSK        +         (CSH6)£, 
*  Proceedings  of  the  Royal  Society,  jx.  27,4,  487, 


720  CYANOGEN    COMPOUNDS. 

It  likewise  yields  garlic  oil  when  decomposed  by  potassium.  Heated  to 
]20°  in  a  sealed  tube  with  pulverized  soda-lime,  it  yields  sodium  sulpho- 
cyanate  and  allyl  oxide,  the  oxidized  constituent  of  garlic  oil : 

2NCS(C3H5)         +       Na20        =        2CNSNa       +         (C3H5)20. 

Aqueous  potash,  soda,  baryta,  and  the  oxides  of  lead,  silver,  and  mercury, 
in  presence  of  water,  convert  oil  of  mustard  into  sinapoline,  C7H12N20,  with 
formation  of  metallic  sulphide  and  carbonate ;  thus  : 

2NCS(C3H6)    +    3PbO    -f-    OH2    =    2PbS    -f    C03Pb    -f    C7H,2N20. 

Sinapoline  is  a  basic  substance,  which  crystallizes  in   colorless  plates, 
soluble  in  water  and  alcohol,  and  having  a  distinct  alkaline  reaction. 

Oil  of  mustard  unites  readily  with   ammonia,  forming  thiosinamine,  C4H5 

f(CS) 
NS  .  NH3,  or  allyl-sulphocarbamide,  N2  -j  C3H5,  which  is  also  a  basic  com- 


pound, forming  colorless  prismatic  crystals,  having  a  bitter  taste  and  solu- 
ble in  water.  The  solution  does  not  affect  test-paper.  Thiosinamine  melts 
when  heated,  but  cannot  be  sublimed.  Acids  combine  with  it,  but  do  not 
form  crystallizable  salts:  the  double  salts  of  the  hydrochloride  with  pla- 
tinic  and  mercuric  chloride  are  the  most  definite. 

Thiosinamine  is  decomposed  by  metallic  oxides,  as  lead  oxide  or  mercuric 
oxide,  with  production  of  a  metallic  sulphide  and  sinamine,  C4H6N2,  a  basic 
compound  which  crystallizes  very  slowly  from  a  concentrated  aqueous  so- 
lution in  brilliant,  colorless  crystals  containing  water.  It  has  a  powerfully 
bitter  taste,  is  strongly  alkaline  to  test-paper,  and  decomposes  ammonium 
salts  at  the  boiling  heat.  Its  oxalate  is  crystallizable.  The  formation  of 
sinamine  from  thiosinamine  by  the  action  of  mercuric  oxide  is  represented 
by  the  equation  C4H8N2S  +  HgO  =  HgS  -f  OH2  -f  C4H6N2. 

Seleniocyanates.  —  A  series  of  salts  containing  selenium,  and  correspond- 
ing in  composition  and  properties  with  the  sulphocyanates,  have  been  dis- 
covered and  examined  by  Mr.  Crookes.* 

Melam. — This  name  is  given  by  Liebig  to  a  buff-colored,  insoluble, 
amorphous  substance,  obtained  by  the  distillation  of  ammonium  sulphocy- 
anate  at  a  high  temperature.  It  may  be  prepared  in  large  quantity  by  in- 
timately mixing  1  part  of  perfectly  dry  potassium  sulphocyanate  with  2 
parts  of  powdered  sal-ammoniac,  and  heating  the  mixture  for  some  time  in 
a  retort  or  flask:  carbon  bisulphide,  ammonium  sulphide,  and  sulphuretted 
hydrogen,  are  disengaged  and  volatilized,  while  a  mixture  of  melam,  potas- 
sium chloride,  and  sal-ammoniac  remains:  the  two  latter  substances  are 
removed  by  washing  with  hot  water.  Melam  contains  C6H9Nn :  it  dissolves 
in  concentrated  sulphuric  acid,  and  gives,  by  dilution  with  water  and  long 
boiling,  cyanuric  acid.  The  same  substance  is  produced,  with  disengage- 
ment of  ammonia,  when  melam  is  fused  with  potassium  hydrate.  When 
strongly  heated,  melam  is  resolved  into  mellone  and  ammonia. 

If  melam  be  boiled  for  a  long  time  in  a  moderately  strong  solution  of 
caustic  potash,  until  the  whole  has  dissolved,  and  the  liquid  be  then  con- 
centrated, a  crystalline  substance  separates  on  cooling,  which  is  called 
mclamine.  By  re-crystallization  it  is  obtained  in  colorless  crystals,  having 
the  figure  of  an  octohedron  with  rhombic  base :  it  is  but  slightly  soluble  in 
cold  water,  fusible  by  heat.  Melamine  is  also  formed  on  heating  cyana- 
mide  to  150°  C.  (302°  F.),  and  even  on  evaporating  an  aqueous  solution  of 
that  substance.  It  contains  C3H6N6,  and  acts  as  a  base,  combining  with 
acids  to  form  crystallizable  compounds.  A  second  basic  substance,  called 
*  Journal  of  the  Chemical  Society,  iv.  12, 


UREA.  721 

ammeline,  very  similar  in  properties  to  melamine,  is  found  in  the  alkaline 
mother-liquor  from  which  the  melamine  has  separated  :  it  is  thrown  down  on 
neutralizing  the  liquid  with  acetic  acid.  The  precipitate,  dissolved  in  di- 
lute nitric  acid,  yields  crystals  of  ammeline  nitrate,  from  which  the  pure 
ammeline  may  be  separated  by  ammonia.  It  forms  a  brilliant  white  pow- 
der composed  of  minute  needles,  insoluble  in  water  and  alcohol,  and  con- 
tains C3H5N50.  When  ammeline  is  dissolved  in  concentrated  sulphuric 
acid,  and  the  solution  mixed  with  a  large  quantity  of  water,  or,  better, 
spirit  of  wine,  a  white,  insoluble  powder  falls,  which  is  called  ammelide,  and 
is  found  to  contain  C6H9N903. 

By  the  action  of  acids  or  alkalies,  melamine  maybe  converted  into  amme- 
line, ammelide,  and,  lastly,  into  cyanuric  acid,  water  being  assimilated 
and  ammonia  evolved : 

C3H6N6        +         H20        =        C3H5N?0        +        NHS 
Melamine.  Ammeline. 

2C3H5N50    -f         H20        =        C6H9N903       -f        NH3 
Amjneline.  Ammelide. 

C6H9N903     +       8H20        =       2C3H3N303       -f      3NH3. 
Ammelide.  Cyanuric  acid. 

Mellone  and  its  Compounds.  —  The  formation  of  mellone  as  a  residuary 
product  of  the  action  of  heat  on  persulphocyanogen,  and  upon  melam,  has 
been  already  mentioned.  This  substance,  which  does  not  appear  to  have 
been  obtained  in  a  state  of  purity,  possesses  the  properties  of  an  organic 
radical.  At  a  high  temperature  it  combines  directly  with  potassium,  pro- 
ducing a  well-defined  saline  compound,  tripotassic  mellonide,  C9H,3K3,  and 
the  same  salt  is  produced  in  the  action  of  mellone  upon  potassium  bromide 
and  iodide,  bromine  and  iodine  being  liberated.  A  better  method  of  pre- 
paring it  consists  in  fusing  crude  mellone  with  potassium  sulphocyanate. 
It  may  also  be  produced  by  fusing  the  ferrocyanide  with  half  its  weight  of 
sulphur.  The  fused  mass  obtained  by  either  process  is  dissolved  in  boiling 
water,  from  which  the  tri-potassic  mellonide  crystallizes  on  cooling,  and 
may  be  purified  by  repeated  crystallization.  Acetic  acid  converts  this  salt 
into  dipotassic  mellonide,  C9H13K2H,  which  is  also  soluble.  Hydrochloric 
acid  produces  the  monopotassic  salt,  C9N13KH2,  which  is  insoluble.  These 
three  salts  stand  to  each  other  in  the  same  relation  as  the  several  salts  of 
phosphoric  and  cyanuric  acids.  Tripotassic  mellonide  produces  with  solu- 
ble silver-salts  a  white  precipitate,  C9Nl3Ag3 ;  with  lead-salts  and  mercury- 
salts,  precipitates  containing  respectively  C^N^Pbg,  and  CjgN^Hgj.  The 
latter  dissolved  in  hydrocyanic  acid,  and  treated  with  sulphuretted  hydro- 
gen, yields  hydromellonic  acid,  C9N13H3.  It  is  known  only  in  solution, 
which  has  an  acid  taste :  on  evaporation  it  is  decomposed. 


UREA.  — URIC  ACID  AND  ITS  PRODUCTS. 

These  bodies  are  closely  connected  with  the  cyanogen-compounds,  and 
may  be  most  conveniently  discussed  in  the  present  place. 

Urea,  CN2H40. — Urea  maybe  extracted  from  its  natural  source,  the 
urine,  or  it  may  be  prepared  by  artificial  means.  Fresh  urine  is  concen- 
trated in  a  water-bath,  until  reduced  to  an  eighth  or  a  tenth  of  its  original 
volume,  and  filtered  through  cloth  from  the  insoluble  deposits  of  urates 
and  phosphates.  The  liquid  is  mixed  with  about  an  equal  quantity  of  a 
strong  solution  of  oxalic  acid  in  hot  water,  and  the  whole  vigorously  agi- 
61 


722  UKEA. 

tated  and  left  to  cool.  A  very  copious  fawn-colored  crystalline  precipitate 
of  urea  oxalate  is  obtained,  which  may  be  placed  upon  a  doth  filter,  slightly 
washed  with  cold  water,  and  pressed.  This  is  to  be  dissolved  in  boiling 
water,  and  powdered  chalk  added  until  effervescence  ceases,  and  the  liquid 
becomes  neutral.  The  solution  of  urea  is  filtered  from  the  insoluble  cal- 
cium oxalate,  warmed  with  a  little  animal  charcoal,  again  filtered,  and  con- 
centrated by  evaporation,  avoiding  ebullition,  until  crystals  form  on  cool- 
ing: these  are  purified  by  a  repetition  of  the  last  part  of  the  process. 
Urea  may  be  extracted  in  great  abundance  from  the  urine  of  horses  and 
cattle  duly  concentrated,  and  from  which  the  hippuric  acid  has  been  sepa- 
rated by  addition  of  hydrochloric  acid ;  oxalic  acid  then  throws  down  the 
oxalate  in  such  quantity  as  to  render  the  whole  semi-solid.  Another  pro- 
cess consists  in  precipitating  the  evaporated  urine  with  concentrated  nitric 
acid,  when  urea  nitrate  is  precipitated,  which  is  purified  by  re-crystalliza- 
tion with  animal  charcoal,  and,  lastly,  decomposed  by  barium  carbonate, 
whereby  a  mixture  of  barium  nitrate  and  urea  is  formed,  which  is  to  be 
evaporated  to  dryness  on  the  water-bath,  and  exhausted  with  hot  alcohol ; 
the  urea  then  crystallizes  on  cooling. 

Urea  is  produced  artificially  by  heating  a  solution  of  ammonium  cya- 
nate. The  following  method  of  proceeding  yields  it  in  any  quantity  that 
can  be  desired.  Potassium  cyanate,  prepared  by  Liebig's  process  (p.  713), 
is  dissolved  in  a  small  quantity  of  water,  and  a  quantity  of  dry  neutral 
ammonium  sulphate,  equal  in  weight  to  the  cyanate,  is  added.  The  whole 
is  evaporated  to  dryness  in  a  water-bath,  and  the  dry  residue  boiled  with 
strong  alcohol,  which  dissolves  out  the  urea,  leaving  the  potassium  sul- 
phate and  the  excess  of  ammonium  sulphate  untouched.  The  filtered  solu- 
tion, concentrated  by  distilling  off  a  portion  of  the  spirit,  deposits  the 
urea  in  beautiful  crystals  of  considerable  size. 

Urea  forms  transparent,  colorless,  four-sided  prisms,  which  are  anhy- 
drous, soluble  in  an  equal  weight  of  cold  water,  and  in  a  much  smaller 
?uantity  at  a  high  temperature.  It  is  also  readily  dissolved  by  alcohol, 
t  is  inodorous,  has  a  cooling  saline  taste,  and  is  permanent  in  the  air, 
unless  the  latter  be  very  damp.  When  heated  it  melts,  and  at  a  higher 
temperature  decomposes,  with  evolution  of  ammonia  and  ammonium  cya- 
nate ;  cyanuric  acid  remains,  which  bears  a  much  greater  heat  without 
change.  The  solution  of  urea  is  neutral  to  test-paper :  it  is  not  decom- 
posed in  the  cold  by  alkalies  or  by  calcium  hydrate,  but  at  a  boiling  heat 
emits  ammonia,  and  forms  a  metallic  carbonate.  The  same  change  hap- 
pens by  fusion  with  the  alkaline  hydrates,  and  when  urea  is  heated  with 
water,  in  a  sealed  tube,  to  a  temperature  above  100°: 

COH4N2        +        H20        =        C02        -f        2NH3. 

Urea  contains,  in  fact,  the  elements  of  ammonium  carbonate  minus  the  ele- 
ments of  water:  C03(NH4)2 —  2H20,  and  has  accordingly  been  supposed 
to  be  identical  with  carbamide.  Recent  experiments  have  shown,  however, 
that  it  is  isomeric,  not  identical  with  that  compound,  inasmuch  as,  when 
heated  with  a  large  excess  of  potassium  permanganate  in  presence  of  much 
free  alkali,  it  gives  off  all  its  nitrogen  in  the  free  state  as  gas,  whereas 
when  amides  and  ammonium-salts  are  thus  treated,  the  whole  of  the  nitro- 
gen is  oxidized  to  nitric  acid.*  The  difference  of  constitution  between  the 
three  isomeric  compounds  —  ammonium  cyanate,  urea,  and  carbamide  — 
may  perhaps  be  represented  by  the  following  formulae : 

(NH)"  (NH2 

NH2  C 1  NH2 

.OH  {&' 

Ammonium  cyanate.  Urea.  Carbamide. 

*  Wanllyn  and  Gpmgee,  Chera.  Soc.  Journal  [2],  yi.  25. 


URIC    ACID.  723 

A  solution  of  pure  urea  shows  no  tendency  to  change  by  keeping,  and  is 
not  decomposed  by  boiling ;  in  the  urine,  on  the  other  hand,  where  it  is 
associated  with  putrefiable  organic  matter,  as  mucus,  the  case  is  different. 
In  putrid  urine  no  urea  can  be  found,  but  enough  ammonium  carbonate  to 
cause  brisk  effervescence  with  an  acid;  and  if  urine,  in  a  recent  state, 
be  long  boiled,  it  gives  off  ammonia  and  carbonic  acid  from  the  same 
source. 

Urea  is  instantly  decomposed  by  nitroiis  acid  into  carbon  dioxide,  nitro- 
gen, and  water :  COH4N2  -f  2N02H  =  C02  -f  2N2  -f  3H20 ;  this  decompo- 
sition explains  the  use  of  urea  in  preparing  nitric  ether  (p.  526).  When 
chlorine  gas  is  passed  over  melted  urea,  hydrochloric  acid  and  nitrogen  are 
evolved,  and  there  remains  a  mixture  of  sal-ammoniac  and  cyanuric  acid : 

6COH4N2  -f   3C12   =  2C3H3N303   +   4NH4C1   -f   2HC1   +   N2; 

but  by  chlorine  in  presence  of  water,  or  by  hypochlorous  acid,  it  is  resolved 
into  hydrochloric  acid,  carbon  dioxide,  water,  and  nitrogen : 

COH4N2    -f     3C1HO     =    3HC1     -f     C02    -f     2H20     +     N2. 

Urea  acts  as  a  base :  with  nitric  acid  it  forms  a  sparingly  soluble  com- 
pound, which  crystallizes,  when  pure,  in  small,  indistinct,  colorless  plates, 
containing  COH4N2 .  N03H.  When  colorless  nitric  acid  is  added  to  urine 
concentrated  to  a  fourth  or  a  sixth  of  its  volume,  and  cold,  the  nitrate 
crystallizes  out  in  large,  brilliant,  yellow  laminae,  which  are  very  insoluble 
in  the  acid  liquid.  The  production  of  this  nitrate  is  highly  characteristic 
of  urea*  The  ozalate,  (COH4N2)2 .  C2H204,  when  pure,  crystallizes  in  large, 
transparent,  colorless  plates,  which  have  an  acid  reaction,  and  are  spar- 
ingly soluble.  Urea  forms  several  compounds  with  metallic  salts,  e.  g., 
with  those  of  mercury.  On  mixing  a  liquid  containing  urea  with  a  solution 
of  mercuric  nitrate,  a  white  precipitate  is  formed,  consisting  of  COH4N2 .  2HgO. 
If  the  nitric  acid  which  is  thus  set  free  be  neutralized  by  the  addition  of  an 
alkali  or  baryta-water,  the  whole  of  the  urea  is  removed  from  the  liquid 
in  the  form  of  the  above  compound.  Liebig  has  based  upon  this  reaction 
a  process  of  determining  the  amount  of  urea  in  urine :  2  volumes  of  urine 
are  mixed  with  1  volume  of  a  baryta-solution  prepared  with  2  volumes 
,  baryta-water  saturated  in  the  cold,  and  1  volume  of  a  solution  of  barium- 
nitrate  also  saturated  in  the  cold  ;  the  liquid  is  filtered  from  the  precipi- 
tated sulphate  and  phosphate  of  barium;  and  a  graduated  solution  of  mer- 
curic nitrate  is  added  to  a  measured  quantity  of  this  filtered  liquid  (about 
15  c.c.)  till  a  sample  taken  out  gives  a  yellow  precipitate  with  sodium  car- 
bonate. It  is  convenient  to  dilute  the  mercuric  solution  to  such  a  degree 
that  1  cubic  centimetre  of  it  shall  correspond  to  0-01  grm.  of  urea.* 

A  series  of  substances  analogous  to  urea,  which  are  known  under  the 
names  of  methyl-urea,  ethyl-urea,  biethyl-urea,  &c.,  will  be  noticed  in  the 
section  on  Organic  Bases. 

Uric  Acid,  C5N4H403;  formerly  called  Lithic  acid.  —  This  acid  is  a  product 
of  the  animal  organism,  and  has  never  been  formed  by  artificial  means.  It 
may  be  prepared  from  human  urine  by  concentration  and  addition  of  hy- 
drochloric acid,  and  crystallizes  out  after  some  time  in  the  form  of  small, 
reddish,  translucent  grains,  very  difficult  to  purify.  A  much  preferable 
method  is,  to  employ  the  solid  white  excrement  of  serpents,  which  can 
be  easily  procured:  this  consists  almost,  entirely  of  uric  acid  and  ammo- 
nium urate.  It  is  reduced  to  powder,  and  boiled  in  dilute  solution  of  caus- 
tic potash:  the  liquid,  filtered  from  the  insignificant  residue  of  feculent 

*  Respecting  certain  precautions  to  he  observed  in  performing  this  process,  see  the  article 
"  Urine,"  by  Dr.  Michael  Foster,  in  Watts's  Dictionary  of  Chemistry. 


724:  URIC   ACID. 

matter  and  earthy  phosphates,  is  mixed  with  excess  of  hydrochloric  acid, 
boiled  for  a  few  minutes,  and  left  to  cool.  The  product  is  collected  on  a 
filter,  washed  until  free  from  potassium  chloride,  and  dried  by  gentle 
heat. 

Uric  acid,  thus  obtained,  forms  a  glistening,  snow-white  powder,  taste- 
less, inodorous,  and  very  sparingly  soluble.  It  is  seen  under  the  micro- 
scope to  consist  of  minute,  but  regular  crystals.  It  dissolves  in  concen- 
trated sulphuric  acid  without  apparent  decomposition,  and  is  precipitated 
by  dilution  with  water.  By  destructive  distillation,  uric  acid  yields  cyanic 
acid,  hydrocyanic  acid,  carbon  dioxide,  ammonium  carbonate,  and  a  black 
coaly  residue,  rich  in  nitrogen.  By  fusion  with  potassium  hydrate,  it  yields 
potassium  carbonate,  cyanate,  and  cyanide.  When  treated  with  nitric  acid 
and  with  lead  dioxide,  it  undergoes  decomposition  in  a  manner  to  be  pres- 
ently described. 

Uric  acid  is  bibasic :  its  most  important  salts  are  those  of  the  alkali- 
metals.  Acid  potassium  urate,  C5N4H3K03,  is  deposited  from  a  hot  saturated 
solution  of  uric  acid  in  the  dilute  alkali,  as  a  white,  sparingly  soluble,  con- 
crete mass,  composed  of  minute  needles:  it  requires  about  500  parts  of 
cold  water  for  solution,  is  rather  more  soluble  at  a  high  temperature,  and 
much  more  soluble  in  excess  of  alkali.  Sodium  urate  resembles  the  potas- 
sium-salt :  it  forms  the  chief  constituent  of  the  gouty  concretions  in  the 
joints  called  chalk-stones.  Ammonium  urate  is  also  a  sparingly  soluble  com- 
pound, requiring  for  solution  about  1000  parts  of  cold  water :  the  solubility 
is  very  much  increased  by  the  presence  of  a  small  quantity  of  certain 
salts,  as  sodium  chloride.  The  most  common  of  the  urinary  deposits, 
forming  a  buff-colored  or  pinkish  cloud  or  muddiness,  which  disappears 
by  re-solution  when  the  urine  is  warmed,  consists  of  a  mixture  of  different 
urates. 

Uric  acid  is  perfectly  well  characterized,  even  when  in  very  small  quan- 
tity, by  its  behavior  with  nitric  acid.  A  small  portion  mixed  with  a  drop 
or  two  of  nitric  acid  in  a  small  porcelain  capsule  dissolves  with  copious 
effervescence.  When  this  solution  is  cautiously  evaporated  nearly  to  dry- 
ness,  and,  after  the  addition  of  a  little  water,  mixed  with  a  slight  excess 
of  ammonia,  a  deep-red  tint  of  murexide  is  immediately  produced. 

Impure  uric  acid,  in  a  remarkable  state  of  decomposition,  is  now  im- 
ported into  this  country,  in  large  quantities,  for  use  as  a  manure,  under 
the  name  of  guano  or  huano.  It  comes  chiefly  from  the  barren  and  unin- 
habited islets  of  the  western  coast  of  South  America,  and  is  the  production 
of  the  countless  birds  that  dwell  undisturbed  in  those  regions.  The  people 
of  Peru  have  used  it  for  ages.  Guano  usually  appears  as  a  pale-brown 
powder,  sometimes  with  whitish  specks :  it  has  an  extremely  offensive  odor, 
the  strength  of  which,  however,  varies  very  much.  It  is  soluble  in  great 
part  in  water,  and  the  solution  is  found  to  be  extremely  rich  in  oxalate  of 
ammonia,  the  acid  having  been  generated  by  a  process  of  oxidation.  Guano 
also  contains  a  peculiar  substance  called  guanine,  which  will  be  described 
further  on. 

Products  formed  from  Uric  Acid  by  Oxidation,  $c. 

Uric  acid  is  remarkable  for  the  facility  with  which  it  is  altered  by  oxi- 
dizing agents,  and  the  great  number  of  definite  and  crystallizable  compounds 
obtained  in  this  manner,  or  by  treating  the  immediate  products  of  oxida- 
tion with  acids,  alkalies,  reducing  agents,  &c.  The  following  is  a  list  of 
most  of  the  compounds  thus  produced  :  — 


DERIVATIVES    OF    URIC    ACID. 


725 


Uric  acid 

C5N4H203  .  II  * 

Thionuric  acid 

C4NJI,06S  .  H 

Pseudo-uric  acid  . 

C.NJWH 

Hydurilic  acid 

C4N4II406.H2 

Uroxanic  acid 

C5N4II8Oe.Ha 

Allantoin 

C4N4II603 

Alloxan 

C4N2II204 

Glycoluvil 

C4N4II602 

Alloxanic  acid 

C4N2H205.H2. 

Mycomelic  acid 

C4N4H302.H 

Alloxantin    . 

C8N4H407  .  3  Aq. 

Oxaluric  acid 

C3N2H304  .  H 

Barbituric  acid    . 

C4N2H203  .  H2 

Allanturic  acid 

C3N2H303  .  H 

Bromobarbi-  \ 
turic  acid     J 

C4N2H2Br03  .  H 

Hydantoin 
Hydantoic  acid 

C3N2M402 
C3N2H503.H 

Dibromobar-  \ 

Allituric  acid 

C6N4H504  .  H 

bituric  acid  / 

C4N2H2Br203 

Leucoturic  acid 

C6N4H305.H 

Violuric  acid 

C4N3II204  .  H 

Parabanic  acid 

cX«A 

Dilituric  acid 

C4N3H205  .  H 

Dibarbituric  acid  . 

C8N4H405.H2 

Violantin 

C4N6H609 

Murcxide 

C8N6H806 

Dialuric  acid 

C4N2H304.H 

Mesoxalic  acid 

C305.H2 

Urarnil 

C4N3H503 

When  uric  acid  is  subjected  to  the  action  of  an  oxidizing  agent  in  pres- 
ence of  water,  it  gives  up  two  of  its  hydrogen-atoms  to  the  oxidizing  agent, 
while  the  dehydrogenized  residue  (which  may  be  called  dehyduric  acid)  re- 
acts with  water  to  form  mesoxalic  acid  and  urea: 


C5N4H203 

Dehyduric 

acid. 


Mesoxalic 
acid. 


2CN2H40 
Urea. 


The  separation  of  the  urea  generally  takes  place,  however,  by  two  stages, 
the  first  portion  being  removed  more  easily  than  the  second ;  thus,  when 
dilute  nitric  acid  acts  upon  uric  acid,  alloxan  is  produced;  and  this,  when 
heated  with  baryta-water,  is  further  resolved  into  mesoxalic  acid  and  urea: 


Dehyduric 
acid. 

C4N2H204 
Alloxan. 


2H20       = 


C4N2H204 
Alloxan. 


2H20       =        C3H205 

Mesoxalic  acid. 


CN2H40 
Urea. 


CN2H40 
Urea. 


.  Moreover,  the  urea  is  frequently  resolved  into  carbonic  acid  and  am- 
monia by  the  action  of  the  acids  or  alkalies  present.  Alloxan  is  a  monu- 
reide  of  mesoxalic  acid — that  is  to  say,  it  is  a  compound  of  that  acid  with  one 
molecule  of  urea  minus  2H2O;  and  the  hypothetical  dehyduric  acid  is  the 
diureide  of  the  same  acid,  derived  from  it  by  addition  of  1  molecule  of  urea 
and  subtraction  of  4  molecules  of  water.  Now,  by  hydrogenizing  mesoxalic 
acid,  we  obtain  tartronic  acid,  C3H405  (p.  668) ;  and  by  hydrogenizing  al- 
loxan, we  obtain  dialuric  acid,  which  two  bodies,  accordingly,  bear  to  uric 
acid  the  same  relation  that  mesoxalic  acid  and  urea  bear  to  dehyduric  acid ; 
thus: 


C.HA 

Mesoxalic 
acid. 


C4N2H204 
Alloxan. 


C4N2H404 

Dialuric 

acid. 


Dehyduric 
acid. 

<WI403; 
Uric  acid. 


Tartronic 
acid. 

and  just  as  the  hypothetical  dehyduric  acid  yields  mesoxalic  acid  and  al- 
loxan, so  should  actual  uric  acid  yield  tartronic  and  dialuric  acids.  These 
bodies,  however,  have  not  been  obtained  by  the  direct  breaking  up  of  uric 

*  The  basicity  of  the  several  acids  in  this  table  is  indicated  by  the  number  of  hydrogen-atoms 
to  the  right  of  the  point. 
01  * 


726  URIC   ACID. 

acid,  but  only  by  rehydrogenizing  the  mesoxalic  acid  and  alloxan  which 
result  from  the  breaking  up  of  its  dehydrogenized  product.  Provisionally, 
however,  dialuric  and  uric  acids  may  be  regarded  as  tartron-ureide  and 
tartron-diureide  respectively. 

The  several  bodies  just  mentioned  are  typical  of  three  well-defined  classes 
of  compounds,  to  one  or  other  of  which  an  immense  number  of  uric  acid 
products  may  be  referred.  First,  there  is  the  class  of  simple  non-nitro- 
genous acids,  or  an-ureides,  like  tartronic  and  mesoxalic  acid  ;  secondly, 
there  is  a  class  of  bodies  containing  a  residue  of  the  acid  plus  one  residue 
of  urea  —  these  are  the  mon-ureides,  such  as  dialuric  acid  and  alloxan;  and, 
lastly,  the  class  of  bodies  containing  a  residue  of  the  acid  plus  two  residues 
of  urea,  or  the  di-ureides,  such  as  uric  acid  itself. 

Mesoxalic  acid,  the  most  complex  non-nitrogenous  product  obtainable 
directly  from  uric  acid,  constitutes  the  third  term  in  the  following  series  : 

CH20?  C2H204  C3H2N5, 

Carbonic.  Oxalic.  Mesoxalic. 

each  of  which  contains  1  atom  of  carbon  monoxide,  CO,  more  than  the  pre- 
ceding. Now,  when  mesoxalic  acid  is  acted  upon  by  nascent  oxygen,  its 
excess  of  carbon  monoxide  is  removed  in  the  form  of  carbon  dioxide,  and 
it  is  thus  converted  into  oxalic  acid  : 

C3H206        +        0        =        C02        -f        C2H20,. 

Hence,  when  uric  acid  is  subjected  to  a  more  active  oxidation  than  that 
which  suffices  to  produce  mesoxalic  acid,  we  obtain  oxalic  acid,  which  may 
occur  either  in  its  simple  anureide  state,  or  conjugated  with  1  molecule  of 
urea  to  form  a  monureide,  such  as  parabanic  acid;  or  with  2  molecules  of 
urea  to  form  a  diureide,  such  as  mycomelic  acid,  a  body  related  to  oxalic 
acid  just  as  uric  acid  is  related  to  mesoxalic  acid. 

In  like  manner,  when  uric  acid  is  subjected  to  a  still  more  powerful  oxi- 
dation than  suffices  to  produce  oxalic  acid,  we  obtain  carbonic  acid,  which, 
like  oxalic  and  mesoxalic  acids,  is  also  capable  of  giving  rise  to  ureides. 
No  ureide  of  carbonic  acid  has,  indeed,  yet  been  formed  directly  from  uric 
acid,  the  active  treatment  required  to  eft'ect  the  complete  oxidation  of  the 
uric  acid  producing  also  a  separation  from  one  another  of  the  resulting 
carbonic  acid  and  urea,  which,  however,  may  be  obtained  in  combination 
by  other  means.  Allophanic  acid,  for  instance,  the  ethylic  ether  of  which 
is  obtained  by  passing  the  vapor  of  cyanic  acid  into  absolute  alcohol,  is  a 
monureide  of  carbonic  acid  ;  but  no  diureide  of  this  acid  appears  to  have 
been  yet  produced. 

Alloxan,  the  monureide  of  mesoxalic  acid  above  mentioned,  is  formed 
from  mesoxalate  of  urea  by  elimination  of  two  molecules  of  water  ;  but 
there  is  another  monureide,  namely,  alloxanic  acid,  which  differs  from  the 
original  salt  by  only  one  molecule  of  water.  Similarly,  oxalic  acid  forms 
two  monureides  —  namely,  parabanic  acid  or  paraban,  analogous  to  alloxan; 
and  oxaluric  acid,  analogous  to  alloxanic  acid.  Carbonic  acid,  however, 
forms  but  a  single  ureide,  which  is  produced  by  the  elimination  of  only 
one  molecule  of  water,  and  accordingly  belongs  to  the  same  series  as  the 
oxaluric  and  alloxanic  acids  ;  thus  : 

Acids.  Ureides. 

CH203,  Carbonic.  C2N2H403,  Allophanic. 

C2H204,  Oxalic.  jn3M254n4'  £xal"ric' 

\  C3N2H203,  Paraban. 


C3H205,  Mesoxalic.  n 

4N2H2O4,  Alloxan. 


DERIVATIVES    OF    URIC   ACID. 


727 


Similarly,  among  the  diureides,  some  are  formed  from  the  corresponding 
monureides  by  elimination  of  one  molecule,  and  others  by  elimination  of 
two  molecules  of  water. 

Mesoxalic  acid,  as  already  observed,  is  convertible,  by  deoxidation  or 
hydrogenation,  into  tartronic  acid,  and  by  pushing  the  deoxidation  a  stage 
farther,  malonic  acid  (p.  661)  is  obtained,  both  of  which  acids  are  capable 
of  forming  monureides  and  diureides;  and,  in  a  similar  manner,  oxalic 
and  carbonic  acids  furnish  a  variety  of  similar  deoxidation-products. 

Of  the  numerous  compounds  belonging  to  the  uric  acid  group  thus  pro- 
duced, the  most  important  are  included  in  the  following  table,*  which  is 
divided  perpendicularly  into  three  columns  of  an-ureides,  mon-ureides,  and 
di-ureides,  and  horizontally  into  three  layers  of  carbonic,  oxalic,  and  mes- 
oxalic  products.  The  compounds  connected  by  dotted  lines  differ  in  com- 
position from  one  another  by  an  excess  or  deficit  of  one  molecule  of  urea 
minus  one  molecule  of  water,  while  those  standing  on  the  same  level  in 
the  adjoining  columns,  and  unconnected  by  dotted  lines,  differ  from  one 
another  by  an  excess  or  deficit  of  one  molecule  of  urea  minus  two  mole- 
cules of  water. 


An-ureides. 
CH203,  Carbonic. 


Mon-ureides. 
_...C2N2H403,  Allophanic. 


Di-ureides. 


C3N2H602,  Aceturea. 
'C3N2H603,  Glycoluric. 


C2H402,  Acetic.'^  ,• 
C2H403,  Glycollic. 
C2H404,  Glyoxylic. 


,/C4N4H602,  Glycoluril. 
C4N4H603,  Allantoin. 

<C3N2H402,  Hydantoin./ 

,C3N2H403,  Lantanuric.      C4N4H402,  Mycomelic. 

xC3N2H404,  Oxaluric. 


/    C3JN2H4O4,  Oxaluric. 
C2H203,  Glyoxalic.>-x 
C2H204,  Oxalic..-"'        C3N2H203,  Parabanic. 


C5N4H40,  Hy  poxanthine. 
C5N4H402,  Xanthine. 
C6N4H403,  Uric  acid. 
-C5N4HBOll,  Pseudo-uric. 


C4N2H40S,  Barbituric. 
C4N2H404,  Dialuric.^ 
xC4N2H405,Alloxanic. 
C3H206,  Mesoxalic./    C4N2H204,  Alloxan. 
Between  some  of  the  consecutive  monureides  shown  in  this  table,  there 
exist  bodies  formed  by  the  union  of  the  two  consecutive  monureides,  with 
elimination  of  water.     Such  is   the   mode  of  formation  of  allituric,  lantan- 
uric,  and  hydurilic  acids,  and  of  alloxantin  ;  thus : 

C6N4H604      =      C3N2H402      -f       C3N2H403      —      H20 
Allituric  Hydantoin.  Lantanuric 

acid.  acid. 


C6N4H405 

Leucoturic 

acid. 

C8N4H?06 

Hydurilic 

acid. 

C8N4H407 
Alloxantin. 


=       C. 


AHA 

Lantanuric 
acid. 

C4N2H403 
Barbituric 

acid. 

C4N2H404 

Dialuric 

acid. 


C3N2H203 
Parabanic 

acid. 

C4N2H404 

Dialuric 

acid. 

C4N2H204 

Alloxan. 


H20 
H20 


*  This  table,  together  with  the  preceding  view  of  the  relations  between  the  several  deriva- 
tives of  uric  acid,  is  taken  from  (Ming's  "  Lectures  on  Animal  Chemistry."  London,  1866, 
pp.  129-135. 


728  DERIVATIVES    OF    URIC   ACID. 

The  following  is  a  description  of  some  of  the  more  important  compounds 
above  enumerated : 

ALLANTOIN,  C4N4H6Og. —  This  substance,  which  contains  the  elements  of 
2  molecules  of  ammonium  oxalate  minus  5  molecules  of  water  [2C2(NH4)2 
04  —  5H20],  is  contained  in  the  allantoi'c  liquid  of  the  foetal  calf  and  in 
the  urine  of  the  sucking  calf.  It  is  produced  artificially,  together  with 
oxalic  acid  and  urea,  by  boiling  uric  acid  with  lead  dioxide  and  water : 

2CsN4H/)3  +  302  +  5H20  =  C4N4H603   +    2C2H204  +  2CN2H403 
Uric  acid.  Allantoin.      Oxalic  acid.        Urea. 

The  liquid  filtered  from  lead  oxalate,  and  duly  concentrated  by  evapora- 
tion, deposits  on  cooling  crystals  of  allantoin,  which  are  purified  by  re- 
solution and  the  use  of  animal  charcoal.  The  mother-liquor,  when  further 
concentrated,  yields  crystals  of  pure  urea.  Allantoin  forms  small  but 
most  brilliant  prismatic  crystals,  which  are  transparent  and  colorless,  des- 
titute of  taste,  and  without  action  on  vegetable  colors.  It  dissolves  in  160 
parts  of  cold  water,  and  in  a  smaller  quantity  at  the  boiling  heat.  It  is 
decomposed  by  boiling  with  nitric  acid,  and  by  oil  of  vitriol  when  concen- 
trated and  hot,  being  in  this  case  resolved  into  ammonia,  carbon  dioxide, 
and  carbon  monoxide.  Heated  with  concentrated  solutions  of  caustic  alka- 
lies, it  is  decomposed  into  ammonia  and  oxalic  acid. 

ALLOXAN,  C4N2H204.  —  This  is  the  characteristic  product  of  the  action 
of  concentrated  nitric  acid  on  uric  acid  in  the  cold.  An  acid  is  prepared 
of  sp.  gr.  about  1-45,  and  placed  in  a  shallow  open  basin:  into  this  a  third 
of  its  weight  of  dry  uric  acid  is  thrown,  by  small  portions,  with  constant 
agitation,  care  being  taken  that  the  temperature  never  rises  to  any  con- 
siderable extent.  The  uric  acid  at  first  dissolves,  with  copious  efferves- 
cence of  carbon  dioxide  and  nitrogen,  and  eventually  the  whole  becomes  a 
mass  of  white,  crystalline,  pasty  matter.  This  is  left  to  stand  some  hours, 
drained  from  the  acid  liquid  in  a  funnel  having  its  neck  stopped  with  pow- 
der and  fragments  of  glass,  and  afterward  more  effectually  dried  upon  a 
porous  tile.  This  is  alloxan  in  a  crude  state:  it  is  purified  by  solution  in  a 
small  quantity  of  water,  and  crystallization. 

Alloxan  crystallizes  with  facility  from  a  hot  and  concentrated  solution, 
slowly  suffered  to  cool,  in  solid,  hard,  anhydrous  crystals  of  great  regular- 
ity, which  are  transparent,  nearly  colorless,  have  a  high  degree  of  lustre, 
and  the  figure  of  a  modified  rhombic  octohedron.  These  crystals  are 
monohydrated,  consisting  of  C4N2H204.  Aq.  A  cold  solution,  on  the  other 
hand,  left  to  evaporate  spontaneously,  deposits  large  foliated  crystals  con- 
taining 4  molecules  of  water:  they  effloresce  rapidly  in  the  air.  The 
monohydrate  heated  to  150°-160°  C.  (302°-320°  F.)  in  a  stream  of  dry  hy- 
drogen gives  off  its  water,  and  leaves  anhydrous  alloxan,  C4N2H204.  Al- 
loxan is  very  soluble  in  water:  the  solution  has  an  acid  reaction,  a  dis- 
agreeably astringent  taste,  and  stains  the  skin,  after  a  time,  red  or  purple. 
It  is  decomposed  by  alkalies,  and  both  by  oxidizing  and  deoxidizing 
agents:  its  most  characteristic  property  is  that  of  forming  a  deep-blue 
compound  with  a  ferrous  salt  and  an  alkali. 

ALLOXANIC  ACID,  C4N2H405.— The  barium-salt  of  this  acid  is  deposited 
in  small  colorless,  pearly  crystals,  when  baryta-water  is  added  to  a  solu- 
tion of  alloxan,  heated  to  60°  C.  (140°  F.),  as  long  as  the  precipitate  first 
produced  redissolves,  and  the  filtered  solution  is  then  left  to  cool.  The 
barium  may  be  separated  by  the  cautious  addition  of  dilute  sulphuric  acid, 
and  the  filtered  liquid  by  gentle  evaporation  yields  alloxanic  acid  in  small 
radiated  needles.  It  has  an  acid  taste  and  reaction,  decomposes  carbon- 
ates., and  dissolves  zinc  with  disengagement  of  hydrogen.  It  is  a  bibasic 


THIONURIC    ACID.  729 

acid.  The  alloxanates  of  the  alkali-metals  are  freely  soluble:  those  of  the 
earth-metals  dissolve  in  a  large  quantity  of  tepid  water;  that  of  silver  is 
quite  insoluble  and  anhydrous. 

MESOXALIC  ACID,  C3H205.  — When  a  warm  saturated  solution  of  barium 
alloxanate  is  heated  to  ebullition,  a  precipitate  falls,  which  is  a  mixture 
of  barium  carbonate,  alloxanate,  and  mesoxalate :  the  solution  is  found 
to  contain  unaltered  barium  alloxanate  and  urea.  Mesoxalic  acid  is  best 
prepared  by  slowly  adding  solution  of  alloxan  to  a  boiling-hot  solution  of 
lead  acetate :  the  heavy  granular  precipitate  of  lead  mesoxalate  thus  pro- 
duced is  washed  and  decomposed  by  sulphuretted  hydrogen :  urea  is  also 
formed  in  this  reaction  (p.  725).  Mesoxalic  acid  is  crystallizable  :  it  has 
a  sour  taste  and  powerfully  acid  reaction,  and  resists  a  boiling  heat:  it 
forms  sparingly  soluble  salts  with  barium  and  calcium,  and  a  yellowish  in- 
soluble compound  with  silver,  which  is  reduced  with  effervescence  when 
gently  heated. 

MYCOMELIC  ACID,  C4N4H402. — This  acid  is  formed  when  ammonia  in 
excess  is  added  to  a  solution  of  alloxan,  the  whole  heated  to  ebullition, 
and  afterward  supersaturated  with  dilute  sulphuric  acid  :  it  then  separates 
as  a  yellow,  light  precipitate,  which  increases  in  quantity  as  the  liquid 
cools.  It  is  but  feebly  soluble  in  water,  easily  dissolved  by  alkalies,  and 
forms  a  yellow  silver-salt.  Its  formation  from  alloxan  and  ammonia  is 
represented  by  the  equation  : 

C4N2H204        +        2NH3        =         C4N4H402        -f        2H20. 

PARABANIC  ACID,  or  PARABAN,  C3N2H203.  —  This  is  the  characteristic 
product  of  the  action  of  moderately  strong  nitric  acid  on  uric  acid  or  al- 
loxan, by  the  aid  of  heat : 

Cy^HA    +     02    +     2H20    =    C3N2H203    -f     2C02    +     2NH3. 

It  is  conveniently  prepared  by  heating  together  1  part  of  uric  acid  and  8 
parts  of  nitric  acid  until  the  reaction  has  nearly  ceased ;  the  liquid  is  eva- 
porated to  a.  syrupy  state  and  left  to  cool;  and  the  acid  drained  from  the 
mother-liquor  is  purified  by  re-crystallization.  Parabanic  acid  forms 
colorless,  transparent,  thin,  prismatic  crystals,  which  are  permanent  in  the 
a'ir:  it  is  easily  soluble  in  water,  has  a  pure  and  powerfully  acid  taste,  and 
reddens  litmus  strongly.  Neutralized  with  ammonia,  and  mixed  with  sil- 
ver nitrate,  it  gives  a  white  precipitate. 

OXALURIC  ACID,  C3H2N404.  —  The  ammonium-salt  of  this  acid  separates 
in  colorless  needles,  when  a  solution  of  parabanic  acid  saturated  with  am- 
monia is  boiled  for  a  moment,  and  then  left  to  cool.  The  acid  is  obtained 
by  adding  an  excess  of  dilute  sulphuric  acid  to  a  hot  and  strong  solution 
of  the  ammonium-salt,  and  cooling  the  whole  rapidly.  It  forms  a  white, 
crystalline  powder,  of  acid  taste  and  reaction,  capable  of  combining  with 
bases:  the  barium-  and  calcium-salts  are  sparingly  soluble;  the  silver-salt 
crystallizes  from  the  mixed  hot  solution  of  silver  nitrate  and  ammonium 
oxalurate  in  long,  silky  needles.  Oxaluric  acid  contains  the  elements  of  1 
molecule  of  parabanic  acid  and  1  molecule  of  water.  Its  solution  is  resolved 
by  ebullition  into  free  oxalic  acid  and  oxalate  of  urea. 

THIONURIC  ACID,  C4N3H6SOtf.  —  This  acid,  which  contains  the  elements 
of  alloxan,  ammonia,  and  sulphurous  oxide  (C4N2H204  -(-  NH3  -f-  S02),  is 
formed,  as  an  ammonium-salt,  when  a  cold  solution  of  alloxan  is  mixed 
with  a  saturated  aqueous  solution  of  sulphurous  acid,  in  such  quantity  that 
the  odor  of  the  gas  remains  quite  distinct ;  an  excess  of  ammonium  car- 
bonate mixed  with  a  little  caustic  ammonia  is  then  added,  and  the  whole 


730  DERIVATIVES    OF   URIC   ACID. 

boiled  for  a  few  minutes.  On  cooling,  ammonium  thionurate  is  deposited  in 
great  abundance,  forming  beautiful,  colorless,  crystalline  plates,  which  by 
solution  in  water  and  re-crystallization  acquire  a  fine  pink  tint.  A  solu- 
tion of  this  salt  gives  with  lead-acetate  a  precipitate  of  insoluble  lead  thio- 
nurate, which  is  at  first  white  and  gelatinous,  but  shortly  becomes  dense 
and  crystalline  :  from  this  compound  the  acid  may  be  obtained  by  the  aid 
of  sulphuretted  hydrogen.  It  forms  a  white  crystalline  mass,  permanent 
in  the  air,  very  soluble  in  water,  of  acid  taste  and  reaction,  and  capable 
of  combining  directly  with  bases.  When  its  solution  is  heated  to  the  boil- 
ing point,  it  undergoes  decomposition,  yielding  sulphuric  acid  and  uramile, 
or  dialuramide,  C4N3H503  : 


URAMILE.  —  To  prepare  this  substance,  ammonium  thionurate  is  dissolved 
in  hot  water,  mixed  with  a  small  excess  of  hydrochloric  acid,  and  the  whole 
boiled  in  a  flask:  the  uramile  then  separates  as  a  white,  crystalline  sub- 
stance, increasing  in  quantity  till  the  contents  of  the  vessel  often  become 
semi-solid.  After  cooling,  it  is  collected  on  a  filter,  washed  with  cold  water 
to  remove  the  sulphuric  acid,  and  dried  by  gentle  heat,  during  which  it 
frequently  becomes  pinkish.  It  is  tasteless  and  nearly  insoluble  in  water, 
but  dissolves  in  ammonia  and  the  fixed  alkalies.  The  ammoniacal  solution 
becomes  purple  in  the  air.  It  is  decomposed  by  strong  nitric  acid,  with 
formation  of  alloxan  and  ammonium  nitrate  : 

C4N3H503    +     0    =    C4N2H204     +     NH3. 

Uramile,  heated  with  aqueous  solution  of  potassium  cyanate,  is  converted 
into  pseudo-uric  acid,  C5N4H604  =  C4N8H503  +  CNIIO. 

Uramile,  added  to  argentic  or  mercuric  oxide  suspended  in  boiling  water, 
is  converted  into  murexide  (p.  732). 

ALLOXANTIN,  C8N4H407  .  3  Aq.  —  This  substance  is  the  chief  product  of 
the  action  of  hot  dilute  nitric  acid  upon  uric  acid,  and  is  likewise  produced 
by  the  action  of  deoxidizing  agents  upon  alloxan,  anhydrous  aljoxantin,  in 
fact,  containing  1  atom  of  oxygen  less  than  2  molecules  of  alloxan.  It  is 
best  prepared  by  passing  sulphuretted  hydrogen  gas  through  a  moderately 
strong  and  cold  solution  of  alloxan.  The  mother-liquor  from  which  the 
crystals  of  alloxan  have  separated  answers  the  purpose  perfectly  well  :  it 
is  diluted  with  a  little  water,  and  a  copious  stream  of  gas  transmitted 
through  it.  Sulphur  is  then  deposited  in  large  quantity,  mixed  with  a 
white,  crystalline  substance,  which  is  the  alloxantin.  The  product  is 
drained  upon  a  filter,  slightly  washed,  and  then  boiled  in  water  :  the  fil- 
tered solution  deposits  the  alloxantin  on  cooling.  Alloxantin  forms  small, 
four-sided,  oblique  rhombic  prisms,  colorless  and  transparent;  it  is  soluble 
with  difficulty  in  cold  water,  but  more  freely  at  a  boiling  temperature. 
The  solution  reddens  litmus,  gives  with  baryta-water  a  violet-colored  pre- 
cipitate, which  disappears  on  heating,  and  when  mixed  with  silver  nitrate 
produces  a  black  precipitate  of  metallic  silver.  Heated  with  chlorine  or 
nitric  acid,  it  is  changed  by  oxidation  to  alloxan.  The  crystals  become  red 
when  exposed  to  ammoniacal  vapors.  They  contain  3  molecules  of  water, 
which  they  do  not  give  off  till  heated  above  150°  C.  (302°  F.). 

Alloxantin  is  readily  decomposed  :  when  a  stream  of  sulphuretted  hydro- 
gen is  passed  through  its  boiling  solution,  sulphur  is  deposited  and  dialuric 
acid  is  produced.  A  hot  saturated  solution  of  alloxantin  mixed  with  a  neu- 
tral salt  of  ammonia  instantly  assumes  a  purple  color,  which,  however, 
quickly  vanishes,  the  liquid  becoming  turbid  from  the  formation  of  ura- 
mile :  the  solution  is  then  found  to  contain  alloxan  and  free  acid.  With 
silver  oxide,  alloxantin  gives  off  carbon  dioxide,  reduces  a  portion  of  the 


BARBITURIC   ACID.  731 

metal,  and  converts  the  remainder  of  the  oxide  into  oxalurate.  Boiled 
with  water  and  lead  dioxide,  alloxantin  gives  urea  and  lead  carbonate. 

DIALTJRIC  ACID,  C4N.;H404. — This  acid  is  the  final  product  of  the  action 
of  reducing  agents  on  alloxan,  and  is  formed  when  sulphuretted  hydrogen 
is  passed  through  a  boiling  solution  of  alloxan  till  no  further  action  takes 
place :  C4N2H204  -+-  H2S  =  C4N2H404  -|-  S.  It  forms  colorless  needles,  re- 
sembling those  of  alloxantin,  has  a  strong  acid  reaction,  and  neutralizes 
acids  completely,  forming  salts  which  are  sparingly  soluble  in  water. 

HYDURILIC  ACID,  C8N4H606.  —  Dialuric  acid,  heated  to  about  160°  C. 
(320°  F.),  with  glycerin  (which  acts  merely  as  a  solvent),  splits  up  into 
formic  acid,  carbon  dioxide,  and  the  ammonium-salt  of  hydurilic  acid: 

5C4N2H404    =     CH202    -f     3C02     +     2C8N4H5(NH4)06. 

By  converting  this  ammonium-salt  into  a  copper-salt,  and  decomposing  the 
latter  with  hydrochloric  acid,  hydurilic  acid  is  obtained  in  crystals. 

Hydurilic  acid  is  converted  by  fuming  nitric  acid  into  alloxan,  without 
any  other  product ;  but  with  nitric  acid  of  ordinary  strength  it  yields  al- 
loxan, together  with  violuric  acid,  violantin,  and  dilituric  acid:* 

C8N4H606  +  N03H  =  C4N3H304    +    C4N2H204  +  H20 
Hydurilic  Violuric  Alloxan. 

acid.  acid. 

C8N4Hg06    +    2N03H  =  C4N3H305    -f  C4N2H204  +  N02H  +  H20. 
Hydurilic  Dilituric  Alloxan. 

acid.  acid. 

If  the  action  be  carried  on  to  the  end,  dilituric  acid  is  the  only  product. 
This  acid  may  indeed  be  regarded  as  a  product  of  the  oxidation  of  violuric 
acid 
two. 

DiBROMOBARBiTURic  ACID,  or  BROMALLOXAN,  C4N2H2Br203,  is  produced, 
together  with  alloxan,  by  the  action  of  bromine  on  hydurilic  acid: 

C4N4H606  +  Br6  +  H20  =  C4N2H2Br203  +  C4N2H204  +  4HBr. 

It  crystallizes  in  colorless,  shining  plates,  or  prisms,  belonging  to  the  tri- 
metric  system,  soluble  in  water,  very  soluble  in  alcohol  and  ether.  By  hy- 
drogen sulphide,  in  presence  of  water,  it  is  reduced  to  dialuric  acid : 

C4N2H2Br203    +    H2S   -f    H20   =   C4N2H404     +     2HBr   +    S. 
With  a  small  quantity  of  hydriodic  acid  it  yields  hydurilic  acid : 

2C4N2H2Br203     +     6HI     =     C8N4H606     -f     4HBr     -f     3I2; 

but  when  it  is  heated  with  excess  of  hydriodic  acid,  the  reduction  goes  a 
step  'farther,  and  barbituric  acid,  C4N2H403,  is  produced : 

C4N2H2Br203     -f     4HI     =     C4N2H403     -f     2HBr     -f     2I2. 

Barbituric  acid  crystallizes  in  beautiful  prisms,  containing  two  molecules 
of  water.  It  is  bibasic,  and  yields  chiefly  acid  salts,  which  are  obtained 
by  treating  the  corresponding  acetates  with  barbituric  acid. 

Barbituric  acid  is  converted  by  fuming  nitric  acid  into  dilituric  acid,  by 
potassium  nitrate  into  potassium  violurate.  When  boiled  with  potash  it 
gives  off  ammonia,  and  yields  the  potassium-salt  of  malonic  acid,  C3H404 

*  For  descriptions  of  these  several  products,  see  Watts's  Dictionary  of  Chemistry. 


732  COMPOUND   AMMONIAS    OR   AMINES. 

(D   661)  whence  it  appears  to  have  the  constitution  of  malonyl  urea,  CN2H2 

(CX°*)"°  =  C2HA  +  CN2H4°  —  2H2°' 

MUREXIDE,  C8N6H806 .  Aq. ;  Prout's  Purpurate  of  Ammonia.— There  are 
several  methods  of  preparing  this  magnificent  compound.  It  may  be  made 
directly  from  uric  acid,  by  dissolving  that  substance  in  dilute  nitric  acid, 
evaporating  to  a  certain  point,  and  then  adding  to  the  warm  but  not  boil- 
ing liquid  a  very  slight  excess  of  ammonia.  In  this  process  alloxantin  is 
first  produced,  and  is  afterward  partially  converted  into  alloxan:  the  pres- 
ence of  both  is  requisite  for  the  production  of  murexide.  This  process 
is,  however,  very  precarious,  and  often  fails  altogether.  An  excellent 
method  is  to  boil  for  a  few  minutes  in  a  flask  a  mixture  of  1  part  of  dry 
uramile,  1  part  of  red  oxide  of  mercury,  and  40  parts  of  water,  to  which 
two  or  three  drops  of  ammonia  have  been  added  :  the  whole  assumes  in  a 
short  space  of  time  an  intensely  deep  purple  tint,  and  when  filtered  boil- 
ing hot,  deposits,  on  cooling,  splendid  crystals  of  murexide,  unmixed  with 
any  impurity.  The  reaction  in  this  case  is : 

2C4N3H50,        +        0        =        C8N6H806        +        H20. 
Uramile.  Murexide. 

A  third,  and  perhaps  even  still  better  process,  is  that  of  Dr.  Gregory :  7 
parts  of  alloxan  and  4  parts  of  alloxantin  are  dissolved  in  240  parts  of  boil- 
ing water,  and  the  solution  is  added  to  about  80  parts  of  cold,  strong  solu- 
tion of  ammonium  carbonate :  the  liquid  instantly  acquires  such  a  depth 
of  color  as  to  become  opaque,  and  gives  on  cooling  a  large  quantity  of 
murexide:  the  operation  succeeds  best  on  a  small  scale. 

Murexide*  crystallizes  in  small  square  prisms,  which  by  reflected  light 
exhibit  a  splendid  green  metallic  lustre,  like  that  of  the  wing-cases  of  the 
rose-beetle  and  other  insects:  by  transmitted  light  they  are  deep  purple- 
red.  It  is  soluble  with  difficulty  in  cold  water,  much  more  easily  at  the 
boiling  heat,  insoluble  in  alcohol  and  ether.  Mineral  acids  decompose  it, 
with  separation  of  a  white  or  yellowish  substance  called  murexan,  probably 
identical  with  uramile,  and  caustic  potash  dissolves  it,  with  production  of  a 
most  magnificent  purple  color,  which  disappears  when  the  solution  is  boiled. 

A  few  years  ago,  murexide  was  extensively  used  in  dyeing ;  it  is  now 
rapidly  being  superseded  by  rosaniline,  the  crimson  derived  from  aniline. 

A  series  of  substances  closely  related  to  the  derivatives  of  uric  acid  will 
be  noticed  under  the  head  of  Caffeine. 


COMPOUND  AMMONIAS  or  AMINES. 

These  names  are  given  to  a  class  of  compounds  derived  from  ammonia, 
NH3,  by  substitution  of  alcohol-radicals  for  hydrogen,  these  radicals  being 
either  monatomic  or  polyatomic ;  the  substitution  may  take  place  in  one, 
two,  or  a  greater  number  of  ammonia  molecules,  thus  giving  rise  to  mona- 
mines,  diamines,  triamines,  &c.  Moreover,  the  nitrogen  in  these  bases  may 
be  replaced  by  phosphorus,  arsenic,  or  antimony,  giving  rise  to  phos- 
phines,  arsines,  and  stibines,  bases  analogous  in  composition  and  properties 
to  the  amines.  Connected  with  these  last-mentioned  bases  are  certain  com- 
pounds of  alcohol-radicals  with  metals  not  belonging  to  the  nitrogen  class. 
The  natural  organic  bases,  or  alkalo'ids,  found  in  plants,  and  certain  artifi- 
cial bases  whose  constitution  has  not  been  very  exactly  made  out,  will  be 
treated  in  an  appendix  to  the  alcoholic  ammonias. 

*  Po  called  from  the  Tyrian  dye,  said  to  have  been  prepared  from  a  species  of  murese,  or 
eliell-fish. 


AMINES. 


733 


AMINES  DERIVED  FROM  MONATOMIC  ALCOHOLS. 

Ammonia,  NH3,  may  give  up  one,  two,  or  three  of  its  hydrogen-atoms  in 
exchange  for  univalent  alcohol-radicals  (methyl  and  its  hoinologues,  for 
example),  producing  primary,  secondary,  and  tertiary  amines.  If  A,  B,  C, 
denote  three  such  alcohol-radicals,  the  amines  formed  by  substituting  them 
for  hydrogen  in  ammonia  will  be  represented  by  the  general  formulae : 

A  f  A  ( A 

B 

C 
Primary.  Secondary.  Tertiary. 

In  the  secondary  and  tertiary  amines  the  alcohol-radicals  denoted  by  A,  B, 
C  may  be  either  the  same  or  different ;  for  example  : 

Secondary.  Tertiary. 


NJH  N|B  H-J 

U  U  1 


fCH3 

JH  CH3 

IH 


CH8 
C..H, 


Diamethyl-      Methyl- 
amine.       ethylamine. 


•I 


CH 


CH 


(  CH, 
JCH, 

,3  (C2H5  5U 

Trimethyl-     Dimethyl-  Methyl-ethyl- 

amine.       ethylamine.    amylamine. 


f  CH, 
NJC2H5 
(C5HU 


It  is  clear  that  amines  containing  only  univalent  alcohol-radicals  must  be 
derived  from  only  one  molecule  of  ammonia :  for  to  bind  together  two  or 
more  such  molecules  would  require  the  introduction  of  a  polyatomic  radi- 


cal: thus, 


is   a   stable   compound,  but  such   a   compound   as 


N  •!  (C2H5)2  would  split  up  into  two  molecules,  each  consisting  of  N 


H 


In  other  words,  amines  derived  from  monatomic  alcohols  must  be  mona- 
mines. 

These  amines  are  basic  compounds  more  or  less  resembling  ammonia  in 
odor,  having  an  alkaline  reaction  on  vegetable  colors,  and  uniting  with 
acids  to  form  salts  which  are  analogous  in  composition  to  the  ammonium- 
salts,  and,  like  the  latter,  may  be  regarded  either  as  compounds  of  ammo- 
nia-molecules with  acids,  or  of  ammonium  molecules  with  halogen  elements 
and  acid  radicals  analogous  thereto  (see  p.  310) ;  thus: 

NH3  -f     HC1 

Ammonia. 

NH2(C2H5)     +     HC1 

Ethyl- 
ammonia. 

NH(C2H5)2     4-     HC1 

Diethyl- 
ammonia. 


=  NH4 .  Cl  Ammonium  chloride. 

=  NH3(C2H6) .  Cl     Ethylammonium  chloride. 

=  NH2(C2H6)2 .  Cl     Diethylammonium  chloride. 


N(C,H8)8 
Triethyl- 


-f     HC1         =  NH(C2H5)3 .  Cl      Triethylammonium  chloride. 


2N(C2H5)3 
Triethyl- 


H2S04     =  [NH(C2H6)3]2S04  Triethylammonium  sulphate. 


62 


734  AMINES. 

All  the  salts  of  these  amines,  when  heated  with  potash,  give  off  the  amine, 
just  as  ammonia-salts  give  off  ammonia. 

The  tertiary  amines  can  unite  with  the  chlorides,  &c.,  of  alcohol-radi- 
cals in  the  same  manner  as  with  acids :  thus  triethylamine,  N(C2H5)3.  unites 
directly  with  ethyl  iodide,  C2H5I,  forming  a  compound  which  may  be  re- 
garded either  as  triethylamine  ethyliodide,  N(C2H5)3  .  C2H5I,  or  as  tetrethyl- 
ammonium iodide,  N(C2H5)4.I.  Now  this  iodide,  when  heated  with  potash, 
does  not  give  off  ammonia  or  a  volatile  ammonia-base ;  but  when  heated 
with  silver  oxide  and  water,  it  is  converted,  by  exchange  of  iodine  for  hy- 
droxyl,  into  a  strongly  alkaline  base,  called  tetrethylammonium  hydrate,  which 
may  be  obtained  in  the  solid  state,  and  exhibits  reactions  closely  analogous 
to  those  of  the  fixed  caustic  alkalies.  Its  formation  is  represented  by  the 
equation : 

N(C2H5)4I      +      KOH       =       KI      -f      N(C2H5)4(OH). 

Moreover,  this  base  can  exchange  its  hydroxyl  for  chlorine,  bromine,  and 
other  acid  radicals,  just  like  potash  or  soda,  forming  solid  crystallizable 
salts  like  the  iodide  above  mentioned.  These  compounds,  containing  four 
equivalents  of  alcohol-radicals,  are,  in  fact,  analogous  in  every  respect  to 
ammonium-salts,  excepting  that  the  corresponding  hydrates  are  capable  of 
existing  in  the  solid  state,  whereas  ammonium  hydrate,  NH4(OH),  splits 
up,  as  soon  as  formed,  into  ammonia  and  water.  The  radicals  N(C2H6)4, 
&c.,  corresponding  to  ammonium,  are  not  known  in  the  free  state. 

The  monamines  containing  more  than  one  carbon-atom  are  susceptible 
of  isomeric  modifications  similar  to  those  of  the  alcohols  ;  thus  ethylamine, 
NH2(C2H6),  is  isomeric  with  dimethylamine,  NH(C2H3)2;  propylamine, 
NH2(C3H7),  is  isomeric  with  methyl-ethylamine,  NH(CH3)(C2H6),  and  with 
trimethylamine,  N(CH3)3,  &c.,  &c.,  the  number  of  possible' modifications 
of  course  increasing  with  the  complexity  of  the  molecules.  Moreover,  a 
monamine,  either  primary,  secondary,  or  tertiary,  may  admit  of  modifica- 
tion in  the  alcohol-radical  itself;  thus  the  primary  monamine,  NH2(G3H7), 
may  exhibit  the  two  following  modifications : 

rCH2CH2CH3  rCH(CH3)2 

N  •<  H  N  -I  H 

IH  (H 

Propylamine.  Isopropylamine. 

An  instance  of  isomerism  of  this  latter  kind  has  lately  been  observed  by 
Wurtz  in  amylamine,  NH2(C5Hn). 

Amines  may  of  course  be  formulated  on  the  methane  or  marsh-gas  type 
instead  of  the  ammonia  type,  the  radical  amidogen,  NH2,  and  others  de- 
rived from  it,  being  substituted  for  an  atom  of  hydrogen  ;  thus : 

H 


[NH2          lNH2  [NH(CH3)       LN(CH3)2 

Methane.      Methyl-        Ethyl-  Dimethyl-       Trimethyl- 

amine.        amine.  amine.  amine. 

This  mode  of  representation  is  convenient  in  some  cases,  but  the  amines 
and  their  salts  are  so  closely  related  to  the  ammonia-compounds  in  their 
modes  of  formation  and  transformation,  that  they  are  for  the  most  part 
more  appropriately  represented  by  formulas  derived  from  ammonia,  NH3, 
and  sal-ammoniac,  NH4C1. 

A  great  number  of  amines  and  their  salts  have  been  obtained,  but  the 
limits  of  this  work  will  not  allow  us  to  describe  more  than  the  most  impor- 


ETHYLAMINES.  735 

tant  of  those  containing  the  radicals,  methyl,  ethyl,  amyl,  and  phenyl.  In 
describing  them  it  will  be  convenient  to  make  a  slight  departure  from  the 
natural  order,  and  commence  with  the  ethyl  bases,  which  have  been  more 
completely  studied  than  their  homologues. 


BASES  OF  THE  ETHYL  SERIES. 

Ethylamine,  or  Ethyl-ammonia,  C2H7N  =  NH2(C2H6).— On  digesting 
ethyl  bromide  or  iodide  with  an  alcoholic  solution  of  ammonia,  the  alka- 
line reaction  of  the  ammonia  gradually  disappears ;  and  on  evaporating 
the  solution  on  the  water-bath,  a  white  crystalline  mass  is  obtained,  which 
consists  chiefly  of  ethyl-ammonium  bromide  or  iodide:  NH3 -f-  C2H6I  = 
NH3(C2H5)I.  On  distilling  this  salt  in  a  retort  provided  with  a  good  con- 
denser, with  caustic  lime,  the  ethylamine  is  liberated  and  distils  over: 

2NH3(C2H6)I     -f     CaO     =     2NH2(C2H5)     +     H20     Calr 

Another  method  of  preparing  this  compound,  and,  indeed,  the  method  by 
which  it  was  first  obtained  by  Wurtz,  consists  in  submitting  ethyl  cyanate 
to  the  action  of  potassium  hydrate.  Cyanic  acid  (p.  710),  when  treated 
with  boiling  solution  of  potash,  splits  into  carbon  dioxide  and  ammonia; 
and  ethyl  cyanate  (p.  714)  suffers-  a  perfectly  analogous  decomposition, 
yielding  carbon  dioxide  and  ethylamine : 

CNHO        -f        2KHO        ==        K2C03        +        NH3 
Cyanic  acid.  Ammonia. 

CN(C2H5)0         +    2KHO        =        K2C03        -f        NH2(C2H5) 
Ethyl  cyanate.  Ethylamine. 

Ethyl  cyanurate,  polymeric  with  the  cyanate,  likewise  gives  off  ethyl- 
amine when  boiled  with  potash. 

Ethylamine  is  a  very  mobile  liquid,  of  sp.  gr.  0-6964,  at  8°  C.  (46°  F.), 
boiling  at  19°  C.  (66°  F.).  The  specific  gravity  of  its  vapor  is  1-57.  It 
has  a  most  powerful  ammoniacal  odor,  and  restores  the  blue  color  to  red- 
dened litmus-paper.  It  produces  white  clouds  with  hydrochloric  acid,  and 
is  absorbed  by  water  with  great  avidity.  With  acids  it  forms  a  series  of 
neutral  crystallizable  salts  perfectly  analogous  to  those  of  ammonium. 

Ethylamine  imitates,  moreover,  in  a  remarkable  manner,  the  deportment 
of  ammonia  with  metallic  salts.  It  precipitates  the  salts  of  magnesium, 
aluminium,  iron,  manganese,  bismuth,  chromium,  uranium,  tin,  lead,  and 
mercury;  zinc-salts  yield  a  white  precipitate,  which  is  soluble  in  excess. 
Like  ammonia,  ethylamine  dissolves  silver  chloride,  and  yields  with  cop- 
per-salts a  blue  precipitate,  which  is  soluble  in  an  excess  of  ethylamine. 
On  adding  ethylamine  to  oxalic  ether,  a  white  precipitate  of  biethyl-oxamide, 
N2(C2^2)//H2(C2H5)2,  is  produced:  a  compound  analogous  to  oxamic  acid 
(p.  659)  has  also  been  obtained.  Ethylamine  may,  however,  be  readily 
distinguished  from  ammonia:  its  vapor  is  inflammable,  and  it  produces 
with  platinic  chloride,  a  salt,  [NH3(C2H5)Cl]2PtCl4,  crystallizing  in  golden 
scales,  which  are  rather  soluble  in 'water.  Treated  with  chlorine,  it  yields 
ethyl-ammonium  chloride  and  bichlor  ethylamine,  NC12C2II5,  a  yellow  liquid 
having  a  penetrating,  tear-exciting  odor.  When  treated  with  potash,  it  is 
converted  into  ammonia,  potassium  acetate,  and  potassium  chloride:  NCL 
(C2H5)  +  3KHO  =  C2H3K02  +  2KC1  -f  Nil,  +  H20. 

Ethyl-urea. — On  passing  the  vapor  of  cyanic  acid  into  a  solution  of 
ethylamine,  the  liquid  becomes  hot,  and  deposits,  after  evaporation,  fine 


736  ETHYLAMINES. 

crystals  of  ethyl-urea:  C2H7N  +  CNHO  =  C3H8N20  =  CH3(C2H5)N,0. 
This  substance,  which  may  be  viewed  as  ordinary  urea  (p.  721 ),  having  1 
atom  of  hydrogen  replaced  by  ethyl,  may  also  be  prepared  by  treating 
cyanic  ether  with  ammonia:  CN(C2H5)0  -f-  NH3  =  C3H8N20.  Ethyl-urea 
is  very  soluble  in  wrater  and  alcohol :  the  concentrated  aqueous  solution, 
unlike  that  of  ordinary  urea,  yields  no  precipitate  with  nitric  acid ;  but  on 
gently  evaporating  the  mixture,  a  very  soluble  crystalline  nitrate  of  ethyl- 
urea  is  obtained.  Boiled  with  potash,  this  substance  yields  a  mixture  of 
equivalent  quantities  of  ammonia  and  ethylamine :  C3H8N20  -f  2KHO  = 
K2C03  +  NH3  +  C2H7N. 

Biethylamine,  C4HnN  =  NH(C2H5)?.— A  mixture  of  the  solutions  of 
ethylamine  and  ethyl  bromide,  heated  in  a  sealed  tube  for  several  hours, 
solidifies  to  a  crystalline  mass  of  biethyl-ammonium  bromide:  NH2C2H6  -(- 
C2H6Br  =  NH2(C2H5)2Br.  This  bromide,  distilled  with  potash,  yields 
biethylamine  as  a  colorless  liquid,  still  very  alkaline,  and  soluble  in  water, 
but  less  so  than  ethylamine.  This  compound  boils  at  57-5°  C.  (135°  F.). 
It  forms  beautifully  crystallizable  salts  with  acids.  A  solution  of  biethyl- 
ammonium  chloride  forms  with  platinic  chloride  a  very  soluble  double  salt, 
2NH2(C2H5)2C1  .  PtCl4,  crystallizing  in  orange-red  grains,  very  different 
from  the  orange-yellow  leaves  of  the  corresponding  ethyl-ammonium  salt. 

Biethyl-urea.  —  Biethylamine  behaves  with  cyanic  acid  like  ammonia  and 
ethylamine,  giving  rise  to  biethyl-urea.  A  substance  similar  to,  but  not 
identical  with,  the  former,  has  been  produced  by  the  action  of  cyanic  ether 
upon  ethylamine :  CN(C2H5)0  +  C2H7N  =  C6H12N20  =  C[H2(C2H6)2]N20. 
The  biethyl-ureas  are  very  crystallizable,  and  readily  form  crystalline  ni- 
trates. Boiled  with  potash,  the  biethyl-ureas  yield,  the  former  1  molecule 
of  biethylamine  and  1  molecule  of  ammonia,  C[H2(C2H5)2]N20  -f-  2KHO  = 
K2C03+  NH(C2H6)24-  NH3;  the  latter,  pure  ethylamine,  C[H2(C2H5)2] 
N20  +  2KHO  =  K2C03  +  2NH2(C2H5), 

Triethylamine,  C6H15N  =  N(C2H6)S. —  The  formation  of  this  body  is  per- 
fectly analogous  to  that  of  ethylamine  and  of  biethylamine.  On  heating 
for  a  short  time  a  mixture  of  biethylamine  with  ethyl  bromide  in  a  sealed 
glass  tube,  a  beautiful  fibrous  mass  of  triethyl-ammonium  bromide  is  ob- 
tained, from  which  the  triethylamine  may  be  separated  by  potash.  Tri- 
ethylamine is  a  colorless,  powerfully  alkaline  liquid,  boiling  at  91°  C.  (196° 
F.).  The  salts  of  this  base  crystallize  remarkably  well.  "With  platinic 
chloride  it  forms  a  very  soluble  double  salt,  2NH(C2H6)3C1 .  PtCl4,  which 
crystallizes  in  magnificent,  large,  orange-red  rhombs. 

The  action  of  ethyl  iodide  or  bromide  on  ammonia  gives  rise  to  the  si- 
multaneous formation  of  the  three  ethylated  bases,  which,  though  differing 
considerably  in  their  boiling  points,  can  scarcely  be  separated  by  fractional 
distillation.  The  separation  succeeds,  however,  by  digesting  the  mixture 
of  these  three  bases  with  anhydrous  ethyl  oxalate.  Ethylamine  is  thus 
converted  into  diethyloxamine : 

C204(C2H5)2    -f    2NH2(C2H6)    =    202H6(OH)    -f    N2(C202)"H2(C2H5)2 
Ethyl  oxalate.  Ethyl-  Alcohol.  Diethyl-oxamide. 

amine. 

and  diethylamine  forms  diethyloxamate: 

C204(C2H5)2   +    NH(C2H5)2  =  C2H5(OH)  +  C202[N(C2H5)2](OC2H5) 
Ethyl  oxalate.          Diethyl-  Alcohol.          Ethylic  diethyloxamate ; 

amine. 

whereas  triethylamine  does  not  combine  with  oxalic  ether.  The  separation 
is  carried  out  in  the  following  manner  : 

On  distilling  the  product  of  the  reaction  of  ethyl  oxalate  upon  the  mix- 


METHYLAMINE.  737 

ture  of  ethyl  bases  in  the  water-bath,  pure  triethylamine  passes  over;  and 
on  treating  the  residue  with  boiling  water,  diethyloxamide  is  dissolved, 
while  ethyl  diethyloxamate  remains  as  an  insoluble  layer  floating  upon  the 
hot  solution  :  it  may  be  separated  by  a  tap-funnel.  Diethyloxamide  treated 
with  potash  yields  pure  ethylamine,  while  pure  diethylamine  is  obtained 
by  treating  ethylic  diethyloxamate  with  the  same  reagent. 

Tetrethyl-ammonium  Hydrate,  C8H2INO  —  N(C2H5)4(OH).  —  When  anhy- 
drous triethylamine  is  mixed  with  dry  ethyl  iodide,  a  powerful  reaction 
ensues,  the  mixture  enters  into  ebullition,  and  solidifies  on  cooling  to  a 
white  crystalline  mass  of  tetrethyl-ammonium  iodide:  N(C2H5)3 -(-  C2H5I 
=i  N(G2H5)4I.  This  iodide  is  readily  soluble  in  hot  water,  from  which  It 
crystallizes  on  cooling  in  beautiful  crystals  of  considerable  size.  This  sub- 
stance is  not  decomposed  by  potash :  it  may  be  boiled  with  the  alkali  for 
hours  without  yielding  a  trace  of  volatile  base.  The  iodine  may,  however, 
be  readily  removed  by  treating  the  solution  with  silver-salts.  If  in  this 
case  silver  sulphate  or  nitrate  be  used,  we  obtain,  together  with  silver 
iodide,  the  sulphate  or  nitrate  of  tetrethyl-ammonium,  which  crystallizes  on 
evaporation:  on  the  other  hand,  if  the  iodide  be  treated  with  freshly  pre- 
cipitated silver  oxide,  the  hydrate  of  tetrethyl-ammonium  itself  is  sepa- 
rated. On  filtering  off  the  silver  precipitate,  a  clear  colorless  liquid  is  ob- 
tained, which  contains  the  isolated  base  in  solution.  It  has  a  strongly  alka- 
line reaction,  and  intensely  bitter  taste.  The  solution  of  tetrethyl-ammo- 
nium hydrate  has  a  remarkable  analogy  to  potash  and  soda.  Like  these 
substances,  it  destroys  the  epidermis  and  saponifies  fatty  substances,  with 
formation  of  true  soaps.  With  metallic  salts  it  exhibits  exactly  the  same 
reactions  as  potash.  On  evaporating  a  solution  of  the  base  in  a  vacuum, 
long  slender  needles  are  deposited,  which  are  evidently  the  hydrate  with 
an  additional  amount  of  crystallization  water.  After  some  time  these  nee- 
dles disappear  again,  and  a  semi-solid  mass  is  left,  which  is  the  hydrate 
of  tetrethyl-ammonium.  A  concentrated  solution  of  this  substance  in 
water  may  be  boiled  without  decomposition,  but  on  heating  the  dry  sub- 
stance, it  is  decomposed  into  pure  triethylamine,  water,  and  olefiant  gas : 

N(C2H5)4(OH)       ==      H20      +      N(C2H5)3      +      C2H4. 

Tetrethyl-ammonium  hydrate  forms  neutral  salts  with  acids.  These  salts 
are  mostly  very  soluble ;  several  yield  beautiful  crystals.  The  platinum- 
salt,  2N(C2H5)4C1 .  PtCl4,  forms  orange-yellow  octohedrons,  which  are  about 
as  soluble  as  the  corresponding  potassio-platinic  salt. 


BASES  OF  THE  METHYL  SERIES. 

Methylamine,  CH5N=rNH2(CH3).  —  The  formation  and  the  method  of  pre- 
paring this  compound  from  methyl  cyanate  are  perfectly  analogous  to  those 
of  ethylamine  (p.  735) :  however,  methylamine  being  a  gas  at  the  common 
temperature,  it  is  necessary  to  cool  the  receiver  by  a  freezing  mixture. 
The  distillate,  which  is  an  aqueous  solution  of  methylamine,  is  saturated 
with  hydrochloric  acid,  and  evaporated  to  dryness.  A  crystalline  residue 
is  thus  obtained,  consisting  of  methylammonium  chloride,  and  this,  when 
distilled  with  dry  lime,  yields  methylamine  gas,  which,  like  ammonia  gas, 
must  be  collected  over  mercury.  It  is  distinguished  from  ammonia  by  a 
slightly  fishy  odor,  and  by  the  facility  with  which  it  burns.  Methylamine 
is  liquefied  at  about  — 18°:  its  sp.  gr.  is  1-08.  This  substance  is  the  most 
soluble  of  all  gases;  at  12° C.  (54°  F.),  one  volume  of  water  absorbs  1040 
62* 


738  AMYLAMINES. 

volumes  of  the  gas.  It  is  likewise  very  readily  absorbed  by  charcoal.  In 
its  chemical  deportment  with  acids  and  other  substances,  methylamine 
resembles  in  every  respect  ammonia  and  ethylamine.  Methylamine  ap- 
pears to  be  produced  in  a  great  number  of  processes  of  destructive  distilla- 
tion :  it  has  been  formed  by  distilling  several  of  the  natural  organic  bases, 
such  as  codeine,  morphine,  caffeine,  and  several  others,  with  caustic  potash  ; 
frequently  a  mixture  of  several  bases  is  produced  in  this  manner. 

Among  the  numerous  derivatives  already  obtained  with  this  substance, 
methyl-urea,  CH3(CH3)N20,  bimethyl-urea,  CH2(CH3)2N20,  and  methyl- ethyl- 
urea]  CH2(CH3)(C2H5]N20,  may  be  mentioned.  The  latter  substance  has  been 
produced  by  t«he  action  of  ethyl  cyanate  upon  methylamine.  A  series  of 
platinum-bases,  analogous  to  those  produced  by  the  action  of  ammonia 
upon  platinous  chloride  (p.  426),  have  likewise  been  obtained  with  methyl- 
amine. 

Bimethylamine,  C2H7N— NH(CH3)2. —  This  compound,  isomeric  with  ethyl- 
amine, is  prepared  by  the  action  of  ammonia  on  methyl  iodide.  Its  sepa- 
ration from  the  methylamine  and  trimethylamine  simultaneously  formed,  is 
accomplished  by  means  of  oxalic  ether  (p.  735). 

Trimethylamine,  C3H9N  —  N(CH3)3.  —  This  substance  is  readily  obtained 
in  a  state  of  perfect  purity,  by  submitting  tetramethyl-ammonium  hydrate 
to  the  action  of  heat.  It  is  gaseous  at  the  common  temperature,  but  lique- 
fies at  about  90°  C.  (194°  F.),  to  a  mobile  liquid  of  very  powerfully  alkaline 
reaction.  Trimethylamine  produces  very  soluble  salts  with  acids.  The 
platinum-salt,  2NH(CH3)3C1 .  PtCl4,  is  likewise  very  soluble,  and  crystallizes 
in  splendid  orange-red  octohedrons.  According  to  Mr.  Winkles,  large  quan- 
tities of  trimethylamine  are  found  in  the  liquor  in  which  salt  herrings  are 
preserved. 

Tetramethyl-ammonium  Hydrate,  C4H13NO  —  N(CH3)4(OH).— The  corre- 
sponding iodide  may  be  obtained  by  adding  methyl  iodide  to  trimethylamine. 
The  two  substances  unite  with  a  sort  of  explosion.  The  same  iodide  is 
prepared,  however,  with  less  difficulty,  simply  by  digesting  methyl  iodide 
with  an  alcoholic  solution  of  ammonia.  In  this  reaction  a  mixture  of  the 
iodides  of  ammonium,  methyl-ammonium,  bimethyl-ammonium,  trimethyl- 
ammonium,  and  tetramethyl-ammonium  is  produced.  The  first  and  last 
compounds  are  formed  in  largest  quantity,  and  may  be  separated  by  crys- 
tallization, the  iodide  of  tetramethyl-ammonium  being  but  sparingly  soluble 
in  water.  From  the  iodide  the  base  itself  is  separated  by  means  of  silver 
oxide.  Its  properties  are  similar  to  those  of  the  corresponding  ethyl-com- 
pound. It  differs,  however,  from  tetrethyl-ammonium  hydrate  in  its  be- 
havior when  heated  (p.  737),  yielding  trimethylamine  and  pure  methyl 
alcohol,  N(CH3)4OH=N(CH3)3+CH3(OH). 


BASES  OF  THE  AMYL  SERIES. 

The  formation  of  these  bodies  being  perfectly  analogous  to  that  of  the 
corresponding  terms  in  the  ethyl  series,  we  refer  to  the  fuller  statement 
given  on  page  735,  and  confine  ourselves  to  a  brief  description  of  their 
principal  properties. 

Amylamine,  CJI^N  =  NH2(C5Hn),  is  a  colorless  liquid  of  peculiar,  pene- 
trating, aromatic  odor,  slightly  soluble  in  water,  to  which  it  imparts  a 
strong  alkaline  reaction.  With  the  acids  it  forms  crystalline  salts,  which 
have  a  fatty  lustre.  Amylamine  boils  at  93°  C.  (199°  F.). 

An  amylamine-urea  has  beeu  prepared. 


AROMATIC   AMINES.  739 

Biamylamine,  C^H^N  =  NH(C5Hn)2. — An  aromatic  liquid,  less  soluble 
in  water,  and  less  alkaline  than  amylamine.  It  boils  at  about  170°  C. 
(338°  P.). 

Triamylamine,  C^H^N  =  N(C5Hn)3. — A  colorless  liquid,  of  properties 
similar  to  those  of  the  two  preceding  bases,  but  boiling  at  257°  C.  (495°  F.). 
The  salts  of  triamylamine  are  very  sparingly  soluble  in  water,  and  fuse,, 
when  heated,  to  colorless  liquids,  floating  upon  water. 

Tetramyl-ammonium  Hydrate,  C20H45NO  =  N(C6Hn)4OH. — This  sub- 
stance is  far  less  soluble  than  the  corresponding  bases  of  the  methyl  and 
ethyl  series,  and  separates  as  an  oily  layer  on  adding  potash  to  the  aque- 
ous solution.  On  evaporating  the  solution  in  an  atmosphere  free  from  car- 
bonic acid,  the  alkali  may  be  obtained  in  splendid  crystals  of  considerable 
size.  When  submitted  to  distillation,  it  splits  into  water,  triamylamine,  and 
amylene : 

N(CBH11)4OH        =        H20        +        N(C5Hn)3        +        C5H10. 

In  addition  to  the  bases  already  enumerated,  the  following  have  been  ob- 
tained by  analogous  processes,  viz.,  treatment  of  the  iodides  of  the  corre- 
sponding alcohol-radicals  with  ammonia :  propylamine,  C3H9N,  hexal- 
amine,  C6H15N,  heptylamine,  C7H17N,  octylamine,  C8H19N,  and  nonylamine, 


BASES  OF  THE  AROMATIC  SERIES. 

In  speaking  of  the  aromatic  hydrocarbons,  we  have  explained  that  each 
of  the  hydrocarbons  homologous  with  benzene  may  be  regarded  as  a  com- 
pound of  phenyl  with  one  or  more  alcohol-radicals  of  the  methyl  series, 
and  may  give  rise  to  two  series  of  derivatives,  accordingly  as  the  hydro- 
gen in  the  phenyl  or  in  the  alcohol-radical  is  replaced:  thus  from  toluene 
or  methyl-phenyl,  C6H5.CH3,  are  derived  chlorotoluene,  C6H4C1.CH3,  iso- 
meric  with  benzyl  chloride,  CgH5.  CH2C1,  —  and  cresol,  C6H4OH  .  CH3,  iso- 
meric  with  benzyl  alcohol,  C6H6,CH2OH.  Each  of  these  hydrocarbons 
can  in  like  manner  yield  two  isomeric  bases,  accordingly  as  an  atom  of  hy- 
drogen in  one  part  or  the  other  of  its  molecule  is  replaced  by  amidogen, 
$H2:  thus  from  toluene  are  derived  two  bases  containing  C7H9N,  viz. : 
C6H4(NH2)  .  CH3  C6H5 .  CH2NH2 

Toluidine.  Benzylamine. 

The  second  of  these,  benzylamine,  is  analogous  in  its  mode  of  formation, 
and  all  its  principal  characters,  to  the  bases  of  the  methyl  series,  and  may 
be  represented  by  the  formula  NH2(C7H7),  derived  from  ammonia  by  sub- 
stitution of  the  univalent  radical,  benzyl,  C7H7,  for  hydrogen.  But  tolu- 
idine  is  formed  in  a  different  manner,  viz.,  by  the  action  of  reducing  agents 
on  nitrotoluene,  and  differs  in  its  chemical  relations  from  benzylamine, 
much  in  the  same  manner  as  cresol  from  benzyl  alcohol,  being  altogether  a 
less  active  substance. 

Xylidine,  C8HUN  =  C6H8(NH2)  .  (CH3)2  ;  cumidine,  C9H,3N  =  C6H4 
(NH2) .  C3H7,  and  cymidine,  C10H15N,  bases  homologous  with  toluidine,  are 
obtained  in  like  manner  from  the  nitro-derivatives  of  the  corresponding 
hydrocarbons.  The  corresponding  bases  homologous  with  benzylamine 
have  not  yet  been  obtained. 

Aniline,  C6H7N.  —  There  is  but  one  aromatic  monamine  containing  six 
atoms  of  carbon,  viz.,  aniline,  C6H7N  ;  and  this  may  be  regarded  indiffer- 
ently, either  as  amidobenzene,  C6H6(NH2),  or  as  phenylamine,  N  <  „  Vr  ,  that 


740  ANILINE. 

is  to  say,  as  a  lower  homologue  either  of.  toluidine  or  benzylamine.  The 
two  formulae  just  given  are  in  fact  identical;  and  moreover  aniline,  both 
in  its  modes  of  formation  and  in  its  properties,  exhibits  resemblances,  on 
the  one  hand  to  toluidine  and  its  homologues,  and  on  the  other  to  benzyl- 
amine and  the  monamines  of  the  methylic  series. 

Aniline  is  produced:  1.  By  heating  phenol  with  ammonia  in  sealed  tubes: 

C6H6(OH)        +        NH3        =        H20        +        NH2(C6H5). 

2.  By  the  action  of  hydrogen  sulphide  and  other  reducing  agents  on  nitro- 
benzene: 

C6H5(N02)     +     3H2S     =     2H20     +     S3     +     C6H5(NH2). 

The  first  of  these  reactions  exhibits  the  relation  of  aniline  to  benzylamine: 
the  second,  its  relation  to  toluidine. — 3.  By  the  action  of  caustic  potash 
upon  indigo : 

C8H5NO    +    4KHO   -f-    H20    =    C6H7N  =   2C03K2   +    2H2. 
Indigo.  Aniline. 

The  name  aniline  indicates  the  relation  of  this  compound  to  the  indigo 
group,  the  botanical  name  of  the  indigo-plant  being  Indiyofera  anil. 

Preparation, — 1.  From  indigo. — Powdered  indigo  boiled  with  a  highly 
concentrated  solution  of  potassium  hydrate  dissolves,  with  evolution  of  hy- 
drogen, to  a  brownish-red  liquid  containing  anthranilic  acid.  If  this  mat- 
ter be  transferred  to  a  retort  and  still  further  heated,  it  swells  up  and  gives 
off  aniline,  which  condenses  in  the  form  of  oily  drops  in  the  neck  of  the 
retort  and  in  the  receiver.  Separated  from  the  ammoniacal  water  by  which 
it  is  accompanied,  and  redistilled,  it  is  obtained  nearly  colorless. 

2.  In  order  to  prepare  aniline  from  nitrobenzene  (see  p.  495),  this  sub- 
stance is  submitted  to  a  process  discovered  by  Zinin,  which  has  proved  a 
very  abundant  source  of  artificial  organic  bases.  An  alcoholic  solution  of 
nitrobenzene  is  treated  with  ammonia  and  sulphuretted  hydrogen,  until  after 
some  hours  a  precipitation  of  sulphur  takes  place.  The  brown  liquid  is 
now  again  saturated  with  sulphuretted  hydrogen,  and  the  process  repeated 
until  sulphur  is  no  longer  separated.  The  reaction  may  be  remarkably 
accelerated  by  occasionally  heating  or  distilling  the  mixture.  The  liquid 
is  then  mixed  with  excess  of  acid,  filtered,  boiled  to  expel  alcohol  and  un- 
altered nitrobenzene,  and  then  distilled  with  excess  of  caustic  potash. 

If  the  aniline  be  required  quite  pure,  it  must  be  converted  into  oxalate, 
the  salt  several  times  crystallized  from  alcohol,  and  again  decomposed  by 
potash. 

Be"champ  has  shown  that  the  reduction  of  nitrobenzene  may  be  effected 
even  more  conveniently  by  the  action  of  ferrous  acetate.  The  distillation  of 
one  part  of  nitrobenzene,  one  part  of  acetic  acid,  and  one  and  a  half  part 
of  iron  filings,  seems,  in  fact,  to  be  the  best  process  for  preparing  aniline.* 
The  mass  swells  violently,  and  very  capacious,  retorts  are  required. 

Aniline  exists  among  the  products  of  the  distillation  of  coal,  and  probably 
of  other  organic  matters:  it  is  formed  in  the  distillation  of  anthranilic  acid, 
and  occasionally  in  other  reactions. 

Aniline,  when  pure,  forms  a  thin,  oily,  colorless  liquid,  of  faint  vinous 
odor,  and  aromatic,  burning  taste.  It  is  very  volatile,  but  has,  neverthe- 
less^ high  boiling  point  (182°C.  [260°  F.]).  In  the  air  it  gradually  becomes 
yellow  or  brown,  and  acquires  a  resinous  consistence.  Its  density  is  1-028. 
Water  dissolves  aniline  to  a  certain  extent,  and  also  forms  with  it  a  kind  of 
hydrate:  alcohol  and  ether  are  miscible  with  it  in  all  proportions.  It  is 

*  According  to  Schoiiror-Kostncr,  the  treatment  of  nitrobenzene  with  a  very  large  quantity 
of  iron  filings  ami  acetic  arid  reproduces  benzene  and  ammonia. 


IULJ 


ANILINE.  741 

destitute  of  alkaline  reaction  to  test-paper,  but  is  quite  remarkable  for  the 
number  and  beauty  of  the  crystallizable  compounds  which  it  forms  with 
acids.  Two  extraordinai-y  reactions  characterize  this  body  and  distinguish 
it  from  all  others  —  viz.,  that  with  chromic  acid,  and  that  with  solution  of 
calcium  hypochlorite.  The  former  gives  with  aniline  a  deep-greenish  or 
bluish-black  precipitate,  and  the  latter  an  extremely  beautiful  violet-colored 
compound,  the  fine  tint  of  which  is,  however,  very  soon  destroyed.  When 
nitrous  acid  is  passed  into  aniline,  or  when  aniline  hydrochloride  is  treated 
with  silver  nitrate,  water  and  phenol  are  produced,  and  nitrogen  is  evolved: 

C6H7N      +      N02H      =      C6H60      +      H20      -f      N2. 

On  the  other  hand,  when  nitrous  acid  is  passed  through  an  alcoholic  solu- 
tion of  aniline,  2  molecules  of  aniline  are  linked  together,  3  atoms  of  the 
hydrogen  being  replaced  by  1  atom  of  nitrogen.  Azodiphenyldiamine,  the 
substance  thus  produced,  contains  C12HUN3.  The  following  equation  re- 
presents its  formation : 

2C6H7N        +        N02H        =         C12HUN3        +        2H20. 

By  treatment  of  azodiphenyldiamine  with  nitrous  acid,  the  same  change  is 
repeated  once  more,  three  additional  atoms  of  hydrogen  being  again  re- 
placed by  one  of  nitrogen,  whereby  a  new  substance,  C12H8N4,  is  formed 
according  to  the  equation : 

C12HUN3        +        N02H        =        C12H8N4        +        2H20. 

Th'is  body  is  remarkable  for  the  violence  with  which,  like  fulminate  of 
silver,  it  explodes.  Griess,  who  discovered  these  substances,  has  succeeded 
in  obtaining  similar  compounds  from  several  others  of  the  basic  derivatives 
of  aniline. 

Paraniline.  —  In  the  manufacture  of  aniline  upon  a  large  scale,  several 
bases,  having  much  higher  boiling  points  than  aniline,  are  formed;  among 
them  there  is  a  beautifully  crystalline  compound  called  paraniline,  poly- 
meric with  aniline  and  represented  by  the  formula  C12H,4N2  =  2C6H7N. 
It  forms  two  series  of  salts,  of  which  the  hydrochlorides,  Ci2HuN2.  HC1  and 
C12H14N2 .  2HC1,  may  be  quoted  as  examples. 


Substitution-products  of  Aniline. 

Under  the  head  of  indigo,  a  product  of  oxidation  of  this  substance  will 
be  noticed,  to  which  the  name  isatin  has  been  given.  When  isatin  is  dis- 
tilled with  an  exceedingly  concentrated  solution  of  caustic  potash,  it  is,  like 
indigo,  resolved  into  aniline,  carbon  dioxide,  and  free  hydrogen.  In  like 
manner,  chlorisatin  and  dichlorisatin,  similarly  treated,  yield  products  anal- 
ogous to  aniline,  but  containing  one  or  two  atoms  of  chlorine  respectively 
in  the  place  of  hydrogen.  The  chloraniline,  C6H6C1N,  and  dichloraniline, 
C6H5C12N,  thus  produced,  cannot,  however,  be  obtained  by  the  direct  action 
of  chlorine  upon  aniline,  thus  differing  from  ordinary  substitution-com- 
pounds; but  aniline  may  be  reproduced  from  them  by  the  same  reagent 
that  is  capable  of  reconverting  chloracetic  acid  into  ordinary  acetic  acid  — 
namely,  an  amalgam  of  potassium  or  sodium  (see  p.  613).  They  are  the 
first  cases  on  record  of  organic  bases  containing  chlorine. 

Chloraniline  forms  large,  colorless  octohedrons,  having  exactly  the  odor 
and  taste  of  aniline,  very  volatile,  and  easily  fusible  :  it  distils  without  de- 
composition at  a  high  temperature,  and  burns,  when  strongly  heated,  with 
a  red  smoky  flame  with  greenish  border.  It  is  heavier  than  water,  in- 
different to  vegetable  colors,  and,  except  in  being  solid  at  common  tempera- 
tures, resembles  aniline  in  the  closest  manner.  It  forms  numerous  and 


742  TOLUIDINE. 

beautiful  crystallizable  salts.  If  aniline  be  treated  with  chlorine  gas,  the 
action  goes  further,  trichloraniline,  C6H4C13N,  being  produced,  a  volatile 
crystalline  body  which  has  no  longer  any  basic  properties.  The  corre- 
sponding bromine  compounds  have  also  been  formed  and  described. 

Nitraniline,  C6H6(N02)N.  —  This  compound  is  formed  by  the  action  of 
ammonium  sulphide  on  dinitrobenzene,  C6H4(N02)2  (p.  495).  The  attempts 
to  prepare  it  directly  from  aniline  by  means  of  nitric  acid  were  unsuccess- 
ful, the  principal  product  being  usually  picric  acid.  It  forms  yellow, 
acicular  crystals,  but  little  soluble  in  cold  water,  although  easily  dissolved 
by  alcohol  and  ether.  When  warmed  it  exhales  an  aromatic  odor,  and 
melts.  At  a  higher  temperature  it  distils  unchanged.  By  very  gentle  heat 
it  may  be  sublimed  without  fusion.  It  is  heavier  than  water,  does  not 
affect  test-paper,  and  like  chlor-  and  brom-aniline  fails  to  give  with  cal- 
cium hypochlorite  the  characteristic  reaction  of  the  normal  compound. 
Nitraniline  forms  crystallizable  salts,  of  which  the  hydrochloride  is  the 
best  known. 

Diphenylamine,  NH(C6H6)2,  is  produced  by  the  distillation  of  triphenyl- 
rosaniline  (aniline  blue).  It  is  a  crystalline  body,  melting  at  45°  C.  (113°  F.) 
to  a  yellow  oil,  which  boils  constantly  at  810°  C.  (590°  F.).  A  substance 
possessing  the  composition  of  triphenylamine,  C18H15N,  but  probably  not  con- 
nected with  the  phenyl  series,  is  formed  by  submitting  the  compound  pro- 
duced by  the  action  of  cinnamic  aldehyde  upon  ammonium  sulphite  to  de- 
structive distillation,  together  with  an  excess  of  lime. 

Cyananiline  is  formed  by  the  action  of  cyanogen  upon  aniline  :  it  is  a 
crystalline  substance  capable  of  combining  with  acids  like  aniline,  but  very 
prone  to  decomposition.  It  contains  C14H,4N2  —  (C6H7N)2 .  Cy2,  and  is 
therefore  a  compound  of  cyanogen  with  aniline,  not  a  substitution-deri- 
vative. 

Derivatives  of  Aniline  containing  Alcohol-radicals. — By  treating  aniline  with 
iodide  or  bromide  of  methyl,  ethyl,  &c.,  in  different  proportions,  bases  are 
pbtained  in  which  the  hydrogen  of  the  aniline  is  more  or  less  replaced  by 
those  radicals.  Ethylaniline,  C6H6(C2H5)N,  or  NH(C2H5)(C6H5),  and  Methyl- 
aniline,  N(C2H6)2(C6H5),  are  liquids  greatly  resembling  aniline ;  the  former 
boils  at  204°  C.  (399°  F.) ;  the  latter  at  213-5°  C.  (416°  F.).  Ethylaniline 
treated  with  amyl  iodide  yields  the  hydriodide  of  ethyl-amyl-aniline,  N(C2H5) 
(C5Hn)(C6H5) .  HI,  or  iodide  of  ethyl-amyl-phenylammonium,  NH(C2H6)(C5Hn) 
(C6H5)I,  from  which  the  ethyl-amyl-aniline  may  be  separated  by  distilla- 
tion with  potash.  It  is  an  aromatic  oil  boiling  at  262°  C.  (504°  F.).  "When 
treated  with  methyl  iodide,  it  is  converted  into  iodide  of  methyl- ethyl- amyl- 
phenylammonium,  N(CH3)(C2H5)(C5Hn)(C6H5)I,  from  which  the  correspond- 
ing hydrate,  N(CH3)(C2H5)(C5H,1)(C6H5) .  OH,  may  be  obtained  by  treat- 
ment with  silver  oxide  and  water.  This  hydrate  is  very  soluble  in  water, 
powerfully  alkaline,  and  has  an  extremely  bitter  taste. 

Many  other  substitution-derivatives  of  aniline  maybe  obtained  in  a  simi- 
lar manner. 

Toluidine,  C7H9N,  or  Amido toluene,  C7H7(NH2)  =  C6H4(NH2) .  CH3.— This 
base  is  homologous  with  aniline,  and  is  obtained,  similarly  to  the  latter,  by 
the  action  of  hydrogen  sulphide  or  ferrous  acetate  on  nitrotoluene,  C7H7(N02). 

It  forms  colorless  platy  crystals,  very  sparingly  soluble  in  water,  easily 
in  alcohol,  ether,  and  oils  :  it  is  heavier  than  water,  has  an  aromatic  taste 
and  odor,  and  a  very  feeble  alkaline  reaction.  At  40°  C.  (104°  F.)  it  melts, 
and  at  205°-206°  C.  (402°  F.),  boils  and  distils  unchanged.  It  forms  well- 
crystallized  salts,  but  is  nevertheless  a  weak  base,  and,  according  to  Wanklyn, 
is  absolutely  incapable  of  neutralizing  dilute  sulphuric  acid.  It  forms  sub- 
stitution-derivatives similar  to  those  of  aniline  ;  those  containing  methyl 
and  its  homologues  are  more  basic  than  toluidine  itself. 


DIAMINES   AND   TRIAMINES.  743 

Benzylamine,  C6H5 .  CH2(NH2)  or  NH2(C7H7). — This  compound,  isomeric 
with  toluidine,  is  obtained,  together  with  dibenzylamine,  NH(C7H7)2,  and 
tribenzylamine,  N(C7H7)3,  by  the  action  of  alcoholic  ammonia  on  benzyl 
chloride,  C6H5.  CH2C1  (p.  496),  the  mode  of  formation  of  these  bases  being 
exactly  analogous  to  that  of  methylamine  and  its  homologues,  and  alto- 
gether different  from  that  of  toluidine. 

Benzylamine  is  a  colorless  liquid,  boiling  at  182°-183°  C.  (360°  F.)  (23° 
C.  (73°  F.)  lower  than  toluidine).  It  mixes  in  all  proportions  with  water, 
and  is  separated  therefrom  by  potash.  It  is  a  much  stronger  base  than 
toluidine ;  absorbs  carbon  dioxide  rapidly,  forming  a  crystalline  carbonate ; 
unites  readily  with  other  acids,  producing  rise  of  temperature ;  and  fumes 
with  hydrochloric  acid.  The  hydrochloride  crystallizes  in  striated  tables ; 
the  platinochloride,  2NH3(C7H7)C1 .  PtCl4,  in  orange-colored  laminae. 

Xylidine,  C8HUN  =  C6H3(NH2)  .  (CH8)2,  Cumidine,  C9H13N,  or  probably 
C6H4(NH2)  .  C3H7,  and  Cymidine,  C10H,5N,  or  C,0H,3(NH2),  homologous  with 
toluidine,  are  obtained  in  like  manner  by  reduction  of  the  corresponding 
nitro-derivatives.  Xylidine  boils  at  214°-216°  C.  (417°-420°F.) ;  cumidine 
at  225°  C.  (437°  F. )  ;  cymidine  at  250°  C.  (482°  F.).  Xylidine  and  cumidine 
form  well-crystallized  salts. 

The  isomers  of  these  three  bases,  homologous  with  benzylamine,  have 
not  yet  been  obtained. 

Naphthalidine,  ClpH9N=C,0H7(NH2),  is  interesting,  as  being  one  of  the 
first  compounds  of  its  kind  produced  by  Zinin's  process.  It  is  obtained  by 
the  action  of  ammonium  sulphide  upon  an  alcoholic  solution  of  nitro-naph- 
thalene,  one  of  the  numerous  products  of  the  action  of  nitric  acid  upon 
naphthalene,  C10H8.  When  pure  it  forms  colorless  silky  needles,  fusible,  and 
volatile  without  decomposition.  It  has  a  powerful,  not  disagreeable  odor, 
and  burning  taste,  is  nearly  insoluble  in  water,  but  dissolves  readily  in 
alcohol  and  ether;  the  solution  has  an  alkaline  reaction.  Naphthalidine 
forms  numerous  crystalline  salts. 


DIAMINES  and  TRIAMINES. 

These  are  bases  derived  from  two  or  three  molecules  of  ammonia,  N2H6 
and  N3H9,  by  substitution  of  bivalent  and  trivalent  alcohol-radicals  for  a 
part  or  the  whole  of  the  hydrogen.  A  portion  of  the  hydrogen  may  at  the 
same  time  be  replaced  by  univalent  alcohol-radicals.  Diamines  are  formed 
by  the  action  of  the  chlorides,  bromides,  and  iodides  of  the  diatomic  alco- 
hol-radicals on  ammonia.  The  examination  of  these  compounds  is  far  from 
being  complete. 

ETHENE-DIAMINE  AND  DIETHENE-DIAMINE. — The  action  of  ammonia  upon 
ethene  dibromide  is  very  complex ;  but  among  the  products  of  the  reaction 
there  are  invariably  present  the  hydrobromides  of  two  bases  which  are 
derived  from  two  molecules  of  ammonia,  viz.,  ethene-diamine,  C2H8N2  = 
N?(C2H4)"H4,  an  oily  liquid  boiling  at  117°  C.  (242°  F.),  and  diethene-dia- 
mine,  C4HION2  =•  N2(C2H4)//2H2,  a  crystalline  solid,  boiling  at  a  high  tem- 
perature. The  formation  of  these  bodies,  which  saturate  two  equivalents 
of  acid,  may  be  represented  by  the  following  equations : 

2NH3  +     (C2H4)"Br2  =  [N2(C2H4)"H6]"Br2,  and 

4NH3  +  2(C2H4)"Br2  =  [N,(C,H4)",H4]"Bra   +   2NH4Br. 

Distillation  with  potash  separates  the  bases  from  these  salts,  potassium 
bromide  being  formed  at  the  same  time. 


744  DIAMINES   AND   TEIAMINES. 

By  the  action  of  ethyl  iodide  upon  ethene-diamine  and  diethene-diamine, 
two  series  of  ethylated  derivatives  have  been  obtained.  We  can  here  give 
only  the  names  and  formulae  of  the  iodides : 

Bases  derived  from  Ethene-diamine. 


Iodide  of  Ethene-diammonium    .     .     . 
Iodide  of  Diethyl-ethene-diammonium. 
Iodide  of  Tetrethyl-ethene-diammonium 
Iodide  of  Pentethyl-ethene-diammonium 
Iodide  of  Hexethyl-ethene-diammonium 


NaH6(C2H4)"]"Ir 

N2H4(C2H4)"(C2H5)2]"I2. 
N2H2(C2H4)"(C2H5)4]"I2. 
N2H(C2H4)"(C2H5)5]"I2. 
[N2(C2H4)"(C2H5)6]"I2. 

'Bases  derived  from  Diethene-diamine. 

Iodide  of  Diethene-diammonium  .     .     .     [N2H4(C2H4)"2]"I2. 
Iodide  of  Diethyl-diethene-diammonium     [N2H2(C2H4)//2(C2H5)2]//I2. 
Iodide  of  Triethyl-diethene-diammonium    [N2H(C2H4)"2(C2H6)8]"I2. 
Iodide  of  Tetrethyl-diethene-diammonium  [N2(CN2H4)"2(C2H5)4]"I2. 


DlETHENE-TRIAMINE     AND      TRIETIIENE-TRIAMINE.  —  More     recently    two 

other  bases  have  been  separated  from  the  product  of  the  action  of  ethene 
dibromide  upon  ammonia,  viz.,  diethene  triamine,  (C2H4)2H5N3<  and  tri- 
ethene-triamine,  (C2H4)3H3N3.  The  formation  of  these  bodies,  which  satu- 
rate 3  equivalents  of  acid,  may  be  represented  by  the  following  equations  : 

4NH.  +  2(C2H4)"Br2  =  [N3(C2H4)"2H8]'"Br3  -f     NH4Br 
6NH3  +  3(C2HJ"Br2  =   [Ns(C,H4)"BH6]'"Br8  +  3NH4Br. 

DlPHENYL-ETHENE-DIAMINE,      N2H2(C2H4)  "  (C6H5)2,      and      DlPHENTL-DI- 

ETHENE-DIAMINE,  N2(C2H4)//2(C6H5)2>  —  Aniline,  when  submitted  to  the  ac- 
tion of  ethene  bromide,  C2H4Br2,  solidifies  to  a  crystalline  mass,  from  which 
potash  separates  two  crystalline  bases,  which  are  soluble  in  alcohol  and  in 
ether,  but  insoluble  in  water.  If  a  large  quantity  of  ethene  bromide  be 
made  to  act  upon  a  comparatively  small  quantity  of  aniline,  the  new  salt 
contains  the  hydrobromide  of  diphenyl-ethene-diamine,  or  ethene-dianaline, 
C14Hi6N2  .  2HBr  =  2C6H7N  -f-  C2H4Br2.  On  the  other  hand,  if  the  aniline 
be  employed  in  excess,  hydrobromide  of  diethene-dianiline,  or  diphenyl- 
diethene-diamine,  C]6H18N2  .  2HBr,  is  formed,  together  with  hydrobromide 
of  aniline  :  4C6H7N  +  2C2H4Br2  ==  C16H18N2  .  2HBr  +  2(C6H7N  .  HBr). 

METHENYL-DIPHENYL-DIAMINE,  C13H12N2  =  N2H(CH)///(C6H5)2,  also  called 
Formyl-aniline.  —  A  mixture  of  aniline  and  chloroform  exposed  in  sealed 
tubes  to  a  temperature  of  180°  solidifies  to  a  crystalline  mass,  consisting 
of  aniline  hydrochloride  and  the  hydrochloride  of  methenyl-diphenyl-dia- 
mine: 

4C6H7N  +  CHC13  =  2(C6H7N  .  HC1)  +  C13H12N2  .  HC1. 

By  washing  with  cold  water,  the  aniline  hydrochloride  is  removed,  and  the 
residue,  treated  with  potash,  yields  the  diatomic  base  in  a  state  of  purity. 
It  is  crystalline,  insoluble  in  water,  soluble  in  alcohol  and  in  ether. 


phenylene-diamine  presents  itself  as  a  slightly-colored,  heavy  oil,  which, 
like  phenylamine,  has  a  tendency  to  assume  a  brown  color  on  exposure  to 
the  air.  The  base  gradually  solidifies  into  a  mass  of  crystals,  which  be- 
come hard  and  white  by  washing  with  ether.  The  melting  point  of  pheny- 
lene-diainine  is  63°  C.  (145°  F.),  the  boiling  point  near  280°  C.  (536°  F.) ; 
it  distils  without  alteration.  This  substance  is  very  soluble  in  water  and 


ANILINE    COLORS.  745 

alcohol,  less  soluble  in  ether.  It  combines  with  2  molecules  of  acid,  form- 
ing well  crystallized,  rather  soluble  salts. 

The  distillation  of  dinitrotoluene  and  dinitrocumene  with  acetic  acid  and 
iron  filings  produces  the  corresponding  bases,  toluylene-diamine,  C7H,0N2, 
and  cumylene-diamine,  C8H,2N2,  which  in  their  properties  and  chemical 
deportment  bear  a  great  resemblance  to  phenylene-diamine. 

I  (C6H5)2 
CARBODIPHENYL-TRIAMINE,  OR  MELANILINE,  C,3H,3N3:=:N3^    Civ       . — The 

(.  Hs 

action  of  dry  cyanogen  chloride  upon  anhydrous  aniline  gives  rise  to  the 
formation  of  a  resinous  substance,  which  is  the  hydrochloride  of  melani- 
line.  Dissolved  in  water  and  mixed  with  potash,  the  above  salt  yields  me- 
laniline  in  the  form  of  an  oil,  which  rapidly  solidifies  to  a  beautiful  crys- 
talline mass.  The  following  equation  represents  its  formation :  2C6H7N  -f- 
CNC1  =  C13H14N3C1. 

Melaniline  treated  with  chlorine,  bromine,  iodine,  or  nitric  acid,  yields 
basic  substitution-products,  in  which  invariably  two  atoms  of  hydrogen  are 
replaced.  It  combines  with  two  equivalents  of  cyanogen,  and  forms  salts 
with  acids,  most  of  which  are  crystallizable. 

CARBOTRIPHENYL-TRIAMINE,  OR  PHENYL-MELANILINE,  C,9H17N3  =  N3H2Civ 
(C6H6)3. — Aniline,  when  exposed  to  the  action  of  carbon  tetrachloride  at  a 
temperature  of  150°  C.  (302°  F.),  solidifies  into  a  resinous  mass,  consisting 
of  a  mixture  of  the  hydrochlorides  of  rosaniline  (p.  746),  and  of  several 
other  bases,  from  which,  by  appropriate  treatment,  a  beautiful  basic  com- 
pound may  be  extracted,  constituted  as  above.  The  formation  of  this  body, 
which  in  its  properties  closely  resembles  melaniline,  may  be  represented 
by  the  equation : 

6C6H7N     +     CC14    =    3(C6H7N.HC1)     +     C19H17N3.  HC1. 

Melaniline  is  sometimes  represented  as  cyano-diphenyl-diamine,  N2H3 
(CN)(C6H5)2,  and  phenyl-melaniline  as  cyano-triphenyl-diamine,  N2H2(CN) 
(C6H5)3 ;  but  these  can  scarcely  be  regarded  as  true  formulae  of  diamines, 
inasmuch  as  they  contain  only  monatomic  radicals,  and  may  therefore  be 
resolved  into  formulae  of  monamines. 


Aniline  Colors. 

Aniline  has  during  the  last  few  years  found  an  extensive  application  in 
the  arts,  a  long  series  of  coloring  matters  unequalled  in  brilliancy  and 
beauty  having,  by  the  action  of  different  oxidizing  agents,  been  produced 
from  it.  It  was  Mr.  W.  H.  Perkin  who  had  first  the  happy  idea  of  apply- 
ing practically  the  well-known  property  possessed  by  aniline,  of  forming 
violet  and  blue  solutions  when  treated  with  a  solution  of  chloride  of  lime 
or  chromic  acid.  He  succeeded  in  fixing  these  colors,  and  bringing  them 
into  a  form  adapted  for  the  dyer.  We  will  here  notice  some  of  the  most 
important  of  these  coloring  matters. 

ANILINE-PURPLE,  MAUVE. —  According  to  Mr.  Perkin,  mauve  is  prepared 
by  mixing  solutions  of  aniline  sulphate  and  potassium  bichromate  in  equi- 
valent proportions,  and  allowing  the  mixture  to  stand  for  several  hours; 
the  black  precipitate  formed  is  filtered  off  and  purified  from  admixed  po- 
tassium sulphate  by  washing  with  water;  it  is  then  dried  and  freed  from 
resinous  matter  by  repeated  digestion  with  coal-tar  naphtha,  and  finally 
dissolved  in  boiling  alcohol.  For  its  further  purification,  the  alcoholic 
solution  is  evaporated  to  dryness,  the  substance  is  dissolved  in  a  large 
63 


746  ANILINE    COLORS. 

quantity  of  boiling  water,  reprecipitated  with  caustic  soda,  washed  with 
water,  and  dissolved  in  alcohol;  and  the  filtered  solution  is  evaporated  to 
dryness.  Mauve  thus  prepared  forms  a  brittle  substance,  having  a  beau- 
tiful bronze-colored  surface :  it  is  difficultly  soluble  in  cold  water,  although 
it  imparts  a  deep  purple  color  to  that  liquid:  it  is  more  soluble  in  hot 
water,  very  soluble  in  alcohol,  nearly  insoluble  in  ether  and  hydrocar- 
bons :  it  dissolves  in  concentrated  acetic  acid,  from  which  it  crystallizes. 
Mauve  is  the  sulphate  of  a  base  called  mauveine,  having  the  composition 
C27H24N4,  and  capable  of  forming  numerous  crystalline  salts  with  acids. 

ANILINE-RED,  ROSANILINE,  C^HjgNg. —  This  substance  occurs  more  or  less 
pure  in  commerce  under  the  names  roseine,  fuchsine,  magenta,  azaleine,  &c. 
A  red  color  had  been  observed  at  different  times  in  experimenting  with 
aniline,  more  especially  when  that  substance  was  digested  with  Dutch 
liquid.  The  red  coloring  matter,  though  still  impure,  was  first  obtained  in 
a  separate  state  from  the  product  formed  by  digesting  aniline  with  carbon 
tetrachloride  at  150°,  in  which  reaction  it  is  formed,  together  with  carbo- 
triphenyltriamine.  It  was  M.  Verguin  who  first  prepared  it  upon  a  large 
scale  by  the  action  of  stannic  chloride  upon  aniline.  Since  that  time  it  has 
been  produced  by  the  action  of  mercuric  salts,  arsenic  acid,  and  many 
other  oxidizing  agents,  upon  aniline.  The  most  advantageous  mode  of  pre- 
paration is  the  following:  A  mixture  of  12  parts  of  the  dry  arsenic  acid 
which  occurs  in  commerce,  and  10  parts  of  aniline,  is  heated  to  120°  or 
140°  C.  (250°-280°  F.),  for  about  six  hours:  a  little  water  may  be  added 
with  advantage.  The  product,  which  is  a  hard  mass  possessing  the  lustre 
of  bronze,  is  dissolved  in  hot  water  and  precipitated  by  a  slight  excess  of 
soda:  the  precipitate  when  washed  with  water,  and  dissolved  in  acetic 
acid,  forms  the  roseine  of  commerce.  In  order  to  purify  this  still  crude 
substance,  it  is  boiled  with  an  excess  of  soda,  to  separate  any  aniline  that 
it  may  contain ;  and  the  washed  precipitate  is  dissolved  in  very  dilute 
mineral  acid,  filtered  from  undissolved  tarry  matter,  and  re-precipitated  with 
alkali.  The  compounds  of  rosaniline  with  one  molecule  of  acid  are  beau- 
tifully crystallized  substances,  which  in  the  dry  state  possess  a  green  color 
with  golden  lustre;  with  water  they  furnish  a  very  intensely  colored  red 
solution.  The  free  base,  first  obtained  by  Mr.  Nicholson,  presents  itself 
in  colorless  crystalline  plates,  insoluble  in  water,  soluble  in  alcohol  and 
ether,  with  a  red  color,  which  it  also  acquires  on  exposure  to  the  air.  Ros- 
aniline in  the  anhydrous  state  is  represented  by  the  formula  C^H^Ng, 
and  in  the  hydrated  state,  such  as  it  assumes  when  isolated  from  its  com- 
pounds, by  the  formula  C20H,9N3 .  H20.  It  is  a  triamine  capable  of  com- 
bining with  one,  two,  or  three  equivalents  of  acid.  The  aniline  reds  of 
commerce  are  saline  compounds,  more  or  less  pure,  of  rosaniline  with  one 
equivalent  of  acid.  The  acetate,  which  is  chiefly  found  in  commerce  in 
England,  has  been  prepared  by  Mr.  Nicholson  in  splendid  crystals  of  very 
considerable  dimensions,  having  the  composition  C^H^Ng .  C2H402.  In 
France,  the  chloride  is  chiefly  employed ;  its  formula  is  C^H^Ng .  HC1.  The 
action  of  ammonium  sulphide  upon  rosaniline  gives  rise  to  leucaniline,  C.^ 
H2,N3,  a  base  containing  two  additional  atoms  of  hydrogen.  This  base  is 
itself  colorless,  and  forms  colorless  salts  containing  3  equivalents  of  acid, 
such  as  Cj0H8|Ng  .  HC1.  Oxidizing  agents  reproduce  rosaniline. 

The  molecular  constitution  of  rosaniline  has  not  been  distinctly  made 
out.  Neither  is  its  mode  of  formation  thoroughly  understood  ;  but  one 
very  important  fact  has  been  brought  to  light  by  the  researches  of  Hof- 
mann,  and  confirmed  by  the  experience  of  manufacturers  —  namely,  that 
pure  aniline,  from  whatever  source  it  may  be  obtained,  is  incapable  of  fur- 
nishing aniline-red.  Commercial  aniline  prepared  from  coal-tar  always  in 
fact  contains  toluidine  as  well  as  aniline  ;  and  Hofmann  has  shown  that  the 


APPENDIX    TO    THE   ALCOHOLIC   AMMONIAS.         747 

presence  of  this  base,  together  with  aniline,  is  essential  to  the  formation 
of  the  red  dye.  Toluidine  by  itself  is  just  as  incapable  of  yielding  the 
red  as  pure  aniline,  but  when  a  mixture  of  pure  aniline  and  pure  toluidine 
is  treated  with  stannic  or  mercuric  chloride,  or  with  arsenic  acid,  the  red 
coloring  matter  is  immediately  produced.  Its  formation  may  perhaps  be 
represented  by  the  equation: 

C6H7N        -f        2C7H,N        =        C^H,^        +        3H2 
Aniline.  Toluidine.  Rosaniline. 

Rosaniline  is  doubtless  a  triamine,  and  the  formula  N3(C7H6)//2.  (C6H4)"H8 
has  been  suggested  as  the  rational  expression  of  its  constitution.  This, 
however,  is  not  the  formula  of  a  true  triamine,  since  it  contains  only  biva- 
lent radicals,  and  may  be  resolved  into  NH3  -f  N2(C7H6)//2(C6H4)//,  or 
N(C6H4)"H  +  N2(C7H6)"2H2. 

ANILINE-BLUE  and  ANILINE-VIOLET. — MM.  Girard  and  De  Laire  obtained 
aniline-blue  by  digesting  rosaniline  with  an  excess  of  aniline  at  150°— 160° 
C.  (300°-320°  F.).  Together  with  aniline-blue,  which  is  the  principal  pro- 
duct of  the  reaction,  several  other  coloring  matters  (violet  and  green)  and 
indifferent  substances  are  formed,  considerable  quantities  of  ammonia  being 
invariably  evolved.  The  crude  blue  is  purified  by  treating  it  successively 
with  boiling  water  acidified  with  hydrochloric  acid,  and  with  pure  water. 
The  blue  coloring  matter  is  said  to  be  obtained  from  its  boiling  alcoholic 
solution  in  brilliant  needles.  It  consists  of  the  hydrochloride  of  triphenyl- 
rosaniline,  C20H,6(C6H5)3N3.  By  heating  rosaniline  with  ethyl-iodide,  Dr. 
Hofmann*  has  obtained  an  aniline-violet,  having  the  composition  of  hydri- 
odide  of  triethyl-rosaniline,  C20H,6(C2H5)3N3.  Another  aniline-violet  is  pro- 
duced by  heating  rosaniline  with  a  quantity  of  aniline  less  than  sufficient 
to  form  aniline-blue. 

ANILINE-YELLOW,  CHRYSANILINE. — In  the  preparation  of  aniline-red,  a 
considerable  quantity  of  secondary  products  is  produced,  from  which  Mr. 
Nicholson  has  succeeded  in  extracting  a  yellow  coloring  matter.  This  sub- 
stance, which  has  been  called  chrt/saniline,  contains  C20H17N3 :  it  is  also  a 
well-defined  base,  forming  two  series  of  salts,  the  majority  of  them  being 
very  well  crystallized.  The  two  hydrochlorides  of  chrysaniline  are  C^H^ 
N3.HC1,  and  C.^H^N,, .  2HC1.  The  nitrate  of  chrysaniline  is  so  insoluble 
in  water,  that  nitric  acid  may  be  precipitated  even  from  a  dilute  solution 
of  nitrates  by  means  of  the  more  soluble  hydrochlorate  or  acetate  of 
chrysaniline.  Chrysaniline  is  intimately  related  to  rosaniline  and  leucani- 
line,  differing  from  the  former  by  2  and  from  the  latter  by  4  atoms  of  hy- 
drogen: 

Chrysaniline     .         .         .     C^H^N,, 

Rosaniline        .         .         .     C20H,9N3 

Leucaniline      .        .         .     CHN. 


APPENDIX  TO  THE  ALCOHOLIC  AMMONIAS. 

Under  this  head  we  shall  include  certain  artificial  organic  bases,  the 
molecular  constitution  of  which  has  not  been  very  distinctly  made  out; 
also  the  natural  bases  or  alkaloids  found  in  living  organisms;  the  phos- 
phorus, arsenic,  and  antimony  bases,  analogous  in  composition  to  the 
amines ;  and  certain  other  compounds  of  organic  radicals  with  metals. 

*  Proceedings  of  the  Royal  Society,  xiii.  13. 


748  ARTIFICIAL    ORGANIC   BASES. 

I.  — Artificial  Organic  Bases  obtained  from  various  Sources. 

BASES  OBTAINED  BY  DESTRUCTIVE   DISTILLATION. 

The  destructive  distillation  of  organic  substances  has  furnished  a  rich 
harvest  of  basic  compounds.  A  few  of  the  more  interesting  may  here  be 
noticed. 

CHINOLINE  (LEUCOLINE),  C9H7N. —Quinine,  cinchonine,  strychnine,  and 
probably  other  bodies  of  this  class,  when  distilled  with  a  very  concentrated 
solution  of  potash,  yield  an  oily  product  resembling  aniline  in  many  re- 
spects, and  possessing  strong  basic  powers :  it  is,  however,  less  volatile 
than  that  substance,  and  boils  at  235°  C.  (455°  F.).  When  pure,  it  is  color- 
less, and  has  a  faint  odor  of  bitter  almonds.  Its  density  is  1-081.  It  is 
slightly  soluble  in  water,  and  miscible  in  all  proportions  with  alcohol,  ether, 
and  essential  oils.  Chinoline  forms  salts  with  acids,  which,  generally 
speaking,  do  not  crystallize  very  freely.  Chinoline  is  a  tertiary  monamine. 
When  digested  with  ethyl  iodide,  it  yields  iodide  of  ethylchinoline,  CnH,2NI 
=  C  H  (C2H5)NI.  Treatment  of  this  iodide  with  silver  oxide  liberates  the 
base9CnH,2N(HO),  which  exhibits  all  the  characters  of  the  .ammonium  bases, 
being  powerfully  alkaline,  easily  soluble  in  water,  and  not  volatile.  Mr. 
C.  Greville  Williams  has  shown  that  the  basic  oil  obtained  by  distilling  cin- 
chonine contains,  in  addition  to  chinoline,  two  other  bases  of  very  similar 
properties,  to  which  the  names  of  lepidine  and  cryptidine  have  been  given. 
Lepidine  contains  C10H9N,  cryptidine  CUHUN. 

CHINOLINE-BLUE,  CYANINE.  —  The  action  of  amyl  iodide  upon  chinoline 
gives  rise  to  iodide  of  amylchinoline,  CJ4H18NI.  Addition  of  an  excess  of 
soda  to  an  aqueous  solution  of  this  iodide  produces  a  black  resinous  pre- 
cipitate, which  dissolves  in  alcohol  with  a  magnificent  blue  color.  This 
precipitate  is  the  iodide  of  a  new  base,  discovered  by  Mr.  C.  G.  Williams, 
which  has  been  called  cyanine.  The  color  of  this  body  is  unfortunately 
very  fugitive.  According  to  recent  researches,*  the  formation  of  the  new 
iodide  is  represented  by  the  following  equation :  2Ci4H18NI  =  C28H35N2I 
+  HI. 

PICOLINE,  C6H7N.  —  Dr.  Anderson  has  described  under  this  name  a  vol- 
atile, oily  base,  which  is  present  in  certain  varieties  of  coal-tar  naphtha, 
being  there  associated  with  aniline,  chinoline,  and  several  other  volatile 
substances  but  imperfectly  understood.  It  is  separated  without  difficulty 
from  the  two  bases  just  mentioned,  by  distillation,  in  virtue  of  its  superior 
volatility.  Picoline,  when  pure,  is  a  colorless,  transparent,  limpid  liquid, 
of  powerful  and  persistent  odor,  and  acrid,  bitter  taste.  It  is  unaffected 
by  a  cold  of — 18°.  It  is  extremely  volatile,  evaporates  rapidly  in  the  air, 
and  does  not  become  brown  like  aniline  when  kept  in  an  ill-stopped  bottle. 
Picoline  has  a  sp.  gr.  of  0-955,  and  boils  at  133°  C.  (271°  F.).  It  mixes  in 
all  proportions  with  pure  water,  but  is  insoluble  in  caustic  potash  and 
most  saline  solutions.  The  alkalinity  of  this  substance  is  exceedingly  well 
marked:  it  restores  the  blue  color  of  reddened  litmus,  and  forms  a  series 
of  crystallizable  salts.  It  is  isomeric  with  aniline,  but  completely  dis- 
tinguished from  that  body  by  numerous  characteristic  reactions. 


BASES  FROM  ANIMAL  OIL. 

The  oily  liquid  obtained  by  the  distillation  of  bones  and  animal  matter 
generally,  frequently  designated  by  the  term  Dippel's  Oil,  contains  several 
*  Hofmann,  Compt.  Rend.  Iv.  849. 


BASES    FROM    ANIMAL    OIL.  749 

volatile  organic  bases.  Together  with  some  of  the  substances  already  de- 
scribed, such  as  methylamine,  ethylamine,  picoline,  aud  aniline,  Dr.  Ander- 
son has  found  in  it  several  peculiar  bases. 

PETININK,  C4HUN. — The  properties  of  this  substance  are  very  analogous 
to  those  of  biethylamine  and  triethylamine.  It  has  the  same  composition 
as  biethylamine,  but  differs  from  it  by  its  higher  boiling-point,  which  is 
79-5°  C.  (175°  F.),  that  of  biethylamine  being  57-5°  C.  (135°  P.)  (p.  736). 
Some  chemists  are  inclined  to  explain  this  difference  by  assuming  that 
petinine  is  identical  with  butylamine,  NH2(C4H9).  This  assumption  may  be 
correct,  but  is  not  as  yet  supported  by  any  experimental  evidence.  The 
true  butylamine  has  been  obtained  by  M.  Wurtz  from  butyl-alcohol  in  the 
same  manner  as  ethylamine  is  obtained  from  common  alcohol. 

PYRIDINE,  C5H5N,  much  resembles  picoline,  and  is  obtained  by  repeatedly 
rectifying  the  bases  of  Dippel's  oil,  which  distil  at  115°  C.  (239°  F.). 

LUTIDINE,  C7H9N.  —  Oily  base  contained  in  the  portion  which  distils  at 
154°  C.  (309°  F.). 

COLLIDINE,  C8HUN. — Oily  base  very  similar  to  the  preceding  ones.  Boil- 
ing point  179°  C.  (354°  F.). 

To  the  same  series  also  belongs  an  oily  base,  lately  isolated  by  Mr.  C. 
Greville  Williams  from  the  basic  products  of  the  distillation  of  Dorsetshire 
shale,  and  described  by  him  under  the  name  of  parvoline.  Parvoline  is 
said  to  contain  C9H13N. 

It  will  be  observed  that  these  bases,  the  constituent  radicals  of  which 
are  not  yet  clearly  made  out,  are  isomeric  with  the  homologues  of  aniline : 

?  .  C5H5N  .  Pyridine. 

Aniline  .  C6H7N  .  Picoline. 

Toluidine  .  C7H9N  .  Lutidine. 

Xylidine  .  C8H,,N  .  Colliding 

Cumidine  .  C9H,3N  .  Parvoline. 

Cymidine  .  010H15N. 

The  first  term  of  the  aniline  series,  and  the  last  of  the  pyridine  series, 
are  unknown.  The  bases  of  the  aniline  series  are  primary,  those  of  the 
pyridine  series  tertiary  monamines. 

PYRROL,  C4H5N. — This  substance  was  first  observed  by  Runge  in  coal- 
tar;  Anderson  afterward  obtained  it  from  animal  oil.  It  has  the  proper- 
ties of  a  very  weak  base,  the  compounds  of  which  with  acids  are  destroyed 
by  boiling  with  water.  To  prepare  pyrrol,  the  bases  of  animal  oil  are  dis- 
solved in  sulphuric  acid;  the  solution,  when  submitted  to  protracted  ebulli- 
tion, retains  the  stronger  bases,  allowing  the  pyrrol  to  pass  over.  The 
distillate  is  heated  with  solid  potassium  hydrate,  when  the  pyrrol  combines 
slowly  with  the  alkali,  admixed  impurities  being  volatilized.  By  dissolving 
the  potassium-compound  in  water,  the  pyrrol  separates  as  an  oily  liquid, 
floating  on  the  surface  of  the  solution.  Pyrrol  is  colorless,  insoluble  in 
water  and  alkalies,  slowly  soluble  in  acids :  it  has  an  ethereal  odor  resem- 
bling that  of  chloroform,  a  specific  gravity  =  1-077,  and  boils  at  133°  C. 
(271°  F.).  Pyrrol  is  easily  recognized  by  the  purple  color  which  it  imparts 
to  fir-wood  moistened  with  hydrochloric  acid. 

By  heating  an  acid  solution  of  pyrrol,  a  red,  flaky  substance,  pyrrol-red, 
is  produced,  containing  Ci2HuN202,  the  formation  of  which  is  represented 
by  the  following  equation: 

3C4H6N        +        H20        =        C12HUN20        +        NII3. 
63* 


750  ARTIFICIAL    ORGANIC   BASES. 

BASES  OBTAINED  BY  THE  ACTION  OF  AMMONIA  UPON  ALDEHYDES. 
The  bodies  called  hydramides,  produced  by  the  action  of  ammonia  on  fur- 
furol  (p.  695),  and  on  the  aldehydes  of  the  aromatic  series,  are  neutral 
substances,  not  capable  of  uniting  with  acids ;  but,  when  boiled  with  aque- 
ous potash,  they  are  converted,  without  addition  or  abstraction  of  any  ele- 
ments whatever,  into  isomeric  compounds,  which  are  strong  bases,  com- 
bining readily  with  acids  and  forming  definite  salts. 

FURFURINE,  C15H,2N203,*  is  formed  in  the  manner  just  described  from 
furfuramide,  a  hydramide  obtained  by  the  action  of  ammonia  on  furfurol 
(p.  695).  It  is  a  powerful  organic  base,  forming  with  acids  a  series  of 
beautiful  crystallizable  salts,  decomposing  at  a  boiling  heat  the  saline 
compounds  of  ammonia.  Furfurine  is  very  sparingly  soluble  in  cold  water, 
but  dissolves  in  about  135  parts  at  about  100°.  Alcohol  and  ether  dissolve 
it  freely:  the  solutions  have  a  strong  alkaline  reaction.  It  melts  below 
the  boiling  point  of  water,  and,  when  strongly  heated,  inflames  and  burns 
with  a  red  and  smoky  light,  leaving  but  little  charcoal.  Its  salts  are  in- 
tensely bitter. 

AMARINE  (BENZOLINE),  C21H18N2.  —  Hydrobenzamide,  produced  by  the 
action  of  ammonia  on  pure  bitter-almond  oil  (p.  690),  when  long  boiled 
with  a  solution  of  caustic  potash,  suffers  the  same  kind  of  change  as  fur- 
furamide, becoming  entirely  converted  into  the  isomeric  base  called  ama- 
rine.  Precipitated  by  ammonia  from  a  cold  solution  of  the  hydrochloride 
or  sulphate,  amarine  separates  in  white  curdy  masses,  which  when  washed 
and  dried  become  greatly  reduced  in  volume.  In  this  state  it  becomes 
strongly  electric  by  friction  with  a  spatula.  It  is  insoluble  in  water,  but 
dissolves  abundantly  in  alcohol :  the  solution  is  highly  alkaline  to  test- 
paper,  and  if  sufficiently  concentrated,  deposits  the  amarine  on  standing  in 
small,  colorless,  prismatic  crystals.  Below  100°  it  melts,  and  on  cooling 
assumes  a  glassy  or  resinous  condition.  Strongly  heated  in  a  retort,  it  de- 
composes, with  production  of  ammonia,  a  volatile  oil  not  yet  examined, 
and  a  new  body,  pyrobenzoline  or  lophine,  C2,H16N2  (?),  which  appears  to  be 
a  feebly  basic  substance,  insoluble  in  water,  soluble  in  boiling  alcohol.  It 
is  fusible  by  moderate  heat,  and  on  cooling  becomes  a  mass  of  colorless 
radiating  needles  or  plates.  The  salts  of  amarine  are  mostly  sparingly 
soluble ;  the  sulphate,  nitrate,  and  hydrochloride  are  crystallizable  and 
very  definite. 

THIALDINE,  C6H,3NS2.  —  This  base  is  obtained  by  dissolving  the  crystal- 
line compound  of  aldehyde  with  ammonia  (p.  687)  in  from  12  to  16  parts 
of  water,  mixing  the  solution  with  a  few  drops  of  caustic  ammonia,  and 
then  subjecting  the  whole  to  a  feeble  stream  of  sulphuretted  hydrogen. 
After  a  time  the  liquid  becomes  turbid,  and  deposits  thialdine  as  a  white 
crystalline  substance.  It  is  separated,  washed,  dissolved  in  ether,  and  the 
solution  mixed  with  alcohol  and  left  to  evaporate  spontaneously,  by  which 
means  the  base  is  obtained  in  large,  regular,  rhombic  crystals,  having  the 
form  of  gypsum.  The  crystals  are  heavier  than  water,  transparent  and 
colorless.  They  refract  light  strongly.  Thialdine  has  a  somewhat  aro- 
matic odor,  melts  at  43-3°,  and  volatilizes  slowly  at  common  temperatures. 
It  distils  unchanged  with  the  vapor  of  water,  but  decomposes  when  heated 
alone.  It  is  very  sparingly  soluble  in  water,  easily  in  alcohol  and  ether. 
It  has  no  action  on  vegetable  colors,  but  dissolves  freely  in  acids,  forming 
crystallizable  salts.  Heated  with  slaked  lime,  it  is  said'to  yield  chinoline. 

A  very  similar  compound  containing  selenium  has  been  prepared. 

*  This  remarkable  substance,  the  nearest  approach  to  the  native  alkaloids  yet  made,  was 
discovered  by  the  author  of  this  manual.  —  EDS. 


NATURAL    ORGANIC   BASES,  751 

ALALINE,  C3H7N02,  produced  by  treating  acetic  aldehyde  with  hydro- 
cyanic and  hydrochloric  acids,  and  leucme,  C6H13N02,  obtained,  in  like 
manner,  from  valeric  aldehyde,  are  likewise  bases,  forming  definite  salts 
with  acids;  but  they  are  also  acids,  capable  of  forming  salts  by  exchanging 
their  hydrogen  for  metals  ;  they  have  indeed  the  composition  of  amido- 
propionic  and  amidocaproic  acids,  and  as  such  have  been  already  de- 
scribed (pp.  615,  619).  Glycocine.,  C2H5N02  (p.  614),  is  another  body  of  the 
same  series,  and  possessing  similar  properties. 


II.  —  Natural  Organic  Bases,  or  Alkaloids. 

The  organic  alkaloids  constitute  a  remarkable  and  most  interesting  group 
of  bodies:  they  are  met  with  in  various  plants,  some  of  them  also  in  the 
animal  organism.  They  are,  for  the  most  part,  sparingly  soluble  in  water, 
but  dissolve  in  hot  alcohol,  from  which  they  often  crystallize  in  a  very 
beautiful  manner  on  cooling.  Several  of  them,  however,  are  oily,  volatile 
liquids.  The  taste  of  the  vegeto-alkalies,  when  in  solution,  is  usually  in- 
tensely bitter,  and  their  action  upon  the  animal  economy  exceedingly  ener- 
getic. They  all  contain  a  considerable  quantity  of  nitrogen,  and  are  very 
complicated  in  constitution,  having  high  combining  numbers.  This  class 
of  bodies  is  very  numerous ;  but  the  limits  of  this  elementary  work  permit 
us  to  study  only  the  more  important  members  included  in  it. 

None  of  the  organic  bases  occurring  in  plants  have  yet  been  formed  by 
artificial  means  ;  and  their  constitution  is  far  from  being  completely  under- 
stood. There  can  be  no  doubt,  however,  that  the  natural  alkaloids,  like 
the  artificial  bases,  are  substitution-products  of  ammonia.  Many  of  them, 
when  submitted  to  the  action  of  methyl  or  ethyl  iodide,  are  capable  of  ab- 
sorbing a  smaller  or  greater  number  of  equivalents  of  methyl  and  ethyl, 
and  their  deportment  with  these  alcohol-iodides  permits  us  to  ascertain 
with  great  precision  their  degree  of  substitution.  If  a  natural  alkaloid, 
when  submitted  to  the  action  of  ethyl  iodide,  be  found  to  require  for  con- 
version into  a  base  of  the  formula, 

(  A  ) 

Me  [OH' 

U-l 

either  1,  or  2,  or  3  equivalents  of  ethyl,  we  may  infer  that  the  alkaloid  in 
question  belongs  to  the  class  of  bases  represented  by  the  formulae : 

fA  fA  fA 

N  \  B  or  N 1  B  or  N  \  H 

lc  U  U  . 

i.  e.,  that  it  is  a  tertiary,  a  secondary,  or  a  primary  monamine.  All  natu- 
ral alkaloids  which  have  been  examined,  with  the  exception  of  conine,  are 
tertiary  bases. 

Morphine,  or  Morphia,  C17H,9N03. — This  is  the  chief  active  principle 
of  opium :  it  is  the  most  characteristic  body  of  the  group,  and  the  earliest 
known,  dating  back  to  the  year  1804,  when  it  was  discovered  by  Sertiirner. 

Opium,  the  inspissated  juice  of  the  poppy-capsule,  is  a  very  complicated 
substance,  containing,  besides  morphine,  a  host  of  other  alkaloids  in  very 
variable  quantities,  combined  with  sulphuric  acid  and  meconic  acid  (p.  670). 
In  addition  to  these,  there  are  gummy,  resinous,  and  coloring  matters, 
caoutchouc,  &c.,  besides  mechanical  impurities,  as  chopped  leaves.  The 


752  NATURAL    ORGANIC   BASES. 

opium  of  Turkey  is  the  most  valuable,  and  contains  the  largest  quantity  of 
morphine :  the  opiums  of  Egypt  and  of  India  are  considerably  inferior. 
Opium  has  been  produced  in  England  of  the  finest  quality,  but  at  great  cost. 

If  ammonia  be  added  to  a  clear,  aqueous  infusion  of  opium,  a  very  abun- 
dant buff-colored  or  brownish-white  precipitate  falls,  which  consists  prin- 
cipally of  morphine  and  narcotine,  rendered  insoluble  by  the  withdrawal 
of  the  acid,  The  product  is  too  impure,  however,  for  use.  The  chief  dif- 
ficulty in  the  preparation  of  these  substances  is  to  get  rid  of  the  coloring 
matter,  which  adheres  with  great  obstinacy,  redissolving  with  the  precipi- 
tates, and  being  again  in  part  thrown  down  when  the  solutions  are  satu- 
rated with  an  alkali.  The  following  method,  which  succeeds  well  upon  a 
small  scale,  will  serve  to  give  the  student  some  idea  of  a  process  very  com- 
monly pursued  when  it  is  desired  to  isolate  at  once  an  insoluble  organic 
base,  and  the  acid  with  which  it  is  in  combination:  A  filtered  solution  of 
opium  in  tepid  water  is  mixed  with  lead  acetate  in  excess;  the  precipitated 
lead  meconate  is  separated  by  a  filter,  and  through  the  solution  containing 
morphine  acetate,  now  freed  to  a  considerable  extent  from  color,  a  stream 
of  sulphuretted  hydrogen  is  passed.  The  filtered  and  nearly  colorless 
liquid,  from  which  the  lead  has  been  thus  removed,  may  be  warmed  to  ex- 
pel the  excess  of  gas,  once  more  filtered,  and  then  mixed  with  a  slight 
excess  of  caustic  ammonia,  which  throws  down  the  morphine  and  narco- 
tine :  these  may  be  separated  by  boiling  ether,  in  which  the  latter  is  solu- 
ble. The  lead  meconate,  well  washed,  suspended  in  water,  and  decomposed 
by  sulphuretted  hydrogen,  yields  a  solution  of  meconic  acid. 

Morphine  and  its  salts  are  advantageously  prepared,  on  the  large  scale, 
by  the  process  of  Dr.  Gregory.  A  strong  infusion  of  opium  is  mixed  with 
a  solution  of  calcium  chloride,  free  from  iron;  calcium  meconate,  which  is 
nearly  insoluble,  then  separates,  while  the  hydrochloric  acid  is  transferred 
to  the  alkaloids.  By  duly  concentrating  the  filtered  solution,  the  hydro- 
chloride  of  morphine  may  be  made  to  crystallize,  while  the  narcotine  and 
other  bodies  are  left  behind.  Repeated  recrystallization,  and  the  use  of 
animal  charcoal,  then  suffice  to  whiten  and  purify  the  salt,  from  which  the 
base  may  be  precipitated  in  the  pure  state  by  ammonia.  Other  processes 
have  been  proposed,  as  that  of  M.  Thiboumery,  which  consists  in  adding 
slaked  lime  in  excess  to  an  infusion  of  opium,  by  which  the  meconic  acid  is 
rendered  insoluble,  while  the  morphine  is  taken  up  with  ease  by  the  alka- 
line earth.  By  exactly  neutralizing  the  filtered  solution  with  hydrochloric 
acid,  the  morphine  is  precipitated,  but  in  a  somewhat  colored  state. 

Morphine,  when  crystallized  from  alcohol,  forms  small  but  very  brilliant 
prismatic  crystals,  which  are  transparent  and  colorless,  It  requires  at 
least  1QOO  parts  of  water  for  solution,  tastes  slightly  bitter,  and  has  an 
alkaline  reaction.  These  effects  are  much  more  evident  in  the  alcoholic 
solution.  It  dissolves  in  about  30  parts  of  boiling  alcohol,  and  with  great 
facility  in  dilute  acids ;  it  is  also  dissolved  by  excess  of  caustic  potash  or 
soda,  but  scarcely  by  excess  of  ammonia.  When  heated  in  the  air,  mor- 
phine melts,  inflames  like  a  resin,  and  leaves  a  small  quantity  of  charcoal, 
which  easily  burns  away. 

Morphine  in  powder  strikes  a  deep-bluish  color  with  neutral  ferric  salts, 
decomposes  iodic  acid  with  liberation  of  iodine,  and  forms  a  deep-yellow 
or  red  compound  with  nitric  acid  :  these  reactions  are  by  some  considered 
characteristic. 


Crystallized  morphine  contains  C17H,9N03.  H20. 
The  most  characteristic  and  best-defined  salt 


salt  of  this  base  is  the  hydro- 
chloride.  It  crystallizes  in  slender,  colorless  needles,  arranged  in  tufts  or 
stellated  groups,  soluble  in  about  20  parts  of  cold  water,  and  in  its  own 
weight  at  the  boiling  heat.  The  crystals  contain  3  molecules  of  water. 
The  sulphate,  nitrate,  and  phosphate  are  crystallizable  salts:  the  acetate  crys- 


NARCOTINE —  CODEINE.  753 

tallizes  with  great  difficulty,  and  is  usually  sold  in  the  state  of  a  dry  pow- 
der. The  artificial  meconate  is  sometimes  prepared  for  medicinal  use. 

An  alcoholic  solution  of  morphine,  heated  in  sealed  tubes  with  methyl 
iodide,  forms  a  crystalline  compound,  C,8H22N03l  =  C,7(H,9CH3)N03T;  this 
substance  yields,  with  silver  oxide,  a  very  alkaline  solution,  obviously  con- 
taining an  ammonium  base.  Morphine  is  therefore  a  tertiary  amine,  the 
group  C17H1903  representing  one  or  several  radicals,  which  are  together 
capable  of  replacing  3  atoms  of  hydrogen. 

Narcotine. — The  marc,  or  insoluble  portion  of  opium,  contains  much 
narcotine,  which  maybe  extracted  by  boiling  with  dilute  acetic  acid.  From 
the  filtered  solution  the  narcotine  is  precipitated  by  ammonia,  and  after- 
wards purified  by  solution  in  boiling  alcohol,  and  filtration  through  animal 
charcoal.  Narcotine  crystallizes  in  small,  colorless,  brilliant  prisms,  which 
are  nearly  insoluble  in  water.  The  basic  powers  of  narcotine  are  very 
feeble :  it  is  destitute  of  alkaline  reaction,  and  although  freely  soluble  in 
acids,  refuses,  for  the  most  part,  to  form  with  them  crystallizable  com- 
pounds. 

According  to  Matthiessen  and  Foster,  narcotine  contains  C^H^NOj. 

Narcotine  yields  some  curious  products  by  the  action  of  oxidizing  agents, 
as  a  mixture  of  dilute  sulphuric  acid  and  manganese  dioxide,  or  a  hot  solu- 
tion of  platinic  chloride.  They  have  been  chiefly  studied  by  Wohler,  Blyth, 
Anderson,  and  lately  also  by  Matthiessen  and  Foster.  The  most  important 
of  these  is  opianic  acid,  a  substance  forming  colorless,  prismatic,  reticulated 
crystals,  sparingly  soluble  in  cold,  easily  in  hot  water.  It  melts  when 
heated,  but  does  not  sublime.  After  fusion  it  becomes  quite  insoluble  in 
dilute  alkalies,  but  without  change  of  composition.  This  acid  forms  crys- 
tallizable salts  and  an  ether:  it  contains  C,0H]006.  The  ammonia-salt,  by 
evaporation  to  dryness,  yields  a  nearly  white  insoluble  powder,  called 
opiammone,  containing  C^H^NOg,  convertible  by  strong  acids  into  opianic 
acid  and  ammonia.  Sulphurous  acid  yields  with  opianic  acid  two  products 
containing  sulphur.  A  basic  substance,  cotarnine,  C^II^NOg,  is  contained 
in  the  mother-liquor  from  which  opianic  acid  has  crystallized :  it  forms  a 
yellow  crystalline  mass,  very  soluble,  of  bitter  taste,  and  feebly  alkaline 
reaction.  Its  hydrochloride  is  a  well-defined  salt.  The  transformation  of 
narcotine  into  opianic  acid  and  cotarnine  is  represented  by  the  equation: 

CnHBN07        +        0        =        C10H1005        +        C12H13N03. 

Another  basic  substance,  narcogenine,  was  accidentally  produced  in  an  at- 
tempt to  prepare  cotarnine  with  platinic  chloride.  It  formed  long  orange- 
colored  needles,  and  contained  C18H,9N05. 

By  heating  opianic  acid  with  a  strong  solution  of  potash,  it  is  converted 
into  a  crystallizable  neutral  and  volatile  substance  called  meconin,  C,0H1004, 
and  a  bibasic  crystallizable  acid,  termed  hemipinic  acid,  C,0H1006: 

2C10H1006        =         C10H1004        +        C10H1006. 

Hemipinic  acid,  treated  with  hydriodic  acid,  splits  up  into  methyl  iodide, 
carbonic  acid,  and  hypogallic,  C7H604,  the  relation  of  which  to  gallic  acid 
has  already  been  mentioned  (p.  607).  When  cotarnine  is  gently  heated 
with  very  dilute  nitric  acid,  it  is  converted  into  methylamine  nitrate  and  co- 
tarnic  acid,  a  bibasic  acid  containing  CUH,206: 

C12H13N03  +  2H20  +  N03H  =  CH6N.N03  +  CUIIH08. 

Codeine,  C,8H21N03.  —  Hydrochloride  of  morphine,  prepared  directly 
from  opium,  as  in  Gregory's  process,  contains  codeine-salt.  On  dissolving 
it  in  water,  and  adding  a  slight  excess  of  ammonia,  the  morphine  is  preci- 
pitated, and  the  codeine  left  in  solution.  Pure  codeine  crystallizes,  by 


754  NATURAL    ORGANIC   BASES. 

spontaneous  evaporation,  in  colorless  transparent  octohedrons:  it  is  soluble 
in  80  parts  of  cold,  and  17  of  boiling  water,  has  a  strong  alkaline  reac- 
tion, and  forms  crystallizable  salts. 

With  ethyl  iodide  codeine  forms  a  crystalline  iodide,  C^H^NOgl  =  C18H21 
(C2H5)N03I,  furnishing  with  silver  oxide  a  soluble  base.  Codeine  being 
considered  as  a  tertiary  monamine,  the  group  C18H2103  represents  3  atoms 
of  hydrogen. 

Codeine  is  homologous  with  morphine,  C,8H2,N03.  It  has  been  the  sub- 
ject of  a  careful  investigation  by  Dr.  Anderson,  who  has  prepared  a  great 
number  of  its  derivatives,  all  of  which  establish  the  formula  above  given. 

Thebaine  or  Paramorphine.  —  This  substance  is  contained  in  the  precipi- 
tate formed  by  calcium  hydrate  in  a  strong  infusion  of  opium,  in  Thibou- 
mery's  process  for  preparing  morphine.  The  precipitate  is  well  washed, 
dissolved  in  dilute  acid,  and  mixed  with  ammonia  in  excess,  and  the  the- 
baine  is  thrown  down  crystallized  from  alcohol.  When  pure,  it  forms 
colorless  needles  like  those  of  narcotine,  but  sparingly  soluble  in  water, 
readily  soluble  in  the  cold  in  alcohol  and  ether.  It  melts  when  heated,  and 
decomposes  at  a  high  temperature.  With  dilute  acids  it  forms  crystalliz- 
able compounds,  and  when  isolated  and  in  solution  has  a  powerfully  alka- 
line reaction. 

A  series  of  other  bases,  papaverine,  C20H2,N04,  pseudo-morphine,  narceine, 
C^H^NOg,  opianine,  and  porphyroxine,  are  also  —  at  least  occasionally  — 
contained  in  opium:  they  are  of  small  importance,  and  comparatively  little 
is  known  respecting  them.  A  considerable  number  of  derivatives  of  papa- 
verine  have  been  prepared,  which  confirm  the  formula  above  given  for  it. 

Cinchonine  and  Quinine.  — It  is  to  these  vegeto-alkalies  that  the  valuable 
medicinal  properties  of  the  Peruvian  barks  are  due.  They  are  associated 
in  the  barks  with  sulphuric  acid,  and  with  a  special  acid,  called  the  quinic 
or  kinic.  Cinchonine  is  contained  in  largest  quantity  in  the  pale  bark,  or 
Cinchona  condaminea ;  quinine  in  the  yellow  bark,  or  Cinchona  cordifolia ; 
the  Cinchona  oblongifolia  contains  both. 

The  simplest,  but  not  the  most  economical,  method  of  preparing  these 
substances  is  to  add  a  slight  excess  of  calcium  hydrate  to  a  strong  decoc- 
tion of  the  ground  bark  in  acidulated  water,  wash  the  precipitate  which 
ensues,  and  boil  it  in  alcohol.  The  solution,  filtered  while  hot,  deposits 
the  vegeto-alkali  on  cooling.  When  both  bases  are  present,  they  may  be 
separated  by  converting  them  into  sulphates :  the  quinine-salt  is  the  less 
soluble  of  the  two,  and  crystallizes  first. 

Pure  cinchonine,  or  cinchonia,  crystallizes  in  small,  but  beautifully  bril- 
liant, transparent,  four-sided  prisms.  It  is  but  very  feebly  soluble  in 
water,  dissolves  readily  in  boiling  alcohol,  and  has  but  little  taste,  although 
its  salts  are  excessively  bitter.  It  is  a  powerful  base,  neutralizing  acids 
completely,  and  forming  a  series  of  crystallizable  salts.  Cinchonine  turns 
the  plane  of  polarization  to  the  right. 

Quinine  or  quina,  much  resembles  cinchonine:  it  does  not  crystallize  so 
well,  however,  and  is  much  more  soluble  in  water :  its  taste  is  intensely 
bitter.  Quinine  turns  the  plane  of  polarization  toward  the  left. 

Cinchonine  is  composed  of     .         .         .         C.^H^N/),  and 
Quinine  Qf C^H^N.O.,. 

Quinine  sulphate  is  manufactured  on  a  very  large  scale  for  medicinal  use : 
it  crystallizes  in  small  white  needles,  which  give  a  neutral  solution.  This 
substance  contains  ^C^H^N./^ .  S04H2 .  7  Aq.  Its  solubility  is  much  in- 
creased by  the  addition  of  a  little  sulphuric  acid,  whereby  the  acid  salt, 
CMH24N2°2-  S04H2.  7  Aq.,  is  formed.  A  very  interesting  compound  lias 
been  produced  by  Dr.  Herapath,  by  the  action  of  iodine  upon  quinine  sul- 


QUINIDINE.  755 

phate.  It  is  a  crystalline  substance  of  a  brilliant  emerald  color,  which 
appears  to  consist  of  equal  equivalents  of  the  sulphate  of  quinine  and  of 
iodine.  This  remarkable  compound  possesses  the  optical  properties  of  the 
tourmaline  (p.  92). 

Cinchonine  and  quinine  yield  with  methyl  iodide,  compounds  represented 
respectively  by  the  formulae  C^H^CHg^OI  and  C20H24(CH3)N2O2I,  which 
are  converted  by  silver  oxide  into  soluble  bases  analogous  to  tetrethyl- 
ammonium  hydrate. 

Quinidine. In  manufacturing  quinine  sulphate,  a  new  base  has  been  ob- 
tained, which  differs  from  quinine  in  some  of  its  physical  properties,  but 
is  said  to  have  the  same  composition.  It  has  been  described  under  the 
name  of  quinidine,  and  appears  to  have  the  same  medicinal  properties  as 
quinine.  The  substance  has  been  carefully  examined  by  Pasteur,  whose 
researches  have  led  to  the  following  interesting  results: 

The  substance  which  is  found  in  commerce  under  the  name  of  quinidine 
is  generally  a  mixture  of  two  alkaloids,  of  which  the  one  is  isomeric  with 
quinine,  and  the  other  with  cinchonine.  Pasteur  designates  these  two  sub- 
stances respectively  as  quinidine  and  cinchonidine.  They  differ  from  quinine 
and  cinchonine  in  several  properties,  but  particularly  in  their  deportment 
with  polarized  light :  for  while  quinine  turns  the  plane  of  polarization  con- 
siderably towards  the  left,  quinidine  exerts  a  powerful  action  towards  the 
right.  Again,  while  cinchonine  deflects  considerably  towards  the  right,  the 
action  of  the  isomeric  cinchonidine  is  in  the  opposite  direction  —  namely, 
towards  the  left.  It  is  evident  that  quinine  and  quinidine  on  the  one  hand, 
and  cinchonidine  and  cinchonine  on  the  other,  stand  to  each  other  in  about 
the  same  relation  as  levo-  and  dextro-tartaric  acids  (p.  677).  Nor  are  the 
terms  wanting  which  correspond  to  racemic  acid.  Pasteur  has,  in  fact, 
proved  that  both  quinine  and  quinidine,  and  likewise  cinchonine  and  cin- 
chonidine, are  peculiarly  modified  by  the  action  of  heat:  exposed  for  sev- 
eral hours  to  a  temperature  varying  between  120°  and  130°  C.  (248°-256°F.), 
quinine  and  quinidine  are  converted  into  a  third  isomeric  alkaloid,  which 
Pasteur  terms  quinicine,  while  cinchonine  and  cinchonidine  furnish  an  iso- 
meric cinchonicine  under  the  same  circumstances.  In  racemic  acid  the  right- 
handed  action  of  dextro-tartaric,  and  the  left-handed  action  of  levo-tar- 
taric  acid,  are  exactly  balanced,  racemic  acid  possessing  no  longer  any  ac- 
tion upon  polarized  light :  in  quinicine  and  cinchonicine,  such  a  perfect 
balance  is  not  observed ;  both  still  exert  a  feeble  right-handed  action, 
which  is,  however,  very  slight  when  compared  with  the  rotatory  powers  of 
the  alkaloids  which  give  rise  to  them.  The  following  table  exhibits  the 
relations  of  the  six  alkaloids,  and  their  analogy  with  the  racemic  group,  in 
a  more  conspicuous  manner: 

Quinine  Quinicine  Quinidine 

Left-handed,  Right-handed,  Right-handed, 

powerfully.  feebly.  very  powerfully, 

Cinchonine  Cinchonicine  Cinchonidine 

Right-handed,  Right-handed,  Left-handed, 

very  powerfully.  feebly.  powerfully. 

Dextro-tartaric  acid     Racemic  acid  Levo-tartaric  acid. 

Right-handed.  neutral.  Left-handed. 

Chino'idine,  Quino'idine,  or  Amorphous  quinine,  is  contained  in  the  refuse,  or 
mother-liquors,  of  the  quinine  manufacture.  In  its  purest  state  it  forms  a 
yellow  or  brown  resin  like  mass,  insoluble  in  water,  freely  soluble  in  alco- 
hol and  ether.  It  is  easily  soluble  also  in  dilute  acids,  and  is  thence  pre- 
cipitated by  ammonia.  Quinoidine  possesses  powerful  febrifuge  properties, 
and  is  identical  in  composition  with  quinine.  It  evidently  bears  to  quinine 


756  NATURAL   ORGANIC   BASES. 

the  same  relation  that  uncrystallizable  syrup  bears  to  ordinary  sugar,  being 
produced  from  quinine  by  the  heat  employed  in  the  preparation. 

From  Cusco-  or  Arica-bark,  and  likewise  from  the  Cinchona  ovata,  or  white 
quinquina  of  Condamine,  a  substance  denominated  Aricine  or  Cinchovatine 
has  been  extracted  :  it  closely  resembles  cinchonine,  and  is  said  to  contain 
C2oH26N2°4-  This  formula  exhibits  a  close  analogy  with  the  formulae  of 
cinchonine  and  quinine.  Aricine  is  useless  in  medicine. 

Strychnine  and  Brucine,  also  called  Strychnia  and  Brucia,  are  contained, 
together  with  several  still  imperfectly  known  bases,  in  Nux  vomica,  in  St. 
Ignatius'  bean,  and  in  false  Angustura  bark.  Strychnine  and  brucine  are 
generally  associated  with  a  peculiar  acid,  called  igasuric  acid.  Nux  vomica 
seeds  are  boiled  in  dilute  sulphuric  acid  until  they  become  soft:  they  are 
then  crushed,  and  the  expressed  liquid  is  mixed  with  excess  of  calcium 
hydrate,  which  throws  down  the  alkaloids.  The  precipitate  is  boiled  in 
spirits  of  wine  of  sp.  gr.  0-850,  and  filtered  hot.  Strychnine  and  brucine 
are  then  deposited  together  in  a  colored  and  impure  state,  and  may  be  sep- 
arated by  cold  alcohol,  in  which  the  latter  dissolves  readily. 

Pure  strychnine  crystallizes  under  favorable  circumstances  in  small  but 
exceedingly  brilliant  octohedral  crystals,  which  are  transparent  and  color- 
less. It  has  a  very  bitter,  somewhat  metallic  taste  (1  part  in  1,000,000 
parts  of  water  is  still  perceptible),  is  slightly  soluble  in  water,  and  fear- 
fully poisonous.  It  dissolves  in  hot,  and  somewhat  dilute  spirit,  but  not  in 
absolute  alcohol,  ether,  or  solution  of  caustic  alkali.  This  alkaloid  may  be 
readily  identified  by  moistening  a  crystal  with  concentrated  sulphuric  acid, 
and  adding  to  the  liquid  a  crystal  of  potassium  bichromate,  when  a  deep 
violet  tint  is  produced,  which  disappears  after  some  time.  Strychnine 
forms  with  acids  a  series  of  well-defined  salts,  which  were  examined  by 
Messrs.  Nicholson  and  Abel,  who  established  for  strychnine  the  formula 
C21H22N202. 

Strychnine  forms  with  ethyl  iodide  a  crystalline  compound,  C21H22(C2H5) 
N204I,  converted  by  silver  oxide  into  a  soluble  base. 

Brucine,  C^H^N^,  is  easily  distinguished  from  the  preceding  substance, 
which  it  much  resembles  in  many  respects,  by  its  ready  solubility  in  alco- 
hol, both  hydrated  and  absolute.  It  dissolves  also  in  about  500  parts  of 
hot  water.  The  salts  of  brucine  are,  for  the  most  part,  crystallizable. 

Veratrine,  or  Veratria,  C32H52N208,  is  obtained  from  the  seeds  of  Veratrum 
sabadilla.  In  the  pure  state  it  is  a  white  or  yellowish-white  powder,  which 
has  a  sharp  burning  taste,  and  is  very  poisonous.  It  is  remarkable  for 
occasioning  violent  sneezing.  It  is  insoluble  in  water,  but  dissolves  in  hot 
alcohol,  in  ether,  and  in  acids :  the  solution  has  an  alkaline  reaction. 

A  substance  called  colchicine,  extracted  from  the  Colchicum  autumnale,  and 
formerly  confounded  with  veratrine,  is  now  considered  distinct :  its  history 
is  still  imperfect. 

Harmaline,  C13H,4N20. — This  compound  is  extracted  by  dilute  acetic 
acid  from  the  seeds  of  the  Peganum  harmala,  a  plant  which  grows  abun- 
dantly on  the  Steppes  of  Southern  Russia,  and  the  seeds  of  which  are  used 
in  dyeing.  When  pure,  it  forms  yellowish  prismatic  crystals,  soluble  in 
alcohol  and  dilute  acids,  but  scarcely  forming  crystallizable  salts.  By  oxi- 
dation it  gives  rise  to  another  compound,  harmine,  C,3H,2N20,  which  also 
possesses  basic  properties. 

Caffeine,  or  Theine,  C8H,0N402.  —  This  remarkable  substance  occurs  in  four 
articles  of  domestic  life,  infusions  of  which  are  used  as  beverages  over  the 
greater  part  of  the  known  world — namely,  in  tea  and  coffee,  in  the  leaves 
of  Guarana  ojficinalis,  or  Paullinia  sorbilis,  and  in  those  of  Ilex  Paraguay ensts  ; 


THEOBROMINE — XANTHINE.  757 

it  will  probably  be  found  in  other  plants.  A  decoction  of  common  tea,  or 
of  raw  coffee-berries,  previously  crushed,  is  mixed  with  excess  of  solution 
of  basic  lead  acetate.  The  solution,  filtered  from  the  copious  yellow  or 
greenish  precipitate,  is  treated  with  sulphuretted  hydrogen  to  remove  the 
lead,  then  filtered,  evaporated  to  a  small  bulk,  and  neutralized  by  ammo- 
nia. The  caffeine  crystallizes  out  on  cooling,  and  is  easily  purified  by 
animal  charcoal.  It  forms  tufts  of  delicate,  white,  silky  needles,  which 
have  a  bitter  taste,  melt  when  heated  with  loss  of  water,  and  sublime  with- 
out decomposition.  It  is  soluble  in  about  100  parts  of  cold  water,  and 
much  more  easily  at  the  boiling  heat,  or  if  an  acid  be  present.  Alcohol 
also  dissolves  it,  but  not  easily.  The  basic  properties  of  caffeine  are  fee- 
ble. The  salts  which  it  forms  with  hydrochloric  and  sulphuric  acids  are 
obtained  only  with  difficulty.  It  forms,  however,  splendid  double  salts 
with  platinum  tetrachloride  and  gold  trichloride.  The  products  of  oxida- 
tion of  caffeine,  which  have  been  studied  by  Rochleder,  are  of  considerable 
interest,  inasmuch  as  both  their  composition  and  their  properties  establish 
a  close  connection  between  these  products  and  the  derivatives  of  uric  acid. 
Under  the  influence  of  chlorine,  caffeine  yields  amalic  acid,  a  substance  of 
feebly  acid  properties,  having  the  composition  of  hydrated  tetramethyl- 
alloxantin,  C8(CH3)4N407 .  Aq.  When  treated  with  oxidizing  agents,  it 
yields  cholestrophane,  C6H6N203,  corresponding  to  parabanic  acid  of  the  uric 
acid  series.  Cholestrophane  may  be  viewed  as  dimethyl-parabanic  acid; 
it  has,  in  fact,  been  obtained  by  digesting  silver  parabanate  with  methyl 
iodide : 

C3Ag2N203  +   2CH3I  ==  2AgI   +    C5H6N203. 

Lastly,  the  murexide  of  the  caffeine  series  is  formed  by  the  treatment  of 
amalic  acid  with  ammonia,  exactly  as  the  true  murexide  from  uric  acid  is 
formed  by  the  action  of  ammonia  upon  alloxantin.  The  new  murexide 
imitates  its  prototype,  not  only  in  composition,  but  likewise  in  the  green 
metallic  lustre  of  its  crystals,  and  the  deep  crimson  color  of  its  solutions. 

Theobromine.  —  The  seeds  of  the  Theobroma  Cacao,  or  cacao-nuts,  from 
which  chocolate  is  prepared,  contain  a  crystallizable  principle,  to  which 
this  name  is  given.  It  is  extracted  in  the  same  manner  as  caffeine,  and 
forms  a  white,  crystalline  powder,  which  is  much  less  soluble  than  the  last- 
named  substance.  It  contains,  according  to  Glasson,  C7H8N402.  Theobro- 
mine  is  easily  soluble  in  aqueous  ammonia ;  by  adding  silver  nitrate  to  this 
solution,  and  boiling,  a  crystalline  precipitate  of  silver-theobromine,  C7Ht 
AgN402,  is  obtained.  By  treating  this  silver  compound  with  methyl  iodide, 
Strecker  obtained  silver  iodide  and  caffeine :  C7H7AgN402  -f  CH3I  =  Agl 
~h  C8H10N402,  which  may  be  extracted  with  alcohol.  Caffeine  must  there- 
fore be  regarded  as  methyl-theobromine.  The  products  obtained  from 
theobromine  by  oxidation  appear  to  be  homologous  with  several  terms  of 
the  uric  acid  series. 

Xanthine,  C5H4N402.  —  Xanthine  was  first  described  by  Dr.  Marcet  under 
the  name  of  xanthic  oxide,  which  he  discovered  as  a  constituent  of  urinary 
calculi;  recently  it  has  been  found  among  the  products  of  the  decomposi- 
tion of  guanine.  It  is  present  in  nearly  every  part  of  the  animal  organism, 
and,  although  in  very  minute  quantities,  in  urine. 

Xanthine,  according  to  Strecker,  may  be  prepared  with  the  greatest 
facility  from  guanine  (p.  758).  Potassium  nitrite  is  added  to  a  solution  of 
guanine  in  concentrated  nitric  acid  until  a  powerful  evolution  of  red  fumes 
takes  place:  the  solution  is  then  mixed  with  a  large  quantity  of  water, 
whereby  a  yellow  substance  is  precipitated,  which,  after  washing  with  wa- 
ter, is  issolved  m  ammonia.  A  solution  of  ferrous  sulphate  is  now  added 


758  NATURAL    ORGANIC    BASES. 

until  a  black  precipitate  of  iron  oxide  begins  to  appear.*  The  still  power- 
fully ammoniacal  solution  is  filtered  and  evaporated  to  dryness ;  and  the 
residue  is  extracted  with  water  in  order  to  separate  the  ammonium  sulphate; 
then  dissolved  in  ammonia,  and  evaporated.  Xanthine  is  a  white,  amor- 
phous powder,  difficultly  soluble  in  water,  soluble  in  acids,  with  which  it 
forms  crystalline  compounds.  The  sulphate  has  the  composition  2C5H4N4 
0  .  S04H2.  Xanthine  dissolves  with  facility  in  ammonia  and  potash.  Its 
characteristic  property  is  to  dissolve  without  evolution  of  gas  in  nitric  acid, 
and  to  give  on  evaporation  a  deep-yellow  residue,  which,  on  addition  of 
ammonia  or  solution  of  potash,  assumes  a  yellow-red  color.  By  treatment 
of  silver-xanthine,  C5H2Ag2N4H2,  with  methyl  iodide,  Strecker  obtained  a 
body  isomeric  with  theobromine,  differing,  however,  in  its  properties  from 
that  substance : 

C5H2Ag2N402    +     2CH3I    =    2AgI     -f     C7H8N402. 

Sarcine  (Hypoxanthine),  C5H4N40.  —  This  base  is  a  constituent  of  the 
flesh  of  vertebrata.  It  is  best  prepared  from  the  mother-liquor  of  creatin 
(p.  902),  by  diluting  with  water  and  boiling  with  cupric  acetate,  whereby 
the  sarcine  is  precipitated  in  combination  with  cupric  oxide.  This  preci- 
pitate is  dissolved  in  nitric  acid  and  mixed  with  silver  nitrate;  the  crys- 
tals, a  compound  of  sarcine  nitrate  with  silver  nitrate,  are  purified  by 
re-crystallization  from  nitric  acid,  and  are  then,  by  ebullition  with  an  am- 
moniacal solution  of  silver  nitrate,  converted  into  the  compound  of  sarcine 
with  silver  oxide,  C5H4N40 .  Ag20,  which  is  decomposed  by  sulphuretted 
hydrogen. 

Sarcine  forms  delicate  white  microscopic  needles,  difficultly  soluble  in 
cold  water,  easily  soluble  in  boiling  water,  in  dilute  acids,  ammonia,  pot- 
ash, and  baryta-water.  Sarcine  forms  crystallizable  salts,  containing  1 
equivalent  of  acid.  It  unites  with  bases,  like  guanine,  forming  crystalline 
compounds  containing  2  equivalents  of  metallic  oxide. 

Guanine,  C5H5N50.  —  This  base  was  first  obtained  from  guano;  it  has 
also  been  proved  to  exist  in  the  pancreatic  juice  of  mammalia,  and  in  the 
excrement  of  the  spider.  To  prepare  it,  guano  is  boiled  with  water  and 
calcium  hydrate  until  a  portion  of  the  liquid,  when  filtered,  appears  but 
slightly  colored:  the  whole  is  then  filtered,  and  the  filtrate  saturated  with 
acetic  acid,  whereby  the  guanine  is  precipitated,  mixed  with  uric  acid.  It 
is  purified  by  solution  in  hydrochloric  acid  and  precipitation  by  ammonia. 

Guanine  is  a  colorless,  crystalline  powder,  insoluble  in  water,  alcohol, 
ether,  and  ammonia,  soluble  in  acids  and  solution  of  potash.  With  acids 
it  forms  crystallizable  salts  containing  1  and  2  equivalents  of  acid :  it  com- 
bines with  bases  to  crystalline  compounds  containing  2  equivalents  of  metal- 
lic oxide. 

Guanine,  sarcine,  and  xanthine  bear  a  great  resemblance  to  each  other, 
and  are  all  found  in  the  animal  organism.  Guanine,  on  account  of  its  in- 
solubility in  water  and  ammonia,  may  easily  be  separated  from  the  two 
other  substances.  To  separate  xanthine  and  sarcine,  they  are  converted 
into  the  hydrochlorides,  which  are  treated  with  warm  water :  xanthine  hy- 
drochloride  is  so  little  soluble  in  that  liquid,  that  it  may  easily  be  separated 
from  the  admixed  sarcine  hydrochloride. 

Guanidine,  CH5N3  — This  substance  is  prepared  from  guanine.  Guanine 
is  treated  with  hydrochloric  acid  and  potassium  chlorate,  whereby  it  is  con- 
verted into  a  mixture  of  guanidine  and  parabanic  acid.  As  soon  as  the 
guanine  is  completely  dissolved,  the  liquid  is  evaporated  till  the  parabanic 

*  The  treatment  of  gnanine  with  nitric  acid  gives  rise  to  xanthine  and  nitroxanthine,  which 
by  the  action  of  reducing  agents  is  converted  into  xanthine.  Strecker  recommends  a  ferrous 
salt  for  this  purpose. 


CREATIN —  CREATININE —  SARCOSINE.  759 

acid  has  crystallized  out.  The  mother-liquor  is  treated  with  a  mixture  of 
alcohol  and  ether,  which,  separated  from  the  residue  and  evaporated, 
yields  on  evaporation  the  crude  guanidine  hydrochloride.  The  hydro- 
chloride  may,  by  digestion  with  silver  sulphate,  be  converted  into  the 
sulphate,  and  the  latter  finally  into  the  free  base  by  addition  of  baryta- 
water. 

Guanidine  thus  prepared  forms  colorless  crystals,  readily  soluble  in  water 
and  alcohol;  the  solution  has  a  powerfully  alkaline  reaction.  It  absorbs 
carbonic  acid  from  the  air,  forming  a  carbonate  2CH5N3  .  H2COj,  which  has 
an  alkaline  reaction,  and  crystallizes  in  square  prisms.  The  transforma- 
tion of  guanine  into  parabanic  acid  and  guanidine  is  represented  by  the 
following  equation: 

C5H5N50     +    0.    +     H20     =     C3H2N208    +     CH5N3    +     C02. 

Triethylguamdine. — The  action  of  sodium  alcohol  upon  ethyl  cyanate  or 
cyanurate  gives  rise  to  a  base  having  the  composition  C7H17N3,  which  is 
that  of  triethylguanidine  (carbotriethyltriamine).  It  is  formed  according 
to  the  following  equation : 

3CN(C2H6)0  +  2C2II5NaO  =  C7H17N3  +  2C2H4  +  C02  +  Na2C03. 

Creatin,  C4H9N302 .  2  Aq. — Creatin  was  first  observed  by  Chevreul,  and 
has  been  studied  very  carefully  by  Liebig,  who  obtained  it  from  the  soup 
of  boiled  meat.  It  is  prepared  from  the  juice  of  raw  flesh  by  the  follow- 
ing process :  A  large  quantity  of  lean  flesh  is  cut  up  into  shreds,  exhausted 
by  successive  portions  of  cold  water,  strained  and  pressed.  The  liquid, 
which  has  an  acid  reaction,  is  heated  to  coagulate  albumin  and  coloring 
matter  of  blood,  and  passed  through  a  cloth.  It  is  then  mixed  with  pure 
baryta-water  as  long  as  a  precipitate  appears,  filtered  from  the  deposit  of 
phosphates,  and  evaporated  in  a  water-bath  to  a  syrupy  state.  After 
standing  some  days  in  a  warm  situation,  the  creatin  is  gradually  deposited 
in  crystals,  which  are  easily  purified  by  re-solution  in  water  and  digestion 
with  a  little  animal  charcoal.  * 

When  pure,  creatin  forms  colorless,  brilliant,  prismatic  crystals,  which 
become  dull  by  loss  of  water  at  100°.  They  dissolve  readily  in  boiling 
water,  sparingly  in  cold  water,  and  are  but  little  soluble  in  alcohol.  The 
aqueous  solution  has  a  weak  bitter  taste,  followed  by  a  somewhat  acrid 
sensation.  In  an  impure  state  the  solution  readily  putrefies.  Creatin  is  a 
neutral  body,  not  combining  either  with  acids  or  with  alkalies.  In  the 
crystallized  state  it  contains  C4H9N302 .  2H20. 

Creatinine,  C4H7N30.  —  By  the  action  of  strong  acids,  creatin  is  converted 
into  creatinine,  a  powerful  organic  base,  with  separation  of  the  elements  of 
water.  The  new  substance  forms  colorless  prismatic  crystals,  and  is  much 
more  soluble  in  water  than  creatin:  it  has  a  strong  alkaline  reaction,  and 
forms  crystallizable  salts  with  acids 

Creatinine  pre-exists  to  a  small  extent  in  the  juice  of  flesh,  together 
with  lactic  acid  and  other  bodies  not  yet  perfectly  examined.  It  is  also 
found  in  conjunction  with  creatin  in  urine. 

Sarcosine,  C3H7N02,  formed  by  boiling  creatin  with  baryta-water,  has 
the  composition  of  methyl-glycocine  or  methyl-amidacetic  acid,  C2H4(CII3) 
N02,  and  has  been  already  described  among  the  derivatives  of  acetic  acid 
(p.  614). 

*  The  mother-liquid  from  flesh  from  which  the  creatin  has  been  deposited  contains,  among 
other  things,  a  new  acid,  the  inosinic.  the  aqueous  solution  of  which  refuses  to  crystallize.  It 
has  a  strong  acid  reaction,  and  is  precipitated  in  a  white  amorphous  condition  by  alcohol.  It 
probably  cont 


760     PHOSPHORUS,  ANTIMONY,  AND  ARSENIC  BASES. 

Berberine,  C21H,9N06,  is  a  substance  crystallizing  in  fine  yellow  needles, 
slightly  soluble  in  water,  extracted  from  the  root  of  the  Berberis  vulgaris. 
It  has  feeble  basic  properties.  This  must  not  be  confounded  with  bcbeerine, 
an  uncrystallizable  basic  substance,  from  the  bark  of  the  green-heart  tree  of 
Guiana,  which  has  the  composition  C,9H21N03. 

Piperine,  C34H38N206.  —  A  colorless,  or  slightly  yellow  crystallizable  prin- 
ciple, extracted  from  pepper  by  the  aid  of  alcohol.  It  is  insoluble  in  water. 
Piperine  readily  dissolves  in  acids  ;  definite  compounds  are,  however,  dif- 
ficult to  obtain. 

Conine  (Conitine,  or  Conia),  Nicotine,  and  Sparteine  differ  from  the  other 
vegetable  bases  in  physical  characters  ;  they  are  volatile  oily  liquids.  The 
first  is  extracted  from  hemlock,  the  second  from  tobacco,  and  the  third 
from  broom  (Spartium  Scoparium).  They  agree  in  most  of  their  characters, 
having  high  boiling  points,  very  poisonous  properties,  strong  alkaline  reac- 
tion, and  the  power  of  forming  crystallizable  salts  with  acids.  The  for- 
mula of  nicotine  is  C10H14N2;  that  of  conine,  C8H,5N  ;  and  that  of  sparteine, 

10      2fi      2* 

Clos'ely  allied  to  conine  is  conhydrine,  CgH,7NO,  a  crystalline  base,  ex- 
tracted by  Wertheim  from  hemlock.  When  distilled  with  anhydrous  phos- 
phoric acid,  it  splits  into  conine  and  one  molecule  of  water. 

A  mixture  of  nicotine  with  methyl  or  ethyl  iodide  solidifies  after  a  short 
time  to  crystalline  masses,  containing  C10H14(CH3)2N2I2,  andCJOHu(C2H6)2N2I2, 
convertible  by  silver  oxide  into  soluble  bases. 

Conine  is  a  secondary  monamine.  Treated  with  ethyl  iodide,  it  yields 
successively  two  iodine-compounds  —  namely,  C8H15(C2H5)NI  and  C8HU(C2 
H5)2NI.  The  latter  is  converted  by  silver  oxide  into  a  soluble  base. 

There  are  very  many  other  bodies,  more  or  less  perfectly  known,  having 
to  a  certain  extent  the  properties  of  alkaloids  :  the  following  statement  of 
the  names  and  mode  of  occurrence  of  a  few  of  them  must  suffice. 

Hyoscyamine  (Dc/turinc).  —  A  white,  crystallizable  substance,  from  Hyos- 
cyamus  niger  ;  it  occurs  likewise  in  Datura  Stramonium. 

Atropine.  —  Colorless  needles,  from  Atr  op  a  Belladonna  ;  formula  ^H^NO.,. 

Solanine.  —  A  pearly,  crystalline  substance,  from  various  solanaceous 
plants;  formula  C43HnNOl6  (?)  (p.  582). 

Aconitine.  —  A  glassy,  transparent  mass,  from  Aconitum  Napellus  :  formula 


Delphmine.  —A  yellowish,  fusible  substance,  from  the  seeds  of  Delphinium 
Staphisagria. 

Emetine.  —  A  white  and  nearly  tasteless  powder  from  ipecacuanha  root. 
Curarine.  —  The  arrow-poison  of  Central  America. 


HI.  —  Phosphorus,  Antimony,  and  Arsenic  Bases. 

Phosphorus,  antimony,  and  arsenic  being,  like  nitrogen,  either  trivalent 
or  quinquivalent,  are  capable  of  forming  compounds  analogous  to  the  amines 
and  the  compound  ammonium  salts.  A  few  of  these  remarkable  compounds 
will  be  briefly  described  in  the  following  paragraphs. 


PHOSPIIINES. 

Paul  Th^nard,  by  passing  the  vapor  of  methyl  chloride  over  calcium 
phosphide  heated  to  about  180°  C.  (356°  F.),  obtained  a  mixture  of  phos- 


ANTIMONY   BASES.  761 

phoretted  bodies,  from  which  he  separated  three  compounds  believed  to 
correspond  in  composition  with  the  three  hydrides  of  phosphorus  (p.  215), 
viz.,  P2(CH3),  P(CH3)2,  and  P(CH3)3;  these  bodies  were,  however,  but  very 
imperfectly  investigated.  More  recently  Cahours  and  Hofmann,  by  sub- 
jecting zinc-methyl  and  zinc-ethyl  to  the  action  of  phosphorus  trichloride, 
have  obtained  saline  compounds,  from  which,  by  distillation  with  potash, 
the  bases  P(CH3)3  and  P(C2H5)3,  analogous  to  the  tertiary  monamines,  may 
be  liberated ;  thus  : 

3Zn(C2H5)2       +       2PC13      =       3ZnCl2       +       2P(C2H5)3. 
Zinc-ethyl.  Triethyl-phosphine. 

Thriethylphosphine,  C6H15P  —  P(C2H5)3.  —  This  substance  is  a  colorless 
oil  having  a  very  penetrating  phosphorus  odor,  and  boiling  at  133°.  It  is 
slowly  oxidized  in  atmospheric  air.  The  vapor,  heated  with  air  or  oxygen, 
explodes.  In  chlorine  gas  it  burns  with  separation  of  carbon,  hydro- 
chloric acid  and  phosphorus  pentachloride  being  produced.  With  acids 
it  forms  crystalline  compounds,  which  are  very  deliquescent.  With  iodide 
of  methyl,  ethyl,  and  amyl,  it  solidifies  after  a  few  moments  to  crys- 
talline compounds,  containing  respectively  P(C2H6)3(CH3)I,  P(C2H5)4I,  and 
P(C2H5)3(C5H11)I,  which  are  decomposed  by  silver  oxide,  yielding  power- 
fully alkaline  liquids,  containing  the  hydrates  P(C2H5)3(CH3)(OH),  P(C2H5)4 
(OH),  and  P(C2H5)3(C5H11)OH,  which  in  every  respect  resemble  hydrate  of 
tetrethyl  ammonium  and  its  homologues. 

Trimethylphosphine,  C3H9P  =  P(CH3)3.  —  This  substance  is  very  similar 
to  the  corresponding  ethyl-base,  but  more  volatile.  When  left  in  contact 
with  atmospheric  air,  it  forms  an  oxide  which  crystallizes  in  beautiful  white 
needles.  With  iodide  of  methyl,  ethyl,  and  amyl,  it  yields  the  iodides 
P(CH3)4I,  P(CH3)3(C2H5)I,  and  P(CH3)3(C5Hn) I,  from  which  three  analogous 
hydrates  may  be  produced  by  means  of  silver  oxide. 


ANTIMONY  BASES  or  STIBINES. 

Triethylstibine,  or  Stibethyl,  Sb(C2H5)3,  is  obtained  by  distilling  ethyl 
iodide  with  an  alloy  of  antimony  and  potassium.  It  is  a  transparent,  very 
mobile  liquid,  having  a  penetrating  odor  of  onions.  It  boils  at  158°  C. 
(316°  F.).  In  contact  with  atmospheric  air,  it  emits  a  dense  white  fume, 
and  frequently  even  takes  fire,  burning  with  a  white  brilliant  flame.  It  is 
analogous  in  many  of  its  reactions  to  triethylamine,  but  has  much  more 
powerful  combining  tendencies,  uniting  readily  with  two  atoms  of  chlorine, 
bromine,  or  iodine,  and  1  atom  of  oxygen  or  sulphur,  thereby  forming 
compounds  in  which  the  antimony  is  quinquivalent,  such  as  Sbv(C2H6)3Cl2, 
Sbv(C2H5)30//,  &c.  The  same  tendency  to  act  as  a  bivalent-radical  is,  how- 
ever, exhibited  by  triethylamine,  which,  though  it  does  not  unite  directly 
with  elementary  bodies,  can  nevertheless  take  up  a  molecule  of  hydrogen 
chloride,  ethyl  iodide,  &c.,  likewise  producing  compounds  in  which  the 
nitrogen  is  quinquivalent,  e.g.,  NV(C2H5)?HC1,  NV(C2H5)3(C2H6)I,  &c. 

Stibethyl  oxide,  Sb(C2H5)30,  forms  a  viscid  transparent  mass,  soluble  in 
water  and  alcohol.  It  is  extremely  bitter  and  not  poisonous.  It  cannot  be 
volatilized  without  decomposition.  It  combines  with  acids,  giving  rise  to 
crystallizable  salts  containing  two  equivalents  of  acid. 

Stibethyl  sulphide,  Sb(C2H5)3S. — Beautiful  crystals  of  silvery  lustre,  solu- 
ble in  water  and  alcohol.  Their  taste  is  bitter,  and  their  odor  similar  to 
that  of  mercaptan.  The  solution  of  this  compound  exhibits  the  deport- 
ment of  an  alkaline  sulphide :  it  precipitates  metals  from  their  solutions 
64* 


762  ARSENIC   BASES. 

as  sulphides,  a  soluble  salt  of  stibetbyl  being  formed  at  the  same  time. 
This  deportment,  indeed,  affords  the  simplest  means  of  preparing  the  salts 
of  stibethyl. 

Stibethyl  chloride,  Sb(C2H6)3Cl2. —Colorless  liquid  having  the  odor  of  tur- 
pentine oil. 

Stibethyl  iodide,  Sb(C2H5)3T2. —  Colorless  needles  of  intensely  bitter  taste. 

The  analogy  of  triethylstibine  with  triethylamine  is  best  exhibited  in  its 
deportment  with  ethyl  iodide.  The  two  substances  combine,  forming  a  new 
iodide,  containing  Sb(C2H5)4I,  from  which  silver  oxide  separates  a  powerful 
alkaline  base  analogous  to  tetrethyl-ammonium  hydrate : 

N(C2H6)4(OH)  Sb(C2H5)4OH. 

A  series  of  analogous  substances  exist  in  the  methyl  series.  They  have 
been  examined  by  Landolt,  who  has  described  several  of  their  compounds, 
and  separated  the  methyl-antimony-base  corresponding  to  tetramethyl- 
ammonium  hydrate. 

The  iodide,  Sb(CH3)4I,  produced  by  the  action  of  methyl  iodide  upon  tri- 
methylstibine,  Sb(CH3)3,  crystallizes  in  white  six-sided  tables,  which  are 
easily  soluble  in  water  and  alcohol,  and  slightly  soluble  in  ether.  It  has 
a  very  bitter  taste,  and  is  decomposed  by  the  action  of  heat.  When  treated 
with  silver  oxide,  it  yields  a  powerfully  alkaline  solution,  exhibiting  all  the 
properties  of  potash,  from  which,  on  evaporation,  a  white  crystalline  mass, 
the  hydrate  of  tetramethylstibonium,  Sb(CH3)4(OH),  crystallizes.  This  com- 
pound forms  an  acid  salt  with  sulphuric  acid,  which  crystallizes  in  tables. 
It  contains  Sb(CH3)4HS04. 


ARSENIC  BASES. 

Triethylarsine,  As(C2H5)3,  is  produced  by  distilling  an  alloy  of  arsenic 
and  sodium  with  ethyl  iodide.  At  the  same  time,  also,  there  is  formed  an- 
other body,  containing  As2(C2H5)4,  analogous  to  arsendimethyl  or  cacodyl. 
Both  compounds  are  liquids  of  powerful  odor;  they  may  be  separated  by 
distillation  in  an  atmosphere  of  carbon-dioxide,  the  triethylarsine  passing 
over  last. 

Triethylarsine  may  be  obtained  pure  by  a  process  analogous  to  that  em- 
ployed for  the  preparation  of  triethylphosphine,  namely,  by  distilling  arse- 
nious  chloride,  AsCl3,  with  zinc-ethyl.  It  is  a  colorless  liquid  of  most  dis- 
agreeable odor,  similar  to  that  of  arsenetted  hydrogen,  soluble  in  water, 
alcohol,  and  ether,  and  boiling  at  140°.  Triethyiarsine  combines  directly 
with  oxygen,  sulphur,  bromine,  and  iodine,  giving  rise  to  a  series  of  com- 
pounds containing  2  atoms  of  bromine  or  iodine,  1  atom  of  sulphur  or  oxy- 
gen, and  analogous  to  the  corresponding  compounds  of  triethylstibine. 

Triethylarsine  submitted  to  the  action  of  ethyl  iodide  yields  a  crystalline 
compound,  As(C2H5)^I,  from  which  freshly  precipitated  silver  oxide  sepa- 
rates the  corresponding  hydrate,  As(C2H5)4OH,  a  powerfully  alkaline  sub- 
stance, similar  to  the  corresponding  nitrogen-,  phosphorus-,  and  antimony- 
compounds. 

Analogous  substances  exist  in  the  methyl  series.  Trimethylarsine, 
As(CH3)a'  is  formed,  together  with  arsendimethyl  or  cacodyl,  As2(CH3)4, 
when  an  alloy  of  arsenic  and  sodium  is  submitted  to  the  action  of  methyl 
iodide.  It  unites  with  methyl  iodide,  producing  tetramethylarsonium 
iodide,  As(CH3)4I,  from  which  silver  oxide  separates  the  hydrate,  As(CH3)4 
)H.  The  iodide  just  mentioned  is  formed,  together  with  iodide  of  cacodyl, 
when  cacodyl  is  acted  upon  by  methyl  iodide: 

As2(CH3)4     +     2CH3I     =     As(CH3)4I     -f     As(CH3)2I. 


AESENIC   BASES.  763 

By  substituting  ethyl  iodide  for  methyl  iodide  in  this  reaction,  the  com- 
pound As(CH3)2(C2H5)2I  is  formed.  All  these  iodides,  treated  with  moist 
silver  oxide,  yield  the  corresponding  hydrates. 

Arsendimethyl  and  arsenmonomethyl  will  be  most  conveniently  described 
in  this  place,  though  they  do  not  strictly  belong  to  the  ammonia  type,  at 
least  when  in  the  free  state. 

As'"(CH3)2 

Arsendimethyl  or  Cacodyl,  As2(CH3)4,  or    j  .  —  The  arsenic  in 

this  compound  is  still  trivalent,  one  unit  of  equivalence  of  each  of  the 
arsenic-atoms  being  satisfied  by  combination  with  the  other,  just  as  in  the 
solid  hydrogen  arsenide,  As2H4  (p.  423).  When,  however,  the  arsendi- 
methyl  combines  with  chlorine  or  other  monatomic  radicals,  the  molecule 
splits  into  two  ;  thus  : 

As(CH3)4        +        C12        =        2AS'"(CH8)aCl. 

Cacodyl,  so  called  from  its  repulsive  odor,  constitutes,  together  with  its 
products  of  oxidation,  the  spontaneously  inflammable  liquid  known  as  Ca- 
det's fuming  liquid,  or  Alkarsin.  This  liquid  is  prepared  by  distilling  potas- 
sium acetate  with  arsenious  oxide.  Equal  weights  of  these  two  substances, 
both  well  dried,  are  intimately  mixed  and  introduced  into  a  glass  retort 
connected  with  a  condenser  and  tubulated  receiver  cooled  by  ice,  a  tube 
being  attached  to  the  receiver  to  carry  away  the  permanently  gaseous  pro- 
ducts to  some  distance  from  the  experimenter.  Heat  is  then  applied  to  the 
retort,  which  is  gradually  increased  to  redness.  At  the  close  of  the  opera- 
tion, the  receiver  is  found  to  contain  two  liquids,  besides  a  quantity  of  re- 
duced arsenic  :  the  heavier  of  these  is  the  crude  cacodyl;  the  other  consists 
chiefly  of  water,  acetic  acid,  and  acetone.  The  gas  given  off  during  the 
distillation  is  principally  carbon  dioxide.  The  crude  cacodyl  is  repeatedly 
washed  by  agitation  with  water  previously  freed  from  air  by  boiling,  and 
afterwards  redistilled  from  potassium  hydrate  in  a  vessel  filled  with  pure 
hydrogen  gas.  All  these  operations  must  be  conducted  in  the  open  air. 

Pure  cacodyl  is  obtained  by  'decomposing  the  chloride  with  metallic  zinc, 
dissolving  out  the  zinc  chloride  with  water,  and  dehydrating  the  oily  liquid 
with  calcium  chloride.  The  strong  tendency  of  cacodyl  to  take  fire  in  the 
air,  and  the  extremely  poisonous  character  of  its  vapors,  render  it  neces- 
'sary  to  perform  all  the  distillations  in  sealed  vessels  filled  with  dry  carbon 
dioxide.  Bunsen,  to  whose  skill  and  perseverance  we  are  indebted  for  the 
discovery  of  this  remarkable  compound,  proceeds  as  follows : 

1.  A  dilute  alcoholic  solution  of  alkarsin   is   cautiously  mixed  with  an 
equally  dilute  solution  of  mercuric  chloride,  avoiding  an  excess  of  the  lat- 
ter; a  white  crystalline,  inodorous  precipitate   then  falls,  containing  As3 
(CH3)40  .  HgCl2:   when  this  is  distilled  with  concentrated  hydrochloric  acid, 
it  yields  mercuric  chloride,  water,  and  cacodyl  chloride,  which  distils  over. 
The  product  is  left  for  some  time  in  contact  with  calcium  chloride  and  a 
little    quicklime,   and   then  distilled    alone   in    an   atmosphere   of  carbon 
dioxide. 

2.  To  obtain  free  cacodyl,  the  pure  anhydrous  chloride  is  digested  for 
three  hours  at  a  temperature  of  100°  with  slips  of  clean  metallic  zinc  con- 
tained in  a  bulb  blown  upon  a  glass  tube  previously  filled  with   carbonic 
acid  gas,  and  hermetically  sealed.     The  metal  dissolves  quietly  without 
evolution  of  gas.     When  the  action  is  complete,  and  the  whole  cool,  the 
vessel  is  observed  to  contain  a  white  saline  mass,  which,  on  the  admission 
of  a  little  water,  dissolves,  and  liberates  a  heavy  oily  liquid,  the  cncod \1 
itself.     This  is  rendered  quite  pure  by  distillation    from  a  fresh  quantity 
of  zinc,   the  process  being  conducted  in  the  little  apparatus  shown  in 


764  ARSENIC   BASES. 

fig.  196,  which  is  made  from  a  piece  of  glass  tube,  and  is  intended  to  serve 
the  purpose  both  of  retort  and  receiver.     The  zinc  is  introduced  into  the 
upper  bulb,  and  the  tube    drawn   out  in   the  manner   represented.     The 
whole  is  then  filled  with  carbon  dioxide,  and   the  lower 
Fig.  196.          extremity   put   into   communication   with   a   little   hand- 
syringe.     On  dipping  the  point  a  into  the  crude  cacodyl, 
and  making  a  slight  movement  of  exhaustion,  the  liquid 
is  drawn  up  into  the  bulb.     Both   extremities  are  then 
sealed  in  the  blowpipe  flame,  and  after  a  short  digestion 
at  100°,  or  a  little  above,  the  pure  cacodyl  is  distilled  off 
into  the  lower  bulb,  which  is  kept  cool.     It  forms  a  color- 
less, transparent,  thin  liquid,  much  resembling  alkarsin 
in  odor,  and  surpassing  that  substance  in  inflammability. 
When  poured  into  the  air,  or  into  oxygen  gas,  it  ignites 
instantly:  the  same  thing  happens  with  chlorine.     With 
very  limited  access  of  air  it  throws  off  white  fumes,  pass- 
ing into  oxide,  and  eventually  into  cacodylic  acid.     Caco- 
dyl boils  at  170°  C.  (338°  F.),  and  when  cooled  to  —6°  C. 
(21°  F.),  crystallizes  in  large,  transparent,  square  prisms. 
It  combines  directly  also  with  sulphur. 
Cacodyl  is  decomposed  at  a  temperature,  below  redness  into  metallic  arse- 
nic, and  a  mixture  of  2  measures  of  marsh-gas  and  1  measure  of  ethene 
gas. 

The  powerful  combining  tendencies  of  cacodyl  indicate  that  it  is  an  un- 
saturated  compound  :  it  can,  in  fact,  take  up  2  atoms  of  a  monad  or  1  atom 
of  a  dyad  element,  forming  compounds  like  the  chloride,  As2(CH3)4Cl2  = 
2As(CH3)2Cl,  and  the  oxide,  As2(CH3)40,  in  which  the  arsenic  is  trivalent; 
or  again,  6  atoms  of  a  monad  or  3  atoms  of  a  dyad  element,  forming  com- 
pounds like  the  trichloride,  As2(CH3)4Cl6  —  2As(CH3)2Cl3,  in  which  arsenic 
is  quinquivalent.  These  last-mentioned  bodies  are  the  most  stable  of  all 
the  cacodyl  compounds. 

CACODYL  CHLORIDE,  or  ARSEN-CHLORODIMETHIDE,  As'"(CHs)2Cl,  prepared 
as  above  described,  is  a  colorless  liquid,  which  does  not  fume  in  the  air, 
but  emits  an  intensely  poisonous  vapor.  It  is  heavier  than  water,  and  in- 
soluble in  that  liquid,  as  also  in  ether;  alcohol,  on  the  other  hand,  dis- 
solves it  with  facility.  The  boiling  point  of  this  compound  is  a  little  above 
100° ;  its  vapor  is  colorless,  spontaneously  inflammable  in  the  air,  and  has 
a  density  of  4-56.  Dilute  nitric  acid  dissolves  the  chloride  without  change  ; 
with  the  concentrated  acid,  ignition  and  explosion  occur.  Cacodyl  chloride 
combines  with  cuprous  chloride,  forming  a  white,  insoluble,  crystalline 
double  salt,  containing  As2(CH3)4Cl2  .  Cu'yCljj  also  with  cacodyl  oxide. 

Cacodyl  chloride  forms  a  hydrate  which  is  thick,  viscid,  and  readily  de- 
hydrated by  calcium  chloride. 

CACODYLTRICHLORIDE,  Asv(CH3)2Cl3,  is  produced  by  the  action  of  phos- 
phorus pentachloride  on  cacodylic  acid : 

As*(CHs)20"(OH)  +  2PC15  =  As(CH3)2Cl3  +  2POC13  +  HC1. 

Also  by  the  action  of  chlorine  gas  on  the  monochloride.  Prepared  by  the 
first  method,  it  forms  splendid  large  prismatic  crystals,  which  however  are 
very  unstable,  being  instantly  decomposed,  at  temperatures  between  40° 
and  50°  C.  (104-122°  F.),  into  methyl  chloride  and  arsen-monomethyl  chlo- 
ride: 

As^(CH3)2Cl3        =        CH3C1        +        As"'(CH3)Cl2. 

CACODYL  IODIDE,  As(CH3)2T,  is  a  thin,  yellowish  liquid,  of  offensive  odor, 
and  considerable  specific  gravity,  prepared  by  distilling  alkarsin  with 


CACODYL.  765 

strong  solution  of  hydriodic  acid.  A  yellow  crystalline  substance  is  formed 
at  the  same  time,  which  is  an  oxyiodide.  Cacodyl  bromide  and  fluoride  have 
also  been  obtained. 

CACODYL  CYANIDE,  As(CH3)2CN,  is  easily  formed  by  distilling  alkarsin 
with  strong  hydrocyanic  acid,  or  mercuric  cyanide.  Above  32-7°  C.  (90° 
F.),  it  is  a  colorless,  ethereal  liquid,  but  below  that  temperature  it  crys- 
tallizes in  colorless  four-sided  prisms,  of  beautiful  diamond  lustre.  It  boils 
at  about  140°  C.  (284°  F.),  and  is  but  slightly  soluble  in  water.  It  requires 
to  be  heated  before  inflammation  occurs.  The  vapor  of  this  substance  is 
most  fearfully  poisonous:  the  atmosphere  of  a  room  is  said  to  be  so  far 
contaminated  by  the  evaporation  of  a  few  grains  of  it  as  to  cause  instan- 
taneous numbness  of  the  hands  and  feet,  vertigo,  and  even  unconscious- 
ness. 

CACODYL  OXIDE,  As///2(CH3)40//. —  This  compound  is  formed  by  the  slow 
oxidation  of  cacodyl.  When  air  is  allowed  access  to  an  aqueous  solution 
of  alkarsin,  so  slowly  that  no  sensible  rise  of  temperature  follows,  that 
body  is  gradually  converted  into  a  thick,  syrupy  liquid,  full  of  crystals  of 
cacodylic  acid.  On  dissolving  this  mass  in  water,  and  distilling,  water  hav- 
ing the  odor  of  alkarsin  passes  over,  and  afterward  an  oily  liquid,  which 
is  the  cacodyl  oxide.  Impure  cacodylic  acid  remains  in  the  retort. 

Cacodyl  oxide,  purified  by  rectification  from  caustic  baryta,  is  a  color- 
less, oily  liquid,  having  a  pungent  odor,  sparingly  soluble  in  water,  and 
boiling  at  120°  C.  (248°  F.),  strongly  resembling  alkarsin  in  odor,  in  its 
relations  to  solvents,  and  in  the  greater  number  of  its  reactions;  but  it 
neither  fumes  in  the  air,  nor  takes  fire  at  common  temperatures :  its  vapor 
mixed  with  air,  and  heated  to  about  88°  C.  (190°  F.),  explodes  with  vio- 
lence. It  dissolves  in  hydrochloric,  hydrobromic,  and  hydriodic  acids, 
forming  chloride,  bromide,  and  iodide  of  cacodyl. 

Cacodyl  dioxide,  As2(CH3)402,  is  the  thick  syrupy  liquid  produced  by  the 
slow  oxidation  of  cacodyl  or  of  alkarsin.  It  is  decomposed  by  water,  and 
then  yields  a  distillate  of  cacodyl  monoxide,  with  a  residue  of  cacodylic 
acid: 

2As2(CH3)402    -f    H20    =    As2(CH3)40   -f-   2As(CH3)20(OH.) 

CACODYLIC  ACID,  AsT(CH?)20"(OH),  also  called  Alkargcn.  —  This  is  the 
ultimate  product  of  the  action  of  oxygen  at  a  low  temperature  upon  caco- 
dyl or  alkarsin  in  presence  of  water:  it  is  best  prepared  by  adding  mer- 
curic oxide  to  alkarsin,  covered  with  a  layer  of  water  and  artificially 
cooled,  until  the  mixture  loses  all  odor,  and  afterward  decomposing  any 
mercuric  cacodylate  that  may  have  been  formed,  by  the  cautious  addition 
of  more  alkarsin.  The  liquid  yields,  by  evaporation  to  dryness  and  solu- 
tion in  alcohol,  crystals  of  cacodylic  acid.  The  sulphide  and  other  com- 
pounds of  cacodyl  yield  the  same  substance  on  exposure  to  air.  Cacodylic 
acid  forms  brilliant,  colorless,  brittle  crystals,  which  have  the  form  of  a 
modified  square  prism :  it  is  permanent  in  dry  air,  but  deliquescent  in  a  moist 
atmosphere.  It  is  not  at  all  poisonous,  though  it  contains  more  than  50  per 
cent,  of  arsenic.  It  is  very  soluble  in  water  and  in  alcohol,  but  not  in  ether: 
the  solution  has  an  acid  reaction.  When  mixed  with  alkalies  and  evapo^ 
rated,  it  leaves  a  gummy,  amorphous  mass.  With  the  oxides  of  silver  and 
mercury,  on  the  other  hand,  it  yields  crystallizable  compounds.  It  unites 
with  cacodyl  oxide,  and  forms  a  variety  of  combinations  with  metallic  salts. 
Cacodylic  acid  is  exceedingly  stable:  it  is  not  affected  by  red  fuming  nitric 
acid,  nitromuriatic  acid,  or  even  chromic  acid  in  solution:  it  may  be  boiled 
with  these  substances  without  the  least  change.  It  is  deoxidized,  however, 
by  phosphorous  acid  and  stannous  chloride,  yielding  cacodyl  oxide.  Dry 
hydriodic  acid  gas  decomposes  it,  with  production  of  water,  cacodyl  iodide, 


766  ARSENIC   BASES. 

and  free  iodine.  With  dry  hydrochloric  acid  gas,  or  with  the  concen- 
trated aqueous  acid,  cacodylic  acid  unites  directly,  forming  the  compound 
As  (CH3)202H .  HC1.  But  by  exposing  cacodylic  acid  for  a  long  time  to  a 
stream  of  hydrochloric  acid  gas,  arsen-monomethyl  dichloride  is  obtained,  to- 
gether with  water  and  methyl  chloride : 

As(CH3)202H  -f  3HC1    =   As(CH3)Cl2  +  2H20  -f  CH3C1. 

Phosphorus  pentachloride  converts  cacodylic  acid  into  cacodyl  trichloride 
(p.  764). 

CACODYL  SULPHIDE,  As2(CH3)4S,  is  formed  by  adding  barium  sulphide  to 
crude  cacodyl,  or  by  distilling  barium  sulph-hydrate  with  cacodyl  chloride. 
It  is  a  transparent  liquid  which  re-tains  its  fluidity  at  — 40°,  and  boils  at  a 
temperature  considerably  above  100°. 

Cacodyl  disulphide,  As2(CH3)4S2,  is  formed  by  the  action  of  sulphur  on  ca- 
codyl or  the  monosulphide,  or  by  treating  cacodylic  acid  with  sulphuretted 
hydrogen  in  a  vessel  externally  cooled.  It  separates  from  the  solution  in 
large  rhombic  crystals.  The  alcoholic  solution  of  this  compound  yields 
with  various  metallic  solutions,  precipitates  consisting  of  salts  of  sulphoca- 
codylic  acid,  As(CH3)2S2H,  analogous  to  cacodylic  acid.  The  lead-salt,  As2 
(CH3)4S4Pb//,  forms  small  white  crystals. 

Arsenmonomethyl,  As(CH3).  —  This  radical,  which  is  not  known  in  the 
separate  state,  is  either  bivalent  or  quadrivalent.  Its  dichloride,  Asx// 
(CH3)C12,  is  produced  either  by  the  decomposition  of  cacodyl  trichloride 
by  heat:  As(CH3)2Cl3^As(CH3)Cl2-f  CH3C1;  or  by  the  prolonged  action  of 
hydrochloric  acid  on  cacodylic  acid  (p.  765).  It  is  a  colorless,  heavy,  mo- 
bile liquid,  having  a  strong  reducing  power ;  boils  at  133°  C.  (271°  F.).  Its 
vapor  exerts  a  most  violent  action  on  the  mucous  membranes ;  on  smelling 
it,  the  eyes,  nose,  and  whole  face  swell  up,  and  a  peculiar  lancinating  pain 
is  felt,  extending  down  to  the  throat.  The  tetrachloride,  Asv(CH3)Cl4,  is  ob- 
tained in  large  crystals  by  passing  chlorine  over  a  mixture  of  the  dichlo- 
ride and  carbon  bisulphide  cooled  to  — 10°.  It  is  very  unstable,  decom- 
posing even  near  0°  into  methyl  chloride  and  arsenious  chloride,  AsCl3. 
There  is  also  a  chlorobromide,  As(CH3)ClBr,  and  a  di-iodide,  As(CH3)I2. 

The  oxide,  As(CH3)0,  obtained  by  decomposing  the  dichloride  with  potas- 
sium carbonate,  forms  large  cubical  crystals,  soluble  in  water,  alcohol,  and 
ether,  and  resolved  by  distillation  with  potash  into  arsenious  oxide  and 
cacodyl  oxide :  4As(CH3)0=:As203+  As2(CH3)40. 

Arsenmethylic  Acid,  As*(CHs)0"(OH)a,  is  obtained  as  a  barium-salt  by 
decomposing  arsenmethyl  dichloride  with  a  slight  excess  of  silver-oxide ; 
and  this  salt,  decomposed  by  sulphuric  acid,  yields  the  acid  which  remains 
on  evaporation  in  the  form  of  a  laminated  mass.  It  is  bibasic. 

Arsenmethyl  sulphide,  As(CH3)S,  is  obtained  as  a  white  mass  by  passing 
hydrogen  sulphide  over  the  dichloride. 

On  comparing  the  combining  or  equivalent  values  of  the  several  arse- 
nides of  methyl,  it  will  be  seen  that  they  all  unite  with  elementary  bodies 
and  compound  radicals,  in  such  proportion  as  to  form  compounds  in  which 
the  arsenic  is  either  trivalent  or  quinquivalent,  the  last-mentioned  com- 
pounds being  by  far  the  most  stable.  Thus  : 

Arsenmonomethyl,  As(CH3),  is  bi-  and  quadri-valent,  forming  the  chlo- 
rides As'"(CH8)Cl2  and  Asv(CH3)Cl4. 

Arsendimethyl,  As(CH3^2,  is  mono-  and  tri-valent,  forming  the  chlorides 
As'"(CH,)2Cl  and  As*(CH3)2Cls. 

Arsentrimethyl,  As(CIL),,  is  bivalent  only,  and  forms  the  chloride  Asv 
(CH3)3C12. 

Arsenmethylium,  or  Tetramethylarsonium,  As(CH«),,  is  univalent,  form- 
ing the  chloride  Asv(CH3)4Cl. 


DIATOMIC    PHOSPHORUS   AND   ARSENIC  BASES.       767 

Bismethyl  or  Triethylbismuthine,  Bi(C2H5)3,  analogous  in  composition  to 
triethj&lstibine  and  triethylarsiae,  is  formed  by  the  action  of  ethyl  iodide 
on  an  alloy  of  bismuth  and  potassium,  and  is  extracted  from  the  residue 
by  ether.  It  is  a  yellow  liquid  of  specific  gravity  1-82,  has  a  most  nau- 
seous odor,  and  emits  vapors  which  take  fire  in  contact  with  the  air.  It 
unites  with  oxygen,  chlorine,  bromine,  iodine,  and  nitric  acid. 

Borethyl,  B(C2H5)3. — Dr.  Frankland  has  obtained  this  compound  by 
treating  boric  ether  with  zinc-ethyl:  it  is  a  colorless  mobile  liquid  having 
a  pungent  odor,  irritating  the  eyes,  of  sp.  gr.  0-696,  and  boiling  at  95°  C. 
(203°  F.).  Borethyl  is  insoluble  in  water,  but  very  slowly  decomposed 
when  left  in  prolonged  contact  with  it.  When  exposed  to  the  air  it  is  spon- 
taneously inflamed,  burning  with  a  beautiful  green  and  somewhat  smoky 
flame.  It  combines  with  ammonia,  forming  the  compound  NH3.B(C2H5)3. 
By  the  gradual  action  of  dry  air,  and,  ultimately,  of  dry  oxygen,  borethyl 
is  converted  into  an  oxygen-compound  of  the  formula  B(C2H5)302. 


DIATOMIC  BASES  OF  THE  PHOSPHORUS  AND  ARSENIC  SERIES. 

The  action  of  ethene  bromide  on  triethylphosphine  gives  rise  to  the  for- 
mation of  two  crystalline  bromides,  according  to  the  proportions  in  which 
the  substances  are  brought  in  contact.  These  bromides  are  C8H19PBr2=r 
C6H,5P+C2H4Br2  and  C,4H34P2Br2r=  2C6H15P-f  C2H4Br2.  The  first  of  these 
compounds  is  the  bromide  of  a  phosphonium  in  which  3  atoms  of  hydro- 
gen are  replaced  by  ethyl  and  one  atom  by  the  univalent  radical  bromethyl, 
C2H4Br,  thus  [(C2H4Br)(C2H5)3P]Br.  Half  the  bromine  in  this  salt  is  un- 
affected by  the  action  of  silver-salts;  it  may  accordingly  be  designated  as 
bromide  of  bromethyl-tricthyl-phosphonium.  Numerous  salts  of  this  compound 
are  known,  but  the  free  base  cannot  be  obtained,  since  silver  oxide  elimi- 
nates the  latent  bromine,  giving  rise  to  the  formation  of  a  base  containing 
[(C2H50)(C2H5)3P]OH.  The  second  compound  is  the  dibromide  of  ethene- 
hexethyl-diphosphonium,  [(C2H4)"(C2H?)6P2]"Br2.  This  radical,  which  cor- 
responds to  2  equivalents  of  ammonium,  2NH4  =  N2Hg,  forms  a  series  of 
very  stable  and  beautiful  salts,  especially  an  iodide  which  is  difficultly 
soluble  in  water.  In  all  these  salts  the  base,  which  is  composed  of  1  mole- 
cule of  ethene,  6  molecules  of  ethyl,  and  2  atoms  of  phosphorus,  is  united 
with  2  molecules  of  univalent-acid  radical;  the  platinum-salt  contains 
(C2H4)//(C2H5)6P2Br2 .  PtivCl4.  The  free,  very  caustic,  and  stable  base  has 
the  composition  [(C2H4)"(C2EI5)6P2]"(OH)2. 

The  dibromide  of  ethene-hexethyl-diphosphonium  may  be  formed  by  the 
action  of  triethylphosphine  upon  the  brominated  bromide  which  has  been 
mentioned  as  the  first  product  of  the  action  of  ethene  dibromide  upon  tri- 
ethylphosphine :  C3H19PBr2+C6H15P=C,4H34P2Br2.  If  the  triethylphosphine 
be  replaced  in  this  process  by  ammonia  or  by  monamines  in  general,  or  by 
monarsines,  an  almost  unlimited  series  of  diatomic  salts  may  be  formed, 
in  which  phosphorus  and  nitrogen  or  phosphorus  and  arsenic  are  associated. 

Thus  the  action  of  ammonia,  of  ethylamine,  and  of  triethylarsine,  gives 
rise  respectively  to  the  fpllowing  compounds ; 

Dibromide  of  Ethene-triethyl-  1  ,,„  „  y,(r  H  >,  H  PNy/Br 
phosphammonium  .  .  /  A^J  (b^gj^^  15r2. 

Dibromide  of  Ethene-tetrethyl)  rfr  w  v/,p  „  .  w  pxn//iu. 

phosphammonium  .  .  [(C2H4)"(C2H6)4H2PN]"Br2. 

Dibromide  of  Ethene-hexethyl- 
phospharsonium         .        . 


768  ZINC-ETHYL. 

Treated  with  silver  oxide,  these  bromides  yield  the  very  caustic  diatomic 
bases  — 

[(C!H4)"(C2H6)3H3PN]-(OH), 


The  arsenic  bases,  when  submitted  to  the  action  of  ethene  dibromide, 
give  rise  to  perfectly  analogous  results.  The  limits  of  this  Manual  will  not 
permit  us  to  examine  these  remarkable  compounds  in  detail. 


IV.  —  Compounds  of  Alcohol- radicals  with  Bivalent  and  Quadrivalent 
Metals  and  Metalloids. 

The  bodies  of  this  group  which  contain  bivalent  elements,  such  as  zinc, 
are  saturated  compounds,  not  capable  of  uniting  directly  with  chlorine,  oxy- 
gen, &c. ;  those  which  contain  quadrivalent  metals,  like  tin,  are  saturated 
or  unsaturated  accordingly  as  they  contain  four  or  only  two  equivalents  of 
alcohol-radicals. 

All  these  compounds  are  frequently  designated  as  organo-metallic  bodies, 
a  term  likewise  including  the  compounds  of  alcohol-radicals  with  arsenic, 
antimony,  and  bismuth.  We  shall  describe  chiefly  the  ethyl  compounds, 
to  which  the  methyl  and  amyl  compounds  are  strictly  analogous. 

Zinc-ethyl  or  Zinc  ethide,  Zn/x(C2H6)2.  —  This  compound,  discovered  by 
Frankland,  is  formed,  together  with  zinc-iodide,  when  ethyl  iodide  is  heated 
with  metallic  zinc  in  a  sealed  glass  tube,  or,  for  larger  quantities,  in  a 
strong  and  well-closed  copper  cylinder :  2C2H5I  -(-  Zn2  =  ZnI2  -j-  Zn(C2H5)2. 
The  two  products  remain  combined  together  in  the  form  of  a  white  crystal- 
line mass,  from  which  the  zinc-ethyl  may  be  separated  by  distillation  in  an 
atmosphere  of  hydrogen.  It  is  a  mobile  and  very  volatile  liquid,  having  a 
disagreeable  odor,  taking  fire  instantly  on  coming  in  contact  with  the  air, 
and  diffusing  white  fumes  of  zinc  oxide.  Water  decomposes  it  violently, 
with  formation  of  zinc  hydrate,  and  evolution  of  ethane  or  ethyl-hydride : 
Zn(C2Hg)2  4-  2H20  =  ZnH202  -f  C2H6.  When  gradually  mixed  with  dry 
oxygen,  it  passes  through  two  stages  of  oxidation,  yielding  first  zinc  ethyl- 

ethylate,    Zn"/S?k,    and   finally   zinc    ethylate,    Zn"(OC2H6)2.      With 

I  UL-jjllg 

iodine  and  other  halogens,  the  reaction  also  takes  place  by  two  stages,  but 
consists  in  the  successive  substitution  of  the  halogen  for  the  ethyl ;  thus : 

Zn(C2H5)2        +         I2         =         C2H5I         +         Zn(C2H5)I, 
and 

Zn(C2H6)I        -f         I2        =         C2H6I         +         ZnI2. 

Zinc  ethide  has  become  a  very  important  reagent  in  organic  chemistry, 
serving  to  effect  the  substitution  of  the  positive  radical  ethyl  for  chlorine, 
iodine,  and  other  negative  elements,  and  thus  enabling  us  to  build  up 
carbon-compounds  from  others  lower  in  the  scale.  Many  examples  of 
these  reactions  have  already  been  given  in  the  chapters  on  alcohols  and 
acids.  In  like  manner  it  serves  for  the  preparation  of  many  other  or- 
gano-metallic bodies.  The  following  equations  exhibit  the  mode  of  forma- 
tion of  mercuric  methide,  stannic  ethide,  and  triethylarsine  by  means  of 
zinc  ethide : 


ALUMINIUM    METHIDE.  769 

Zn"(C2H5)2  +  Hg"Cl2  =  ZnCl2  +  Hg"(C2H5)2 
2Zn"(C2H5)3  -f-  Sn*Cl4  =  2ZnCl2  +  Sn»*(C2H5)4 
3Zn"(C2H5)2  -f-  2As"'Cl3  =  3ZnCl2  +  2As'"(C2H6)3. 

Zinc  Methide,  Zn'^CH^),  is  analogous  in  its  reactions  to  zinc  ethide,  but 
is  still  more  volatile  and  inflammable. 

Potassium  Ethide,  C2H6K,  and  Sodium  Ethide,  C2H5Na,  are  not  known  in 
the  separate  state,  but  only  in  combination  with  zinc-ethyl.  These  mixed 
compounds  are  produced  by  the  action  of  potassium  on  sodium  zinc-ethyl; 
thus: 

3Zn(C2H5)2      +      Na2      =      Zn      -f       2(C2H5)3 

These  compounds  and  their  homologues,  discovered  by  Wanklyn,  have  also 
played  an  important  part  in  chemical  synthesis.  The  production  of  the 
fatty  acids  by  the  combination  of  carbon  dioxide  with  sodium  ethide,  &c. 
has  been  frequently  mentioned. 

Mercuric  Ethide,  Hg//(C2H5)2.  —  This  compound  is  formed,  as  already  ob- 
served, by  the  action  of  mercuric  chloride  on  zinc  ethide,  but  it  is  more 
easily  prepared  by  the  action  of  sodium-amalgam  on  ethyl  iodide  in  presence 
of  acetic  ether  : 

2C2H5I       +       Na2      +       Hg      =    2NaI      +       Hg(C2H5)2. 

The  acetic  ether  takes  no  part  in  the  reaction  ;  nevertheless  its  presence 
appears  to  be  essential. 

Mercuric  ethide  is  a  transparent,  colorless  liquid,  boiling  at  159°.  It 
burns  with  a  smoky  flame,  giving  off  a  large  quantity  of  mercurial  vapor. 
Chlorine,  bromine,  and  iodine  remove  one  equivalent  of  ethyl  from  this  com- 
pound, and  take  its  place,  forming  mercuric  chlorethide,  &c.  ;  thus  : 

Hg(C2H6)2    +     C12     =     C2H5C1    +     Hg(C2H5)Cl. 

A  similar  action  is  exerted  by  acids,  e.  g.,  by  hydrobromic  acid,  the  pro- 
ducts being,  ethane  and  mercuric  bromethide: 


C2H6      +     Hg(C2H5)Br. 

The  chlorethide  or  bromethide  is  converted  by  water  into  mercuric  ethyl- 
"hydrate,  Hgx/(C2H6)(OH).  Mercuric  ethide  serves  for  the  preparation  of 
several  other  organo-metallic  bodies. 

Aluminium  Methide,  A1///(CH3)3,  or  A12(CH3)6.  —  This  compound,  dis- 
covered by  Buckton  and  Odling,*  is  formed  by  heating  mercuric  ethide 
with  aluminium.  It  is  a  mobile  liquid,  which  crystallizes  at  a  little  above 
0°,  and  boils  at  130°  C.  (266°  F.).  At  and  above  220°  C.  (428°  F.)  the  den- 
sity of  its  vapor,  compared  with  that  of  air,  is  2-8,  which  is  near  to  the 
theoretical  density  calculated  for  the  formula  A1(C2H5)3,  namely,  2*5.  This 
seems  to  show  that  the  true  formula  of  the  compound  is  A1(C2H6)3,  and  not 
A12(C2H5)6,  and,  consequently,  that  aluminium  is  a  triad,  not  a  tetrad  (p. 
333).  At  temperatures  near  the  boiling  point,  however,  the  vapor-density 
becomes  4-4,  approximating  to  the  theoretical  density  calculated  for  the 
formula  A12(C2H6)6. 

Aluminium  ethide  resembles  the  methyl  compound.  It  boils  at  194°  C. 
(381°  F.),  and  its  vapor  likewise  exhibits,  at  temperatures  considerably 
above  its  boiling  point,  a  density  nearly  equal  to  that  required  by  the  for- 
mula A1(C3H5)3,  for  a  two-volume  condensation.  -J- 

*  Proceedings  of  the  Royal  Society,  xiv.  19. 

f  The  vapor-density  of  aluminium  chloride,  as  determined  by  Deville,  agrees  with  that  re- 
quired by  the  formula  A12C1C;  but  as  this  compound  has  a  very  high  boiling  point,  it  was  per- 
haps not  heated  sufficiently  to  convert  it  into  a  perfect  gas  (see  page  461). 

65 


770  PLUMBIC   ETHIDE. 

Ethyl  Compounds  of  Tin.  —  Tin  forms  two  ethyl  compounds,  Sn//(C2H5)2 
and  Sniv(C2H5)4,  analogous  to  stannous  and  stannic  chloride ;  also  a  stan- 
noso-stannous  ethide,  Sn2(C2H5)6,  analogous  in  constitution  to  ethane,  C2H6. 
Stannic  ethide  is  a  saturated  compound,  but  the  other  two  are  unsaturated 
bodies,  capable  of  uniting  with  chlorine,  bromine,  oxygen,  and  acid  radi- 
cals, and  being  thereby  converted  into  compounds  of  the  stannic  type. 

STANNOUS  ETHIDE,  Sn//(C2H5)2. — When  ethyl  iodide  and  tinfoil  are 
heated  together  in  a  sealed  glass  tube  to  about  150°  or  180°  C.  (302°-356° 
F.),  stannous  iodethide,  SniT(C2H5)2I2,  is  produced,  crystallizing  in  colorless 
needles.  The  same  compound  is  obtained  when  tin  and  ethyl  iodide  are 
exposed  to  the  rays  of  the  sun  concentrated  by  a  parabolic  reflector.  The 
reaction  is  considerably  facilitated  if  the  tin  be  alloyed  by  one-tenth  of  its 
weight  of  sodium.  This  iodide  is  decomposed  by  sodium  or  zinc,  which 
abstracts  the  iodine  and  leaves  stannous  ethide  in  the  form  of  a  thick,  oily 
liquid,  insoluble  in  water,  and  having  the  sp.  gr.  1-55.  Stannous  ethide 
combines  directly  with  2  atoms  of  chlorine,  iodine,  and  bromine,  forming 
stannic  chlorethide,  Sn'T(C2H5)2Cl2,  &c,  Exposed  to  the  air,  it  absorbs  oxy- 
gen and  is  converted  into  stannous  oxethide,  SniT(C2H6)20,  a  whitish,  taste- 
less, inodorous  powder,  which,  when  treated  with  oxygen-acids,  yields  well 
crystallized  stannous  salts,  such  as  Sniv(C2H6)2(N03)2,  Sniv(C2H5)2S04,  &c. 

STANNOSO-STANNIC  ETHIDE,  Sn2(C2H5)6,  is  always  produced  in  small  quan- 
tity when  stannous  ethide  is  prepared  by  the  methods  above  mentioned. 
It  is  really  obtained  in  the  free  state  by  digesting  an  alloy  of  1  part  of 
sodium  and  5  parts  of  tin  with  ethyl  iodide,  exhausting  the  mass  with  ether, 
evaporating  the  ethereal  solution,  and  exhausting  the  residue  with  alcohol. 
The  stannoso-stannic  ethide,  being  insoluble  in  that  liquid,  then  remains 
behind.  It  is  a  yellow  oil,  boiling  at  380°  C.  (356°  F.),  combining  directly 
with  chlorine,  bromine,  and  iodine  to  form  two  molecules  of  a  stannic  com- 
pound ;  e.  ff.  : 

Sn2(C2H5)6    +     C12    =     2Sn*(C2H5)3Cl; 

Stannic  chloro-triethide. 

also  with  oxygen,  forming  distannic  oxy-hexethide,  Sniv2(C2H5)60.  This 
oxide  is,  however,  best  obtained  by  distilling  stannous  oxy-diethide,  SniT 
(C2Hs)20  (above  described),  with  potash.  It  is  an  oily  liquid,  soluble  in 
alcohol,  ether,  and  water ;  the  aqueous  solution  has  a  strong  alkaline  reac- 
tion. It  is  easily  acted  upon  by  oxygen-acids,  yielding  the  corresponding 
sulphate,  Sn2(C2H5)6S04,  &o. 

STANNIC  ETHIDE,  Sn*(C2H5)4,  is  produced  by  the  action  of  zinc  ethide  on 
stannic  chloride ;  also  by  the  distillation  of  stannous  ethide,  2Sn(C2H5)2  = 
Sn  -(-  Sn(C2H5)4.  It  is  a  colorless,  nearly  odorless  liquid,  of  sp.  gr.  1-19, 
boiling  at  181°  C.  (358°  F.),  and  very  inflammable,  burning  with  a  highly 
luminous  flame.  When  treated  with  chlorine,  bromine,  &c.,  or  with  acids, 
it  forms  substitution-products :  thus,  with  iodine,  it  splits  up  into  ethyl 
iodide  and  stannic  iodotriethide  : 

Sn(C2H5)4     +     I2    =     C2H5I     +     Sn(C2H5)3I. 

With  strong  hydrochloric  acid,  it  yields  ethane  and  stannic  chlorotriethide, 
Sn(C2H5)4  +  HC1  =  C2H6  +  Sn(C2H5)3Cl. 

Plumbic  Ethide,  Pb(C2H5)4,  is  produced  by  the  action  of  plumbic  chloride 
on  zinc  ethide : 

2Zn(C2H5)2  +  2PbCl2  =  2ZnCl2  +  Pb  -f  Pb(C2H6)4. 

It  is  a  colorless  limpid  liquid,  soluble  in  ether  but  not  in  water.  It  is  not 
acted  upon  by  oxygen  at  ordinary  temperatures ;  but  chlorine,  bromine, 


TELLURETHYL.  771 

and  iodine  act  violently  upon  it,  in  the  same  manner  as  on  stannic  ethide, 
forming  plumbic  chloro-triethide,  Pb(C2H6)3Cl,  &c.  Plumbic  ethide  is 
interesting,  as  affording  a  proof  that  lead  is  really  a  tetrad  (p.  398.) 

Tellurethyl,  Te"(C2H5)2,  is  obtained  by  distilling  potassium  telluride 
with  potassium  ethylsulphate.  It  is  a  heavy,  oily  liquid  of  yellowish-red 
color,  very  inflammable,  and  having  a  most  insufferable  odor.  It  acts  as  a 
bivalent  radical,  uniting  directly  with  chlorine,  bromine,  oxygen,  &c.,  to 
form  compounds  in  which  the  tellurium  enters  as  a  tetrad,  e.  g.,  Teiv(C2H6)2 
C12,  Te»T(C2H5)30",  &c.  The  nitrate  Te(C2H5)2(N03)2,  is  obtained  by  treat- 
ing tellethuryl  with  nitric  acid ;  the  other  salts  by  double  decomposition ; 
the  chloride,  for  example,  settles  down,  as  a  heavy  oil,  on  adding  hydro- 
chloric acid  to  a  solution  of  the  nitrate.  The  oxide  is  best  prepared  by 
treating  the  chloride  with  water  and  silver  oxide.  It  dissolves  in  water, 
forming  a  slightly  alkaline  liquid. 

Telluro-methyl,  Te(CH3)2,  and  tdluramyl,  Te(C6Hu)2,  are  similar  in  their 
properties  to  tellurethyl.  The  corresponding  selenium  compounds  have  like- 
wise been  obtained. 

There  are  also  compounds  of  sulphur  with  alcohol-radicals  in  which  the 
sulphur  plays  the  part  of  a  quadrivalent  element,  viz.,  the  triethylsulphurous 
compounds,  already  described  (p.  530). — Sulphurous  iodo-1riethide,  Siv(C2H6>3I, 
for  example,  is  produced  by  combination  of  ethyl  monosulphide,  S(C2H5)2, 
with  ethyl  iodide,  C2H5I. 

Other  compounds,  in  which  the  sulphur  may  be  regarded  as  a  hexad, 
are  obtained  by  combining  ethyl  sulphide  and  ethene  sulphide  with  ethene 
dibromide:  thus  sulphuric  diethene-dibromide,  Siv(C2H4)//2Br.J,  is  formed  by 
combination  of  S(C2H4)  with  C2H4Br2,  and  sulphuric  diethyl-ethene-dibromide, 
Svi(C2H5)2(C2H4)''Br2,  in  like  manner  by  combination  of  S(C2H6)2  with 
C2H4Bra. 


AMIDES. 

WE  have  had  frequent  occasion  to  speak  of  these  compounds,  as  derived 
from  ammonium-salts  by  abstraction  of  water,  or  from  acids  by  substitu- 
tion of  amidogen,  NH2,  for  hydroxyl,  OH,  or  from  one  or  more  molecules 
of  ammonia  by  substitution  of  acid-radicals  for  hydrogen.  They  are 
divided  (like  amines)  into  monamides,  diamides,  and  triamides,  each  of 
which  groups  is  further  subdivided  into  primary,  secondary,  and  tertiary 
amides,  accordingly  as  one-third,  two-thirds,  or  the  whole  of  the  hydrogen 
is  replaced  by  acid-radicals.  If  the  hydrogen  is  replaced  partly  by  acid- 
radicals,  and  partly  by  alcohol-radicals,  the  compound  is  called  an  alkala- 
mide\  for  example,  ethylacetamide,  NH(C2H5)(C2H30) ;  ethyldiacetamide 
N(C2H5)(C2H30)2. 


AMIDES  DERIVED  FROM  MONATOMIC  ACIDS. 

A  monatomic  acid  yields  but  one  primary  amide,  which  may  be  formed : 
1.  From  its  ammonium-salt  by  abstraction  of  a  molecule  of  water,  under 
the  influence  of  heat ;  thus : 

C2H3(NH4)02    -    H20    =    C2H5NO    =      |    '         = 
Ammonium  Acetamide.          CONH2 

acetate. 

These  amides  are  also  produced:    2.  By  the  action  of  ammonia  on  acid 
chlorides ;  e.  g. : 

C2H3OC1        4-        NH3        =        HC1        -f        NH2(C2H30). 

This  method  is  especially  adapted  to  the  preparation  of  those  amides  which 
are  insoluble  in  water. 

3.  By  the  action  of  ammonia  on  compound  ethers : 

C2H3O.OC2H5     4-      NH3     =      HOC2H5     +      NH2(C2H30). 
Ethyl  acetate.  Ethyl  alcohol.  Acetamide. 

Acetamide,  which  may  be  regarded  as  a  type  of  primary  monamides,  is  a 
white  crystalline  solid  melting  at  78°  C.  (172°  P.),  and  boiling  at  221°  or 
222°  C.  (480°  F.).  When  heated  with  acids  or  with  alkalies,  it  takes  up 
water  and  is  converted  into  acetic  acid  and  ammonia.  Distilled  with  phos- 
phoric oxide,  it  gives  up  water  and  is  converted  into  acetonitrile  or  methyl 
cyanide,  C2H5N02  —  H20  —  C2H3N.  Heated  in  a  stream  of  dry  hydrochlo- 
ric acid,  it  yields  diacetamide,  together  with  other  products : 

2NH2(C2H30)       +      HC1      =      NH4C1      -f       NH(C2H30)2. 

Acetamide  acts  both  as  a  base  and  as  an  acid,  combining  with  hydrochloric 
and  with  nitric  acid,  and  likewise  forming  salts  in  which  one  atom  of  its 
hydrogen  is  replaced  by  a  metal :  silver-acetamide,  C2H4NAgO,  for  example, 
is  obtained  in  crystalline  scales  by  saturating  an  aqueous  solution  of  ace- 
tamide  with  silver  oxide. 

772 


AMIDES.  773 

Benzamide,  C7H7NO  =  NH2(CrH60),  is  produced  by  methods  similar  to 
those  above  given  for  the  formation  of  acetamide ;  also  by  oxidizing  hip- 
puric  acid  with  lead  dioxide  : 

C9H9N08      +       02      =      C7H7NC1      -f      2C02      +       H20 

Benzamide  is  a  crystalline  substance  nearly  insoluble  in  cold  water,  easily 
soluble  in  boiling  water,  also  in  alcohol  and  ether;  it  melts  at  1 15°  C.  (239°  F. ), 
and  volatilizes  undecomposed  between  286°  and  290°  C.  (547°-554°  F.).  Its 
reactions  are  for  the  most  part  similar  to  those  of  acetamide.  Heated  with 
benzoic  oxide  or  chloride,  it  yields  benzonitrile  and  benzoic  acid : 

C7H7NO       +       (C7H50),0      =        C7H?N       +       2C7H602 
Benzamide.          Benzoic  oxide.         Benzonitrile.      Benzoic  acid. 

C7H7NO       -f       C?H5OC1        =        C7HgN       -f     C7H6024-HC1 
Benzamide.       Benzoic  chloride.        Benzonitrile.  Benzoic  acid. 

Heated  with  fuming  hydrochloric  acid,  it  forms  hydrochloride  of  benz- 
amide,  C7H7NO  .  HC1,  which  separates  on  cooling  in  long  aggregated  prisms. 
Its  aqueous  solution  dissolves  mercuric  oxide,  forming  benzomercuramide, 
N2H2(C7H50)2Hg". 

Secondary  monamides  are  those  in  which  two  atoms  of  hydrogen  in  a  mole- 
cule of  ammonia  are  replaced  by  two  univalent  or  one  bivalent  acid-radi- 
cal, or  by  one  acid-radical  and  one  alcohol-radical.  Those  containing  only 
univalent  radicals  are  formed  by  the  action  of  dry  hydrochloric  acid  gaa 
on  primary  monamides  at  a  high  temperature  ;  e.  g. : 

2NH2(C2H30)       -f       HC1      =      NH4C1       +      NH(C2H30)2 
Acetamide.  Diacetamide. 

Those  containing  bivalent  acid-radicals  are  called  imides  ;  e.  g  ,  succinimides, 
NH(C4H402)".  They  are  derived  from  bibasic  acids,  and  will  be  noticed 
farther  on. 

Secondary  monamides  (alkalamides}  containing  an  acid-radical  and  an 
alcohol-radical,  are  formed  by  processes  similar  to  those  .above  given  for 
.the  formation  of  the  primary  monamides,  substituting  amines  for  ammo- 
nia; thus: 

NH2(C2H6)     -f     C2H3OC1  =    HC1          +  NH(C2H5)(C2H30) 

Ethylamine.  Acetic  Ethyl-acetamide. 

chloride. 

NH2(C2H5)     -f-     C2HS0(OC2H6)    =     HOC2H5  -f  NH(C2H6)(C2H30) 
Ethylamine.  Ethyl  acetate.  Alcohol.         Ethyl-acetamide. 

They  are  crystalline,  and  for  the  most  part  do  not  combine  with  acids. 
When  boiled  with  acids  or  alkalies,  they  take  up  water  and  regenerate 
their  acid  and  primary  amine ;  thus  : 

NH(C6H5)(C2H30)     +     HOH    =     C2H30(OH)     +     NH2(C6H6) 
Phenyl-acetamide.  Acetic  acid.  Aniline. 

Tertiary  monamides  are  those  in  which  the  whole  of  the  hydrogen  in  one 
molecule  of  ammonia  is  replaced  by  acid-radicals  or  by  acid-  and  alcohol- 
radicals.  Those  of  the  latter  kind,  called  tertiary  alkalamides,  are  produced 
by  the  action  of  acid  chlorides  on  secondary  alkalamides : 

NH(C6H5)(C7H60)     +     C7H5OC1    =     HC1    -f     N(C6H5)(C7H50)2 
Phenyl-benzamide.  Bonzoyl  Phenyl-dibenzamide. 

chloride. 
65* 


774:  AMIDES. 

Or  by  the  action  of  monatomic  acid  oxides  on  cyanic  ethers ;  e.  g.  : 

(C2H30)20    +     N(CO)"(C2H6)     =     C02    +     N(C2H5)(C2H30)2 
Acetic  oxide.  Ethyl  cyanate.  Ethyl-diacetamide. 


AMIDES  DERIVED  FROM  DIATOMIC  AND  MONOBASIC  ACIDS. 

Acids  of  this  group  may  give  rise  to  two  monamides,  both  formed  by 
substitution  of  one  equivalent  of  NH2  for  OH,  and  therefore  having  the 
same  composition.  They  are  however  isomeric,  not  identical,  the  one 
formed  by  replacement  of  the  alcoholic  hydroxyl  being  acid,  while  the 
other,  formed  by  replacement  of  the  basic  hydroxyl,  is  neutral.  The  acid 
amides  thus  formed  are  called  amic  acids.  Glycollic  acid,  for  example, 
yields  glycollamic  acid  and  glycollamide,  both  containing  C2H6N02 : 

CH2OH  CH2NH2  CH2OH 

COOH  COOH  CONH2 

Glycollic  Glycollamic  Glycollamide. 

acid.  acid. 

These  amic  acids  and  amides  are  sometimes  represented  as  derived  from  a 
molecule  of  ammonia  and  a  molecule  of  water,  bound  together  by  the  sub- 
stitution of  a  diatomic  acid-radical  for  two  atoms  of  hydrogen;  thus: 


Type.  Glycollamic  acid. 

The  amic  acids  of  this  group  are  identical  with  the  amidated  acids  de- 
rived from  the  corresponding  monatomic  acids,  CnH2n02,  by  substitution  of 
amidogen  for  hydrogen  ;  thus  glycollamic  acid  is  identical  with  amidacetic 
acid  ;  lactamic  with  amidopropionic  ;  leucamic  with  amidocaproic  acid;  for 
example : 

CH3  CH2(NH2)  CH2(OH) 

COOH  COOH  COOH 

Acetic  acid.  Amidacetic  or  Glycollic  acid. 

Glycollamic  acid. 

These  amic  acids  are  formed,  as  already  observed,  by  the  action  of  am- 
monia on  the  monochlorinated  or  monobrominated  derivatives  of  the  fatty 
acids;  the  corresponding  neutral  amides  are  produced  by  the  action  of 
ammonia,  in  the  gaseous  state  or  in  alcoholic  solution,  on  the  corresponding 
oxides  or  anhydrides,  or  on  the  ethylic  ethers  of  glycollic  and  lactic  acids ; 
thus: 

C3H,02        +        NHS        =        C3H7N02 
Lactide.  Lactamide. 

C2H4(OH)  C2H4OH 

4-  NH2H     =        HOC2H6      +        I 
CO(OC2H5)  CONH2 

Ethyl  lactate.  Alcohol.  Lactamide. 

Leucamide,  the  neutral  ether  of  leucic  acid,  is  not  known. 

The  amic  acids  of  this  series  possess  basic  as  well  as  acid  properties,  and 
are  therefore  often  designated  by  names  ending  in  ine,  the  ordinary  ter- 


AMIDES.  775 

ruination  for  organic  bases,  glygollamic  acid  being  designated  as  glycocine, 
lactamic  acid  as  alanine,  leucamic  acid  as  leucine  (pp.  614,  615,  620). 

Amidobenzoic  acid,  C7H6(NH2)02,  or  C6H4(NH?) .  C02H,  produced  from 
nitro-benzoic  acid,  C7H4(N02)02,  by  the  action  of  hydrogen  sulphide,  may 
also  be  regarded  as  oxy-benzamic  acid,  derived  from  oxy-benzoic  acid,  C6H4 
(OH)  .  C02H,  by  substitution  of  NH2  for  OH. 

Diamidobenzoic  acid,  C7H4(NH2)202,  formed  in  like  manner  from  dinitro- 
benzoic  acid,  may  also  be  viewed  as  dioxybenzamic  acid,  derived  from  a  hy- 
pothetical dioxybenzoic  acid,  C6H3(OH)2.  C02H  ;  but  according  to  the  mode 
of  formation  of  these  acids,  they  are  more  conveniently  regarded  as  deriva- 
tives of  benzoic  acid.  Similar  remarks  apply  to  the  amidated  acids  derived 
from  the  homologues  of  benzoic  acid. 


AMIDES  DERIVED  FROM  DIATOMIC  AND  BIBASIC  ACIDS. 

Each  acid  of  this  group  may  give  rise  to  three  amides:  viz.,  1.  An  odd, 
amide,  or  amic  acid,  formed  from  the  acid  ammonium-salt  by  abstraction  of 
one  molecule  of  water.  —  2.  A  neutral  monamide  or  imide,  formed  from  the 
acid  ammonium-salt  by  abstraction  of  two  molecules  of  water.  — 3.  A  neu- 
tral diainide,  derived  from  the  neutral  ammonium-salt  by  abstraction  of  two 
molecules  of  water.  Thus  from  succinic  acid,  (C4H402)X/(OH)2  are  derived : 

H2 

C4H5(NH4)04  —  H20  =  C4H7N03  =  (C4H402)"(NHa)(OH)  =  (C4H4Oa)" 
Acid  ammonium  Succinamic  H 

succinate.  acid. 

CA(NH4)04-2H20=C4H5N02=(C4H402)"(NH)"         =  (C4H4Of)"  \  N 
Acid  salt.  Succinimide.  H  / 

C4H4(NH4)204-  2H10=C4H8N10,=(C  ,H402)^(NH2)2         =  (C4H40,)" 
Neutral  salt.  Succinamide.  H4 

The  amic  acids  of  this  group  are  produced: 

1.  By  the  action  of  heat  on  the  acid  ammonium-salts  of  the  correspond- 
ing acids. 

2.  By  the  action  of  aqueous  ammonia  on  the  neutral  ethers  of  bibasic 
acids ;  e.  g. : 

(C202)"(OC2H5)2  +  NH3  -f  H(OH)  =  2H(OC2H6)  -f  (C202)"(NH2)(OH) 
Ethyl  oxalate.  Alcohol.  Oxamic  acid. 

3.  By  boiling  imides  with   ammonia,  under  which  circumstances  they 
take  up  a  molecule  of  water  and  are  converted  into  amic  acids ;  thus  suc- 
cinimide,  C4H5N02,  with  H20  forms  succinamic  acid,  C4H7N03. 

The  typic  or  extra-radical  hydrogen  in  these  amides  may  also  be  replaced 
by  alcoholic  or  by  acid  radicals,  thereby  producing  alkalamides,  secondary 
and  tertiary  diamides,  &c.  The  mode  of  producing  such  compounds  may 
be  understood  from  the  following  equations : 

(C2Oa)"(ONH8CH,)OH    —    H20      =        (CaOa)"NH(CHs) .  (OH) 
Acid  methylamino-  Methyloxamic  acid, 

nium  oxalate. 

(C4H40S)"0          +  •   NH2(C6H5)       =       2H20  .+  N(C8H6)(C4H408)" 

Succinic  Aniline.  Phenylsuccin- 

oxide.  imide. 

(CA)"(OC,H6)S  +      2NII2(CH3)      =      2H(OC2H5)    +  N,H,(Ca02)"(CIT3)a 
Ethyl  oxalate.  Methylamine.          Ethyl  alcohol.      Dimethyl-oxamidc. 


776  AMIDES. 

(CO)C12  +    2NH2(C6H5)      =      2HC1        +      N2H2(CO)"(C6H6), 

Carbonyl  Aniline.  Diphenyl-carbonide. 

chloride. 

2N(C4H402)"Ag    +     (C4H402)"C12  =      2AgCl      +         N2(C4H402)"3 
Argent  osuccin-  Succinyl  Tnsuccmamide. 

imide.  chloride. 

Amides  of  Carbamic  Acid.  —  Carbonic  acid,  (CO)"(NH2)(OH),  is  not  known 
in  the  free  state,  that  is,  as  a  hydrogen-salt,  but  its  ammonium-salt,  (CO)" 
(NH2)(ONH4),  is  produced,  as  already  noticed  (p.  314),  by  the  direct  com- 
bination of  carbon  dioxide  and  ammonia-gas.  This  salt  is  easily  obtained 
pure  and  in  large  quantity  by  passing  the  two  gases,  both  perfectly  dry, 
into  cold  absolute  alcohol,  separating  the  copious  crystalline  precipitate  by 
filtration  from  the  greater  part  of  the  liquid,  and  heating  it  with  absolute 
alcohol  in  a  sealed  tube  to  100°,  or  above.*  The  liquid,  on  cooling,  de- 
posits ammonium  carbamate  in  large  crystalline  laminae.  This  salt,  if  per- 
fectly dried  over  oil  of  vitriol,  and  then  heated  in  a  sealed  tube  to  130°-140° 
C.  (266°-284°  F.),  splits  up  into  ammonium  carbonate  and  urea,  one  mole- 
cule of  it  giving  up  a  molecule  of  water  to  another: 

2CN2Hg02          =          CN2H40          -f          CN2H803 
Ammonium  Urea.  Ammonium 

carbamate.  carbonate. 

Hence  Kolbe  concludes  that  urea  is  the  amide  of  carbamic  acid,  not  the 
amide  of  carbonic  acid ;  but  it  is  not  easy  to  see  in  what  the  supposed  dif- 
ference consists;  for  carbonic  acid  being  (CO)"(OH)(OH),  and  carbamic 
acid,  (CO)//(NH2)(OH),  the  amide  of  the  latter  must  be  identical  with  the 
diamide  of  the  former.  It  appears,  also,  from  the  observations  of  Basa- 
roff,  that  ordinary  commercial  ammonium  carbonate,  when  treated  in  the 
manner  just  described,  likewise  yields  urea.  On  the  other  hand,  the  ex- 
periments of  Wanklyn  and  Gamgee,  already  quoted  (p.  722),  seem  to  show 
that  urea  is  essentially  different  from  carbamide,  f 

CARBAMIC  ETHERS.  —  Carbamic  acid  forms  acid  and  neutral  ethers,  ac- 
cordingly as  an  atom  of  hydrogen  in  the  group  NH2  or  OH  is  replaced  by 
an  alcohol-radical. 

Ethylcarbamic  acid,  (CO)"  .  NH(C2H6)  .  OH,  is  not  known  in  the  free 
state,  but  its  ethylammonium-salt,  (CO)" .  NH(C2H5)  .  ONH3(C2H6),  is  pro- 
duced, as  a  snow-white  powder,  by  passing  carbon  dioxide  into  anhydrous 
ethylamine  cooled  by  a  freezing  mixture.  Its  aqueous  solution,  like  that 
of  ammonium  carbamate,  does  not  precipitate  barium  chloride  unless  aided 
by  heat.  The  methylammonium-salt  of  methylcarbamic  acid  is  obtained  in 
a  similar  manner.  Phenylcarbamic  acid,  (CO)"  .  NH(C6H5) .  OH,  also  called 
carbanilic  and  anthranilic  acid,  isomeric  with  amidobenzoic  acid,  is  obtained 
by  boiling  indigo  with  potash  and  manganese  dioxide.  It  is  a  crystalline 
body,  soluble  in  water,  and  converted  by  nitrous  acid  into  salicylic 
(phenyl-carbonic)  acid,  with  evolution  of  nitrogen : 

(CO)".  NH(C6H5) .  OH  +  N02H  =  (CO)".  OC6H6.  OH  +  H20  +  N2. 
Phenyl-carbamic  acid.  Phenyl-carbonic 

acid. 

The  neutral  carbamic  ethers  are  called  urethanes.  Ethyl  carbamate, 
(CO)".  NH2 .  OC2H5,  called  simply  urethane,  is  formed  by  leaving  ethyl  car- 

*  KoTbe  and  Basarnff,  Chem.  Soc.  Journal  [2],  vi  194 

f  Basaroff's  experiments  have  not  yet  been  published  in  detail,  and  there  is  no  proof  given 
in  the  paper  above  referred  to,  that  the  compound  obtained  by  the  dehydration  of  ammonium 
carbamate  was  really  urea  and  not  carbamide. 


AMIDES.  777 

bonate  in  contact  with  aqueous  ammonia ;  and  by  the  action  of  ammonia 
on  ethyl  chlorocarbonate  (alcohol  saturated  with  carbonyl  chloride)  : 

(CO)"(OC2H5)C1    +    NH3     =     HC1    +     (CO)"(NH2)(OC2H.) 

It  forms  colorless  crystals  easily  soluble  in  water.  Methyl  carbamate,  methy- 
lie  urethane  or  urethylane,  and  amyl  carbamate  or  amylic  urethane,  are  obtained 
in  like  manner. 

Carbamic  acid  in  which  the  whole  of  the  oxygen  is  replaced  by  sulphur, 
constitutes  sulpho-carbamic  acid,  (CS)//(NH2)(SH).  There  is  also  an  oxy- 
sulpho-carbamic  acid,  (CS)//(NH2)(OH),  the  ethylic  ether  of  which  is  xan- 
thamide,  (CS)"(NH2)(OC2H6)  (p.  651). 

CARBIMIDE,  (CO)//(NH)//  or  N<  ^JT  '    ,  is  the  same  as  cyanic  acid;  and 

many  of  the  reactions  of  cyanic  acid  are  most  naturally  represented  by 
the  formula  just  given,  especially  its  conversion  into  carbon  dioxide  and 
ammonia  under  the  influence  of  acids  or  alkalies : 

NH(CO)"        +        H20        =        NH3        +        (C0)"0, 

and  the  corresponding  formation  of  ethylamine  and  its  homologues  by  dis- 
tilling cyanic  ethers  with  potash. 

CARBAMIDE,  CN2H40  or  N2(CO)"H4.  —  This  compound  is  produced  by  the 
action  of  ammonia-gas  on  carbonyl  chloride: 

COC12        +        2NH3        =         2HC1        +        N2COH4 ; 

also  by  the  action  of  ammonia  on  ethyl  carbonate,  and  by  the  decomposi- 
tion of  oxamide  at  a  red  heat :  C202N2H4  =  CON2H4  -f-  CO.  It  bears  a  very 
close  resemblance  to  urea ;  the  only  difference  indeed  yet  observed  between 
the  two  compounds,  is  in  the  products  which  they  yield  when  oxidized  by 
potassium  permanganate  in  presence  of  free  alkali  (p.  722). 

Amides  of  Oxalic  Acid.  —  Oxamic  add,  C2NH303  =  (C202)"(NH2)(OH), 
is  produced  by  heating  acid  ammonium  oxalate  to  about  230° ;  also  as  an 
ammonium-salt  by  boiling  oxamide  with  aqueous  ammonia :  C2H4N202  -f- 
H20  =  C2H2(NH4)N03.  Oxamic  acid  is  a  white  crystalline  powder,  spar- 
ingly soluble  in  cold  water,  still  less  soluble  in  alcohol  and  ether.  It  is 
monobasic,  and  forms  numerous  crystalline  metallic  salts. 

Oxamic  ethers  may  be  formed  by  substitution  of  ethyl-radicals  for  hydro- 
gen, either  in  the  group  NH2  or  in  the  group  OH  of  oxamic  acid,  the  re- 
sulting ethers  being  acid  in  the  former  case,  neutral  in  the  latter.  The 
neutral  ethers,  also  called  oxamethanes  (p.  660),  are  formed  by  the  action  of 
ammonia,  in  the  gaseous  state  or  in  alcoholic  solution,  on  neutral  oxalic 
ethers;  thus: 

(C202)"(OC2H5)2    +    NH3  =   HOC2H5    +    (C202)"(NH2)(OC2H5) 
Ethyl  oxalate.  Alcohol.  Ethyl  oxamate. 

They  are  crystalline  bodies  soluble  in  alcohol,  decomposed  by  boiling  water, 
yielding  ammonium  oxalate  and  the  corresponding  alcohol. 

The  acid  ethers  of  oxamic  acid,  containing  one  equivalent  of  alcohol- 
radical,  are  produced  by  dehydration  of  the  acid  oxalates  of  the  corre- 
sponding amines  ;  thus : 

(C202)"(ONH3C2H5)(OH)     -    OH,    =     (C202)"rNH(C2H5)](OH) 
Acid  ethylammonium  Ethyloxamic  acid, 

oxalate. 


778  AMIDES. 

Methyloxamic  and  phenyloxamic  acids  are  also  known.  These  acid  ethers 
are  metameric  with  the  neutral  oxamic  ethers  containing  the  same  alcohol- 
radicals. 

The  replacement  of  both  the  hydrogen-atoms  in  the  group  NH2  in  oxamic 
acid,  would  also  yield  monobasic  acid  ethers ;  none  of  these  are,  however, 
known  in  the  free  state,  but  the  ethylic  ethers  of  dimethyl-  and  diethyl- 
oxamic  acids  have  been  obtained;  e.g.,  ethylic  dimethyl-oxamate,  (C20,)//N 
(CH3)2(OC2H5). 

The  imide  of  oxalic  acid  is  not  known. 

OXAMIDE,  N2(C202)//H4.  —  This  compound  is  produced  by  the  action  of 
heat  on  neutral  ammonium  oxalate  (p.  659),  but  is  more  advantageously 
prepared  by  the  action  of  ammonia  on  neutral  ethyl  oxalate.  It  is  also 
formed  in  several  reactions  from  cyanogen  and  cyanides:  an  aqueous  solu- 
tion of  hydrocyanic  acid,  mixed  with  hydrogen  dioxide,  yields  a  crystal- 
line deposit  of  oxamide :  2CNH  -f  H202  =  C2N2H402. 

Oxamide  is  a  white,  light,  tasteless  powder,  insoluble  in  cold  water, 
slightly  soluble  in  boiling  water,  insoluble  in  alcohol.  Heated  in  an  open 
tube,  it  volatilizes  and  forms  a  crystalline  sublimate ;  but  its  vapor,  passed 
through  a  red-hot  tube,  is  completely  resolved  into  carbon  monoxide,  am- 
monium carbonate,  hydrocyanic  acid,  and  urea  (or  carbamide) : 

2C2N2H402     =     CO     +     C02    -f     NH3    +     CNH     +     CN2H40. 

Dilute  mineral  acids  decompose  it,  yielding  an  ammonium-salt  and  free 
oxalic  acid ;  e.  g. : 

C2N2H402    +     S04H2    +     2H20     =     S04(NH4)2     +     C2H204. 

Dimethyloxamide,  N2(C202)//H2(CH3)2,  is  produced  by  the  dry  distillation 
of  methylammonium  oxalate: 

C2(CH6N)204  2H20        =        C2N2H2(CH3)202. 

Diethyloxamide,  diamyloxamide,  diphenyloxamide,  and  dinaphthyloxamide, 
are  obtained  in  a  similar  manner. 


AMIDES  DERIVED  FROM  ACIDS  OF  HIGHER  ATOMICITY. 

Our  knowledge  of  these  amides  is  somewhat  limited :  we  shall  notice  only 
those  derived  from  malic  and  from  citric  acid. 

Malic  acid,  (C4H302)///(OH)3,  which  is  triatomic  and  bibasic,  forms  an 
acid  amide  and  a  neutral  amide  : 

fOH  fOH  fOH 

(C4H802)//X  I  OH  (C4H,0S)'"  I NH2  (C4H80S)'"  j  NH, 

Malic  acid.  Malamic  acid.  Malamide. 

Malamide  is  deposited  in  small  crystals,  when  ammonia-gas  is  passed  into 
an  alcoholic  solution  of  ethyl  malate : 

<WC2H5)205        +        2NH3        =        2C2H60        +        C4H8N203 
Ethyl  malate.  Alcohol.  Malamide. 

Malamic  acid,  C4H7N04,  is  not  known  in  the  free  state ;  but  its  ethylic 


AMIDES.  779 

ether,  or  malamethane,  C4H6(C2H5)N04,  is  produced  as  a  crystalline  mass, 
when  dry  ethyl  malate  is  saturated  with  ammonia-gas: 

C4H4(C2H6)205    +     NH3    :   :    C2H60    +     C4H6(C2H5)N04. 

Malamide  is  metameric,  not  identical,  with  asparagin,  a  substance  found  in 
the  root  of  marsh -mallow,  in  asparagus-shoots,  and  in  several  other  plants. 
To  prepare  asparagin,  marsh-mallow  roots  are  chopped  small,  and  mace- 
rated in  the  cold  with  milk  of  lime ;  'the  filtered  liquid  is  precipitated  by 
carbonate  of  ammonia ;  and  the  clear  solution  evaporated  in  the  water- 
bath  to  a  syrupy  state.  The  impure  asparagin,  which  separates  after  a 
few  days,  is  purified  by  re-crystallization.  Asparagin  forms  brilliant, 
transparent,  colorless  crystals,  which  have  a  faint,  cooling  taste,  and  are 
freely  soluble  in  water,  especially  when  hot.  When  dissolved  in  a  saccha- 
rine liquid,  which  is  afterward  made  to  ferment,  or  when  heated  with 
water  under  pressure  in  a  close  vessel,  or  when  boiled  with  an  acid  or  an 
alkali,  it  is  converted  into  ammonia  and  aspartic  acid,  an  acid  metameric 
with  malamic  acid. 

Asparagin  differs  from  malamide  in  crystalline  forms;  moreover,  it  con- 
tains water  of  crystallization,  the  composition  of  the  crystals  being  C4H8 
N203 .  H20,  whereas  those  of  malamide  are  anhydrous.  The  two  sub- 
stances differ  also  in  their  action  on  polarized  light,  malamide  having  a 
specific  rotatory  power  of  — 47-5°,  whereas  that  of  asparagin  in  an  acid 
solution  is  -f-  35°,  and  in  an  ammoniacal  solution  — 11°  18'.  Lastly,  mal- 
amide, when  treated  with  alkalies,  is  easily  resolved  into  ammonia  and 
malic  acid,  whereas  asparagin,  as  already  observed,  yields  ammonia  and 
aspartic  acid. 

The  difference  of  constitution  between  these  metameric  bodies  may  be 
represented  by  the  following  formulae  : 


COOH 

COOH 

CONH2 

CONH2 

CONHa 

CHOH 

CHNH2 

CHOH 

CHNH2 

CHOH    ' 

CH2 

k 

CH2 

CH2 

CH2 

COOH 

COOH 

COOH 

COOH 

CONH2 

Malic  acid. 

Aspartic 

Malamic 

Asparagin. 

Malamide. 

acid.  acid. 

These  formulae  indicate  that  aspartic  acid  is  bibasic,  malamic  acid  and 
asparagin  monobasic,  and  malamide  neutral.  Now,  malamide  is  certainly 
neutral,  and  asparagin  forms  salts  by  substitution  of  metals  for  one  of  its 
hydrogen-atoms.  The  basicity  of  malamic  and  aspartic  acids  is  not  very 
distinctly  made  out.  Aspartic  acid  is  commonly  said  to  be  monobasic, 
forming  neutral  salts,  like  C4H6KN04,  and  likewise  basic  salts  ;  but  the  as- 
patates  have  not  been  very  fully  investigated,  and  it  is  quite  possible  that 
these  so-called  basic  salts  may  really  be  neutral. 

There  are  also  phenylated  amides  of  malic  acid,  viz.,  diphenyl-malamide 
or  malanilide,  C4H6(C6H5)2N203,  and  phenyl-malimide  or  malanil,  C,0H9N03  = 

(C4H302)///  {  kp  TT    ,  produced  simultaneously  by  fusing  malic  acid  with 

v  ^^65 

aniline;    and  phenyl-malamic  or  malanilic  acid,   C10HnN04   =    (C^oO,)'" 

f  OC6H5 

-|  NH2     ,  obtained  as  an  ammonium-salt  by  boiling  phenyl-malimide  with 

(^  OH 
aqueous  ammonia. 

Lastly,  the  action  of  heat  on  acid  ammonium-malate  yields  malamyl-nitrile, 
(C4II302)///N,  which  is  identical  with  the  imide  of  fumaric  acid,  and  when 


780  AMIDES. 

boiled  with  hydrochloric  or  nitric  acid,  yields  compounds  of  these  acids 
with  an  optically  inactive  variety  of  aspartic  acid :  C4H302N  -f  2H20  = 
C4H7N04. 

AMIDES  OF  CITRIC  ACID.  —  Citramide,  ^s(C6ttspi)///H6J  is  a  crystalline 
compound,  slightly  soluble  in  water,  obtained  by  the  action  of  alcoholic  am- 
monia on  ethyl  or  methyl  citrate.  —  Triphenyl-citramide,  N3(C6H504)///(C6 
H5)3HS,  obtained  by  the  action  of  heat  on  neutral  phenylammonium  citrate, 
C«H6(C6H8N)304,  from  which  it  differs  by  3H20,  crystallizes  from  alcohol 
in  colorless  striated  prisms. 

Citrimide  and  citramic  acid  are  not  known ;  but  phenylic  derivatives  of 
these  amides  have  been  obtained. 


UNCLASSIFIED  ORGANIC  COMPOUNDS. 

THERE  are  still  many  organic  compounds,  especially  those  obtained  from 
natural  sources,  which  cannot,  in  the  present  state  of  our  knowledge,  be 
included  with  certainty  in  either  of  the  preceding  groups  or  series.  Some 
of  these  have  been  described  in  connection  with  the  more  definitely  known 
compounds  to  which  they  are  most  closely  allied  in  their  origin  or  proper- 
ties. It  remains  to  describe  the  Organic  Coloring  principles,  the  Resins 
and  Balsams,  and  the  Albuminous  and  Gelatinous  principles  of  the  living 
organism ;  these  last,  however,  will  be  most  conveniently  described  under 
the  head  of  "Animal  Chemistry." 


ORGANIC  COLORING  PRINCIPLES. 

The  organic  coloring  principles  are  substances  of  very  considerable  prac- 
tical importance  in  relation  to  the  arts ;  several  of  them,  too,  have  been 
made  the  subjects  of  extensive  and  successful  chemical  investigation.  With 
the  exception  of  one  red  dye,  cochineal,  they  are  all  of  vegetable  origin. 

The  art  of  dyeing  is  founded  upon  an  affinity  or  attraction  existing  be- 
tween the  coloring  matter  of  the  dye  and  the  fibre  of  the  fabric.  In  wool 
and  silk  this  affinity  is  usually  very  considerable,  and  to  such  tissues  a 
permanent  stain  is  very  easily  communicated;  but  with  cotton  and  flax  it 
is  much  weaker.  Recourse  is  then  had  to  a  third  substance,  which  does 
possess  such  affinity  in  a  high  degree,  and  with  this  the  cloth  is  impreg- 
nated. Such  substances  are  termed  mordants.  Alumina,  ferric  oxide,  and 
stannic  oxide  are  bodies  of  this  class. 

When  an  infusion  of  some  dye-wood,  as  logwood,  for  example,  is  mixed 
with  alum  and  a  little  alkali,  a  precipitate  falls,  consisting  of  alumina  in 
.combination  with  coloring  matter,  called  a  lake;  it  is  by  the  formation  of 
this  insoluble  substance  within  the  fibre  that  a  permanent  dyeing  of  the 
cloth  is  effected.  Ferric  oxide  usually  gives  rise  to  dull,  heavy  colors; 
alumina  and  stannic  oxide,  especially  the  latter,  to  brilliant  ones.  It  is 
easy  to  see  that,  by  applying  the  mordant  partially  to  the  cloth,  by  a 
wood-block  or  otherwise,  a  pattern  may  be  produced,  as  the  color  will  be 
removed  from  the  other  portions  by  washing. 

Indigo.  —  Indigo  is  the  most  important  member  of  the  group  of  blue 
coloring  matters.  It  is  the  product  of  several  species  of  the  genus  Indigo- 
fera,  which  grow  principally  in  warm  climates.  When  the  leaves  of  these 
plants  are  placed  in  a  vessel  of  water  and  allowed  to  ferment,  a  yellow  sub- 
stance is  dissolved  out,  which  by  contact  of  air  becomes  deep-blue  and  in- 
soluble, and  finally  precipitates.  This,  washed  and  carefully  dried,  con- 
stitutes the  indigo  of  commerce.  It  is  not  contained  ready  formed  in  the 
plant,  but  is  produced  by  the  oxidation  of  some  substance  there  present. 
Neither  is  the  fermentation  essential;  as  a  mere  infusion  of  the  plant  in 
hot  water  deposits  indigo  by  standing  in  the  air. 

The  occurrence  of  small  quantities -of  indigo  in  urine  had  been  observed 

by  Hassall  and  others:  it  was,  however,  generally  considered  as  a  morbid 

secretion;  but  lately  Dr.  Schunck  has  proved  that  traces  of  indigo  may  be 

procured  from  healthy  urine.     The  process  by  means  of  which  this  object. 

66  781 


782  ORGANIC    COLORING    PRINCIPLES. 

may  be  obtained  is  rather  complicated.  For  a  description  of  this  process, 
and  for  a  full  account  of  his  researches  on  the  formation  of  indigo-blue, 
which  would  overstep  the  limits  of  this  elementary  work,  the  reader  is  re- 
ferred to  Dr.  Schunck's  original  papers.* 

Indigo  comes  into  the  market  in  the  form  of  cubic  cakes,  which,  when 
rubbed  with  a  hard  body,  exhibits  a  copper-red  appearance  :  its  powder 
has  a  deep-blue  tint.  The  best  indigo  is  so  light  as  to  float  upon  water. 
In  addition  to  the  blue  coloring  matter,  or  true  indigo,  it  contains  at  least 
half  its  weight  of  various  impurities,  among  which  may  be  noticed  a  red 
resinous  matter,  the  indigo-red  of  Berzelius  :  these  may  be  extracted  by  boil- 
ing the  powdered  indigo  in  dilute  acid,  in  alkali,  and  afterwards  in  alcohol. 
Pure  indigo  is  quite  insoluble  in  water,  alcohol,  oils,  dilute  acids,  and 
alkalies;  it  dissolves  in  about  15  parts  of  concentrated  sulphuric  acid, 
forming  a  deep-blue  pasty  mass,  entirely  soluble  in  water,  and  often  used 
in  dyeing;  this  is  sulphindylic  or  sulphindigotic  acid,  a  compound  analogous 
to  ethyl-sulphuric  acid,  capable  of  forming  with  alkaline  bases  blue  salts, 
which,  though  easily  soluble  in  pure  water,  are  insoluble  in  saline  solutions. 
If  an  insufficient  quantity  of  sulphuric  acid  has  been  employed,  or  the 
digestion  not  long  enough  continued,  a  purple  powder  is  left  on  diluting  the 
acid  mass,  soluble  in  a  large  quantity  of  pure  water.  The  Nordhausen 
acid  answers  far  better  for  dissolving  indigo  than  ordinary  oil  of  vitriol. 
Indigo  may,  by  cautious  management,  be  volatilized :  it  forms  a  fine  pur- 
ple vapor,  which  condenses  in  brilliant  copper-colored  needles.  The  best 
method  of  subliming  this  substance  is,  according  to  Mr.  Taylor,  to  mix  it 
with  plaster  of  Paris,  make  the  whole  into  a  paste  with  water,  and  spread 
it  upon  an  iron  plate.  1  part  indigo  and  2  parts  plaster  answer  very  well. 
This,  when  quite  dry,  is  heated  by  a  spirit-lamp :  the  volatilization  of  the 
indigo  is  aided  by  the  vapor  of  water  disengaged  from  the  gypsum,  and 
the  surface  of  the  mass  becomes  covered  with  beautiful  crystals  of  pure  in- 
digo, which  may  be  easily  removed  by  a  thin  spatula.  At  a  higher  tem- 
perature, charring  and  decomposition  take  place. 

In  contact  with  deoxidizing  agents,  and  with  an  alkali,  indigo  suffers  a 
very  curious  change :  it  becomes  soluble  and  nearly  colorless,  perhaps  re- 
turning to  the  same  state  in  which  it  existed  in  the  plant.  It  is  on  this 
principle  that  the  dyer  prepares  his  indigo-vat :  5  parts  of  powdered  indigo, 
10  parts  of  green  vitriol,  15  parts  of  slaked  lime,  and  60  parts  of  water, 
are  agitated  together  in  a  close  vessel,  and  then  left  to  stand.  The  ferrous 
hydrate,  in  conjunction  with  the  excess  of  lime,  reduces  the  indigo  to  the 
soluble  state  :  a  yellowish  liquid  is  produced,  from  which  acids  precipitate 
the  white  or  deoxidized  indigo  as  a  flocculent  insoluble  substance,  which  ab- 
sorbs oxygen  with  the  greatest  avidity,  and  becomes  blue.  Cloth,  steeped 
in  the  alkaline  liquid,  and  then  exposed  to  the  air,  acquires  a  deep  and 
most  permanent  blue  tint  by  the  deposition  of  solid  insoluble  indigo  in 
the  substance  of  the  fibre.  Instead  of  the  iron  salt  and  lime,  a  mixture  of 
dilute  caustic  soda  and  grape-sugar  dissolved  in  alcohol  may  be  used:  the 
sugar  becomes  oxidized  to  formic  acid,  and  the  indigo  reduced.  On  allow- 
ing a  solution  of  this  description  to  remain  in  contact  with  the  air,  it  ab- 
sorbs oxygen,  and  deposits  the  indigo  in  the  crystalline  state. 

The  following  formulae  represent  the  composition  of  the  bodies  just  de- 
scribed : 

Blue  insoluble  indigo     ....        C8H5NO. 

White,  or  reduced  indigo  f    .         .         .         C]6H]2N202. 

Sulphindylic  acid  ....         C8H5NO .  S03. 

*  Memoirs  of  the  Literary  and  Philosophical  Society  of  Manchester,  vol.  xii.  177 ;  xiv.  181, 
239;  also  Philosophical  Magazine  [3],  x.  73;  xv.  99;  [4],  xv.  29,117. 

f  Properly  hydrogenized  indigo,  if  the  above  be   the  correct  view ;  white  indigo  may,  how- 
ever, be  viewed  as  a  hydrate,  and  blue  indigo  as  an  oxide  of  one  and  the  same  substance : 
White  indigo      .        .  CiflH10N«Q  •  H20. 

Blueiudigo CjeH^NgO.O. 


INDIGO.  783 

PRODUCTS  OF  THE  DECOMPOSITION  OF  INDIGO.  —  The  products  of  the  de- 
structive modifications  of  indigo  by  powerful  chemical  agents  of  an  oxi- 
dizing nature  are  both  numerous  and  interesting,  inasmuch  as  they  connect 
this  substance  in  a  very  curious  manner  with  several  other  groups  of 
organic  bodies,  especially  with  those  of  the  salicyl  and  phenyl  series. 
Many  of  them  are  exceedingly  beautiful,  and  possess  very  remarkable  pro- 
perties. 

ISATIN,  C3H5N02.  —  To  prepare  this  substance,  which  contains  the  ele- 
ments of  indigo  with  1  atom  of  oxygen,  1  part  of  indigo  reduced  to  fine 
powder,  and  rubbed  to  a  paste  with  water,  is  gently  heated  with  a  mixture 
of  1  part  of  sulphuric  acid  and  1  part  of  potassium  bichromate  dissolved 
in  20  or  30  parts  of  water.  The  indigo  dissolves,  with  very  slight  disen- 
gagement of  carbon  dioxide,  towards  the  end,  forming  a  yellow-brown 
solution,  which,  on  standing,  deposits  impure  isatin  in  crystals.  These  are 
collected,  slightly  washed,  and  redissolved  in  boiling  water:  the  filtered 
solution  on  cooling  deposits  the  isatin  in  a  state  of  purity.  Or,  powdered 
indigo  may  be  mixed  with  water  to  a  thin  paste,  heated  to  the  boiling  point 
in  a  large  capsule,  and  nitric  acid  added  by  small  portions  until  the  blue 
color  disappears  :  the  whole  is  then  largely  diluted  with  boiling  water,  and 
filtered.  The  impure  isatin  which  separates  on  cooling  is  washed  with 
water  containing  a  little  ammonia,  and  recrystallized.  Both  these  pro- 
cesses require  careful  management,  or  the  oxidizing  action  proceeds  too 
far,  and  the  product  is  destroyed. 

Isatin  forms  deep  yellowish-red  prismatic  crystals  of  great  beauty  and 
lustre :  it  is  sparingly  soluble  in  cold  water,  freely  in  boiling  water,  and 
also  in  alcohol.  The  solution  colors  the  skin  yellow,  and  causes  it  to  emit 
a  very  disagreeable  odor.  Isatin  cannot  be  sublimed. 

A  solution  of  potash  dissolves  isatin  with  purple  color  :  from  this  solution 
acids  precipitate  the  isatin  unchanged.  On  boiling,  however,  the  color  is 
destroyed,  and  the  liquid  yields  on  evaporation  crystals  of  the  potassium- 
salt  of  isatic  acid,  C8H7N03.  In  the  free  state  this  is  a  white  and  imper- 
fectly crystalline  powder,  soluble  in  water,  and  easily  decomposed  into 
isatin  and  water. 

By  chlorine  isatin  is  converted  into  chlorisatin,  C8H4C1N02,  a  body  closely 
resembling  isatin  itself  in  properties.  If  an  alcoholic  solution  and  excess 
of  chlorine  be  employed,  other  products  make  their  appearance,  as  chloranil, 
CgCl402,  Irichlorophenol,  C6H3C130,  and  a  resinous  substance.  The  former 
of  these  substances,  the  position  of  which  in  the  quinone  series  has  been 
already  noticed  (p.  681),  yields  further  products  with  potash  and  ammonia. 
Bromisatin  is  easily  formed.  The  change  which  isatin  and  its  chlorinated 
and  brominated  congeners  undergo  when  submitted  to  the  action  of  fusing 
potassium  hydrate  has  been  already  considered  in  the  section  on  the  Or- 
ganic Bases  (p.  740). 

Exposed  to  the  action  of  hydrogen  and  ammonium  sulphide,  isatin  yields 
several  new  compounds,  as  isathyde,  sulphisathyde,  &c. 

A  hot  solution  of  isatin,  treated  with  ammonium  sulphide,  gives  rise  to  a 
deposit  of  sulphur,  a  white  crystallized  substance  being  produced  at  the 
same  time :  it  has  received  the  name  of  isathyde,  and  contains  C8H6N02. 
It  bears  to  isatin  the  same  relation  as  white  to  blue  indigo.  If  the  am- 
monium sulphide  be  replaced  by  hydrogen  sulphide,  bisulphisathyde,  C8H6NOS, 
is  produced,  which  is  derived  from  the  former  by  substitution  of  one  atom 
of  sulphur  for  oxygen.  An  alcoholic  solution  of  potash  converts  this  last 
compound  into  sulphisathyde,  C16H12N203S,  or  a  double  molecule  of  isathyde 
in  which  one  quarter  of  the  oxygen  is  replaced  by  sulphur.  Under  the  in- 
fluence of  cold  aqueous  solution  of  potash,  bisulphisathyde  yields  indin, 
C8H6NO,  which  is  polymeric  with  white  indigo.  When  treated  with  boiling 


784  OKGANIC    COLOKING    PKINCIPLES. 

potash,  indin  fixes  the  elements  of  one  molecule  of  water,  and  becomes  in- 
dinic  acid,  C8H8N02,  the  potassium-salt  of  which  forms  fine  black  needles. 

Ammoniacal  gas  and  solution  of  ammonia  yield  with  isatin  a  series  of 
interesting  substances,  containing  the  nitrogen  of  the  ammonia  in  addition 
to  that  of  the  isatin. 

ACTION  OF  CHLORINE  ON  INDIGO.  — In  the  dry  state  chlorine  has  no  action 
whatever  on  indigo,  even  at  the  temperature  of  100°.  In  contact  with  wa- 
ter, the  blue  color  is  instantly  destroyed,  and  cannot  again  be  restored. 
The  same  thing  happens  with  the  blue  solution  of  sulphindylic  acid.  When 
chlorine  is  passed  into  a  mixture  of  powdered  indigo  and  water  until  the 
color  disappears,  and  the  product  is  then  distilled  into  a  retort,  water  con- 
taining hydrochloric  acid  and  a  mixture  of  two  volatile  bodies,  trichloran- 
iline,  C6H4C13N,  and  trichlorophenol,  C6H3C130,  pass  over  into  the  receiver, 
while  the  residue  in  the  retort  is  found  to  contain  chlorisatin,  already  men- 
tioned, and  bichlorisatin,  C8H3C12N02,  much  resembling  the  former,  but  more 
freely  soluble  in  alcohol.  Both  these  bodies  yield  acids  in  contact  with 
boiling  solution  of  potash,  by  assimilating  the  elements  of  water. 

The  action  of  bromine  on  indigo  is  very  similar. 

ANILIC  AND  PICRIC  ACIDS.  — Anilic  or  indigotic  acid  is  prepared  by  add- 
ing powdered  indigo  to  a  boiling  mixture  of  1  part  of  nitric  acid  and  10 
parts  of  water,  until  the  disengagement  of  gas  ceases,  filtering  the  hot  dark- 
colored  liquid,  arid  allowing  it  to  stand.  The  impure  anilic  acid  so  obtained 
is  converted  into  the  lead-salt,  which  is  purified  by  crystallization  and  the 
use  of  animal  charcoal,  and  then  decomposed  by  sulphuric  acid.  Anilic 
acid  forms  fine  white  or  yellowish  needles,  which  have  a  feebly  acid  taste, 
and  a  very  sparing  degree  of  solubility  in  cold  water.  In  hot  water  and  in 
alcohol  it  dissolves  easily.  It  melts  when  heated,  and  on  cooling  assumes 
a  crystalline  structure.  By  careful  management  it  may  be  sublimed  un- 
changed. Anilic  acid  contains  CfH^NOg  =  C7H5(N02)03.  The  same  acid  is 
readily  prepared  from  salicylic  acid  (p.  655).  Hence  it  is  more  appro- 
priately called  nitrosalicylic  acid. 

Picric,  carbazotic,  or  nitrophenisic  acid,  C6IT3(N02)30,  already  described 
among  the  derivatives  of  phenol  (p.  552),  is  also  one  of  the  ultimate  products 
of  the  action  of  nitric  acid  upon  indigo. 

PRODUCTS  OF  THE  ACTION  OF  POTASSIUM  HYDRATE  UPON  INDIGO. — One 
of  the  most  remarkable  of  these,  aniline,  has  been  already  described  (p. 
739).  When  powdered  indigo  is  boiled  with  a  very  concentrated  solution 
of  caustic  potash,  it  is  gradually  dissolved,  with  the  exception  of  some 
brownish  flocculent  matter,  and  the  liquid  on  cooling  deposits  yellow  crys- 
tals of  the  potassium-salt  of  chrysanilic  add,  which  can  be  procured  in  a  purer 
state  by  dissolving  the  crystals  in  water,  filtering  from  reproduced  indigo, 
and  adding  a  slight  excess  of  mineral  acid.  Chrysanilic  acid  can  be  ob- 
tained in  indistinct  crystals  from  weak  alcohol ;  it  is  supposed  to  contain 
C28H22N<Og;  but  it  is  very  probably  a  mixture  of  several  substances,  espe- 
cially isatic  acid. 

When  this  substance  is  boiled  with  mineral  acids,  it  is  decomposed  into 
anthranilic,  or  phenyl-carbamic  acid,  C7H7N02  (p.  770),  which  remains  in 
solution,  and  a  blue  insoluble  matter  resembling  indigo:  a  similar  effect  is 
slowly  produced  by  the  action  of  the  air  upon  an  alcoholic  solution  of  chrys- 
anilic  acid.  Anthranilic  acid  is  colorless,  sparingly  soluble  in  cold  water, 
easily  soluble  in  alcohol.  It  melts  when  heated,  sublimes  under  favorable 
circumstances,  but  decomposes  entirely  when  heated  in  a  narrow  tube  into 
carbon  dioxide  and  aniline.  By  treatment  with  nitrous  acid,  it  is  converted 
into  salicylic  acid. 

According  to  Cahours,  pure  indigo  can  also  be  converted  into  salicylic 


LICHENS.  785 

ac;d  by  fusion  with  potash  :  a  particular  temperature  is  required,  some- 
what above  299°  C.  (570°  F.),  and  the  operation  is  by  no  means  always  suc- 
cessful. 

Lichens. — Litmus  is  used  by  the  dyer  as  a  red  coloring  matter;  the 
chemist  employs  it  in  the  blue  state  as  a  test  for  the  presence  of  acid,  by 
which  it  is  instantly  reddened. 

In  preparing  test-papers  for  chemical  use  with  infusion  of  litmus,  good 
writing  or  drawing  paper,  free  from  alum  and  other  acid  salts,  should  be 
chosen.  Those  sheets  which  after  drying  exhibit  red  spots,  or  patches, 
may  be  reddened  completely  by  a  little  dilute  acetic  acid,  and  used,  with 
much  greater  advantage  than  tumeric-paper,  to  discover  the  presence  of 
free  alkali,  which  restores  the  blue  color. 

Many  liquids,  when  exposed  in  a  moistened  state  to  the  action  of  ammo- 
nia, yield  purple  or  blue  coloring  principles,  which,  like  indigo,  do  not 
pre-exist  in  the  plant  itself.  Thus,  the  Roccella  tinctoria,  the  Variolaria  or- 
cina,  the  Lecanora  tartarea,  &c.,  when  ground  to  paste  with  water,  mixed 
with  putrid  urine  or  solution  of  ammonium  carbonate,  and  left  for  some 
time  freely  exposed  to  the  air,  furnish  the  archil,  litmus,  and  cudbear  of  com- 
merce, very  similar  substances,  differing  chiefly  in  the  details  of  the  pre- 
paration. From  these  the  coloring  matter  is  easily  extracted  by  water  or 
very  dilute  solution  of  ammonia. 

The  lichens  have  been  extensively  examined  by  Schunck,  Stenhouse, 
and  several  other  chemists.  The  whole  subject  has  been  lately  revised  by 
Strecker,  whose  formulae  have  been  adopted  in  the  following  succinct  ac- 
count: 

ERYTHRIC  ACID. — The  lichen  Roccella  tinctoria,  from  which  the  finest 
kind  of  archil  is  prepared,  is  boiled  with  milk  of  lime;  the  filtered  solu- 
tion is  precipitated  by  hydrochloric  acid,  and  the  precipitate  dried  and  dis- 
solved in  warm,  not  boiling  alcohol,  from  which  on  cooling  crystals  of  ery- 
tliric  acid  are  deposited.  This  is  a  very  feeble  acid,  colorless,  inodorous, 
difficultly  soluble  in  cold  and  even  in  boiling  water,  readily  soluble  in  ether. 
Its  solution,  when  mixed  with  chloride  of  lime,  assumes  a  blood-red  color. 
Boiled  with  water  for  some  time,  erythric  acid  absorbs  one  molecule  and 
yields  picro-ert/thrin,  a  crystallizable,  bitter  principle,  and  orsellinic  acid.  If 
the  ebullition  be  continued,  the  orsellinic  acid  undergoes  a  further  change, 
being  converted  into  orcin  (p.  552). 

Picro-erythrin,  boiled  with  baryta-water,  is  decomposed  into  orcin,  ery- 
thrite  (p.  571),  and  carbon  dioxide. 

The  composition  of  these  various  substances  is  expressed  by  the  follow- 
ing formulfie : 

Erythric  acid C20H22010. 

Orsellinic  acid C8H804. 

Picro-erythrin C,2H)6O7. 

Orcin C7H802. 

And  the  successive  changes  which  occur  by  ebullition  are  represented  by 
the  following  equations: 

CaoHaAo       +       H,0       =       C8H804         +         C18HMOr 
Erythric  acid.  Orsellinic  acid.       Picro-erythrin. 

C8H804        =        C7H802       +        C02. 
Orsellinic  acid.  Orcin. 

C12H1607     +     H20     -    C7H802    +     C4H1004     +     C02. 
Picro-erythrin.  Orcin.  Erythro- 

maiiiute. 
66* 


786  ORGANIC    COLORING    PRINCIPLES. 

LECANORIC  OR  ALPHA-ORSELLIC  ACID  is  obtained  from  the  South  Ameri- 
can variety  of  Roccella  tinctoria.  The  preparation  and  the  properties  of 
this  substance  are  perfectly  analogous  to  those  of  erythric  acid.  It  con- 
tains C16H1407,  and  likewise  yields  orsellinic  acid  by  boiling  with  baryta- 
water  : 

C16H1407        +        H20        =        2C8H804 
Lecanoric  acid.  Orsellinic  acid. 

If  the  ebullition  be  too  long  continued,  a  great  portion  of  the  orsellinic 
acid  is  converted  into  orcin. 

ORSELLINIC  ACID,  whether  prepared  from  erythric  or  lecanoric  acid, 
forms  crystals  which  are  far  more  soluble  in  water  than  either  of  the  acids 
from  which  it  has  been  prepared.  Its  taste  is  somewhat  bitter.  Boiled 
with  water  it  yields  orciri ;  under  the  influence  of  air  and  ammonia,  it  as- 
sumes a  beautiful  purple  color. 

If  the  lichens,  instead  of  being  treated  with  milk  of  lime,  are  exhausted 
with  boiling  alcohol,  the  erythric  and  lecanoric  acids  are  likewise  decom- 
posed; but  instead  of  orsellinic  acid,  the  ether  of  this  substance,  C8H7 
(C2H5)04,  is  formed.  This  ether  was  formerly  described  under  the  name 
pseudo-erythrin,  until  Dr.  Schunck  pointed  out  its  true  nature.  Ethyl  orsel- 
liriate  may  be  likewise  produced  by  boiling  pure  orsellinic  acid  with  alco- 
hol. It  crystallizes  in  colorless  lustrous  plates,  which  are  readily  soluble 
in  boiling  water,  alcohol,  and  ether. 

BETA-ORSELLIC  ACID  is  found  in  Roccella  tinctoria  grown  at  the  Cape:  it 
is  obtained  like  erythric  and  alpha-orsellic  acid,  which  it  resembles  in  pro- 
perties. Beta-orsellic  acid  contains  C34H32Oi5:  by  boiling  with  water  it 
likewise  yields  orsellinic  acid,  together  with  hair-like  crystals  of  a  silvery 
lustre,  of  a  substance  called  roccellinin,  which  has  the  composition  C18H1607. 

C34H329i5        =         2C8H804         -f         C18H1?07 
Beta-orsellic  acid.      Orsellinic  acid.  Roccellinin. 

The  decomposition  of  beta-orsellic  acid  is  obviously  analogous  to  that  of 
erythric  acid,  the  roccellinin  representing  the  picro-erythrin. 

EVERNIC  ACID  is  extracted  by  milk  of  lime  from  Evernia  prunastri,  which 
was  formerly  believed  to  contain  lecanoric  acid.  Evernic  acid  is  very  diffi- 
cultly soluble  even  in  boiling  water:  it  assumes  a  yellow  color  with  chloride 
of  lime.  When  boiled  with  an  alkali,  it  yields  another  crystalline  acid, 
everninic  acid,  differing  from  the  preceding  by  its  free  solubility  in  boiling 
water.  The  composition  of  evernic  acid  is  represented  by  the  formula 
C,7II,607,  that  of  everninic  acid  by  C9H,004.  Evernic  acid,  when  boiled  for 
a  considerable  time  with  bai-yta,  yields  orcin :  everninic  acid  does  not  give 
a  trace  of  this  substance.  It  is  therefore  probable  that  evernic  acid,  under 
the  influence  of  alkalies,  yields,  in  addition  to  everninic  acid,  likewise 
orsellinic  acid,  from  which  the  orcin  is  derived,  and  that  this  decomposi- 
tion is  represented  by  the  equation: 

C17H1607    +     H20    =    C8H804      -f       C9H1004 
Evernic  acid.  Orsellinic  acid.     Everninic  acid. 

PARELLIC  ACID. — Lecanora  parella  contains  an  acid  probably  analogous 
to  erythric,  alpha-orsellic,  beta-orsellic,  and  evernic  acids,  the  composition 
of  which  is,  however,  still  unknown.     By  boiling  with  baryta  it  yields  orsel-  • 
linic  acid  and  parellic  acid,  C9H604. 

ORCIN,  C7H802,  is  the  general  product  of  decomposition  of  the  acids  pre- 
viously described,  under  the  influence  of  heat  or  alkaline  earths.  It.  is  a 
diatomic  phenol,  and  has  already  been  described  under  that  head  (p.  562). 


COCHINEAL  —  MADDER.  787 

In  contact  with  ammonia  and  oxygen  it  is  converted  into  a  deep-red  color- 
ing matter  called  orcein,  C7H7N03. 

Other  substances  are  occasionally  present  in  lichens :  thus,  the  Usnea 
barbata  and  several  other  lichens  contain  usnic  acid,  a  substance  crystallizing 
from  alcohol  in  fine  yellowish-white  needles  with  metallic  lustre,  having 
the  formula  C,9HI807.  It  gives  no  orcin  by  distillation,  but  a  substance 
similar  to  it,  which  probably  contains  C8H1002,  and  has  been  designated  by 
the  name  of  beta-orcin.  The  Parmelia  parietina  furnishes  another  new  sub- 
stance, chrysophanic  acid,  crystallizing  in  fine  golden-yellow  scales,  and  con- 
taining C10H803.  It  is  a  very  stable  substance,  and  may  be  sublimed 
without  much  decomposition.  The  same  body  is  present  in  rhubarb,  to- 
gether with  emodin,  a  principle  closely  resembling  chrysophanic  acid. 

Cochineal.  — This  is  a  little  insect,  the  Coccus  cacti,  which  lives  on  several 
species  of  cactus,  found  in  warm  climates,  and  cultivated  for  the  purpose, 
as  in  Central  America.  The  dried  body  of  the  insect  yields  to  water  and 
alcohol  a  magnificent  red  coloring  matter,  precipitable  by  alumina  and 
oxide  of  tin :  carmine  is  a  preparation  of  this  kind.  In  cochineal  the  color- 
ing matter  is  associated  with  several  inorganic  salts,  especially  phosphates 
and  nitrogenous  substances.  Mr.  Warren  De  La  Rue,  who  has  published 
a  very  elaborate  investigation  of  cochineal,*  has  separated  the  pure  color- 
ing matter,  which  he  calls  carminic  acid,  by  the  following  process :  The 
aqueous  decoction  of  the  insect  is  precipitated  by  lead  acetate,  and  the  im- 
pure lead  carminate  washed  and  decomposed  by  hydrogen  sulphide :  the 
coloring  matter  thus  separated  is  submitted  again  to  the  same  treatment. 
A  solution  of  carminic  acid  is  thus  obtained,  which  is  evaporated  to  dry- 
ness,  redissolved  in  absolute  alcohol,  and  digested  with  crude  lead  car- 
bonate, whereby  a  small  quantity  of  phosphoric  acid  is  separated,  and, 
lastly,  mixed  with  ether,  which  separates  a  trace  of  a  nitrogenous  substance. 
The  residue  now  obtained  on  evaporation  is  pure  carminic  acid.  It  is  a 
purple-brown  mass,  yielding  a  fine  red  powder,  soluble  in  water  and  alco- 
hol in  all  proportions,  slightly  soluble  in  ether.  It  is  soluble  without  de- 
composition in  concentrated  sulphuric  acid,  but  readily  attacked  by  chlorine, 
bromine,  and  iodine,  which  change  its  color  to  yellow.  It  resists  a  tem- 
perature of  130°  C.  (277°  F.),  but  is  charred  when  heated  more  strongly. 
Carminic  acid  is  a  feeble  acid.  The  composition  of  the  substance,  dried 
at  120°  C.  (248°  F.),  is  represented  by  C14HU08,  which  formula  is  corrobo- 
rated by  the  analysis  of  a  copper  compound,  2C14H14Og.  CuO. 

By  the  action  of  nitric  acid  upon  carminic  acid,  there  is  formed,  together 
with  oxalic  acid,  a  splendid  nitrogenetted  acid,  crystallizing  in  yellow 
rhombic  plates.  This  substance,  to  which  the  name  nitrococcusic  acid  was 
given,  is  bibasic :  it  contains  C8H5N309.  It  is  soluble  in  cold,  more  so  in 
boiling  water,  and  readily  soluble  in  alcohol  and  ether.  Nitrococcusic 
acid  is  evidently  derived  from  a  non-nitrogenous  compound  in  which  part 
of  the  hydrogen  is  replaced  by  N02.  Like  all  substances  of  this  class,  it 
explodes  when  heated. 

In  the  mother-liquor,  from  which  the  carminic  acid  has  been  separated, 
De  La  Rue  discovered  a  white,  crystalline,  nitrogenous  substance,  for  which 
he  established  the  formula  C8H,,N03.  This  substance  is  identical  with 
tyrosine,  which  will  be  mentioned  in  the  section  on  Animal  Chemistry. 

Madder.  — The  root  of  the  Rubia  tinctorum,  cultivated  in  southern  France, 
the  Levant,  &c.,  is  the  most  permanent  and  valuable  of  the  red  dye-stuifs. 
In  addition  to  several  yellow  coloring  matters,  which  are  of  little  impor- 
tance for  tho  purposes  of  the  dyer,  madder  contains  two  red  pigments, 
which  are  called  alizarin  and  purpurin.  These  substances  have  been  the 

*  Memoirs  of  the  Chemical  Society,  vol.  iii.  p.  454. 


788  ORGANIC   COLORING   PRINCIPLES. 

subject  of  very  extensive  researches  by  Debus,  Higgins,  and  especially 
Schunck.  The  latest  papers  on  madder  have  been  published  by  Wolff  and 
Strecker,  whose  formulae  are  quoted  in  the  following  abstract : 

ALIZARIN. — The  aqueous  decoction  of  madder  is  precipitated  by  sul- 
phuric acid,  and  the  precipitate  washed  and  boiled  with  aluminium  chlo- 
ride, which  dissolves  the  red  pigments,  an  insoluble  brownish  residue  re- 
maining behind.  The  solution,  when  mixed  with  hydrochloric  acid,  yields 
a  precipitate  consisting  chiefly  of  alizarin  —  still,  however,  contaminated 
with  purpurin.  The  impure  alizarin  thus  obtained  may  be  further  purified 
by  again  throwing  down  the  alcoholic  solution  with  aluminium  hydrate,  and 
boiling  the  precipitate  with  a  concentrated  solution  of  soda,  which  leaves 
a  pure  compound  of  alumina  and  alizarin  behind.  From  this  the  alizarin 
is  separated  by  hydrochloric  acid  and  recrystallized  from  alcohol.  Pure 
alizarin  crystallizes  in  splendid  red  prisms,  which  may  be  sublimed.  It  is 
but  slightly  soluble  in  water  and  in  alcohol,  but  dissolves  in  concentrated 
sulphuric  acid  with  a  deep  red  color.  On  addition  of  water,  the  coloring  mat- 
ter is  reprecipitated  unchanged.  It  is  also  soluble  in  alkaline  liquids,  to  which 
it  imparts  a  magnificent  purple  color.  It  is  insoluble  in  cold  solution  of 
alum.  Alizarin  is  the  chief  coloring  matter  of  madder:  it  contains  C,0H6 
03 .  2H20,*  and  is  a  feeble  acid:  a  few  definite  compounds  with  mineral 
oxides  have  been  prepared,  among  which  a  lime  compound,  4C,0H603 . 
3CaH202,  may  be  mentioned.  The  action  of  nitric  acid  upon  alizarin  gives 
rise  to  the  formation  of  oxalic  acid  and  phthalic  acid  (p.  666) : 

ClpH603    +     H20     +     0,     =     C2H204      +      C8H,04    ^ 
Alizarin.  Phthalic  acid. 

PURPURIN.  —  Madder  is  allowed  to  ferment  and  then  boiled  with  a  strong 
solution  of  alum.  The  solution,  when  mixed  with  sulphuric  acid,  yields  a 
red  precipitate,  which  is  purified  by  re-crystallization  from  alcohol.  Pur- 
purin thus  obtained  crystallizes  in  red  needles,  which  contain  C9H603 .  H20, 
i.  e.,  one  atom  of  carbon  less  than  alizarin.  When  treated  with  nitric  acid, 
purpurin,  like  alizarin,  furnishes  oxalic  and  phthalic  acids.  Purpurin 
likewise  contributes  to  the  tinctorial  properties  of  madder,  but  less  so  than 
alizarin.  Together  with  alizarin  and  purpurin,  several  other  substances 
occur  in  madder,  among  which  may  be  noticed  an  orange  pigment,  rubiacin, 
convertible  by  oxidizing  agents  into  a  peculiar  acid,  rubiacic  acid,  a  yellow 
pigment,  xanthin,  a  bitter  principle,  rabian,  sugar,  pectic  acid,  and  several 
resins,  &c. 

Garancin  is  a  coloring  material,  which  is  produced  by  the  action  of  sul- 
phuric acid  upon  madder.  This  substance  possesses  a  higher  tinctorial 
power  than  madder  itself. 

The  beautiful  Turkey-red  of  cotton  cloth  is  a  madder  color;  it  is  given 
by  a  very  complicated  process,  the  theory  of  which  is  not  yet  perfectly 
elucidated. 

Safflower.  —  This  substance  contains  a  yellow  and  a  red  coloring  matter, 
the  latter  being  insoluble  in  water,  but  soluble  in  alkaline  liquids.  The 
safflower  may  be  exhausted  with  water  acidulated  with  acetic  acid,  and  the 
solution  mixed  with  lead  acetate,  and  filtered  from  the  dark-colored  impure 
precipitate.  The  lead  compound  of  the  yellow  pigment  may  then  be  thrown 
down  by  addition  of  ammonia  and  decomposed  by  sulphuric  acid.  In  its 
purest  form  the  yellow  matter  constitutes  a  deep  yellow,  uncrystallizable, 
and  very  soluble  substance,  very  prone  to  oxidation.  In  its  lead-compound 
it  has  probably  the  composition  C24H240,3. 

The  red  matter,  or  carthamin,  is  obtained  from  the  residual  safflower  by 
a  dilute  solution  of  sodium  carbonate;  pieces  of  cotton-wool  are  immersed 

*  According  to  Schunck,  the  formula  of  alizarin  is  Ci4Hi004. 


as 


ALOES.  789 

in  the  liquid,  and  acetic  acid  gradually  added.  The  dried  cotton  is  then 
digested  in  a  fresh  quantity  of  the  alkaline  solution,  and  the  liquid  supersatu- 
rated with  citric  acid,  which  throws  down  the  carthamin  in  carinine-red  flocks. 
It  forms,  when  pure  and  dry,  an  amorphous,  brilliant,  green  powder,  nearly 
insoluble  in  water,  but  soluble  in  alcohol  with  splendid  purple  color.  It 
contains  CUH,607. 

Brazil-wood  and  Logwood  give  red  and  purple  infusions,  which  are  largely 
used  in  dyeing:  the  coloring  principle  of  logwood  is  termed  hematoxylin, 
and  has  been  obtained  in  crystals.  This  substance  contains  C,6H,406.  Acids 
brighten  these  colors,  and  alkalies  render  them  purple  or  blue. 

Among  yellow  dyes,  quercitron  bark,  fustic-wood,  and  saffron  may  be  men- 
tioned, and  also  turmeric :  these  all  give  yellow  infusions  to  water,  and  fur- 
nish more  or  less  permanent  colors. 

Purree  or  Indian  yellow,  a  body  of  unknown  origin,  used  in  water-color 
painting,  is,  according  to  the  researches  of  Stenhouse  and  Erdmann,  a 
compound  of  magnesia  with  a  substance  termed  purreic  or  euxanthic  acid. 
The  latter,  when  pure,  crystallizes  in  nearly  colorless  needles,  sparingly 
soluble  in  cold  water,  and  of  sweetish-bitter  taste.  It  forms  yellow  com- 
pounds with  the  alkalies  and  earths,  and  is  decomposed  by  heat,  with  pro- 
duction of  a  neutral  crystalline  sublimate,  purrenone  or  euxanthone.  Purreic 
acid  contains  C^H^O^,  purrenone  C20H1206.  By  the  action  of  chlorine, 
bromine,  and  nitric  acid,  a  series  of  substitution-products  are  formed. 

Frangulin,  C6H603,  from  Rhamnus  frangula,  has  been  already  mentioned 
i  a  triatomic  phenol  (p.  571). 

Morindin,  C2gH30016,  is  a  yellow  crystalline  coloring  matter,  occurring  in 
the  root  of  Morinda  citrifolia,  called  Soranjee  in  the  East  Indies.  When 
heated  it  is  converted  into  a  beautiful  crystalline  body,  morindone,  contain- 
ing C14H1006. 

Aloes.  —  Certain  of  the  products  of  the  action  of  nitric  acid  upon  aloes, 
very  much  resemble  some  of  the  derivatives  of  indigo,  without,  however, 
it  seems,  being  identical  with  them.  Powdered  aloes,  heated  for  a  consid- 
erable time  with  excess  of  moderately  strong  nitric  acid,  yields  a  deep-red 
solution,  which,  on  cooling,  deposits  a  yellow  crystalline  mass.  This,  puri- 
fied by  suitable  means,  constitutes  chrysammic  acid:  it  crystallizes  in  golden- 
yellow  scales,  which  have  a  bitter  taste,  and  are  but  sparingly  soluble  in 
water.  Its  potassium-salt  has  a  carmine-red  tint,  and  exhibits  a  green  me- 
tallic lustre,  like  that  of  murexide.  The  formula  of  chrysammic  acid  is 
not  perfectly  established.  It  is  probably  C7H2N206  or  C7H2(N02)202.  Like 
picric  acid,  it  yields,  with  chloride  of  lime,  chloropicrin.  The  mother- 
liquor,  from  which  the  chrysammic  acid  has  been  deposited,  contains  a 
second  acid,  the  chrysolepic,  which  also  forms  golden-yellow,  sparingly  sol- 
uble, scaly  crystals.  The  potassium-salt  forms  small,  yellow  prisms,  of 
little  solubility.  It  explodes  by  heat.  Chrysolepic  acid  contains  C6H3N307 : 
it  is  said  to  be  identical  with  picric  acid. 

To  these  may  be  added  the  sti/phnic,  or  oxypicric  acid,  described  by  Bott- 
ger  and  Will,  produced  by  the  action  of  nitric  acid  of  sp.  gr.  1-2  upon  assa- 
j'lrtidn  and  several  other  gum-resins  and  extracts.  Brazil-wood  and  purree, 
when  treated  with  excess  of  nitric  acid,  likewise  yield  styphnic  acid.  It 
crystallizes,  when  pure,  in  slender,  yellowish-white  prisms,  sparingly  sol- 
uble in  water,  readily  dissolved  in  alcohol  and  ether.  It  has  a  purely 
astringent  taste,  and  stains  the  skin  yellow.  By  a  gentle  heat  it  melts, 
and  on  cooling  becomes  crystalline  ;  suddenly  and  strongly  heated  it  burns 
like  gun-powder.  It  also  yields  chloropicrin.  The  salts  of  this  substance 
mostly  crystallize  in  orange-yellow  needles,  and  explode  with  great  violence 
by  heat.  Styphnic  acid  contains  C6H3N308,  i.  e.,  picric  acid  -f  1  atom  of 
oxygen. 


790  RESINS   AND   BALSAMS. 


KESINS  AND  BALSAMS. 

Common  resin,  or  colophony,  furnishes  perhaps  the  best  example  of  the 
class.  It  is  the  resinous  substance  which  remains  when  turpentine  or  pine 
resin  is  heated  till  the  water  and  volatile  oil  are  expelled,  and  is  a  mixture 
of  two  distinct  bodies  having  acid  properties  :  viz.,  abietic  acid,  C44H6405, 
which  is  crystallizable,  and  pinic  acid,  C^H^O^  which  is  amorphous.  These 
acids  may  be  separated  from  each  other  by  their  difference  of  solubility  in 
cold  and  somewhat  dilute  alcohol,  the  latter  being  by  far  the  more  soluble 
of  the  two.  Pure  abietic  acid  crystallizes  in  small,  colorless,  rhombic 
prisms,  insoluble  in  water,  soluble  in  hot  strong  alcohol,  in  volatile  oils, 
and  in  ether.  It  melts  when  heated,  but  cannot  be  distilled  without  de- 
composition. An  alcoholic  solution  of  abietic  acid,  precipitated  by  sul- 
phuric acid,  yields  another  crystalline  acid  called  sylvic  acid,  isomeric  with 
pinic  acid.  A  fourth  resin-acid,  called  pimaric  acid,  also  isomeric  with  pinic 
acid,  has  been  found  in  the  turpentine  of  the  Firms  maritima  of  Bordeaux. 

Lac  is  a  very  valuable  resin,  much  harder  than  colophony,  and  easily 
soluble  in  alcohol:  three  varieties  are  known  in  commerce  —  viz.,  slick-lac, 
seed  lac,  and  shellac.  It  is  used  in  varnishes,  and  in  the  manufacture  of 
hats,  and  very  largely  in  the  preparation  of  sealing-wax,  of  which  it  forms 
the  chief  ingredient.  Crude  lac  contains  a  red  dye  called  lac-dye,  which  is 
partly  soluble  in  water.  Lac  dissolves  in  considerable  quantity  in  a  hot 
solution  of  borax ;  Indian  ink,  rubbed  up  with  this  liquid,  forms  a  most 
excellent  label-ink  for  the  laboratory,  as  it  is  unaffected  by  acid  vapors,  and, 
when  once  dry,  becomes  nearly  insoluble  in  water. 

Mastic,  dammar-resin,  and  sandarac  are  resins  largely  used  by  the  varnish- 
maker.  Dragon's  blood  is  a  resin  of  deep-red  color.  Copal  is  also  a  very 
valuable  substance  :  it  differs  from  the  other  resins  in  being  but  slowly  dis- 
solved by  alcohol  and  essential  oils.  It  is  miscible,  however,  in  the  melted 
state  with  oils,  and  is  thus  made  into  varnish.  Amber  appears  to  be  a  fossil 
resin ;  it  is  found  accompanying  brown-coal  or  lignite.  Caoutchouc  and 
guttapercha  have  been  already  described  as  terpenes  (p.  492). 

Most  of  the  resins,  when  exposed  to  destructive  distillation,  yield  oily 
pyro-products,  usually  of  hydrocarbons,  which  have  been  studied  with 
partial  success.  Great  difficulties  occur  in  these  investigations:  the  task 
of  separating  from  each  other,  and  isolating  bodies  which  scarcely  differ 
but  in  their  boiling  points,  is  exceedingly  troublesome. 

Balsams  are  natural  mixtures  of  resins  with  volatile  oils.  They  differ 
very  greatly  in  consistence,  some  being  quite  fluid,  others  solid  and  brittle. 
By  keeping,  the  softer  kinds  often  become  hard.  Balsams  may  be  con- 
veniently divided  into  two  classes  —  viz.,  those  which,  like  common  and 
Venice  turpentine,  Canada  balsam,  Copaiba  balsam,  &c.,  are  nearly  natural 
varnishes,  or  solutions  of  resins  in  volatile  oils,  and  those  which  contain 
benzoic  or  cinnamic  acid  in  addition,  as  Peru  and  Tolu  balsams,  and  the 
solid  resinous  benzoin,  commonly  called  gum-benzoin. 

Tolu-balsam,  by  distillation  with  water,  yields  three  products  —  namely, 
benzoic  acid,  cinnamein,  or  styracin,  Ci6H4402  (p.  641),  and  tolene,  a  vola- 
tile, colorless  hydrocarbon,  boiling  at  170°  C.  (338°  F.),  and  containing 
C,2H,8,  or,  according  to  some  authorities,  C10H,6.  The  balsam  freed  in  this 
manner  from  essential  oils,  and  exposed  to  destructive  distillation,  yields 
in  succession  a  viscous  liquid,  which  crystallizes  in  the  receiver,  and  a  thin 
liquid  heavier  than  water ;  carbon  dioxide  and  carbon  monoxide  are  largely 
evolved,  and  the  retort  is  afterwards  found  to  contain  a  residue  of  charcoal. 
The  solid  product  is  chiefly  a  mixture  of  benzoic  and  cinnamic  acids :  the 
volatile  oil  contains  at  least  two  substances  differing  in  their  boiling  points, 
and  are  easily  separated  —  namely,  toluene  (p.  495),  and  an  oily  liquid 


RESINS   AND   BALSAMS.  791 

heavier  than  water,  of  high  boiling  point,  and  having  the  composition  and 
characters  of  benzoic  ether. 

Liquid  storax,  distilled  with  water  holding  in  solution  a  little  sodium  car- 
bonate, yields  a  small  and  variable  quantity  of  volatile  oil,  not  homogeneous, 
but  from  which,  by  careful  distillation,  pure  cinnamene  or  styrolene,  C8H8 
(p.  501),  may  be  extracted. 

Storax,  from  which  the  styrol  has  been  separated  by  distillation,  when 
treated  with  sodium  carbonate,  yields  a  considerable  quantity  of  sodium 
cinnamate.  The  residue  consists  of  resinous  bodies,  associated  with  styra- 
cin  or  cinnyl  cinnamate  (p.  641). 


PART  IV. 

ANIMAL   CHEMISTRY. 


INTRODUCTION. 

ANIMAL  CHEMISTRY,  for  the  purpose  of  clearness,  may  fee  divided 
into  the  chemistry  of  separate  substances  entering  into  the  composi- 
tion of  the  fluids  and  solids  of  animals,  the  chemistry  of  the  complex  ani- 
mal fluids  and  textures,  and  the  chemistry  of  the  processes  which  take 
place  in  the  animal  body. 

This  classification  has  a  great  many  advantages,  and  in  the  following 
brief  abstract  the  subject  will  be  considered  under  these  different  heads. 

Many  animal  substances  have  been  already  fully  mentioned  in  the  inor- 
ganic part  of  this  work :  for  example,  water,  carbonic  acid,  and  calcium 
phosphate ;  the  other  animal  substances,  as  urea,  formic,  and  hippuric 
acid,  have  been  placed  in  the  organic  part,  because,  from  their  composi- 
tion, relations,  and  properties,  they  could  not  be  separated  from  many 
bodies  which  are  not  connected  with  animal  chemistry.  As  the  chemical 
knowledge  of  other  animal  substances  is  perfected,  these  also  will  be  placed 
under  the  head  of  organic  chemistry  ;  and  thus  animal  chemistry  will  ulti- 
mately embrace  the  knowledge  of  the  composition  and  properties  of  the 
complex  fluids  and  textures  of  the  body,  and  of  the  chemical  actions  re- 
sulting from  the  air  and  food  which  are  requisite  for  the  support  of  ani- 
mal life. 

Although  animal  chemistry  has  hitherto  occupied  the  attention  of  nearly 
every  great  chemist,  yet  comparatively  much  remains  to  be  done  and  to  be 
undone.  For  example,  the  very  different  substances  which  are  included 
under  the  term  protein-principles,  that  is,  of  which  protein  is  the  first  pro- 
duct of  decomposition  and  ammonia  carbonate  the  last,  can  scarcely  yet  be 
arranged  according  to  their  percentage-composition,  much  less  be  repre- 
sented truly  by  any  formulae.  The  chemical  composition  of  the  different 
organs  and  textures  of  the  body,  of  the  brain  or  blood,  for  instance,  or 
even  of  the  bones,  is  differently  given,  according  as  this  or  that  method  of 
analysis  is  followed.  The  same  may  be  said  of  the  secretions  and  excre- 
tions ;  and  these  vary  so  much  at  different  times,  in  different  persons,  and 
in  different  classes  of  animals,  that  no  single  standard  of  comparison  can 
be  adopted ;  but  the  highest  and  lowest  limits  of  composition  for  health 
and  disease  must  be  regarded,  and  not  the  mean  of  a  number  of  analyses. 
A  still  more  difficult  problem  is  presented  to  the  chemist  in  the  investi- 
gation of  the  processes  which  take  place  in  the  bodies  of  animals  and  vege- 
tables. The  solution  of  the  food  by  the  action  of  alkalies,  acids,  and  fer- 
ments ;  the  nutrition  of  the  organs  by  the  blood ;  the  production  of  animal 
heat  by  the  action  of  inspired  oxygen ;  and  the  removal  from  the  body 
of  the  substances  that  have  been  used  or  are  useless  or  injurious ;  — these 
are  questions  which  in  future  years  will  form  the  chief  subjects  of  investi- 
gation in  animal  chemistry,  whilst  in  vegetable  chemistry  the  influence  of 
sunlight  in  promoting  the  formation  of  the  innumerable  compounds  of  car- 
bon will  have  to  be  determined. 

792 


ON  SEPARATE  SUBSTANCES   ENTERING  INTO  THE  COMPOSITION 
OF  THE  FLUIDS  AND  SOLIDS  OF  ANIMALS. 


ALBUMINOUS  PRINCIPLES. 

ALTHOUGH,  in  the  present  state  of  our  knowledge,  no  chemical  dis- 
tinction exists  between  vegetable  and  animal  substances,  and  although 
many  mineral  substances  always  exist  in  the  fluids  and  solids  of  ani- 
mals and  vegetables,  yet  there  is  a  class  of  substances  which  formerly 
were  considered  as  exclusively  animal,  and  of  these  we  still  know  so  little 
that  it  is  most  convenient  still  to  keep  them  distinct  from  other  organic 
substances.  They  form  the  chief  part  of  the  solid  constituents  of  the 
blood,  muscles,  nerves,  glands,  and  other  organs  of  animals,  and  they  occur 
in  small  quantities  in  almost  every  part  of  vegetables.  Their  atomic 
weight  and  constitution  are  still  unknown,  and  only  slight  differences  exist 
in  the  percentage  composition  ;  thus : 

C  52,7  to  54,5 

H  6,9  «  7,3 

N  15,4  «  16,5 

0  20,9  «  23,5 

S  0,8  «  1,6 

They  are  amorphous,  more  or  less  soluble  in  water,  soluble  in  excess  of 
acetic  acid,  more  soluble  in  alkalies,  almost  insoluble  in  alcohol,  and  quite 
so  in  ether.  Strong  mineral  acids  dissolve  all  albuminous  substances.  The 
hydrochloric  acid  solution  is  first  blue,  then  violet,  then  brown.  The  nitric 
acid  solution  is  yellow,  and  gives  rise  to  xanlhoproteic  acid,  which  dissolves 
in  alkalies  and  ammonia  with  orange-red  color.  Caustic  alkalies  decom- 
pose albuminous  substances  according  to  the  temperature,  giving  rise  to 
leucine,  tyrosine,  oxalic  acid,  carbonic  acid,  and  ammonia. 

Albuminous  substances  are  precipitated  from  solutions:  1.  By  excess  of 
mineral  acids.  2.  By  potassium  ferrocyanide  with  acetic  acid  or  a  little 
hydrochloric  acid.  3.  By  acetic  acid,  with  a  considerable  quantity  of  con- 
centrated solutions  of  neutral  salts  of  alkalies  and  alkaline  earths,  gum 
arabic,  or  dextrin  When  examined  for  circular  polarization,  they  rotate 
the  light  more  or  less  to  the  left. 

SERUM  ALBUMIN  is  the  most  abundant  albuminous  substance  in  animal 
bodies.  It  can  be  obtained  tolerably  pure  from  blood-serum  by  precipita- 
tion with  lead  acetate,  washing  with  water,  suspending  the  precipitated 
lead  compound  in  water,  and  decomposing  it  with  carbonic  acid ;  then,  by 
filtration,  a  very  cloudy  solution  of  albumin  is  obtained.  It  forms  a  yel- 
low, elastic,  transparent  substance,  which  when  perfectly  dry  can  be  heated 
to  100°  without  change.  It  is  soluble  in  water  and  precipitable  by  alcohol; 
long  continued  action  of  alcohol  changes  it  into  coagulated  albumin.  Se- 
rum albumin  is  not  precipitated  by  carbonic,  acetic,  tartaric,  or  phos- 
phoric acid;  when  mixed  with  a  very  small  quantity  of  other  vory  weak 
67  793 


794:  ALBUMINOUS    PKINCIPLES. 

mineral  acids,  it  is  not  precipitated ;  by  large  quantities  of  acid  it  is  .im- 
mediately precipitated;  nitric  acid  acts  most  strongly.  The  precipitate 
with  strong  hydrochloric  acid  dissolves  in  an  excess  of  acid;  and  on  add- 
ing water  to  this  solution,  a  precipitate  forms,  which,  after  filtration  and 
squeezing,  dissolves  in  water  and  has  all  the  reactions  of  hydrochloride  of 
syntonin  ;  caustic  potash  and  soda-solution  change  the  serum  albumin  into 
compounds  of  albumin  with  the  alkali. 

When  heated  to  72°  or  73°  C.  (163°  F.),  blood-serum  coagulates  into  a 
compact  mass.  The  fluid  begins  to  be  cloudy  at  60°  C.  (140°  F.).  Coagu- 
lation occurs  at  a  lower  temperature  when  very  dilute  phosphoric  or 
acetic  acid  is  added,  or  neutral  salts  in  small  quantity,  and  at  a  higher 
temperature  with  a  very  little  sodium  carbonate. 

Serum  albumin  is  precipitated  from  its  solutions  by  most  of  the  salts  of 
the  heavy  metals.  When  agitated  with  ether  it  does  not  coagulate. 

EGG  ALBUMIN  differs  from  serum  albumin  by  gradually  giving  a  precipi- 
tate when  agitated  with  ether ;  oil  of  turpentine  also  coagulates  this  kind 
of  albumin.  Serum  albumin  dissolves  easily  in  strong  nitric  acid,  whilst 
egg  albumin  scarcely  dissolves  at  all.  When  a  solution  of  egg  albumin  is 
injected  into  the  veins  or  under  the  skin  of  dogs  or  rabbits,  the  egg  albu- 
min passes  unchanged  into  the  urine,  whilst  serum  albumin,  injected  in  the 
same  way,  does  not  pass  into  the  urine  at  all. 

When  white  of  egg  is  thinly  spread  upon  a  plate  and  exposed  to  evapo- 
ration in  a  warm  place,  it  dries  up  to  a  pale-yellow,  brilliant,  gum-like 
substance  destitute  of  all  traces  of  crystalline  structure.  In  this  state  it 
may  be  preserved  unchanged  for  any  length  of  time,  the  presence  of  Avater 
being  in  all  cases  necessary  to  putrefactive  decomposition.  The  watery 
solutions  of  egg  albumin  and  serum  albumin  coagulate  at  the  same  tempera- 
ture under  similar  circumstances.  The  existence  of  unoxidized  sulphur  in 
albumin  is  easily  shown;  a  boiled  egg  blackens  a  silver  spoon,  from  a  trace 
of  alkaline  sulphide  formed  or  separated  during  the  coagulation ;  and  a 
solution  of  albumin  in  excess  of  caustic  potash  mixed  with  a  little  acetate 
of  lead,  gives,  on  boiling,  a  black  precipitate  containing  sulphide  of  lead. 

CASEIN;  AND  ALBUMINATE  OR  PROTEIN.  —  Albuminous  substances,  when 
treated  with  solution  of  potash,  undergo  more  or  less  change  according  to 
the  strength  of  the  potash  and  the  temperature  at  which  the  action  takes 
place.  Sometimes  bodies  can  be  produced  which  agree  Avell  together,  and 
cannot  be  distinguished  from  the  casein  of  milk,  although  most  probably 
casein  is  not  identical  with  artificial  albuminate,  and  the  bodies  which  are 
produced  by  the  action  of  potash  on  different  albuminous  substances  may 
differ  slightly  one  from  the  other,  as  is  evident  in  the  difference  of  their 
rotatory  action  on  polarized  light. 

Casein  occurs  most  plentifully  in  the  milk  of  animal  feeders.  In  the 
fluids  of  the  textures  it  has  certainly  not  been  found.  In  the  blood  it  is 
entirely  absent,  and  it  is  rarely  present  in  the  fluid  of  cysts. 

It  is  best  obtained  from  milk  by  precipitating  it  with  crystalline  magne- 
sium sulphate,  filtering  and  washing  with  a  concentrated  solution  of  Epsom 
salt,  then  dissolving  the  precipitate  in  water ;  the  butter  is  filtered  oft',  and 
the  clear  solution  precipitated  by  dilute  acetic  acid. 

For  preparing  protein  or  potassium  albuminate,  any  albuminous  sub- 
stance may  be  used.  Lieberkiihn  directs  egg  albumin  to  be  stirred  with 
an  equal  volume  of  water  and  filtered;  the  filtrate  to  be  reduced  to  one- 
half  in  shallow  vessels  at  40°  C.  (104°  F.),  and,  after  cooling,  to  be  mixed 
with  concentrated  potash  drop  by  drop  until  the  whole  substance  sets  to  a 
strong  transparent  jelly.  This  is  cut  into  pieces  of  the  size  of  a  bean,  and 
thrown  into  much  distilled  water;  after  being  stirred,  the  water  is  youred 
off  from  the  albuminate.  The  washing  is  repeated  as  long  as  any  alkaline 


PARALBUMIN — SYNTONIN.  795 

reaction  remains.  The  purified  albuminate  is  then  dissolved  in  boiling 
water  or  spirits  of  wine,  in  which  it  ought  to  give  a  clear  solution. 

An  albuminate  is  more  simply  obtained  by  shaking  milk  with  caustic 
soda  and  ether,  pouring  off  the  clear  alkaline  lower  layer  of  fluid,  precipi- 
tating it  with  acetic  acid,  and  washing  it  with  water. 

The  dried  casein  and  albuminate  are  yellow,  transparent,  and  hygro- 
scopic, swelling  up  in  water,  but  not  dissolving.  When  precipitated  in  a 
flocky  state,  they  dissolve  easily  in  water  if  it  contains  a  little  alkali.  The 
precipitate  which  forms  on  neutralizing  the  alkaline  solution,  dissolves 
easily  in  an  excess  of  acetic  acid  or  dilute  hydrochloric  acid.  On  the  ad- 
dition of  an  excess  of  mineral  acid,  or  by  neutralizing  with  an  alkali,  these 
solutions  give  a  precipitate. 

The  neutral  or  feebly  alkaline  albuminate  and  casein  in  alkaline  solution, 
are  precipitated  in  the  cold  by  alcohol :  when  hot  they  are  dissolved.  Al- 
buminates  are  precipitated  by  copper  sulphate,  silver  nitrate,  and  barium 
chloride.  Lieberkiihn  gives  as  their  formula  C72H112R.2N18023S,  R  denoting 
an  atom  of  univalent  metal.  According  to  him,  potassium  albuminate  has 
the  same  composition.  Meissner  says  that  by  boiling  casein  continuously, 
lactic  acid  and  creatin  are  formed. 

By  fusion  with  potassium  hydrate,  casein  yields  valeric  and  butyric  acids, 
besides  other  products. 

The  most  striking  property  of  casein  is  its  coagulability  by  certain  animal 
membranes.  This  is  well  seen,  in  the  process  of  cheeseinaking,  in  prepar- 
ing the  curd.  A  piece  of  the  stomach  of  the  calf,  with  its  mucous  membrane, 
is  slightly  washed,  put  into  a  large  quantity  of  milk,  and  the  whole  slowly 
heated  to  about  53°  C.  (124°  F.).  In  a  short  time  after  this  temperature 
has  been  attained,  the  milk  is  observed  to  separate  into  a  solid,  white  co- 
agulum,  or  mass  of  curd,  and  a  yellowish,  translucent  liquid  called  whey. 
The  curd  contains  all  the  casein  of  the  milk,  much  of  the  fat,  and  much  of 
the  inorganic  matter:  the  whey  retains  the  milk-sugar  and  the  soluble 
salts.  It  is  just  possible  that  this  mysterious  change  may  be  really  duo  to 
the  formation  of  a  little  lactic  acid  from  the  milk-sugar,  under  the  joint 
influence  of  a  slowly  decomposing  membrane  and  the  elevated  temperature, 
and  that  this  acid  may  be  sufficient  in  quantity  to  withdraw  the  alkali 
which  holds  the  casein  in  solution,  and  thus  occasion  its  precipitation  in 
•the  insoluble  state.  The  loss  of  weight  the  membrane  itself  suffers  in  this 
operation  is  very  small :  it  has  been  found  not  to  exceed  TfL7  part. 

PARALBUMIN  has  as  yet  been  found  only  in  ovarian  cysts,  and  it  rarely 
occurs  alone.  It  is  precipitated  by  alcohol,  but  still  contains  some  alkali. 
It  is  coagulated  by  boiling,  but  cannot  be  filtered.  When  it  is  dissolved  in 
much  water,  and  carbonic  acid  gas  is  passed  through  it,  a  plentiful  flocky 
precipitate  falls;  acetic  acid  carefully  added  acts  still  better.  The  pre- 
cipitate is  easily  soluble  in  an  excess  of  acetic  acid,  or  in  a  very  weak  solu- 
tion of  alkali.  By  the  addition  of  magnesium  sulphate  it  is  not  precipitated 
from  a  feeble  alkaline  solution.  It  gives  a  precipitate  with  acetic  acid  and 
potassium  ferrocyanide,  lead  acetate,  alum,  and  copper  sulphate.  The 
composition  of  this  albuminous  substance  is  stated  by  Haerlin  to  be  51  -8 
carbon,  6-9  hydrogen,  12-8  nitrogen,  26  8  oxygen,  and  1-7  sulphur. 

SYNTONIN  or  PARAPEPTONE.  — As  by  the  action  of  alkalies  on  albuminous 
matters  the  albuminates  are  produced,  so  by  treating  these  with  strong 
hydrochloric  acid,  syntonin  is  formed  among  other  products  of  decomposi- 
tion. Probably  the  shorter  the  time  the  acid  is  in  action,  the  more  synto- 
nin is  formed.  It  is  also  formed  from  other  albuminous  substances,  most 
easily  from  myosin,  as  in  the  first  action  of  the  gastric  juice  in  the  stomach. 
For  preparing  syntonin,  fresh-cut  meat  is  treated  with  cold  water,  ami  the 
residue  is  mixed  with  water  containing  T^  hydrochloric  acid ;  a  thick- 


796  ANIMAL    SUBSTANCES. 

ish  solution  is  thus  obtained  which  can  be  filtered.  The  clear  liquid  is  care- 
fully neutralized  with  sodium  carbonate,  which  gives  a  gelatinous  precipi- 
tate of  syntonin ;  this  is  purified  by  washing  with  water,  alcohol,  and  ether. 
It  contains  much  unaltered  myosin.  From  fibrin,  serum  albumin,  or  any 
other  albuminous  matter,  except  uncoagulated  egg  albumin,  syntonin  may 
be  obtained  by  dissolving  them  in  fuming  hydrochloric  acid,  filtering,  and 
precipitating  the  filtrate  with  twice  its  volume  of  water  ;  the  precipitate  is 
filtered  olf,  dissolved  in  water,  and  precipitated  by  careful  neutralization 
with  sodium  carbonate. 

The  composition  of  syntonin  is  54-1  carbon,  7-3  hydrogen,  16-1  nitrogen, 
21-5  oxygen,  and  1-1  sulphur.  It  is  insoluble  in  solution  of  sodium  chlo- 
ride, whatever  its  concentration ;  easily  soluble  in  dilute  hydrochloric  acid, 
and  in  feebly  alkaline  liquids.  The  solution  in  lime-water  is  partially 
coagulated  by  boiling.  When  the  solution  is  boiled,  sodium  chloride,  mag- 
nesium sulphate,  or  calcium  chloride,  gives  a  precipitate  as  with  many 
other  albuminous  substances.  Syntonin,  like  casein,  when  dissolved  in 
very  dilute  hydrochloric  acid,  gives  a  precipitate  with  neutral  potassium- 
salts  at  ordinary  temperatures.  By  the  action  of  strong  hydrochloric  acid 
on  uncoagulated  albumin,  an  albuminous  substance  is  first  obtained,  which 
is  scarcely  soluble  in  water,  and  is  also  very  slightly  soluble  in  dilute  hydro- 
chloric acid. 

MYOSIN  was  first  separated  by  Kiihne  from  other  albuminous  matters  oc- 
curring in  the  protoplasma  or  contractile  muscular  substance  that  causes 
the  rigor  mortis.  To  prepare  it  well,  cut-up  flesh  is  carefully  washed  with 
water,  and  the  mass  is  then  placed  in  a  mixture  of  one  volume  of  concen- 
trated solution  of  common  salt  to  two  volumes  of  water ;  these  are  contin- 
ually rubbed  together  and  filtered  through  linen ;  the  slimy  filtrate  is 
allowed  to  drop  into  much  distilled  water.  The  myosin  is  re-dissolved  in 
solution  of  sodium  chloride,  and  re-precipitated  by  much  water.  It  is  in- 
soluble in  water,  soluble  in  solution  of  common  salt  under  10°,  soluble  in 
very  dilute  hydrochloric  acid,  but  in  this  solution  it  passes  by  degrees  into 
syntonin ;  in  dilute  alkali,  myosin,  like  other  albuminous  matter,  is  soluble, 
being  changed  into  albuminate.  By  heat  it  is  changed  into  coagulated  al- 
bumin. It  is  also  coagulated  by  alcohol.  The  substances  which  occur  in 
yolk  of  egg,  the  crystalline  lens,  and  the  fluid  from  some  cysts,  soluble  in 
concentrated  solutions  of  common  salt,  but  not  soluble  in  water,  have  been 
considered  by  Denis  as  identical  with  myosin,  called  by  him  globulin. 

FlBRINO-PLASTIC  SUBSTANCE  and  FlBRINOQEN,   Or  PARAGLOBULIN,  Or  PAR- 

AGLOBIN. — Alexander  Schmidt  has  found  that  fibrin  is  formed  by  the  con- 
tact of  two  albuminous  matters.  One  he  calls  fibrinoplastic  and  the  other 
fibrinogenous  substance.  The  first  is  especially  plentiful  in  the  red  blood- 
globules,  in  the  serum  of  the  blood,  the  cellular  tissue,  and  the  cornea. 
The  second  is  found  in  exudations,  specially  in  the  pericardium  and  fluid 
of  hydrocele,  in  lymph  and  chyle.  In  their  reactions  they  nearly  resemble 
myosin,  being  soluble  in  a  solution  of  common  salt,  and  precipitable  by  an 
excess  of  it.  They  dissolve  in  very  dilute  hydrochloric  acid,  and,  by  keep- 
ing, change  into  a  syntonin-like  substance;  soluble  also  in  very  feeble 
alkaline  solutions,  from  which  the  fibrinoplastic  substance  is  more  easily 
precipitated  than  the  fibrinogenic  by  carbonic  acid.  When  these  two  sub- 
stances come  into  contact  in  any  fluid,  they  combine,  quickly  or  slowly, 
according  to  the  greater  or  less  quantity  of  each  substance  in  the  fluid,  to 
form  Fibrin.  The  fluid  coagulates  either  to  a  mass  of  jelly,  or,  when  very 
little  is  present,  the  fibrin  forms  in  separate  flocks.  The  coagulation  takes 
place  more  quickly  at  a  high  temperature,  more  slowly  at  a  low  tempera- 
ture. The  temperature  of  the  blood  appears  peculiarly  adapted  for  quick 
coagulation  ;  whereas  at  0°  C.  it  is  as  slow  as  possible.  In  the  living  vessels 


AMYLOID    SUBSTANCE —PEPTONE.  797 

the  blood  coagulates  slowly;  by  contact  with  foreign  bodies  coagulation  oc- 
curs quickly.  Carbonic  acid  protracts  or  prevents  coagulation  ;  passing  air 
through  the  liquid,  or  any  other  agitation,  hastens  it.  Free  acids,  for  ex- 
ample, acetic,  lactic,  phosphoric,  and  also  free  alkalies  and  their  carbon- 
ates, stop  coagulation.  When  brought  into  a  solution  of  sodium  nitrate  or 
chloride,  fibrin  swells  to  a  slimy  jelly-like  mass,  and  partially  dissolves: 
sodium  sulphate  also  hinders  the  coagulation  of  fibrin.  Thus  fibrin  may 
be  prepared  by  allowing  the  blood  to  flow  from  a  vein  into  a  vessel  con- 
taining much  concentrated  solution  of  sodium  sulphate  whilst  it  is  briskly 
stirred.  The  whole  is  left  to  stand  until  the  blood-globules  are  completely 
separated.  The  clear  fluid  is  then  thrown  into  ten  times  its  bulk  of  water, 
on  which  the  coagulation  of  the  liquid  takes  place.  When  washed  fibrin 
in  a  neutral  liquid  is  heated  to  72°,  it  becomes  white  and  loses  its  trans- 
parency, like  coagulated  albumin.  If  the  liquid  has  an  acid  reaction,  the 
coagulation  takes  place  even  at  a  lower  temperature.  Fibrin  is  usually 
procured  by  washing  the  coagulum  of  blood  in  a  cloth  until  all  the  soluble 
portions  are  removed,  or  by  agitating  fresh  blood  with  a  bundle  of  twigs, 
when  the  fibrin  attaches  itself  to  the  latter,  and  is  easily  removed  and 
cleansed  by  repeated  washing  with  water,  after  which  the  fat  is  extracted 
by  ether.  On  an  average,  fibrin  has  the  composition  52 -6  carbon,  7-0  hy- 
drogen, 17*4  nitrogen,  21-8  oxygen,  and  1-2  sulphur. 

COAGULATED  ALBUMINOUS  SUBSTANCES.  —  Coagulated  albumin  is  formed 
from  albumin,  syntonin,  fibrin,  myosin,  &c.,  by  heating  their  neutral  solu- 
tions to  boiling,  or  by  the  action  of  alcohol.  Egg  albumin  is  also  changed 
into  coagulated  albumin  by  strong  hydrochloric  acid  and  by  ether.  The 
albuminates,  and  also  casein,  when  precipitated  by  neutralization,  pass 
into  coagulated  albumin  when  heated.  The  coagulated  albuminous  sub- 
stances are  insoluble  in  water,  alcohol,  and  other  indifferent  fluids,  scarcely 
soluble  in  dilute  potash,  soluble  with  great  difficulty  in  ammonia.  In  acetic 
acid  they  swell  up,  and  by  degrees  dissolve.  They  are  mostly  insoluble  in 
dilute  hydrochloric  acid;  but  when  pepsin  is  also  present  at  blood  heat, 
they  change  first  into  syntonin,  and  then  into  peptone.  They  are  dissolved 
by  strong  hydrochloric  acid,  and  by  caustic  potash  they  are  changed  into 
albuminates. 

AMYLOID  SUBSTANCE. — According  to  C.  Schmidt,  Friedreich,  and  Kekule", 
it  is  composed  of  53-6  carbon,  7-10  hydrogen,  15-0  nitrogen,  and  14-4  oxy- 
gen and  sulphur.  It  differs  only  from  coagulated  albumin  in  being  colored 
reddish  by  iodine,  and  violet  by  sulphuric  acid  and  iodine.  It  gives  no 
trace  of  sugar  when  boiled  with  dilute  sulphuric  acid,  but  with  caustic 
potash  and  acid  it  behaves  exactly  like  an  albuminous  substance.  Concen- 
trated hydrochloric  acid  dissolves  it,  and  the  solution  diluted  with  water 
gives  a  precipitate  which  has  all  the  properties  of  syntonin  hydrochlorate. 
By  solution  in  caustic  potash,  a  potassium  albuminate  is  obtained.  It  may 
be  formed  at  will  by  treating  fibrin  with  very  dilute  hydrochloric  acid,  and 
evaporating  the  solution  to  dryness  in  a  water-bath.  An  impure  amyloid 
substance  may  be  obtained  from  any  gland  much  infiltrated  with  the  sub- 
stance, as,  for  example,  the  liver,  by  dividing  it  and  removing  the  vessels, 
and  extracting  the  bile  substances  with  cold  water.  It  is  then  boiled  for 
some  time  with  water  to  remove  the  cellular  tissue,  and  the  residue  is 
treated  with  boiling  alcohol  and  ether  to  dissolve  the  fat  and  cholesterin. 
The  residual  mass  consists  chiefly  of  amyloid  substance  characterized  by 
the  iodine  reaction. 

PEPTONE. — By  the  action  of  the  acid  gastric  juice,  all  albuminous  sub- 
stances are  changed  into  bodies  called  peptones.  These  are  found  only  in 

67* 


798  ANIMAL    SUBSTANCES. 

the  stomach  and  contents  of  the  small  intestines.  They  can  no  longer  be 
detected  in  the  chyle.  They  are  easily  soluble  in  water,  insoluble  in  alco- 
hol or  ether  ;  but  alcohol  separates  them  with  difficulty  from  the  watery 
solution;  when  precipitated  they  remain  unchanged  even  after  boiling. 
They  are  not  precipitated  either  by  acids  or  by  alkalies.  Acetic  acid  and 
potassium  ferrocyanide  give  no  precipitate;  but  corrosive  sublimate  and 
lead  acetate  with  ammonia  give  precipitates.  The  substance  designated  by 
Meissner  as  metapeptone  does  not  certainly  belong  to  the  peptones,  although 
of  these  there  are  many  different  kinds,  whose  properties  are  not  yet  suffi- 
ciently made  out  to  enable  them  to  be  accurately  distinguished. 

METALBUMIN  was  found  by  Scherer  in  a  slimy,  ropy,  dropsical  liquid  ob- 
tained by  tapping.  In  the  dilute  liquid  neither  acetic  nor  hydrochloric 
acid  caused  a  precipitate.  It  became  cloudy  when  boiled,  and  after  this 
acetic  acid  caused  no  precipitate.  Acetic  acid  and  potassium  ferrocyanide 
also  caused  no  precipitate.  Alcohol  caused  a  precipitate,  which  redissolved 
in  water. 

HAEMOGLOBIN,  54'2  carbon,  7-2  hydrogen,  0-42  iron,  16'0  nitrogen,  21-5 
oxygen,  and  0-7  sulphur;  also  called  Hsematoglobulin  and  HsemalocrystaMin. 
This  substance  forms  the  chief  part  of  the  red  globules  of  the  blood  of 
vertebrata ;  ustially  it  is  obtained  in  an  amorphous  condition,  but  from  the 
blood  of  some  animals  —  as,  for  example,  dogs,  cats,  rats,  mice,  and  many 
fish  —  it  can  be  separated  in  the  crystalline  form.  Red  crystals  can  be  ob- 
tained from  dog's  blood  by  mixing  the  defibrinated  blood  with  an  equal 
quantity  of  water  and  adding  one  volume  of  alcohol  to  four  volumes  of  the 
diluted  blood  and  leaving  it  to  stand  at  0°  C.,  or  lower.  After  twenty-four 
hours  the  crystals  are  filtered  off,  squeezed,  and  dissolved  in  the  least  pos- 
sible quantity  of  water  at  25°  to  30°  C.  (77°-86°  F.).  This  solution  is 
again  mixed  with  one-fourth  its  volume  of  alcohol,  and  the  re-crystalliza- 
tion is  repeated  many  times.  In  different  animals  differently  formed  crys- 
tals are  found.  In  the  guinea-pig  they  are  tetrahedrons ;  in  the  squirrel, 
six-sided  tables;  in  the  goose,  rhombic  four-sided  or  six-sided  tables;  in 
dogs  and  cats,  long  four-sided  prisms.  In  a  vacuum  over  sulphuric  acid 
they  lose  water  of  crystallization  and  change  into  a  bright  brick-red  mass. 
The  crystals  which  form  when  the  air  has  access  to  them  also  contain  oxy- 
gen loosely  combined ;  the  more  moist  they  are  the  more  oxygen  they  con- 
tain. This  they  lose  when  warmed  in  a  vacuum ;  by  exposure  over  sulphu- 
ric acid  a  portion  of  the  oxygen  escapes.  The  crystals  dissolve  in  water 
with  difficulty;  the  saturated  solution  at  5°  C.  (41°  F.),  contains  2  per 
cent,  haemoglobin,  but  by  increase  of  temperature  the  solubility  is  con- 
siderably increased.  In  feebly  alkaline  liquids,  as  in  blood-serum,  the 
crystals  are  much  more  soluble. 

These  solutions  have  a  very  beautiful  blood-red  color  and  absorb  the 
light  from  the  commencement  of  the  red  to  three-fourths  of  the  section  of 
the  spectrum  between  the  lines  C  and  D  in  the  solar  spectrum.  The  part 
of  the  spectrum  lying  about  the  line  D  of  this  space  between  C  and  D  is 
much  more  strongly  absorbed  than  the  rest.  If  the  oxygen  is  expelled 
from  the  solution  by  carbonic  acid  or  hydrogen,  the  liquid  then  absorbs 
the  light  most  beyond  D ;  the  rest  of  the  light  is  more  strongly  absorbed 
than  it  is  by  the  haemoglobin  solution  which  contains  oxygen ;  and  even 
the  light  between  A  and  B  is  more  strongly  absorbed  by  solutions  which 
contain  no  oxygen  than  by  those  which  contain  it.  The  change  of  color 
and  transparency  of  the  blood  and  blood-solutions  when  they  pass  from 
the  venous  condition  into  one  containing  more  oxygen,  and  vice  versa,  de- 
pend, without  doubt,  on  these  optical  properties.  The  fresh  blood  taken 
from  a  vein  of  an  animal  shows  clearly  strong  absorption  of  light  from  B 


H^JMATIN.  799 

to  beyond  C  in  the  spectrum,  and  this  disappears  when  the  blood  is  agi- 
tated with  air. 

When  a  concentrated  solution  of  haemoglobin  is  diluted  with  water,  it 
rapidly  increases  in  transparency  up  to  the  line  D;  by  further  dilution  the 
spectrum  extends  beyond  F,  whilst  at  the  same  time  between  D  and  E  a 
green-yellow  streak  appears.  The  band  lying  nearest  to  I)  is  darker  and 
more  sharply  bounded  than  the  other,  and  ultimately  disappears  by  con- 
tinued dilution  a  little  later  than  the  other  band ;  the  appearance  of  these 
bands  is  influenced  by  the  combination  of  oxygen  with  the  haemoglobin. 
For  if  a  tolerably  dilute  blood  solution  is  allowed  to  stand  some  time,  or 
if  such  a  solution  is  warmed  in  a  water-bath  above  50°  C.  (122°  F.),  or  if 
to  a  blood  solution,  or  a  pure  solution  of  haemoglobin,  a  few  drops  of  am- 
monium sulphide,  or  of  an  ammoniacal  solution  of  zinc  tartrate,  be  added, 
the  arterial  color  of  the  solution  gradually  vanishes,  and  by  examination 
in  the  spectrum,  in  the  place  between  these  two  bands,  there  is  seen  a 
broader  ill-defined  absorption-band,  about  in  the  middle  between  D  and  E; 
at  the  same  time  the  blue  shows  that  it  is  less  absorbed  than  by  blood  con- 
taining oxygen.  The  venous  blood  of  animals  does  not  show  this  property 
clearly  when  it  is  taken  from  the  animal;  but  animals  that  have  died  as- 
phyxiated do  show  this  change  in  the  blood.  If  a  solution  of  haemoglobin, 
or  of  blood,  from  which  the  oxygen  has  been  taken  away,  is  shaken  with 
atmospheric  air,  the  two  absorption-bands  of  the  haemoglobin  containing 
oxygen  again  appear,  and  the  oxygen  must  be  chemically  combined  with 
the  haemoglobin,  for  it  is  not  removed  by  nitric  oxide  gas. 

Dilute  solutions  of  haemoglobin  may  be  heated  to  70°  or  80°  C.  (158°- 
176°  F.)  for  a  short  time  without  marked  change,  but  when  the  heat  is  con- 
tinued, the  haemoglobin  splits  into  haamatin  and  coagulated  albumin,  with 
marked  change  of  color  and  coagulation.  Alcohol  causes  the  same  decom- 
position. Generalty  no  substance  is  known  which  cai\  precipitate  haemo- 
globin without  at  the  same  time  destroying  it;  alkalies,  and  more  readily 
acids,  cause  it  to  split  without  first  precipitating  it;  this  occurs  the  more 
readily  the  more  concentrated  the  alkali  or  acid  is,  or  the  greater  the  quan- 
tity of  it  used,  and  the  more  concentrated  the  solution  of  haemoglobin,  or 
the  higher  the  temperature.  Haemoglobin,  in  a  dilute  solution  at  ordinary 
temperature,  is  not  decomposed  by  carbonated  alkalies.  A  feebly  alkaline 
solution  is  more  permanent  than  a  neutral  solution;  the  feeblest  acids,  even 
carbonic  acid,  decompose  haemoglobin ;  hydrogen  sulphide  does  not  act  on 
haemoglobin  when  it  contains  no  oxygen,  but  on  oxyhaemoglobin  it  acts, 
causing  the  separation  of  sulphur  and  of  an  albuminous  substance.  Car- 
bon monoxide  passed  into  a  solution  of  oxyhaemoglobin  drives  the  oxygen 
out  and  forms  a  compound  of  carbon  monoxide  and  haemoglobin.  It  also 
combines  with  haemoglobin  free  from  oxygen. 

Metahsemoglobin,  so  named  by  Hoppe,  maybe  a  mixture  of  haematin  and  an 
easily  soluble  albuminous  matter.  It  has  been  found  in  old  extravasations 
of  blood,  in  the  brown  fluid  from  the  ovaries,  in  strumous  cysts,  hydrocele, 
&c.,  or  when  a  solution  of  haemoglobin  is  long  kept.  Even  when  a  solution 
of  haemoglobin  is  filtered,  that  which  is  sucked  up  by  the  edge  of  the  filter 
passes  into  metahaemoglobin.  Ozone  has  the  same  action.  A  solution  of 
metahaemoglobin  has  a  manifestly  acid  reaction  arising  from  volatile  acids 
(butyric  and  formic),  produced  by  changes  in  the  haemoglobin.  The  optical 
properties  of  metahaemoglobin  are  similar  to  those  of  solutions  of  haematin 
in  acids,  alcohol,  and  ether. 

H.EMATIN,  CggH^NjjFegOjg,  occurs  in  the  body  as  a  product  of  the  decom- 
position of  haemoglobin  in  old  extravasations;  after  haemorrhage  into  the 
stomach  it  may  be  found  in  the  faeces.  It  is  obtained  pure  by 
the  compound  with  hydrochloric  acid  in  ammonia,  evaporating  to  dryness, 


800  ANIMAL    SUBSTANCES. 

and  heating  the  residue  to  130°  C.  (266°  F.).  The  ammonium  chloride  is 
extracted  with  water,  and  the  residue  dried  at  130°.  It  gives  12-8  per  cent, 
of  iron  oxide  as  a  residue  when  burnt,  and  is  insoluble  in  water,  alcohol, 
ether,  and  chloroform.  In  ammoniacal  solutions  it  is  soluble.  It  combines 
with  alkalies  and  acids:  by  boiling  with  dilute  nitric  acid  it  loses  its  color, 
and  is  decomposed.  Chlorine  passed  into  an  alkaline  solution  decomposes 
it  very  rapidly. 

Hsematin  combined  with  Hydrochloric  Acid,  CggH^NjgFegOjg.  2HC1,  is  ob- 
tained in  regular  crystals  by  treating  haemoglobin  or  metahgemoglobin  with 
common  salt  and  strong  acetic  acid.  The  defibrinated  blood  of  some  animal 
is  diluted  with  once  or  twice  its  volume  of  water,  and  lead  acetate  is  added 
as  long  as  a  precipitate  falls.  The  blood  is  then  filtered,  and  the  excess  of 
lead  removed  from  the  filtrate  by  sodium  carbonate,  again  filtered,  and  the 
clear  solution  is  evaporated  over  sulphuric  acid.  The  residue  is  powdered 
and  rubbed  with  from  15  to  20  times  its  weight  of  commercial  glacial  acetic 
acid,  to  which  a  little  common  salt  is  added.  The  brown  mixture  is  heated 
in  a  water-bath,  and  frequently  shaken  for  an  hour  or  two  until  all  is  dis- 
solved. About  five  times  the  volume  of  pure  water  is  then  added,  and  it  is 
left  to  stand  for  a  week  in  an  even  temperature.  The  liquid  is  then  poured 
off  from  the  crystals;  these  are  again  boiled  with  glacial  acetic  acid;  a 
great  mass  of  water  is  then  added,  find  the  precipitate  is  allowed  to  settle, 
separated,  well  washed,  again  allowed  to  deposit,  and  then  dried  in  a  water- 
bath.  The  crystals  are  mostly  thin  rhombic  plates  of  dark-blue  color,  and 
dirty-brown  by  transmitted  light.  From  the  name  of  their  discoverer  they 
are  called  Teichmann's  Hscmin  crystals.  They  are  perfectly  insoluble  in  water, 
alcohol,  and  ether.  They  are  soluble  in  acids  and  alkalies,  but  only  in  acetic 
and  hydrochloric  acids  without  decomposition.  They  may  be  heated  to 
130°  C.  (266°  F.),  without  decomposition  :  at  red  heat  they  do  not  swell  up, 
but  burn,  leaving  pure  oxide  of  iron. 

MUCIN,  containing  52-2  carbon,  7-0  hydrogen,  12-6  nitrogen,  and  28-2 
oxygen,  usually  called  mucus,  may  be  prepared  from  filtered  ox-gall  by 
precipitating  it  with  alcohol,  washing  with  dilute  alcohol,  dissolving  in  wa- 
ter, and  precipitating  by  acetic  acid.  It  cannot  be  perfectly  purified  from 
biliary  coloring  matter.  It  may  be  obtained  more  pure  from  the  salivary 
glands  by  solution  in  water  and  precipitation  by  acetic  acid.  Mucin  swells 
up  in  water,  and  by  sufficient  dilution  it  can  be  filtered.  It  is  precipitable 
by  alcohol  in  excess ;  also  by  acetic  acid,  and  it  is  not  soluble  in  an  excess 
of  the  precipitant;  also  by  nitric,  hydrochloric,  and  sulphuric  acids,  and 
it  is  soluble  in  an  excess  of  these  acids.  It  is  not  precipitated  by  mercuric 
chloride,  lead  acetate,  or  potassium  ferrocyanide.  It  is  not  coagulable  by 
boiling ;  when  thoroughly  dried,  it  merely  swells  in  water  to  a  thick  mass. 

PYIN  is  said  often  to  occur  in  pus :  but  normal  pus  contains  neither  pyin 
nor  mucin.  It  is  precipitable  by  acetic  acid,  and  this  precipitate  is  not 
soluble  in  an  excess  of  acid,  while  the  precipitates  with  nitric  and  hydro- 
chloric acids  are  so ;  a  solution  of  pyin  in  hydrochloric  acid  is  not  precipi- 
table by  a  solution  of  potassium  ferrocyanide.  It  is  distinguishable  from 
mucin  only  by  being  precipitable  by  mercuric  chloride  and  lead  acetate. 
The  precipitate  which  forms  in  the  serum  of  healthy  pus  on  the  addition 
of  acetic  acid  is  soluble  in  a  solution  of  common  salt,  and  consists  of  al- 
bumin. 

PEPSIN  has  not  yet  been  perfectly  isolated ;  it  resembles  mucin,  and  is 
precipitated  by  lead  acetate  and  by  alcohol;  according  to  Briicke's  dis- 
covery it  is  also  carried  down  from  its  solution  when  any  fine  granular  pre- 
cipitate is  produced.  Briicke's  method  has  also  been  used  for  isolating 
other  substances  resembling  pepsin.  For  this  purpose  fresh-formed  cal- 


GELATIN  —  CHONDRIN.  801 

cium  phosphate  or  cholesterin  is  dissolved  in  4  parts  alcohol  and  1  ether, 
or  even  animal  charcoal  or  milk  of  sulphur  may  be  used.  The  pepsin  may 
be  obtained  thus  dissolved  in  water,  and  this,  when  mixed  with  very  dilute 
hydrochloric  acid,  changes  albumin  into  peptone. 

SUGAR-FORMING  FERMENTS  IN  SALIVA  AND  PANCREATIC  FLUID  have  also 
been  separated  by  addition  of  dilute  phosphoric  acid,  and  subsequent  neu- 
tralization afterwards  by  lime-water  and  by  ethereal  solutions  of  cholesterin. 
They  can  be  dissolved  in  water  and  precipitated  by  absolute  alcohol.  They 
can  be  dried  at  ordinary  temperatures  without  decomposition.  If  heated 
to  100°,  they  lose  their  power  of  acting  upon  starch.  When  boiled  with 
nitric  acid,  and  mixed  with  an  excess  of  ammonia,  the  solution  remains 
colorless. 

GELATIN  AND  CHONDRIN. — Animal  membranes,  skin,  tendons,  and  even 
bones,  dissolve  in  water  at  a  high  temperature  more  or  less  completely,  but 
with  very  different  degrees  of  facility,  giving  solutions  which  on  cooling 
acquire  a  soft-solid,  tremulous  consistence.  The  substance  so  produced  is 
called  gelatin:  it  does  not  pre-exist  in  the  animal  system,  but  is  generated 
from  the  membranous  tissue  by  the  action  of  hot  water.  The  jelly  of 
calves'  feet,  and  common  size  and  glue,  are  familiar  examples  of  gelatin  in 
different  conditions  of  purity.  Isinglass,  the  dried  swimming-bladder  of 
the  sturgeon,  dissolves  in  water  merely  warm,  and  yields  a  beautifully  pure 
gelatin.  In  this  state  it  is  white  and  opalescent,  or  translucent,  quite  in- 
sipid and  inodorous,  insoluble  in  cold  water,  but  readily  dissolving  by  a 
slight  elevation  of  temperature.  Cut  into  slices  and  exposed  to  a  current 
of  dry  air,  it  shrinks  prodigiously  in  volume,  and  becomes  a  transparent, 
glassy,  brittle  mass,  which  is  soluble  in  warm  water,  but  insoluble  in  alco- 
hol and  ether.  By  dry  distillation  a  watery  fluid  is  produced,  containing 
much  carbonate  of  ammonia,  and  a  thick  brown  oil,  in  which,  besides  am- 
monium carbonate,  ammonium  sulphide,  ammonium  cyanide,  and  neutral 
oily  bodies,  various  basic  substances  exist,  as  aniline,  picoline,  methyl- 
amine,  trimethylamine,  butylamine,  and  probably  many  others.  In  the 
dry  state,  gelatin  may  be  kept  indefinitely :  in  contact  with  water,  it 
becomes  acid,  loses  the  property  of  gelatinizing,  and  putrefies.  Long-con- 
tinued boiling  gradually  alters  it,  and  the  solution  loses  the  power  of  form- 
ing a  jelly  on  cooling.  1  part  of  dry  gelatin  or  isinglass  dissolved  in  100 
parts  of  water  solidifies  on  cooling. 

An  aqueous  solution  of  gelatin  is  precipitated  by  alcohol,  which  with- 
draws the  water :  corrosive  sublimate  in  excess  gives  a  white  flocculent 
precipitate,  and  the  same  happens  with  solution  of  mercurous  and  mer- 
curic nitrate:  neither  alum,  neutral  lead  acetate,  nor  basic  lead  ace- 
tate affects  a  solution  of  gelatin.  With  tannic  acid  or  infusion  of  galls, 
gelatin  gives  a  copious,  whitish,  curdy  precipitate,  which  coheres  on 
stirring  to  an  elastic  mass,  quite  insoluble  in  water,  and  incapable  of  pu- 
trefaction. 

Tannic  acid  is  the  only  acid  that  gives  a  precipitate  with  a  solution  of 
gelatin.  It  does  so  even  when  the  solution  is  exceedingly  dilute. 

Chlorine  passed  into  a  solution  of  gelatin  occasions  a  dense  white  pre- 
cipitate of  chlorite  of  gelatin,  which  envelops  each  gas-bubble,  and  ulti- 
mately forms  a  tough,  elastic,  pearly  mass,  somewhat  resembling  fibrin. 
Boiling  with  strong  alkalies  converts  gelatin,  with  evolution  of  ammonia, 
into  leucine,  and  glycocine.  This  last-mentioned  substance,  also  called 
glycocol,  was  first  formed  by  the  action  of  cold  concentrated  sulphuric  acid 
upon  gelatin,  and  has  lately  been  obtained  by  the  action  of  acids  upon  hip- 
puric  acid,  which  is  thereby  resolved  into  benzoic  acid  and  glycocine  (see 
page  633). 

A  dilute  solution  of  gelatin,  distilled  with  a  mixture  of  potassium  bichro- 


802  ANIMAL    SUBSTANCES. 

mate  and  sulphuric  acid,  yields  acetic,  valeric,  benzoic,  and  hydrocyanic 
acids,  and  two  volatile  oily  principles  termed  valeronitrile,  CgHgN,  and  val- 
eracetonitrtte,  C26H48N406.  The  former  is  a  thin  colorless  liquid,  of  aromatic 
odor,  like  that  of  salicylol:  it  is  lighter  than  water,  and  boils  at  125°  C. 
(257°  F.).  The  latter  much  resembles  the  first,  but  boils  at  70°  C.  (158°  F.). 
Alkalies  convert  valeronitrile  into  valeric  acid  and  ammonia,  and  valerace- 
tonitrile  into  valeric  acid,  acetic  acid,  and  ammonia.  Valeracetonitrile 
contains  the  elements  of  4  molecules  of  valeronitrile  and  3  molecules  of 
acetic  acid: 

C26H48N406  4C5H9N          -f          3C2H402. 

Dry  gelatin,  subjected  to  analysis,  has  been  found  to  contain  in  100  parts, 
50-05  carbon,  6-47  hydrogen,  18-35  nitrogen,  and  25-13  oxygen. 

The  cartilage  of  the  ribs  and  joints  yields  a  gelatin  differing  in  some  re- 
spects from  the  preceding :  it  is  called,  by  way  of  distinction,  chondrin.  It 
is  less  soluble  in  boiling  water  than  gelatin.  It  is  precipitated  from  its 
solution  by  acetic  acid,  and  is  not  soluble  in  an  excess  of  acid.  Other  acids 
in  very  small  quantity  precipitate  chondrin,  but  the  slightest  excess  redis- 
solves  the  precipitate.  Acetate  of  lead  and  solution  of  alum  also  precipi- 
tate this  substance.  These  reactions  distinguish  chondrin  from  gelatin. 
Scherer  gives  50-75  carbon,  6-90  hydrogen,  14-70  nitrogen,  and  27-65  oxy- 
gen. The  doubtful  formulae  CjgH^N^  and  C^H^NgOjo,  have  been  assigned 
to  chondrin. 

If  a  solution  of  gelatin,  albumin,  fibrin,  casein,  or  probably  any  one  of 
the  more  complex  azotized  animal  principles,  be  mixed  with  solution  of 
cupric  sulphate,  and  then  a  large  excess  of  caustic  potash  added,  the  green- 
ish precipitate  first  formed  is  redissolved,  and  the  liquid  acquires  a  deep 
and  beautiful  purple  tint. 

Gelatin  is  largely  employed  as  an  article  of  food,  as  in  soups,  &c. ;  but 
its  value  in  this  respect  has  been  perhaps  overrated.  In  the  useful  arts,  size 
and  glue  are  consumed  in  great  quantities.  These  are  prepared  from  the 
clippings  of  hides,  and  other  similar  matters,  enclosed  in  a  net,  and  boiled 
with  water  in  a  large  caldron.  The  strained  solution  gelatinizes  on  cool- 
ing, and  constitutes  size.  Glue  is  the  same  substance  in  a  state  of  desicca- 
tion, the  size  being  cut  into  slices  and  placed  upon  nettings  freely  exposed 
to  a  current  of  air.  Gelatin  is  extracted  from  bones  with  much  greater 
difficulty:  the  best  method  of  proceeding  is  said  to  be  to  enclose  the  bones, 
previously  crushed,  in  strong  metallic  cylinders,  and  admit  high-pressure 
steam,  which  attacks  and  dissolves  the  animal  matter  much  more  easily 
than  boiling  water;  or,  to  steep  the  bones  in  dilute  hydrochloric  acid, 
thereby  removing  the  earthy  phosphate,  and  then  dissolve  the  soft  and 
flexible  residue  by  boiling. 

There  is  an  important  economical  application  of  gelatin,  or  rather  of  the 
material  which  produces  it,  which  deserves  notice — viz.,  to  the  clarifying 
of  wines  and  beer  from  the  finely  divided  and  suspended  matter  which 
often  renders  these  liquids  muddy  and  unsightly.  When  isinglass  is  di- 
gested in  very  dilute  cold  acetic  acid,  as  sour  wine  and  beer,  it  softens, 
swells,  and  assumes  the  aspect  of  a  very  light  transparent  jelly,  which, 
although  quite  insoluble  in  the  cold,  may  be  readily  mixed  with  a  large 
quantity  of  watery  liquid.  Such  a  preparation,  technically  called  finings, 
is  sometimes  used  by  brewers  and  wine-merchants  for  the  purpose  before 
mentioned:  its  action  on  the  liquor  with  which  it  is  mixed  seems  to  be 
purely  mechanical,  the  gelatinous  matter  slowly  subsiding  to  the  bottom  of 
the  cask,  and  carrying  with  it  the  insoluble  substance  to  which  the  tur- 
bidity was  due. 

HORNY  MATTER;  ELASTIN  (55-5  carbon,  7-4  hydrogen,  16-7  nitrogen,  and 
20-5  oxygen).  —  This  substance  is  prepared  by  boiling  the  ligamentum  nuchss 


KERATIN  —  PEOTAGON.  803 

of  cattle  with  alcohol,  ether,  water,  concentrated  acetic  acid,  and  dilute 
caustic  soda.  It  has  a  yellow  color  when  moist,  is  extensible,  but  becomes 
brittle  after  drying.  It  is  perfectly  insoluble  in  cold  or  boiling  water,  also 
in  ammonia,  acetic  acid,  or  alcohol.  In  a  concentrated  solution  of  potash 
it  is  dissolved,  and  at  the  same  time  decomposed.  The  solution  is  not  pre- 
cipitated by  acids,  only  with  tannic  acid  the  neutral  solution  gives  a  pre- 
cipitate. When  boiled  with  sulphuric  acid  it  is  decomposed,  with  formation 
of  leucine. 

KERATIN.  —  Hair,  nails,  horn,  feathers,  epidermis,  and  epithelium,  boiled 
with  ether,  alcohol,  water,  and  dilute  acid,  yield  residual  substances  which 
do  not  agree  well  in  their  analysis,  and  therefore  probably  are  not  rightly 
classed  under  one  name.  These  bodies  swell  but  little  in  water,  but  when 
dry  are  very  hygroscopic.  By  continual  boiling  in  water  at  150°  C.  (302° 
F.),  they  partially  decompose.  A  milky  liquid  forms,  and  sulphuretted 
hydrogen  escapes.  If  the  solution  is  evaporated  to  dryness,  a  residue,  in- 
soluble in  water,  remains.  In  acetic  acid  these  substances  swell  up  more 
than  in  water,  without  materially  altering  in  texture  ;  in  concentrated 
acetic  acid  they  dissolve  when  boiled  ;  and  when  boiled  with  sulphuric 
acid,  they  give  leucine,  and  about  4  per  cent,  of  tyrosine.  In  caustic  pot- 
ash, and  with  difficulty  in  a  solution  of  potassium  carbonate,  they  swell 
up,  and  when  heated  dissolve.  The  alkaline  solutions  evolve  sulphuretted 
hydrogen  on  addition  of  acids. 

FIBROIN,  48-6  carbon,  6-5  hydrogen,  17-3  nitrogen,  and  27-6  oxygen.  — 
This  substance  dissolves  in  concentrated  acids  and  alkalies  and  in  ammo- 
niacal  cupric  solution,  but  not  in  ammonia:  when  neutralized,  the  solutions 
give  precipitates ;  by  boiling  with  dilute  sulphuric  acid  it  yields  leucine 
and  5  per  cent,  of  tyrosine. 

SPONGIN  is  obtained  from  sponge  by  treating  it  with  ether,  alcohol,  hy- 
drochloric acid,  and  5  per  cent,  soda-lye.  It  closely  agrees  in  composition 
with  fibroin,  but  when  boiled  with  sulphuric  acid  does  not  yield  tyrosine, 
but  glycocine  and  leucine. 

CONCHIOLIN  forms  the  greater  part  of  the  organic  basis  of  mussel-shells. 
It  is  insoluble  in  water,  alcohol,  acetic  acid,  dilute  mineral  acid,  and  pot- 
a^sh-lye.  It  contains  16  or  17  per  cent,  of  nitrogen,  and  gives  by  boiling 
with  sulphuric  acid,  only  leucine,  and  no  tyrosine,  glycocine,  or  sugar. 

CIIITIN,  from  the  skeleton  of  insects  and  Crustacea,  C9H12H06.  It  is  best 
prepared  by  boiling  the  elytra  of  the  cockchafer  with  alkalies,  water,  acetic 
acid,  alcohol,  and  ether.  It  yields  glucose  when  dissolved  in  sulphuric  acid. 

PROTAGON  AND  EURINE. — Protagon,  first  prepared  and  investigated  by 
Liebreich,  was  formerly  known  in  an  impure  state  as  cerebrin,  cerebric 
acid,  lecithin,  and  when  swollen  in  water,  as  myelin.  It  forms  the  chief 
constituent  of  the  nervous  substance  in  the  nervous  centres  and  peripheral 
nerves.  It  also  most  likely  occurs  in  oil  of  eggs,  in  pus-cells,  in  white 
blood-cells,  and  in  semen;  but  at  present  it  has  only  been  obtained  pure 
from  the  brain,  which  must  be  freed  as  much  as  possible  from  blood  and 
extraneous  tissues.  The  emulsion  is  agitated  with  water,  and  poured  into 
a  ilask:  much  ether  is  poured  on  it,  and  after  constant  shaking  at  29°  C. 
(84°  F.),  it  is  allowed  to  stand  for  some  time  and  at  the  same  temperature. 
The  ether  is  poured  off,  filtered,  and  the  solution  is  cooled  from  0°  to 
— 10°  C.  (14°  F.),  filtered  at  this  low  temperature,  and  washed  out  \\iih 
cold  ether  until  no  more  cholesterin  is  extracted  by  the  ether.  The  resi- 
due is  dried  over  sulphuric  acid,  dissolved  in  alcohol  of  80  per  cent,  at 
40°  C.  (10i°  F.),  to  form  a  not  too  concentrated  solution,  and  then  it  is 
allowed  to  cool  slowly  in  a  water-bath.  The  protagon  crystallizes  out  in 


804  ANIMAL    SUBSTANCES. 

bundles  of  fine  needles.  It  is  colorless  and  without  smell,  scarcely  soluble 
in  pure  ether,  easily  in  warm  spirit  of  wine,  very  easily  in  fatty  and  ethereal 
oils,  and  very  easily  also  in  warm  ethereal  solutions  of  fat.  In  water  it 
swells  up  to  an  opalescent  white  mass  like  a  decoction  of  starch,  and  in 
concentrated  solution  forms  a  firm  paste.  When  heated  in  alcohol,  more 
especially  in  absolute  alcohol,  above  50°  to  60°  C.  (122°-140°  F.),  it  decom- 
poses with  separation  of  oily  drops.  When  boiled  with  strong  baryta-wa- 
ter, the  protagon  by  degrees  decomposes  into  glycerin,  phosphoric  acid, 
stearic  acid,  and  a  third  crystalline  non-nitrogenous  acid  not  thoroughly 
investigated ;  but  its  lead-salts  are  soluble  in  ether ;  in  addition  to  these 
acids,  neurine  is  formed,  which  is  a  strong  base. 

NEURINE,  C5H,5NO,  or  C5H,4N(OH),  was  obtained  by  Liebreich  by  boil- 
ing protagon  continuously  with  baryta-water,  precipitating  the  baryta  with 
carbonic  acid,  evaporating  the  filtrate  to  a  very  small  volume,  precipitating 
with  absolute  alcohol,  evaporating  the  filtered  alcoholic  extract  to  a  syrup, 
again  dissolving  it  in  absolute  alcohol,  and  precipitating  the  concentrated 
solution  in  alcohol  with  platinic  chloride.  The  double  platinum-salt, 
(C5H14NC1)2 .  PtCl4,  is  easily  soluble  in  water,  and  crystallizes  in  thin  large 
rhombic  tables  of  a  yellow  color.  It  is  not  altogether  insoluble  in  alcohol. 
Solutions  of  neurine  react  very  strongly  alkaline,  even  after  carbonic  acid 
has  long  been  passed  into  them.  The  solution  of  the  base  in  absolute  alco- 
hol becomes  thick  by  passing  carbonic  acid  into  it ;  carbonate  of  neurine 
with  an  alkaline  reaction  then  forms.  This  is  decomposed  with  efferves- 
cence by  strong  acids.  The  neurine  forms  out  of  protagon  by  simply  split- 
ting into  glycerin,  phosphoric  acid,  &c.  By  its  formation  no  evolution  of 
ammonia  takes  place,  and  the  neurine  takes  all  the  nitrogen  of  the  prota- 
gon. Bauer  has  lately  shown  that  this  substance  is  the  hydrate  of  tri- 
methyl-ethyl-ammonium,  and  Wurtz  has  actually  produced  this  complex 
organic  substance  synthetically. 

INOSINIC  ACID,  C6H8N206  (?),  found  by  Liebig  in  the  flesh  of  some  warm- 
blooded animals.  It  has  not  yet  been  obtained  in  crystals,  but  as  a  syrup 
which  becomes  solid  in  alcohol.  It  dissolves  easily  in  water,  reddens  lit- 
mus strongly,  tastes  pleasantly  like  soup,  and  partly  decomposes  by  boil- 
ing. Its  salts,  even  those  of  the  alkalies,  are  crystalline.  The  alkaline 
salts  are  soluble  in  water.  The  copper  and  silver-salts  form  amorphous, 
insoluble,  or  almost  insoluble  precipitates.  In  alcohol  and  ether  the  ino- 
sinic  salts  are  not  soluble. 

CHLOROHODIC  ACID,  obtained  by  Bosdecker  from  pus  by  extraction  with 
ether,  alcohol,  and  water,  precipitation  with  lead  acetate,  decomposition 
by  hydrogen  sulphide,  and  extraction  with  absolute  alcohol,  forms  fine  mi- 
croscopic needles.  The  acid  dissolves  easily  in  water  or  alcohol,  but  not 
in  ether.  It  will  not  sublime,  melts  when  heated,  and  burns,  with  the 
smell  of  horn.  In  its  watery  solutions,  chloride  of  mercury  and  tin  and 
nitrate  of  mercury  cause  a  white  precipitate.  So  also  does  tannin.  Iodine 
gives  a  light  yellow  precipitate.  Chlorine  water  in  dilute  solutions  gives  a 
rose-red  color ;  dark-red  in  concentrated  solutions. 

EXCRETIN,  CT8H15602S,  according  to  Marcet.  Alcoholic  extract  of  human 
faeces  is  precipitated  with  lime,  and  extracted  with  alcohol  and  ether,  and 
the  solution  left  at  a  sufficiently  low  temperature  to  crystallize.  It  melts 
at  92°  to  90°  C.  (198°-205°  F.),  is  soluble  in  water,  and  in  warm  alcohol  or 
ether,  almost  insoluble  in  cold  alcohol.  The  solutions  have  a  neutral  reac- 
tion. Neither  boiling  caustic  potash  nor  dilute  acids  attack  it.  Nitric 
acid  easily  decomposes  it. 

Excretolic  acid  is  the  name  given  by  Marcet  to  a  mixture  of  fatty  acids, 
&c.,  which  are  precipitated  from  the  alcoholic  extract  of  excrement  by  lime. 


ON  THE  ANIMAL  FLUIDS. 


BLOOD,  URINE,  SWEAT,  SALIVA,  GASTRIC  JUICE,  BILE,  CHYLE,  MUCUS,  PUS, 

MILK. 


COMPOSITION  OF  THE  BLOOD.  — The  blood  is  the  general  circulating  fluid 
of  the  animal  body,  the  source  of  all  nutriment  and  growth,  and  the  gen- 
eral material  from  which  all  the  secretions,  however  much  they  may  differ  in 
properties  and  composition,  are  derived.  Food  or  nourishment  from  with- 
out can  only  be  made  available  by  first  passing  through  the  blood.  It 
serves  also  the  scarcely  less  important  office  of  removing  and  carrying  off 
from  the  body  principles  which  are  hurtful,  or  no  longer  required. 

In  all  vertebrated  animals  the  blood  has  a  red  color,  and  probably  in  all 
cases  a  temperature  above  that  of  the  medium  in  which  the  creature  lives. 
In  the  mammalia  this  is  very  apparent,  and  in  the  birds  still  more  so.  The 
heat  of  the  blood  is  directly  connected  with  the  degree  of  activity  of  the 
respiratory  process.  In  man  the  temperature  of  the  blood  seldom  varies 
much  from  36-6°  C.  (98°  F.),  when  in  a  state  of  health,  even  under  great 
vicissitudes  of  climate:  in  birds  it  is  sometimes  as  high  as  42-8°  C.  (109° 
F.).  To  these  two  highest  classes  of  the  animal  kingdom,  the  mammifers  and 
the  birds,  the  observations  about  to  be  made  are  intended  especially  to  apply. 

In  every  creature  of  this  description  two  kinds  of  blood  are  met  with, 
which  differ  very  considerably  in  their  appearance,  viz.,  that  contained  in 
the  left,  side  of  the  heart  and  in  the  arteries  generally,  and  that  contained 
in  the  right  side  of  the  heart  and  in  the  veins :  the  former,  or  arterial  blood, 
has  a  bright-red  color;  the  latter,  the  venous  blood,  is  blackish-purple.  The 
conversion  of  the  dark  into  the  florid  blood  may  be  traced  to  what  takes 
place  during  its  exposure  to  the  air  in  the  lungs  ;  and  the  opposite  change, 
to  what  takes  place  in  the  capillaries  of  the  general  vascular  system,  or 
the  minute  tubes  or  passages,  distributed  in  countless  numbers  throughout 
the  whole  body,  which  connect  the  extremities  of  the  arteries  and  veins. 
When  compared  together,  little  difference  of  properties  or  composition  can 
be  found  in  the  two  kinds  of  blood :  the  hsemoglobin  of  arterial  blood  is 
found  by  spectrum  analysis  to  differ  from  the  haemoglobin  of  venous  blood. 
The  difference  in  the  interference  bands  is  caused  by  the  combination  of 
oxygen  with  haemoglobin  in  the  arteries  and  its  deoxidation  in  the  veins. 
The  fibrin  varies  a  little,  that  from  venous  blood  being,  as  already  men- 
tioned, soluble  in  a  solution  of  potassium  nitrate,  which  is  not  the  case 
with  arterial  fibrin.  It  is,  besides,  very  prone  to  absorb  oxygen,  and  to 
become,  in  all  probability,  partly  changed  to  a  higher  oxygen-compound  of 
fibrin.  The  only  other  notable  point  of  difference  is  in  the  gaseous  matter 
the  blood  holds  in  solution,  carbonic  acid  predominating  in  the  venous,  and 
free  oxygen  in  the  arterial  variety. 

In  its  ordinary  state  the  blood  has  a  slimy  feel,  a  density  varying  from 
1-058  to  1  057,  and  a  decidedly  alkaline  reaction,  partly  from  soda  com- 
bined with  albumin,  and  partly  from  sodium  carbonate  and  phosphate:  it 
has  a  saline  and  disagreeable  taste,  and,  when  quite  recent,  a  peculiar  odor 
or  halitus,  which  almost  immediately  disappears.  An  odor  may,  however, 
08  805 


806  ANIMAL    FLUIDS. 

afterwards  be  developed  by  addition  of  sulphuric  acid,  which,  is  by  some 
considered  characteristic  of  the  animal  from  which  the  blood  was  obtained. 
The  coagulation  of  blood  in  repose  has  been 
already  noticed,  and  its  cause  traced  to  the  mu- 
tual  action  of  the  fibrino-plastic  and  fibrino-genous 
substances,  which  together  constitute  fibrin  :  the 
effect  is  best  seen  when  the  blood  is  received  in  a 
shallow  vessel,  and  left  to  itself  some  time.  No 
evolution  of  gas  or  absorption  of  oxygen  takes 
place  in  this  process.  By  strong  agitation  coagu- 
lation may  be  prevented ;  the  fibrin  in  this  case 
separates  in  cohering  filaments. 

To  the  naked  eye  the  blood  appears  a  homo- 
geneous fluid  ;  but  it  is  not  so  in  reality.  When 
examined  by  a  good  microscope,  it  is  seen  to  con- 
sist of  a  transparent  and  nearly  colorless  liquid, 
in  which  float  about  a  countless  multitude  of  little 
round  red  bodies  to  which  the  color  is  due;  these 
are  the  blood-discs  or  blood-corpuscles  of  micro- 
scopic observers.  They  are  accompanied  by  colorless  globules,  fewer  and 
larger,  the  white  corpuscles  of  the  blood. 

The  blood-discs  are  found  to  present  different  appearances  in  the  blood 
of  different  animals:  in  the  mammifers  they  look  like  little  round  red  or 
yellowish  discs,  thin  when  compared  with  their  diameter,  being  flattened 
or  depressed  on  opposite  sides.  In  birds,  lizards,  frogs,  and  fish,  the  cor- 
puscles are  elliptical.  In  magnitude  they  seem  to  be  pretty  constant  in  all 
the  members  of  a  species,  but  differ  with  the  genus  and  order.  In  man 
they  are  very  small,  varying  from  ^7T5-  to  3^3-  of  an  inch  in  breadth,  while 
in  the  frog  the  long  diameter  of  the  ellipse  measures  at  least  four  times  as 
much.  The  corpuscles  consist  of  an  envelope  containing  a  fluid  in  which 
the  red  coloring  matter  of  the  blood  is  dissolved. 

The  coagulation  of  blood  effects  a  kind  of  natural  proximate  analysis; 
the  clear,  pale  serum,  or  fluid  part,  is  an  alkaline  solution  of  albumin,  con- 
taining various  soluble  salts ;  the  clot  is  a  mechanical  mixture  of  fibrin  and 
blood-globules,  swollen  and  distended  with  serum,  of  which  it  absorbs  a 
large  but  variable  quantity. 

The  following  table  represents  the  composition  of  healthy  human  blood 
as  a  whole ;  it  is  on  the  authority  of  M.  Lecanu :  * 

(1-)  (2-) 

Water 780-15  785-58 

Fibrin          .         .         .         .         .         .  2-10  3-57 

Albumin 65-09  69-41 

Coloring  matter           ....  133-00  119-63 

Crystallizable  fat 2-43  4-30 

Fluid  fat 1-31  2-27 

Extractive  matter  of  uncertain  nature,  \  ..  .-g  ^  g« 

soluble  in  both  water  and  alcohol    .  J 

Albumin  in  combination  with  soda          .  1-26  2-01 

Sodium  and  potassium  chlorides,  car-  ">  R  q-r  7  on 

bonates,  phosphates,  and  sulphates .  / 
Calcium  and  magnesium   carbonates ;  \ 

phosphates  of  calcium,  magnesium,  I  2-10  1-42 

and  iron  ;  ferric  oxide     .         .         .  J 

Loss 2-40  2-59 

1000-00          1000-00 
*  Ann.  Chim.  Phys.  xlviii.  320. 


URINE.  807 

In  healthy  individuals  of  different  sexes  these  proportions  are  found  to 
vary:  the  fibrin  and  coloring  matter  are  usually  more  abundant  in  the 
male  than  in  the  female :  in  disease,  variations  of  a  far  wider  extent  are 
often  apparent. 

It  appears  singular  that  the  red  corpuscles,  which  are  so  easily  dissolved 
by  water,  should  remain  uninjured  in  the  fluid  portion  of  the  blood.  This 
seems  partly  due  to  the  presence  of  saline  matter,  and  partly  to  that  of  al- 
bumin, the  corpuscles  being  alike  insoluble  in  a  strong  solution  of  salt  and 
in  a  highly  albuminous  liquid.  In  the  blood  the  limit  of  dilution  within 
which  the  corpuscles  retain  their  integrity  appears  to  be  nearly  reached, 
for  when  water  is  added  they  immediately  become  attacked. 

URINE. — The  urine  is  the  great  channel  by  which  the  azotized  matter  of 
those  portions  of  the  body  which  have  been  taken  up  by  the  absorbents, 
and  by  which  the  excess  of  nitrogenous  food  is  conveyed  away  and  rejected 
from  the  system  in  the  form  of  urea.  It  serves  also  to  remove  superfluous 
water  and  foreign  soluble  matters  which  get  introduced  into  the  blood. 

The  two  most  remarkable  and  characteristic  constituents  of  urine,  urea, 
and  uric  acid,  have  already  been  fully  described ;  in  addition  to  these,  it- 
contains  lactic  and  hippuric  acids,  creatin,  creatinine,  and  traces  of  glucose 
and  indican,  calcium  and  magnesium  sulphates,  chlorides,  and  phosphates, 
alkaline  salts,  and  certain  yet  imperfectly  known  principles,  including  an 
odoriferous  and  a  coloring  substance. 

Healthy  human  urine  is  a  transparent,  light  amber-colored  liquid,  which, 
while  warm,  emits  a  peculiar,  aromatic,  and  not  disagreeable  odor.  This 
is  lost  on  cooling,  while  the  urine  at  the  same  time  occasionally  becomes 
turbid,  from  a  deposition  of  urates,  which  redissolve  with  slight  elevation 
of  temperature.  It  is  very  decidedly  acid  to  test-paper;  this  acidity, 
which  continually  varies  in  amount,  has  been  ascribed  to  acid  sodium  phos- 
phate, to  free  uric  acid,  and  to  free  lactic  acid  ;  lactic  acid  can,  however, 
hardly  co-exist  with  alkaline  urates,  and  the  amorphous  buff-colored  de- 
posit obtained  from  fresh  urine  by  spontaneous  evaporation  in  a  vacuum, 
is  not  uric  acid,  but  mixed  acid  urates,  modified  as  to  crystalline  form  by 
the  presence  of  minute  quantities  of  sodium  chloride.  That  a  free  acid  is 
sometimes  present  in  the  urine  is  certain  :  in  this  case  the  reaction  to  test- 
paper  is  far  stronger,  and  the  liquid  deposits  on  standing,  little,  red,  hard 
crystals  of  uric  acid  ;  but  this  is  no  longer  a  normal  secretion. 

An  alkaline  condition  of  the  urine  from  fixed  alkali  is  sometimes  met 
with.  Such  alkalinity  can  always  be  induced  by  the  administration  of  neu- 
tral potassium  or  sodium-salts  of  a  vegetable  acid,  as  tartaric  or  acetic 
acid :  the  acid  of  the  salt  is  burned  in  the  blood  in  the  process  of  respira- 
tion, and  a  portion  of  the  base  appears  in  the  urine  in  the  state  of  car- 
bonate. The  urine  is  often  alkaline  in  cases  of  retention,  from  ammonium 
carbonate  produced  by  putrefaction  in  the  bladder  itself;  but  this  is  easily 
distinguished  from  alkalinity  from  fixed  alkali,  in  which  it  is  secreted  in  that 
condition. 

The  density  of  the  urine  varies  from  1  005  to  1-030:  about  1-020  to  1-025 
may  be  taken  as  the  average  specific  gravity.  A  high  degree  of  density  in 
urine  may  arise  from  an  unusually  large  proportion  of  urea :  in  such  a 
case,  the  addition  of  nitric  acid  will  occasion  an  almost  immediate  produc- 
tion of  crystals  of  urea  nitrate ;  whereas  with  urine  of  the  usual  degree 
of  concentration,  very  many  hours  will  elapse  before  the  nitrate  begins  to 
separate.  The  quantity  of  urine  passed  depends  much  upon  circumstances, 
as  upon  the  activity  of  the  skin.  It  is  usually  more  deficient  in  quantity 
and  of  higher  density  in  summer  than  in  winter.  Perhaps  about  32  ounces 
in  the  24  hours  may  be  assumed  as  a  mean. 

When  kept  at  a  moderate  temperature,  urine  after  some  days  begins  to 


808  ANIMAL    FLUIDS. 

decompose :  it  exhales  an  offensive  odor,  becomes  alkaline  from  the  pro- 
duction of  ammonium  carbonate,  and  turbid  from  the  deposition  of  earthy 
phosphates.  The  ammonium  carbonate  is  due  to  the  putrefactive  decom- 
position of  the  urea,  which  gradually  disappears,  the  ferment,  or  active 
agent  of  the  change,  being  a  peculiar  nitrogenous  substance  which  is 
always  voided  with  the  urine.  It  has  been  found  also  that  the  yellow  ad- 
hesive deposit  containing  infusoria  from  stale  urine  is  a  most  powerful  fer- 
ment to  the  fresh  secretion.  In  this  putrefied  state  urine  is  used  in  several 
of  the  arts,  as  in  dyeing,  and  forms  perhaps  the  most  valuable  manure  for 
land  known  to  exist. 

Putrid  urine  always  contains  a  considerable  quantity  of  ammonium  sul- 
phide: this  is  formed  by  the  deoxidation  of  sulphates  by  the  organic  mat- 
ter. The  highly  offensive  odor  and  extreme  pungency  of  the  decomposing 
liquid  may  be  prevented  by  previously  mixing  the  urine,  as  Liebig  sug- 
gests, with  sulphuric  or  hydrochloric  acid,  in  sufficient  quantity  to  saturate 
all  the  ammonia  that  can  be  formed. 

The  following  is  an  analysis  of  human  urine  by  Berzelius.  1000  parts 
contained  — 

Water 933-02 

Urea 30-10 

Lactates  and  extractive  matter     .         .         17-14 

Uric  acid 1-00 

Potassium  and  sodium  sulphates  .  6-87 

Sodium  phosphate   .         .         .         .         .2-92 
Ammonium  phosphate  .         .         .  1-65 

Calcium  and  magnesium  phosphates        .       1-00 

Sodium  chloride 4-45 

Sal-ammoniac 1-50 

Silica 0-03 

Mucus  of  bladder    .        .        .        .        .0-32 


1000-00 

In  certain  states  of  disorder  and  disease,  substances  appear  in  the  urine 
which  are  never  present  in  the  normal  secretion :  of  these  the  most  com- 
mon is  albumin.  This  is  easily  detected  by  the  addition  of  nitric  acid  in 
excess,  which  then  causes  a  white  cloud  or  turbidity,  which  is  permanent 
when  boiled,  or  by  corrosive  sublimate,  the  urine  being  previously  acidi- 
fied with  a  little  acetic  acid ;  boiling  usually  causes  a  precipitate  which  is 
not  dissolved  by  a  drop  or  two  of  acid.  Mere  turbidity  by  boiling  is  no 
proof  of  albumin,  the  earthy  phosphates  being  often  thrown  down  from 
nearly  neutral  urine  under  such  circumstances  ;  the  phosphatic  precipitate 
is,  however,  instantly  dissolved  by  a  drop  of  any  acid. 

In  diabetes  the  urine  contains  grape-sugar,  the  quantity  of  which  varies 
with  the  intensity  of  the  disease ;  sometimes  it  is  enormous,  the  urine  ac- 
quiring a  density  of  1-040  and  beyond.  It  does  not  appear  that  the  urea 
is  deficient  absolutely,  although  more  difficult  to  discover  from  being  mixed 
with  such  a  mass  of  syrup.  Very  small  traces  of  sugar  may  be  discovered 
in  urine  by  Trommer's  test,  formerly  mentioned  (p.  576)  :  a  few  drops  of 
solution  of  cupric  sulphate  are  added  to  the  urine,  and  afterwards  an  ex- 
cess of  caustic  potash:  if  sugar  be  present,  a  deep  blue  liquid  results, 
which,  on  boiling,  deposits  red  cuprous  oxide.  With  proper  management 
this  test  is  very  valuable.  Urine  containing  sugar,  when  mixed  with  a 
little  yeast,  and  put  in  a  warm  place,  readily  undergoes  vinous  fermenta- 
tion, and  afterwards  yields,  on  distillation,  weak  alcohol  contaminated  with 
ammonia. 

The  urine  of  children  is  said  sometimes  to  contain  benzoic  acid :  this  is 


URINARY    CALCULI.  809 

produced  by  the  decomposition  of  hippuric  acid,  which  constantly  occurs 
in  the  urine  of  healthy  persons.  When  benzoic  acid  is  taken,  the  urine 
after  a  few  hours  yields  on  concentration,  and  the  addition  of  hydrochloric 
acid,  needles  of  hippuric  acid,  soiled  by  adhering  uric  acid. 

The  deposit  of  buff-colored  or  pinkish  amorphous  sediment,  which  so 
frequently  occurs  in  urine  upon  cooling,  after  unusual  exercise  or  slight 
derangements  of  health,  consists  of  a  variable  mixture  of  colored  acid 
urates  uncrystallized:  it  may  be  at  once  distinguished  from  a  deposit  of 
ammonio-magnesian  phosphate  by  its  instant  disappearance  on  the  appli- 
cation of  heat.  The  earthy  phosphates,  besides,  are  hardly  ever  deposited 
from  urine  which  has  an  acid  reaction. 

The  coloring  matters  of  the  urine  have  been  carefully  examined  by  Dr. 
Schunck.  He  finds  that  most  of  the  substances  hitherto  described  as  col- 
oring healthy  urine  are  products  of  the  change  of  one,  or  at  most  two, 
coloring  matters,  which  are  always  present.  The  first  and  most  important 
of  these,  Dr.  Schunck  has  obtained  as  a  dark-yellow  extract,  amorphous 
and  deliquescent,  with  a  peculiar  odor.  It  is  soluble  in  alcohol  and  ether, 
as  well  as  in  water,  and  has  the  composition  C^H^NO^.  It  is  decomposed 
at  a  boiling  temperature,  yielding  a  large  quantity  of  a  brown  resin  and 
volatile  organic  acid.  A  second  extractive  matter,  soluble  in  water  and  al- 
cohol, but  not  in  ether,  he  found  had  the  formula  C,9H27NO,4.  This  is  cer- 
tainly produced  in  the  process  of  preparing  the  first  extractive  matter, 
and,  perhaps,  does  not  pre-exist  in  healthy  urine.  Heat  and  all  strong 
alkalies  and  acids  decompose  these  extractive  matters,  and  give  rise  to 
most  of  the  coloring  matters  which  have  hitherto  been  described  as  exist- 
ing in  healthy  urine.  The  reddish-pink  coloring  matter,  called  purpurin 
or  uro-erythrin,  which  adheres  so  tenaciously  to  the  urates,  is  not  an  ordi- 
nary constituent  of  healthy  urine,  but  is  formed  more  especially  when  the 
secretion  of  bile  is  diminished.  With  regard  to  the  presence  of  indican  in 
healthy  urine,  see  p.  583. 

The  yellow  principle  of  bile  may  be  observed  in  urine  in  cases  of  jaun- 
dice. 

The  urine  of  the  carnivorous  mammifera  is  small  in  quantity  and  highly 
acid.  It  has  a  very  offensive  odor,  and  quickly  putrefies.  In  composition 
it  resembles  that  of  man,  and  is  rich  in  urea.  In  birds  and  serpents,  the 
•urine  is  a  white  pasty  substance,  consisting  almost  entirely  of  urate  of  am- 
monia. In  herbivorous  animals  it  is  alkaline  and  often  turbid  from  earthy 
carbonates  and  phosphates :  urea  is  still  the  characteristic  ingredient, 
while  of  uric  acid  there  is  scarcely  a  trace:  hippuric  acid  is  usually,  if  not 
always,  present,  sometimes  to  a  very  large  extent.  When  the  urine  putre- 
fies, this  hippuric  acid,  as  already  noticed,  becomes  changed  to  benzoic  acid. 

URINARY  CALCULI.  —  Stony  concretions,  differing  much  in  physical  char- 
acters and  in  chemical  composition,  are  unhappily  but  too  frequently 
formed  in  the  bladder  itself,  and  give  rise  to  one  of  the  most  distressing 
complaints  to  which  humanity  is  subject.  Although  many  endeavors  have 
been  made  to  find  some  solvent  or  solvents  for  these  calculi,  and  thus  su- 
persede the  necessity  of  a  formidable  surgical  operation  for  their  removal, 
success  has  been  but  very  partial  and  limited. 

Urinary  calculi  are  generally  composed  of  concentric  layers  of  crystal- 
line or  amorphous  matter,  of  various  degrees  of  hardness.  Very  frequent- 
ly the  central  point  or  nucleus  is  a  small  foreign  body:  curious  illustrations 
of  this  will  be  seen  in  any  large  collection.  Calculi  are  not  confined  to 
man:  the  lower  animals  are  subject  to  the  same  affliction  ;  they  have  been 
found  in  horses,  oxen,  sheep,  pigs,  and  almost  constantly  in  rats. 

The   foil  owing  is  a   sketch  of  the  principal  characters  of  the  different 
varieties  of  calculi:  — 
68* 


810  ANIMAL    FLUIDS. 

1.  Uric  Acid.  — These  are  among  the  most  common  :  externally  they  are 
smooth  or  warty,  of  yellowish  or  brownish  tint:  they  have  an  imperfectly 
crystalline,  distinctly  concentric  structure,  and  are  tolerably  hard.     Be- 
fore the  blowpipe  the  uric  acid  calculus  burns  away,  leaving  no  ash.     It  is 
insoluble  in  water,  but  dissolves  with  facility  in  caustic  potash,  with  but 
little  ammoniacal  odor :  the  solution  mixed  with  acid  gives  a  copious  white 
curdy  precipitate  of  uric  acid,  which  speedily  becomes  dense  and  crystal- 
line.    Cautiously  heated  with  nitric  acid,  and  then  mixed  with  a  little  am- 
monia, it  gives  the  characteristic  reaction  of  uric  acid,  viz.,  deep  purple- 
red  murexide. 

2.  Ammonium   Urate.  —  Calculi  of  ammonium  urate  much  resemble  the 
preceding;  they  are  easily  distinguished,  however.     The  powder  boiled  in 
water   dissolves,  and  the  solution   gives  a  precipitate  of  uric  acid  when 
mixed  with  hydrochloric  acid.     It  dissolves  also  in  hot  potassium  carbo- 
nate with  copious  evolution  of  ammonia. 

3.  Fusible   Calculus;     Calcium   Phosphate  icith  Ammonio-Magnesian   Phos- 
phate.—  This  is  one  of  the  most  common  kinds.     The  stones  are  usually 
white  or  pale-colored,  smooth,  earthy,  and  soft;  they  often  attain  a  large 
size.     Before  the  blowpipe  this  substance  blackens  from  animal  matter, 
which  calculi  always  contain ;  then  becomes  white,  and  melts  to  a  bead 
with  comparative  facility.     It  is  insoluble  in  caustic  alkali,  but  readily  sol- 
uble in  dilute  acids,  and  the  solution  is  precipitated  by  ammonia.     Calculi 
of  unmixed  calcium  phosphate  are  rare,  as  also  those  of  magnesium  and 
ammonium  phosphate;  the  latter  salt  is  sometimes  seen,  forming  small  bril- 
liant crystals,  in  cavities  in  the  fusible  calculus. 

4.  Calcium  Oxalate  Calculus;  Mulberry  Calculus.  —  The  latter  name  is  de- 
rived from  the  rough,  warty  character,  and   dark  blood-stained  aspect  of 
this  variety:  it  is  perhaps  the  worst  form  of  calculus.     It  is  exceedingly 
hard:  the  layers  are  thick  and  imperfectly  crystalline.     Before  the  blow- 
pipe the  calcium  oxalate  burns  to  a  carbonate  by  a  moderate  red  heat,  and, 
when  the  flame  is  strongly  urged,  to  quicklime.    It  is  soluble  in  moderately 
strong  hydrochloric  acid  by  heat,  and  very  easily  in  nitric  acid.     When 
finely  powdered   and   long  boiled  in  a  solution  of    potassium   carbonate, 
potassium  oxalate  may  be  discovered  in  the  filtered  liquor  when  carefully 
neutralized  by  nitric  acid,  by  white  precipitates  with  solutions  of  lime, 
lead,  and  silver.     A  sediment  of  calcium  oxalate  in  very  minute,  transpar- 
ent, octohedral  crystals,  only  to  be  seen  by  the  microscope,  is  of  common 
occurrence  in  urine,  in  which  a  tendency  to  deposits  of  urates  exists. 

5.  Cystine  and  Xanthine.  —  These   calculi  are  very  rare,  especially  the 
latter.     Calculi  of  cystine  or  cystic   oxide  are  very  crystalline,  and  often 
present  a  waxy  appearance  externally  :  sediments  of  cystic  oxide  are  some- 
times met  with.     This  substance  is  a  definite  crystallizable  organic  prin- 
ciple, containing  sulphur  to  a  large  amount,  its  formula  being  C3H7NS02. 
The  powdered  calculus  dissolves  in  great  part,  without  effervescence,  in 
dilute  acids  and  alkalies,  including  ammonia :   the  ammoniacal  solution  de- 
posits, by  spontaneous  evaporation,  small  but  beautiful  colorless  crystals, 
which   have  the  form   of  six-sided  prisms  and  tables.     It  forms  a  saline 
compound  with  hydrochloric  acid.      Caustic  alkalies  disengage  ammonia 
from  this  substance  by  continued  ebullition.     When  the  solution  in  nitric 
acid  is  evaporated  to  dryness,  it  blackens :  when  it  is  dissolved  in  large 
quantity  of  caustic  potash,  a  drop  of  solution  of  lead  acetate  added,  and  the 
whole  boiled,  a  black  precipitate  containing  lead  sulphide  makes  its  appear- 
ance.    By  these  characters  cystine  is  easily  recognized. 

Xanthine  or  xanthic  oxide,  also  a  definite  organic  principle,  C5H4N402,  is 
distinguished  by  the  peculiar  deep-yellow  color  produced  when  its  solution 
in  nitric  acid  is  evaporated  to  dryness:  it  is  soluble  in  alkalies  and  in  boil- 
ing, strong  hydrochloric  acid. 


SWEAT  —  BILE.  811 

Very  many  calculi  are  of  a  composite  nature,  the  composition  of  the  dif- 
ferent layers  being  occasionally  changed,  or  alternating:  thus,  mixed 
urates  aud  calcium  oxalate  are  not  unfrequently  associated  in  the  same 
stone. 

SWEAT.  — The  watery  fluid  poured  out  by  the  skin  contains  from  £  to  2 
per  cent,  of  solid  matter :  the  acidity  of  the  secretion  depends  on  organic 
acids,  chiefly  formic :  acetic  and  butyric  acids  also  exist  in  it.  Lactic  acid 
has  been  stated  to  be  absent,  even  in  rheumatism :  a  new  acid  named  sudoric 
acid,  and  somewhat  resembling  uric  acid  in  composition,  is  said  to  be  al- 
ways present.  In  disease,  and  in  health,  small  quantities  of  urea  also  exist 
in  sweat.  The  salts  in  the  sweat  are  chlorides  of  sodium  and  potassium. 
Phosphoric  acid,  lime,  magnesia,  and  iron  oxide  have  been  found. 

SALIVA  is  a  mixture  of  several  fluids  secreted  by  different  glands  of  the 
mouth.  Its  specific  gravity  is  from  1  *002  to  1  -009.  It  is  usually  alkaline :  dur- 
ing and  after  eating,  the  alkaline  reaction  increases,  while  it  decreases  by 
fasting.  It  contains  an  albuminous  substance,  ptyalin,  which  acts  on  starch, 
rapidly  changing  it  into  sugar.  The  secretion  of  the  submaxillary  gland, 
with  the  mucus  of  the  mouth,  chiefly  produces  this  effect.  On  the  passage 
of  the  food  into  the  acid  gastric  juice,  this  conversion  of  starch  into  sugar 
ceases.  The  second  remarkable  substance  in  saliva  is  potassium  sulpho- 
cyanate,  which  exists  in  very  small  quantities,  but  is  very  easily  detected. 
The  solid  constituents  of  the  saliva  are  about  1  per  cent.,  and  in  100  parts 
of  solid  constituents  from  7  to  21  parts  are  fixed  salts,  chiefly  chlorides, 
with  calcium  carbonate  and  phosphate. 

GASTRIC  JUICE  is  a  clear,  colorless,  transparent  fluid,  of  sp.  gr.  1-002, 
containing  1  to  2  per  cent,  of  solid  constituents,  chiefly  sodium  chloride  and 
lactate.  It  has  an  acid  reaction,  and  contains  hydrochloric,  lactic,  butyric, 
propionic,  and  acetic  acids.  It  is  slightly,  or  not.  at  all,  coagulable  by 
boiling,  though  it  contains  two  albuminous  substances,  one  insoluble  in  wa- 
ter and  absolute  alcohol,  the  osmazome  of  older  authors ;  the  other  soluble 
in  water,  but  precipitated  by  alcohol,  tannin,  mercuric  chloride,  and  lead- 
salts.  This  is  pepsin.  In  the  gastric  juice  of  man  it  exists  to  the  amount 
.of  0-319  per  cent.  When  the  gastric  juice  has  the  greatest  solvent  power, 
100  parts  of  fluid  are  saturated  by  1-25  parts  of  potash.  The  gastric  juice 
dissolves  the  albuminous  substances  taken  as  food,  and  slightly  changes 
their  reactions.  Thus  albumin,  fibrin,  casein,  legumin,  gluten,  and  chon- 
drin  give  rise  to  as  many  different  peptones.  (See  pepsin,  p.  801.) 

BILE.  —  This  is  a  secretion  of  a  very  different  character  from  the  pre- 
ceding :  the  largest  internal  organ  of  the  body,  the  liver,  is  devoted  to  its 
preparation,  which  takes  place  from  venous,  instead  of  arterial  blood.  Ac- 
cording to  Gorup-Besanez,  human  bile  contains  in  1000  parts  — 

Water 823—908 

Solid  matter  177—  92 


Bile  acids  with  alkali  .         .     108 —  56 
Fat  and  cholesterin  .         .  47 —  40 

Mucus  and  coloring  matter       24—  15 

Ash 11—     6 

In  its  ordinary  state,  bile  is  a  very  deep-yellow,  or  greenish,  viscid,  trans- 
parent liquid,  which  darkens  by  exposure  to  the  air,  and  undergoes  changes 
which  have  been  yet  imperfectly  studied.  It  has  a  disagreeable  odor,  a 
most  nauseous,  bitter  taste,  a  distinctly  alkaline  reaction,  and  is  miscililc 
with  ^ter  in  all  proportions.  When  evaporated  to  dryness  at  100°,  and 
treateu  with  alcohol,  the  greater  part  dissolves,  leaving  behind  an  in- 


312  ANIMAL   FLUIDS. 

soluble  jelly  of  mucus  of  the  gall-bladder.  This  alcoholic  solution  contains 
coloring  matter  and  cholesterin :  from  the  former  it  may  be  freed  by  di- 
gestion with  animal  charcoal,  and  from  the  latter  by  a  large  admixture  of 
ether,  in  which  the  bile  is  insoluble,  and  separates  as  a  thick,  syrupy,  and 
nearly  colorless  liquid.  The  coloring  matter  may  also  be  precipitated  by 
baryta-water. 

Pure  bile  thus  obtained,  when  evaporated  to  dryness  by  a  gentle  heat, 
forms  a  slightly  yellowish  brittle  mass,  resembling  gum-arabic.  It  is  com- 
pletely soluble  in  water  and  absolute  alcohol.  The  solution  is  not  affected 
by  the  vegetable  acids ;  hydrochloric  and  sulphuric  acids,  on  the  contrary, 
give  rise  to  turbidity,  either  immediately  or  after  a  short  interval.  Lead 
acetate  partly  precipitates  it ;  tribasic  acetate  precipitates  it  completely : 
the  precipitate  is  readily  soluble  in  acetic  acid,  in  alcohol,  and  to  a  cer- 
tain extent  in  excess  of  lead  acetate.  When  carbonized  by  heat,  and  in- 
cinerated, bile  leaves  between  11  and  12  per  cent,  of  ash,  consisting  chiefly 
of  sodium  carbonate,  with  a  little  common  salt  and  alkaline  phosphate. 
The  beautiful  researches  of  Strecker  show  that  bile  is  essentially  a  mix- 
ture of  the  sodium-salts  of  two  peculiar  acids,  resembling  the  resinous 
and  fatty  acids.  One  of  these  contains  nitrogen,  but  no  sulphur,  and  is 
termed  glycocholic  acid,  being  a  conjugated  compound*  of  a  non-nitrogenous 
acid,  cholic  acid,  with  the  azotized  substance  glycocine  (p.  614);  the  other, 
containing  nitrogen  and  sulphur,  is  called  taurocholic  acid,  being  a  conjugated 
compound  of  the  same  cholic  acid  with  a  body  to  be  presently  described 
under  the  name  of  taurin,  containing  both  nitrogen  and  sulphur.  The  rela- 
tive proportion  in  which  these  acids  occur  in  bile,  remains  pretty  constant 
with  the  same  animal,  but  varies  considerably  with  different  classes  of 
animals. 

GLYCOCHOLIC  ACID  may  be  thus  obtained: — When  ox-bile  is  perfectly 
dried  and  extracted  with  cold  absolute  alcohol,  and  after  nitration  is  mixed 
with  ether,  it  first  deposits  a  brownish  tough  resinous  mass,  and  after  some 
time,  stellate  crystals,  consisting  of  the  glycocholates  of  sodium  and  potas- 
sium. These  mixed  crystals  were  first  obtained  by  Plattner,  and  they  com- 
pose his  so-called  crystallized  bile. 

Glycocholic  acid  may  be  obtained  by  decomposing  sodium  glycocholate 
with  sulphuric  acid:  it  crystallizes  in  fine  white  needles  of  a  bitterish- 
sweet  taste,  is  soluble  in  water  and  alcohol,  but  only  slightly  in  ether,  and 
has  a  strong  acid  reaction.  It  is  represented  by  the  formula  C26H43N06. 
When  boiled  with  a  solution  of  potash,  the  acid  divides  into  cholic  acid  and 
glycocine : 

C26H43NOe     +     H20     =     C^H^     +     C2H5N02 
Glycocholic  Cholic  acid.        Glycocine. 

acid. 

Boiled  with  concentrated  sulphuric  or  hydrochloric  acid,  it  likewise  yields 
glycocine,  but  instead  of  cholic  acid,  another  white  amorphous  acid,  cholo- 
'idic  acid  (C24H3g04  —  cholic  acid  minus  1  molecule  of  water),  or,  if  the  ebul- 
lition has  continued  for  some  time,  a  resinous  substance,  from  its  insolu- 
bility in  water  called  dy  sly  sin  (C^HggOg  =  cholic  acid  minus  2  molecules 
of  water). 

TAUROCHOLIC  ACID  is  thus  procured :  — Ox-bile  is  freed  as  far  as  possible 
from  glycocholic  acid  by  means  of  neutral  lead  acetate,  and  is  then  pre- 
cipitated by  basic  lead  acetate,  to  which  a  little  ammonia  is  added.  The 
precipitate  is  decomposed  by  sodium  carbonate,  whereby  tolerably  pure 
sodium  taurocholate  is  obtained.  By  decomposing  the  taurocholate  of 
lead  with  sulphuretted  hydrogen,  taurocholic  acid  is  liberated.  This  sub- 

*  A  compound  is  sometimes  said  to  bo  "  conjugated"  Of  two  others,  when  it  co^ins  the 
elements  ot  those  two  bodies,  minus  the  elements  of  water. 


BILE.  813 

stance,  however,  which  was  previously  called  cholic  acid  and  bilin,  has 
never  been  obtained  in  the  pure  state;  its  formula,  as  inferred  from  the 
study  of  its  products  of  decomposition,  appears  to  be  C26H46NS07.  When 
boiled  with  alkalies,  it  divides  into  cholic  acid  and  taurin  : 


C^H^NSO,     +     H20     =     C24H400?     +     C2H7NS03 
Taurocholic  acid.  Cholic  acid.          Glycocine. 

With  boiling  acids  it  likewise  gives  taurin,  but  instead  of  cholic  acid 
either  choloi'dic  acid  or  dyslysin,  according  to  the  duration  of  the  ebullition. 

TAURIN,  C2H7NS03,  crystallizes  in  colorless  regular  hexagonal  prisms, 
which  have  no  odor  and  very  little  taste.  It  is  neutral  to  test-paper,  and 
permanent  in  the  air.  When  burnt,  it  gives  rise  to  much  sulphurous  acid. 
It  contains  upwards  of  25  per  cent,  of  sulphur.  It  is  easily  prepared  by 
boiling  purified  bile  for  some  hours  with  hydrochloric  acid.  After  nitra- 
tion and  evaporation,  the  acid  residue  is  treated  with  five  or  six  times  its 
bulk  of  boiling  alcohol,  from  which  the  taurin  separates  on  cooling.  Strecker 
made  many  attempts  to  prepare  taurin  artificially.  Ultimately  he  found 
that  when  ammonium  isethionate  (p.  527),  which  melts  at  180°,  is  heated 
to  210°  or  220°  C.  (410°-428°  F.),  it  loses  1  molecule  of  water,  and  becomes 
taurin.  The  substance  is  dissolved  in  water,  and  on  the  addition  of  alco- 
hol, gives  crystals  having  all  the  properties  of  taurin.  Kolbe  has  recently 
observed  the  formation  of  taurin  under  very  interesting  circumstances. 
The  treatment  of  potassium  isethionate  with  phosphorus  pentachloride 
gives  rise  to  a  heavy  oily  liquid,  with  simultaneous  formation  of  hydro- 
chloric acid  and  phosphorus  oxychloride.  This  oily  liquid,  the  so-called 
chloride  of  chlorethylsulphuric  acid,  C4H4C1S02C1,  when  mixed  with  water, 
yields  the  corresponding  acid,  chlorethylsulphuric  acid,  C2H6C1S03,  which 
on  digestion  with  an  excess  of  ammonia  at  100°,  produces  taurin:  C,H5 
C1S03  +  2NH3  =  NH4C1  -f  C2H7NS03. 

CHOLIC  ACID,  C24H4005,  crystallizes  in  tetrahedrons.  It  is  soluble  in  sul- 
phuric acid,  and  on  the  addition  of  a  drop  of  this  acid  and  a  solution  of 
sugar  (1  part  of  sugar  to  4  parts  of  water),  a  purple-violet  color  is  pro- 
duced, which  constitutes  Pettenkofer's  test  for  bile.  At  195°  C.  (383°  F.), 
.it  loses  a  molecule  of  water,  and  is  converted  into  choloidic  acid,  which 
change,  as  already  pointed  out,  is  also  produced  by  ebullition  with  acids. 

Cholic  acid  is  best  obtained  by  boiling  the  resinous  mass  precipitated  by 
ether  from  the  alcoholic  solution  of  the  bile,  with  a  dilute  solution  of  -potash 
for  24  or  36  hours,  till  the  amorphous  potassium-salt  that  has  separated 
begins  to  crystallize.  When  the  dark-colored  soft  mass  is  removed  from 
the  alkaline  liquid,  dissolved  in  water,  and  hydrochloric  acid  added,  a  little 
ether  causes  the  deposition  of  the  cholic  acid  in  crystals. 

The  principal  coloring  matter  of  the  bile  has  been  called  cholepj/rrhin. 
When  dry  it  is  reddish-brown  and  uncrystallizable,  insoluble  in  water, 
more  soluble  in  alcohol,  which  become?  yellow,  and  most  soluble  in  caustic 
alkali.  On  the  addition  of  nitric  acid  to  the  yellow  alkaline  solution,  a 
change  ensues.  It  passes  through  green,  blue,  violet,  and  red:  after  some 
time,  it  again  turns  yellow,  probably  in  consequence  of  a  gradual  process 
of  oxidation. 

Another  coloring  matter  has  been  called  biliverdin.  It  is  dark-green, 
amorphous  without  taste  or  smell,  insoluble  in  water,  slightly  soluble  in 
alcohol,  but  soluble  in  ether.  Berzelius  considers  it  to  be  identical  with 
chlorophyl,  the  green  coloring  matter  of  leaves. 

According  to  the  researches  of  Strecker  and  Gundelach,  pigs'  bile  differs 
from  the  bile  of  other  animals.  This  bile  contains  an  acid,  to  which  the 
name  of  glyco-hyocholic  acid  has  been  given.  It  may  be  prepared  in  the 
following  manner:  fresh  pigs'  bile  is  mixed  with  a  solution  of  sodium  sul- 


314  ANIMAL   FLUIDS. 

phate,  and  the  precipitate  obtained  is  dissolved  in  absolute  alcohol,  and 
decolorized  by  animal  charcoal.  From  this  solution  ether  throws  down  a 
sodium-salt,  which  on  addition  of  sulphuric  acid  yields  glyco-hyocholic 
acid  as  a  resinous  mass,  which  is  dissolved  in  alcohol  and  re-precipitated 

^Glyco-hyocholic  acid  contains  C^H^NOg.  When  heated  with  solutions 
of  the  alkalies,  it  undergoes  a  decomposition  perfectly  analogous  to  that 
of  glycocholic  acid,  splitting  up  into  glycocine  and  a  crystalline  acid,  very 
soluble  in  alcohol,  less  so  in  ether,  which  has  been  termed  hyocholic  acid. 
This  substance  contains  025114004 ;  and  the  change  is  represented  by  the 
following  equation: 

C27H43N05      +      H20      =       C25H4004      +      C2H5N02 
Glyco-hyocholic  Hyocholic  Glycocine. 

acid.  acid. 

When  boiled  with  acids,  glyco-hyocholic  acid  yields  likewise  glycocine, 
but  instead  of  hyocholic  acid,  a  substance  representing  the  dyslysin  of  the 
ordinary  bile,  which  might  be  termed  hyodyslysin.  The  composition  of 
hyodyslysin  is  C25H3803  =  hyocholic  acid  minus  H20. 

Pigs'  bile  contains  a  very  trifling  quantity  of  sulphur,  probably  in  the 
form  of  a  sulphuretted  acid  corresponding  to  taurocholic  acid  of  ox-bile. 
Strecker  believes  this  acid  to  contain  C27H45NS06:  it  might  be  called  tauro- 
hyocholic  acid;  when  boiled  with  an  alkali,  it  should  yield  taurin  and  hyo- 
cholic acid.  The  sulphuretted  acid  must  be  present  in  pigs'  bile  in  very 
minute  quantity;  it  is  even  less  known  than  taurocholic  acid. 

The  once  celebrated  oriental  bazoar  stones  are  biliary  calculi,  said  to  be 
procured  from  a  species  of  antelope:  they  have  a  brown  tint,  a  concentric 
structure,  and  a  waxy  appearance,  and  consist  essentially  of  a  peculiar 
and  definite  crystallizable  principle  called  Ulhofellic  acid.  To  procure  this 
substance,  the  calculi  are  reduced  to  powder  and  exhausted  with  boiling 
alcohol;  the  dark  solution  is  decolorized  by  animal  charcoal,  and  left  to 
evaporate  by  gentle  heat,  whereupon  the  lithofellic  acid  is  deposited  in 
small,  colorless,  transparent  six-sided  prisms.  It  is  insoluble  in  water, 
and  sparingly  soluble  in  ether,  but  dissolves  with  ease  in  alcohol:  it  melts 
at  94-5°  C.  (202°  F.),  and  at  a  higher  temperature  burns  with  a  smoky 
flame,  leaving  but  little  charcoal.  Lithofellic  acid  dissolves  without  decom- 
position in  concentrated  acetic  acid  and  in  oil  of  vitriol:  it  forms  a  soluble 
salt  with  potash,  and  dissolves  also  in  ammonia,  but  crystallizes  out  un- 
changed on  evaporation.  By  analysis,  lithofellic  acid  is  found  to  consist 
of  C^Hg/V 

The  liver  not  only  forms  bile  which  is  excreted,  but  it  also  effects  a  re- 
markable change  in  the  blood  that  passes  through  it.  M.  Bernard  dis- 
covered that  after  death,  sugar  could  be  detected  in  the  blood  from  the 
hepatic  vein,  whilst  no  sugar  was  found  in  blood  from  the  portal  vein.  In 
the  progress  of  his  researches  into  the  origin  of  this  sugar,  he  found  that 
a  glycogenic  substance  was  formed  in  the  substance  of  the  liver  itself,  and 
this  he  succeeded  in  extracting  and  isolating  (p.  594). 

PANCREATIC  FLUID  is  strongly  alkaline,  and  has  a  specific  gravity  of 
about  1-008  to  1-009,  containing  from  9  to  11  per  cent,  of  solid  constitu- 
ents; among  these  are  an  albuminous  substance  resembling  ptyalin,  to- 
gether withleucine,  guanine,  xanthine,  and  inosite,  and  about  1  per  cent,  of 
ash,  chiefly  chlorides  and  phosphates. 

It  has  three  distinct  actions  —  first  on  starch,  secondly  on  fat,  and  thirdly 
on  albuminous  matter.  Starch  is  converted  into  sugar  more  energetically 
by  the  pancreatic  fluid  than  by  the  saliva.  Fat  is  changed  into  fatty  acid 
and  glycerin  at  a  temperature  of  35° ;  and  boiled  albumin  and  fibrin  are 


CHYLE — MUCUS   AND    PUS.  815 

quickly  dissolved  at  the  same  temperature,  whilst  the  alkalescence  dis- 
tinctly remains. 

INTESTINAL  JUICE  is  a  colorless,  alkaline  fluid,  containing  from  3  to  4 
per  cent,  of  solid  constituents.  It  is  thought  to  be  capable  of  dissolving 
fibrinous  substances  only. 

CHYLE. — The  fluid  of  the  lacteal  vessels.  This  is  a  very  variable  fluid, 
milky,  and  feebly  alkaline.  Its  fibrin  begins  to  coagulate  when  taken  from 
the  vessels,  in  five  to  twelve  minutes,  and  is  perfectly  coagulated  in  two  to 
four  hours.  The  coagulum  is  much  smaller  and  weaker  than  that  of  the 
blood.  That  of  the  horse,  from  a  yellowish  color  changes  in  the  air  to 
light  red. 

The  albuminous  saline  serum  cpntains  very  finely  divided  molecules,  con- 
sisting of  the  minutest  particles  of  fatty  matter,  which  give  rise  to  the 
milkiness ;  also  larger  chyle  globules,  and  colorless  blood  globules.  Thus 
the  chyle  approximates  in  composition  and  properties  to  the  blood. 

In  the  chyle  of  the  horse  there  was  found: 

Water 91-00  to     96-00  per  cent. 

Fixed  constituents  .         .         .  9-00  4  00        " 

Nuclei  and  cells           .         .         .  Variable. 

Fibrin 0-19  0-7 

Albumin 1-93  4-34 

Fat 1-89  0-53 

Extractive  matter  free  from  salts  7-27  834 

Soluble  salts        .         .         .         .7-49  6-78 

Insoluble         .        .        .     about  2-00 

LYMPH  is  the  name  given  to  the  fluid  in  the  lymphatic  vessels.  It  is 
colorless,  has  an  alkaline  reaction,  and  coagulates  in  from  four  to  twenty 
minutes.  It  closely  resembles  the  blood  without  the  blood  globules.  It 
contains  colorless  globules,  resembling  the  white  globules  of  the  blood. 
It  contains  much  less  albumin  and  fat  than  the  serum  of  the  blood,  but 
more  water,  and  proportionately  more  extractive  matter. 

Closely  resembling  this  fluid  is  that  poured  out  by  serous  membranes  and 
the  cellular  tissue.  It  has  been  called  exsudation  fluid,  and  may  be  divided 
into  fibrinous  and  non-fibrinous.  It  may  be  considered  as  the  serum  of  the 
blood  with  or  without  fibrin,  which  is  far  more  commonly  present  than  has 
been  supposed. 

Mucus  AND  Pus. — The  slimy  matter  effused  upon  the  surface  of  various 
mucous  membranes,  as  the  lining  of  the  alimentary  canal,  that  of  the  blad- 
der, of  the  nose,  lungs,  &c.,  to  which  the  general  name  mucus  is  given,  is 
so  small  in  quantity,  and  so  variable  in  consequence  of  any  irritation  of 
the  membranes,  that  it  is  difficult  to  characterize.  It  always  contains  more 
or  less  epithelium  and  mucous  cells.  It  contains  a  peculiar  nitrogenous 
principle  to  which  the  name  of  mucin  has  been  given  (p.  800). 

Pus,  the  natural  secretion  of  a  wounded  or  otherwise  injured  surface,  is 
commonly  a  creamy,  white,  or  yellowish  liquid,  which,  under  the  micro- 
scope, appears  to  consist  of  multitudes  of  minute  globules  floating  in  a 
serum.  It  is  neither  acid  nor  alkaline. 

The  pus  globules  are  distended  by  very  dilute  mineral  and  organic  acids : 
imperfectly  dissolved  by  alkalies,  leaving  the  membrane  of  the  cells  ad- 
hering in  a  gelatinous  mass.  This  cell  membrane  is  an  albuminous  sub- 
stance, soluble  in  very  dilute  acids.  The  pus  serum  contains  more  or  less 
albumin,  in  all  respects  identical  with  that  of  the  blood  and  a  peculiar  sub- 
stance, pyin  (p.  800). 

The  quantity  of  fatty  substance  is  remarkable  in  pus,  varying  from  2  to 


816  ANIMAL    FLUIDS. 

6  per  cent.  As  much  as  1  per  cent,  of  cholesterin  has  been  found  to  be 
present;  but  neither  by  this  nor  by  any  other  character  can  the  passage  of 
mucus  into  pus  be  determined. 

MILK. The  peculiar  special  secretion  destined  for  the  nourishment  of 

the  young  is,  so  far  as  is  known,  very  much  the  same  in  flesh-eating  ani- 
mals and  in  those  which  live  exclusively  on  vegetable  food.  The  propor- 
tions of  the  constituents  may,  however,  sometimes  differ  to  a  considerable 
extent.  The  specific  gravity  varies  from  1  018  to  1-045.  It  will  be  seen 
hereafter  that  the  substances  present  in  milk  are  wonderfully  adapted  to 
the  office  of  providing  materials  for  the  rapid  growth  and  development  of 
the  animal  frame.  It  contains  an  azotized  matter,  casein  or  potassium  al- 
buminate,  fatty  principles,  and  a  peculiar  sugar,  and  lastly,  various  salts, 
among  which  may  be  mentioned  calcium  phosphate,  held  in  complete  solu- 
tion in  a  slightly  alkaline  liquid.  This  last  is  especially  important  to  a 
process  then  in  activity,  the  formation  of  bone. 

The  white,  and  almost  opaque,  appearance  of  milk  is  an  optical  illusion : 
examined  by  a  microscope  of  even  moderate  power,  it  is  seen  to  consist  of 
a  perfectly  transparent  fluid,  in  which  float  about  numbers  of  transparent 
globules :  these  consist  of  fat,  surrounded  by  an  albuminous  envelope,  which 
can  be  broken  mechanically,  as  in  the  churning,  or  dissolved  by  the  chemi- 
cal action  of  caustic  potash,  after  which,  on  agitating  the  milk  with  ether, 
the  fat  can  be  dissolved. 

When  milk  is  suffered  to  remain  at  rest  some  hours  at  the  ordinary  tem- 
perature of  the  air,  a  large  proportion  of  the  fat-globules  collect  at  the 
surface  into  a  layer  of  cream;  if  this  be  now  removed  and  exposed  for  some 
time  to  strong  agitation,  the  fat-globules  coalesce  into  a  mass,  and  the  re- 
maining watery  liquid  is  expelled  from  between  them  and  separated.  The 
butter  so  produced  must  be  thoroughly  washed  with  cold  water,  to  remove, 
as  far  as  possible,  the  last  traces  of  casein,  which  readily  putrefies,  and 
would  in  that  case  spoil  the  whole.  A  little  salt  is  usually  added. 

Ordinary  butter  still,  however,  contains  some  butter-milk,  and  when  in- 
tended for  keeping  should  be  clarified,  as  it  is  termed,  by  fusion.  The 
watery  part  then  subsides,  and  carries  with  it  the  residue  of  the  azotized 
matter.  The  flavor  is  unfortunately  somewhat  impaired  by  this  process. 
The  consistence  of  butter,  in  other  words,  the  proportions  of  solid  fat  and 
olein,  is  dependent  upon  the  season,  or  more  probably  upon  the  kind  of 
food ;  in  summer  the  oily  portion  is  always  more  considerable  than  in  win- 
ter. The  volatile  odoriferous  principle  of  butter,  butyrin,  has  been  already 
referred  to. 

The  casein  of  milk,  in  the  state  of  cheese,  is  in  many  countries  an  im- 
portant article  of  food.  The  milk  is  usually  heated  to  about49°C.  (120°  F.), 
and  coagulated  by  rennet,  or  an  infusion  of  the  stomach  of  the  calf  in 
water:  the  curd  is  carefully  separated  by  a  sieve  from  the  whey,  mixed 
with  a  due  proportion  of  salt,  and  sometimes  some  coloring  matter,  and 
then  subjected  to  strong  and  increasing  pressure.  The  fresh  cheese  so 
prepared,  being  constantly  kept  cool  and  dry,  undergoes  a  particular  kind 
of  putrefactive  fermentation,  very  little  understood,  by  which  principles 
are  generated  which  communicate  a  particular  taste  and  odor.  The  good- 
ness of  cheese,  as  well  as  much  of  the  difference  of  flavor  perceptible  in 
different  samples,  depends  in  great  measure  upon  the  manipulation:  the 
best  kinds  contain  a  considerable  quantity  of  fat,  and  are  made  with  new 
milk :  the  inferior  descriptions  are  made  with  skimmed  milk. 

Some  of  the  Tartar  tribes  prepare  a  kind  of  spirit  from  milk  by  suffering 
it  to  ferment,  with  frequent  agitation.  The  casein  converts  a  part  of  the 
milk-sugar  into  lactic  acid,  and  another  part  into  grape-sugar,  which  in 
turn  becomes  converted  into  alcohol.  Mare's  milk  is  said  to  answer  better 
for  this  purpose  than  that  of  the  cow. 


MILK. 


817 


In  a  fresh  state,  and  taken  from  a  healthy  animal,  milk  is  always  feebly 
alkaline.  When  left  to  itself,  it  very  soon  becomes  acid,  and  is  then  found 
to  contain  lactic  acid,  which  cannot  be  discovered  in  the  fresh  milk.  The 
alkalinity  is  due  to  the  soda  which  holds  the  casein  in  solution.  In  this 
soluble  form  casein  possesses  the  power  of  taking  up  and  retaining  a  very 
considerable  quantity  of  calcium  phosphate.  The  density  of  milk  varies 
exceedingly:  its  quality  usually  bears  an  inverse  ratio  to  its  quantity. 
From  an  analysis  of  cow-milk  in  the  fresh  state  by  Haidlen,*  the  following 
statement  of  its  composition  in  1000  parts  has  been  deduced: 


Water 

Butter 

Casein    .         .         ... 
Milk-sugar          .... 
Calcium  phosphate 
Magnesium     " 
Iron  "... 

Potassium  chloride     . 
Sodium  "  . 

Soda  in  combination  with  casein 


873-00 

30-00 

48-20 

43-90 

2-31 

0-42 

0-07 

1-44 

0-24 

0-42 

1000-00 


Human  milk  is  remarkable  for  the  difficulty  with  which  it  coagulates:  it 
generally  contains  a  larger  proportion  of  sugar  than  cow-milk,  but  scarcely 
differs  in  other  respects. 


*  Annalen  der  Cheraio  und  Pharmacie,  xiv.  263. 


69 


ON  THE  ANIMAL  TEXTURES. 


NERVOUS  SUBSTANCE;  CONTRACTILE  SUBSTANCE;  ELASTIC  TISSUE;   SKIN. 


NERVOUS  SUBSTANCE.  —  The  brain  and  nerves  contain  protagon  (p. 
cholesterin,  and  albuminous  matter.  In  the  watery  extract  are  found  cre- 
atin,  uric  acid,  xanthine,  sarcine,  inosite,  lactic  acid ;  in  the  ash,  sulphuric 
and  phosphoric  salts,  especially  potassium  salts,  a  little  sodium  chloride, 
calcium  and  magnesium.  The  substance  yields  from  75  to  80  per  cent,  of 
water,  and  3  to  4  of  ash. 

CONTRACTILE  SUBSTANCE. — This,  like  nerve  substance,  consists  of  many 
different  compounds.  It  contains  74  to  80  per  cent,  water,  and  26  to  20 
solid  constituents.  The  most  remarkable  of  these  is  syntonin,  Liebig's 
fibrin  of  flesh  (see  p.  795).  Casein,  albumin,  creatin,  hypoxanthine,  uric 
acid,  and  fat  are  also  present.  The  solid  constituents  contain  4  to  5  per 
cent,  of  ash.  Potash,  soda,  lime,  magnesia,  sulphuric,  phosphoric,  and 
hydrochloric  acids  are  present. 

ELASTIC  TISSUE;  SKIN. — The  tendons  and  skin  consist  also  of  many  dif- 
ferent substances.  Of  these  elastin  (see  p.  802)  is  one  of  the  most  remark- 
able. A  cellular  tissue,  which  yields  gelatin  when  long  boiled,  is  another 
constituent.  These  two  principles  combine  with  tannic  acid,  forming 
leather. 

The  principle  of  tanning,  of  such  great  practical  value,  is  easily  ex- 
plained. When  the  skin  of  an  animal,  carefully  deprived  of  hair,  fat,  and 
other  impurities,  is  immersed  in  a  dilute  solution  of  tannic  acid,  the  cellu- 
lar and  elastic  tissues  gradually  combine  with  that  substance  as  it  pene- 
trates inwards,  forming  a  perfectly  insoluble  compound,  which  resists  pu- 
trefaction completely :  this  is  leather.  In  practice,  lime-water  is  used  for 
cleansing  and  preparing  the  skin,  and  an  infusion  of  oak-bark,  or  some- 
times catechu,  or  other  astringent  matter,  as  the  source  of  tannic  acid. 
The  process  itself  is  necessarily  a  slow  one,  as  dilute  solutions  only  can  be 
safely  used.  Of  late  years,  however,  various  contrivances,  some  of  which 
show  great  ingenuity,  have  been  adopted,  with  more  or  less  success,  for 
quickening  the  operation.  All  leather  is  not  tanned:  glove  leather  is 
dressed  with  alum  and  common  salt,  and  afterwards  treated  with  a  prepa- 
ration of  the  yolks  of  eggs,  which  contain  an  albuminous  matter  and  a 
yellow  oil.  Leather  of  this  kind  still  yields  a  size  by  the  action  of  boiling 
water. 

BONES. — At  the  age  of  21  years  the  weight  of  the  skeleton  is  to  that 
of  the  whole  body  as  10-5  to  100  in  man,  and  as  8-5  to  100  in  woman,  the 
weight  of  the  body  being  about  125  or  130  Ibs.  Bones  are  constructed  of 
organic  matter  called  osse'in,  which  yields  gelatin  on  boiling,  and  is  made 
stiff  by  insoluble  earthy  salts,  of  which  calcium  phosphate,  (P04)2Ca//3,  is 
the  most  abundant.  The  proportions  of  earthy  and  animal  matter  vary 
very  much  with  the  kind  of  bone  and  with  the  age  of  the  individual,  as 

818 


BONES.  819 

will  be  seen  in  the  following  table,  in  which  the  corresponding  bones  of  an 
adult  and  of  a  still-born  child  are  compared : 

ADULT.  CHILD. 


Inorganic        Organic                     Inorganic  Organic 

matter.         matter.                       matter.  matter. 

Femur      .       .         62-49          37-51                     57-51  4249 

Humerus     .       .      63.02          36-98                    58-08  41-92 

Radius      .       .         60-51           39-49                    56-50  43-50 

Os  temporum    .       63-50          36  50                    55-90  44-10 

Costa.       .       .         57-49          42-51                   53-75  46-25 

The  bones  of  the  adult  are  constantly  richer  in  earthy  salts  than  those  of 
the  infant. 

The  following  complete  comparative  analysis  of  human  and  ox  bones  is 
due  to  Berzelius: 

Human  bones.  Ox  bones. 

Animal  matter  soluble  by  boiling    .        .      32-17  \ 
Vascular  substance     ....  1-13  / 

Calcium  phosphate,  with  a  little  )                   K0  A,  e_  OK 

calcium  fluoride       .         .      }'         '      53'04 

Calcium  carbonate      ....            11-30  3-85 

Magnesium  phosphate     ....         1-16  2-05 

Soda,  and  a  little  common  salt    .         .            1-20  3-45 


100-00          100-00 

The  teeth  have  a  very  similar  composition,  but  contain  less  organic  mat- 
ter :  their  texture  is  much  more  solid  and  compact.  The  enamel  does  not 
contain  more  than  2  or  3  per  cent,  of  animal  matter,  whilst  81  to  88  per 
cent,  of  calcium  phosphate  with  7  or  8  per  cent,  of  carbonate  are  present ; 
and  more  calcium  fluoride  than  in  the  bones. 


ON  CHEMICAL  FUNCTIONS  IN  ANIMALS. 


RESPIRATION,  DIGESTION,  NUTRITION. 


RESPIRATION.  —  The  simplest  view  that  can  be  taken  of  a  respiratory 
organ  in  an  air-breathing  animal,  is  that  of  a  little  membranous  bag,  satu- 
rated with  moisture,  and  containing  air,  over  the  surface  of  which  mean- 
der minute  blood-vessels,  whose  contents,  during  the  passage,  are  thus 
subjected  to  the  chemical  action  of  the  air,  through  the  substance  of  the 
membranes,  and  in  virtue  of  the  solubility  of  the  gaseous  matter  itself  in 
the  water  with  which  the  membranes  are  imbued.  In  some  of  the  lower 
classes  of  animals,  where  respiration  is  sluggish  and  inactive,  these  air- 
cells  are  few  and  larger ;  but  in  the  higher  kinds  they  are  minute,  and 
greatly  multiplied  in  number,  in  order  to  gain  extent  of  surface,  each  com- 
municating with  the  external  air  by  the  windpipe  and  its  ramifications. 

Respiration  is  performed  by  the  agency  of  the  muscles  which  lie  between 
and  about  the  ribs,  and  by  the  diaphragm.  In  an  ordinary  respiration, 
from  22  to  43  cubic  inches  of  air  are  thrown  out.  It  has  been  said  that  as 
little  as  3  and  as  much  as  100  cubic  inches  have  been  expired.  By  a  forced 
eifort,  ordinarily  from  50  to  60  cubic  inches  are  expelled,  and  after  a  full 
inspiration  possibly  from  100  to  300  cubic  inches  may  be  expired.  Even 
then  the  lungs  are  not  emptied  of  air.  The  residual  quantity  may  be  esti- 
mated at  from  40  to  260  cubic  inches.  After  an  ordinary  expiration  a  fur- 
ther quantity  of  air,  amounting  to  from  77  to  170  cubic  inches,  may  be 
expired,  and  after  an  ordinary  inspiration,  by  the  deepest  sigh,  from  119 
to  200  more  cubic  inches  may  be  drawn  into  the  lungs.  Usually  about  15 
respirations  are  made  in  a  minute  :  the  number,  however,  even  in  health, 
varies  from  9  to  20. 

The  expired  air  is  found  to  have  undergone  a  remarkable  change:  it  is 
loaded  with  aqueous  vapor,  while  a  very  large  proportion  of  oxygen  has 
disappeared,  and  its  place  been  supplied  by  carbon  dioxide,  air  once 
breathed  containing  enough  of  that  gas  to  extinguish  a  taper.  The  quan- 
tity of  this  gas  is  very  liable  to  variation;  usually  from  8-3  to  6-2  per 
cent,  of  carbon  dioxide  is  found  to  be  present;  when  the  respirations  are 
few,  the  carbon  dioxide  is  greatest,  when  many,  least:  thus  with  6  respi- 
rations per  minute,  55  per  cent,  has  been  found:  with  48  respirations, 
2-9  per  cent.  A  full  meal,  cold  weather,  and  increased  barometric  pres- 
sure, increase  the  carbon  dioxide.  Heat,  alcohol,  tea,  and  diminished  pres- 
sure, lessen  the  carbon  dioxide ;  age  and  sex  produce  definite  effects.  It 
appears  most  probable  that  nitrogen  in  small  quantities  is  exhaled. 

Whatever  may  be  the  difficulties  attending  the  investigation  of  these  sub- 
jects,—  and  difficulties  there  are,  as  the  discrepant  results  of  the  experi- 
ments prove,  —  one  thing  is  clear:  namely,  that  quantities  of  hydrogen 
and  carbon  are  daily  oxidized  in  the  body  by  the  free  oxygen  of  the  atmos- 
phere, and  their  products  expelled  from  the  system  in  the  shape  of  water 
and  carbon  dioxide.  Now,  if  it  be  true  that  the  heat  developed  in  the  act 
of  combination  is  a  constant  quantity,  and  no  proposition  appears  more 
reasonable,  part  or  all  of  the  high  temperature  of  the  body  must  be  the 
result  of  this  exertion  of  chemical  force. 

820 


BESPIRATION.  821 

The  oxidation  of  combustible  matter  in  the  blood  is  effected  in  the  capil- 
laries of  the  whole  body,  not  in  the  lungs,  the  temperature  of  which  scarcely 
exceeds  that  of  the  other  parts.  The  oxygen  of  the  air  is  taken  up  in  the 
lungs,  and  carried  by  the  blood  to  the  distant  capillary  vessels ;  by  the  aid 
of  which,  secretions,  and  all  the  mysterious  functions  of  animal  life,  are 
undoubtedly  performed:  here  the  combustion  takes  place,  although  how  this 
happens,  and  what  the  exact  nature  of  the  combustible  may  be,  beyond  the 
simple  fact  of  its  containing  carbon  and  hydrogen,  yet  remains  a  matter 
of  conjecture.  The  carbon  dioxide  produced  is  held  in  solution  by  the  now 
venous  blood,  and  probably  confers,  in  great  measure,  upon  the  latter  its 
dark  color  and  deleterious  action  upon  the  nervous  system.  Once  more 
poured  into  the  heart,  and  by  that  organ  driven  into  the  second  set  of  capil- 
laries bathed  with  atmospheric  air,  this  carbon  dioxide  is  conveyed  out- 
wards, through  the  wet  membrane,  by  a  kind  of  false  diffusion,  constantly 
observed  under  such  circumstances  ;  while  at  the  same  time  oxygen  is,  by 
similar  means,  carried  inwards,  and  the  blood  resumes  its  bright-red  color, 
and  its  capability  of  supporting  life  Much  of  this  oxygen  is,  no  doubt, 
simply  dissolved  in  the  serum.  The  haemoglobin  of  the  corpuscles,  becom- 
ing oxyhaemoglobin  in  the  arteries,  acts  as  a  carrier  of  another  portion 
(p.  798).  Mulder  considers  the  fibrin  to  act  in  the  same  manner,  being 
true  fibrin  in  the  veins,  and,  in  part  at  least,  oxidized  in  the  arteries. 

It  would  be  very  desirable  to  show,  if  possible,  that  the  quantity  of  com- 
bustible matter  daily  burned  in  the  body  is  adequate  to  the  production  of 
the  heating  eifects  observed.  Something  has  been  done  with  respect  to 
the  carbon.  Comparison  of  the  quantities  and  composition  of  the  food  con- 
sumed by  an  individual  in  a  given  time,  and  of  the  excretions,  shows  an 
excess  of  carbon  in  the  former  over  the  latter,  amounting,  in  some  cases, 
according  to  Liebig's  high  estimate,*  to  14  ounces:  the  whole  of  which  is 
thrown  off  in  the  state  of  carbon  dioxide,  from  the  lungs  and  skin,  in  the 
space  of  twenty-four  hours.  This  statement  applies  to  the  case  of  healthy, 
vigorous  men,  much  employed  in  the  open  air,  and  supplied  with  abundance 
of  nutritious  food.  Females,  and  persons  of  weaker  habits,  who  follow  in- 
door pursuits  in  warm  rooms,  consume  a  much  smaller  quantity :  their  res- 
piration is  less  energetic,  and  the  heat  generated  less  in  amount.  Those 
who  inhabit  very  cold  countries  are  well  known  to  consume  enormous  quan- 
tities of  food  of  a  fatty  nature,  the  carbon  and  hydrogen  of  which  are, 
without  doubt,  chiefly  employed  in  the  production  of  animal  heat.  These 
people  live  by  hunting:  the  muscular  exertion  required  quickens  and 
deepens  the  breathing ;  while,  from  the  increased  density  of  the  air,  a 
greater  weight  of  oxygen  is  taken  into  the  lungs,  and  absorbed  into  the 
blood  at  each  inspiration.  In  this  manner  the  temperature  of  the  body  is 
kept  up,  notwithstanding  the  piercing  external  cold  :  a  most  marvellous 
adjustment  of  the  nature  of  the  food,  and  even  of  the  inclinations  and  ap- 
petite of  the  man,  to  the  circumstances  of  his  existence,  enable  him  to  bear 
with  impunity  an  atmospheric  temperature  which  would  otherwise  injure 
him. 

The  carbon  consumed  in  respiration  in  one  day,  by  a  horse  moderately 
fed,  amounted,  in  a  valuable  experiment  of  M.  Boussingault,f  to  79  ounces; 
that  consumed  by  a  cow  to  71  ounces.  The  determination  was  made  in  the 
manner  just  mentioned,  viz.,  by  comparing  the  quantity  and  composition 
of  the  food. 

New  and  very  important  experiments  on  respiration  have  been  made  in 
Munich  by  Drs.  Pettenkofer  and  Voit. 

The  apparatus  was  large  enough  to  allow  a  man  to  breathe  and  move  as 
in  an  ordinary  dwelling-room  for  twenty-four  hours  at  least.  The  air 

*  Animal  Chemistry,  p.  14. 
f  Annales  de  Chimie,  vol.  Ixxi.  pp.  136  and  137. 
69* 


822  DIGESTION   AND   NUTRITION. 

could  be  changed  to  the  extent  of  from  fifteen  to  seventy-five  cubic  meters 
an  hour :  the  chemical  difference  between  the  air  that  went  in  and  that 
which  came  out  was  determined. 

The  King  of  Bavaria  gave  about  $3000  for  the  construction  of  the  appa- 
ratus, and  it  acted  so  well  that  the  quantity  of  carbon  and  of  hydrogen  in 
a  stearin  candle  burnt  in  the  apparatus  could  be  determined  as  accurately 
by  the  quantity  of  carbon  dioxide  and  water  produced  as  by  an  organic 
analysis. 

A  dog  and  a  man  were  experimented  on.  In  the  dog  the  amount  of  car- 
bon dioxide  expired  was  least  after  ten  days  of  hunger;  when  a  full  diet 
of  flesh  and  fat  was  taken,  three  times  as  much  carbon  dioxide  was  pro- 
duced. The  urea  was  increased  twenty-two  times  as  much  as  during  star- 
vation. 

In  man  not  quite  one-third  more  carbon  dioxide  was  produced  when  full 
diet  was  taken  than  was  found  during  starvation. 

From  the  amount  of  carbon  dioxide  and  urea  formed  when  animal  food 
alone  was  taken,  it  appears  that  soni'i  fatty  matter  must  be  produced  and 
retained  in  the  system. 

Starch  and  sugar  diet  do  not  appear  to  cause  a  deposit  of  fat  directly, 
though  they  may  do  so  indirectly. 

Careful  determination  of  the  amount  and  composition  of  the  food  and 
oxygen  consumed  led  to  the  belief  that  hydrogen  and  light  carburetted 
hydrogen  (CH4)  were  given  off  in  respiration.  This  is  fully  confirmed  by 
these  experiments.  It  follows  from  this  important  fact,  first,  that  the  car- 
bon dioxide  produced  cannot  be  looked  on  as  the  measure  of  the  amount 
of  oxygen  taken  from  the  air,  and  secondly,  that  hydrogen  cannot  be  as- 
sumed to  be  oxidized  in  the  body  in  preference  to  carbon. 

In  a  paper  read  to  the  Academy  of  Sciences  at  Munich,  November,  1866, 
the  authors  give  their  latest  results.  They  find  that  the  proportion  of  car- 
bon dioxide  exhaled  to  oxygen  inhaled  is  much  greater  in  the  day  than  in 
the  night ;  with  perfect  rest  day  and  night,  nearly  twice  as  much ;  with 
active  motion  during  the  day,  nearly  three  times  as  much.  The  amount 
of  oxygen  taken  in  during  rest  by  day  is  only  half  as  much  as  is  taken 
in  at  night,  and  after  active  motion  the  amount  of  oxygen  taken  in  at 
night  is  still  more.  In  diabetes  the  proportion  of  carbon  dioxide  exhaled 
by  day  to  the  oxygen  inhaled  is  less  than  in  health  ;  at  night  the  amount 
of  oxygen  inhaled  may  be  less  than  half  the  amount  that  would  be  inhaled 
in  health.  When  one-third  of  the  blood  consisted  of  white  globules,  the 
proportion  of  carbon  dioxide  exhaled  to  oxygen  inhaled  by  day  was  much 
less  than  in  health,  and  the  amount  of  oxygen  taken  in  at  night  was  even 
less  than  is  taken  in  during  the  day. 

DIGESTION  AND  NUTRITION. — The  various  substances  of  which  the  food 
of  man  is  composed  must  become  finely  divided  in  order  to  admit  of  their 
passage  into  the  blood.  In  the  process  of  fine  division  or  solution  different 
substances  undergo  different  changes  in  the  alimentary  canal.  We  learn 
nothing  by  saying  that  the  food  is  converted  into  chyme,  and  the  chyme  is 
changed  into  chyle ;  but  each  animal  and  vegetable  substance  must  be  con- 
sidered separately,  as  regards  the  changes  it  undergoes  when  exposed  to 
the  action  of  the  different  fluids  which  constitute  the  saliva,  gastric  juice, 
bile,  pancreatic  juice,  and  intestinal  fluid. 

Shortly,  it  may  be  stated  that  mineral  substances,  when  exposed  to  these 
reagents,  are  but  little  changed. 

Hydrates  of  carbon,  as  cellulose,  gum,  starch,  sugar,  are  each  acted  on 
differently  by  different  secretions ;  thus  cellulose  and  gum  are  probably 
not  changed.  Starch,  by  the  action  of  the  saliva  and  pancreatic  fluid,  be- 
comes dextrin  and  glucose.  Cane-sugar  is  changed  by  gastric  juice  and 


DIGESTION    AND   NUTRITION.  823 

heat  into  glucose,  and  all  sugars  are  ultimately  changed  by  the  intestinal 
fluid  and  heat  into  acids. 

Fat  is  unchanged  by  the  saliva  and  gastric  juice ;  but  the  bile,  the  pan- 
creatic and  intestinal  fluid,  change  the  fat  into  a  finely  divided  emulsion, 
but  effect  no  perfect  solution. 

Albuminous  substances,  as  albumin,  fibrin,  casein,  globulin,  undergo 
subdivision  and  solution  chiefly  in  the  stomach.  Each  of  these  substances 
is  chemically  changed  in  the  process  of  solution  by  the  gastric  juice  (p.  797) 
into  corresponding  peptones.  The  rate  of  change  and  of  solution  depends 
on  the  mechanical  subdivision  as  well  as  on  the  chemical  properties  of  the 
different  substances  acted  on. 

Gelatinous  substances  are  changed  chemically  by  the  gastric  juice,  and 
thereby  lose  the  property  of  gelatinizing  when  cold.  But  this  change  is 
not  requisite  to  their  solution,  which  occurs  so  readily  that  these  sub- 
stances can  often  be  taken  as  food  when  albuminous  substances  would  re- 
main in  the  stomach  undissolved. 

The  constant  and  unceasing  waste  of  the  animal  body  in  the  process  of 
respiration,  and  in  the  various  secondary  changes  therewith  connected, 
necessitates  an  equally  constant  repair  and  renewal  of  the  whole  frame  by 
the  deposition  or  organization  of  matter  from  the  blood,  which  is  thus 
gradually  impoverished.  To  supply  this  deficiency  of  solid  material  in  the 
circulating  fluid  is  the  office  of  the  food.  The  striking  contrast  which  at 
first  appears  in  the  nature  of  the  food  of  the  two  great  classes  of  animals, 
the  vegetable  feeders  and  the  carnivorous  races,  diminishes  greatly  on 
close  examination  :  it  will  be  seen  that,  so  far  as  the  materials  of  blood,  or, 
in  other  words,  those  devoted  to  the  repair  and  sustenance  of  the  body  it- 
self, are  concerned,  the  process  is  the  same.  In  a  flesh-eating  animal  great 
simplicity  is  observed  in  the  construction  of  the  digestive  organs ;  the 
stomach  is  a  mere  enlargement  of  the  short  and  simple  alimentary  canal; 
and  the  reason  is  plain :  the  food  of  the  creature,  flesh,  is  absolutely  iden- 
tical in  composition  with  its  own  blood,  and  with  the  body  that  blood  is 
destined  to  nourish.  In  the  stomach  it  undergoes  mere  solution,  being 
brought  into  a  state  fitted  for  absorption  by  the  lacteal  vessels,  by  which 
it  is  nearly'  all  taken  up,  and  at  once  conveyed  into  the  blood  :  the  excre- 
ments of  such  animals  are  little  more  than  the  comminuted  bones,  feathers, 
hair,  and  other  matters  which  refuse  to  dissolve  in  the  stomach.  The  same 
condition,  that  the  food  employed  for  nourishment  of  the  body  must  have 
the  same,  or  nearly  the  same,  chemical  composition  as  the  body  itself,  is 
really  fulfilled  in  the  case  of  animals  that  live  exclusively  on  vegetable 
substances.  It  has  been  shown*  that  certain  of  the  azotized  principles  of 
plants,  which  often  abound,  and  are  never  altogether  absent,  have  a  chem- 
ical composition  and  assemblage  of  properties  which  assimilate  them  in 
the  closest  manner,  and  it  is  believed  even  identify  them,  with  the  azotized 
principles  of  the  animal  body :  vegetable  albumin,  fibrin,  and  casein  are 
scarcely  to  be  distinguished  from  the  bodies  of  the  same  name  extracted 
from  blood  and  milk. 

If  a  portion  of  wheaten  flour  be  made  into  a  paste  with  water,  and  cau- 
tiously washed  on  a  fine  metallic  sieve,  or  in  a  cloth,  a  grayish,  adhesive, 
elastic,  insoluble  substance  will  be  left,  called  gluten  or  glutin,  and  a  milky 
liquid  will  pass  through,  which  by  a  few  hours'  rest  becomes  clear  by  de- 
positing a  quantity  of  starch.  If  now  this  liquid  be  boiled,  it  becomes 
again  turbid  from  the  production  of  a  flocculent  precipitate,  which,  when 
collected,  washed,  dried,  and  purified  from  fat  by  boiling  with  ether,  is 
found  to  have  the  same  composition  as  animal  albumin.  The  glutin  itself 
is  a  mixture  of  true  vegetable  fibrin,  and  a  small  quantity  of  a  peculiar 
azotized  matter  called  gliadin,  to  which  its  adhesive  properties  are  due. 
*  Liebig,  Ann.  Ch.  Pharm.  xxxix.  129. 


324  DIGESTION   AND   NUTRITION. 

The  gliadin  may  be  extracted  by  boiling  alcohol,  together  with  a  thick, 
fluid  oil,  which  is  separable  by  ether:  it  is  gluey  and  adhesive,  quite  in- 
soluble in  water,  and  when  dry,  hard  and  translucent  like  horn ;  it  dis- 
solves readily  in  dilute  caustic  alkali,  and  also  in  acetic  acid.  The  fibrin 
of  other  grain  is  unaccompanied  by  gliadin :  barley  and  oatmeal  yield  no 
glutin,  but  inadherent  filaments  of  nearly  pure  fibrin. 

Vegetable  albumin  in  a  soluble  state  abounds  in  the  juice  of  many  soft 
succulent  plants  used  for  food:  it  may  be  extracted  from  potatoes  by  ma- 
cerating the  sliced  tubers  in  cold  water  containing  a  little  sulphuric  acid. 
It  coagulates  when  heated  to  a  temperature  dependent  upon  the  degree  of 
concentration,  and  cannot  be  distinguished  when  in  this  state  from  boiled 
white  of  egg  in  a  divided  condition. 

Almonds,  peas,  beans,  and  many  of  the  oily  seeds,  contain  a  principle 
which  bears  the  most  striking  resemblance  to  the  casein  of  milk.  When  a 
solution  of  this  substance  is  heated,  no  coagulation  occurs,  but  a  skin  forms 
on  the  surface,  just  as  with  boiled  milk.  It  is  coagulable  by  alcohol,  and 
by  acetic  acid,  the  last  being  a  character  of  importance.  Such  a  solution, 
mixed  with  a  little  sugar  —  an  emulsion  of  sweet  almonds,  for  instance  — 
and  left  to  itself,  soon  becomes  sour  and  curdy,  and  exhales  an  offensive 
smell:  it  is  then  found  to  contain  lactic  acid. 

All  these  substances  dissolve  in  caustic  potash,  with  production  of  a 
small  quantity  of  alkaline  sulphide :  the  filtered  solution  mixed  with  ex- 
cess of  acid  gives  precipitates  of  protein. 

The  following  is  the  composition  in  100  parts  of  vegetable  albumin  and 
fibrin :  it  will  be  seen  that  they  agree  very  closely  with  the  results  before 
given : 

Albumin.  Fibrin. 

Carbon 65  01  54-60 

Hydrogen 7-23  7-30 

Nitrogen 15-92  1581 

Oxygen,  sulphur,  and  phosphorus       .         21-84  22-29 

100-00  10.0-00 

The  composition  of  vegetable  casein,  or  legumin,  has  not  been  so  well 
made  out :  so  much  discrepancy  appears  in  the  analyses  as  to  lead  to  the 
supposition  that  different  substances  have  been  operated  upon. 

The  great  bulk,  however,  of  the  solid  portion  of  the  food  of  the  herbi- 
vora  consists  of  bodies  which  do  not  contain  nitrogen,  and  therefore  can- 
not yield  sustenance  in  the  manner  described:  some  of  these,  as  vegetable 
fibre  or  ligniri,  and  waxy  matter,  pass  unaltered  through  the  alimentary 
canal;  others,  as  starch,  sugar,  gum,  and  perhaps  vegetable  fat,  are  ab- 
sorbed into  the  system,  and  afterwards  disappear  entirely :  they  are  sup- 
posed to  contribute  very  largely  to  the  production  of  animal  heat. 

On  these  principles,  Liebig*  made  the  now  doubtful  distinction  between 
what  he  terms  plastic  elements  of  nutrition  and  elements  of  respiration.  In  the 
former  class  he  placed  — 

Vegetable  fibrin, 

Vegetable  albumin, 

Vegetable  casein, 

Animal  flesh, 

Blood. 
To  the  latter : 


Fat, 
Starch, 
Gum, 
Cane-sugar, 


Grape-sugar, 
Milk-sugar, 
Pectin, 
Alcohol  ? 


*  Auimal  Chemistry,  p.  96. 


DIGESTION   AND    NUTRITION.  825 

When  the  muscular  movements  of  a  healthy  animal  are  restrained,  a 
genial  temperature  kept  up,  and  an  ample  supply  of  food  containing  much 
amylaceous  or  oily  matter  given,  an  accumulation  of  fat  in  the  system  rap- 
idly takes  place :  this  is  well  seen  in  the  case  of  stall-fed  cattle.  On  the 
other  hand,  when  food  is  deficient,  and  much  exercise  is  taken,  emaciation 
results.  These  effects  are  ascribed  to  differences  in  the  activity  of  the 
respiratory  function :  in  the  first  instance,  the  heat-food  is  supplied  faster 
than  it  is  consumed,  and  hence  accumulates  in  the  form  of  fat;  in  the 
second,  the  conditions  are  reversed,  and  the  creature  is  kept  in  a  state  of 
leanness  by  its  rapid  consumption.  The  fat  of  an  animal  appears  to  be  a 
provision  of  Nature  for  the  maintenance  of  life  during  a  certain  period 
under  circumstances  of  privation. 

The  origin  of  fat  in  the  animal  body  was  at  one  time  the  subject  of  much 
discussion.  On  the  one  hand  it  was  contended  that  satisfactory  evidence 
exists  of  the  conversion  of  starch  and  saccharine  substances  into  fat,  by 
separation  of  carbon  and  oxygen,  the  change  somewhat  resembling  that 
of  vinous  fermentation ;  it  was  argued  on  the  other  side,  that  oily  or  fatty 
matter  is  invariably  present  in  the  food  supplied  to  the  domestic  animals, 
and  that  this  fat  is  merely  absorbed  and  deposited  in  the  body  in  a  slightly 
modified  state.  The  question  has  been  decided  in  favor  of  the  first  of  these 
views,  which  was  enunciated  by  Liebig,  by  the  very  chemist  who  formerly 
advocated  the  second  opinion.  By  a  series  of  very  beautiful  experiments, 
MM.  Dumas  and  Milne  Edwards  proved  that  bees  exclusively  feeding  upon 
sugar  were  still  capable  of  producing  wax,  which  is  known  to  be  a  veri- 
table fat. 

The  food  of  animals,  or  rather  that  portion  of  the  food  which  is  destined 
to  the  repair  and  renewal  of  the  frame  itself,  is  thus  seen  to  consist  of  sub- 
stances identical  in  composition  with  the  body  it  is  to  nourish,  or  requir- 
ing but  little  chemical  change  to  become  so. 

The  chemical  phenomena  observed  in  the  animal  system  resemble  so 
far  those  produced  out  of  the  body  by  artificial  means,  that  they  are  all,  or 
nearly  all,  so  far  as  is  known,  changes  in  a  descending  series.  Albumin 
and  fibrin  are  probably  more  complex  compounds  than  gelatin  or  the  mem- 
brane which  furnishes  it:  this,  in  turn,  has  a  far  greater  complexity  of 
constitution  than  urea,  which  contains  most  of  the  azotized  matter  that  is 
•  rejected  from  the  body.  The  animal  lives  by  the  assimilation  into  its  own 
substance  of  the  most  complex  and  elaborate  products  of  the  organic  king- 
dom ;  —  products  which  are,  and,  apparently,  can  only  be,  formed  under 
the  influence  of  vegetable  life. 

The  existence  of  the  plant  is  maintained  in  a  manner  strikingly  dissimi- 
lar:—  the  food  supplied  to  vegetables  is  wholly  inorganic ;  the  carbon  di- 
oxide and  nitrogen  of  the  atmosphere ;  the  water  which  falls  as  rain,  or  is 
deposited  as  dew;  the  minute  traces  of  ammoniacal  vapor  present  in  the 
air ;  the  alkali  and  saline  matter  extracted  from  the  soil ;  —  such  are  the 
substances  which  yield  to  plants  the  elements  of  their  growth.  That  green 
healthy  vegetables  do  possess,  under  circumstances  to  be  mentioned  imme- 
diately, the  property  of  decomposing  carbon  dioxide  absorbed  by  their 
leaves  from  the  air,  or  conveyed  thither  in  solution  through  the  medium 
of  their  roots,  is  a  fact  positively  proved  by  direct  experiment,  and  ren- 
dered certain  by  considerations  of  a  very  stringent  kind.  To  effect  this 
very  remarkable  decomposition,  the  influence  of  light  is  indispensable;  the 
diffused  light  of  day  suffices  in  some  degree,  but  the  direct  rays  of  the  sun 
greatly  exalt  the  activity  of  the  process.  The  carbon  separated  in  this 
manner  is  retained  in  the  plant  in  union  with  the  elements  of  water,  with 
which  nitrogen  is  also  sometimes  associated,  while  the  oxygen  is  thrown 
off  into  the  air  from  the  leaves  in  a  pure  and  gaseous  condition. 

The  effect  of  ammoniacal  salts  upon  the  growth  of  plants  is  so  remark- 


826  DIGESTION   AND   NUTRITION. 

able  as  to  leave  little  room  for  doubt  concerning  the  peculiar  functions  of 
the  ammonia  discovered  in  the  air.  Plants  which  in  their  cultivated  state 
contain,  and  consequently  require,  a  larger  supply  of  nitrogen,  as  wheat, 
and  the  cereals  in  general,  are  found  to  be  greatly  benefited  by  the  appli- 
cation to  the  land  of  such  substances  as  putrefied  urine,  which  may  be 
looked  upon  as  a  solution  of  ammonium  carbonate,  or  of  guano,  which  is 
the  partially  decomposed  dung  of  birds,  found  in  immense  quantities  on 
some  of  the  barren  islets  of  the  western  coast  of  South  America,  as  that 
of  Peru.  More  recently,  similar  deposits  have  been  found  on  the  coast  of 
Southern  Africa.  The  guano  now  imported  into  England  from  these  locali- 
ties is  usually  a  soft,  brown  powder,  of  various  shades  of  color.  White 
specks  of  bone-earth,  and  sometimes  masses  of  saline  matter,  may  be  found 
in  it.  That  which  is  most  recent,  and  probably  most  valuable  as  manure, 
often  contains  undecomposed  uric  acid,  besides  much  ammonium  oxalate 
or  chloride,  alkaline  phosphates,  and  other  salts :  it  has  a  most  offensive 
odor.  The  specimens  taken  from  older  deposits  have  but  little  smell,  are 
darker  in  color,  contain  no  uric  acid,  and  much  less  ammoniacal  salt;  the 
chief  components  are  bone-earth,  a  peculiar  dark-colored  organic  matter, 
and  soluble  inorganic  salts.  (See  also  p.  724). 

Upon  the  members  of  the  vegetable  kingdom  thus  devolves  the  duty  of 
building  up,  as  it  were,  out  of  the  inorganic  constituents  of  the  atmos- 
phere,—  the  carbon  dioxide,  the  water,  and  the  ammonia, — the  numerous 
complicated  organic  principles  of  the  perfect  plant,  many  of  which  are 
afterwards  destined  to  become  the  food  of  animals,  and  of  man.  The  chem- 
istry of  vegetable  life  is  essentially  a  process  of  reduction  caused  by  the 
action  of  light,  but  the  mode  in  which  this  is  effected  is  at  present  by  no 
means  made  out.  One  thing,  however,  is  manifest,  namely,  the  wonderful 
relations  between  the  two  orders  of  organized  beings,  in  virtue  of  which 
the  rejected  and  refuse  matter  of  the  one  is  made  to  constitute  the  essen- 
tial and  indispensable  food  of  the  other.  While  the  animal  lives,  it  exhales 
incessantly  from  its  lungs,  and  often  from  its  skin,  carbon  dioxide ;  when 
it  dies,  the  soft  parts  of  the  body  undergo  a  series  of  chemical  changes  of 
degradation,  which  terminate  in  the  production  of  carbon  dioxide,  water, 
ammonium  carbonate,  and,  perhaps,  other  products  in  small  quantity. 
These  are  taken  up  by  a  fresh  generation  of  plants,  which  may  in  their 
turn  serve  for  food  to  another  race  of  animals. 


APPENDIX. 


HYDROMETER  TABLES. 


COMPARISON     OF     THE   DEGREES    OP    BAUME's     HYDROMETER    WITH     THE   REAL 
SPECIFIC    GRAVITIES. 

1.  For  Liquids  heavier  than  Water. 


Degrees. 

Specific 
Gravity. 

Degrees. 

Specific 
Gravity. 

Degrees. 

Specific 
Gravity. 

0 

1-000 

26 

1-206 

52 

1-520 

1 

1-007 

27 

1-216 

53 

1-535 

2 

1-013 

28 

1-225 

54 

1-551 

3 

1-020 

29 

1-235 

55 

1-567 

4 

1-027 

30 

1-245 

56 

1-583 

5 

1-034 

31 

1-256 

57 

1-600 

6 

1-041 

32 

1-267 

58 

1-617 

7 

1-048 

33 

1-277 

59 

1-634 

8 

1-056 

34 

1-288 

60 

1-652 

9 

1.063 

35 

1-299 

61 

1-670 

10 

1-070 

36 

1-310 

62 

1-689 

11 

1-078 

37 

1-321 

63 

1-708 

12 

1-085 

38 

1-333 

64 

1-727 

13 

i-094 

39 

1-345 

65 

1-747 

14 

1-101 

40 

1-357 

66 

1-767 

15 

1-109 

41 

1-369 

67 

•788 

16 

1-118 

42 

1-381 

68 

•809 

17 

1-126 

43 

1-395 

69 

•831 

18 

1-134 

44 

•407 

70 

•854 

19 

1-143 

45 

•420 

71 

•877 

20 

1-152 

46 

•434 

72 

•900 

21 

1-160 

47 

•448 

73 

•944 

22 

1-169 

48 

•462 

74 

•04(.» 

23 

1-178 

49 

•476 

75 

•974 

24 

1-188 

50 

1-490 

76 

2-000 

26 

1-197 

51 

1-495 

827 


828 


APPENDIX. 


2.  BaumPs  Hydrometer  for  Liquids  lighter  than  Water. 


Degrees. 

Specific 
Gravity. 

Degrees. 

Specific 
Gravity. 

Degrees. 

Specific 
Gravity. 

10 

1-000 

27 

0-896 

44 

0-811 

11 

0-993 

28 

0-890 

45 

0-807 

12 

0-986 

29 

0-885 

46 

0-802 

13 

0-980 

30 

0-880 

47 

0-798 

14 

0-973 

31 

0-874 

48 

0-794 

15 

0-967 

32 

0-869 

49 

0-789 

16 

0-960 

33 

0-864 

50 

0-785 

17 

0-954 

34 

0-859 

51 

0-781 

18 

0-948 

35 

0-854 

52 

0-777 

19 

0-942 

36 

0-849 

53 

0-773 

20 

0-936 

37 

0-844 

54 

0-768 

21 

0-930 

38 

0-839 

55 

0-764 

22 

0-924 

39 

0-834 

56 

0-760 

23 

0-918 

40 

0-830 

57 

0-757 

24 

0-913 

41 

0-825 

58 

0-753 

25 

0-907 

42 

0-820 

59 

0-749 

26 

0-901 

43 

0-816 

60 

0-745 

These  two  tables  are  on  the  authority  of  Francoeur ;  they  are  taken  from 
the  Handworterbuch  der  Chemie  of  Liebig,  Poggendorif,  and  Wohler.  Baum^'s 
hydrometer  is  very  commonly  used  on  the  Continent,  especially  for  liquids 
heavier  than  water.  For  lighter  liquids  the  hydrometer  of  Cartier  is  often 
employed  in  France.  Cartier's  degrees  differ  but  little  from  those  of  Bailing. 

In  the  United  Kingdom,  Twaddell's  hydrometer  is  a  good  deal  used  for 
dense  liquids.  This  instrument  is  so  graduated  that  the  real  specific  grav- 
ity can  be  deduced  by  an  extremely  simple  method  from  the  degree  of  the 
hydrometer;  namely,  by  multiplying  the  latter  by  5,  and  adding  1000;  the 
sum  is  the  specific  gravity,  water  being  1000.  Thus  10°  Twaddle  indicates 
a  specific  gravity  of  1050,  or  1-05;  90°  Twaddell,  1450,  or  1-45. 

In  the  Customs  and  Excise,  Sikes's  hydrometer  is  used. 


APPENDIX. 


829 


ABSTRACT 

OP  DR.  DALTON'S  TABLE  OP  THE  ELASTIC  FORCE  OF  TAPOUR  OF  WATER 
DIFFERENT  TEMPERATURES,  EXPRESSED  IN  INCHES  OF  MERCURY. 


Temperature. 

Force. 

Temperature. 

Force. 

Temperature. 

Force. 

Fah. 

Cent. 

Fah. 

Cent. 

Fah. 

Cent. 

32° 

o°-o 

0-200 

57° 

13o-88 

0-474 

90° 

32°-2 

1-36 

33 

C°-55 

0-207 

58 

140.4 

0-490 

95 

35° 

1-58 

34 

1°-1 

0-214 

59 

15° 

0-507 

100 

8.70.77 

1-86 

35 

l°-66 

0-221 

60 

15°-5 

0-524 

105 

40°  -5 

2-18 

36 

2°-2 

0-229 

61 

16°-1 

0-542 

110 

43°-3 

2-53 

37 

2°-77 

0-237 

62 

i6°-66 

0-560 

115 

46°-l 

2-92 

38 

3°-3 

0-245 

63 

17°-2 

0-578 

120 

48°-88 

3-33 

39 

3°-88 

0-254 

64 

170.77 

0^597 

125 

51°-66 

3-75 

40 

40.4 

0-263 

65 

18°-3 

0-616 

130 

54°-4 

4-34 

41 

5° 

0-273 

66 

18°-88 

0-635 

135 

57°-2 

5-00 

42 

5°  -55 

0-283 

67 

19°-4 

0-665 

140 

60° 

6-74 

43 

6°-l 

0-294 

68 

20° 

0-676 

145 

620.77 

6-53 

44 

6°-66 

0-305 

69 

20°  -55 

0-698 

150 

65°-5 

7-42 

45 

70.2 

0-316 

70 

21°-1 

0-721 

160 

71°-1 

9-46 

46 

70.77 

0-328 

71 

21°-66 

0-745 

170 

76°-66 

12-13 

47 

8°  -3 

0-339 

72 

22°  -2 

0-770 

180 

82°-2 

15-15 

48 

8°-88 

0-351 

73 

22°-77 

0-796 

190 

87°-77 

1900 

19 

90.4 

0-363 

74 

23°-3 

0-823 

200 

93o-3 

23-64 

50 

10° 

0-375 

75 

230-88 

0-851 

210 

98°  -88 

28-84 

51 

10°-55 

0-388 

76 

24°-4 

0-880 

212 

100° 

30-00 

52 

11°-1 

0401 

77 

25o 

0-910 

220 

1040.4 

34-99 

53 

llo-66 

0-415 

78 

25°-5 

0-940 

230 

110° 

41-75 

54 

12°-2 

0-429 

79 

26°-l 

0-971 

240 

115°-5 

49-67 

65 

12°-77 

0443 

80 

26°-66 

1-000 

250 

121°-1 

68-21 

56 

13°-3 

0-458 

85 

29°-44 

1-170 

300 

148°-88 

111-81 

70 


830 


APPENDIX. 


TABLE 

OF  THE  PBOPORTION  BY  WEIGHT  OF  ABSOLUTE  OR  REAL  ALCOHOL  IN  100  PARTS 
OF   SPIRITS    OF   DIFFERENT    SPECIFIC   GRAVITIES.       (FOWNES.) 


Sp.  Or.  at  60° 
(15°-5C). 

Per  cent, 
of  real 
Alcohol. 

Sp.  Or.  at  60° 
(15°-5C.) 

Per  cent, 
of  real 
Alcohol. 

Sp.  Or.  at  60° 
(15°-5C). 

Per  cent, 
of  real 
Alcohol. 

0-9991 

0-5 

0-9511 

34 

0-8769 

68 

0-9981 

1 

0-9490 

35 

0-8745 

69 

0-9965 

2 

0-9470 

36 

0-8721 

70 

0-9947 

3 

0-9452 

37 

0-8696 

71 

0-9930 

4 

0-9434 

38 

0-8672 

72 

0-9914 

5 

0-9416 

39 

0-8649 

73 

0-9898 

6 

0-9396 

40 

0-8625 

74 

0-9884 

7 

0-9376 

41 

0-8603 

75 

0-9869 

8 

0-9356 

42 

0-8581 

76 

0-9855 

9 

0-9335 

48 

0-8557 

77 

0-9841 

10 

0-9314 

44 

0-8533 

78 

0-9828 

11 

0-9292 

45 

0-8508 

79 

0-9815 

12 

0-9270 

46 

0-8483 

80 

0-9802 

13 

0-9249 

47 

0-8459 

81 

0-9789 

14 

0-9228 

48 

0-8434 

82 

0-9778 

15 

0-9206 

49 

0-8408 

83 

0-9766 

16 

0-9184 

50 

0-8382 

84 

0-9753 

17 

0-9160 

51 

0-8357 

85 

0-9741 

18 

0-9135 

52 

0-8331 

86 

0-9728 

19 

0-9113 

53 

0-8305 

87 

0-9716 

20 

0-9090 

54 

0-8279 

88 

0-9704 

21 

0-9069 

55 

0-8254 

89 

0-9691 

22 

09047 

56 

0-8228 

90 

0-9678 

23 

0-9025 

57 

0-8199 

91 

0-9665 

24 

0-9001 

58 

0-8172 

92 

0-9652 

25 

0-8979 

59 

0-8145 

93 

0-9638 

26 

0-8956 

60 

0-8118 

94 

0-9623 

27 

0-8932 

61 

0-8089 

95 

0-9609 

28 

0-8908 

62 

0-8061 

96 

0-9593 

29 

0-8886 

63 

0-8031 

97 

0-9578 

30 

0-8863 

64 

0-8001 

98 

0-9560 

31 

0-8840 

65 

0-7969 

99 

0-9544 

32 

0-8816 

66 

0-7938 

100 

0-9528 

33 

0-8793 

67 

APPENDIX. 


831 


TABLE 

OF  THE  PROPORTION  BY  VOLUME  OF  ABSOLUTE  OR  REAL  ALCOHOL  IN  100  VOL- 
UMES OF  SPIRITS  OF  DIFFERENT  SPECIFIC  GRAVITIES  (GAY-LUSSAC)  AT  59° 
F.  (15°  C.) 


100  vol.  Spirits. 

100  vol.  Spirits. 

100  vol.  Spirits. 

Spec.  Grav. 

Contain 
vol.  of 
real 
Alcohol. 

Spec.  Grav. 

Contain 
vol.  of 
real 
Alcohol 

Spec.  Grav. 

Contain 
vol.  of 
real 
Alcohol. 

1  0000 

0 

0-9608 

34 

0-8956 

68 

0-9985 

1 

0-9594 

35 

0-8932 

69 

0-9970 

2 

0-9581 

36 

0-8907 

70 

0-9956 

3 

0-9567 

37 

0-8882 

71 

09942 

4 

0-9553 

38 

0-8857 

72 

0-9929 

5 

0-9538 

39 

0-8831 

73 

0-9916 

6 

0-9523 

40 

0-8805 

74 

0-9903 

7 

0-9507 

41 

0-8779 

75 

0-9891 

8 

0-9191 

42 

0-8753 

76 

0-9878 

9 

0-9474 

43 

0-8726 

77 

0-9867 

10 

0-9457 

44 

0-8699 

78 

0-9855 

11 

0-9440 

45 

0-8672 

79 

0-9844 

12 

0-9422 

46 

0-8645 

80 

0-9833 

13 

0-9404 

47 

0-8617 

81 

0-9822 

14 

0-9386 

48 

0-8589 

82 

0-9812 

15 

0-9367 

49 

0-8560 

83 

09802 

16 

0-0348 

50 

0-8531 

84 

0  9792 

17 

0-9329 

51 

0-8502 

85 

0-9782 

18 

0-9309 

52 

0-8472 

86 

0-9773 

19 

0-9289 

53 

0-8442 

87 

09763 

20 

0-9269 

54 

0-8411 

88 

0-9753 

21 

0-9248 

55 

0-8379 

89 

0-9742 

22 

0-9227 

56 

0-8346 

90 

0-9732 

23 

0-9206 

57 

0-8312 

91 

0-9721 

24 

0-9185 

58 

08278 

92 

0-9711 

25 

0-9163 

59 

08242 

93 

0-9700 

26 

0-9141 

60 

0-8206 

94 

0-9690 

27 

0-9119 

61 

0-8168 

95 

0-9679 

28 

0-9096 

62 

0-8128 

96 

0-9668 

29 

09073 

63 

0-8086 

97 

0-9657 

30 

0-9050 

64 

0-8042 

98 

0-9645 

31 

0-9027 

65 

0-8006 

99 

0-9633 

32 

0-9004 

66 

0-7947 

100 

0-9621 

33 

0-8980 

67 

ANALYSES  OF 


Source,    .     . 
Name  of  Spring,    . 

Vichy, 
France. 

Puits 
Carre. 

Ems, 
Nassau. 

Keasel- 
brunnen. 

Sellers, 
Nassau. 

Karla- 
brunnen, 
Silesia, 

Karlsbad, 
Bohemia. 

Sprudel. 

Calcium          .... 
Barium       .... 
Strontium      .... 
Magnesium 
Sodium           .... 
Potassium 

117-1 

"i-7 

64-2 
1814-0 
162-7 

594 
0-3 
0-6 
29-3 
1122-9 
34-7 

113-9 
0-1 
1-4 
51-2 
1232-9 
47-8 
trace 

241-8 

'7-4 

125-0 

"6-5 
50-3 
1793-0 

Aluminium 
Iron       
Manganese          .         .         . 
Chlorine         .... 
Bromine     .... 

"2  -a 

trace 
324-8 

trace 
1-6 
0-2 

487-0 

trace 
trace 
trace 

1388-5 

31-9 
14-1 

trace 
1-7 
0-4 
630-2 

Iodine  
Fluorine     .... 
Carbonic  acid  (C03) 
Sulphuric  acid  (SO4) 
Nitric  acid  (NO,) 

2415-0 

196-8 

"6-1 

952-0 
38-7 

"i-5 

7538 
28-4 

378-8 
39-6 

'l-5 
1028-5 
1749-1 
0-4 

Phosphoric  acid  (P04) 
Arsenic  acid  (As04) 
Silicic  acid  (SiO,) 
Sulphur          .... 

16-7 
1-0 

68-0 

539 

0-4 
39-2 

72-1 

0-4 
75-1 

Organic  Matter 

Total  solid  constituents  in  1 
1,000,000  parts   .         .      / 

Gaseous    Constituents  —  in  "1 
cubic     centimetres     per  1 
litre    at   0°  C.    and    760  [ 
mm.  bar.  : 
Carbon  dioxide 
Nitrogen 
Ether      .... 

5184-0 
445 

2780-7 

93 
0-4 

3659-1 
1087 

785-7 
406 

5456-1 
1100 

Hydrogen  sulphide      . 

Temperature  (Cent.)      . 
Specific  gravity 

Analysts         ...           J 

43-75° 

Bou- 
quet 

46° 
1-0034 

15° 

8° 

Meiss- 
ner 

74° 

1-00497 

Berze- 
lius 

832 


MINERAL  WATERS. 


Piillna, 
Bohemia. 

Seidschlitz 
Bohemia. 

Seidlitz, 
Bohemia. 

Bath. 

Chelten- 
ham. 

Harrow- 
gate- 

Wheat 
Clifford, 
Cornwall. 

Saratoga. 

Chief 
Spring. 

Chief 
Spring. 

King's 
Bath. 

Royal 
WeU. 

Old  Sul- 
phur Well. 

Congress. 

139-6 

385-8 

722-9 

386-7 

179-5 

493-6 

1163-6 

405-5 

*" 

•  •* 

*** 

... 

*"* 

*•• 

"*6-6 

3319-0 

2813-7 

2918-5 

"53-9 

"  8-1 

198-7 

"31-9 

209-3 

5222-0 

1974-0 

... 

160-0 

2701-4 

4940-4 

20422 

2134-4 

344-0 

239-6 

... 

29-8 

... 

479-7 

111.2 

1607 

... 

... 

... 

... 

... 

... 

61-3 

... 

... 

... 

... 

... 

) 

•6 

... 

)andC03r 

... 

7-4 

4-1 

f 

traces 

1-4 

... 

C    24-9J 

... 

... 

... 

...  j 

1-7 

1913-3 

211-1 

292-0 

265-3 

2066-7 

9187-4 

5632-5 

1505-6 

... 

trace 

... 

... 

23-2 

... 

... 

6-3 

... 

4-3 

... 

... 

... 

... 

•2 

... 

463-7 

904-0 

"86-9 

639-5 

104-8 

... 

'... 

656-2 

14273-4 

11568-6 

1029-5 

2259-1 

18-2 

i'23-8 

13132 

21154-0 

2746-0 

... 

... 

... 

... 

... 

12-2 

... 

... 

... 

... 

2-6 

... 

... 

... 

0-3 

... 

... 

... 

... 

... 

... 

22-9 

4-7 

... 

42-6 

14-6 

*3-4 

66-0 

19-2 

... 

... 

... 

... 

87-7 

... 

... 

... 

... 

... 

... 

240-7 

... 

... 

... 

32771-3 

23141-2 

16406-0 

2062-1 

8139-4 

15513-9 

9232-5 

5777-9 

69 

200 

91-6 

125 

80-3 

69-5 

... 

... 

... 

... 

10-6 

... 

... 

... 

21-3 

... 

... 

... 

... 

19-6 

... 

... 

14° 

9° 

52° 

10- 

1-0064 

1-01113 

1-007 

... 

Struve 

Berze- 
lius 

Nau- 
mann 

Merck 
and  Gal- 
loway 

Abel 
and 
Rowney 

Hof- 
mann 

Miller 

Schwei- 
tzer 

833 


ANALYSES 

FRESH  SPRING  AND 


Source,    .    .    . 

Spring  at 
Whitley, 
Surrey. 

Spring 
at 
Watford, 
Herts. 

Artesian 
Well, 
Trafalgar 
Square. 

Artesian 
Well, 

Guy's 
Hospital. 

Artesian 
Well, 
Crenelle, 
Paris. 

Calcium 

8-1 

110-1 

18-8 

15-0 

27-2 

Magnesium 

1-8 

... 

9-1 

9-8 

4-0 

Sodium 

6-4 

11-0 

265-3 

237-3 

... 

Potassium 

2-3 

... 

99-0 

7-8 

23-8 

Iron      .... 

... 

... 

Alumina  and    Ferric  "» 

oxide      .         .           j 

... 

... 

... 

... 

Chlorine 

12-8 

12-1 

174-2 

139-3 

5-2 

Carbonic  acid  (C03) 

trace. 

156-0 

197-1 

134-4 

60-5 

Sulphuric  acid  (SOJ     . 

13-3 

6-8 

1805 

158-4 

6-6 

Nitric  acid  (N03) 

... 

19-0 

... 

... 

Phosphoric  acid    (P04) 

... 

... 

... 

07 

... 

Silicic  acid  (Si03) 

12-3 

ii'-6 

13-1 

11  3 

6-0 

Organic  matter 

16-0 

11-6 

13-0 

13-4 

20 

Total  solid  constitu-  ") 

ent  in    1,000,000  I 

73-0 

338-2 

970-1 

727-4 

135-3 

parts.      .         .       J 

Gaseous  constituents, 

cub.  cent,  per  litre: 

Carbon  dioxide     . 

trace. 

304 

0-7 

15 

Oxygen 

... 

3-4 

3-6 

Nitrogen 

... 

... 

20-5 

13-0 

Temperature 

14-5° 

15-5° 

28° 

Specific  gravity     . 

1-00095 

1-00077 

Hardness  . 

2-8° 

... 

8° 

... 

r 

Graham, 

Analysis        .         .       J 

Miller, 
and 
Hof- 

Camp- 
bell 

Abel 
and 
Rowney 

Odling 

Payen 

I 

mann 

834 


OF 

RIVER  WATER, 


St.  Wini- 

fred's Holy 
Well, 

North 

Thames,  at 
Twicken- 
ham. 

Thames,  at 
Lambeth 

Rhone, 
near 
Geneva. 

Rhine, 
at 

Basle. 

Ulls- 
Wiiter 
Lake. 

Loch 
Katrine. 

Walt*. 

115-9 

83-8 

69-4 

45-3 

65-5 

8-3 

1-9 

11-0 

4-7 

6-0 

2-7 

4-8 

1-8 

0-8 

13-6 

9-2 

11-1 

3-1 

06 

5-4 

... 

trace 

4-2 

6-1 

... 

... 

... 

... 

trace 

... 

3-9 

... 

... 

... 

trace 

12-1 

... 

... 

1  4 

35-7 

14-2 

16-8 

1-0 

1  5 

99 

4-7 

156-3 

119-9 

91-7 

50-8 

86-2 

20-4 

1-7 

52-5 

31-4 

37-6 

429 

15-4 

6-4 

5-6 

... 

... 

... 

8-5 

... 

... 

... 

... 

... 

... 

... 

trace 

39-1 

"3-9 

149 

23-8 

2-1 

3-0 

01 

... 

49-7 

37-0 

... 

3-3 

5-0 

11-4 

4L<-1 

321-0 

302-7 

1820 

169-4 

60-2 

27-6 

V 

.  81-8 

5-1 

63-2 

8-4 

1-8 

0-3 

... 

... 

... 

8-0 

7-5 

9-3 

... 

... 

... 

18-4 

.... 

15-5 

18-4 

11° 

9-5° 

1-001 

1-0003 

... 

... 

... 

... 

...  5 

... 

20-2 

... 

... 

1-9 

... 

Graham, 

Barrat 

Clark 

Miller, 
and 

Deville 

Pagen- 
stecher 

Way 

Wallace 

Hofmann 

835 


836  APPENDIX. 


WEIGHTS   AND    MEASURES. 


480-0  grains  Troy  =  1  oz.  Troy. 

437-5  "  =  1  oz.  Avoirdupoids. 

7000-0  "  =  1  Ib.  Avoirdupoids. 

5760-0  «  =1  Ib.  Troy. 


Ibe  imperial  gallon  contains  of  water  at  60°  (15° -50)  70,000-    grains. 

The  pint  (£  of  gallon) 8,750- 

The  fluid-ounce  (^  of  pint) 437-5      " 

The  pint  equals  34-66  cubic  inches. 


The  Fren:h  kilogramme  =  15,433-6  grains,  or  2-679  Ib.  Troy, or 

2-205  Ib.  avoirdupoids. 

The  grammme       =  15-4336  grains. 

"    decigramme    =    1-5434       " 

"    centigramme  =    0-1543       " 

"•    milligramme  =    0-0154       " 


The  metre  of  France  =  39-37      inches. 
"    decimetre  =    3-937         " 

"    centimetre  =    0-394         «< 

"     millimetre  =    00394        " 


APPENDIX. 


837 


h  Miles 
yards. 


I" 


CO  7"!  CD  t£>  *O  O  O  O 

CO  CO  ^H  CD  O  O  O  O 

kO  -<f  CD  CO  f«  CO  >O  *O 

§O  -tf  CO  CO  ^H  CO  O 
O  O  Tf  CO  CO  ^H  CO 

ooooo^cbcb 

iO 


3* 

I" 

w 


CO  CO  CO  CO 

§CO  O  CO  CO  «-H 

O5  CO  CO  CO  CO  ^-  O 

r-i  O  C5  CO  CD  CO  CO  i— > 

OOr- lOOSCpCpCO 

OOOrHOCTlCOCO 
i-.  O  05  CO 

1-1  ^i  o 


H 


II 

w  a 


§co  c-i  co  o  co  O5 
p  cp  <M  co  o  co 

O  O  O  CO  C-1  CO  O 

CO  <M  CO 

CO  (M 


t~—  i— t  CO  Oi  O  O  O 
co  r^  o  i^  C5  O  o 
Oi  CO  l^  O  I-  Oi  O 
CO  Ci  CO  I-  O  I—  Ol 
O  CO  Oi  CO  l~  O  l^ 


H 


sh  Pol 
Sq.  Fe 


«s 


Si 


. 


CO 
CO 

O  CO  O 

g 


103 
632 
33260 


96 


CO  <M  CO 
O  TP  CO 

05  CO  <-H 
<M  O5  rt< 

•*  OS  CO 
CO  CM  O5 

6  «b  CM 


S  g 


66 


£ 

II 


time 
met 


Si 

II 


«=d> 

till 

11 

££ 

g§ 


838 


APPENDIX. 


n  Bushels 
ons  =  221 
Cubic  In 


In  Gallons  = 
Pints  =  277-27 
Cubic  Inches. 


o  i^  b-  oo  b-  t—  o  o 

r-t  ai  CD  co  i-  co  i^  >o 

O 


t-i  t-  co  o  r-  i—  co  r* 

O  ^-i  l^  CO  O  l^  t^  CO 

O 


i-l  CO  LC  00  O  1^ 

COr-iCOtOOOO 

o  cc  i—  <  CD  tra  co 

CO  O  CO  i—  i  CO  lO 
O  CO  tO  CO  r-f  CO 
O  O  CO  lO  CO  T-H 


(M  l^  O  tO  i— i  iO  1-1  CS 
O  <M  t^-  O  iO  i— i  O  i— ( 
r-i  O  <M  t^  O  O  i—  iO 

«0   ~   O   (M   t-  O   'O    ri 
rH  O  C>1  1^  O  O 


Z,  •+->  -M 

S  S  O  o 

•-j  D  o>  »H 

•S  o  o  -e 


ii 


1 1 


' 


n  Cwts.  =  112  LbB. 
=  784,000  Grains. 


1 

EH  ^ 


Is 


(MOtOCOfNr-icOCO 
(M  <M  O  •<*  CD  CM  I-H  (M 
O  CM  (M  O  Tt<  CD  (M  r-i 

OOOCNCNOrfico 
O  O  O  O  O  O1  <M  O 


(M  <M  iO  r-t  l-~  CO 

CO  01  1-1  tO    ~ 

§CO  (M 
O 
(^  
O  O  O  CO  CSI  r* 

OOobocbcNT-! 


T-H    ^  C       ^ 

1  1C  O  t^  <M  CO 
1-1  tO  O  l^  C-l 
(M  T-I  iO  O  i^ 


lOrtHCOCNJCO-^OOOO 
r-t  IO  Tt<  00  <M  CO  -^  00 


•§» 


2  S  «  S 


APPENDIX. 


839 


TABLE 

FOR     CONVERTING     DEGREES     OF    THE     CENTIGRADE     THERMOMETER    INTO 
DEGREES    OF    FAHRENHEIT'S    SCALE. 


Cent. 

Fah. 

Cent. 

Fah. 

Cent. 

Fah. 

—100° 

...  —148-0° 

—55° 

...  _  67-0° 

—10° 

...   -f-14-00 

99 

146-2 

54 

65-2 

9 

15-8 

98 

144-4 

53 

63-4 

8 

17-6 

97 

142-6 

52 

61-6 

7 

19-4 

96 

140-8 

51 

59-8 

6 

21-2 

95 

139-0 

50 

58-0 

5 

23-0 

94 

137-2 

49 

56-2 

4 

24-8 

93 

135-4 

48 

54-4 

3 

26-6 

92 

133-6 

47 

52-6 

2 

28-4 

91 

131-8 

46 

50-8 

1 

30-2 

90 

1300 

45 

49-9 

0 

32-0 

89 

128-2 

44 

47-2 

+1 

83-8 

88 

126-4 

43 

45-4 

2 

35-6 

87 

124-6 

42 

43-6 

3 

37-4 

86 

122-8 

41 

41-8 

4 

39-2 

85 

121-0 

40 

40-0 

5 

41-0 

84 

1192 

39 

38-2 

6 

42-8 

83 

117-4 

38 

36-4 

7 

44-6 

82 

115-6 

37 

34-6 

8 

46-4 

81 

113-8 

36 

32-8 

9 

48-2 

80 

1120 

35 

31-0 

10 

50-0 

79 

110-2 

34 

29-2 

11 

51-8 

78 

1084 

33 

27-4 

12 

53-6 

77 

...  .   106-6 

32 

25-6 

13 

55-4 

76 

104-8 

31 

23-8 

14 

57-2 

75 

103-0 

30 

22-0 

15 

59-0 

74 

101-2 

29 

20-2 

16 

60-8 

73 

99-4 

28 

18-4 

17 

62-6 

72 

97-6 

27 

16-6 

18 

64-4 

71 

95-8 

26 

14-8 

19 

66-2 

70 

94-0 

25 

13-0 

20 

68-0 

69 

92-2 

24 

11-2 

21 

69-8 

68 

90-4 

23 

9-4 

22 

71-6 

67 

88-6 

22 

7-6 

23 

73-4 

66 

86-8 

21 

5'8 

24 

75-2 

65 

85-0 

20 

4-0 

25 

77-0 

64 

83-2 

19 

2-2 

26 

78-8 

63 

81-4 

18 

0-4 

27 

80-6 

62 

79-6 

17 

...    +1-4 

28 

82-4 

61 

77'8 

16 

3-2 

29 

84-2 

60 

76-0 

15 

5-0 

30 

86-0 

59. 

74-2 

14 

6-8 

31 

87-8 

58 

72-4 

13 

8-6 

82 

89-6 

57 

70-6 

12 

10'4 

83 

91-4 

56 

68-8 

11 

12-2 

34 

93-2 

840  APPENDIX. 

TABLE  or  THERMOMETER  SCALES  (continued'). 


I 


Cent. 

Fah. 

Cent. 

Fah. 

Cent. 

Fah. 

+35° 

+95-0° 

+85° 

+185-0° 

4-135° 

...  +275-0° 

36 

96-8 

86 

186-8 

136 

276-8 

37 

98-6 

87 

188-6 

137 

278-6 

38 

100-4 

88 

190-4 

138 

280-2 

39 

102-2 

89 

192-2 

139 

282-2 

40 

104-0 

90 

194-0 

140 

284-0 

41 

105-8 

91 

195  8 

141 

285-8 

42 

107-6 

92 

197-6 

142 

287-6 

43 

109-4 

93 

199-4 

143 

289-4 

44 

111-2 

94 

201-2 

144 

291-2 

45 

113-0 

95 

203-0 

145 

293-0 

46 

114-8 

96 

204-8 

146 

294-8 

47 

116-6 

97 

206-6 

147 

296-6 

48 

118-4 

98 

208-4 

148 

298-4 

49 

120-2 

99 

210-2 

149 

300-2 

50 

122-0 

100 

212-0 

150 

302-0 

51 

123-8 

101 

213-8 

151 

303-8 

52 

125-6 

102 

215-6 

152 

3056 

53 

127-4 

103 

217-4 

153 

307-4 

54 

129-2 

104 

219-2 

154 

3092 

55 

131-0 

105 

221-0 

155 

311-0 

56 

132-8 

106 

222-8 

156 

312-8 

57 

134-6 

107 

224-6 

157 

314-6 

58 

136-4 

108 

226-4 

158 

316-4 

59 

138-2 

109 

228-2 

159 

318-2 

60 

140-0 

110 

230-0 

160 

320-0 

61 

141-8 

111 

231-8 

161 

321-8 

62 

143-6 

112 

233-6 

162 

323-6 

63 

145-4 

113 

235-4 

163 

325-4 

64 

147-2 

114 

237-2 

164 

327-2 

65 

149-0 

115 

239-0 

165 

329-0 

66 

150-8 

116 

240-8 

166 

330-8 

67 

152-6 

117 

242-6 

167 

332-6 

68 

154-4 

118 

244-4 

168 

334-4 

69 

156-2 

119 

246-2 

169 

336-2 

70 

158-0 

120 

248-0 

170 

338-0 

71 

159-8 

121 

249-8 

171 

339-8 

72 

161-6 

122 

251-6 

172 

341-6 

73 

163-4 

123 

253-4 

173 

343-4 

74 

165-2 

124 

255-2 

174 

345-2 

75 

167-0 

125 

257-0 

175 

347-0 

76 

168  8 

126 

258-8 

176 

348-8 

77 

170-6 

127 

260-6 

177 

350  6 

78 

172-4 

128 

2624 

178 

352-4 

79 

174-2 

129 

264-2 

179 

354-2 

80 

176-0 

130 

266-0 

180 

356-0 

81 

177-8 

131 

267-8 

181 

357-8 

82 

179-6 

132 

269-6 

182 

359-6 

83 

181-4 

133 

271-4 

183 

361-4 

84 

1832 

134 

273-2 

184 

363-2 

APPENDIX. 
TABLE  OF  THERMOMETER  SCALES  (continued). 


841 


Cent. 

Fah. 

Cent. 

Fuh. 

Cent. 

Fah. 

-j-1850 

...  +365-0° 

-(-230° 

...  +446-0° 

+275° 

...  +527-0° 

186 

366-8 

231 

447-8 

276 

528-8 

187 

368-6 

232 

449-6 

277 

530-6 

188 

370-4 

233 

451-4 

278 

532-4 

189 

372-2 

234 

453-2 

279 

534-2 

190 

374-0 

235 

455-0 

280 

536-0 

191 

375-8 

236 

456-8 

281 

537-8 

192 

377-6 

237 

458-6 

282 

539-6 

193 

379-4 

238 

460-4 

283 

5414 

194 

381-2 

239 

4(52-2 

284 

543-2 

195 

383-0 

240 

404-0 

285 

545-0 

19G 

384-8 

241 

465-8 

286 

546-8 

197 

386-6 

242 

467-6 

287 

548-6 

198 

388-4 

243 

469-4 

288 

550-4 

199 

390-1 

244 

471-2 

289 

552-2 

200 

392-0 

245 

473-0 

290 

5540 

201 

393-8 

246 

474-8 

291 

555-8 

202 

395-6 

247 

476-6 

292 

557-6 

203 

397-4 

248 

478-4 

293 

559-4 

204 

399-2 

249 

480-2 

294 

561-2 

205 

401-0 

250 

482-0 

295 

563-0 

206 

402-8 

251 

483-8 

296 

564-8 

207 

404-6 

252 

485-6 

297 

566-6 

208 

406-4 

253 

487-4 

298 

568-4 

209 

408-2 

254 

489-2 

299 

570-2 

210 

410-0 

255 

491-0 

300 

572-0 

211 

411-8 

256 

492-8 

301 

573-8 

212 

413-6 

257 

494-6 

302 

575-6 

213 

415-4 

258 

496-4 

303 

577-4 

214 

417-2 

259 

498-2 

304 

579-2 

215 

419-0 

260 

5000 

305 

581-0 

216 

420-8 

261 

501-8 

306 

582-8 

217 

422-6 

262 

503-6 

307 

584-6 

218 

424-0 

263 

505-4 

308 

6864 

219 

426-2 

264 

607-2 

309 

588-2 

220 

4280 

265 

509-0 

310 

590-0 

221 

429-8 

266 

5108 

311 

5918 

222 

431-6 

267 

512-6 

312 

693-6 

223 

433-4 

268 

514-4 

313 

595-4 

224 

43-V2 

269 

516-2 

314 

5972 

225 

437-0 

270 

518-0 

315 

599  0 

226 

438-8 

271 

519-8 

316 

600-8 

227 

440-6 

272 

521-6 

317 

602-6 

228 

442-4 

273 

523-4 

318 

604.4 

229 

444-2 

274 

525-2 

319 

600-2 

71 


INDEX. 


PAGE 

Absorption  of  gases.  ...139,  150 
of  heat                        101  106 

Acid: 
bromo-benzoic  

PAGE 
636 

Aeid  :                                   p 
dextroracemic,     or 

AGE 

C74 
731 
775 
013 
731 
612 
019 
52S 
644 
613 
047 
731 

r,ir> 

03fi 

nsa 

f.SS 
f,82 
6S.T 

r.77 

109 
f>29 
67.°. 
f',70 

r.29 

7S5 
r.s:j 

S62 

f.lti 
770 
fi.'50 
r,C)l 
fi2S 
Wfi 
(170 
6C.5 
60S 
7  Si) 
787 
804 
,199 
004 
Of,4 
714 
71ti 
603 
OL'S 
070 
072 
(U',7 
SI  -2 
si:5 
774 
f,44 
COO 
073 
(-,.",7 
5S5 

7  ^ 

IS'.t 

032 

bromo-phenisic  
bromo-propionic  

552 
615 

Acetal        687 

Acctamide                   772 

616 

diamido-benzoic  636, 
dibromacetic  

Acetates    metallic               607 

765 

Acetic  acid,  manufacture 
of             607 

632 

campholic  

631 

dichloracetic  
diethylacetic  
diethjlphosphoric  
diglycollic 

ethers                                 610 

664 

620 

Acetone           698 

caproic  

619 

determination  of  vapor- 
density  of.  4-59 

620 

di-iodacetic 

carballylic  

670 

dilactic 

Acetonitrile  710 

carbamic 

..314,  776 
552 
654 

dilituric 

Acetosalipyl  694 
Acetyl  chloride  611 

carbazotic  
carbocresylic  

dimethylacetic  

Acetylene  485 

carbolic 

550 

disulphetholic  
disulphobenzolic  
disulphometholic  597, 
disnlphoiiaphtholic  
ditartaric 

Acid  acetic                            606 

carbonic  
liquefaction  of..... 

.166,  648 
...66,  167 
AfiK 

acetamidobenzoic  637 

acetonic                               699 

aconitic  670 

carbohydroquinonic  668 
carminic  787 
cerotic    625 

acrylic  627 
adipic  662 

dithionic  
cla'idic  

alizaric  665 

all'inturic                            7°5 

chelidonic  

.  .       690 

612 

allituric               .    ...         727 

chlorhydric  

181 

alloxanic  728 
alpha-orsellic  7S6 

chloric  
chlorobenzoic  

186 
626 

erythric......  670, 
ethionic  518, 
ethene-diglycollic  ...  
etliylacetic  

alpha-toluic        .     ..      .    639 

440 

alphaxylic                           639 

184 

chloronitrous  

184 

amidacetic  614 
amido-benzoic  636,  775 
.    amido-butyric  617 

chlorophenesic  

552 
552 

chloropropionic  .... 

615 

ethylpliosphoric  
ethylsulphnric  

804 

amido-propionic  615 
amylacetic           ...             b'20 

chlorous  

185 

618 

anchoic                               663 

cholic 

812,  813 

812 

anilic                 .        ...  784 

439 

evernic             .     .    .  665 

anisic                                    654 

789 

anthranilic  776,784 
antimonic                            419 

chrysanilic  

784 

.  789 

ferric  

arachidic                            625 

chrysophanic  

787 
628 

fill  niin  ic  

440 

fulniiimric  

664 

atropic  641 
auric                  370 

citric  

678 
408 

pudic 

liarbitviric                         .  7-51 

.     ..  679 

frallotannic  ...       .     580 

benic  or  bohonic  625 
bcnz'imidacetic                  638 

convolvulinoleic  .... 

652 
655 

I)(>ii7ilic          050 

654 

|lC||/uic                                                      Ifc'.o 

678 

ben/oglycollic                    638 

827 

#1  vcollir                        614 

bfta-orscllii-    786 

440 

lijmniithic           428 

712 

boric                                     "OS 

7i;j 

brassic     629 

440 

hiimic             

bromaretic  613 

(;27 

IiV<I;mtoi<' 

bromio                                 1S8 

627 

bromo-barbituric  731 

660 

843 

INDEX. 


Acid: 
liydrubromic  
hydrochloric  

PAGE 

188 

Acid: 

PAOE 

621 

Acid  :                                     PAOE 
quadrichlorovaleric  618 
quinic  680 

niyronic  

580 

hydrocyanic  
hydroferricyania. 
liydroferi-ocyanic.  . 
hydrofluoric     

,...  701 
709 
708 
192 

naphthalic  

.  6t'5 
434 
158 

quinonic   665 
quinoylic  665 

C95 

artificial  production  of  677 
rhodizonic  078 

't  -''i'11,81 

636 

hydroflnosilicic  

hydroselenic  
hydrosulphocyanii 

205 
718 

nitrocumic  

440 
552 

ricinoleic             .                652 

roccellic  :  663 
rubiacic  788 

It       1  ' 

552 

nitrophenisic  

553 
665 

ruble    673 

hydrotcllurie    

rutic  620 

814 

nitrutoluic  

439 

saccharic  681 
salicylic  550,  653 

,  161 

698 

6-20 

salieylous  692 

hypogaaic  

667 

cenanthylic  

619 

sarcolactic     644 
scbacic  or  sebic  663 
selenhydric  205 

hypophosphorous  . 
hyponilpbmic  
hyposulphurous.... 

213 
,.  199 
199 

756 

oleic  

628 

673 

orsellinic  
orthophosphoric  ... 

.665,  786 
285 
.  388 

selenic                                  205 

selenious  204 

784 

silicic   210 

insolinic   
inosinic  

..439,  66(5 
..759,  804 
613 

388 

sorbic                                   632 

oxalic  

'  72.) 

stannic           391 

ste'iric                        .         623 

iodic       

190 

oxamic  

659,  777 
653 

styphuic  788 
suberic                    662 

783 

..527,  683 
616 

.557,  642 

eucciuic  662 

ist.tiiionic  

789 

sudoric          811 

on  ty  lie  

618 

668 

sulphacetic                 .    .    682 

itaconic     
jalapinoleic  

664 
G52 
673 

oxysiilphocarbamic 

777 
621 

729 

fiulph-hydric                 ..    200 

J£;I)01UC  

6^0 

645 

652 

sulphiudigotic  782 

lactamic  

lactic 

775 
644 

sulphindylic  782 

paraphosphoric  

286 

sulphobenzoic  683 
sulphobenzolic  683 
sulphocacodylic  766 
sulphocarbainic  777 
Bulphocarbonic  203 

.  ...  727 

parasorbic  

632 

677 

lauric     

621 
935 

parellic  

786 

.  .  663 

poetic  

088 
620 

775 

648 

pentathionic  

200 
186 

lo  vo-raccmic,  or  lev 
taric 

o-tar- 
.674,  677 
7°3 

440 

Bulphomethylic  514 

sulphonaphthalic  683 

lithic 

periodic  
permanganic  
phony  Icarbamic  ... 
phloretic  
phosphoric.  

194 
413 
776 
655 

214    2S-5 

lithofellic 

814 

778 

663 

malic  

6C8 

malonic  

661 

,214 

tannic        671 

...  .     413 

285 

tint'ilic                                633 

681 

^85 

623 

286 

meconic  

679 

214 

tartralic                          .  676 

melissic  

626 

52S 

6:15 

phthalic    

OG5 

mesaconic  

664 
..726,  729 
671 

tauro-cholie                    .     812 

mesoxalic  
metagallic  

picric  

553 

tauro-hyocholic  814 
tellurhydric         207 

pimaric  .... 

7% 

metantimonic  

420 

telluric                                 207 

metapectic  
metaphosphoric  ... 

nu'tastannic 

588 
2S5 

392 

pinic  

790 

668 

terephthalic               666 

propionic     
protocatechnic  
prussic  .. 

614 
668 

701 

tetrachlorovaleric  618 

tetnthionic                         199 

methacrylic    

....  630 

methiouic  682 
methylcarbamic   „  776 
methylcrotonic  630 
niothylparoxybenzoic...   654 
methylsulphuric  514 
molybdlc  44.4 

thi'icetic             613 

730 

purpuric  .... 

732 

thiosulphuric  199 

purroic  .... 

789 

thymotic             655 

pyrocomenic  

679 

thymyl-carbonic  655 

titanic                                  393 

570   671 

niunobromacetic   . 
nionachloracetic... 

613 
612 

pyromeconic    . 

670 

68'' 

iuorin"ic  

6'>g 

pyrophosphoric  ..„ 

pyrotartaric  

286 
661 

trichlorovaleric  618 
trithi6nic  199 

mucic  

681 

muriatic  
Jiiycoinolic  

181 
729 

pyroterobic  
pyruvic  

6-J7 
...  651 

tungstic  442 
ulmic  ...                   585 

INDEX. 


845 


Arid  :                                   PAGE 
lira  tni  lie                                730 

Alcohol:                              PACE 
i|iiarlvlic  532 

Aluminium:                        PAGE 
fluoride  334 

uric                             7'>3    MO 

hydrates  334 

quintylic         53(3 

methide                               76(> 

IIMIIV  7V[ 

sexdecylic  542 

oxide  334 

silicates.                               337 

vanadic                                 430 

xvlylic          549 

sulphate                               335 

violuric  731 

Alcohol  bases  470 

Aluminium    salts     reac- 

xanthic   *.       651 

Alcuholic  ammonias  470 

tions  of  337 

xylic         *                        <'>:;<) 

Alcoholic  oxides  469 

Alum  .stone                           336 

\ri.ls                                       133 

Alcohol  radicals      4(W 

ju-rvlic    626 

Alcohols,  generally  4tJ8 

Amalgams     .        .                 1563 

•iinic                            314    471 

aromatic  548 

A  marine.    .     .               690   750 

•ironi'itic                             633 

primary  secondary,  and 

Amber                                 '  790 

tertiary                 511 

Amic  acids            314    47''   775 

basicity  of.  282,  595 
fitly                                    597 

and  ethers,  diatomic  5.^5 

Amides  314,  472,  772 
Amidin                                   590 

iso-icrylic  .                .    .      6'29 

monatomic  510 

Amidogen  314 

diatomic  and    mono- 
basic                             642 

tetratoinic  571 

Amines  470,  732 

Aldebvde,  acetic  681 

natiiinic  alcohols  733 

nionatomic             .  .       640 

Anunelide.  .  .          .              721 

pentatomic                     (iso 

tions  of        .               6S7 

acrylic                               689 

triatoinic  and  bibasic  60S 

anisic             695 

hen/oic                                  C90 

basic    666 

cinnamic  691 

copper-compounds  ...   .  356 

triatoniic  and  tribasic  669 

cumic                 691 

Aconitates                             670 

formic                                  ('88 

Acrolcin     6S») 

salicylic         692 

turpethum  363 

Aconitiiie          .  .                   7*>0 

Actinism                                    96 

toluic                         .         6(.;0 

FM-uietin  579 

Aldehyde-ammonia  (87 

phosphate  349   810 

Aesculiu             .                     579 

Affinity  chemical                 239 

\ldehvdes                       470    6£3 

acetate                                  608 

relations  of  heat  to  241 

from    monatomic    alco- 

alum         336 

disposilV                                      *?40 

hols  .                                684 

carbonates                          312 

Air-pump  37 

aromatic  690 

chloride  312 

Alembroth   sal-                      359 

cyanate      .                         713 

Alanine                          615    751 

Albite    337 

Ali/arin   788 

Allminin                                 70.3 

Alkalies                          271    2tJO 

nitrate                               312 

test  for                                 80"' 

oxalate                                 659 

vegetable  S"l 

ganic  bodies  464 

phosphates                 .    .    313 

'All'iiminatc                             794 

Alkalimeter                            M';"i 

AllniiiiiiniUR  principles....  793 

Alkaliuietrv  303 

sulphate  312 

All  'i!  mini  ins     .substances 

Alkaline  earths         .        .     323 

sulphide.                              313 

coagulated                           797 

Alkaloids                                751 

absolute  516 

Alkargen  .  .                            70)5 

urate                         724   810 

allylic             .                     544 

Alkarsin                                 763 

amvlcnic  556 

\llantoin  728 

Amphid   salts  281 

amylic  535 

Allox-in                                   728 

Anivdalin                            579 

anisic    .     .                         564 

Alloxantin                             730 

Amvl   acetate                        610 

Alloys                                     ''70 

Amyl  alcohols  and  ethers   535 

butylic  532 

\llvl  alcohol                           543 

Amvl  bases  ..  738 

cervlic.                                543 

cyanide                                 710 

cetylic                                 54'' 

iodides                                   5-15 

Amvl  oxide                            537 

cinnylic    554 

sulph-hvdrate  537 

cresvlic.  553 

oxide                                     545 

Atnvhiiuino                            738 

evmvlic     ...                        549 

siil])h-hv<lr'ite                      546 

etlialic                                    542 

A  ni  yl  cue                        480    536 

(•theme  556 

Allvlcne                                 4SC) 

etlivlic  515 

AHjil-Riilj'hocarl'nniide        7*'f 

chloride                              637 

Allyl-sulpbnric  *icid             545 

hvdmte                               538 

hexylic                                ;">.•','» 

isnprnpvlic  531 

Aloes                                       789 

jn  vricy'lic.                             543 

A  Inn  is                                       ',\'.Vi 

Amvl-Hvceriii                       669 

iionvlir  5-lt> 

Alumina                       .              334 

(n-tsiii-  nii 

phenvlic  

Aluminium   333 

Analcime  337 

clitnride                          :;.".:; 

prop  v  lie  531 

ethide                                   769 

..•aiiic  bodies    448 

71  * 

846 


INDEX. 


PAGE 

PAGE 

PAGE 

Assafoetida      789 

Battery,  constant    252 

diatts  and  cai  >on<i  es... 

Atmolysis      138 

A       'lino                                                                739 

Atmosphere    composition 

and  analysis...  154 

Wollaston's  252 

physical  constitution  of....    35 

Baume's  hydrometer  827-8 

Aniline  blue             747 

vapor  of  water  in  69 

Bay  salt   300 

Atmospheric  electricity...  119 

Bebeerine  .          760 

Atomic    theory  229 

Beer  519 

Atomic  weight,  definition 

Beet-root,  sugar  from  584 

of        223 

Bell  metal     ....                      356 

relation   of,   to   crystal- 

Bengal light                           421 

Aninril  fluids                  ..  ..  £05 

line  form  227 

Benzarnide  773 

Animal  limit  821 
body,  compounds  of  793 

relation   of,    to   specific 
heat  73,  227 
relation  of,  to  volume...  228 

Benzene  or  benzol  493 
additive  compounds  of...  495 
homologues  of.  493 

Atomic  weights,  table  of...  226 

substitution-products  of  494 

Atoms                         229 

Benzoates                                634 

combination  of  similar 

Benzohelicin  582 

Anisidine                                 551 

232    234 

Anisol                              551 

Atropine  760 

Benzoic  aldehyde  C33 

Anisyl  hydride                      695 

Attenuation  of  wort  520 

Benzoic  chloride  .      .             635 

Anthracene                            504 

iodide           ...                        635 

electrical  114 

oxide  635 

magnetic  107 

bases                                    761 

Atifite        ...             350 

chlorides                              418 

Auric  acid  and  oxide          370 

hydride                        .      419 

Auric    and    aurous    coni- 

Benzol  .     493 

oxides                                  419 

Australene,  or  Austratere- 

Ben/one     699 

sulphides         .    ..          ..  420 

benthene  488 

Benzonitrile      ....             .     710 

and  potassium  tartrute..  675 

Axes  of  crystals  260 

Benzophenone  699 

Apatite                                   330 

Axiuite               .                 .  337 

Azaleine   746 

Arabia   588 

Azotized  substances,  ana- 

Archil                                    785 

lysis  of                                 453 

Archimedes'  theorem.  29 
Arn'aiul  lamp  176 

Berthollet's     fulminating 
silver   .     .                           321 

Argol   674 

B. 

Beryl                                       337 

Aromatic  acids  633 

Beryllia                                     S38 

alcohols,  primary  548 

Balsams    790 

Beryllium                               337 

secondary  550 
aldehydes  690 

Barammonium  311 
Barilla                                     301 

B"taorsellic  acid  786 

bases  .  .     739 

ketones  696 

Biehlonniline                        741 

Arragonite  329 
Arrow-poison    of  Central 

325,  332 
Barley  siagar     .                     585 

Bichlorethylamine  735 

America  760 

Barometer                          39   41 

Arrow-root                             590 

Arsenates  4''3 

Bases       132 

Arsendiethyl  762 
Arsendimethyl  763 

from  aldehydes.  750 

Biethyl-urea    736 

Arsenic  4-22 

Bile                                               Sll 

bases.                                   762 

chloride  422 

Bilin                                         81'j 

detection  in  organic  mix- 

aromatic    739 

Biliverdin  813 

tures  425 

hydrides                              423 

xHineinyiamine  t?x 

oxides  423 

rea.-tions  of  425 

distillation                      74S 

sulphides  424 

Arsenites  423 

Arsenmethylium  766 
Areenmonomethyl  766 

artificial,        containing 
mercury  362,  769 

Binitrotoluene  497 
Biscuit  396 

Ar-ini's    471,  7<;2 
Arterial  blood  805 

phorus     and    arsenic 

series     767 

Bismethyl   767 
Bismuth     and     its     com- 
pounds                            4"7 

Artsads     231 

Asparagin  779 
Aspartic  acid  779 
Asphalt  506 

of  the  methyl  series  737 
nitrile  '.  7;53 
organic  751 
phosphorus  760 

reactions  of   429 
Bismuthic  acid  428 
Bisulphide  of  carbon  202 
Bitter-almond  oil  fci90 

INDEX. 


847 


PAGE 
5U(3 
500 
331 
402 
426 
180 
330 
331 
185 
351 
404 
805 
SOo 
805 
806 
806 
806 
806 
806 
805 
175 
708 
407 
421 
707 

PAGE 

PAGE 
Carburettcd  hydrogen 

Ijirht                                                             169 

Butyric  ucid      tilt) 

ethers                                   617 

Carbo-diphenyl-triamine...  745 
Carbonic  acid  ..  .            168    648 

C. 

Cacao  butter  623 

Black  flux 

ethers                                    649 

Bleaching  ..  -  
Bleaching  powder  
testing  its  value  
salts                              .    ... 

Carbo-triethyl-triamine  ...  759 
Carl  o-triphenyl-triamine..  745 
Carbyl    sulphate                    518 

Blende 

CaCOClyl                                                       763       rWminif     nr»!rl                                   rtT 

Wintered  steel  

chloride  764 

Cartier's  hydrometer  828 

Blood                              .    ... 

iodide                                   764 

Carragheen  moss  592 
Casein             .                        794 

circulation  of  the  
composition  of  the  

oxide  705 

sulphides     .  .                 .      766 

trichloride                           764 

Cassius,  purple  of  371 
Ca&tor-oil  540,  652 
Catalysis  240 
Catechu  f.73 

Cacodylic  acid    7f>5 
Cadet's  fuming  liquid  763 
Cadmium     and    its    com- 
pounds      .     .     .            352 

Catechin                                  (  73 

salts  reactions  of              353 

Cavendish's  eudiometer...  144 
Cellulose  592 

Blue  ink      

CfO-amu  316 

Caesium  alum            .             336 

Cements                                    3-/7 

Blue  li"-ht 

C'iffeine                                      756 

CeraMii                                      588 

Cerite  340 

708 
345 
229 
58 
819 
309 
767 
208 
546 
546 
208 
209 
209 
209 
39 
356 
411 
784 
526 
519 
421 
591 
742 
C95 

767 
568 
188 
275 
188 
783 
494 
5re 
694 
4!  »7 
35li 
393 
505 
750 
254 
177 
305 
507 
816 
418 
532 
710 
74'.) 
480 
finfi 

Calamine  350 
Calcium     and     its     com- 

Cerium  340 
Ccrotates  G'^6 

Bohemian  tdass  

Boilers,  deposits  in  

Cerotene    ..        .                      480 

carbonate                              3''8 

chloride                               3'76 

Cctene                                         480 

fluoride  327 
oxalate                        659    810 

Cet  U  alcohol  ;.42 
Chalk                                        328 

]>'  >ivthvl 

Boric  oxide  and  acid  

oxide  327 

stones  7''4 

phosphate            .       328    810 

Chameleon,  mineral  413 
Change  of  stat»  produced 
by  heat  55 

phosphide                             332 

Boron           

salts    reactions  of  332 

chloride 

sulphate         .                     328 

Charcoal,  animal  and  vege- 
table                                    165 

fluoride  

sulphides                              331 

Calculi  biliary  814 

urinary                                809 

Chemical  philosophy  219 
rays  of  the  eolar  spec- 
trum       95 

fusible  810 

Braiinite 

mulberry    .                        810 

Calomel                                   358 

Chimneys,  action  of  f.3 
ChincM'  wax  543 

Bread            .                     

Calotype  process  97 

Camphenu                  .              489 

Chinoline  748 

Camphol                                  546 

Chinoline-blue                       74S 

r  *'t'O 

Camphor                                 691 

Chinoidine                                7;"> 

of  liorneo           •                  546 

Cliitin     880    8(  3 

Chloral                             817    688 

Bromethyl     triethyl-phos- 

insoluble                               1  88 

Chloranil      .         .           ..     681 

Candle,  flame  of  175 
Caoutchin                  .       ...  491 

Chloraniline                           741 

Chlorates  180 

Bromide-*,  metallic  

Caoutchouc                              401 

Chlorl.vdrins     568 

mineral     506 

Caoutrhoucin                         491 

Chlorides,  metallic  :27:i 

C'ir-miel                                   5S5 

Chlurimetrv  331 

,,            . 

Chlorine  .        .            .              189 

Carbamic  ethers   776 
Carbamide  314,  777 
Carbides  of  hydrogen..lG9,  474 
of  iron                          401    402 

action  of,  on  organic  bo- 
dies     463 

JSron/e    

compounds  of,  with  hy- 
dio«'en                           181 

Carbimide  777 

with  nitrogen  IsT 

Bnicine 

Carbinol                                  512 

wit  li  carbon  1ST 

Bunsrifs  battery    

Carbon                                       103 

chlorides  187    5.',9 

estimation    in     organic 
bodies  457 

Burette 

bisulphide  'J02 
con)])ounds  with  oxvgen  165 
with  hydrogen  '  10<i,  474 
estimation     in    organic 
bodies                                  448 

Chlorisatin                               741 

Butter    620, 

Chlorites  185 

Chlorolien/eii'-s  4U4 
Chloroform                     .          567 

Butyl  alcohols  ;m<l  ethers 

Carbon  oxvchloride  204 
sulphoehloride  204 
Carbonates  168,  474 
analysis  of....                ...  306 

Chloropirrin                            553 

Hut  vlamiiie  

Chloroqiiinoiies  ('SO 
CMil.'i-i-alicylol  CH4 
Ihlorotoluenes....            ...   496 

Butvlene                  

JIutvlene  alcohol  .... 

848 


INDEX. 


PAGE 

PAGE 

Cyanogen:                           PAGE 

chloride  716 

Cholepyrrhin  £13 

radicals         237 

iodide     716 

sulphide  717 

vapors                             63    66 

Conduction  of  heat    52 

Cyanurates  714 

Conductors  of  electricity  .  116 

Cymene  499 

Clioiuuiii  ow* 

Conhydrine  760 

Cymidine  739 

Conine     760 

Cymyl  alcohol  549 

Constancy  of  composition  219 

Cymophane  337 

Constant  battery  252 

Cystic  oxide  810 

fluorides              438 

Constitutional  formulae....  231 

Contact  action  240 

oxychlorides  440 

Contractile  substance  818 

D. 

Copal  790 

Copper  353 

Dal  ton's  table  of  the  ten- 

j™i>y8e!*e '"*."  OOQ 

acetates  609 

sion  of  'aqueous  vapor...  829 

alloys    356 

Dammar-resin  .    .                  790 

Chyle                                      815 

arsenite  355 

Daniell's  battery  253 

pyrometer  47 

Cinchonidine              755 

chlorides  354 

Daturine  760 

cal  356 

Decane  477 

Decay  .                                    463 

Decene                                    480 

uneim  '"  50^ 

oxides  354 

p'nn               '1     f                    610 

pyrites                     ..  353    356 

Cinnyl  alcohol                       554 

salts,  reactions  of  356 

coal  165 

cinnamate                          641 

sulphate  355 

sulphides                             355 

li"ht                                      93 

Cork-borer  137 

Dehydratin""    agents     ac- 

Circulation  of  the  blood     805 

Corn-oil      538 

Citramide       780 

Corundum  334 

De  la  Rive's  floating  bat- 

Citrates          *      .                678 

Corrosive  sublimate  358 

ter  v                                    123 

Delphinine                             760 

Classification  of  metals...  271 

Cotton-xylo'idin  593 

Density         27 

Coumaric  acid  695 

Clay                                        336 

Coumarin       .                        694 

ironstone  400 

Cream  694 

tion  of                           459 

Cleavage        .           .              257 

of  tartar.  ..    .                     674 

Dew                                        101 

Coal  505 

Creatin  759 

gas  170 

Creatinine  .'    759 

Dextrin                        .            590 

Coal-tar  creosote          .         550 

Creosol                                   5^3 

Coal-tar,    volatile    princi- 

Creosote    550    563 

ples  of.  493 

Cresol    553 

Cobalt  407 

Crown-glass                            345 

Diabetes                          575    808 

amiuoniacal  compounds 

Crucibles  347 

Diacetamide                            773 

of  408 

Cryolite  .    ..                            334 

Diacetin                                   fill 

Cobalt-glance  407 

Cryophorus  68 

liiallyl       .                              487 

Cobalticvanides  709 

Cryptidine  748 

Dialysis                                     148 

Cobalt-salts,  reactions  of..    40(J 

Crystalline  forms  257 

Diamagnetic  bodies  110 

Cobalt-ultramarine  409 

Crystallization  .  .                  257 

Coccus  cacti  787 
Cochineal  787 

Crystallization,  water  of...  147 
Crystalloids                         149 

Diammonio-platinic    com- 

Cocoa oil  620 

Cubebs  oil  of                        491 

pounds  ..........  «J7o 

Codeine  753 

Cudbear  785 

Cohesion  239 

Coke  165 

Cumin  oil                           '  691 

Diastase                  519    577    591 

Colchicine  756 

Cuminol                                 691 

Diathermancy                        102 

Cold  produced  by  evapora- 

Cumene                   499 

Dibenzoyl   ..            ..             636 

tion  68 

Diben/yl                                 503 

Collidine  749 

Didymium                              340 

Collodion  594 

Diethenic  alcohol                  562 

Colloids  149 

Curarine                                  760 

Colophone    489 

Curd                                         795 

Colophony  790 

Cyamelide                               712 

Coloring     principles,     or- 

Cvananiline .      .                   742 

ganic  781 

Cyanates                                 713 

Columbium  or  Niobium...  634 
Combination  by  volume...  228 

Cyandiphenyldiamine  745 
Cyanides,  alcoholic  710 

mide,  sulphuric  771 
Diethyl-ethene-diammoni- 

Combustion  172 
furnan-  449 

Cyanine  748 
Cvaiiitt-                                       337 

Diffnsion  of  gases  137 

Diffusion  of  liquids               148 

heat  of  241 

Cyanogen  ....                    ,...  700 

Digestion...,                     ....  822 

INDEX. 


849 


PAGE 

Elements  :                           PAGE 

Ethyl  :                                PAOB 

-LM^IUCOS                         .  ...                       ^ 

genie                                22%? 

Emery  334 

telluride                                791 

Emetine                         .         760 

I)ij)lii'iiyl                                 503 

Emodin  787 

Ethylacetamide                     773 

Kmiilsin       579 

Ethylaniino                            735 

Diphenyl-ethene-diamine..  74-4 

Epichlorhidriu  569 

-urea  735 

Epidermis                                 803 

I)ij»l)c]"s  oil  748 
Disacryl                         815 

Epithelium  803 
Epsoinsalt  349 

Ethyl-ainyl-phenyl-animo- 
nium  iodide.    .".      .           742 

Disinfection                            331 

Equivalency,  variation  of..  233 

Ethylsaniline                        742 

Oisposin"-  influence  240 

Equivalents,  law  of.  221 

Ethyl-benzene  498 

Dissiici'ition                      .  ..  461 

Erbium    242 

Ethyl-codeine       .                 754 

Distillation                               61 

Ethyl-conine                          760 

Erythrite                                573 

Ethyl-methyl  oxide             526 

Diterebene                           489 

Essence  of  turpentine  488 

Ethyl-oxamide                     778 

Double  refraction                   91 

Essential  oils                          492 

Ethvl-phenylainine              742 

Double  salts                 282 

Ethalic  alcohol  542 

Ethyl-toluidine  742 

Dragon's  blood                      790 

Ethane  .               ...       467    475 

Ethvl-salicylol                      694 

Ductility  of  metals  269 

Ethene  170,  481 

Ethyl-strychnine  756 

Dulcite                                ..  573 

Ethene  alcohol  or  glycol  .  556 

Eucalyn  ..  578 

Ethene  bromide                   5tO 

Euchlorine.                           186 

chloride                               558 

Dvads                             331 

cyanide  711 

Dyes    yellow                           7^9 

iodide                                   560 

Enclase                                  33Z 

Dyeing  781 

oxalate  '660 

Eirxanthone  ~  789 

oxide              ...           .  .  560 

Dyslysin                                  812 

sulphide                                560 

Ethene-diamine  743 

Eventia  prur.astri  786 

Excretin              .          .         804 

E 

dide                                    744 

Ethene-hexethyl     diphos- 

Expansion  by  heat  42 

phonium.                           767 

of  liquids     .                  48   50 

Farth-metals  333 

Ethene  -  hexethyl  -  phos  - 

of  gases  51 

pharsonium  .    767 

of  solids  45 

Ebonite                                   491 

Ethene  -  tetrethyl  -  phos- 

of  water  .           .  .               50 

Ebullition                      57 

phammonium  767 

Effervescing  draughts  675 

Ethene  -  triethyl  -  phos  - 

F 

E(r(r  albumin       791 

Ethereal  salts  409 

Egg  white  of                    .  .  791 

Etherincation  „  524 

Fat  origin  of  in  the  ani- 

Ela'idin                                   629 

mal  body                             825 

Eluldehyde  687 

diatomic  555 

Fats  .           ..   .      566  623   625 

Elastic  tissue                 ..  ..  818 

Fatty  acids.       .                     597 

Electric  battery  119 

monatomic  510 

Feathers  803 

current          119 

pentatomic    572 

Fecula  589 

tetratomic                   .          571 

Felspar                           .         336 

Electric  discharge  116 

triatomic  565 

Fermentation  463 

Electric  eel       122 

Ethides  metallic...  768 

butyric                    617 

Ethyl   acetate                        610 

lactic                                  646 

Electricity     positive    and 

borates   528 

bromide                           ..  522 

Ferments                .  .    463   646 

Ferrate4*                        .          399 

Electro-chemical    decom- 

carbonates         649 

Ferric    and    ferrous  com- 

chloride                              522 

pounds                  398 

Electrodes                              °45 

cyanite                                714 

Electrolysis                     .    ..  245 

cyanide                                710 

Ferrieyanides  709 

Electrolytic      decomposi- 

cyanurato  714 

Ferrocyanides    706 
Fibroin                                   £03 

Electmlytos                  •     •  •  24  f) 

Ficus  rubriginosa,  resin  of  549 

nitrate                                  526 

Fire    blue  421 

nitrite                                  526 

-damp                                   178 

Electro-negative  and  elec- 

oxalates              660 

red  and  green  326 

Flame  structure  of..  .172,  175 

Eleetrophorus                         119 

oxide                                    f)''.0) 

Klccho-plating  2f>n 

palmitatc           .    .           .  622 

berg's  phosphates  287 

Kli-ctruscope              10(5 

Flint-glass          £44 

Electrotype                                      'T)4 

Elementary   bodies    fable. 

Fluorescence  91 

stearate                                 C'^o 

Fluorides    metallic  276 

symbols  of                           "•'li 

Fluorin"                                   192 

Klenii'iltS   127 

svilph-hvdrate  -  529 

Fluor-spar  327 

sulphides                              530 

Food             ...           822 

sulphites                               527 

Formates                       .              C05 

lent  value.  ....             ....  2C6 

sulnhocarbonates  ...  650 

Formula}.....                     ...   226 

850 


INDEX. 


Formulae  :                           PAGE 

PAGE 

Glass       344 

empirical  and  molecular  457 
graphic  and  glyptic  231 

i"    tiotial                                981     472 

346 
307 
823 
143 
337 
574 
578 
802 
823 
823 
566 
569 
644 
594 
813 
801 
801 
774 
555 
725 
692 
580 
692 
692 
231 
369 
705 
371 
370 
371 
258 
609 
336 
575 
231 
164 
35 

132 

27 
459 
326 
353 
376 
266 
253 
255 
563 
758 
758 
826 
588 
588 
634 
591 
588 
588 
593 
356 
294 
491 
328 

799 
399 

798 
789 
800 
798 

363 

Gliadin  

Franguliu  571 
French  weights  and  meas- 
ures    837,  838 
Frigorific  mixtures  56 
Fruit  sugar                    837    838 

Glue       

Gluten  

Fuchsine                                 746 

Glutin  

Glycerin  

Glycide  

Fucusoi                                   696 

Fulminates                             714 

Glycogen  

Glyco-hyocholic  acid  
Glycocine      614, 

Fulminurates  716 

Glvcocol  

Fuming  liquor  of  Libavius  390 
Furfur'imide                            696 

Glycollamide  

Glycols  

Furfurine                               696 

Glycoluril  

Furfurol                                 695 

Gly  cosine  

Furnace,  reverberatory....  173 
Furnace  for  combustion...  451 
Fusel-oil                                  535 

Glycyrrhizin  

Glyoxal 

of  grain  spirit  537 
Fusibility   of   metals  268 
Fusible  calculus    .     .          810 

Glyptic  formulas  
Gold  and  its  compounds... 
cyanide  of.  

Fusible    metal  429 
Fustic  wood  789 

Gold-leaf            

-salts,  reactions  of  
-standard  of  England... 

G. 

Gadolinite                    337    342 

Galactose  578 

Graphic  formulae  
Graphite  

Galena  394 

Gallates  671 
Galls,  nut-  672 

Gravitation  
Gravity,   specific  — 

Galvanism  ...         .      119 

of  metals  

Galvanometer                103   122 

Garancin  788 
Garlic,  oil  of.  545 

Greenockite  

Garnets  ....                             337 

Green  salt  of  Magnus  
Groups,  isomorphous  
Grove's  battei'y  

Gas,  coal  and  oil  170 
defiant  170,  557 
battery  255 

burners         .                    177 

Gas    furnace    for  organic 
analysis  451 
Gases,  absorption  of..  ..139,  150 
capillary    transpiration 
of.  140 

Guanidine  

Guano  724, 
Gum  

arabic  .. 

collection  and  preserva- 
tion of                            199 

British 

diffusion  of.  137 

effusion   of  140 
eudiometric  analysis  of  156 
expansion  of.  51 

Gun-cotton  

Gun-metal  

liquefaction  of  66 
occlusion  of    140 

osmose  of.  138 

Gypsum  

physical  constitution  of    35 
specific  gravity  of  132 
specific  heat  of  71 
Gas-holder  130 

H. 

Haematin 

Gastric  juice  811 

Gaultheria     procumbens, 
oil   of.  654 

Haematite  
Haamatocrystallin  

Gelatin  801 

Gelatin-sugar  801 
German  silver  407 

Ilaunin  crystals 

Haemoglobin  
Hahnemann's  soluble  mer- 
cury   

Geyser  springs  of  Iceland  153 
Gilding  371 

PAGE 

Hair 803 

Halitus 806 

Halides,  acid 469 

Haloid   ethers 4t;8 

Haloid  salts 281 

Hardness  of  water 328 

permanent 328 

temporary 329 

Harmaline 756 

Harmine 756 

Hatchetin .  507 

Hausmannite 412 

Heat,  absorption  of. ...101,  106 

animal 821 

capacity  for 69 

conduction  of 54 

developed  by  the  elec- 
tric current 255 

dynamical  theory  of. 77 

expansion  produced  by.    42 

latent,  of  fusion 55 

latent,  of  vaporization..     57 
mechanical  equivalentof    75 

radiation  of 99 

reflection  of. 99 

relations   of,   to  chemi- 
cal affinity 241 

sources  of 74 

specific 69 

transmission  of 102 

Heavy  spar 324 

Helicin 582 

Helvite 337 

Hcmihedral  crystals 2C3 

Hemming's  safety-jet.. 141,  179 

Hepar  sulphuds 298 

Heptyl  alcohols  and  ethers  539 

Ileptylene 480 

Heiilandite 337 

Heveene 491 

Hexads 231 

llexethyl-ethene-diammo- 

niuni  iodide 744 

Hexyl  alcohols  and  ethers  539 

Hexyl-carbinol 541 

Hexylene 480 

hydrate 480 

Hofmann's  gas-furnace  for 

organic  analysis 451 

Homologous  series 466 

Honeystone  665 

Hops,  oil  of 520 

Hornblende 350 

Horn  silver 319 

Horny  substance 802 

Huan'o  724 

Humus 585 

Hydantoin 725 

Hydrates 147 

of  turpentine  oil  489 

Hydrides   of  alcohol-radi- 
cals   478 

Hydriodic  acid 189 

Hydrobenzamide 690 

Hydrobromic  acid 188 

Hydrocarbons,  table  of....  467 

Hydrochloric  acid 181 

Hydrocyanic  acid 701 

Hydroferricyanic  acid 709 

Hydroferrocyanic  acid 708 

Hydrofluoric  acid 192 

Hydrofluosilicic  acid 210 

Hydrogen-  136 

antimonide 419 

arsenides —  ...  423 


INDEX. 


851 


Hydrogen  :     .                     PAGE 

Iridinm  :                               PAGE 
aiiimonjacal  compounds 
of  384 

PAGE 

Lac  tin                               ..    587 

carbides                               169 

Lactone  647 

chloride                               181 

Lactose  587 

combination     of,     with 
oxygen                           140 

Iron                     .                    397 

Lake                      .                  781 

acetates   609 

dioxide  153 
estimation  of,  in  organic 
bodied                                448 

ben/<rlte                                          634 

Lampblack                               16;") 

carbonate  400 

chlorides                             398 

safety-                                      178 

iodides                                 399 

manufacture   4(Jl 

without  flame  143 
Land  and  sea  breezes  101 

nitrates  401 

monoxide  143 
phosphides                          215 

oxides                                  399 

phosphates  401 

Lapis  lazuli  309 
Latent  heat  of  fusion  55 

selenide                 205 

salts,  reactions  of.  401 

sulphates                            400 

telluride                              ''07 

sulphides  401 

Isatin             .                        783 

Laumonite                              337 

Hydrogen  snlts                      133 

Ixathyde  783 

Law  of  equivalents  221 

Isinglass            801 

Law  of  even  numbers  232 
Law  of  multiples  220 
Laws   of  combination  by 
volume                               228 

Hydrometer                       ..    32 

Isobutyl  carbinol  535 

Hydrometer  tables  827,  828 
Hydros'Uicyl'imide                693 

Hydroselenic  acid  205 
H'ydro.sulphuric  acid  200 
Hydroxyl                                237 

Laws    of  combination  by 
weight                        .         219 

Isomerism  in  the  olefine 
series         483 

Lead                                         394 

Hydrometer,  dew-point....    69 

acetates             .    .     .          609 

paraffin  series...  .  478 
Isomorphism  264 

alloys                                 397 

Hyoscyamine  760 
Hyodyslysin            814 

carbonate  396 

chloride  .  395 

Hypophosphitcs                     214 

nitrate                                 396 

Hyposulphates  149 
Hyposulphites   199 

Isoproppyl     alcohol    and 
ethers                         531 

oxides  395 

Isopropyl-carbinol  533 

J. 
Jade                    .          ....  350 

red                                     395 

I. 

salt?  reactions  of  397 

sulphide  394 

tree.      .            255 

Idrialin  507 

Jet      505 

white   396 

Idryl                                        507 

Jews'  pitch   505 

Leaven              .                     520 

jo-nition                                   173 

Juice  gastric              811 

Imides                    471    773    775 

Imidogen-bases          ..  237    733 

K. 

Kakodyl,  see  Cacodyl  763 
Kjilinm             .            ...  .   290 

Inclination,  magnetic  109 
Incrustations  in  boilers...  229 
Indian  yellow                         789 

Lci>i<line                          .  ...  748 

Lepidolite                               316 

India  rubber  491 

Leucine                          619  751 

Indican           .                ...     583 

Kaolin                                       337 

Leucoline                                748 

Indiglucin  583 
Indigo    583   781 

Kelp  189 
Keratin                 803 

red                      782 

Leyden  jar                             118 

vat                                       782 

Ketoues                          470    6% 

I  ichens                                     785 

white  or  deoxidized  7«2 
Indin  783 

Kino                                       672 

Liebi<>-'s   bulbs                     451 

Kir                ,                ..      ..  507 

Liebig's  condenser  62 
Light,                            83 

Indium  416 

Kre.atin,  seeCreatin  759 
Kreatinine,  seeCreatinine  759 
Kreosote,  see  Creosote  550,  563 
Kupfernickel  405 
Kyan's  method  of  preserv- 
ing timber                         358 

Induction  coil      126 

blue  or  Bengal  ....  421 
chemical   rays  of  95 
dispersion  of  85 
reflection  and  refraction 
of                                      83 

•  •!<•(•{  n  (magnetic  124 
magnetic  108 

Ink,  label  7'.K» 

blue,  sympathetic  407 

Inosite                                       578 

L. 

Labarraque's   disinfecting 
fluid                                     330 

Iniilin                                        592 

Inverted  sugar     585 

Li<rnin                                     592 

lodicacid  190 

Lignite  .                      504 

Iodides,  metallic  276 

Lime                                        327 

Iodine  188 

Label  ink                              7(»0 

action    of,    on     organic 
bodies    '.  4tU 

Lac  790 

Lac  dye                                  7(.l(i 

Limestone.  228 

Liqnelaetion   of   gases  66 
of  carbonic  acid  66,  167 
Liquids,  boiling  points  of.    57 

and  nitrogen  191 

and    o\v<ren     ...          ..  .  190 

Lactates                                  <>47 

chloride                               1()1 

lodoform    ;";»><> 
Iridiuui  3S2 

Lactic  ethers  <US 
Lactide....                          ...    647 

latent   heat   of....,        ,.     55 

852 


INDEX. 


Liquids  :                               PAGE 

PAGE 

Methyl  :            ,                 PAGE 

specific  gravity  of.  27 
volatile  organic,  analy- 
sis of  452 

Melam                                     720 

Melamine  720 
Melaniline  745 

sulphide  515 

Methylamine  737 

Liquorice   sugar  580 
I  ith-irge                                 395 

Melene              4SO 

Methylammonia                    737 

Melezitose                              587 

Methylated  spirit                  518 

Lithia                      316 

Melitose  587 

Methyl-benzene  405 

1  ithium                                  316 

Mellite  665 

Methyl-carbinol  512 
Methyl  -  ethyl  -  amyl  -phe- 
nylammonium  742 
Methyl-ethyl-benzene  499 
Meth.yl-ethyl-carbinol  534 
Methyl-glycocine  614 
Methyl  -hexyl-carbinol...  541 
Methyl-isopropyl-carbinol  538 
Methyl  mercaptan  515 

hydrate                              31  6 

Mel  lone                  -                 720 

Mellonides  721 

Loadstone                      107    399 

Membranes,  mucous  815 

Mercaptan  510,  529 

Lophine                                750 

methyl-  515 

Luminosity,  conditions  of  173 
Lupulin     520 

Mercurammonium  salts...  362 
Mercuric  ethide  769 

Lungs  821 
Lutidine                                 749 

Mercury  357 
acetates  610 
chlorides  358 

Methyl-morphine  753 

Methyl-cenanthol  541 
Methyl-salicylol  693 

Lymph  815 

M. 

Madder                                  787 

Mica  337 

fulminate  .                .         715 

Microcosmic  salt  308 
Milk  816 

iodides  359 

nitrates  360 

spirit  from  588 

oxides                 .                 360 

Milk-sugar                             587 

Magenta  746 

sulphates  361 

Mindererus,  spirit  of.  608 

Magnesia  349 

sulphides  361 

alba                                     349 

salts  reactions  of             363 

waters,  tables  of  832-S35 
Molasses  584 

Magnesium  347 

Mercury-compounds,   am- 
moniacal  362 

Molecular  actions  239 

phosphates                     .  349 

Meridian,  magnetic  109 
Mesityl  chloride  699 
Mesitylene  499    699 

Molecules       °25   230 

salts,  reaction  of  350 
silicates  353 

Molybdenite  .                        445 

Molybdenum  444 

sulphate  349 
Magnetism                            107 

Mesotype  337 
Metacetone,  seePropione..  697 
Metacinnamene  501 

Molybdenum  -salts,  reac- 
tion of                                 445 

Magneto-electricity  124 
Magnus,  green  salt  of  376 
Malachite                               355 

Monoacetin  611 

Mctaheemoglobin  799 

Monads  231 

Metalbumin                           798 

Malamicacid  778 
Malamide  779 
Malamyl-uitrile                     779 

Metaldehyde  6S7 
Metallammoniums  315 
Metalloids                             1"7 

Monamines  732 

Monobasic  acids...  282,  597,  642 
666,  676 
Monogens  221 

Malates  ...  669 
Malleability  of    metals...  268 
Malting  519 

Metals  267 
chemical  relations  of...  270 
classification  of                 271 

Mordants                               781 

Maltose          ..                     577 

physical  properties  of...  '267 
Metameric  bodies  475 
Metapectin                            588 

Mauganates  413 

Morindoue  789 
Morphia  or  Morphine  751 

Manganese  410 

chlorides    ...                  410 

Metaphosphates  285 
Metastanuates  392 

fluorides  411 

Mosaic  gold  392 

oxides    .                             411 

Metastyrolene  501 

salts,  reactions  of.  414 
Marsh's  test  for  arsenic...  427 
Manganite                              411 

Mucin                            800   815 

Metatungstates.  .                  442 

Mucous  membranes  815 
Mucus  800,  815 
Mulberry  calculus  810 
Multiplier                 123 

Metavanadates  431 
Meteorites  398 
Methane  169    466   474 

Manna  sugar  587 
Mannitan  573 

Mannite  572 

Methene  .                              481 

Multiples,  law  of  219 

Mannitose  577 

Methenyl  ethers                  665 

Manures  824 

Methenyl  -  diphenyl  -  dia- 

Murexide  ....  732 

Maple,  sugar  from  584 

Marble  2°8 

Methide,    aluminium  769 

Muriatic  acid  181 

Marc-brandy,  fusel-oil  of...  530 
Margariu  629 

Methyl  •                                  478 

Must                                        518 

Mariotte's    law  39 
Marl  337 

acetate  610 

Mustard,  oil  of  719 
Mycose             587 

Marsh's  apparatus  427 
Marsh  gas  169 
Marsh  mallow  779 
Massicot  .              395 

Mycomelio  acid  729 

chloride  513 
ether  513 

Myricin  54:5 
Myricyl  alcohol  543 

Mastic  790 

Mauve  745 

N. 

Naphtha  505 
Naphtha,  Burmese  507 
Naphthalene  502 

Mauveine  ,.     746 

nitrate  514 

Measures  839 

oxide  513 

Meat  823 

Merhn  nical   equivalent  of 
heat  „  75 

phosphates..,  ,  51  5 
salicylate  (i.">4 
silicates  515 

INDEX. 


853 


PAGE 
Naphthalidine       743 

PAGE 

Octane  467   477 

PAGE 

Oxalates                                659 

Naiveine                                   754 

Octene  or  octylene  467 
glycol  556 

Oxalic  acid                              657 

ethers                                    660 

Narcotine            753 

Octyl  alcohols  and  ethers.  541 
chloride                               542 

\efte-de'>-il                              507 

\ephelin      337 

carbinol  543 

Oxamic  acid                    659  777 

Nervous  substance  818 
Neurine                                   803 

(Enanthol  or  oenanthylic 

ether  6(il    777 

Oxamide                         659    778 

Neutrality  of  salts  283 
Nii-kel                      405 

Oil  gas  172 

Oil  of  aniseed  695 

Oxatyl                                     595 

-salts  reactions  of          .  406 

Oxides                                     132 

Nicotine    760 

of  bitter  almonds  690 
of  cicuta     691 

alcoholic  469,  509 

metallic                                 278 

Niobium                            ...  634 

N  i  tramline                             742 

Oxygen                                  128 

Nitraniside      695 

of  cloves  ;.  491 

its    action    on    organic 
compounds  462 

Nitranisidine                .      .   551 

of  copaiba  .                        491 

\itranisol                               551 

of  cubebs  491 
of  cumin  .  .         691 

Nitrates  159 

of  the  glycols  560 
of  the  polyglucosic  alco- 
hols.                               589 

Nitre                                      294 

cubic  308 

of  garlic  545 
of   gaultheria    procum- 
bens                                  654 

sweet  spirits  of  526 
Nitric  acid                             158 

Oxygen-salts  133,  280 
Oxy-hydrogen  flame    and 
blowpipe                         142 

action  of,  upon   amyla- 
ceous and  saccharine 
substances  593 

of  juniper  491 
of  laurel                              491 

safety-jet                             141 

of  lavender  491 

Oxvphenol  562 

acid,  fuming   161 

of  lemon     ...                 .    491 

Ozocerite                               507 

Nitrides    metallic            ...  162 

Ozone                                     135 

Nitrile-bases  470,  732 

of  mustard   711 

P. 

Palladium                             278 

Nitro-benzene?  495 

Nitro-cumene        499 

Nitro-cymene                         500 

Nitroform  566 

of  ptychotis  554 

Nitroglycerin                        568 

ammoniacal  compounds 
of                                    479 

Nitrogen  153 

of  rue  .        689 

chloride      .  .        .          ...  189 

of  spiraea  ulmaria  693 
of  thyme    554 

Palmitins                               629 

compounds  with  oxygen  157 
with  hydrogen  162 

Palm-oil             622 

of  turpentine  488 

Pancreatic  fluid                     814 

with  boron               .    .  208 

of  vitriol                            196 

dioxide  160 

of  wintergreen  654 
Oils,  drying  and  non-dry- 
ing                                 630 

Papyrin  593 

estimation    in    organic 

Paraban                                  729 

iodide     191 

volatile  491    492 

Paraffin               477 

monoxide  160 

Oleflant  gas                            170 

Paraffins                                  474 

pentoxide                            158 

Olefines                                    459 

substitution-products  of  478 
Paraglobin                             796 

tetroxide  161 

compounds  of,  with  hal- 
oo'ens                              482 

trioxide  Til 

Paraglobulin                         796 

Nitrolactin  588 

Oleins  629 

Paralactates    ....          ..        647 

Nitro-naphthalenes    503 

Olive  oil  629 

Paralbnmin  795 
Paramagnetic  bodies  110 
Paramide  665 

Nitro-phenols         .      .          552 

Nitro-prussides                      704 

Opianine  754 

Nitre-thymols  554 

Nitro-toluenes    .                  497 

Orange-flowers,  oil  of.  691 
-peel   oil  of                         691 

Paramylene  537 

ether  526 

Orcein  691 

Paraniline      741 

oxide  161 

Orcin        .                                691 

Parapectin                              588 

Nitro-xylenes  498 

Organic  bases  732 
chemistry,  the   chemis- 
try of   carbon    corn- 

Nomenclature      ..                132 

of  alcohols                          512 

l>.  '.'!]  i  ''  '  'lir  ,C  ,  (Jjo 

of  hydrocarbons  469 

Parmelia  parietina  787 

of  salts  2*2 

substances,     action     of 
heat   on  462 
substances,  classification 
of                                      464 

Paviin                                      579 

Nonane  .467,  477 

Pe'irl-'ish                                  296 

Nonene  480 

Pectin                                        588 

Nonvl  alcohol  542 

Pendulum,  compensating.     46 
Pentads                            .         231 

Nordhausen  sulphuric  acid  T.Mi 
Notation,  chemical  225 
Nut-galls  ..  672 

substances,    decomposi- 
tion of  462 

Pentetlivl-ethene-diammo- 
nium  iodide  744 

Pepsin                             .   .  ..               SOO 

substances,   elementary 
analysis  of.    4-18 
substances,  synthesis  of  447 

Orgnno-metalHc  bodies  471,  768 
Orpimont                                  4->4 

Nutrition,  animal  S-_>2 
plastic  elements  of  S-_>4 
vegetable  825 

Peptone  797 
Perchl,  .rates  -  1^6 

Percussion-caps.  715 
peris-ads                           "31 

0. 

Occlusion  of  gases  139 
Octammonio-platinic  com- 
pounds    377 

Orthophosphatcs  2S5 

Osmium    3S7 
Osmose  of  gases          ....      138 

Permanganates  413 
Peroxide  of  chlorine  1Sf> 
Persulphide  of  hydrogen..  202 
Peru  balsam.  ...              ...  7'J1 

of  liquids                             149 

Osseiu  ....                         ...  818 

72 


854 


INDEX. 


PAGE 

PAGE 

PAGE 

Proportions   multiple          220 

diamaguetic  112 

Propyl  478    531 

Pt-tlitf>                          316   337 

electric     115 

Propyl  alcohol  531 

IVtinine                                •  749 

magnetic  107 

Propylamiue  734 

IVttunkofer's  bile-test  813 

Polarization  of  light  91 
circular  93 

Propylene,  see  Propene....  480 
Propyl-phycite  571 

'            .',",ln  "                                         01- 

Poles    electric  ..115,  245 

Prota^ou  803 

1  (  tunty.t  

Polybasic  acids  282 

Protein      .                              794 

pfw       V'  g-g 

Polyethenic   alcohols  561 

Prussian  blue  707 

Phenamylol  551 

Polygenic  elements  222 

Prussiate  of  potash,  red...  709 

Polyglucosic  alcohols  583 

yellow  706 

Phenetol                                 551 

oxygen  ethers  of  589 

Prussic  acid  701 

Phenol                                    550 

Polylycerins  569 

Pseudo-erythrin                    786 

Phenols                                   550 

Polymeric  bodies  475 

Pseudo-morphine  754 

diatomic  562 

xylylic                                 553 

Populin  582 

Ptvalin  810 
Puddling  .                           403 

Phenyl                               ...  494 

Purple  of   Cassius  371 

Porphyry              •              •    336 

Potash  293 

Purpurin                                7  88 

chloride                               551 

crude                296 

Potash-bulbs  450 

liydrate                               550 

Potassammonium  311 

Pus             ,                     800    815 

Plu-nvlainine      739 

Potassio-ferrous  fcrricyan- 

Putrefaction  463 

Phenyl-dibenz'imide             773 

ide                                   707 

Pyin                               800   815 

Phenylene                              500 

Potassium             .                 290 

acetates  608 

Pyrites                                    401 

Philosophy    chemical          219 

alum              335 

Phloretin                                581 

Phlorizin         581 

bicarbonate  297 

Phloroglucin                         570 

bisulphate                           297 

Pliorone                                 6fl4 

bromide                               292 

carbonate  296 

Pyrolusite      .                        412 

Phosphates                            285 

chlorate           .           .  ...   295 

Phosphide  of  calcium          332 

chloride                               291 

Phosphine  285 

Phosphines                   471    760 

cyanide                                703 

Pyroxylin                              593 

Phosphoretted  hydrogen..  215 

ferricyanide  709 

Pyrrol  749 

Phosphoric  acid  214 

Phosphorus     ..                      212 

hydrate                                293 

Q 

-bases  604 

iodide  291 

bromides                             217 

chlorides                            216 

estimation  of  in  organic 

nitrate  294 

Qu'irtene                        4(j7    480 

oxalate                                 659 

hydride                               215 

oxides                                   292 

Chrirtine                         4G7    487 

iodides  217 

Qu'irtyl                                   467 

sulphides  217 

ethers                                  532 

Photography  96 

sulphates                             297 

Phycite  571 

sulphides                             298 

Picoline  748 

(hercetin  '<me  587 

Picro-erythrin....                  785 

tartrates                              674 

Quercite                                  572 

Pinacone              -.                 699 

tetroxid0                             293 

Finite  572 

urate                                  724 

Pipcrine                                  7€0 

Pitchblende  414 

Potassium-methyl                769 

Quina                 .           754 

Pitch    mineral                  .    505 

Plants,  supply  of  carbon  to  824 

of  .  299 

Plaster  of  Paris  218 

Potassoxyl                              237 

Quinicine                           ...  755 

Plate  glass  218 

Potato-oil  535 

Quinidine  755 

Platinum  372 

Precipitate  red                     360 

Quinine   7;">4 

ammoniacal  compounds 

white                                    362 

of                                    374 

Prehnite                                  337 

Quinoidine                         .     755 

chlorides                             373 

Quinone                                   680 

oxides  374 

salts  reactions  of     .    .    378 

Prism   Nichol's                        93 

Quintane                         467    477 

sulphides               374 

Proof  spirit                            518 

Quintene                467   480    482 

surface  action  of  142 
Platinum-black  373 

Propane  467,  475 
Propene  480 

Quintene  glycol  556 
Quintenyl  alcohol         569 

Plumbago  104 

Quintine                            .  .  487 

Plumbethvl  770 

Plumbic   compounds  395 

Propine  686 

Pneumatic   trough  129 

Propione  ...  697 

ethers....                       ...  535 

INDEX. 


855 


R. 

I 

AGE 
677 
99 
237 
507 
424 
32(3 
395 
412 

465 
403 
99 
83 
91 
84 
427 
816 
237 
790 
549 
820 
505 
508 
173 
sso 

Salt:                                  PAGE 
definition  of  133    280 

Salts    acid  281 

Radicals          .           

basic  283 

binary  theory  of               281 

Realgar 

double  .        281 

Red  lead               

Red  oxide  of  manganese... 
Reducing  agents,  action  of, 

Saltpetre  294 

Sai>(»nification  567 

Refining  of  pig-Iron  
Reflection  of  heat  

Sipphire                                 334 

Sarcolactates  647 

of  light               

Refraction,  double  
of  light  

S'ircosine                 .       614    759 

Sca"-liola  328 

Reinsch's  test  for  arsenic- 
Rennet 

Sea-water,  composition  of.  146 
Secondary  butyl  alcohol.  ..  534 

Residues   

Resins                 

Resin  of  Ficus  rubiginosa 

octyl  alcohol  541 

propyl  alcohol  531 
electrolytic    decomposi- 
tion                                  247 

Retene        .          

Reverberator  y  furnace  
Rhodium     ...         

Seggars         347 

Seiirnettc  salt                         675 

River  -  water,  analyses  of  834, 
835 
Roccella  tinctoria  786 

Selenetted   hydrogen  205 
Selenic  acid                         .  205 

Selenides  metallic                289 

Rocoellinin 

786 
675 
W6 

Ruck-oil 

Selenite                                   328 

Rock-salt 

300 

Selenium                                 204 

336 
740 
746 
679 
787 
788 
788 
788 
316 
336 
334 
398 
385 
387 
393 

93 
584 
178 
788 
789 
592 
358 
312 
592 
581 
693 
653 
692 
654 
693 
692 
692 
581 
682 
811 
801 
800 

Septivigintene  480 
Series,     homologous    and 

Rue,  oil  of  

Serpentine    ..  .                  .    350 

Serum  of  blood                      8u6 

Rubiadn  
Rubiacic  acid  
Nubian                         

Scxdeccne    480 

Sexdecyl  alcohol         .          542 

Sextino                                    487 

Rubidium 

Sexvalent  elements  331 
Sbale      ..              .                  337 

Ruby             

Shellac                                       790 

Rust 

Sikes's   hydrometer              828 

Silica                           ....         210 

-salts,  reactions  of  
Rutile 

Silicated  hydrogen                211 

Silicates  of  aluminium....  336 

S. 

Silicic  acid                              210 

Silicic  ethers  515,  529 

Silicotungstates   443 

Silicium   or  Silicon              209 

chloride                               211 

fluoride  210 

hydride               .   .             211 

oxide  210 

Sa(ro 

Silver       317 

acetate         610 

Sal-ammoniac  
Salep                    

ben/oate              ..          .    634 

carbonate  321 

Salicin 

chloride  319 

Salicylamido               

cyanate  713 

aldehyde 

S'llicylites 

fluoride    319 

Salicylol 

fulminate      714 

Salieylous  acid      

liyposulphate  321 
hyposulphite  321 
Iodide      319 

Baliva 

oxides                     .              .  319 

Milplrite                                 320 

Salt.   common.... 

Silver-alum....                   ....  ."2S 

PAGE 

Silver-salts,  reactions  of...  321 
Silver-standard  of  England  322 

Sinamine 720 

Sinapuline 720 

Size 802 

Skin 818 

Slate 337 

Smalt 409 

Smee's  battery 254 

Soap 625 

Soup-stone 350 

Soda 301 

Soda-ash  process 302 

Soda-ash,  testing  its  value  303 

Sodammonium 310 

Sodium ,..., 299 

acetate 608 

bicarbonate 303 

bisulphate 307 

borates  309 

bromide  301 

carbonate 301 

chloride  300 

cyanide  704 

ferrocyanide 708 

hydrate 301 

hyposulphite 307 

iodide 301 

nitrate 308 

oxalate 659 

oxides 301 

phosphates 308 

sulphates 307 

sulphides 309 

tartrates 675 

unite 724 

Solaniue, 769 

Solar  spectrum 86 

Solder  397 

Soleil's  saccharimeter 93 

Solids,  expansion  of 45 

specific  gravity  of 29 

Solubility  of  salts 147 

Soranjee , 789 

Sorbin 578 

Sorrel,  salt  of «;,y 

Spar,  calcareous 229 

Sparteine  760 

Spathose  iron  ore 400 

Specific  gravities  of  metals  267 
gravity    of    solids    and 

liquids 27 

heat 69 

Speculum  metal 356 

Spectroscope 88 

Spectrum 86 

Spectrum-analysis 87 

Spoiss  405 

Spermaceti 543 

Spirit,  methylated 518 

Spirit  of  Mindererus 608 

Spirit-lamp 176 

Spirits,  table  of  spec.  gr. 

of 830,  831 

Spodumene 316,  337 

Spongin 803 

Springs 147 

Spring-water,  fresh,  analy- 
ses of 834,   835 

Staimites,  metallic .".'.H 

Stamicthyls 770 

Stannic  and  stannous  com- 
pounds    :;«.io 

Stannic   rtliide 770 

Stanuoso-stannic  ethide...  770 


856 


INDEX. 


PAGE 

Sulphur:                            PAGE 
and  carbon  *•  202 
bromides    204 

PAGE 

Tetrethyl-ethcne-diamino- 
nium  iodide  744 
Thallium     and    its     com- 
pounds    305 

State,  change  of,  by  heat..     55 
Steam,  clastic  force  of  59 

chlorides                     203 

estimation  of,  in  organic 
bodies  457 

Thallium   salts,  reactions 

Steam  engine  CO 
specific  gravity  of  145 

iodides  204 
oxides  and  oxygen  acids  194 
Sulphur-acids  and  bases...  289 
Sulphuretted  hydrogen....  200 
Sulphuric  acid  196 
ethers            514,  526 

of  368 
Thebaine  754 

Theine  756 

Theobromine  757 

Stearin  625 

Thermo  -  electrical    phe- 
nomena    103 

Stearoptene  492 

Sulphurous  acid  195 

Thermometer  42 
differential  45 

gteel                         403 

Sulphur-salts  289 
Surface  action  of  platinum, 
charcoal,  &c  142,  165 
gweat              811 

Thermomultiplier  104 
Thialdiue  750 

Stickhic    •  790 

Thiosinamine  720 
Thorina  339 

Stilbite                                      337 

Sycocerylic  alcohol  549 
gylvic  acid  790 

Thorinum  339 

Thorite  339 

Symbols,  chemical  129,  330 

Tbujin  582 

Strontium    and    its    corn- 

Thymol  554 

Synthesis     of     organic 
bodies                                   447 

Tin  389 

Strontium  salts,  reactions 
of          326,  332 

alloys                                   392 

Synthetical     method     of 

chlorides  390 
fluorides                         ...  391 

oxides                                  391 

Styracin                                  641 

Systems  of  crystals  200 

T. 
T'tlc                                        350 

sulphides  392 
Tin-salts,  reactions  of  392 
Tincal     309 

Tinned  plate  392 

Sublimate,  corrosive  358 
Sublimation                     61    634 

Tissue,    membranous  818 
lifueoxis  592 

Tannates          672 

Substitution                  225    330 

T-uining                         .  .  ..  818 

Titanium    393 

Tolene                            .  .  .     790 

Sugar  584 
action    of   dilute    acids 

Tantalite  432 
Tantalum                432 

Tolu  balsam  790 

Toluene      495 

T'ipioca                                   592 

Toluidine                   496 

action  of  alkalies  upon.  586 
candy                                  589 

Tartar     674 

Toluylic  alcohol  549 

Tonka   bean  .-..  €94 

Sugar,  copper  test  for  the 

emetic  675 
Tartaric  acid  673 

Trachyte  336 
Trade  winds  52 

from  diabetes  575 
Sugar  from  starch  or  dex- 
trin                                 575 

Tartaric  ethers                       676 

Transmission  of  heat  302 
Transpiration  of  gases  139 
Travertin                                229 

Tartrates,  metallic  674 
T-mrin                                     597 

Teeth                                       819 

Triacetin  611 

from  ergot  of  rye  587 
of  lead   609 

Tellurethyl  771 
Tellurhydric  acid  207 
Telluric  acid                    ..     207 

Triads                                      231 

Triamines  743 

of  milk         587 

Triatomic     alcohols    and 
ethers                          ..  565 

Tellui'ides                                289 

Sugar-forming  ferments  in 
saliva  801 
Sugars,  action  of,  on  polar- 
ized lifht                           575 

Telluromethyl                        771 

Tellurous   acid                       206 

Triamylamine           739 

Ten-carbon  phenols  565 
Tension  of  vapors  63 
Terbium                    .              242 

Tribasic  acids  284,  669,  678 

Sulphamic  acid    314 

Trichloroquinone  680 
Trichlorophenol  552 
Tridecane                                477 

Sulphanisolic  acid  551 
Sulphantimonates     ..           490 

Terebene  489 

Terpenes  488 
Terpentin-hydrate                490 

Sulphantimonites  420 
Sulpharsenates  424 
Sulpharsenites  424 
Sulphione  24" 
Sulphisathyde                       784 

Triethene  alcohol    561 

Terpin                                     4QO 

Triethene-triamine  744 
Triethylamino  736 
Triethylarsine  762 
Triethylbismuthine  767 
Triethyl  -  diethene  -  diam- 
monium  iodide  744 

Terpin-hydrate  490 
Terpinol  490 
Tertiary  butyl  alcohol  534 
hexyl  alcohol  540 
Tetrachloroquinone  680 
Tetrads  .  .                              231 

Sulphites  196 

Sulpho-acids  682 
Sulphobenzide  483 

Sulphocarbonic  ethers  650 
Sulphocyanates,  metallic..  717 
Sulphocyanic  ethers  718 
Sulphomolybdates  445 
Sulphophosphatefl  218 

Tetramethyl  -  ammonium 
hydrate  738 
Tetrammonio  -  platinic 
compounds                         377 

Triethylrosaniline  747 
Triethylstibine         761 

Triethyl  sulphurous  com- 
pounds                           .  .  530 

Tetrammonio  -  platinous 
compounds  376 
Tetramylammonium     hy- 
drate                       739 

Sulphotungstates  443 
Bnlphovinatea  526 

Tri<nntene          480 

Triglucosic   alcohol  583 
Tri'mercurodiamine  363 
Trimethylcarbinol  534 
Trimethylphosphine  761 

Sulphur  193 

allotropic  modifications 
of  194 

Tetrathionie  acid  

Tetrethylammonium    hy- 
drate    737 

auratum  420 

INDEX. 


857 


PAGE 

Trinitrocellulose  694 

PAGE 
Vapor-densities,   anomal  - 
ous  .  .                                   460 

Weights:                             PAGE 

Trinitrophenol  552 

Tnphen.vlamine   742 

Vapors,  determination  of 
the  density  of  459 
theoretical  density  of...  229 
maximum  density  of.....     6-1 

Whey  587 

Tiiphenylrosaniline  747 
Tripliylline  316 

White  of  egg  794 

Will     and     Varrentrapp's 
method    of    estimating 
nitrogen  455 

Tri-tearin    625 

Tritliionic  acid  199 
Trivalent  elements  231 

Varec  189 
Variolaria  785 

Winds                                        52 

Trona                               .          303 

Tube-atmolyser  138 

Vegetable  nutrition  824 

clarifying  of                      802 

Wire-drawing  268 

Turkey  red     788 

Venice  turpentine   790 

Turmeric  789 

Venous  blood  805 

Wolfram                                  440 

Tnrnhull's   blue      709 

Ventilation  ...         53 

Turpentine  488 

Veratrine  or  Veratria  75(3 
Ve.ratrol                                   564 

livilrated  oil  of  489 

Wood-spirit                            512 

oil  of  488 

Verdi  "ris    609 

Turpith  or  Turbeth,  min- 
eral     361 

-Verdi  ter  355 

Wootz  404 

Vermilion          361 

Wort  519 

Twaddell's  hydrometer....  828 
Type,  ammonia  ..315,  470,  733 
Typ;',  hydrochloric  acid...  373 
Type,  marsh-gas...464,  510,  598 
734 
Type-metal  511 

Vinous  fermentation  518 
Vinyl  alcohol...             486,  543 

X. 

Violantin                                 731 

Vitriol   blue  355 

green                .                  400 

oil  of                                    196 

Type,  water          ..        278    596 

white                                    351 

Xanthic  acid  and  ethers...  651 
Xanthic   oxide                       757 

Volatile  oils   in  general...  492 
isomeric  with  oil  of  tur- 
pentine                            491 

Tyrosiue  787 

Xanthine                                758 

U. 

TJImin                                    585 

Xanthorhamnin  583 
Xylene  497 

Volatility  of  metals  269 
Volume,  combination  by...  228 
specific                                 2''9 

Xylo'idin                        .         593 

Voltaic  battery             1°0    250 

Xylyl   i'lcohol                        549 

Ultimate  analysis   of   or- 
ganic bodies                       448 

pile,  chemistry  of  the...  245 
Voltameter                              249 

Xylylic  phenols  553 

Y. 
yeast      520 

Ultramarine  309 

Volta'spile  121 

Undecane    ....          ..            457 

W. 

Wash    distiller's                   520 

Uramile                                   7;'>0 

Uramilicacid  ..          ..      ..  7-'!0 

Uranates                                 415 

Yellow  dyes                          789 

Uranium  414 

Yttria  343 

Uranium-salts,  reaction  of  416 
Uranite                                   414 

Water                                       143 

Yttrium              .                     242 

Yttro-tantalite                      432 

Untes                                     724 

distilled                                 146 

Z. 

7'\ffre                                     409 

Urea                                713    721 

expansion  of,  by  heat...     48 

of  crystallization  147 
maximum  density  of....     50 
not  an   electrolyte  248 
oxygenated  153 
solvent  properties  of.....  147 

Uric  acid                                 723 

Zeolites  337 
7inc                       .         .         350 

Urinary  calculi                      809 

Urine                                       807 

alloys                                   352 

analysis  of              808 

in  disease                            808 

tension   of  vapor  of  63 
tvpe                             278    596 

coloring  matter  of  809 

chloride          .                     351 

sea-,  analysis  of  146 
spring  and  river-,  analy- 
ses of                       834    835 

j'irtate     648 

V. 

Valerian  oil   of              .  ..  492 

oxide                                ...  351 

Waters,  mineral,  analyses 
of  s:;2.  s:;:; 
Water-vapor,  composition 
of,  by  volume  146 

sulplnte                              351 

sulphide     351 

-ethyl  or/inoethide  768 
-methyl  or  /inc-methide  769 
-oxyl  337 
-salts,  reactions  of  352 
Zircon  338 
Zirconia  338 

Valeric  or  valerianic  acid.  617 
Valeric  ethers  tiitf 

W-i\                                542    6°5 

fossil  507 
Weights  and  measures  836 
comparison    of   French 
and  English  837,  838 
Weights    atomic  2"2 

Yaleronitrile  710 

V'llervlene                              487 

V'llylene                                   4ss 

Zirconium    338 

-salts,  reactions  of.  343 

Vanor  of  water,  tension  of     63 

table  of....                  ...  226 

BRANDE  AND  TAYLOR'S  CHEMISTRY, 

NEW  EDITION,  JUST  ISSUED. 


CHEMISTRY 


WILLIAM   THOMAS   BRANDE,  D.  C.  L.,  &c., 

AND 

ALFRED  SWAINE  TAYLOR,  M.  D.,  F.  R.  S., 

Professor  of   Chemistry  and   Medical  Jurisprudence  in  Guy's   Hospital,   London. 

Second  American  Edition,  thoroughly  revised  by  Dr.  Taylor.    In  one  large  octavo  volume  of  764 
closely  printed  pages  ;  extra  cloth,  $5  ;  leather,  $6. 

We  do  not  hesitate  to  pronounce  this  the  ablest  work  on  chemistry  in  the  English  language. 
Iowa  Med.  Journal,  April,  1868. 

The  recognized  value  of  this  treatise,  and  its  reputation  both  here  and  abroad,  render  it 
unnecessary  for  us  to  more  than  call  attention  to  this  new  edition,  which  the  American  pub- 
lisher has  brought  out  with  great  care  and  accuracy,  the  supervision  of  the  work,  as  it  passed 
through  the  press,  being  intrusted  to  a  competent  chemist.  —  New  York  Medical  Journal, 
March,  1868. 

An  eminently  practical  and  truly  admirable  work.  —  Leavenworth  Med.  Herald,  Nov.  5867. 

One  of  the  most  useful  and  complete  in  the  language.  It  has  been  already  announced  offi- 
cially as  the  text-book  in  one  of  our  medical  colleges,  and  we  expect  other  schools  to  follow. — 
St.  Louis  Med.  and  Surg.  Journal,  Dec.  1867. 

This  is  an  elegant  volume  of  nearly  eight  hundred  pages,  and  as  a  manual  for  students  seems 
all  that  could  be  desired.  It  is  full  without  being  lengthy,  minute  without  being  wearisome, 
and  written  in  a  manner  calculated  to  attract.  It  is  a  first-class  book  for  students,  and  as  such 
we  confidently  recommend  it  to  them.  Those  who  may  desire  to  purchase  it  may  be  sure  of 
having  in  it  all  the  latest  chemical  knowledge.— Canada  Med.  Journal,  Nov.  1867. 

The  one  before  us,  which  is  the  joint  labor  of  two  of  the  greatest  minds  in  Great  Britain, 
can  most  certainly  demand  for  itself  the  highest  rank  in  the  special  department  of  which  it 
treats.  Although  a  work  of  large  size,  being  an  octavo  of  over  seven  hundred  pages,  it  is  filled 
with  such  subjects  as  arc  useful  to  the  student  of  every-day  chemistry,  or  to  the  practical  man 
who  measures  the  utility  of  every  scientific  fact  in  proportion  to  its  capability  of  being  demon- 
strated. In  other  words,  it  is  calculated  in  our  opinion  to  give  to  the  medical  man  the  broadest 
possible  groundwork  for  the  study  of  chemisty,  and  the  application  of  its  great  truths  to  the 
every-day  necessities  of  practical  life.  Nothing  more  is  attempted,  and  nothing  more  is  needed, 
in  a  work  specially  designed  for  medical  practitioners  and  students. — N.  Y.  Medical  Record, 
'  Nov.  15, 1867. 

One  of  the  standard  works  on  chemistry;  alike  valuable  for  the  student  and  for  reference  by 
the  practitioner ;  well  up  to  the  times,  containing  the  latest  discoveries.  —  Detroit  Review  of 
Medicine  and  Pharmacy,  Dec.  1867. 

Any  full  or  critical  notice  of  such  a  work,  in  this  place,  would  seem  to  be  uncalled  for.  To 
the  careful  student,  who  desires  a  full  and  complete  text-book  in  this  department  of  study,  we 
commend  the  volume  before  us.  —  Cincinnati  Lancet  and  Observer,  Nov.  1867. 

A  work  of  real  merit,  such  as  every  student  and  practitioner  will  find  useful,  both  for  study 
and  reference.  —  Chicago  Medical  Examiner,  Oct.  1867. 

The  pervading  idea  is  to  afford  such  information  on  chemistry  as  will  be  of  most  advantage 
to  the  student  who  cannot  devote  his  whole  time  to  the  study.  The  foundation  is  laid  in  this 
work  for  a  deeper  research,  if  time  and  inclination  permit.  Altogether  it  is  a  very  valuable 
text-book  for  the  student  of  medicine,  and  may  well  be  adopted  by  every  medical  college;  the 
constant  reference  which  the  physician  must  make  to  this  science  will  render  the  work  abso- 
lutely necessary  on  his  shelves.—  St.  Louis  Medical  Reporter,  Nov.  1, 1867. 

The  author  appears  to  have  extended  his  care  to  all  portions  of  the  work,  organic  and  inor- 
ganic. Among  the  former,  additions  will  be  found  at  chloroform,  nitro-glycerine,  anilin  colors, 
valerianates,  spectrum  analysis,  and  other  subjects  have  also  been  enlarged,  so  that  the  claims 
of  the  book  presented  to  the  student  are  strong  and  decided,  as  being  up  to  the  present  time, 
and  meriting  his  confidence.  —  Am.  Journal  of  Pharmacy,  Nov.  1867. 

(lives,  in  the  clearest  and  most  summary  method  possible,  all  the  facts  and  doctrines  of  chem- 
istry, with  more  especial  reference  to  the  wants  of  the  medical  student.—  London  Medical 
Times. 

HENRY  C.  LEA,  Philadelphia 


GRAHAM'S    CHEMISTRY. 

THE    ELEMENTS    OP    CHEMISTRY, 

INCLUDING   THE  APPLICATIONS  OF  THE   SCIENCE  TO    THE   ARTS. 
BY  THOMAS  GRAHAM,  F.  K.  S. 

Second  American,  from  the  Second  Revised  and  Enlarged  English  Edition. 
EDITED  BY    HENRY    WATTS,    F.  C.  S.,    AND    ROBERT    BRIDGES,    M.  D. 

With  Two  Hundred  and  Thirty-three  Illustrations  on  Wood. 
Complete  in  one  volume,  large  octavo,  of  850  closely  printed  pages,  extra  cloth,  $5.50.     Containing 

the  whole  of  the  two  -volumes  of  the  London  edition. 

The  publishers  have  gotten  up  the  work  in  their  usually  excellent  style;  the  wood  en  grav- 
ing are  bountifully  executed,  and  altogether  the  chemical  student  or  physician  will  find 
nothing  better  or  so  good,  as  a  standard  and  complete  text-book,  as  this  new  edition  of  Graham. 
—  Cincinnati  Lancet. 

We  have  always  regarded  Graham's  Chemistry  as  one  of  the  best  standard  works  upon  the 
important  department  of  science  to  which  it  is  directed,  and  its  merits  we  believe  are  so  gen- 
erally admitted  that  any  lengthened  commendation  from  us  becomes  unnecessary.  Suffice  it, 
then,  to  observe  that  we  know  of  no  more  reliable  authority  to  which  reference  can  be  made 
than' the  text  of  this  valuable  work,  nor  of  any  better  adapted  to  the  general  purposes  of  the 
student  in  search  of  sound  and  profitable  intelligence.  Of  the  totality  it  may  be  curtly  ob- 
served  it  is  everywhere  good,  and  the  descriptions  are  as  intelligible  as  they  are  comprehen- 
sive. —  Montreal  Med.  Chronicle.  • 

The  very  best  work  on  Inorganic  Chemistry  extant,  and  published  in  the  best  style.  —  N.  0. 
Med.  News  and  Hosp.  Gazette.  

BOWMAN'S  PRACTICAL   CHEMISTRY. 

INTRODUCTION  TO  PRACTICAL  CHEMISTRY— Including  Analysis. 
BY  JOHN  E.  BOWMAN,  M.  D. 

EDITED  BY  C.  L.  BLOXAM,  Professor  of  Practical  Chemistry  in  King's  College,  London. 

Fourth  American,  from  the  Fifth  and  Revised  English  Edition.    In  one  handsome  royal  I2mo. 

volume,  with  numerous  illustrations  ;  extra  cloth,  $2.25. 

The  works  of  the  late  Professor  Bowman,  on  Chemistry,  have  long  and  deservedly  held  a 
prominent  place  in  our  scientific  literature,  and,  if  there  be  any  one  reason  for  this  more 
marked  than  another,  we  should  say  it  is  because  of  their  combined  conciseness  with  correct- 
ness. Not  a  superfluous  word  is  employed,  and  much  space  is  thus  saved  that  in  many  authors 
is  wasted  in  vague  generalities  and  confusing  theoretical  discussions,  that  bewilder  rather  than 
enlighten  the  student.  This  edition,  which  is  prepared  by  Professor  Bowman's  successor  at 
King's  College,  is  quite  up  to  the  advances  that  are  constantly  making  in  this  progressive 
science.  —  N.  Y.  Medical  Journal. 

It  will  be  found  one  of  the  best  guides  for  the  student  of  practical  chemistry,  and  a  very 
convenient  manual  for  reference  by  the  profession  generally.  —  Chicago  Med.  Examiner. 


BOWMAN'S  MEDICAL  CHEMISTRY. 

PRACTICAL   HANDBOOK   OF  MEDICAL     CHEMISTRY. 

BY  JOHN  E.  BOWMAN,  F.  C.  S., 

Formerly  Professor  of  Practical   Chemistry  in  King's  College,  London. 

EDITED  BY  CHARLES  L.  BLOXAM, 

Professor  of  Practical  Chemistry  in  King's  College,  London. 

Fourth  American,  from  the  Fourth  and  Revised  London  Edition;  with  numerous  illustrations. 

In  one  neat  royal  I2mo.  volume  of  351  pages;  extra  cloth,  $2.25. 

Bowman's  Handbook  of  Medical  Chemistry  has  been  so  well  appreciated  by  the  medical 
public,  that  any  extended  notice  of  a  new  edition  would  be  unnecessary  were  it  not  for  the 
appearance  of  another  name  on  the  title-page,  and  the  extensive  alterations  and  additions  which 
have  been  made.  The  student  and  practitioner  have  here  offered  to  them  a  book  which  will  be 
found  very  useful,  as  a  guide  and  aid  in  the  application  of  modern  chemistry  and  microscopic 
analysis  to  medical  science,  the  importance  of  which  will  be  more  and  more  appreciated,  as  phy- 
sicians avail  themselves  of  the  means  which  are  thus  offered. — Am.  Journal  of  Med.  Sciences. 
Few  students  of  medicine,  we  suppose,  are  without  a  copy  of  one  or  other  editions  of  this 
valuable  and  handy  work,  and  possibly  there  are  but  few  of  our  younger  fellow-practitioners 
who  do  not  find  it  still  a  useful  book  for  reference.  On  this  supposition  it  can  hardly  be  neces- 
sary for  us  to  offer  any  criticism  on  its  merits.— British  and  Foreign  Medico- Chirurgical  Review, 


HENEY  0.  LEA,  Philadelphia, 


CATALOGUE  OF  BOOKS 

PUBLISHED  BY 

o. 

(LATE  LEA  &  BLANCHARD.) 


The  books  in  the  annexed  list  will  be  sent  by  mail,  post-paid,  to  any 
Post  Office  in  the  United  States,  on  receipt  of  the  printed  prices.  No 
risks  of  the  mail,  however,  are  assumed,  either  on  money  or  books.  Gen- 
tlemen will  therefore,  in  most  cases,  find  it  more  convenient  to  deal  with 
the  nearest  bookseller. 

Detailed  catalogues  furnished  or  sent  free  by  mail  on  application.  An 
illustrated  catalogue  of  64  octavo  pages,  handsomely  printed,  mailed  on 
receipt  of  10  cents.  Address, 

HENRY  C.  LEA, 
Nos.  706  and  708  Sansom  Street,  Philadelphia. 


A  MERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES. ")     p      fi 

-"•    Edited  by  Isaac  Hays,  M.D.,  published  quarterly,  about  j  ^    ° 

1100  large  8vo.  pages  per  annum, 

MEDICAL  NEWS  AND  LIBRARY,  monthly,  384  large     .    nr 
8vo.  pages  per  annum,  j  1D 

OR, 

A  MERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES,  1 
•"•     Quarterly, 


For  six 
Dollars  per 


MEDICAL  NEWS  AND  LIBRARY,  monthly, 
RANKING' S    HALF-YEARLY    ABSTRACT    OF    THE 
MEDICAL  SCIENCES.     2  vols.  a  year,  of  about  300 
pages  each. 

In  all,  over  2000  large  8vo.  pages  per  annum, 
ABSTRACT,  RANKING'S  HALF-YEARLY,   per  volume,  $150;  per 
•"•     annum,  $2  50. 

ALLEN  (J.M.)  THE  PRACTICAL  ANATOMIST;  or,  THE  STUDENT'S 
-*••*•    GUIDE  IN  THE  DISSECTING  ROOM.     With  266  illustrations.     1  vol. 
royal  12mo.,  over  600  pages,  cloth,  $2. 

ASHTON  (T.  J.)  ON  THE  DISEASES,  INJURIES,  AND  MALFOR- 
MATIONS OF  THE  RECTUM  AND  ANUS.  With  remarks  on 
Habitual  Constipation.  Second  American  from  the  fourth  London 
edition,  with  illustrations.  1  vol.  8vo.  of  about  300  pp.,  cloth,  $3  25. 

ABEL  AND  BLOXAM'S  HANDBOOK  OF  CHEMISTRY,  THEORE- 
TICAL, PRACTICAL,  AND  TECHNICAL.  With  illustrations.  1 
vol.  8vo.  of  662  pages,  cloth,  $4  50. 

ARNOTT  (NEIL).  ELEMENTS  OF  PHYSICS  ;  or,  NATURAL  PHILO- 
SOPHY, GENERAL  AND  MEDICAL.  1  vol.  8vo.,  with  illustrations, 
cloth,  $2  25. 

ASHWELL  (SAMUEL).    A  PRACTICAL  TREATISE  ON  THE  DIS- 
-tl    EASES  OF  WOMEN.     Third  American  from  the  third  London  edi- 
tion.    In  one  8vo.  vol.  of  528  pages,  cloth,  $3  50. 
BRINTON  (WILLIAM).    LECTURES  ON  THE  DISEASES  OF  THE 
STOMACH  ;  with  an  introduction  on  its  Anatomy  and  Physiology. 
From  the  second  London  edition,  with  illustrations.     1  vol.  8vo.  of 
about  300  pages,  cloth,  $3  25. 

-DRANDE    (WM.   T.),    AND   ALFRED   S.   TAYLOR.     CHEMISTRY. 

•D     Second  American  edition,  thoroughly  revised  by  Dr.    Taylor.     In 

one  large  and  handsome  octavo  volume,  extra  cloth,  $5  ;  leather,  $6. 


HENRY  C.  LEA'S  PUBLICATIONS. 


BTJMSTEAD  (F.  J.)  THE  PATHOLOGY  AND  TREATMENT  OF 
VENEREAL  DISEASES.  Including  the  results  of  recent  investi- 
gations upon  the  subject.  A  new  and  revised  edition,  with  illustra- 
tions. 1  vol.  8vo.,  of  640  pages,  cloth,  $5. 

AND  CULLERIER'S  ATLAS  OF  VENEREAL.    See  'CTJLLERIER.' 

-DUCKNILL   (J.   C.)   AND   DANIEL   M.   TUKE.      A    MANUAL   OF 
-D     PSYCHOLOGICAL   MEDICINE.      Containing   the   History,  Nos- 
ology, Description,  Statistics,  Diagnosis,  Pathology,  and  Treatment 
of  Insanity.    With  a  Plate.     1  vol.  8vo.,  of  536  pages,  cloth,  $4  25. 
•QARCLAY  (A..  W.)  A  MANUAL  OF  MEDICAL  DIAGNOSIS;  being 
•D     an  Analysis  of  the  Signs  and  Symptoms  of  Disease.    Third  American 
from  the  second  revised  London  edition.     1  vol.  8vo.,  of  451  pages, 
cloth,  $3  50. 

BENNET  (HENRY).  A  PRACTICAL  TREATISE  ON  INFLAMMA- 
TION OF  THE  UTERUS,  ITS  CERVIX  AND  APPENDAGES, 
AND  ON  ITS  CONNECTION  WITH  UTERINE  DISEASE.  Sixth 
American,  from  the  fourth  and  revised  English  edition.  1  vol.  8vo., 
of  about  500  pages,  cloth,  $3  75. 

.  A  REVIEW  OF  THE  PRESENT  STATE  OF  UTERINE  PA- 
THOLOGY.    1  small  vol.  8vo.,  cloth,  50  cents. 

"DABLOW    (GEORGE    H.)     A    MANUAL   OF    THE    PRACTICE    OF 
-D     MEDICINE.     With  additions  by  D.  F.  Condie,  M.D.     1  vol.  8vo., 
of  over  600  pages,  cloth,  $2  50. 

BUOWN  (ISAAC  BAKER).  ON  SOME  DISEASES  OF  WOMEN 
ADMITTING  OF  SURGICAL  TREATMENT.  With  illustrations. 
1  vol.  8vo.,  of  276  pages,  cloth,  $1  60. 

BROWNE  (R.  W.)  A  HISTORY  OF  GREEK  CLASSICAL  LITERA- 
TURE. Second  American,  from  a  revised  English  edition.  1  vol. 
crown  8vo.,  of  about  500  pages,  cloth,  $1  90. 

A  HISTORY  OF  ROMAN  CLASSICAL  LITERATURE.    Second 

American,  from  a  revised  English  edition.  1  vol.  crown  8vo.,  of 
about  500  pages,  cloth,  $1  90. 

BAIRD  (ROBERT).  IMPRESSIONS  AND  EXPERIENCES  OF  THE 
WEST  INDIES  AND  UNITED  STATES.  1  vol.  royal  12mo.,  cloth, 
75  cents. 

TDUDD  (GEORGE).    ON  DISEASES  OF  THE  LIVER.    Third  American, 

•D     from  the  third  and  enlarged  London  edition.       With  four  colored 

plates  and  numerous  wood-cuts.     1  vol.  8vo.,  of  500  pages,  cloth,  $4. 

BUCKLER  (THOMAS  H.)  ON  FIBRO-BRONCHITIS  AND  RHEU- 
MATIC PNEUMONIA.  1  vol.  8vo.,  of  150  pages,  cloth,  $1  25. 
BOWMAN  (JOHN  E.)  A  PRACTICAL  HAND-BOOK  OF  MEDICAL 
CHEMISTRY.  Edited  by  C.  L.  Bloxam.  Fourth  American,  from 
the  fourth  and  revised  London  edition.  With  numerous  illustra- 
tions. 1  vol.  royal  12mo.  of  350  pages,  cloth,  $2  25. 

INTRODUCTION  TO  PRACTICAL  CHEMISTRY,  INCLUDING 

ANALYSIS.  Edited  by  C.  L.  Bloxam.  Fourth  American,  from 
the  fifth  and  revised  London  edition,  with  numerous  illustrations. 
1  vol.  royal  12mo.  of  350  pages,  cloth,  $2  25. 

-RRODIE  (SIR  BENJAMIN) .     CLINICAL  LECTURES  ON  SURGERY. 
-D     l  vol.  8vo.,  of  350  pages,  cloth,  $1  25. 

flHAMBERS  (T.  K.)     THE  INDIGESTIONS ;  OR,  DISEASES  OF  THE 
V     DIGESTIVE    ORGANS    FUNCTIONALLY    TREATED.       Second 
American,  from  the  second  and  enlarged  London  edition.      1  vol. 
8vo.,  of  over  300  pages,  cloth,  $3  00. 

paiOMBAT  DE  L'ISERE.     THE  DISEASES  OF  FEMALES.     Trans- 
^     lated  by  Charles  D.  Meigs,   M.D.     Second  edition,  with  numerous 
illustrations.     1  vol.  8vo.,  of  720  pages,  cloth,  $3  75. 


HENRY  C.  LEA'S  PUBLICATIONS. 


pARPENTER  (WM.  B.)     PRINCIPLES  OF  HUMAN  PHYSIOLOGY, 

U  WITH  THEIR  CHIEF  APPLICATIONS  TO  PSYCHOLOGY,  PA- 
THOLOGY, THERAPEUTICS,  HYGIENE,  AND  FORENSIC 
MEDICINE.  A  new  American  edition  edited  by  Francis  G.  Smith, 
M.D.  With  nearly  300  illustrations.  In  one  large  vol.  8vo.,  of 
nearly  900  closely  printed  pages,  cloth,  $5  50 ;  leather,  raised 
bands,  $6  50. 

PRINCIPLES  OF  COMPARATIVE  PHYSIOLOGY.  New  Ameri- 
can, from  the  fourth  and  revised  London  edition.  With  over  300 
beautiful  illustrations.  1  vol.  8vo.,  of  752  pages,  cloth,  $5  00. 

THE  MICROSCOPE  AND  ITS  REVELATIONS.  With  an  Appen- 
dix containing  the  applications  of  the  Microscope  to  Clinical  Medi- 
cine, by  Francis  G.  Smith,  M.D.  With  434  handsome  illustrations. 
1  vol.  8vo.,  of  724  pages,  cloth,  $5  25. 

PRIZE  ESSAY  ON  THE  USE  OF  ALCOHOLIC  LIQUORS  IN 

HEALTH  AND  DISEASE.     New  edition,  with  a  Preface  by  D.  F. 
Condie,  M.D.     1  vol.  I2mo.  of  178  pages,  cloth,  60  cents. 

PARSON  (JOSEPH)  .   A  SYNOPSIS  OF  THE  COURSE  OF  LECTURES 

v  ON  MATERIA  MEDICA  AND  PHARMACY,  delivered  in  the  Uni- 
versity of  Pennsylvania.  Fourth  and  revised  edition.  1  vol.  8vo. , 
extra  cloth,  $3  00.  (Just  issiied.) 

PHRISTISON  (ROBERT.)  DISPENSATORY  OR  COMMENTARY  ON 
V   THE  PHARMACOPOEIAS  OF  GREAT  BRITAIN  AND  THE 

UNITED  STATES.  With  a  Supplement  by  R.  E.  Griffith.  In  one 
8vo.  vol.  of  over  1000  pages,  containing  213  illustrations,  extra 
cloth,  $4  00. 

pHURCHILL  (FLEETWOOD).    ON  THE  THEORY  AND  PRACTICE 
U     OF  MIDWIFERY.     A  new  American  from  the  fourth  revised  Lon- 
don edition.     With  notes  and  additions  by  D.  Francis  Condie,  M.D. 
With  about  200  illustrations.     In  one  handsome  8vo.  vol.  of  nearly 
700  pages,  extra  cloth,  $4  00  ;  leather,  $5  00. 

ON  THE  DISEASES  OF  WOMEN  :  INCLUDING  THOSE  OF 

PREGNANCY   AND    CHILDBED.     A   new   American  edition   re- 
vised by  the  author.     With  notes  and  additions  by  D.  Francis  Condie, 
M.D.     In   one   large   and    handsome  8vo.   vol.    of  768  pages,   with 
numerous  illustrations,  extra  cloth,  $4  00  ;  leather,  $5  00. 

ESSAYS  ON  THE  PUERPERAL  FEVER,  AND  OTHER  DIS- 
EASES PECULIAR  TO  WOMEN.  In  one  neat  octavo  vol.  of  about 
450  pages,  extra  cloth,  $2  50. 

HLYMER  ON  FEVERS.     In  one  8vo.  vol.  of  600  pages,  leather,  $1  75. 

CONDIE  (D.  FRANCIS).  A  PRACTICAL  TREATISE  ON  THE  DIS- 
EASES OF  CHILDREN.  Sixth  edition,  revised  and  enlarged.  In 
one  large  octavo  volume  of  nearly  800  pages,  extra  cloth,  $5  25  ; 
leather,  $6  25.  (Just  issued  ) 

PROPER  (B.  B.)     LECTURES  ON  THE  PRINCIPLES  AND  PRAC- 
v*     TICE  OF  SURGERY.     In  one  large  8vo.  vol.  of  750  pages,  extra 

cloth,  $2  00. 

PURLING   (T.  B.)     A  PRACTICAL  TREATISE  ON  DISEASES  OF 
V     THE  TESTIS,  SPERMATIC  CORD,  AND  SCROTUM.     1  vol.  8vo. 

of  420  pages,  extra  cloth,  $2  00. 

pULLERIER  (A.)     AN  ATLAS  OF  VENEREAL  DISEASES.     Trans- 
V-J     lated  and  edited  by  FREEMAN  J.  BUMSTEAD,  M.D.     A  large  imperial 
quarto  volume,  with  26  plates  containing  about  150  figures,  beauti- 
fully colored,  many  of  them  the  size  of  life.     In  five  parts,  price  per 
part,  $3  00. 

Same  Work,  complete  in  one  volume  4to.,  extra  cloth,  $17  00.   (Now 

ready.) 


HENRY  C.  LEA'S  PUBLICATIONS. 


CYCLOPEDIA  OF  PEACTICAL  MEDICINE.     By  Dunglison,  Forbes, 
\J     Tweedie,  and  Conolly.     In  four  large  super  royal  octavo  volumes,  of 

3254  double-columned  pages,  leather,  raised  bands,  $15  ;  extra  cloth, 

$11. 

CAMPBELL'S  LIVES  OF  LORDS  KENYON,  ELLENBOROUGH,  AND 
U     TENTERDEN.     Being  the  third  volume  of  "  Campbell's  Lives  of 

the  Chief  Justices  of  England."    In  one  crown  octavo  vol.,  cloth,  $2. 

D  ALTON  (J.  C.)  A  TREATISE  ON  HUMAN  PHYSIOLOGY.  Fourth 
edition,  revised,  with  nearly  300  illustrations  on  wood.  In  one  very 
handsome  octavo  volume  of  about  700  pages,  extra  cloth,  $5  25  ; 
leather,  $6  25. 

DE  JONGH,  ON  THE  THREE  KINDS  OF  COD-LIVER  OIL.  1  small 
12mo.  vol.,  75  cents. 

DEWEES  (W.  P.)  A  TREATISE  ON  THE  DISEASES  OF  FEMALES. 
With  illustrations.  In  one  8vo.  vol.  of  536  pages,  extra  cloth,  $3. 

-  A   COMPREHENSIVE    SYSTEM   OF   MIDWIFERY.      In   one 
octavo  volume  of  600  pages,  with  plates,  extra  cloth,  $3  50. 

--  A  TREATISE  ON  THE  PHYSICAL  AND  MEDICAL  TREAT- 
MENT OF  CHILDREN.  In  one  octavo  volume  of  548  pages,  extra 
cloth,  $2  80. 

DICKSON  (S.  H.)  ELEMENTS  OF  MEDICINE.  Second  edition,  re- 
vised. 1  vol.  8vo.,  of  750  pages,  extra  cloth,  $4. 

DRUITT  (ROBERT).  THE  PRINCIPLES  AND  PRACTICE  OF  MO- 
DERN SURGERY.  A  revised  American,  from  the  eighth  London 
edition.  Illustrated  with  432  wood  engravings.  In  one  handsome 
8vo.  vol.  of  nearly  700  large  and  closely  printed  pages,  extra 
cloth,  $4  ;  leather,  $5. 

TJUNGLISON  (ROBLEY).  MEDICAL  LEXICON;  a  Dictionary  of 
-L'  Medical  Science.  Containing  a  concise  explanation  of  the  various 
subjects  and  terms  of  Anatomy,  Physiology,  Pathology,  Hygiene, 
Therapeutics,  Pharmacology,  Pharmacy,  Surgery,  Obstetrics,  Medical 
Jurisprudence,  and  Dentistry.  Notices  of  Climate  and  of  Mineral 
Waters  ;  Formulae  for  Officinal,  Empirical,  and  Dietetic  Preparations, 
with  the  accentuation  and  Etymology  of  the  Terms,  and  the  French 
and  other  Synonymes  ;  so  as  to  constitute  a  French  as  well  as  English 
Medical  Lexicon.  In  one  very  large  royal  8vo.  vol.  of  1048  double 
columned  pages,  in  small  type  ;  strongly  bound  in  cloth,  $6  ;  leather, 
raised  bands,  $6  75. 

-  HUMAN  PHYSIOLOGY.     Eighth   edition,  thoroughly  revised. 
In  two  large  8vo.  vols.  of  about  1500  pages,  with  532  illustrations, 
extra  cloth,  $7. 

-  NEW  REMEDIES,  WITH  FORMULA  FOR  THEIR  PREPARA- 
TION AND  ADMINISTRATION.     Seventh  edition.     In  one  very 
large  8vo.  vol.  of  770  pages,  extra  cloth,  $4. 

DE  LA  BACHE'S  GEOLOGICAL  OBSERVER.  In  one  large  8vo.  vol. 
of  700  pages,  with  300  illustrations,  cloth,  $4. 

ON  QUIXOTE  DE  LA  MANCHA.  Translated  by  Chas.  Jarvis,  Esq., 
with  illustrations  by  Tony  Johannot.  In  two  handsome  vols.  crown 
8vo.,  fancy  cloth,  $3;  plain  cloth,  $2  50;  library  sheep,  $3  20; 
half  morocco,  $3  70. 

(JAMES  D.)  THE  STRUCTURE  AND  CLASSIFICATION  OF 
ZOOPHYTES.  With  illustrations  on  wood.  In  one  imperial  4to.  vol., 
cloth,  $4  00. 

(BENJAMIN).  THE  MEDICAL  FORMULARY.  Being  a 
collection  of  prescriptions  derived  from  the  writings  and  practice  of 
the  most  eminent  physicians  of  America  and  Europe.  Twelfth  edi- 
tion, carefully  revised  by  A.  H.  SMITH,  M.  D.  In  one  8vo.  volume 
of  374  pages,  extra  cloth,  $3.  (Now  ready.) 


T) 
•*-' 


HENRY  C.  LEA'S  PUBLICATIONS. 


ERICHSEN  (JOHN).  THE  SCIENCE  AND  ART  OF  SURGERY. 
A  new  and  improved  American,  from  the  second  enlarged  and  re- 
vised London  edition.  Illustrated  with  over  400  engravings  on 
wood.  In  one  large  8vo.  vol.  of  1000  closely  printed  pages,  extra 
cloth,  $6  ;  leather,  raised  bands,  $7. 

ON  RAILWAY  AND  OTHER  INJURIES  OF  THE  NERVOUS 

SYSTEM.     In  one  small  8vo.  vol.,  extra  cloth,  $]. 

•pNCYCLOFElDIA   AMERICANA.     Complete  in   14   large  8vo.   vols. 
•L      Containing  nearly  9000  double  columned  pages,  cloth,  $22. 

ENCYCLOPAEDIA  OF  GEOGRAPHY.     In  three  large  8vo.  vols.     Illus- 
trated with  83  maps  and  about  1100  wood-cuts,  cloth,  $5. 
•PISKE  FUND  PRIZE  ESSAYS  ON  TUBERCULOUS  DISEASE.     In 
•^      one  small  8vo.  vol.,  cloth,  $1. 

PLINT    (AUSTIN).     A    TREATISE    ON    THE    PRINCIPLES    AND 
•£     PRACTICE  OF  MEDICINE.     Third  edition,  thoroughly  revised  and 
enlarged.     In  one  large  8vo.  volume  of  1002  pages,  extra  cloth,  $6  ; 
leather,  raised  bands,  $7.       (Now  ready.) 

A  PRACTICAL  TREATISE,  ON  THE  PHYSICAL  EXPLORA- 
TION OF  THE  CHEST,  AND  THE  DIAGNOSIS  OF  DISEASES 
AFFECTING  THE  RESPIRATORY  ORGANS.  Second  and  re. 
vised  edition.  One  8vo.  vol.  of  595  pages,  cloth,  $4  50.  (Just  issued.) 

A  PRACTICAL  TREATISE  ON  THE  DIAGNOSIS  AND  TREAT- 
MENT OF  DISEASES  OF  THE  HEART.  In  one  neat  8vo.  vol. 
of  nearly  500  pages,  extra  cloth,  $3  50. 

FOWNE  (GEORGE) .  A  MANUAL  OF  ELEMENTARY  CHEMISTRY. 
With  197  illustrations.  In  one  royal  12mo.  vol.  of  600  pages,  extra 
cloth,  $2  ;  leather,  $2  50. 

PULLER   (HENRY).     ON   DISEASES  OF  THE   LUNGS  AND  AIR 
•L      PASSAGES.     Their  Pathology,  Physical  Diagnosis,  Symptoms  and 
Treatment.     From   the  second  English   edition.     In   one   8vo.  vol. 
of  about  500  pages,  extra  cloth,  $3  50.      (Just  issued.) 

FLETCHER'S  NOTES  FROM  NINEVEH,  AND  TRAVELS  IN  MESO- 
POTAMIA, ASSYRIA,  AND  SYRIA.  In  one  12mo.  vol.,  cloth,  75cts. 
GARDNER'S  MEDICAL  CHEMISTRY.    In  one  12mo.  vol.  of  396  pages, 
cloth,  $1. 

GLUGE  (GOTTLIEB).  ATLAS  OF  PATHOLOGICAL  HISTOLOGY. 
Translated  by  Joseph  Leidy,  M.D.,  Professor  of  Anatomy  in  the 
University  of  Pennsylvania,  <fcc.  In  one  vol.  imperial  quarto,  with 
320  copper  plate  figures,  plain  and  colored,  extra  cloth,  $4. 

GRAHAM  (THOMAS) .  THE  ELEMENTS  OF  INORGANIC  CHEMIS- 
TRY, INCLUDING  THE  APPLICATION  OF  THE  SCIENCE  IN 
THE  ARTS.  A  new  and  enlarged  edition  by  H.  Watts  and  Robert 
Bridges,  M.D.  In  one  8vo.  vol.,  of  over  800  pages,  with  232  wood- 
cuts, extra  cloth,  $5  50. 

GIBSON'S  INSTITUTES  AND  PRACTICE  OF  SURGERY.    In  two  8vo 
vols.  of  about  1000  pages,  leather,  $6  50. 

GRAY  (HENRY).  ANATOMY,  DESCRIPTIVE  AND  SURGICAL. 
Second  American,  from  the  second  revised  London  edition.  In  one 
large  imperial  8vo.  vol.  of  over  800  pages,  with  388  large  and  elabo- 
rate engravings  on  wood.  Extra  cloth,  $6  ;  leather,  raised  bands,  $7. 
GRIFFITH  (ROBERT  E.)  A  UNIVERSAL  FORMULARY,  CON- 
TAINING THE  METHODS  OF  PREPARING  AND  ADMINISTER- 
ING OFFICINAL  AND  OTHER  MEDICINES.  In  one  large  8vo. 
vol.  of  650  pages,  double  columns,  extra  cloth,  $4 ;  leather,  $5. 

GTJIZDT'S  HISTORY  OF  OLIVER  CROMWELL.  In  two  royal  12mo. 
vols.  Containing  900  pages,  cloth,  $2. 


6  HENRY  C.  LEA'S  PUBLICATIONS. 

GROSS  (SAMUEL  D.)  A  SYSTEM  OF  SURGERY,  PATHOLOGICAL, 
DIAGNOSTIC,  THERAPEUTIC,  AND  OPERATIVE.  Illustrated 
by  over  1300  engravings.  Fourth  edition,  revised  and  improved. 
In  two  large  royal  8vo.  vols.  of  2200  pages,  strongly  bound  in  leather, 
raised  bands,  $15. 

A  PRACTICAL  TREATISE  ON  THE  DISEASES,  INJURIES, 

AND  MALFORMATIONS  OF  THE  URINARY  BLADDER,  THE 
PROSTATE  GLAND,  AND  THE  URETHRA.  Second  edition, 
with  184  illustrations.  One  large  8vo.  vol.  of  over  900  pages, 
extra  cloth,  $4. 

A  PRACTICAL  TREATISE  ON  FOREIGN  BODIES  IN  THE 

AIR  PASSAGES.    In  one  8vo.  vol.  of  468  pages.     Extra  cloth,  $2  75. 

ELEMENTS  OF  PATHOLOGICAL  ANATOMY.     Third  edition. 

In  one  large  8vo.  vol.  of  nearly  800  pages,  with  about  350  illustra- 
tions, extra  cloth,  $4. 

HARTSHORNE  (HENRY).  ESSENTIALS  OF  THE  PRINCIPLES 
AND  PRACTICE  OF  MEDICINE.  Second  and  revised  edition.  In 
one  12mo.  vol.  of  about  450  pages,  cloth,  $2  38  ;  half  bound,  $2  63. 
(Now  ready.) 

TTARTSHORNE    (HENRY).      CONSPECTUS     OF     THE     MEDICAL 

•El  SCIENCES.  Comprising  Manuals  of  Anatomy,  Physiology,  Chemis- 
try, Materia  Medica,  Practice  of  Medicine,  Surgery,  and  Obstetrics. 
In  one  royal  12mo.  volume  of  over  1000  pages,  with  about  300  illus- 
trations. Strongly  bound  in  leather,  $5  25  ;  extra  cloth,  $4  50. 

MANUAL  OF  ANATOMY  AND  PHYSIOLOGY.    One  volume  royal 

12mo.,  cloth,  $1  75. 

TTABERSHON  (S.  0.)  PATHOLOGICAL  AND  PRACTICAL  OBSERVA- 

•EL  TIONS  ON  DISEASES  OF  THE  ALIMENTARY  CANAL,  OESO- 
PHAGUS, STOMACH,  CJECUM,  AND  INTESTINES.  In  one  8vo. 
vol.  of  312  pages,  extra  cloth,  $2  50. 

HUDSON  (A.)  LECTURES  ON  THE  STUDY  OF  FEVER.  1  vol. 
8vo.,  316  pages,  cloth,  $2  50.  (Now  ready.) 

HAMILTON  (FRANK  H.)  A  PRACTICAL  TREATISE  ON  FRAC- 
TURES AND  DISLOCATIONS.  Third  edition,  revised.  In  one 
handsome  8vo.  vol.  of  777  pages,  with  294  illustrations,  extra 
cloth,  $5  75. 

HARRISON'S  ESSAY  TOWARD  A  CORRECT  THEORY  OF  THE 
NERVOUS  SYSTEM.  In  one  vol.  8vo.  of  292  pages,  cloth,  $1  50. 
HOBLYN  (RICHARD  D.)  A  DICTIONARY  OF  THE  TERMS  USED 
IN  MEDICINE  AND  THE  COLLATERAL  SCIENCES.  In  one 
12mo.  vol.  of  over  500  double  columned  pages,  cloth.  $1  50; 
leather,  $2. 

HODGE  (HUGH  L.)  ON  DISEASES  PECULIAR  TO  WOMEN,  IN- 
CLUDING DISPLACEMENTS  OF  THE  UTERUS.  Second  arid 
revised  edition.  In  one  8vo.  volume,  cloth,  $4  50.  (J2ist  issued.) 
THE  PRINCIPLES  AND  PRACTICE  OF  OBSTETRICS.  Illus- 
trated with  large  lithographic  plates  containing  159  figures  from 
original  photographs,  and  with  numerous  wood-cuts.  In  one  large 
quarto  vol.  of  550  double-columned  pages.  Strongly  bound  in  extra 
cloth,  $14. 

HOLLAND  (SIR  HENRY).  MEDICAL  NOTES  AND  REFLECTIONS. 
From  the  third  English  edition.  In  one  8vo.  vol.  of  about  500  pages, 
extra  cloth,  $3  50. 

TTODGES  (RICHARD  M.)    PRACTICAL  DISSECTIONS.    Second  edi- 
J-L   tion.     In  one  neat  royal  12mo.  vol.,  half  bound,  $2. 

HUGHES'  SCRIPTURE  GEOGRAPHY  AND  HISTORY,  with  12 
colored  maps.  In  1  vol.  12mo.,  cloth,  $1. 


HENRY  0.  LEA'S  PUBLICATIONS. 


TJORNER  (WILLIAM  E.).   SPECIAL  ANATOMY  AND  HISTOLOGY. 
•"-   Eighth  edition,  revised  and  modified.     In  two  large  8vo.  vols.  of  over 

1000  pages,  containing  300  wood-cuts,  extra  cloth,  $6. 
TTILL  (BERKELEY).     SYPHILIS  AND  LOCAL  CONTAGIOUS  DIS- 
J-«-    ORDERS.  In  one  Svo.  volume  of  467  pages,  extra  cloth,  $3,25.    (Now 

ready.) 

HILLIER  (THOMAS).  HAND  BOOK  OF  SKIN  DISEASES.  In  one 
neat  12ino.  vol.  of  about  300  pages,  with  two  plates,  extra  cloth, 
$2  25. 

HALL  (MRS.  M.)  LIVES  OF  THE  QUEENS  OF  ENGLAND  BEFORE 
THE  NORMAN  CONQUEST.  In  one  handsome  Svo.  vol.,  cloth, 
$2  25  ;  crimson  cloth,  $2  50  j  half  morocco,  $3. 

TONES  (C.  HANDFIELD),  AND  SIEVEKING  (E.  D.  H.)     A  MANUAL 
J      OF  PATHOLOGICAL  ANATOMY.     In  one  large  Svo.  vol.  of  nearly 

750  pages,  with  397  illustrations,  extra  cloth,  $3  50. 
TONES  (C.  HANDFIELD).     CLINICAL  OBSERVATIONS  ON  FUNC- 
U      TIONAL  NERVOUS  DISORDERS.     Second  American  Edition.     In 

one  Svo.  vol.  of  348  pages,  extra  cloth,  $3  25. 

T7-IRKES  (WILLIAM  SENHOUSE).     A  MANUAL  OF  PHYSIOLOGY. 
-••*-    From  the  third  London  edition,  with  200  illustrations.     In  one  large 

12mo.  vol.  of  586  pages,  cloth,  $2  25;  leather,  $2  75. 
T7-NAPP  (F.)     TECHNOLOGY;  OR  CHEMISTRY  APPLIED  TO  THE 
-"•    ARTS  AND  TO  MANUFACTURES,  with  American  additions,  by 
Prof.  Walter  R.  Johnson.     In  two  Svo.  vols.,  with  500  illustrations, 
cloth,  $6. 

T7-ENNEDY'S  MEMOIRS  OF  THE  LIFE  OF  WILLIAM  WIRT.     In 
**-    two  vols.  12mo.,  cloth,  $2. 

T  EA  (HENRY  C.)    SUPERSTITION  AND  FORCE  ;  ESSAYS  ON  THE 
-U     WAGER  OF  LAW,  THE  WAGER  OF  BATTLE,  THE  ORDEAL, 
AND  TORTURE.     In  one  handsome  royal  12mo.  vol.  of  406  pages, 
extra  cloth,  $2  50. 

TALLEMAND    (M.)    AND    WILSON    (MARTUS).      A    PRACTICAL 

J-l     TREATISE  ON  THE  CAUSES,  SYMPTOMS,  AND  TREATMENT 

OF    SPERMATORRHOEA.      Translated   and   edited  by   Henry   J. 

McDougall.     Fifth  American  edition.     To  which  is  added ON 

DISEASES  OF  THE  VESICUL2E  SEMINALES.  With  special  re- 
ference to  the  Morbid  Secretions  of  the  Prostatic  and  Urethral 
Mucous  Membrane.  By  Marris  Wilson,  M.  D.  In  one  neat  octavo 
volume,  of  about  400  pages,  extra  cloth,  $2  75. 

LA  ROCHE  (R.)  YELLOW  FEVER  IN  ITS  HISTORICAL,  PATHO- 
LOGICAL, ETIOLOGICAL,  AND  THERAPEUTICAL  RELA- 
TIONS. In  two  Svo.  vols.  of  nearly  1500  pages,  extra  cloth,  $7. 
PNEUMONIA,  ITS  SUPPOSED  CONNECTION,  PATHOLO- 
GICAL AND  ETIOLOGICAL,  WITH  AUTUMNAL  FEVERS.  In 
one  Svo.  vol.  of  500  pages,  extra  cloth,  $3. 

T  ATJRENCE  (J.  Z.)   AND   MOON   (ROBERT  C.)     A   HANDY  BOOK 
-U    OF  OPHTHALMIC  SURGERY.     With  numerous  illustrations.     In 

one  Svo.  vol.,  extra  cloth,  $2  50.     (Just  issued.) 

T  EHMANN  (C.  G.)     PHYSIOLOGICAL  CHEMISTRY.    Translated  by 

-U     George  F.  Day,  M.  D.,  and  edited  by  R.  E.   Rogers,  M.  D.,  Prof,   of 

Chemistry,  in  the  University  of  Pennsylvania.  With  plates,  and  nearly 

200  illustrations.     In  two  large  Svo.  vols.,  containing  1200  pages, 

extra  cloth,  $6. 

A  MANUAL  OF  CHEMICAL  PHYSIOLOGY.     Translated  with 

notes  and  additions,  by  J.  Cheston  Morris,  M.  D.  With  an  Intro- 
ductory Essay  on  Vital  Force,  by  Prof.  Samuel  Jackson.  In  one 
very  handsome  Svo.  vol.  of  336  pages,  extra  cloth,  $2  25. 


HENRY  C.  LEA'S  PUBLICATIONS. 


T  AWSON  (GEORGE).   INJURIES  OF  THE  EYE,  ORBIT,  AND  EYE- 
J-l     LEDS,  with  about  100  illustrations.     Prom  the  last  English  edition. 

In  one  handsome  8vo.  vol.,  extra  cloth,  $3  50.     (Just  issued.) 
TAYCOCK    (THOMAS).     LECTURES   ON   THE   PRINCIPLES    AND 
J-l    METHODS  OF  MEDICAL  OBSERVATION  AND  RESEARCH.    In 

one  12mo.  vol.,  extra  cloth,  $1. 

T  TJDLOW  (J.  L.)     A  MANUAL  OF  EXAMINATIONS  UPON  ANA- 
•LI     TOMY    PHYSIOLOGY,  SURGERY,  PRACTICE  OF  MEDICINE, 

OBSTETRICS,  MATERIA  MEDICA,  CHEMISTRY,  PHARMACY, 

AND  THERAPEUTICS.     To  which  is  added  a  Medical  Formulary. 

Third  edition.     In  one  royal  12mo.  vol.  of  over  800   pages,    extra 

cloth,  $3  25 ;  leather,  $3  75. 

T  YONS  (EGBERT  D.)     A  TREATISE  ON  FEVER.     In  one  neat  8vo. 
-Li    vol.  of  362  pages,  extra  cloth,  $2  25. 

T  YNCH  (W.  F.)     A  NARRATIVE  OF  THE  UNITED  STATES  EX- 
JJ    PEDITION  TO  THE  DEAD  SEA  AND  RIVER  JORDAN.     In  one 

large  and  handsome  octavo  vol.,  with  28  beautiful  plates  and  two 

maps,  cloth,  $3. 
Same  Work,  condensed  edition.     One  volume  royal  12mo.,  extra 

cloth,  $1. 

MARSHALL  (JOHN).  OUTLINES  OF  PHYSIOLOGY,  HUMAN 
AND  COMPARATIVE.  With  Additions  by  FRANCIS  G.  SMITH, 
M.  D. ,  Professor  of  the  Institutes  of  Medicine  in  the  University  of 
Pennsylvania.  In  one  8vo.  volume  of  1026  pages,  with  122  illustra- 
tions. Strongly  bound  in  leather,  raised  bands,  $7  50  ;  extra  cloth, 
$650.  (Just  issued.) 

MACLISE  (JOSEPH).     SURGICAL   ANATOMY.     In  one  large   im- 
perial quarto  vol.,  with  68  splendid  plates,  beautifully  colored;  con- 
taining 190  figures,  many  of  them  life  size,  extra  cloth,  $14. 
MALGAIGNE'S  OPERATIVE  SURGERY.     With  numerous  illustra- 
tions.    In  one  8vo.  vol.  of  nearly  600  pages,  cloth,  $2  50. 
MANUALS  OF  BLOOD  AND  URINE.     By  Griffith,  Reese,  and  Mar- 
wick.     1  vol.  12mo.  of  460  pages,  extra  cloth,  $1  25. 
MAYNE'S    DISPENSATORY    AND    THERAPEUTICAL    REMEM- 
BRANCER.    Edited  by  R.  E.  Griffith,  M.D.     In  one  12mo.  vol.  of 
about  300  pages,  extra  cloth,  75  cents. 

MACKENZIE  (W.)  A  PRACTICAL  TREATISE  ON  DISEASES  AND 
INJURIES  OF  THE  EYE.  In  one  handsome  8vo.  vol.  of  1027 
pages,  with  plates  and  numerous  wood-cuts,  extra  cloth,  $6  50. 

MEIOS  (CHAS.  D.)  OBSTETRICS,  THE  SCIENCE  AND  THE  ART. 
Fifth  edition,  revised,  with  130  illustrations.  In  one  beautifully 
printed  8vo.  vol.  of  760  pages,  extra  cloth,  $5  50  ;  leather,  $6  50. 

WOMAN  :  HER  DISEASES  AND  THEIR  REMEDIES.     Fourth 

and  improved  edition.     In  one  large  8vo.  vol.  oftover  700  pages, 
extra  cloth,  $5  ;  leather,  $6. 
-ON  THE  NATURE,  SIGNS,  AND  TREATMENT  OF  CHILD-BED 


M 


FEVER      In  one  8vo.  vol.  of  365  pages,  extra  cloth,  $2. 
ILLER  (HENRY).    PRINCIPLES  AND  PRACTICE  OF  OBSTET- 
RICS,  &c.     In   one   very  handsome  8vo.  vol.   of  over  600  pages, 
extra  cloth,  $3  75. 

TV/TILLER  (JAMES) .    PRINCIPLES  OF  SURGERY.    Fourth  American, 
-"-L  from  the  third  Edinburgh  edition.      In  one  large  8vo.  vol.  of  700 

pages,  with  240  illustrations,  extra  cloth,  $3  75. 
THE  PRACTICE  OF  SURGERY.     Fourth  American,  from  the 

last  Edinburgh  edition.     In  one  large  8vo.  vol.  of  700  pages,  with 

364  illustrations,  extra  cloth,  $3  75. 


HKXRY  (.'.  LKA'S  PUBLICATIONS. 


MONTGOMERY  (W.  F.)      AN  EXPOSITION  OF  THE  SIGNS  AND 
SYMPTOMS  OF  PREGNANCY.     From  the  second  English  edition. 
In  one  handsome  8vo.  vol.  of  nearly  600  pages,  extra  cloth,  $3  75. 
TV/TORLAND  (W.  W.)   DISEASES  OF  THE  URINARY  ORGANS.    With 
1YL  illustrations.     In  one  handsome  8vo.  vol.  of  about  600  pages,  extra 
cloth,  $3  50. 

MORLAND  (W.  W.)  ON  THE  RETENTION  IN  THE  BLOOD  OF  THE 
ELEMENTS  OF  THE  URINARY  SECRETION.  In  one  vol.  8vo., 
extra  cloth,  75  cents. 

TV/TILLWRIGHT'S   GTJIDE.      By  Oliver  Evans.      Fourteenth   edition. 
-L»J-  In  one  vol.  8vo.  with  numerous  plates,  extra  cloth,  $2  50. 

MULLER  (J.)  PRINCIPLES  OF  PHYSICS  AND  METEOROLOGY. 
In  one  large  8vo.  vol.  with  550  wood-cuts,  and  two  colored  plates, 
cloth,  $4  50. 

MIRABEAU;  A  LIFE  HISTORY.  In  one  royal  12mo.  vol.,  cloth, 
75  cents. 

•it/rACFARLAND'S  TURKEY  AND  ITS  DESTINY.     In  2  vols.  royal 
1Y1  12mo.,  cloth,  $2. 

MARSH  (MRS.)  A  HISTORY  OF  THE  PROTESTANT  REFORMA- 
TION IN  FRANCE.  In  2  vols.  royal  12mo.,  extra  cloth,  $2. 
NEILL  (JOHN)  AND  SMITH  (FRANCIS  G.)  COMPENDIUM  OF 
THE  VARIOUS  BRANCHES  OF  MEDICAL  SCIENCE.  In  one 
handsome  I2mo.  vol.  of  about  1000  pages,  with  374  wood-cuts, 
extra  cloth,  $4;  leather,  raised  bands,  $4  75. 

NELIGAN  (J.  MOOSE).  A  PRACTICAL  TREATISE  ON  DISEASES 
OF  THE  SKIN.  Fifth  American,  from  the  second  Dublin  edition. 
In  one  neat  royal  12mo.  vol.  of  462  pages,  extra  cloth,  $2  25. 

AN  ATLAS  OF  CUTANEOUS  DISEASES.     In  one  handsome 

quarto  vol.  with  beautifully  colored  plates,  Ac.,  extra  cloth,  $5  50. 

NIEBUHK   (B.   G.)     LECTURES   ON    ANCIENT    HISTORY ;    com- 
prising    the     history    of    the     Asiatic     Nations,    the     Egyptians, 
Greeks,    Macedonians,   and   Carthagenians.     Translated  by  Dr.  L. 
Schmitz.     In  three  neat  volumes,  crown  octavo,  cloth,  $5  00. 
pARRISH  (EDWARD).     A  TREATISE  ON  PHARMACY.    With  many 
•*•      Formula)  and  Prescriptions.      Third  edition.     In  one  handsome  8vo. 
vol.  of  850  pages,  with  several  hundred  illustrations,  extra  cloth,  $5. 
PEASLEE  (E.  R.)     HUMAN  HISTOLOGY  IN  ITS  RELATIONS  TO 
-L      ANATOMY,  PHYSIOLOGY,  AND  PATHOLOGY.     With  434  illus- 
trations.    In  one  8vo.  vol.  of  600  pages,  extra  cloth,  $3  75. 
pIRRIE  (WmiAE")      THE  PRINCIPLES  AND  PRACTICE  OF  SUR- 
•t      GERY.     In  one   handsome  octavo  volume  of  780  pages,  with   316 
illustrations,  extra  cloth,  $3  75. 

PEREIRA  (JONATHAN).     MATERIA  MEDIC  A  AND  THERAPEU- 
TICS.    An  abridged  edition  of  the  late  Dr.  Pereira's  "Elements  of 
Materia  Medica."     With  numerous  additions  and  references  to  the 
United  States  Pharmacopoeia.     In  one  large  octavo  volume,  of  1040 
pages,  with  236  illustrations,  extra  cloth  $7  ;  leather,  raised  bands,  $8. 
pTJLSZKY'S  MEMOIRS  OF  AN  HUNGARIAN  LADY.     In   one  neat 
•L      royal  12mo.  vol.,  extra  cloth,  $1. 

PAGET'S  HUNGARY  AND  TRANSYLVANIA.  In  two  royal  12mo. 
vols.,  cloth,  $2. 

-ROBERTS  (WILLIAM).     A  PRACTICAL  TREATISE  ON  URINARY 
IV)    AND  RENAL  DISEASES.     With  numerous  illustrations.     In  one 

very  handsome  8vo.  vol.  of  516  pages,  extra  cloth,  $4  50. 
"DOYLE  ( J.  FORBES).   MATERIA  MEDICA  AND  THERAPEUTICS. 
JEX)    Edited  by  Jos.  Carson,  M.  D.     In  one  large  8vo.  vol.  of  about  700 
pages,  with  98  illustrations,  extra  cloth,  $3. 


10  HENRY  C.  LEA'S  PUBLICATIONS. 

R^MSBOTHAM  (FRANCIS  H.)  THE  PRINCIPLES  AND  PRAC- 
TICE OF  OBSTETRIC  MEDICINE  AND  SURGERY.  In  one  im- 
perial 8vo.  vol.  of  650  pages,  with  64  plates,  besides  numerous  wood- 
cuts in  the  text.  Strongly  bound  in  leather  $7. 
EIGBY  (EDWARD).  THE  CONSTITUTIONAL  TREATMENT  OF 
FEMALE  DISEASES.  In  one  neat  royal  12mo.  vol.  of  about  250 
pp.,  extra  cloth,  $1. 

A  SYSTEM  OF  MIDWIFERY.     Second  American  edition.    In 

one  handsome  8vo.  vol.  of  422  pages,  extra  cloth,  $2  50. 
POKITANSKY  (CARL).    A  MANUAL  OF  PATHOLOGICAL   ANA- 
-tw    TOMY.     Translated  by  W.  E.    Swaine,   Edward  Sieveking,   C.   H. 
Moore,  and  G.  E.  Day.     Four  vols.  8vo.,  bound  in  two.    About  1200 
pages,  extra  cloth,  $7  50. 

EANKE'S  HISTORY  OF  THE  TURKISH  AND  SPANISH  EMPIRES 
in  the  16th  and  beginning  of  17th  Century.  In  one  8vo.  volume, 
paper,  25  cts. 

HISTORY  OF  THE  REFORMATION  IN  GERMANY.     Parts  I. 

II.  III.     In  one  vol.,  extra  cloth,  $1. 

SARGENT  (F.  W.)  ON  BANDAGING  AND  OTHER  OPERATIONS 
OF  MINOR  SURGERY.  New  edition,  with  an  additional  chapter 
on  Military  Surgery.  In  one  handsome  royal  12mo.  vol.  of  nearly 
400  pages,  with  184  wood -cuts,  extra  cloth,  $1  75. 

SMITH  (LEWIS  J.)  A  TREATISE  ON  THE  DISEASES  OF  IN- 
FANCY AND  CHILDHOOD.  A  New  Work,  now  ready.  In  one 
large  8vo.  volume  of  620  pages,  strongly  bound  in  leather,  $5  75  ; 
extra  cloth,  $4  75. 

QHARPEY    (WILLIAM)    AND    QTJAIN    (JONES   AND    RICHARD) 

&    HUMAN  ANATOMY.     With  notes  and  additions  by  Jos.    Leidy, 

M.D.,  Prof,  of  Anatomy  in  the  University  of  Pennsylvania.     In  two 

large  8vo.  vols.  of  about  1300  pages,  with  51 1  illustrations,  extra  cl.  $6. 

SIMPSON  (SIR  JAMES  Y.)     CLINICAL  LECTURES  ON  THE  DIS- 
EASES OF  WOMEN.     (A  new  edition  preparing.) 
OIMON'S  GENERAL  PATHOLOGY.     In  one  8vo.  vol.  of  212  pages 
^    extra  cloth,  $1  25. 

SKEY  (FREDERIC  C.)     OPERATIVE  SURGERY.     In  one  8vo.  vol. 
of  over  650  pages,  with  about  100  wood-cuts,  cloth,  $3  25. 
SLADE  (D.  D.)     DIPHTHERIA  ;  ITS  NATURE  AND  TREATMENT. 
Second  edition.     In  one  neat  royal  12mo.  vol.,  extra  cloth,  $1  25. 
SMITH  (HENRY  H.)  AND  HORNER  (WILLIAM  E.)     ANATOMICAL 
ATLAS.  Illustrative  of  the  structure  of  the  Human  Body.  In  one  large 
imperial  8vo.  vol.,  with  about  650  beautiful  figures,  extra  cloth,  $4  50. 

SMITH  (EDWARD).     CONSUMPTION ;    ITS  EARLY  AND   REME- 
DIABLE STAGES.     In  one  8vo.  vol.  of  254  pp.,  extra  cloth,  $2  25. 
SOLLY    (SAMUEL).     THE    HUMAN    BRAIN;    ITS    STRUCTURE, 
PHYSIOLOGY,  AND  DISEASES.     In  one  neat  8vo.  vol.  of  500  pp. 
with  120  wood-cuts,  extra  cloth,  $2  50. 

qTILLE  (ALFRED).  THERAPEUTICS  AND  MATERIA  MEDICA. 
^  Third  edition,  revised  and  enlarged.  In  two  large  and  handsome 
J  8vo.  vols.,  extra  cloth,  $10  ;  leather,  $12.  (Just  ^ss^ted.) 
QALTER  (H.  H.)  ASTHMA  ;  ITS  PATHOLOGY,  CAUSES,  CONSE- 
W  QUENCES,  AND  TREATMENT.  In  one  volume  8vo.,  extra  cloth, 
$250. 

aCHOEDLER  (FREDERICK)  AND  MEDLOCK  (HENRY).   WONDERS 

*J     OF  NATURE.   An  elementary  introduction  to  the  Sciences  of  Physics, 

Astronomy,     Chemistry,     Mineralogy,    Geology,    Botany,     Zoology, 

and  Physiology.     Translated  from  the  German  by  H.  Medlock.     In 

one  neat  8vo.  vol.,  with  679  illustrations,  extra  cloth,  f  3. 


HENRY  C.  LEA'S  PUBLICATIONS.  11 


SMALL  BOOKS  ON  GREAT  SUBJECTS.  Twelve  works  ;  each  one  15 
cents,  sewed,  forming  a  neat  and  cheap  series  ;  or  done  up  in  3  vols., 
extra  cloth,  $1  50. 

QTRICKLAND    (AGNES).      LIVES  OF  THE  QUEENS   OF.  HENRY 
fc     THE  VIII.  AND  OF  HIS   MOTHER.     In  one  crown  octavo  vol., 

extra  cloth,  $1  ;  black  cloth,  90  cents. 
MEMOIRS  OF  ELIZABETH,  SECOND  QUEEN  REGNANT  OF 

ENGLAND  AND  IRELAND.     In  one  crown  octavo  vol.,  extra  cloth, 

$140;  black  cloth,  $1  30. 

SCHMITZ  AND  ZTJMPT'S  CLASSICAL  SERIES.     In  royal  18mo. 
CORNELII  NEPOTIS  LIBER  DE  EXCELLENTIBUS  DUCIBUS 

EXTERARUM  GENTIUM,  CUM  VITIS  CATONIS  ET  ATTICI. 

With  notes,  &c.     Price  in  extra  cloth,  60  cents  j  half  bound,  70  cts. 
C.  I.  C^ESARIS  COMMENTARII  DE  BELLO  GALLICO.  With  notes, 

map,  and  other  illustrations.     Price  in  extra  cloth,  60  cents;   half 

bound,  70  cents. 
C.  C.  SALLUSTII  DE  BELLO  CATILINARIO  ET  JUGURTHINO. 

With  notes,  map,  &c.     Price  in  extra  cloth,  60  cents ;  half  bound, 

70  cents. 
Q.  CURTII  RUFII  DE  GESTIS  ALEXANDRI  MAGNI  LIBRI  VIII. 

With  notes,  map,  <fec.     Price  in  extra  cloth,  80  cents  ;  half  bound, 

90  cents. 
P.  VIRGILII  MARONIS  CARMINA  OMNIA.     Price  in  extra  cloth, 

85  cents;  half  bound,  $1. 
M.  T.  CICERONIS  ORATIONES  SELECTS  XII.     With  notes,  Ac. 

Price  in  extra  cloth,  70  cents  ;  half  bound,  80  cents. 
ECLOGUE  EX  Q.  HORATII  FLACCI  POEMATIBUS.     With  notes, 

&c.     Price  in  extra  cloth,  70  cents  ;  half  bound,  80  cents. 
ADVANCED    LATIN    EXERCISES,     WITH    SELECTIONS    FOR 

READING.     Revised,  with  additions.     Extra  cloth,  price  60  cents  ; 

half  bound,  70  cents. 

rpANNER  (THOMAS  HAWKES).    A  MANUAL  OF  CLINICAL  MEDI- 
J-     CINE  AND   PHYSICAL   DIAGNOSIS.     Third  American  from  the 
second  revised  English  edition.     In  one  handsome  12mo.  vol.      (Pre- 
paring for  early  publication.) 

ON  THE  SIGNS  AND  DISEASES  OF  PREGNANCY.     First 

American  from  the  second  English  edition.  With  four  colored  plates 
and  numerous  illustrations  on  wood.  In  one  vol.  8vo.  of  about  500 
pages,  extra  cloth,  $4  25.  (Just  issued.) 

HP  A  YLOR  (ALFRED  S.)    MEDICAL  JURISPRUDENCE.    Sixth  Ameri- 

J-     can  from  the  eighth  London  edition.     With  notes  and  references  to 

American  Decisions,  by  C.  B.  Penrose  of  the  Philadelphia  Bar.     In 

one  large  8vo.  vol.  of  776  pages,  extra  cloth,  $4  50  ;  leather,  $5  50. 

rpHOMAS  (T.  GAILLARD).     A  COMPLETE  PRACTICAL  TREATISE 

-L     ON  THE  DISEASES  OF  FEMALES.     Second  and  revised  edition. 

In  one  large  and  handsome  octavo  volume  of  about  650  pages,  with 

illustrations,  extra  cloth,  $5  ;  leather,  $6.     (Now  ready.) 

rpDDD  (ROBERT  B.)  AND  BOWMAN  (W.)     PHYSIOLOGICAL  ANA- 

J-     TOMY  AND  PHYSIOLOGY  OF  MAN.     In  one  large  8vo.  vol.  of 

about  950  pages,  with  300  illustrations  on  wood,  extra  cloth,  $4  75. 

TODD  (ROBERT  BENTLEY).  CLINICAL  LECTURES  ON  CERTAIN 
ACUTE  DISEASES.  In  one  vol.  8vo.  of  320  pp.,  extra  cloth,  $2  50. 

rpOYNBEE  (JOSEPH).    THE  DISEASES  OF  THE  EAR  :  Their  nature, 

•*•     Diagnosis,    and    Treatment.       Second    American    edition.       In   one 

handsome  8vo.  vol.  of  440  pp.,  with  100  illustrations,  extra  cloth,  $4. 


12  HENRY  C.  LEA'S  PUBLICATIONS. 

mHOMPSON  (SIR  HENRY).    CLINICAL  LECTURES  ON  DISEASES 
1     OF  THE  URINARY  ORGANS.     In  one  8vo.  volume  of  204  pages, 
with  illustrations,  extra  cloth,  $2  25.     (Now  ready.) 

WALES  (PHILIP  S.)  MECHANICAL  THERAPEUTICS  :  A  Prac- 
tical Treatise  on  Surgical  Apparatus,  Appliances,  and  Elementary 
Operations  ;  embracing  Minor  Surgery,  Bandaging,  Orthopraxy,  and 
Treatment  of  Fractures  and  Dislocations.  In  one  large  8vo.  vol.  of 
about  700  pnges,  with  642  illustrations  on  wood,  extra  cloth,  $5  75  ; 
leather,  $6  75.  (Jiist  issued.) 

WELLS  (J.  SOELBEEG).  A  TREATISE  ON  THE  DISEASES  OF 
THE  EYE.  Edited  with  additions.  In  one  large  and  handsome 
octavo  volume,  with  6  colored  plates  and  several  hundred  wood-cuts. 
(In  press.) 

WALSHE  (W.  H.)  PRACTICAL  TREATISE  ON  THE  DISEASES 
OF  THE  HEART  AND  GREAT  VESSELS.  Third  American  from 
the  third  revised  London  edition.  In  one  8vo.  vol.  of  420  pages, 
extra  cloth,  $3. 

WHAT  TO   OBSERVE  AT  THE   BEDSIDE  AND  AFTER  DEATH 
W  IN  MEDICAL  CASES.    In  one  royal  12mo.  vol.,  extra  cloth,  $1. 

WATSON  (THOMAS).  LECTURES  ON  THE  PRINCIPLES  AND 
PRACTICE  OF  PHYSIC.  A  new  American  from  the  last  revised 
English  edition,  with  additions  by  D.  Francis  Condie.  With  185 
illustrations  on  wood.  In  one  very  large  volume  imperial  8vo.  of 
over  1200  pages,  in  small  type,  extra  cloth,  $6  50  ;  strongly  bound 
in  leather,  raised  bands,  $7  50. 

WEST  (CHARLES).  LECTURES  ON  THE  DISEASES  PECULIAR 
TO  WOMEN.  Third  American  from  the  Third  English  edition.  In 
one  octavo  volume  of  550  pages,  extra  cloth,  $3  75  ;  leather,  $4  75. 
(Now  ready.) 

LECTURES  ON  THE  DISEASES  OF  INFANCY  AND  CHILD- 

HOOD.  Fourth  American  from  the  fifth  revised  English  edition.  In 
one  large  8vo.  vol.  of  656  closely  printed  pages,  extra  cloth,  $4  50  ; 
leather,  $5  50. 

AN  ENQUIRY  INTO  THE  PATHOLOGICAL  IMPORTANCE 

OF  ULCERATION  OF  THE  OS  UTERI.     In  one  vol.  8vo.,  extra 
cloth,  $1  25. 

WILLIAMS  (CHARLES  J.  B.)  PRINCIPLES  OF  MEDICINE.  A 
new  American  from  the  third  revised  London  edition.  In  one  8vo. 
vol.  of  about  500  pages,  extra  cloth,  $3  50. 

YfiTILSON   (ERASMUS).     A  SYSTEM  OF  HUMAN  ANATOMY.     A 
"  »    new  and  revised  American  from  the  last  English  edition.    Illustrated 
with  397  engravings  on  wood.     In  one  handsome  8vo.  vol.  of  over 
600  pages,  extra  cloth,  $4  ;  leather,  $5. 

THE  DISSECTOR'S  MANUAL.     Third  American  from  the  last 

revised  London  edition.     In  one  large  12mo.  vol.  of  582  pages,  with 
354  illustrations,  extra  cloth,  $2. 

ON  DISEASES  OF   THE  SKIN.     The  seventh  American  from 

the  last  English  edition.     In  one  large  8vo.  vol.  of  over  800  pagea, 
extra  cloth,  $5.      (Just  ready.) 

Also  A  SERIES  OF  PLATES,  illustrating  "  Wilson  on  Diseases  of  the 
Skin,"  consisting  of  20  plates,  thirteen  of  which  are  beautifully 
colored,  representing  about  one  hundred  varieties  of  Disease.  $5  50. 

Also,  the  TEXT  AND  PLATES,  bound  in  one  volume,  extra  cloth,  $10. 

THE  STUDENT'S  BOOK   OF  CUTANEOUS   MEDICINE.     In 

one  handsome  royal  12mo.  vol..  extra  cloth,  $3  50. 

WINSLOW  (FORBES).  ON  OBSCURE  DISEASES  OF  THE  BRAIN 
AND  DISORDERS  OF  THE  MIND.  In  one  handsome  8vo.  rol. 
of  nearly  600  pages,  extra  cloth,  $4  25. 


L 


4l879 


